- Bumps in the Night
- Night VFR Video Black Holes and Little Grey Cells-Spatial Disorientation During NVFR
- When a Runway is Not Long Enough to Land On
- What's New in Icing
- Risk of Two Aircraft Colliding in Class D Airspace
- From the Investigator's Desk - Stall/Spin and Collision with Terrain
- Seat Belt Use: Reducing the Impact of Turbulence
This article is an authorized reprint from the March 2005 issue of Aviation Safety magazine.
Flying at night really isn't more dangerous than during the day, but it can be less forgiving. It just requires more planning and more care.
When pilots inevitably gather to discuss the various risks of certain flight operations, flying over mountains, in IMC [instrument meteorological conditions] or at night is always a lively topic. Someone will point out that, being an inanimate object, the airplane doesn't know what time it is, what the weather is or what it's flying over. Someone else will point out the illogic of refusing to fly at night, while another pilot will draw a line in the sand against it. Regardless of whether flying at night gives you the willies, is night flying really more dangerous than in the daytime?
Night-time flight operations offer a number of benefits when compared with flying the same route during the daylight hours. The air is generally smoother, there's less traffic, controllers are not as busy and can be more helpful, and traffic can be easier to spot. The only real problem is, well, it's dark. And, while it seems simple enough, because a pilot's ability to see and avoid unlighted objects is impaired at night, pilots need to plan ahead and respect the differences. As we shall see, finding and avoiding those objects can mean the difference between a safe, relaxing night flying experience and something else.
Unlike, say, continuing VFR into IMC, or reckless operation, there is no formal category for an aviation accident occurring during night-time flight operations. Instead, accident investigators simply round up the usual suspects after they collect all the necessary information and when they write a final report. Sometimes, the accident investigator's equivalent of an asterisk is appended to a report, noting that the event occurred at night.
Take, for example, the December 9, 2003, fatal crash of a Piper PA-28-181 in Sugar Land, Texas. The 350-hour non-instrument-rated private pilot was attempting a night landing in good visual conditions. After the pilot confirmed to the controller he saw the runway, the flight was cleared to land. Instead, the airplane struck power lines running perpendicular to the approach end of the runway, which featured a displaced threshold of 1 964 ft. Both aboard the Piper died in the crash. At the time, wind at the airport was reported from 320°, at 16 kt gusting to 25 kt. The NTSB [U.S. National Transportation Safety Board] determined the probable cause was the pilot's failure to avoid power lines and noted the night-time conditions and the high winds.
Later that month, on December 26, 2003, a Cessna 177RG was substantially damaged when it hit a deer during the landing rollout at Waterloo, Iowa. Again, night visual conditions prevailed. Neither the private pilot nor the ATP [airline transport pilot]-rated passenger was injured.
These two accidents demonstrate that, yes, night flying requires more careful operating practices. Rarely are power lines marked for night operations, but displaced thresholds are. Similarly, few deer are equipped with position lights, but airplanes have been known to collide with deer and other wildlife in broad daylight, too.
And then there's CFIT
Similarly, controlled flight into terrain (CFIT) accidents can happen in broad daylight, but operators are especially vulnerable after the sun goes down. A good example occurred on November 19, 2003, near Bellevue, Idaho, when a Cessna T210N crashed in night visual conditions while manoeuvring to land. The solo pilot was killed.
After informing the local controller that he was going to perform a 360° turn to "lose altitude if that's okay," and being cleared to land, there were no further communications. The Cessna's wreckage was located 307 ft below the summit of a mountain 6 NM southeast of the destination airport. The airplane had impacted on a south-westerly heading in a slightly right-wing-low, level attitude. The NTSB noted the mountainous terrain, high winds and the dark night in its finding of probable cause.
Another example of why there is increased risk of a CFIT accident at night occurred on December 22, 2003, in Missoula, Montana. After a night-time takeoff, two pilots flew a pressurized Beech Baron 58P into open terrain, with one of them suffering minor injuries. The aircraft was destroyed by a post-impact fire.
