- Back To Basics: Taking Takeoffs and Landings to the Max
- Flight Training-Could You or Your Students Run Out of Fuel?
- Timely Selection of Pneumatic De-icing Equipment and Inadvertent Selection of Inappropriate Automatic Flight Control System (AFCS) Climb Mode
- "Labrador Tea-Brush" Punctures Bell 212 Belly, Fuel Cell
- Collision Avoidance
Back To Basics: Taking Takeoffs and Landings to the Max
by Cordell Akin
Taken from www.swaviator.com/html/issueON99/backbasics.html
This article is an authorized reprint from the October/November 1999 issue of Southwest Aviator Magazine. This and many other excellent safety articles can be found on their Web site at http://www.swaviator.com/.
Just thinking about it is pure enjoyment. You fly into a remote airstrip in the mountains of the Southwest in your own airplane and pitch a tent beside a stream. The trout are hungry. You laze away a few days under a turquoise sky with a warm summer breeze singing through endless stands of pine trees. Or perhaps you'd prefer to pitch that tent in a meadow surrounded by golden aspen trees and set out to track the huge bull elk. Either option appeals to me, but the most interesting part is exercising the skill required to fly into and out of a challenging remote airstrip.
The very geographical nature of the Southwest invites pilots to visit short, high, sloping, dirt or grass airstrips or airports with obstacles in the approach and departure path. Anyone flying their birds to such perches should become well practiced in the area of maximum performance manoeuvres. You remember what they are from training days: short field and soft field takeoffs and landings. If you stay sharp on these manoeuvres, your passengers may not talk about you like they did the pilot in the following story.
After a successful hunting trip, a pilot who was flying passengers for the second year in a row loaded three 200-lbs hunters and the entire elk in a four place airplane and departed from a short airstrip. They all survived the crash right after takeoff, and one hunter said to another, "You know, Zeke, we sure have a skilled pilot. This is only 100 yd from where we crashed last year."
The short field departure with obstacles
Most short, unpaved airstrips will not have a taxiway, so you must back taxi the take-off runway and turn around, wasting as little runway as possible. Be careful when making the turn that your aircraft's tail does not strike something at the end of the runway (e.g. a stump). We're talking real bush here.
Straighten the nose wheel, hold the brakes and apply full power. If the strip is at high altitude, lean the mixture at full power to get maximum performance from the engine. Before releasing the brakes, check all the engine instruments for normal readings and normal power. Be ready to abort the takeoff if anything appears, sounds, or feels abnormal.
Hold the aircraft on the ground until Vx (best angle of climb) speed is reached. Rotate and maintain Vx until the obstacle is cleared, then increase speed to Vy (best rate of climb). As the aircraft leaves ground effect, and induced drag (drag resulting from the production of lift) increases, the initial pitch angle of the nose will need to be lowered slightly to maintain Vx. You must not give in to the urge to lift the nose prematurely when you see trees coming closer at an alarming rate. If the situation is tight, the speed you need is Vx, because it will give you the best climb over obstacles.
So, if you practice short field takeoffs, you can depart from an airstrip whenever you want, right? Wrong. Sometimes the density altitude will not allow the clearance of obstacles no matter how good your technique. It will help to plan your takeoff in the early morning when the temperature and density altitude is lower. If possible, always take off downhill and avoid tailwinds. Ground roll will be increased about 10 percent for each two knots of tailwind.
It is a good idea to increase all pilot operating handbook (POH) figures for 50-ft obstacle clearance by 25 percent in order to take into account engine hours, extra parasite drag from the addition of antennas or the removal of wheel farings, and your own skill level. Keep in mind that published obstacle clearance distances do not take into consideration the real world realities of turbulence and downdrafts. These could place you in the position of looking squarely into the face of a knothole halfway up a tree on takeoff. If the situation is truly marginal, do a pattern with just yourself on board. Then, add passengers one at a time in successive patterns to see how the aircraft performs under the actual conditions.
Aerial view of Hawkesbury East Airfield, a typical short, grass airfield. Photo courtesy of COPA.
Short field arrivals
Clearing the trees on takeoff will be a moot question if you run off the end of the runway on arrival. Of course, it could extend your vacation while you try figuring out a way to get back home.
There is a reason why the practical test standards for private pilot stipulate that the aircraft must touch down within 200 ft of a selected point. On a short field arrival, you want to touch down as close to the beginning of the runway as possible. The key to doing this involves both pitch and power. Once established on final approach with full flaps, pitch the aircraft to achieve the short field airspeed given in the POH. Next, reduce power until the aircraft begins to sink, then increase power just to hold a straight glide path to the beginning of the runway (assuming no obstacles).
