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AIR - 2.0 FLIGHT OPERATIONS

 

2.1 General

This section provides airmanship information on various flight operations subjects.

2.2 Crosswind Landing Limitations

Approximately 10% of all aircraft accidents involving light aircraft in Canada are attributed to pilot failure to compensate for crosswind conditions on landing.

Light aircraft manufactured in the United States are designed to withstand, on landing, 90° crosswinds up to a velocity equal to 0.2 (20%) of their stalling speed.

This information in conjunction with the known stalling speed of a particular aircraft makes it possible to use the following crosswind component graph to derive a “general rule” for most light aircraft manufactured in the United States. The aircraft owner’s manual may give higher or limiting crosswinds. Examples follow.

Wind Degrees off Runway

Example 1: Aircraft with a stalling speed of 60 MPH:

WIND-DEGREE PERMISSIBLE WIND SPEEDS
90° (0.2 x 60 MPH stalling speed) 12 MPH
60° using crosswind component graph 14 MPH
30° using crosswind component graph 24 MPH
15° using crosswind component graph 48 MPH

Example 2: Aircraft with a stalling speed of 50 KT:

WIND-DEGREE PERMISSIBLE WIND SPEEDS
90° (0.2 x 50 KT stalling speed) 10 KT
60° using crosswind component graph 12 KT
30° using crosswind component graph 20 KT
15° using crosswind component graph 40 KT
 

2.3 Carburetor Icing

Carburetor icing is a common cause of general aviation accidents. Fuel injected engines have very few induction system icing accidents, but otherwise no airplane and engine combination stands out. Most carburetor icing related engine failure happens during normal cruise. Possibly, this is a result of decreased pilot awareness that carburetor icing will occur at high power settings as well as during descents with
reduced power.

In most accidents involving carburetor icing, the pilot has not fully understood the carburetor heat system of the aircraft and what occurs when it is selected. Moreover, it is difficult to understand the countermeasures unless the process of ice formation in the carburetor is understood. Detailed descriptions of this process are available in most good aviation reference publications and any AME employed on type can readily explain the carburetor heat system. The latter is especially important because of differences in systems. The pilot must learn to accept a rough-running engine for a minute or so as the heat melts and loosens the ice which is then ingested into the engine.

The following chart provides the range of temperature and relative humidity which could induce carburetor icing.

Carburetor Icing

NOTE: This chart is not valid when operating on MOGAS. Due to its higher volatility, MOGAS is more susceptible to the formation of carburetor icing. In severe cases, ice may form at OATs up to 20°C higher than with AVGAS.

2.4 Low Flying

Before conducting any low flying, the pilot should be clear about the purpose and legality of the exercise. Accordingly, all preparations in terms of assessment of the terrain to be overflown, weather, aircraft performance, and selection of appropriate charts are important to the successful completion of the flight.

All known objects 300 feet or more AGL (or lower ones if deemed hazardous) are depicted on visual navigational charts. However, because there is only limited knowledge over the erection of man-made objects, there can be no guarantee that all such structures are known, and accordingly, an additional risk is added to the already hazardous practice of low flying.

Further, even though structures assessed as potential hazards to air navigation are required to be marked, including special high intensity strobe lighting for all structures 500 ft AGL and higher, the majority of aircraft collisions with man-made structures occur at levels below 300 ft AGL (See Obstruction Markings – AGA 6.0).

Another concern to low flying is the blasting operations associated with the logging industry. The trajectory of debris from the blasting varies with the type of explosives, substance being excavated and the canopy of trees, if any. These blasting activities may or may not be advertised by NOTAM.

2.4.1 Flying Near Power Lines

Main power lines are easy to see, but when flying in their vicinity you must take the time to look for what is really there and then use safe procedures. Remember, the human eye is limited, so if the background landscape does not provide sufficient contrast you will not see a wire or cable. Although hydro structures are big and generally quite visible, a hidden danger exists in the wires around them.

Flying Near Power Llines

The figure shown above emphasizes this point. The main conductor cluster is made up of several heavy wires. These heavy, sagging conductors are about two inches in diameter and very visible, so they tend to distract one from seeing the guard or lightning protection wires, which are of much smaller diameter.

Guard wires do not sag the way the main conductors do and are difficult to pick out even in good visibility. The only way to be safe is to avoid the span portion of the line and always cross at a tower, maintaining a safe altitude, with as much clearance as possible.

  • When following power lines, remain on the right-hand side relative to your direction of flight and watch for cross lines and guy cables.
  • Expect radio and electrical interference in the vicinity of power lines.
  • For operational low flying, do an overflight and map
    check first.
  • Leave yourself an “out”-cross at 45 degrees to the line.
  • Reduce speed in low visibility (for VFR-one mile visibility; clear of cloud; 165 kt max.).

Warning—Intentional low flying is hazardous. Transport Canada advises all pilots that low flying for weather avoidance or operational requirements is a high-risk activity.

2.4.2 Logging Operations

Extensive use is made in logging operations of equipment potentially hazardous to aircraft operations. These include highlead spars, grapple yarders and skyline cranes.

When highlead spars or grapple yarders are used, hauling and guyline cables radiate from the top of the spar or boom. Cables may cross small valleys or be anchored on side hills behind the spar. While spars generally do not exceed 130 ft AGL and are conspicuously painted, the cable system may be difficult to see. This type of equipment operates from a series of logging roads.

Figure 2.1 – Highlead Spar

Highlead Spar

By contrast, skyline cranes consist of a single skyline cable anchored at the top and bottom of a long slope and supported by one or several intermediate poles. This cable generally follows the slope contour about 100 ft AGL, but may also cross draws and gullies and may be at heights in excess of 100 ft AGL. Skyline cables are virtually invisible from the air. Their presence is indicated by active or recently completed logging and the absence of a defined series of logging roads, although a few roads may be present.

Figure 2.2 – Skyline Crane

Skyline Crane

Pilots operating in areas where logging is prevalent must be aware when operating below 300 ft AGL that these types of equipment exist and do not always carry standard obstruction and paint markings.

 

2.5 Flight Operations in Rain

An error in vision can occur when flying in rain. The presence of rain on the windscreen, in addition to causing poor visibility, introduces a refraction error. This error is because of two things: firstly, the reduced transparency of the rain-covered windscreen causes the eye to see a horizon below the true one (because of the eye response to the relative brightness of the upper bright part and the lower dark part); and secondly, the shape and pattern of the ripples formed on the windscreen, particularly on sloping ones, which cause objects to appear lower. The error may be present as a result of one or other of the two causes, or of both, in which case it is cumulative and is of the order of about 5° in angle. Therefore, a hilltop or peak 1/2 NM ahead of an aircraft could appear to be approximately 260 ft lower, (230 ft lower at 1/2 SM) than it actually is.

Pilots should remember this additional hazard when flying in conditions of low visibility in rain and should maintain sufficient altitude and take other precautions, as necessary, to allow for the presence of this error. Also, pilots should ensure proper terrain clearance during enroute flight and on final approach to landing.

2.6 Flight Operations In Volcanic Ash

Flight operations in volcanic ash are hazardous. Experience has shown that damage can occur to aircraft surfaces, windshields and powerplants. Aircraft heat and vent systems, as well as hydraulic and electronic systems, can also be contaminated. Powerplant failures are a common result of flight in volcanic ash, with turbine engines being particularly susceptible. Simultaneous power loss in all engines has occurred. In addition, volcanic ash is normally very heavy; accumulations of it within the wings and tail section have been encountered, with adverse effects on aircraft weight and balance.

Aviation radar is not effective in detecting volcanic ash clouds. There is no reliable information regarding volcanic ash concentrations which might be minimally acceptable for flight. Recent data suggests that “old” volcanic ash still represents a considerable hazard to safety of flight. Pilots are cautioned that ash from volcanic eruptions can rapidly reach heights in excess of FL600 and be blown downwind of the source for considerable distances. Encounters affecting aircraft performance have occurred 2 400 NM from the ash source and up to 72 hours after an eruption.

Therefore: if an ash cloud is visible to a pilot, entry into the cloud must be avoided.

The risk of entering ash in IMC or night conditions is particularly dangerous, owing to the absence of a clear visual warning.

Therefore: if PIREPs, SIGMETs (see MET 3.18), NOTAM (see MAP 5.0), and analysis of satellite imagery and/or ash cloud trajectory forecasts indicate that ash might be present within a given airspace, that airspace must be avoided until it can be determined to be safe for entry.

St. Elmo’s fire is usually a telltale sign of a night encounter, although rapid onset of engine problems may be the first indication. Pilots should exit the cloud expeditiously while following any engine handling instructions provided in the aircraft flight manuals for such circumstances.

Pilots should be aware that they may be the first line of volcanic eruptions detection in more remote areas. In the initial phase of any eruption there may be little or no information available to advise pilots of the new ash hazard. If an eruption or ash cloud is observed, an urgent PIREP (see MET 2.5 and 3.17) should be filed with the nearest ATS unit.