Shortly after taking off for the night flight in IMC, the flying pilot-who had no previous flight time in this make and model-made a right turn from the runway heading at about 400 to 500 ft AGL to join the departure procedure. During the turn, a "thump" was felt and the right bank angle increased from about 25° to 45°. While the second pilot was attempting to correct the increased bank angle, the aircraft entered a descent. Just before hitting open terrain one mile south of the runway, the PIC [pilot-in-command] took control and levelled the wings. The aircraft skipped across open terrain for several hundred yards before coming to rest on its belly. Neither pilot could recall scanning the instruments to verify a climb or descent.
Predictably, the NTSB determined the accident's probable cause to include the second pilot's failure to maintain terrain clearance while manoeuvring after takeoff. Additionally, the Board gigged the PIC for inadequate supervision and noted the night-time conditions.
It's likely that neither of these two CFIT accidents would have happened in daylight, since it would have been easier for the crews to see and avoid the terrain. But if you choose to fly at night, especially in the mountains or away from well-lit areas, extra precautions must be taken to identify and avoid potential hazards that you just can't see.
Of course, proper planning and exercising additional cautions are not the only keys to successful night-time flight operations. To identify and avoid those potential hazards, we must also understand and compensate for the tricks our eyes can play at night.
The eye's physiology creates several limitations on our ability to visually acquire objects at night. Perhaps first and foremost is the eye's requirement to become accustomed to low light levels. Bright cockpit lighting can drastically impair our ability to see lighted objects outside the aircraft.
Other darkness-related visual limitations include autokinesis (stationary objects appear to move), the so-called "Purkinje Shift" (certain colors are perceived differently) and the need to compensate for the eye's natural night-time blind spot by using our peripheral vision. Understanding and compensating for these unavoidable dark-light vision limitations can make our night flying experience much safer.
Flying between sunset and sunrise can be especially enjoyable, if pilots understand and are prepared for the differences with which they must contend to ensure safe operations. Identifying and avoiding obstacles and terrain while compensating for the eye's physiology are key. So is ensuring the airplane is properly equipped and that the proposed flight doesn't present any additional challenges because of darkness. If it does, it's your responsibility to determine if the additional risks are worth it and whether they can be properly managed.
Pay attention to the details at your departure and destination airports, ensure you have sufficient altitude to clear obstacles and terrain, and do some "what-if" planning to avoid that inevitable bump in the night.
Copyright 2005 Aviation Safety. Reprinted with permission, Belvoir Media Group, LLC. For subscription and other information, call 1 800 424-7887 or visit http://www.aviationsafetymagazine.com/.
Night VFR Video Black Holes and Little Grey Cells-Spatial Disorientation During NVFR
We would like to remind our audience of the availability of our excellent aviation safety video on night visual flight rules (NVFR) operations. The 10-minute video is called Black Holes and Little Grey Cells-Spatial Disorientation During NVFR (TP 13838E). It addresses NVFR, black hole illusion, somatogravic illusion and other traps and challenges facing pilots flying VFR at night. The video also contains some recommended procedures and practices that will assist pilots in making their night VFR flights as safe as possible. This video and the poster depicted above are also included in the System Safety Summer Briefing Kit, which is described on page 38 of this issue of the ASL. The video is available individually for loan from your Regional System Safety Office, or can be purchased from the new Transport Canada Transact Web site at www.tc.gc.ca/transact, or by calling the Civil Aviation Communications Center
at 1 800 305-2059.
A good landing is one that you can walk away from.
A great landing is one where you can use the aircraft again.
On 18 December 2000, the crew of an Antonov 124 conducted an instrument landing system (ILS) approach to Runway 25 at the Windsor, Ont., airport. Because of the weather minima on Runway 07, the aircraft was landed with a 4-kt tailwind component. The aircraft was about 20 ft higher, and about 6 kt faster, than recommended when it crossed the threshold of Runway 25. Consequently, the aircraft touched down well beyond the normal touchdown point (3 400 ft from the threshold). The runway was covered with a trace of loose snow, which reduced braking friction and lengthened the landing roll. Finally, the aircraft could not be stopped, and overran approximately 340 ft past the end of the runway. There were no injuries, and the aircraft sustained minor damage. Source: TSB Report Number A00O0279.