With this approach, when power is reduced, the aircraft will sink. When power is added, the sink will stop. This makes possible an accurate straight-line descent to the aiming point in the windscreen. The most common mistake pilots make is to leave in too much power and get high on the approach. Then, even though power is reduced to idle and the proper airspeed maintained, the landing point is exceeded by a good distance.
At the short field approach airspeed and just enough power to hold the glide path, reduce power to idle just before the intended touchdown point and there will be no speed left to cause float down the runway. Allow the main wheels to contact the surface in a modified flare so that maximum braking can begin as soon as possible.
A good short field landing will not be a greaser, but a firm touchdown-the opposite of a soft field landing. It is not necessary to retract the flaps immediately after landing, since the drag they produce is more beneficial than retracting them to put the weight on the wheels. On a rough, short strip, the wheels are going to be bouncing without a lot of braking action initially. The drag of flaps will help slow the aircraft.
Soft field departures
It has been said that if it takes full power to taxi, you have either forgotten to remove the chocks or the tail is still tied down. I would like to add one more situation to that. One time I landed on a dirt airstrip after a heavy rain in a pressurized 210. Slowing to taxi speed occurred very quickly and then it took full power to taxi in the red mud-with about 2 in. of it on all the wheels.
A soft field takeoff starts with the taxi. The control wheel should be full back to allow the propeller slipstream to increase down pressure on the elevator and lighten the nose wheel. During taxi and takeoff in soft conditions, the nose wheel must be protected. If the nose wheel happens to be on the rear of the plane, the soft field task is easier.
Refer to the POH for your aircraft regarding flap setting for a soft field takeoff. It will be 10 degrees on some light aircraft. This flap setting allows enough lift in relation to drag to get the aircraft in the air in ground effect as quickly as possible, allowing the weight to be shifted from the wheels to the wings. When full power is applied with the control wheel full back, the nose will initially rise higher than needed. At that point, reduce the back pressure just enough to keep the nose wheel off the muddy surface. With the wings in this high angle of attack position, the aircraft will lift off into ground effect at an airspeed too slow to sustain flight above ground effect. Therefore, once lift-off occurs, a slow but positive forward pressure must be applied to the control wheel in order for the aircraft to level out in ground effect and accelerate to Vx before trying to climb. The flaps can be retracted once the aircraft is climbing.
Ground effect occurs within one wingspan of the runway, increasing closer to the runway. It is the result of the runway surface interfering with the wingtip vortices and the average relative wind around the aircraft that produces induced drag. The reduction of drag in ground effect is quite pronounced, being about 25 percent at one-forth of the wingspan above the runway.
Soft field arrivals
If the airstrip is soft, touchdown must be made softly on the main wheels and the control wheel held full back to protect the nose wheel. I once landed on a soft grass strip and held the nose off as long as possible as the aircraft rapidly slowed. When the nose wheel finally touched down at a slow speed, it sank into the soft dirt halfway up the tire. There was no damage, but the aircraft had to be pushed by hand to firmer ground.
Assuming there arc no obstacles in the approach path, a soft field landing is normally made with half flaps and a normal approach speed. Half flaps work better than full flaps in most cases due to the fact that the pitch change in the flare is less pronounced because the approach angle is not as steep. The most consistently soft landings can be made if the power is reduced to slightly more than idle on short final and left there until the wheels touch. The throttle may then be reduced to idle. In an actual soft field situation, the power may be increased after touchdown to keep the nose wheel elevated until firmer ground is reached.
It is important to keep raising the nose in the flare to hold the wheels off the runway as long as possible with the stall warning horn activated. Once the main wheels touch, maintain full back pressure to keep the nose wheel off the surface until it falls by itself, then continue the back pressure until the taxi is completed.
Whether or not you ever fly into a remote airstrip in the Southwest with that fishing rod or hunting rifle, staying proficient in maximum performance takeoffs and landings will make you a better pilot. Besides, the airplane tires, landing gear and airframe will benefit from constant softer field landings, even those you make with full flaps. And, by the way, your self esteem will also benefit when your passengers tell you what a great pilot you are.
Cordell Akin is a certified flight instructor-instrument (CFII), multi-engine instructor (MEI) with a total of 10 000 hr and 3 000 hr as a flight instructor. He spent 15 years in East Africa flying a C-185 and a P-210. He is the owner of Akin Air at Coronado Airport in Albuquerque, New Mexico.
How could it happen? It couldn't possibly happen to one of my students. No way it could ever happen to me...or could it?