 

2.7 Flight Operation Near Thunderstorms

2.7.1 General

Thunderstorms are capable of containing nearly all weather hazards known to aviation. These include tornadoes, turbulence, squall line, microburst, heavy updrafts and downdrafts, icing, hail, lightning, precipitation static, heavy precipitation, low ceiling and visibility.

There is no useful correlation between the external visual appearance of a thunderstorm and the severity or amount of turbulence or hail within it. The visible thunderstorm cloud is only a portion of a turbulent system of updrafts and downdrafts that often extend far beyond. Severe turbulence may extend up to 20 NM from severe thunderstorms.

Airborne or ground based weather radar will normally reflect areas of precipitation. The frequency and severity of turbulence associated with the areas of high water content generally increases the radar return. No flight path, through an area of strong or very strong radar echoes separated by 40 NM or less, can be considered free of severe turbulence.

Turbulence beneath a thunderstorm should not be underestimated. This is especially true when the relative humidity is low. There may be nothing to see until you enter strong out-flowing winds and severe turbulence.

The probability of lightning strikes occurring to aircraft is greatest when operating at altitudes where temperatures are between -5°C and 5°C. Lightning can strike aircraft flying in clear air in the vicinity of a thunderstorm. Lightning can puncture the skin of an aircraft, damage electronic equipment, cause engine failure and induce permanent error in
magnetic compasses.

Engine Water Ingestion

If the updraft velocity in the thunderstorm approaches or exceeds the terminal falling velocity of the falling raindrops, very high concentrations of water may occur. It is possible that these concentrations may exceed the quantity of water that a turbine engine is capable of ingesting. Therefore, severe thunderstorms may contain areas of high water concentration which could result in a flameout or structural failure of one or more engines. Note that lightning can also cause compressor stalls or flameouts.

PIREP

Remember, a timely PIREP will allow you and others to make the right decision earlier.

2.7.2 Considerations

(a) Above all, never think of a thunderstorm as “light” even though the radar shows echoes of light intensity. Avoiding thunderstorms is the best policy. Remember that vivid and frequent lightning indicates a severe activity in the thunderstorm and that any thunderstorm with tops 35 000 ft or higher is severe. Whenever possible:

(i) don’t land or take off when a thunderstorm is approaching. The sudden wind shift of the gust front or low level turbulence could result in loss of control;

(ii) don’t attempt to fly under a thunderstorm even when you can see through to the other side. Turbulence under the storm could be disastrous;

(iii) avoid any area where thunderstorms are covering 5/8 or more of that area;

(iv) don’t fly into a cloud mass containing embedded thunderstorms without airborne radar;

(v) avoid by at least 20 NM any thunderstorm identified as severe or giving intense radar returns. This includes the anvil of a large cumulonimbus; and

(vi) clear the top of a known or suspected severe thunderstorm by at least 1 000 ft altitude for each 10 KT of wind speed at the cloud top.

(b) If you cannot avoid an area of thunderstorms, consider these points:

(i) Tighten your seat belt and shoulder harness; secure all loose objects.

(ii) Plan a course that will take you through the storm area in a minimum time and hold it.

(iii) Avoid the most critical icing areas, by penetrating at an altitude below the freezing level or above the level of -15°C.

(iv) Check that pitot, carburetor or jet inlet heat are on. Icing can be rapid and may result in almost instantaneous power failure or airspeed indication loss.

(v) Set the power settings for turbulence penetration airspeed recommended in your aircraft manual.

(vi) Turn up cockpit lights to its highest intensity to minimize temporary blindness from lightning.

(vii) When using the auto-pilot, disengage the altitude hold mode and the speed hold mode. The automatic altitude and speed controls will increase manoeuvres of the aircraft, thus increasing structural stresses.

(viii) Tilt the airborne radar antenna up and down occasionally. This may detect hail or a growing thunderstorm cell.

(c) If you enter a thunderstorm:

(i) Concentrate on your instruments; looking outside increases the danger of temporary blindness from lightning.

(ii) Don’t change power settings; maintain the settings for turbulence penetration airspeed.

(iii) Don’t attempt to keep a constant rigid altitude; let the aircraft “ride the waves”. Manoeuvres in trying to maintain constant altitude increases stress on the aircraft. If altitude cannot be maintained, inform ATC as soon as possible.

(iv) Don’t turn back once you have entered a thunderstorm. Maintaining heading through the storm will get you out of the storm faster than a turn. In addition, turning manoeuvres increases stress on the aircraft

 

2.8 Low Level Wind Shear

Relatively recent meteorological studies have confirmed the existence of the “burst” phenomena. These are small-scale, intense downdrafts which, on reaching the surface, spread outward from the downflow centre. This causes the presence of both vertical and horizontal wind shear that can be extremely hazardous to all types and categories of aircraft.

Low Level Wind Shear

Wind shear may create a severe hazard for aircraft within 1 000 ft AGL, particularly during the approach to landing and in the takeoff phases. On takeoff, this aircraft may encounter a headwind (performance increasing) (1) followed by a downdraft (2), and tailwind (3) (both performance decreasing).

Pilots should heed wind shear PIREP as a previous pilot’s encounter with a wind shear may be the only warning. Alternate actions should be considered when a wind shear has been reported.

Characteristics of microbursts include:

  1. Size - Approximately 1 NM in diameter at 2 000 ft AGL with a horizontal extent at the surface of approximately 2 to 2 1/2 NM.
  2. Intensity - Vertical winds as high as 6 000 ft per minute. Horizontal winds giving as much as 45 KT at the surface (i.e., 90 KT shear).
  3. Types - Microbrusts are normally accompanied by heavy rain in areas where the air is very humid. However, in drier areas, falling raindrops may have sufficient time and distance to evaporate before reaching the ground. This is known as VIRGA.
  4. Duration - The life-cycle of a microburst from the initial downburst to dissipation will seldom be longer than 15 minutes with maximum intensity winds lasting approximately 2 - 4 minutes. Sometimes microbursts are concentrated into a line structure and under these conditions, activity may continue for as long as an hour. Once microburst activity starts, multiple microbursts in the same general area are common and should be expected.

The best defence against wind shear is to avoid it altogether because it could be beyond your or your aircraft’s capabilities. However, should you recognize a wind shear encounter, prompt action is required. In all aircraft, the recovery could require full power and a pitch attitude consistent with the maximum angle of attack for your aircraft. For more information on wind shear, consult the Air Command Weather Manual (TP 9352E).

Remember, should you experience a wind shear, warn others, as soon as possible, by sending a PIREP to the ground facility.

 

2.9 Wake Turbulence

Wake turbulence is caused by wing-tip vortices and is a by-product of lift. The higher air pressure under the wings tries to move to the lower air pressure on top of the wings by  flowing towards the wing tips, where it rotates and flows into the lower pressure on top of the wings. This results in a twisting rotary motion that is very pronounced at the wing tips and continues to spill over the top in a downward spiral. Therefore, the wake consists of two counter-rotating cylindrical vortices.

Wake Turbulence

Vortex Strength

The strength of these vortices is governed by the shape of the wings, and the weight and speed of the aircraft; the most significant factor is weight. The greatest vortex strength occurs under conditions of heavy weight, clean configuration, and slow speed. The strength of the vortex shows little dissipation at altitude within 2 min of the time of initial formation. Beyond 2 min, varying degrees of dissipation occur along the vortex path; first in one vortex and then in the other. The break-up of vortices is affected by atmospheric turbulence; the greater the turbulence, the more rapid the dissipation of the vortices.

Induced Roll

Aircraft flying directly into the core of a vortex will tend to roll with the vortex. The capability of counteracting the roll depends on the wing span and control responsiveness of the aircraft. When the wing span and ailerons of a larger aircraft extend beyond the vortex, counter-roll control is usually effective, and the effect of the induced roll can be minimized. Pilots of short wing span aircraft must be especially alert to vortex situations, even though their aircraft are of the high-performance type.

Helicopter Vortices

In the case of a helicopter, similar vortices are created by the rotor blades. However, the problems created are potentially greater than those caused by a fixed-wing aircraft  because the helicopter’s lower operating speeds produce more concentrated wakes than fixed-wing aircraft. Departing or landing helicopters produce a pair of high-velocity trailing vortices similar to wing-tip vortices of large fixed-wing aircraft; the heavier the helicopter, the more intense the wake turbulence. Pilots of small aircraft should use caution when operating or crossing behind landing or departing helicopters.

Vortex Avoidance

Avoid the area below and behind other aircraft, especially at low altitude, where even a momentary wake turbulence encounter could be disastrous.