Antonov 124 overrun at the Windsor, Ont., airport, 18 December 2000
Each day, thousands of landings are made worldwide. Most aircraft land on runways that are longer than the minimum required length. However, each year there are occurrences reported in which the aircraft could not be stopped on the runway during landing. These occurrences are known as overruns. Many of these overruns are classified as minor incidents, as they do not result in significant damage to the aircraft or injuries to the occupants. However, when the aircraft enters a ditch, an embankment, or collides with an obstacle, the result of the overrun can be more dramatic. This is clearly illustrated by the landing overrun accident with an Airbus A340 that occurred recently at the Lester B. Pearson International Airport in Toronto, Ont. Unfortunately, there are many more examples like this accident.
Why do aircraft overrun? In order to answer this question, it is worthwhile to consider how a landing should be conducted (at least according to the textbook). In short, a "good" landing has the following characteristics: it starts with a stabilized approach on speed, in trim and on glide path; during the approach, the aircraft is positioned to land in the touchdown zone; when the aircraft crosses the threshold, it is at the correct height, speed and glide slope; the approach ends in a flare without any rapid control column movements, which is followed by a positive touchdown without floating; and immediately after touchdown of the main gear, the spoilers (if available) are raised (manually or automatically), the brakes are applied (manually or automatically), the reverse thrust or propeller reverse is selected (if available), and the nose is lowered. These actions are all conducted without delay and according to the standard operating procedures (SOP). This is the landing as it can be found in flight crew training manuals. Of course, not many landings are conducted exactly like this every day. Deviations from this practice often occur without any serious consequences. However, when there are large deviations from the "good" practice, it can become more difficult to stop the aircraft on the runway.
In 2005, a study was conducted by the National Aerospace Laboratory NLR, with the objective of identifying and quantifying the factors that increase the probability of a landing overrun. For this purpose, 400 landing overrun accidents that occurred with commercial transport aircraft were analyzed. This study revealed some interesting facts, which will be briefly discussed here. The study showed that if the landing was long (e.g. the aircraft contacted the runway far beyond the threshold), the landing overrun accident risk was 55 times greater than when it was not long. There are various reasons for a long landing. The touchdown should follow immediately upon the completion of the flare. However, the aircraft often floats for some time before touchdown. If floating occurs, the pilot often (but not always) tries to bleed off the excess speed. This action takes a significant part of the amount of runway remaining to stop the aircraft. The effect of the excess speed on the ground roll distance is usually less than the increase of the flare distance due to floating. This is explained by the fact that the deceleration of the aircraft during the flare is only a fraction of what can be achieved during braking on the ground, even on slippery runways. Therefore, it is important to put the aircraft down with excess speed, instead of bleeding it off in the air.
Ground effect also appears to play an important role in the floating of an aircraft. Ground effect is the aerodynamic influence of the ground on the flow around an aircraft. It increases the lift, reduces the aerodynamic drag, and generates a nose-down pitching moment as the ground is approached. The nature and magnitude of ground effect are strongly affected by the aircraft configuration. Ground effect provides a landing cushion that feels very comfortable to the pilot. This could explain, to some extent, the influence of ground effect on the tendency to float.
Runway surface conditions have been an important factor in landing overruns. The NLR study showed that the landing overrun accident risk increases by a factor of 10 when the landing was conducted on a wet or flooded runway, and by a factor of 14 when the runway was covered with snow, ice or slush.
A fact revealed by the NLR study that is of concern, is that in 15% of the 400 landing overrun accidents that were analyzed, there was late, or no, application of the available stopping devices. In many of these accidents, an overrun was avoidable if the available stopping devices had been properly used. The problems were mainly caused by the fact that the ground spoilers were not armed. In these cases, the pilots often failed to notice that the spoilers did not deploy. Also, late or no application of thrust reversers was often found in the accidents. In some cases, reverse thrust was selected initially; however, shortly afterwards it was deselected again. The NLR study revealed many more interesting facts about landing overruns. Readers are encouraged to have a close look at the report on the NLR study (see reference at the end).