Why do pilots of various experience levels, including instructors, run out of fuel?
We've learned some things from following up on fuel starvation occurrences that are worth sharing. There is a common thread-well, more like a rope-it's a lack of understanding.
This makes sense when you think about it. Obviously, if someone planned a trip properly and determined they were going to run out of fuel, they'd make a change, right? Perhaps take more fuel or make an intermediate stop, something, anything. The more likely explanation is that errors are made. Errors in planning, errors in judgment, pilots unknowingly make changes en route that result in higher fuel consumption rates than planned, or sometimes they don't plan at all. Also, it's difficult to pin down exactly how much fuel will be consumed on a training flight. There's no accurate information to rely on, making it guesswork at best.
It is interesting to note that pilots often don't see it coming, right to the end. One pilot told us he thought he had carb ice or some other engine problem when it happened to him. He didn't even suspect fuel starvation as the cause of his engine failure.
Another interesting point is that in some cases, pilots didn't take much or any extra fuel. Why not? Maybe it's because some call it "granny" fuel. One pilot told us he was late leaving on his cross-country and wanted to save some time, so he didn't add fuel. In his case, he already had pretty much the exact amount of fuel he calculated he would need on board. His calculations were off, and yes he crashed. Fuel planning is far from an exact science. As pilots advance and fly things around like people or freight, the luxury of taking extra fuel is pretty much history. It's hard to tell your boss you're leaving a few passengers or some freight behind so you can take some fuel you probably won't need. Why not enjoy that luxury now? Sometimes things are just plain missed. We know trainees can make mistakes, that's the business we're in. Why not teach them to have some extra "go" juice in their back pocket if they can take it?
The truth is, it could happen to your trainee. It could happen to you. It could happen to anybody, and it has. This may be another part of the problem. It just seems like such an unlikely thing that some pilots may not take it seriously enough. Vigilance is a factor. Never assume anything. Remember, in aviation, assumption is the mother of emergency.
Let's take a closer look at some of the seemingly minor common errors that stack up to steal fuel from us.
How much fuel do we need to make the trip?
Did we include fuel to start, taxi, run-up, take off and climb? Some pilot operating handbooks (POH) give us some of this information, some don't. It should be considered.
Are we going to get the consumption rate the POH says we will?
I think pretty much everybody will agree that we won't. Remember, the POH values are for a new airplane, at a specific altitude, at a constant power setting, with a certain mixture leaning procedure and a specific fuel grade. The rate is low even for those parameters because low fuel consumption is a selling point for manufacturers. They're going to print the lowest values they got in testing. If you're conducting a training flight, you really don't know what your consumption rate will be. It could be considerably higher than the POH values. Values up to 170 percent of the POH cross-country consumption rates are possible, depending on what you're doing with the airplane. That means if you calculate 5.0 gallons per hour (gph), you might actually be up around 8.5 gph on training flight.
How much fuel was on board when we left?
Who checked the fuel quantity-you or your trainee? Was it an accurate measurement? Do you occasionally confirm what they tell you? Was the aircraft on level ground? Are the dipsticks properly calibrated against a meter and for that specific aircraft? Was the quantity rounded up to half-tanks or three-quarter-tanks? It's better to work with the number of gallons instead.
Is our cross-country en-route time accurate?
Maybe not. Forecasting of upper winds has become fairly accurate but you may get there sooner or later than planned. The key is to get there. Fuel must be closely monitored en route; not on gauges alone, but based on how many gallons you had on departure, your consumption rate, and your actual time en route. You know, some of the other not-so-accurate stuff we've already talked about!
Have you discussed fuel consumption performance penalties with your trainee?
Does your trainee understand the increase in fuel consumption rates encountered with changes in altitude, mixture-rich instead of lean, making a diversion to look at something, doing some practice precautionary procedures or forced approaches?
The amount of fuel we think we need when we plan the flight may not be accurate. The amount of fuel we have on board for the flight may not have been measured accurately. The amount of fuel we're consuming en route is difficult to calculate accurately. The amount of fuel remaining is tough to figure out, too. We all know fuel gauges are not incredibly accurate. If all of these things conspire against us, we may be in trouble.
What if a trainee decides on a lower altitude or leaning the mixture has always been kind of scary, so they don't? What if they want to take a look at something, or fly over a friend's place? How about throwing in a practice precautionary, forced approach or diversion, wouldn't that make my instructor happy? What if they get lost for a little while? Do they really understand the fuel consumption penalties they would suffer? It's difficult to know even for experienced pilots.
What's the answer?