2.9.1 Vortex Characteristics

General

Trailing vortices have characteristics which, when known, will help a pilot visualize the wake location and thereby take avoidance precautions. Vortex generation starts with rotation (lifting off of the nosewheel) and will be severe in that airspace immediately following the point of rotation. Vortex generation ends when the nosewheel of a landing aircraft touches down.

Because of ground effect and wind, a vortex produced within about 200 feet AGL tends to be subject to lateral drift movements and may return to where it started. Below 100 feet AGL, the vortices tend to separate laterally and break up more rapidly than vortex systems at higher altitude. The vortex sink rate and levelling off process result in little operational effect between an aircraft in level flight and other aircraft separated by 1 000 feet vertically. Pilots should fly at or above a heavy jet’s flight path, altering course as necessary to avoid the area behind and below the generating aircraft. Vortices start to descend immediately after formation and descend at the rate of 400 to 500 feet per minute for large heavy aircraft and at a lesser rate for smaller aircraft, but in all cases, descending less than 1 000 feet in total in 2 minutes.

Vortices spread out at a speed of about 5 KT. Therefore, a crosswind will decrease the lateral movement of the upwind vortex and increase the movement of the downwind vortex. Thus, a light wind of 3 to 7 KT could result in the upwind vortex remaining in the touchdown zone for a period of time or hasten the drift of the downwind vortex toward another runway. Similarly, a tail wind condition can move the vortices of the preceding landing aircraft forward into the touchdown zone.

Since vortex cores can produce a roll rate of 80° per second or twice the capabilities of some light aircraft and a downdraft of 1 500 feet per minute which exceeds the rate of climb of many aircraft, the following precautions are recommended.

Pilots should be particularly alert in calm or light wind conditions where the vortices could:

(a) remain in the touchdown area;

(b) drift from aircraft operating on a nearby runway;

(c) sink into takeoff or landing path from a crossing runway;

(d) sink into the traffic pattern from other runway operations;

(e) sink into the flight path of VFR flights at 500 feet AGL and below.

2.9.2 Considerations

On the ground

(1) Before requesting clearance to cross a live runway, wait a few minutes when a large aircraft has just taken off or landed.

(2) When holding near a runway, expect wake turbulence.

Takeoff

(1) When cleared to takeoff following the departure of a large aircraft, plan to become airborne prior to the point of rotation of the preceding aircraft and stay above the departure path or request a turn to avoid the departure path.

(2) When cleared to takeoff following the landing of a large aircraft, plan to become airborne after the point of touchdown of the landing aircraft

Enroute VFR

(1) Avoid flight below and behind a large aircraft. If a large aircraft is observed along the same track (meeting or overtaking), adjust position laterally preferably upwind.

Landing

(1) When cleared to land behind a departing aircraft, plan to touchdown prior to reaching the rotation point of the departing aircraft.

(2) When behind a large aircraft landing on the same runway, stay at or above the preceding aircraft’s final approach flight path, note the touchdown point and land beyond this point if it is safe to do so.

(3) When cleared to land behind a large aircraft on a low approach or on a missed approach on the same runway, beware of vortices that could exist between the other aircraft’s flight path and the runway surface.

(4) When landing after a large aircraft on a parallel runway closer than 2 500 feet, beware of possible drifting of the vortex on to your runway. Stay at or above the large aircraft’s final approach flight path, note his touchdown point and land beyond if it is safe to do so.

(5) When landing after a large aircraft has departed from a crossing runway, note the rotation point. If it is past the intersection, continue the approach and land before the intersection. If the large aircraft rotates prior to the intersection, avoid flight below the large aircraft’s flight path. Abandon the approach unless a landing is assured well before reaching the intersection.

ATC will use the words “CAUTION – WAKE TURBULENCE” to alert pilots to the possibility of wake turbulence. It is the pilots’ responsibility to adjust their operations and flight path to avoid wake turbulence.

Air traffic controllers apply separation minima between aircraft. See RAC 4.1.1 for these procedures which are intended to minimize the hazards of wake turbulence.

An aircraft conducting an IFR final approach should remain on glide path as the normally supplied separation should provide an adequate wake turbulence buffer. However, arriving VFR aircraft, while aiming to land beyond the touchdown point of a preceding heavy aircraft, should be careful to remain above its flight path. If extending flight path, so as to increase the distance behind an arriving aircraft, one should avoid the tendency to develop a dragged-in final approach. Pilots should remember to apply whatever power is required to maintain altitude until reaching a normal descent path. The largest number of dangerous encounters have been reported in the last half mile of the final approach.

Be alert to adjacent large aircraft operations particularly upwind of your runway. If an intersection takeoff clearance is received, or parallel and cross runway operations are in progress, avoid subsequent heading which will result in your aircraft crossing below and behind a large aircraft.

NOTES 1: If any of the procedures are not possible and you are on the ground, WAIT! (2 minutes are usually sufficient). If on an approach, consider going around for another approach.

2: See AIR 1.7 for Jet and Propeller Blast Danger.

 

2.10 Clear Air Turbulence

These rules of thumb are given to assist pilots in avoiding clear air turbulence (CAT). They apply to westerly jet streams. The Air Command Weather Manual (TP 9352E) available from Transport Canada discusses this subject more thoroughly.

  1. Jet streams stronger than 110 KT (at the core) have areas of significant turbulence near them in the sloping tropopause above the core, in the jet stream front below the core and on the low-pressure side of the core.
  2. Wind shear and its accompanying CAT in jet streams is more intense above and to the lee of mountain ranges. For this reason, CAT should be anticipated whenever the flight path crosses a strong jet stream in the vicinity of a mountain range.
  3. On charts for standard isobaric surfaces such as the 250 mbs charts, 30 KT isotachs spaced closer than 90 NM indicate sufficient horizontal shear for CAT. This area is normally on the north (low-pressure) side of the jet stream axis, but in unusual cases may occur on the south side.
  4. CAT is also related to vertical shear. From the wind-aloft charts or reports, compute the vertical shear in knots-per-thousand feet. Turbulence is likely when the shear is greater than 5 KT per thousand feet. Since vertical shear is related to horizontal temperature gradient, the spacing of isotherms on an upper air chart is significant. If the 5°C isotherms are closer together than 2° of latitude (120 NM), there is usually sufficient vertical shear for turbulence.
  5. Curving jet streams are more apt to have turbulent edges than straight ones, especially jet streams which curve around a deep pressure trough.
  6. Wind-shift areas associated with troughs are frequently turbulent. The sharpness of the wind-shift is the important factor. Also, ridge lines may also have rough air.
  7. In an area where significant CAT has been reported or is forecast, it is suggested that the pilot adjust the airspeed to the recommended turbulent air penetration speed for the aircraft upon encountering the first ripple, since the intensity of such turbulence may build up rapidly. In areas where moderate or severe CAT is expected, it is desirable to adjust the airspeed prior to encountering turbulence.


    Clear Air Turbulence
  8. If jet stream turbulence is encountered with direct tailwinds or headwinds, a change of flight level or course should be initiated since these turbulent areas are elongated with the wind but are shallow and narrow. A turn to the south in the Northern Hemisphere will place the aircraft in a more favourable area. If a turn is not feasible because of airway restrictions, a climb or descent to the next flight level will usually result in smoother air.
  9. When jet stream turbulence is encountered in a crosswind situation, pilots wanting to cross the CAT area more quickly should, either climb or descend based on temperature change. If temperature is rising – climb; if temperature is falling - descend. This will prevent following the sloping tropopause or frontal surface and staying in the turbulent area. If the temperature remains constant, either climb or descend.
  10. If turbulence is encountered with an abrupt wind-shift associated with a sharp pressure trough, a course should be established to cross the trough rather than to fly parallel to it. A change in flight level is not as likely to reduce turbulence.
  11. If turbulence is expected because of penetration of a sloping tropopause, pilots should refer to the temperature. The tropopause is where the temperature stops decreasing. Turbulence will be most pronounced in the temperature-change zone on the stratospheric side of the sloping tropopause.
  12. Both vertical and horizontal wind shear are greatly intensified in mountain wave conditions. Therefore, when the flight path crosses a mountain wave, it is desirable to fly at turbulence-penetration speed and avoid flight over areas where the terrain drops abruptly. There may be no lenticular clouds associated with the mountain wave.

PIREP

Clear air turbulence can be a very serious operational factor to flight operations at all levels and especially to jet traffic flying above 15 000 feet. The best available information comes from pilots via a PIREP. Any pilot encountering CAT is urgently requested to report the time, location and intensity (light, moderate or severe as per MET 3.7) to the facility with which they are maintaining radio contact. (See MET 1.1.6.)

 

2.11 Flight Operations on Water

2.11.1 General

Pilots are reminded that when aircraft are being operated on the waters of harbours, ports, lakes or other navigable waterways, they are considered to be a vessel and must abide by the provisions of CAR 602.20. (See RAC 1.10.)