Example of an overrun that didn't become an accident due to a soft arrestor bed.
An interesting technology that is worth mentioning here, is the application of a ground arrestor system, which is located beyond the end of the runway and centred on the extended runway centreline. A ground arrestor system is designed to stop an overrunning aircraft by exerting deceleration forces on its landing gear. Although this technology (as will be explained later) cannot prevent overruns from happening, its application can mean the difference between an accident and a minor incident. Different types of ground arrestor systems for civil application were studied in the United Kingdom in the 1970s, and later in the United States. An example of a ground arrestor system is the engineered material arresting system (EMAS), which is a so-called soft ground arrestor. A soft ground arrestor system like EMAS deforms under the weight of an aircraft tire that runs over it. As the tires crush the material, the drag forces decelerate the aircraft, bringing it to a safe stop. In recent years, EMAS became popular in the United States at airports that have difficulties complying with the rules on runway safety areas defined by the Federal Aviation Administration (FAA). There have been at least three reported overruns in which EMAS stopped the aircraft. These occurrences took place in the United States with a Saab 340 (May 1999), a MD11 (May 2003), and most recently, with a B747 (January 2005). Clearly, no soft ground arrestor system can prevent overruns from happening; however, it seems evident that such a system can affect the consequences. Other arrestor systems were also studied in the past. Examples are loose gravel, water ponds, and arrestor cables. Application of these systems to commercial airports has been limited.
In the unlikely event that you do run out of runway, let us hope that you do not run out of luck!
Van Es, G.W.H., Running Out of Runway: Analysis of 35 Years of Landing Overrun Accidents, National Aerospace Laboratory NLR, Technical Paper TP-2005-498, 2005.
As a result of recent accidents involving ground icing conditions and small aircraft, co-operative work on a computer-based training (CBT) project between Transport Canada, the Federal Aviation Administration (FAA), the National Aeronautics and Space Administration (NASA), the UK Civil Aviation Authority (CAA), and various air operators commenced in early January 2005.
This CBT addresses training needs for professional/corporate pilots of General Aviation type aircraft, as well as small cargo operators. The CBT program can be accessed from the NASA Web site, where you can download it and subsequently run it on your Web browser at your convenience. To download this program, visit the NASA Web site at: http://aircrafticing.grc.nasa.gov/courses.html.
An investigation conducted by the Transportation Safety Board of Canada (TSB) on the risk of two aircraft colliding in class D airspace showed the need to update pilot knowledge.
The management of air traffic in class D airspace is often misunderstood by aircraft pilots flying in accordance with instrument flight rules (IFR) or visual flight rules (VFR).
The article published in Aviation Safety Letter 4/2004, regarding the management of collision risk in class G airspace, analyzes the system, the management of risks and defensive barriers that assist in avoiding aircraft collisions. It is also an excellent tool to help remember the classification of airspace.
A fundamental principle applies to flying aircraft:
- Aviate: control the flight to reach the desired goals.
- Navigate: know your position, plan in accordance with the tools available and the type of flight (VFR/IFR).
- Communicate: exchange necessary information with the air navigation services and the pilots of other aircraft involved.
Communication consists of sending messages between a transmitter and a receiver through signs and signals. The following is a list of communication tools and their effectiveness:
- Verbal language (words) 7%;
- Paralanguage (tone of voice, volume, etc.) 38%;
- Non-verbal language (body language, hand signals, etc.) 55%.
It is evident that the tools available to pilots and controllers are limited to 45%, which emphasises the importance of each word.
To ensure the safety of a flight in a complex environment, the pilot must plan, act, monitor, and re-evaluate to see if the goals to be reached are the same as they were to begin with. Low-level controlled airspace can be complex and contain the following elements:
- Low level airways;
- Terminal control area;
- Extensions of a control area;
- Control zone;
- Transition area;
- Military terminal control area.
The Québec terminal area is an example:
The area of class D airspace around Québec has a complex, stacked shape, that is limited to the north by a restricted area. Arrivals from and departures towards the west are almost in a straight line with the Québec VHF omnidirectional range (YQB VOR), which is also where several airways cross. To the south, there is a training area with heavy traffic.