The answer is knowledge. The answer is vigilance. And, oh yeah, since things are not accurate, take more fuel than you think you need. Remember, you can take more fuel than you need, what a luxury! What an example to set for your students. Ever notice that experienced pilots seem to do things that give them a large margin of safety whenever they can? There's no shame in it, nobody can plan for every possible scenario, but you can set yourself up so you have options and see things coming. Teach that attitude to your students, and remember-grannies live for a long time.
Timely Selection of Pneumatic De-icing Equipment and Inadvertent Selection of Inappropriate Automatic Flight Control System (AFCS) Climb Mode
This article is in response to two recent Aviation Safety Advisories from the Transportation Safety Board of Canada (TSB).
On May 27, 2005, a de Havilland DHC-8-100 (Dash 8) was on a flight from St. John's, N.L., to Deer Lake, N.L., with 36 passengers and 3 crew on board. During the climb out from St. John's, the indicated airspeed began a gradual and undetected decrease to the point that the aircraft departed controlled flight. The aircraft descended rapidly, out of control, losing 4 400 ft before recovery was effected, approximately 41 seconds later. The aircraft was operating in icing conditions1 when the loss of control occurred; however, the extent to which airframe icing contributed to this occurrence has not yet been established. The TSB investigation into the causes and contributing factors of this occurrence is on-going (TSB file A05A0059).
Dash 8 operating instructions state that, when operating in icing conditions, engine intake by-pass doors must be open, engine ignition switches must be set at manual, and airframe de-ice must be set to slow or fast. The crew was aware of the possibility of ice, was watching for its formation, and had selected the engine by-pass doors to open. The anti-ice system was on, with the ignition switches set to manual. The airframe de-ice system remained off.
For many years, the accepted practice in the aviation community was to wait until a significant amount of ice built up prior to activating airframe de-icing equipment to prevent "ice bridging."The Dash 8 aircraft flight manual (AFM) reflects current norms of selecting all anti-ice systems "on" immediately when entering icing conditions. In the course of the investigation, it became apparent that a number of pilots may still cling to the traditional practice of waiting, despite contrary instructions in the AFM. When contacted, FlightSafety Canada estimated that 50 percent of pilots, both Canadian and international, who attend their training sessions, still wait for ice to build up despite directions that may exist in AFMs to select de-icing equipment "on" immediately upon entering icing conditions.
Small amounts of ice may have unpredictable adverse effects, particularly if the aircraft is already operating near the stall speed. Since the occurrence, the operator has taken steps to ensure that pilots conform to published procedures for activation of pneumatic boots. Pilots are required by regulations to complete annual ice contamination training, and the occurrence crew had completed airborne icing training in March of 2005. However, it is apparent that old beliefs on the use of pneumatic boots are still prevalent. The TSB suggested that Transport Canada (TC) take additional action to ensure that pilots are informed and conform to published de-icing procedures, and dispel old beliefs about the use of pneumatic de-icing equipment.
TC agreed with the suggestion, and we therefore invite all pilots to read Commercial and Business Aviation Advisory Circular (CBAAC) 0147, issued on November 2, 1998, which can be found at http://www.tc.gc.ca/eng/civilaviation/standards/commerce-circulars-ac0147-1615.htm. This circular addresses airborne icing and the operational use of pneumatic de-icing boots. It also addresses the issue of "ice bridging" and recommends the procedure proposed in the TSB advisory unless specifically prohibited by the AFM.
For the benefit of our readers, here is the excerpt on "ice bridging" as found in CBAAC 0147:
Several generations of pilots operating aeroplanes with pneumatic de-icing boots have been cautioned against the dangers of ice bridging. Pilots were-and are-advised against activation of the pneumatic de-icing boots before sufficient ice has built up on the leading edge-generally between 1/4 and 1 inch-out of concern that the ice would form the shape of the inflated boot, resulting in the boot inflating and deflating under a shell of ice, making de-icing impossible. Despite the widespread belief in this phenomenon within the pilot community and its coverage in numerous technical publications, its existence cannot be substantiated, either technically or anecdotally. At a recent conference held in Cleveland [Ohio] to investigate ice bridging, the major manufacturers of pneumatic de-icing boots reported that they had been unable to reproduce ice bridging under any laboratory/wind tunnel conditions, and that any operational report of ice bridging investigated by them had been determined to be a report of residual ice."
Finally, CBAAC 130R, Revised Airborne Icing Training Guidance Material, directs operators to revise their training programs to incorporate the revised information on airborne icing issues.