The attention of all pilots and aircraft owners is drawn to the Canada Shipping Act, 2001, and the Canada Marine Act. The Canada Marine Act provides harbour commissions and port authorities with the authority to restrict vessel operations on the bodies of water that are in their jurisdiction

Restrictions established by the above authorities relating to vessels apply to aircraft underway or at rest on the water of a harbour, and operators are advised to furnish themselves with copies of the appropriate regulations as published by such harbour commissions or port authorities.

In addition, the Canada Shipping Act, 2001, through the Vessel Operation Restriction Regulations prohibits or imposes restrictions on the operation of vessels on certain lakes and waterways within Canada. The bodies of water affected and applicable restrictions may be found in the schedules to the Vessel Operation Restriction Regulations (<http://laws-lois.justice.gc.ca/eng/regulations/SOR-2008-120/page-6.html>).

2.11.2 Ditching

When flying over water, a pilot must always consider the possibility of ditching. Aircraft operating handbooks usually contain instructions on ditching that are applicable to the type of aircraft. Also, the Flight Training Manual (TP 1102E) discusses this topic.

Before flying over water, pilots should be aware of the regulatory requirements, some of which are outlined in AIR 2.11.3.

On the high seas, it is best to ditch parallel and on top of the primary swell system, except in high wind conditions. The primary swell is usually recognized first because it is easier to see from a higher altitude while secondary systems may only be visible at a lower altitude. Wind effect may only be discernible at a much lower altitude from the appearance of the white caps. It is possible for the primary swell system to disappear from view once lower altitudes are reached as it becomes hidden by secondary systems and the wind chop.

Some guidelines can be adopted:

(a) Never land into the face of a primary swell system unless the winds are extremely high. The best ditching heading is usually parallel to the primary swell system.

(b) In strong winds it may be desirable to compromise by ditching more into the wind and slightly across the swell system.

Decide as early as possible that ditching is inevitable, so that power can be used to achieve the optimum impact conditions. This would permit a stabilized approach at a low rate of descent at the applicable ditching speed.

Communicate. Initially, broadcast on the last frequency in use, then switch to 121.5 as many air carriers at high altitude have a VHF radio set on 121.5. Set off the ELT if able; SARSAT has a very good chance of picking up the signal. Set your transponder to 7700. Many coastal radars will detect the signal at extremely long ranges over the water.

Surviving a ditching is one thing, but immersion and the time spent in the cold water is possibly even more hazardous. Ensure that all equipment needed for flotation and the prevention of hypothermia from a lengthy exposure to cold water is on board and available. Brief passengers on their expected actions including their responsibilities for the handling of emergency equipment, once the aircraft has stopped in the water.

2.11.3 Life-Saving Equipment For Aircraft Operating Over Water

Life jackets suitable for each person on board are required to be carried on all aircraft taking off from and landing on water, and on all single-engine aircraft flown over water beyond gliding distance from shore. Complete requirements are contained in CARs 602.62 and 602.63.

2.11.4 Landing Seaplanes on Glassy Water

It is practically impossible to judge altitude when landing a seaplane or skiplane under certain conditions of surface and light. The following procedure should be adopted when such conditions exist.

Power assisted approaches and landings should be used although considerably more space will be required. The landing should be made as close to the shoreline as possible, and parallel to it, the height of the aircraft above the surface being judged from observation of the shoreline. Objects on the surface such as weeds and weed beds can be used for judging height. The recommended practice is to make an approach down to 200 ft (300 ft to 400 ft where visual aids for judgement of height are not available) and then place the aircraft in a slightly nose high attitude. Adjust power to maintain a minimum rate of descent, maintaining the recommended approach speed for the type until the aircraft is in contact with the surface. Do not “feel for the surface”. At the point of contact, the throttle should be eased off gently while maintaining back pressure on the control column to hold a nose high attitude which will prevent the floats from digging in as the aircraft settles into the water. Care must be taken to trim the aircraft properly to ensure that there is no slip or skid at the point of contact.

This procedure should be practised to give the pilot full confidence. It is recommended that the same procedure be used for unbroken snow conditions.

 

2.12 Flight Operations in Winter

2.12.1 General

The continuing number of accidents involving all types and classes of aircraft indicates that misconceptions exist regarding the effect on performance of frost, snow or ice accumulation on aircraft.

Most commercial transport aircraft, as well as some other aircraft types, have demonstrated some capability to fly in icing conditions and have been so certified. This capacity is provided by installing de-icing or anti-icing equipment on or in critical areas of equipment, such as the leading edges of the wings and empennage, engine cowls, compressor inlets, propellers, stall warning devices, windshields and pitots. However, this equipment does not provide any means of de-icing or anti-icing the wings or empennage of an aircraft that is on the ground.

2.12.2 Aircraft Contamination on the Ground—Frost, Ice or Snow

(a) General Information: Where frost, ice or snow may reasonably be expected to adhere to the aircraft, the Canadian aviation regulations require that an inspection or inspections be made before takeoff or attempted takeoff. The type and minimum number of inspections is indicated by the regulations, and depends on whether or not the operator has an approved Operator’s Ground Icing Operations Program using the Ground Icing Operations Standard as specified in CAR 622.11 – Operating and Flight Rules Standards.

The reasons for the regulations are straightforward. The degradation in aircraft performance and changes in flight characteristics when frozen contaminants are present are wide ranging and unpredictable. Contamination makes no distinction between large aircraft, small aircraft or helicopters, the performance penalites and dangers are just as real.

The significance of these effects are such that takeoff should not be attempted unless the pilot-in-command has determined, as required by the CARs, that frost ice or snow contamination is not adhering to any aircraft critical surfaces.

(b) Critical Surfaces: Critical surfaces of an aircraft means the wings, control surfaces, rotors, propellers, horizontal stabilizers, vertical stabilizers or any other stabilizing surface of an aircraft and, in the case of an aircraft that has rear-mounted engines, includes the upper surface of its fuselage.

Flight safety during ground operations in conditions conducive to frost, ice or snow contamination requires a knowledge of:

(i) adverse effects of frost, ice or snow on aircraft performance and flight characteristics, which are generally reflected in the form of decreased thrust, decreased lift, increased drag, increased stall speed, trim changes, altered stall characteristics and handling qualities;

(ii) various procedures available for aircraft ground de-icing and anti-icing, and the capabilities and limitations of these procedures in various weather conditions, including the use and effectiveness of freezing point depressant (FPD) fluids;

(iii) holdover time, which is the estimated time that an application of an approved de-icing/anti-icing fluid is effective in preventing frost, ice, or snow from adhering to treated surfaces. Holdover time is calculated as beginning at the start of the final application of an approved de-icing/ anti-icing fluid and as expiring when the fluid is no longer effective. The fluid is no longer effective when its ability to absorb more precipitation has been exceeded. This produces a visible surface build-up of contamination. Recognition that final assurance of a safe takeoff rests in the pretakeoff inspection.

(c) The Clean Aircraft Concept: CARs prohibit takeoff when frost, ice or snow is adhering to any critical surface of the aircraft. This is referred to as “The Clean Aircraft Concept”.

It is imperative that takeoff not be attempted in any aircraft unless the pilot-in-command has determined that all critical components of the aircraft are free of frost, ice or snow contamination. This requirement may be met if the pilot-in-command obtains verification from properly trained and qualified personnel that the aircraft is ready for flight.

(d) Frozen Contaminants: Test data indicate that frost, ice or snow formations having a thickness and surface roughness similar to medium or coarse sandpaper, on the leading edge and upper surface of a wing, can reduce wing lift by as much as 30% and increase drag by 40%. Even small amounts of contaminants have caused (and continue to cause) aircraft accidents which result in substantial damage and loss of life. A significant part of the loss of lift can be attributed to leading edge contamination. The changes in lift and drag significantly increase stall speed, reduce controllability, and alter aircraft flight characteristics. Thicker or rougher frozen contaminants can have increasing effects on lift, drag, stall speed, stability and control.

More than 30 factors have been identified that can influence whether frost, ice or snow will accumulate, cause surface roughness on an aircraft and affect the anti-icing properties of freezing point depressant fluids. These factors include ambient temperature; aircraft surface temperature; the de-icing and anti-icing fluid type, temperature and concentration; relative humidity; and wind speed and direction. Because many factors affect the accumulation of frozen contaminants on the aircraft surface, holdover times for freezing point depressant fluids should be considered as guidelines only, unless the operator’s Ground Icing Operations program allows otherwise.

The type of frost, ice or snow that can accumulate on an aircraft while on the ground is a key factor in determining the type of de-icing/anti-icing procedures that should be used.

Where conditions are such that ice or snow may reasonably be expected to adhere to the aircraft, it must be removed before takeoff. Dry, powdery snow can be removed by blowing cold air or compressed nitrogen gas across the aircraft surface. In some circumstances, a shop broom could be employed to clean certain areas accessible from the ground. Heavy, wet snow or ice can be removed by placing the aircraft in a heated hangar, by using solutions of heated freezing point depressant fluids and water, by mechanical means (such as brooms or squeegees), or a combination of all three methods. Should the aircraft be placed in a heated hanger, ensure it is completely dry when moved outside; otherwise, pooled water may refreeze in critical areas or on critical surfaces.

A frost that forms overnight must be removed from the critical surfaces before takeoff. Frost can be removed by placing the aircraft in a heated hangar or by other normal de–icing procedures.

(e) The Cold-Soaking Phenomenon: Where fuel tanks are located in the wings of aircraft, the temperature of the fuel greatly affects the temperature of the wing surface above and below these tanks. After a flight, the temperature of an aircraft and the fuel carried in the wing tanks may be considerably colder than the ambient temperature. An aircraft’s cold-soaked wings conduct heat away from precipitation so that, depending on a number of factors, clear ice may form on some aircraft, particularly on wing areas above the fuel tanks. Such ice is difficult to see and, in many instances, cannot be detected other than by touch with the bare hand or by means of a special purpose ice detector. A layer of slush on the wing can also hide a dangerous sheet of ice beneath.

Clear ice formations could break loose at rotation or during flight, causing engine damage on some aircraft types, primarily those with rear-mounted engines. A layer of slush on the wing can also hide a dangerous sheet of ice beneath.

The formation of ice on the wing is dependent on the type, depth and liquid content of precipitation, ambient air temperature and wing surface temperature. The following factors contribute to the formation intensity and the final thickness of the clear ice layer:

(i) low temperature of the fuel uplifted by the aircraft during a ground stop and/or the long airborne time of the previous flight, resulting in a situation that the remaining fuel in the wing tanks is subzero. Fuel temperature drops of up to 18°C have been recorded after a flight of two hours;

(ii) an abnormally large amount of cold fuel remaining in the wing tanks causing fuel to come in contact with the wing upper surface panels, especially in the wing root area;

(iii) weather conditions at the ground stop, wet snow, drizzle or rain with the ambient temperature around 0°C is very critical. Heavy freezing has been reported during drizzle or rain even in a temperature range between +8° to +14°C.

As well, cold-soaking can cause frost to form on the upper and lower wing under conditions of high relative humidity. This is one type of contamination that can occur in above-freezing weather at airports where there is normally no need for de-icing equipment, or where the equipment is deactivated for the summer. This contamination typically occurs where the fuel in the wing tanks becomes cold-soaked to below-freezing temperatures because of low temperature fuel uplifted during the previous stop, or cruising at altitudes where low temperatures are encountered, or both, and a normal descent is made into a region of high humidity. In such instances, frost will form on the under and upper sides of the fuel tank region during the ground turn-around time, and tends to re-form quickly even when removed.

Frost initially forms as individual grains about 0.004 of an inch in diameter. Additional build-up comes through grain growth from 0.010 to 0.015 of an inch in diameter, grain layering, and the formation of frost needles. Available test data indicate that this roughness on the wing lower surface will have no significant effect on lift, but it may increase drag and thereby decrease climb gradient capability which results in a second segment limiting weight penalty.

Skin temperature should be increased to preclude formation of ice or frost prior to take-off. This is often possible by refuelling with warm fuel or using hot freezing point depressant fluids, or both.

In any case, ice or frost formations on upper or lower wing surfaces must be removed prior to takeoff. The exception is that takeoff may be made with frost adhering to the underside of the wings provided it is conducted in accordance with the aircraft manufacturer’s instructions.

(f) De-Icing and Anti-Icing Fluids: Frozen contaminants are most often removed in commercial operations by using freezing point depressant fluids. There are a number of freezing point depressant fluids available for use on commercial aircraft and, to a lesser extent, on general aviation aircraft. De-icing and anti-icing fluids should not be used unless approved by the aircraft manufacturer.

Although freezing point depressant fluids are highly soluble in water, they absorb or melt ice slowly. If frost, ice or snow is adhering to an aircraft surface, the accumulation can be melted by repeated application of proper quantities of freezing point depressant fluid. As the ice melts, the freezing point depressant mixes with the water, thereby diluting the freezing point depressant. As dilution occurs, the resulting mixture may begin to run off the aircraft. If all the ice is not melted, additional application of freezing point depressant becomes necessary until the fluid penetrates to the aircraft surface. When all the ice has melted, the remaining liquid residue is a mixture of freezing point depressant and water at an unknown concentration. The resulting film could freeze (begin to crystallize) rapidly with only a slight temperature decrease. If the freezing point of the film is found to be insufficient, the de-icing procedure must be repeated until the freezing point of the remaining film is sufficient to ensure safe operation.

The de-icing process can be sped up considerably by using the thermal energy of heated fluids and the physical energy of high-pressure spray equipment, as is the common practice.

(g) SAE and ISO Type I Fluids: These fluids in the concentrated form contain a minimum of 80% glycol and are considered “unthickened” because of their relatively low viscosity. These fluids are used for de-icing or anti-icing, but provide very limited
anti-icing protection.

(h) SAE and ISO Type II Fluids: Fluids, such as those identified as SAE Type II and ISO Type  II, will last longer in conditions of precipitation. They afford greater margins of safety if they are used in accordance with aircraft manufacturers’ recommendations.

Flight tests performed by manufacturers of transport category aircraft haveshown that most SAE and ISO Type II fluids flow off lifting surfaces byrotation speeds (Vr), although some large aircraft do experience performance degradation and may require weight or other takeoff compensation. Therefore, SAE and ISO Type II fluids should be used on aircraft with rotation speeds (Vr) above 100 KT. Degradation could be significant on aeroplanes with rotation speeds below this figure.

As with any de-icing or anti-icing fluid, SAE and ISO Type II fluids should not be applied unless the aircraft manufacturer has approved their use, regardless of rotation speed. Aircraft manufacturers’ manuals may give further guidance on the acceptability of SAE and ISO Type II fluids for specific aircraft.

Some fluid residue may remain throughout the flight. The aircraft manufacturer should have determined that this residue would have little or no effect on aircraft performance or handling qualities in aerodynamically quiet areas; however, this residue should be cleaned periodically.

SAE and ISO Type II fluids contain no less than 50% glycol and have a minimum freeze point of -32°C. They are considered “thickened” because of added thickening agents that enable the fluid to be deposited in a thicker film and to remain on the aircraft surfaces until the time of takeoff. These fluids are used for de-icing (when heated) and anti-icing. Type II fluids provide greater protection (holdover time) than do Type I fluids against frost, ice or snow formation in conditions conducive to aircraft icing on the ground.

These fluids are effective anti-icers because of their high viscosity and pseudoplastic behaviour. They are designed to remain on the wings of an aircraft during ground operations or short-term storage, thereby providing some anti-icing protection and will readily flow off the wings during takeoff. When these fluids are subjected to shear stress (such as that experienced during a takeoff run), their viscosity decreases drastically, allowing the fluids to flow off the wings and causing little adverse effect on the aircraft’s aerodynamic performance.

The pseudoplastic behaviour of SAE and ISO Type II fluids can be altered by improper de-icing/anti-icing equipment or handling. Therefore, some North American airlines have updated de-icing and anti-icing equipment, fluid storage facilities, de-icing and anti-icing procedures, quality control procedures, and training programs to accommodate these distinct characteristics. Testing indicates that SAE and ISO Type II fluids, if applied with improper equipment, may lose 20 to 60% of their anti-icing performance.

All Type II fluids are not necessarily compatible with all Type I fluids; therefore, you should refer to the fluid manufacturer or supplier for further information. As well, the use of Type II fluid over badly contaminated Type I fluid will reduce the effectiveness of the Type II fluid.

SAE and ISO Type II fluids were introduced in North America in 1985, with widespread use beginning to occur in 1990. Similar fluids, but with slight differences in characteristics, have been developed, introduced, and used in Canada.

(i) Type III Fluids: Type III is a thickened freezing point depressant fluid which has properties that lie between Types I and II. Therefore, it provides a longer holdover time than Type I, but less than Type II. Its shearing and flow-off characteristics are designed for aircraft that have a shorter time to the rotation point. This should make it acceptable for some aircraft that have a Vr of less than 100 KT.

The SAE had approved a specification in AMS1428A for Type III anti-icing fluids that can be used on those aircraft with rotation speeds significantly lower than the large jet rotation speeds, which are 100 KT or greater. No fluid has yet been identified that can meet the entire Type III fluid specification. Pending publication of a Type III Holdover Time Table and availability of suitable fluids, the Union Carbide Type IV fluid in 75/25 dilution may be used for anti-icing purposes on low rotation speed aircraft, but only in accordance with aircraft and fluid manufacturer’s instructions.

(j) Type IV Fluids: A significant advance is Type IV anti-icing fluid. These fluids meet the same fluid specifications as the Type II fluids and in addition have a significantly longer holdover time. In recognition of the above, Holdover Time Tables are available for Type IV.