Class D airspace
Both IFR and VFR flights are permitted in class D airspace. VFR flights must establish two-way communication with the appropriate ATC unit prior to entering this type of airspace.
ATC ensures the separation of IFR flights and provides other aircraft with traffic information.
If equipment and workload permit, ATC will provide a conflict resolution advisory between VFR and IFR aircraft and, upon request, between VFR aircraft.
All pilots who undertake a flight in class D airspace must ensure that:
- the aircraft is equipped with:
- radio equipment capable of two-way communications with the appropriate ATC unit, and
- a mode C transponder, when the class D airspace is classified as transponder airspace; and
- a flight crew member keeps a continuous listening watch on a radio frequency assigned by an ATC unit.
Certain conditions concerning aircraft that are not equipped with this equipment may apply (see RAC 2.8.4 in the Transport Canada Aeronautical Information Manual).
Unless stated otherwise, you must ensure separation with other aircraft on your own. Planning for both departure and arrival are essential because it will allow pilots to develop a pace of work that corresponds to their experience, their skills, and the weather conditions. Up-to-date reference documentation (Canada Flight Supplement) is essential for operation in complex airspaces. The consistent use of a mode C transponder will help ATC, and provide a traffic advisory (TA) or a resolution advisory (RA) to aircraft equipped with a traffic alert and collision avoidance system (TCAS). A specific transponder code may be assigned by ATC.
ATC provides separation between IFR flights and provides information regarding VFR flights, which requires pilots to be continuously vigilant. It is important to be seen and to use all systems available to make your aircraft visible to others. It often seems easier for an IFR pilot to enter complex controlled airspace and feel protected because ATC provides separation from all other aircraft, but this is not always the case. The high workload on performance aircraft during arrivals and departures, and familiarity with tasks to be completed, may result in the crew being less vigilant of VFR aircraft.
The ATC unit
The ATC unit provides air traffic control, in order to prevent collisions and boost the traffic.
Several factors may influence the controller's work, such as the workload, traffic volume, multiple communications or lack of communication, and available equipment. Effective communication will allow a situation to be represented the same way from both perspectives. Ambiguous situations must be clarified and not tolerated.
Remember that it is your responsibility to plan your flight, establish effective communication with ATC, and maintain an active listening watch. Due to the complexity of airspace, pilots are required to have a good knowledge of the regulations and operational standards applicable to the class of airspace.
On April 7, 2003, at approximately 09:10 Eastern Daylight Time (EDT), a Found Aircraft Canada Inc. FBA-2C1 Bush Hawk XP aircraft took off from a cleared ice strip, that was approximately 1 600 ft long and 50ft wide, on the frozen surface of Lake Temagami, 20 km southwest of the town of Temagami, Ont. The ice strip was adjacent to the pilot's residence.
At 08:00 that morning, the pilot had taxied the aircraft to the rear of his residence for pre-flight preparation and refuelling. He returned the aircraft to the front of his residence sometime before 08:30, where it remained until about 09:00. At that time, the pilot and one passenger, who was also a licensed pilot, boarded the aircraft for a visual flight rules (VFR) flight to Parry Sound, Ont.
The aircraft lifted off approximately halfway down the strip, climbed on runway heading to 200–300 ft above the lake surface, then commenced an approximately 30° bank turn to the left. After the aircraft had turned approximately 120°, the aircraft rolled about 90° to the left, the nose dropped, and the aircraft stalled and entered an incipient spin to the left. The spin stopped after about one turn, and the aircraft then rotated briefly in the opposite direction and struck the frozen lake surface in a nearvertical attitude. The accident occurred at approximately 09:10 EDT. The aircraft was destroyed on impact and both occupants were fatally injured.