Inadvertent selection of inappropriate automatic flight control system (AFCS) climb mode
In the same occurrence described above, the aircraft used a Sperry SPZ-8000 digital AFCS. A single flight guidance controller is used to select flight director modes of operation, and to engage/disengage the autopilot. Most of the controls on the AFCS controller are alternate-action pushbutton (push on, push off). There are two vertical modes available; when the "IAS" button is selected, the AFCS will command the aircraft's indicated airspeed at the time of selection, and when the "VS" button is selected, the aircraft's vertical speed at the time of selection. The selection of either of these two modes will remove the other one, if it was previously selected and active. The "IAS" and "VS" selection buttons are located next to each other on the flight guidance control panel. When the autopilot is engaged, it is driven by the flight director commands selected on the flight guidance controller panel.
The crew had engaged the autopilot during the initial stages of the climb. Normally, the aircraft is climbed using "IAS" mode. Flight data recorder information for the flight shows that, during the climb, the rate of climb remained constant at 1 190 ft/min, while the airspeed varied. This indicates that the AFCS was operating in the "VS" mode. Information gathered to date indicates that the crew had meant to select "IAS" mode, and were unaware that "VS" had been selected. The inadvertent selection of"VS" and the subsequent loss of airspeed was not detected by the crew.
The crew had recently completed DHC-8-100 conversion training at FlightSafety Canada. FlightSafety Canada's standard operating procedures (SOP) for the DHC-8-100 (page 10.4) for the climb state:
"The vertical speed (VS) mode should not be used for climb, since airspeed may decrease below that desired, as the FD (flight director) increases pitch attitude to maintain climb rate to compensate for decreasing engine power at higher altitudes."
To help guard against inadvertent selection of "VS" mode and subsequent low airspeed, FlightSafety Canada SOPs require a verbal challenge and response when the AFCS is engaged. Upon engaging the AFCS, the pilot flying calls out, "set IAS," along with the captured airspeed. The pilot monitoring confirms the selection of "IAS," and reads back the captured "IAS" value.
At the time of the occurrence, the operator's SOP for the climb phase did not restrict climbs in "VS" mode; however, it was common knowledge amongst company crews that "VS" mode was not to be used. The operator's SOPs also did not require a verbal challenge and response between crew members to ensure correct AFCS mode engagement. Since the occurrence, the operator has taken steps to modify their SOPs to ensure that the correct selection of AFCS mode is made. There arc other AFCSs that operate in a manner similar to the Sperry SPZ-8000. Selection of "VS" modes during climbs in these other systems could also have adverse effects.
At present, there is no requirement for operators to have an SOP detailing specific AFCS engagement procedures. Defences need to be put in place to prevent inadvertent or inappropriate selection of AFCS vertical and other commands by aircrew. As evidenced by this serious incident, an inadvertent selection of "VS" mode during climb could lead to an airspeed deterioration which, if not detected and corrected in time, could lead to a loss of control. Therefore, operators are strongly advised to incorporate appropriate measures into their SOPs to ensure the correct selection and monitoring of the AFCS modes of operation.
Tree stump with vegetation removed
Helicopter operations in the field often involve landing in remote, confined and obstructed areas. Pilots who land in totally unprepared areas have a certain routine about inspecting the intended site, and as such, will usually exercise a level of diligence appropriate to the situation. At other times, ground support personnel may have prepared a remote or improvised landing area, which can influence the level of diligence used by pilots when approaching the site.
An example of such a situation occurred on August 16, 2005, when a Bell 212 helicopter was landing on an improvised pad at Bonnie Lake, Ont., on a flight from a firefighting camp. The landing site had been prepared by trained ground personnel. As the aircraft was landing, it struck a tree stump, described as "Labrador tea-brush," which punctured the belly of the aircraft and the right main fuel cell. About 300 lbs of fuel was lost.
View of punctured helicopter fuselage
The stump should have been removed by the ground crew, but was not easily seen because of the vegetation. Since the site had been prepared by trained personnel, the pilot likely assumed that the landing site was free of hazards. As a result, the operator is reviewing its helipad construction training for ground personnel.
Collision Avoidance Tip: Use of landing lights. Pilots have confirmed that the use of landing lights when flying at the lower altitudes and within terminal areas, both during daylight hours and at night, greatly enhances the probablility of the aircraft being seen. A side benefit for improved safety is that birds seem to see aircraft showing lights in time to take avoidance action. Therefore, it is recommended that all aircraft show a landing light(s) during the take-off and landing phases, and when flying below 2 000 ft AGL within terminal areas and aerodrome traffic zones. (Ref.: TC AIM AIR 4.5)