The Product is dyed green as it is believed that the green product will provide for application of a more consistent layer of fluid to the aircraft and will reduce the likelihood that fluid will be mistaken for ice. However, as these fluids do not flow as readily as conventional Type II fluid, caution should be exercised to ensure that enough fluid is used to give uniform coverage.

Research indicates that the effectiveness of a Type IV fluid can be seriously diminished if proper procedures are not followed when applying it over Type I fluid.

All fluid users are advised to ensure that these fluids are applied evenly and thoroughly and that an adequate thickness has been applied in accordance with the manufacturer’s recommendations. Particular attention should be paid to the leading edge area of the wing and horizontal stabilizer.

Further information on aircraft critical surface contamination may be found in the training packages produced by Transport Canada, When In Doubt … Small and Large Aircraft, and Ground Crew, Critical Surface Contamination Training booklets and video cassettes. These priced videos and the accompanying booklets may be ordered from the Civil Aviation Communications Centre:

North America only: 1-800-305-2059
Local number: 613-993-7284
Fax: 613-957-4208
E-mail: services@tc.gc.ca

2.12.3 Aircraft Contamination in Flight—Inflight Airframe Icing

Airframe icing can be a serious weather hazard to fixed and rotary wing aircraft in flight. Icing will result in a loss of performance in the following areas:

(a) ice accretion on lifting surfaces will change their aerodynamic properties resulting in a reduction in lift, increase in drag and weight with a resultant increase in stalling speed and a reduction in the stalling angle of attack. Therefore, an aerodynamic stall can occur before the stall warning systems activate;

(b) ice adhering to propellers will drastically affect their efficiency and may cause an imbalance with resultant vibration;

(c) ice adhering to rotor blades will degrade their aerodynamic efficiency. This means that an increase in power will be required to produce an equivalent amount of lift Therefore, during an autorotation this increase can only come from a higher than normal rate of descent. In fact, it may not be possible to maintain safe rotor RPM’s during the descent and flare due to ice contamination;

(d) ice on the windshield or canopy will reduce or block vision from the flight deck or cockpit;

(e) carburetor icing, see AIR 2.3; and

(f) airframe ice may detach and be ingested into jet engine intakes causing compressor stalls, loss of thrust and flame out.

2.12.3.1 Types of Ice

There are three types of ice which pilots must contend with in flight, Rime Ice, Clear Ice and Frost (see MET 2.4). For any ice to form the OAT must be at or below freezing with the presence of visible moisture.

Rime ice commonly found in stratiform clouds is granular, opaque and pebbly and adheres to the leading edges of antennas and windshields. Rime ice forms in low temperatures with a low concentration of small super-cooled droplets. It has little tendency to spread and can easily be removed by aircraft de-icing systems.

Clear ice commonly found in cumuliform clouds is glassy, smooth and hard, and tends to spread back from the area of impingement. Clear ice forms at temperatures at or just below 0°C with a high concentration of large super-cooled droplets. It is the most serious form of icing because it adheres firmly and is difficult to remove.

Frost may form on an aircraft in flight when descent is made from below-freezing conditions to a layer of warm, moist air. In these circumstances, vision may be restricted as frost forms on the windshield or canopy.

Additional references on icing include MET 2.4 and the Air Command Weather Manual (TP 9352E).

2.12.3.2 Aerodynamic Effects of Airborne Icing

Commercial pilots are familiar with the classic aerodynamic effects of ice accumulation on an aeroplane in flight. These can include:

(a) reduced lift accompanied by significant increases in drag and increases in weight;

(b) increases in stall speed and reduced stall angle of attack as ice alters the shape of an airfoil and disrupts airflow;

(c) reduced thrust due to ice disrupting the airflow to the engine and/or degrading propeller efficiency. Ice ingested into a jet engine may induce a compressor stall and/or a flame out;

(d) control restrictions due to water flowing back into control surfaces and freezing;

(e) ice adhering to rotor blades will degrade their aerodynamic efficiency. This means that an increase in power will be required to produce an equivalent amount of lift. Therefore, during an autorotation this increase can only come from a higher than normal rate of descent. In fact, it may not be possible to maintain safe rotor RPM during the descent and flare due to ice contamination;

(f) ice on the windshield or canopy will reduce or block vision from the flight deck or cockpit; and

(g) carburetor icing (see AIR 2.3).

2.12.3.3 Roll Upset

Roll upset describes an uncommanded and possibly uncontrollable rolling moment caused by airflow separation in front of the ailerons, resulting in self-deflection of unpowered control surfaces. It is associated with flight in icing conditions in which water droplets flow back behind the protected surfaces before freezing and form ridges that cannot be removed by de-icing equipment. Roll upset has recently been associated with icing conditions involving large super-cooled droplets; however, it theoretically can also occur in conventional icing conditions when temperatures are just slightly below 0°C.

The roll upset can occur well before the normal symptoms of ice accretion are evident to the pilot, and control forces may be physically beyond the pilot’s ability to overcome. Pilots may receive a warning of incipient roll upset if abnormal or sloppy aileron control forces are experienced after the autopilot is disconnected when operating in icing conditions.

Corrective Actions

If severe icing conditions are inadvertently encountered, pilots should consider the following actions to avoid a roll upset:

1. Disengage the autopilot. The autopilot may mask important clues or may self disconnect when control forces exceed limits, presenting the pilot with abrupt unusual attitudes and control forces.

2. Reduce the angle of attack by increasing speed. If turning, roll wings level.

3. If flaps are extended, do not retract them unless it can be determined that the upper surface of the wing is clear of ice. Retracting the flaps will increase the angle of attack at any given airspeed, possibly leading to the onset of roll upset.

4. Set appropriate power and monitor airspeed /angle of attack.

5. Verify that wing ice protection is functioning symmetrically by visual observation if possible. If not, follow the procedures in the aircraft flight manual.

2.12.3.4 Tail Plane Stall

As the rate at which ice accumulates on an airfoil is related to the shape of the airfoil, with thinner airfoils having a higher collection efficiency than thicker ones, ice may accumulate on the horizontal stabilizer at a higher rate than on the wings. A tail plane stall occurs when its critical angle of attack is exceeded. Because the horizontal stabilizer produces a downward force to counter the nose-down tendency caused by the centre of lift on the wing, stall of the tail plane will lead to a rapid pitch down. Application of flaps, which may reduce or increase downwash on the tail plane depending on the configuration of the empennage (i.e., low set horizontal stabilizer, mid-set, or T-tail), can aggravate or initiate the stall. Therefore, pilots should be very cautious in lowering flaps if tail plane icing is suspected. Abrupt nose-down pitching movements should also be avoided, since these increase the tail plane angle of attack and may cause a contaminated tail plane to stall.

A tail plane stall can occur at relatively high speeds, well above the normal 1G stallspeed. The pitch down may occur without warning and be uncontrollable. It is more likely to occur when the flaps are selected to the landing position, after a nose-down pitching manoeuvre, during airspeed changes following flap extension, or during flight through wind gusts.

Symptoms of incipient tail plane stall may include:

(a) abnormal elevator control forces, pulsing, oscillation, or vibration;

(b) an abnormal nose-down trim change (may not be detected if autopilot engaged);

(c) any other abnormal or unusual pitch anomalies (possibly leading to pilot induced oscillations);

(d) reduction or loss of elevator effectiveness (may not be detected if the autopilot is engaged);

(e) sudden change in elevator force (control would move down if not restrained); and/or

(f) a sudden, uncommanded nose-down pitch.

Corrective Actions

If any of the above symptoms occur, the pilot should consider the following actions unless the aircraft flight manual dictates otherwise:

1. Plan approaches in icing conditions with minimum flap settings for the conditions. Fly the approach on speed for the configuration.

2. If symptoms occur shortly after flap extension, immediately retract the flaps to the previous setting. Increase airspeed as appropriate to the reduced setting.

3. Apply sufficient power for the configuration and conditions. Observe the manufacturer’s recommendations concerning power settings. High power settings may aggravate tail plane stall in some designs.

4. Make any nose-down pitch changes slowly, even in gusting conditions, if circumstance allow.

5. If equipped with a pneumatic de-icing system, operate several times to attempt to clear ice from the tail plane.

WARNINGS

1: At any flap setting, airspeed in excess of the manufacturer’s recommendations for the configuration and environmental conditions, accompanied by uncleared ice on the tail plane, may result in a tail plane stall and an uncontrollable nose-down pitch.

2: Improper identity of the event and application of the wrong recovery procedure will make an already critical situation even worse. This information concerning roll upset and tail plane stall is necessarily general in nature, and may not be applicable to all aircraft configurations. Pilots must consult their aircraft flight manual to determine type specific procedures for these phenomena.

2.12.3.5 Freezing Rain, Freezing Drizzle, and Large Super-Cooled Droplets

The classical mechanism producing freezing rain and/or freezing drizzle aloft involves a layer of warm air overlaying a layer of cold air. Snow falling through the warm layer melts, falls into the cold air, becomes supercooled, and freezes on contact with an aircraft flying through the cold air. Freezing rain and freezing drizzle are therefore typically found near warm fronts and trowals, both of which cause warm air to overlay cold air. Freezing rain or freezing drizzle may also occur at cold fronts, but are less common and would have a lesser horizontal extent due to the steeper slope of the frontal surface. The presence of warm air above has always provided a possible escape route to pilots who have encountered classical freezing precipitation aloft through a climb into the warm air.

Recent research has revealed that there are other non-classical mechanisms that produce freezing precipitation aloft. Flights by research aircraft have encountered freezing drizzle at temperatures down to -10° C at altitudes up to 15000 feet ASL. There was no temperature inversion-that is, no warm air aloft-present in either case. Pilots must be aware that severe icing may be encountered in conditions unrelated to warm air aloft. They must also understand that, if non-classical freezing drizzle is encountered in flight, the escape route of a climb into warmer air may not be immediately available; however, climbing remains the preferred escape route. It should allow the aircraft to reach an altitude above the formation region, while a descent may keep the aircraft in freezing precipitation. It should be noted that, while ascending, the aircraft might get closer to the source region with smaller droplets, higher liquid water content and conventional icing.

2.12.3.6 Detecting Large Super-Cooled Droplets Conditions in Flight

Visible clues to flight crew that the aircraft is operating in large super-cooled droplets conditions will vary from type to type. Manufacturers should be consulted to assist operators in identifying the visible clues particular to the type operated. There are, however, some general clues of which pilots should be aware:

(a) ice visible on the upper or lower surface of the wing aft of the area protected by de-icing equipment (irregular or jagged lines of ice or pieces that are self-shedding);

(b) ice adhering to non-heated propeller spinners farther aft than normal;

(c) granular dispersed ice crystals or total translucent or opaque coverage of the unheated portions of front or side windows. This may be accompanied by other ice patterns on the windows such as ridges. Such patterns may occur within a few seconds to one half minute after exposure to large super-cooled droplets;

(d) unusually extensive coverage of ice, visible ice fingers or ice feathers on parts of the airframe on which ice does not normally appear; and

(e) significant differences between airspeed or rate of climb expected and that attained at a given power setting.

Additional clues significant at temperatures near freezing:

(a) visible rain consisting of very large droplets. In reduced visibility selection of landing or taxi lights “on” occasionally will aid detection. Rain may also be detected by the audible impact of droplets on the fuselage;

(b) droplets splashing or splattering on the windscreen. The 40 to 50 micron droplets covered by Appendix C to Chapter 525 of the Airworthiness Manual icing criteria (Appendix C lists the certification standard for all transport category aeroplanes for flight in known icing), are so small that they cannot usually be detected; however freezing drizzle droplets can reach sizes of 0.2 to 0.5 mm and can be seen when they hit the windscreen;

(c) water droplets or rivulets streaming on windows, either heated or unheated. Streaming droplets or rivulets are indicators of high liquid water content in any sized droplet; and/or

(d) weather radar returns showing precipitation. Whenever the radar indicates precipitation in temperatures near freezing, pilots should be alert for other clues of large super-cooled droplets.

2.12.3.7 Flight Planning or Reporting

Pilots should take advantage of all information available to avoid or, at the very least, to plan a safe flight through known icing conditions. As well as FAs, TAFs, and METARs, pilots should ask for pertinent SIGMETs and any PIREPs received along the planned route of flight. Significant Weather Prognostic Charts should be studied, if available. Weather information should be analyzed to predict where icing is likely to be found, and to determine possible safe exit procedures should severe icing be encountered. Pilots should routinely pass detailed PIREPs whenever icing conditions
are encountered.

2.12.4 Landing Wheel-Equipped Light Aircraft on Snow-Covered Surfaces

During the course of each winter, a number of aircraft accidents have occurred due to pilots attempting to land wheel-equipped aircraft on surfaces covered with deep snow. This has almost invariably resulted in the aircraft nosing over.

Light aircraft should not be landed on surfaces covered with snow unless it has previously been determined that the amount of snow will not constitute a hazard.

The pamphlet Flying with Skis (TP 4883E), is available from your RASO.

2.12.5 Use of Seaplanes on Snow Surfaces

The operation of float-equipped aircraft or flying boats from snow covered surfaces will be permitted by Transport Canada under the following conditions:

(a) the pilot and operator will be held responsible for confining all flights to those snow conditions found to be satisfactory as a result of previous tests or experimental flights in that type of aircraft;

(b) passengers should not be carried; and

(c) a thorough inspection of the float or hull bottom, all struts and fittings, all wing fittings, bracing, wing tip floats and fittings should be carried out after every flight to ensure that the aircraft is airworthy.

Seaplanes should not be landing on, or taking off from, snow surfaces except under conditions of deep firm snow, which should not be drifted or heavily crusted.

Flights should not be attempted if there is any adhesion of ice or snow to the under surface of the float or hull. When landing or forced landing a ski or float equipped aeroplane on unbroken snow surfaces, the procedure in AIR 2.11.4 is recommended.

2.12.6 Landing Seaplanes on Unbroken Snow Conditions

It has been found practically impossible to judge altitude when landing a skiplane or seaplane under certain conditions of surface and light. Under such conditions the procedures for landing seaplanes on glassy water should be used (see AIR 2.11.4).

2.12.7 Whiteout

Whiteout (also called milky weather) is defined in the Glossary of Meteorology (published by the American Meteorological Society) as:

“An atmospheric optical phenomenon of the polar regions in which the observer appears to be engulfed in a uniformly white glow. Neither shadows, horizon, nor clouds are discernible; sense of depth and orientation is lost; only very dark, nearby objects can be seen. Whiteout occurs over an unbroken snow cover and beneath a uniformly overcast sky, when with the aid of the snowblink effect, the light from the sky is about equal to that from the snow surface. Blowing snow may be an additional cause.”

Light carries depth perception messages to the brain in the form of colour, glare, shadows, and so on. These elements have one thing in common, namely, they are all modified by the direction of the light and changes in light intensity. For example, when shadows occur on one side of objects, we subconsciously become aware that the light is coming from the other. Thus, nature provides many visual clues to assist us in discerning objects and judging distances. What happens if these clues are removed? Let’s suppose that these objects on the ground and the ground itself are all white. Add to that, a diffused light source through an overcast layer which is reflected back in all directions by the white surface so that shadows disappear. The terrain is now virtually devoid of visual clues and the eye no longer discerns the surface or terrain features.

Since the light is so diffused, it is likely that the sky and terrain will blend imperceptibly into each other, obliterating the horizon. The real hazard in whiteout is the pilot not suspecting the phenomenon because the pilot is in clear air. In numerous whiteout accidents, pilots have flown into snow-covered surfaces unaware that they have been descending and confident that they could “see” the ground.

Consequently, whenever a pilot encounters the whiteout conditions described above, or even a suspicion of them, the pilot should immediately climb if at low level, or level off and turn towards an area where sharp terrain features exist. The flight should not proceed unless the pilot is prepared and competent to traverse the whiteout area on instruments.

In addition, the following phenomena are known to cause whiteout and should be avoided if at all possible:

(a) water-fog whiteout resulting from thin clouds of super-cooled water droplets in contact with the cold snow surface. Depending on the size and distribution of the water droplets, visibility may be minimal or nil in such conditions.

(b) blowing snow whiteout resulting from fine snow being plucked from the surface by winds of 20 KT or more. Sunlight is reflected and diffused resulting in a nil visibility whiteout condition.

(c) precipitation whiteout resulting from small wind-driven snow crystals falling from low clouds above which the sun is shining. Light reflection complicated by spectral reflection from the snow flakes and obscuration of land marks by falling snow can reduce visibility and depth perception to nil in such conditions.

If at all possible, pilots should avoid such conditions unless they have the suitable instruments in the aircraft and are sufficiently experienced to use a low-speed and minima rate of descent technique to land the aircraft safely.

 

2.13 Flight Operations in Mountainous Areas

The importance of proper training, procedures and pre-flight planning when flying in mountainous regions is emphasized.

In the Pacific area, the combined effect of the great mountain system and the adjacent Pacific Ocean lead to extremely changeable weather conditions and a variety of weather patterns. Some of the factors to be taken into consideration regarding the effect on aircraft performance when operating under these conditions include the following:

(a) elevation of the airport;

(b) temperature and pressure;

(c) turbulence and wind effect; and

(d) determination of safe takeoff procedures to ensure clearance over obstacles and intervening high ground.