On the Sunday night before the accident, the weather was clear with an overnight temperature of -20°C and reports of overnight frost. The weather remained clear and, based on reports from a nearby airport, the temperature rose to between -15°C and -10°C by the time of the accident. Upon investigation, ladders and brooms, which the pilot was known to have used on other occasions to sweep snow and frost off the aircraft, were found at the rear of his residence, in the pre-flight preparation area. No de-icing fluids were found. Based on observation two days after the accident, direct sunlight did not reach the spot where the aircraft had been parked until 09:00 and would not have melted any frost that was present.
The TSB makes note of a recent U.S. National Transportation Safety Board (NTSB) advisory that suggests that even "imperceptible" amounts of frost can have catastrophic effects. The NTSB expressed concern that pilots may not be aware that small amounts of frost on an aircraft can have as serious an effect on performance as larger and more visible amounts of ice accumulation.
Findings as to causes and contributing factors
The TSB investigation determined that frost on the aircraft's wing adversely affected its performance, resulting in the aircraft stalling at higher-than-normal airspeed and entering a spin without warning. The single-engine plane had just taken off; as a result, it was too low to permit recovery. In its report, the TSB describes how the pilot may not have noticed the aircraft slowing down because he was making a low-altitude turn and picking up a stronger tailwind. This situation created the illusion of travelling at faster-than-actual speeds. The frost also reduced the aircraft's stability. These two factors negated usual cues that would have alerted the pilot to the slower speed.
The full report on this and other TSB investigations is available on the Internet at: http://www.tsb.gc.ca/, or via the TSB electronic subscription service.
Most passengers have experienced turbulence-a choppy, bumpy sensation when an aircraft travels through a rough air pocket. Turbulence can be created by a number of different conditions, including atmospheric pressures, cold or warm fronts, thunderstorms, jet streams or mountain waves. The effects of turbulence on aircraft vary in intensity, with light turbulence being a mere inconvenience to travelers. However, many passengers do not realize that turbulence may occur suddenly, and without warning, and that severe turbulence can have disastrous consequences.
In non-fatal accidents, in-flight turbulence is the leading cause of injuries to passengers and flight attendants. Injuries are most common to those not wearing a seat belt. Flight attendant duties, such as cabin checks and securing galley equipment, put them at a greater risk for injury. In some cases of severe turbulence, unsecured passengers and flight attendants have experienced fatal head and neck injuries as a result of being thrown about the cabin.
The Canadian Aviation Regulations (CARs) require passengers and crew members to be seated with seat belts fastened:
- during aircraft movement on the ground, during takeoff/landing, and during turbulence;
- when directed to do so by the pilot-in-command; and
- when an in-charge flight attendant is carried, and they direct the use of seat belts when turbulence is encountered.
The CARs do not require mandatory use of seat belts during all phases of flight-such a policy would be impracticable and difficult to enforce. Thus, Transport Canada encourages air operators to take initiatives promoting passenger-use of seat belts at all times during flight. The message that must be conveyed to passengers is that the best protection against unexpected-turbulence related injuries is to remain belted at all times. Communicating this message creates a spirit of cooperation with passengers in preventing such injuries from occurring.
More specifically, Transport Canada encourages seat belt use with a number of recommendations. First, when the seat belt sign is initially turned off during flight, an announcement should be made from the flight deck explaining the hazards associated with not wearing a seat belt, and the importance of keeping seat belts fastened at all times. Second, air operators should discourage the practice of unnecessary illumination of the seat belt sign; in other words, the seat belt sign should be illuminated only during taxi, takeoff, landing and turbulence. Once the threat of turbulence has expired, an announcement should be made to passengers that they keep their seat belts fastened to prevent injuries from unexpected turbulence.
Finally, air operators should encourage their crew members to be proactive in promoting seat belt use, and to lead by example by keeping their restraint devices fastened when seated, even when the seat belt sign is not illuminated.
As injuries to secured passengers are far less likely than to those who are not secured, Transport Canada supports the initiative of any air operator who promotes the use of seat belts throughout flight.
For more information, please refer to Commercial and Business Aviation Advisory Circulars (CBAACs) No. 149-Seat Belt Use &Seat Belt Discipline and No. 0070R-In-Flight Use Of Seat Belts/Safety Harness-Flight Attendants.
Flying is a discipline...
safety is an attitude.
- Date modified: