Page b1 Takeoffs
Takeoffs
and Departures
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Contents:
…POH takeoff factors; …Takeoff Notes; …P-Factor...Takeoff to enroute procedures; ...Takeoffs are different from landings; …Takeoff Killers; ...Attitude; ...A proficient pilot can; ... The takeoff; ...Why takeoff pitch changes; ...Short Field Takeoff; ...Soft-Field Takeoff ; ...Downwind Takeoff; ...Short, Soft, and Rough Takeoff; ...Aborted Takeoff; ...Crosswind Takeoff; …Class C Mountain Departure; ...Close the Door; …
Many airports of the U.S. are long enough and wide enough for all G.A. aircraft. Oddly, most are not. When the runway has variations of length, obstacle clearance, surface texture, slope, and density altitude the pilot is called upon to do some combination of artistic and technical figuring. He must figure the foregoing variables into the POH as they apply along with the aircraft weight and balance. He must factor in his pilot skills and knowledge of technique which is, perhaps, the most unknown variable. An airplane can land in considerably less distance than it needs for takeoff. Pilots tend to over-estimate their skills. The POH is required reading.
Every takeoff is as unique as every landing. Every takeoff occurs in unique conditions. After landings, takeoffs are the most frequent source of accidents. The minimum safe runway takeoff length should be one and a half times that indicated by the POH. The extra 50% is required to cover pilot optimism. The first warm day of spring gives a completely different takeoff than those you have made all winter. Also, this takeoff will be different from the first 100-degree takeoff of summer. The hotter it is, the less pitch attitude recommended during acceleration.
For standard temperatures you should increase takeoff distances by 25% for each 1000 feet of elevation. Increase POH distances by 10% for every 25 degrees Fahrenheit above standard for any altitude. Every 2500' of increased elevation causes 10 degree standard reduction in temperature. If an airport at 2500' elevation is warmer than 70 degrees you have a density altitude situation.
Factors that make a difference have some rules of thumb that a pilot should know and perhaps reference on his lap board. For every 15 degrees F above standard temperature raises density altitude by 1000'. Every 2 knots of tailwind increases takeoff distance by 10%. A firm turf takeoff requires 7% more distance, short grass requires 10% more distance, and soft surface/tall grass requires 25% more distance than recommended by a POH for a macadam runway.
Most common takeoff mistake is using apparent ground speed to initiate an early rotation. Making a proper rotation using indicated airspeed may cause a pilot to pitch for a sea level climb. It is not unusual to find the aircraft a mile or two off the runway end after having mushed through the air that far without climbing.
Attempting to climb out of ground effect with insufficient airspeed is the problem you must be patient and prepared to stay in ground effect to gain airspeed. Any go-around decision must be made early in the approach will carefully controlled changes in configuration and airspeed.
By listening on the radio you can get insight into the ATC mind and prepare for such things as "taxi closer and hold, prepare for an immediate", "taxi into position and hold", etc. You must become aware as to what is occurring with other aircraft in the air and on other runways. The mental process required to execute a safe takeoff extend far beyond just moving the aircraft.
Consider:
1. Pretakeoff checklist/position Emergency list
2. Clearing the approach area both base and final
3. Configuration and yoke set for wind direction
4. What-if considerations such as power, aborting, emergency,
etc.
5. Vso speed for rotation and attitude for Vy climb
Check weight and balance
Density altitude 'begins' to make a difference at 2000' and 80
degrees F.
Keep the nose straight with rudder
Crosswinds require crosswind controls
Rotate sooner rather than later
Don't hesitate to abort a takeoff
The POH (Pilot Operations Handbook) has compiled the manufacturer's
experience with wind velocity and direction, flap configuration,
density altitude, runway surface, and slope to determine the performance
capability of the aircraft for a given weight to lift off and
overfly the FAA 50' obstacle. The POH has determined the flap
requirements, the rotation speed, tire inflation, and the climb
speed. If the surface is firm an over-inflated tire is preferred,
under inflation can increase required distances by 15%.