In the western mountainous region VFR routes may be marked by diamonds on visual navigation charts. The routes are marked for convenience to assist pilots with pre-flight planning. The diamond marks do not imply any special level of facilities and services along the route. Pilots are cautioned that the use of the marked routes does not absolve them from proper pre-flight planning or the exercising of good airmanship practices during the proposed flight. Alternative unmarked routes are always available, the choice of a suitable route for the intended flight and conditions remains the sole responsibility of the pilot-in-command.

2.14 Flight Operations in Sparsely Settled Areas of Canada

“Sparsely settled area” is no longer a defined area. As such, the pilot/operator must decide what survival equipment is to be carried on board the aircraft in accordance with
the regulations.

CAR 602.61, “Survival Equipment—Flights Over Land”, regulates the survival equipment required for aircraft operations over land in Canada. The regulation requires a pilot to carry on board the aircraft survival equipment sufficient for the survival on the ground of each person on board, taking into consideration the geographical area, the season of the year, and anticipated seasonal climatic variations. The survival equipment must be sufficient to provide the means for starting a fire, providing shelter, providing or purifying water, and visually signalling distress. The AIR Annex contains a table that is a useful guide in helping pilots and operators choose equipment to ensure that they are operating within the regulations.

Experience has shown that pilots who are not familiar with the problems associated with navigating as well as other potential dangers of operating aircraft in sparsely settled areas of Canada tend to underestimate the difficulties involved.

Some pilots assume that operating in this area is no different than operating in the more populated areas. This leads to a lack of proper planning and preparation that can result in pilots exposing themselves, their crew, passengers and aircraft to unnecessary risks. This in turn can lead to considerable strain being placed on very limited local resources at stop-over or destination aerodromes. It has resulted in lengthy and expensive searches that could have been avoided with careful planning and preparation. Also, it has resulted in unnecessary loss of life.

Sparsely settled areas of Canada require special considerations for aircraft operations. In this area, radio aids to navigation, weather information, fuel supplies, aircraft servicing facilities, accommodation and food are usually sparse and sometimes non-existent. There are four factors to which pilots planning to operate into this area should pay particular attention.

(a) Flight Planning: Plan your flight using current aeronautical charts and the latest edition of the CFS. Check NOTAM and AIP Canada (ICAO) Supplements. Familiarize yourself with the nature of the terrain over which the flight is to be conducted. If you are not familiar with the area, consult officials of the RCMP, DND or TC at the appropriate local regional offices before departure. These officials, as well as local pilots and operators, can provide a great deal of useful advice, especially on the ever changing supply situation, the location and condition of possible emergency strips, potential hazards and en route weather conditions. In preflight planning, you must ensure that the fuel, food, accommodation and services you may require at intermediate stops and at your destination will be available.

(b) Weather: Weather observation stations are scattered compared to more densely populated areas. This means that snow or rain showers, thunderstorms, strong winds, fog, cloud conditions, icing, and whiteout may exist that are unobserved and, therefore, not reported.

Experienced pilots know that whiteout can be extremely hazardous to visual flight. Whiteout can affect visibility to the extent that a pilot may have little or no visual reference by which to control his aircraft.

A thorough weather briefing before departure is a must. During the flight, use whatever communication facilities are available to obtain updated information on current weather conditions.

(c) Navigation: Flights in sparsely settled areas of Canada are likely to be over longer than average legs with fewer navigation aids. Further, the route may be over terrain that is uniform in appearance with very few distinguishing features to use as reliable check points. For example, the terrain may be covered with lakes to the extent that, for the pilot who is not familiar with the area, distinguishing one lake from another is very difficult. The route may be over large tracts of unbroken forest or over tundra. In the winter, when lakes and tundra are frozen, the problem of identifying terrain features is even more acute.

Within the Northern Domestic Airspace (NDA), bearings and headings are shown on charts in degrees True (i.e., 135°T). It is strongly recommended that aircraft, engaged in day VFR flying within this airspace, be equipped with a good directional gyro and a means of checking heading using the sun or other celestial bodies as reference. To this end a manual of tables has been prepared that greatly assists in determining the true meridian using the sun as reference. The true meridian information is then used to keep the “free” directional gyro in alignment. This manual, entitled “Finding the Sun’s True Bearing (TP 784E)”, is available from Transport Canada [see MAP 7.1 for the Civil Aviation Catalogue of Publications (TP 3680E)].

Pilots planning to fly IFR or night VFR in the NDA should review the regulations governing such flights. These are set out in CAR 602.34.

NOTE: Surface wind direction information for aerodromes located within the NDA, for purposes of takeoff and landing is reported in degrees True.

(d) Emergencies: In the event of a forced landing in sparsely settled areas of Canada, survival will depend on the preparations the pilot has made for such an eventuality and knowledge of ELT Search and Rescue procedures. These procedures are detailed in the SAR Section and a list of the equipment suggested for flight in this area is found in AIR Annex. The need to carry clothing and equipment that will provide protection from insects in the summer and exposure in the other seasons cannot be overstressed.

2.14.1 Single-Engine Aircraft Operating in Northern Canada

In addition to emergency equipment required for flights in sparsely settled areas, single-engine aircraft in northern Canada should carry the equipment described below.

(a) Outside Arctic Archipelago:

(i) Telecommunications Equipment:

(A) HF radio (with a minimum output of 30 watts) capable of transmitting and receiving on 5680 kHz, and

(B) a portable emergency transmitter capable of operation on the ground independent of the aircraft battery and transmitting on a distress frequency used by DND for search and rescue.

(ii) Navigation Equipment:

(A) A gyro-stabilized magnetic compass, or

(B) an astro compass and a low precession gyroscopic direction indicator.

NOTES 1: If an astro compass is carried it should be accompanied with the necessary tables and the operator should be proficient in its use.

2: Telecommunications equipment must be adequate to ensure compliance with CAR 602.146 – Security Control of Air Traffic and Air Navigation Aids Plan (SCATANA).

3: Frequency 5680 kHz is for use in accordance with COM 5.14.

4: If it can be shown to the satisfaction of Transport Canada that an aircraft is otherwise satisfactorily equipped, then the requirements set forth above may be modified for flights in the area south of the Arctic Archipelago.

(b) Within Arctic Archipelago: Operators proceeding to the Arctic Archipelago should meet the following additional requirements.

(i) Telecommunications Equipment: VHF capable of transmitting and receiving on 121.5 and 126.7 MHz.

(ii) Routing: In choosing the most suitable route, it must be remembered that under CARs, Part VII, no single-engined land plane or multi-engined land plane shall be operated on a commercial air service over water beyond gliding distance from shore except as authorized in its operator certificate, and complies with the Commercial Air Service Standards.

(iii) Emergency Equipment: In addition to the equipment suggested in the Survival Advisory Information detailed in AIR Annex, it is strongly recommended that flares, a small stove or heating device and sleeping bags to accommodate all persons on board the aircraft, be carried at all times.

(c) Flight Itinerary or Flight Plans: See RAC 3.6 to 3.10 inclusive.

2.15 Automatic Landing Operations

(See COM 3.13.1 for more information.)

Some States have developed procedures wherein practice Automatic Landing Operations (autolands) may be conducted on Category I ILS facilities, or on Category II/III ILS facilities when low visibility procedures are not in force. In the case of an ILS of facility performance Category I for example, the ILS should be of Category II signal quality, without necessarily meeting the associated reliability and availability criteria for backup equipment and automatic change-over of facility performance Category II. Other procedures include verifying Category I and II facilities can, in fact, support autoland operations; compatibility of the autoland system with the aerodrome surfaces preceding the runway threshold and the runway profile; notification by the crew of their intention to conduct a practice autoland; Air Traffic Control procedures to ensure protection of the ILS signal for practice autolands; and an ATC approval once the signal protection is effected.

Until such time as Canada establishes and implements procedures to safely accommodate practice autolands on Category I/II ILS facilities or on Category III ILS facilities without the requisite low visibility procedures active, flight crews are considered solely responsible for these practice autolands. Flight crews must recognize that changes in the ILS signal quality may occur rapidly and without any warning from the ILS monitor equipment. Furthermore, flight crews are reminded to exercise extreme caution whenever ILS signals are used beyond the minima specified in the approach procedure and when conducting autolands on any category of ILS when the critical area protection is not assured by air traffic control. Pilots must be prepared to immediately disconnect the autopilot and take appropriate action should unsatisfactory Automatic Flight Control Guidance System (AFCGS) performance occur during these operations.

2.16 Flight Operations at Night

There are many risks associated with operating aircraft in dark-night conditions where maintaining orientation, navigation and weather avoidance may become extremely difficult. Takeoff and landing may be particularly dangerous for both VFR and IFR pilots.

A variety of illusions may result at night because of a lack of outside visual cues. Your best defense, if you do not hold an instrument rating, is to receive some instrument training, and to be aware of the illusions and their counter measures.

Date modified:
2012-03-29