Many POH charts fail to provide for variables of runway surface, for this we must use 'rules of thumb' that provide safety margins. For grass runways increase lift-off distance by 20%. If the grass is long or damp add 50%. Slope of the runway and wind direction can be compounded by the slope and turn clearance area of the departure path. For specifics you must consult with the locals. Distances can be reduced by 5% for every 100 pounds below gross or POH weights. A 3000' runway becomes very short when temperatures exceed 80 degrees at 3000' elevation
In the aircraft POH there is reference data that show how the aircraft will perform under a variety of conditions. One of these conditions is going to be an appropriate fit for most any takeoff you will make. You should make a practice of referencing some of your takeoffs with the information contained in the POH. The more often you do this the least likely will you be a pilot who if found by the NTSB (National Transportation Safety Board) as not understanding takeoff data and responsible for improper decision-caking. The POH will have charts that cover the takeoff influence of weight, power, runway surface, wind and density altitude. Any one of these factors can alone or in combination cause a takeoff accident. The worst thing that can happen to a pilot is to get-away-with-it one time.
An overweight aircraft may be pitched too high during the takeoff roll. This pitch limits the ability of the aircraft to accelerate. The perception of attitude improving takeoff from previous flights or even a flight simulator may get you off the ground only to cease flying out of ground effect and stall to the surface. The pitch attitude puts the aircraft behind the power curve. The aircraft may fly off the runway but it will crash because once behind the power curve, you must lower the nose and lose altitude before gaining flying speed.
P-factor results when there is a differential in thrust between two propeller blades. This asymmetric disc loading of the blades moves the line of thrust from the axis of rotation. The result is adverse yaw which must be countered by rudder application. When the propeller blades differ in thrust there is a proportional decrease in total propeller performance.
Every time an aircraft rotates for takeoff or for landing flare the propeller has asymmetric loading of the propeller blades and the resulting adverse yaw. The higher the pitch angle or the power the greater need exists for rudder application to keep the nose straight. Some lack of climb performance is due to the inefficiency of the descending propeller blade.
TAKEOFF.....CLIMB .....LEVEL ......CHECKPOINT
Clear Rwy ......Airspeed ..1. Dive/trim .......Time
Configuration ...Trim ........2.Level/trim .......Heading check
Rotate Vso ....Alignment ..3. Accelerate ....Gauges
Alignment .......Gauges .....4. RPM ............Radios set
Gauges ...........CLEAR ....5. Fine trim .......ATA/ETA
Turn Alt ..........Turn ..........6. Gauges ........Alternate
What if... ..Altitude
The safest takeoff requires that maximum use of the runway be made. Anything other than a smooth rapid application of throttle is relatively unsafe. Most aircraft engines and carburetors are not designed for sudden applications of power. Rotation and liftoff should occur at minimum safe operating speed (bottom of the green arc) and climb trimmed for best rate. On takeoff, it is a good practice to have the student check his runway alignment between three and four hundred feet AGL. The first time a student does this he will unknowingly pull the yoke and cause dramatic attitude and airspeed changes. Emphasize that the aircraft must be correctly trimmed and the yoke released for the runway check. If parallel runways are in use it is well to teach a 10 degree divergence from runway heading as a safety measure.
An abrupt application of throttle can cause the carburetor to 'load up' from excess fuel and effectively 'choke' the engine. This can be traumatic on takeoff and dangerous on a go-around. Too slow an application of power wastes runway. With fixed propeller aircraft all takeoffs and climbs are done at full power. Oddly enough, the reason for this is engine cooling. At full power the last fraction of throttle movement opens an additional fuel jet in the carburetor. This additional fuel is beyond the operational requirement of the engine and serves to cool the cylinders and valves when air flow cooling is reduced in climb. Full power operations also raise the octane of the fuel used. 80/87 (red) fuel has the higher octane under full power operations. Sudden power changes are to be avoided.
A pilot is expected to used the maximum allowable power for every takeoff. You are not helping the engine or safety by using less than maximum power. A reduced power takeoff requires more time, runway and engine wear. The sudden acceleration often causes a student to over apply rudder control. Rudder should be applied only to straighten the nose to parallel on the center line with no effort to center on the runway. Light rudder control is best during the takeoff. The student must anticipate the right rudder required as the nose is raised off the runway. With the runway out of sight, the runway alignment is maintained by peripheral vision on the horizon or by reference to the left side.
On a takeoff, the pilot has only a few moments to make the go-no go decision on a less than 3000' runway. Every takeoff should have a pre-planned takeoff option of aborting, or continuing at a given point on the takeoff runway. Once airborne the pilot should have pre-planned off-airport landing options up to and including 700 feet. Above 700' you may have a shot at getting back to the airport but perhaps not back to the takeoff runway. A takeoff is a matter of technique and planning. Complacency is the pilot's greatest enemy.
No climb of any duration should proceed without clearing. Climb at best rate for safety and noise abatement. At an altitude of 600' (A Contra Costa County regulation) we may turn on the course requested. No turn should be made without clearing. As a procedural habit "Clear left-turn left" should orally precede every left turn. Likewise for right turns.
Takeoffs are different from landings
The actual condition of the aircraft for takeoff probably bears no relationship to the presumptions of the POH or AFM. There are entirely too many variables of surface, slope, wind, performance configuration, and pilot technique, to put into such a source. The takeoff distance on a runway is not just a matter of speed. It how soon over the distance that the speed is attained that is important. Takeoff distance is a function of speed squared. Once you have reached half the takeoff speed, you will need four times as much more distance to takeoff. A 10% increase in weight will require slightly over 20% more takeoff distance. Abort the takeoff if you can't acquire 75% of your takeoff speed before using half of the total distance.
Any wind will have a significant effect on the takeoff. A tailwind will double the takeoff distance. The same takeoff into the wind would have a 30% decrease in distance. The slope becomes significant only when it is above 5-degrees and a low powered aircraft. Expect about a 4% change in required distance for every one percent of slope. This is not very much change per degree of slope. Only 10 pounds per 1000 pounds of aircraft weight. an uphill takeoff will be easier to abort. A tail wind that increases in velocity as you climb will result in a lower slope gradient. Add at least 25% to any AFM performance requirements just for the aircraft and pilot capabilities that will differ from those when new at the factory.
Takeoff
Killers:
You should use a higher than normal liftoff speed in strong
wind/gusty conditions because of stall probability.
1. Configuration
2. Fuel-fullest/pump/pressure
3. Trim-indexed
4. Instruments
5. Speed-abort distance
6. Seats, belts, doors, windows
An engine failure on takeoff results in a few moments of incomprehension
while the pilot holds the climb attitude even though a climb does
not exist. No change in control pressure is required to bring
this effect. At some point the sink rate increases with an increase
in angle of attack because of a lower airspeed until the critical
angle brings about the stall. Only lowering the nose will break
the stall. Otherwise the nose will fall in the stall. Pilot input
can only increase the sink rate and airspeed. Achieving a minimum
sink rate at best glide speed is the best compromise of speed
for the most distance over the ground.
Second Opinion:
Vx gives you a benefit of getting over an obstacle... best climb
per distance, but overall, you will gain the best altitude per
time, which is the issue. Better cooling, better visibility, and
you will be in a better position to set up best glide, in the
event of a powerplant failure. R.B. MD
Attitude
The handmaiden of airspeed is attitude. When power is a constant
then airspeed is determined by airspeed. Poor liftoffs and touchdowns
occur not because of poor airspeed control so much as poor pitch
control. A pilot sets pitch attitude by using the visual view
of the actual horizon or selected horizon through the windshield.
Holding a given pitch with constant power sets airspeed. There
is a delay factor between setting the pitch and getting the performance.
The delay depends on the excess power and thrust available.
Even though the takeoff and pitch attitudes are similar they are not exactly the same. On liftoff a slightly lower pitch will be used for Vy and a slightly higher pitch will be used for Vx. Just prior to touchdown the pitch will be increased slightly to accomplish a minimum airspeed touchdown.
The kind of airplane and the pilot's seat position determines the level pitch position. Where you sit and how you sit in a cockpit will affect your visual picture through the windshield. The more consistent your position the better. The higher your position the better except in high-wing aircraft where you want to be able to turn your head and see under the wing without bending forward. Tall pilots want to have at least four inches of clearance below the headliner. Even a snug seat belt will allow you to lift about four inches off the seat in severe turbulence.
A pilot who learns in a nose-wheel aircraft has a near level pitch attitude while taxiing. The pitch attitude used for both takeoff and landing is one that just covers the far end of the runway. You should set and hold that attitude just as soon as elevator authority allows. On takeoff the initial set must be relaxed as soon as authority increases. On landing, the initial set must be gradually increased as elevator authority decreases.
The simulation of these attitudes is difficult to achieve. They are approximately identical except that the pitch authority of the elevator is increasing on takeoff and decreasing on landing. One way this can be demonstrated is by use of a runway that is not active. With ATC approval, taxi to the threshold end and shut down. The instructor should get out and hold the nose of the aircraft at various nose high pitch attitudes. Have the student advise you when the nose of the airplane reaches and covers the far end of the runway. The pitch attitude will approximate the angle set by the attitude of a tail-dragger aircraft. Only consistent exposure to this attitude and pitch pressure will provide the visual picture and memory of a proper takeoff and landing attitude. Once the stationary pitch position has been attained the instructor should move the tail side to side a foot or two to give a visual picture of how rudder movement affects the nose across the horizon. Since the horizon may not be visible over the nose the peripheral vision should be used referenced to the lower outside corners of the windshield. The purpose of this exercise is to show the pilot who is offset from the center of the aircraft just how much parallax adjustment is required to center the aircraft in taxiing, on the approach and on the runway. Every transition to a new aircraft presents both the pitch and yaw problem.
A
proficient pilot can:
--Set takeoff attitude on rotation
--Set both Vx, Vy and Vref for climb after takeoff
--Set clean pitch landing attitude
--Set full-flap pitch power on/off landing attitude
--Set go-around pitch attitude
The runup is completed and the trim is set for takeoff. We have used our pre takeoff and takeoff checklist and have been cleared by the tower. Taxi toward a point adjacent to the runway that will allow a turn that will give a full view toward final and base. Hold a couple of inches of back yoke. Cross the hold bars and align the plane with the runway centerline in a slow taxi. Check that the runway is clear. Smoothly apply full power. Lightly touch and hold right rudder as required to keep nose straight. Quick-check the instruments and listen to the engine. Learn what a normal aircraft engine sounds like during takeoff. With experience in hearing a good engine you will more readily recognize poor engine operation.
I let my students handle the first and all other takeoffs unless a demonstration is called for. Student applies power and rotational forces. Power is applied smoothly, rapidly, and fully. The instructor maintains initial directional control and may reach across to the student's fingers on the left yoke to help as required. The idea is to allow the student to relate pressure with yoke movement and nose attitude. The instructor's hand pressures on the student's is far more indicative of control requirements than if the instructor were to use his own yoke. Instructor maintains active control of rudder.
A takeoff has three distinct phases, first, the takeoff where the initial acceleration occurs and the emphasis is upon directional control and pitch attitude. Second, the liftoff where the pitch attitude is held to let the aircraft fly off around the landing gear rotation axis, only to be changed to adapt to the center of lift horizontal axis for acceleration. Finally, the initial climb out is set by attitude to perform a climb at Vy. This is usually the noise abatement climb speed.
The control position during the takeoff is set for full deflection toward any crosswind. In a crosswind weight is left on the main gear with the nose wheel barely off the ground. Initial directional control is a function of braking, since the rudder is the first control to become effective, use it as soon as it becomes effective. Liftoff is initiated at POH recommended speed by leveling the yoke and increasing the pitch to get liftoff before side loads can develop. Rudder is applied to crab into the wind sufficient to maintain track of runway heading. Do not set climb pitch until reaching Vx or even Vy.
Your problem, should you chose to undertake it, is to draw the diagram and place the words where they belong..
wind into position
direction runway and hold
hold bars
taxiway clearing/closer hold
short position to see runup area landing aircraft
runup
position
Make a guess at a yoke setting that will get and keep the nose wheel off the ground. This setting is usually obtained by moving the control-lock hole about three inches from the panel in a C-150. Every aircraft has such a yoke reference you just need to find it. Lock the elbow on the door. Scan the instruments when you first apply power. As acceleration occurs the elevators will become more effective and allow a yoke position to raise the nose wheel off the ground. This is called rotation and in the C-150 occurs at about 45 kts . If the rotation attitude selected is correct the aircraft will lift off at Vso but never any faster than 60 kts. This is the standard from which special circumstances require additional knowledge and skill. Any rotation will require an application of right rudder. Rudder is best applied in anticipation rather than reaction. The higher the nose the more right rudder required.
Rearward yoke pressure is maintained with one finger to get weight off the nose wheel. This pressure and any additional required to obtain lift off at 55 kts is locked by pressing the elbow and arm against the door. Minimum lift off speeds are desirable since higher speeds wear out tires. At lift off the nose is slightly lowered to allow acceleration to best rate of climb of 65 kts. If the initial trim setting was neutral in a C-150, a full downward turn of the trim wheel top button to the very bottom will come very close to being the correct trim setting for a 65 knot climb. Use this first climb out to let the student experiment with the results of full movements of the trim wheel. Trim is the cruise control of flying. Its early introduction and use is essential for developing awareness and a light control touch.
The rotation fault in the beginning is failing to do it at all. The plane proceeds down the runway at 60, 70 or even 80 knots and the student is still waiting for it to fly. Personally, I never let this happen more than once. It is exceptionally difficult on the aircraft. The next rotation fault is called over-rotation. This means that the nose is held so high off the runway that were the aircraft to become airborne it would be unable to climb or to accelerate. It is behind the power curve. The only thing that will get the aircraft flying is lowering the nose. Unless this is slowly and very carefully done a relatively hard contact with the ground will occur. This over-rotation is a practiced procedure used for making soft field takeoffs.
The rotation used for crosswind takeoffs is somewhat different in that the aircraft is lightly held on the runway with yoke held fully into the wind. This prevents the wind from sliding the aircraft sideways on the runway surface. At the moment the aircraft reaches a safe takeoff speed for the existing ground effect the yoke is leveled and the yoke is used to 'hop' the aircraft off the ground while the rudder is used to crab the nose into the wind. Once in the air the airplane is flown in ground effect long enough to reach climb speed. Takeoff stalls often occur if the pilot tries to climb before acquiring POH climb speeds. Through a misunderstanding of how ground effect can give an initial but false indication of climb capability, the pilot will initiate a climb at a relatively low airspeed only to find that his climb capability ceases at about half a wing span height above the ground.
There is an alternative to this minimum speed lift off. Some pilots prefer to let the aircraft accelerate nearly to Vx before lifting off the ground. This greatly increases tire wear and nose strut problems. On the other hand it does let the aircraft climb continuously out of ground effect without the momentary leveling off for acceleration.
Vso or minimum safe operating speed is the most desirable takeoff speed for several reasons. Aircraft tires are relatively small and expensive. The sooner they are off the ground the less wear. Rolling ground contact at high speeds is potentially more damaging to the airframe structure than at slow speeds. We want to get off the grounds as slow as possible. Less runway is required, thus more is available for aborted takeoffs. See Abort
The best angle of climb speed (Vx) is a precise speed at present weight that gives the highest altitude over distance. The hazard of the best angle of climb speed is that it is close to the power off stall speed. A power failure at best angle requires an immediate lowering of the nose to avoid disaster. The best rate of climb speed (Vy) is a precise speed at present weight that gives the highest altitude over time. Any speed different than the precise speed gives reduced performance.
Vx is the climb speed after Vso lift off that will, in the shortest distance and steepest climb, get the aircraft over an FAA tree. All FAA trees stop growing at 50".
The Vy climb would make the aircraft fly through the top branches of the FAA tree but would get the aircraft to a higher altitude in a given time interval.
Once we have established a climb at 65 kts in the C-150 the trim must be fine tuned for hands off. With experience you can pre-set the trim and 'know' the correct pitch attitude.
On takeoff it is a good practice to have the student check his runway alignment between three and four hundred feet AGL. The first time a student does this he will unknowingly pull the yoke and cause dramatic attitude and airspeed changes. Emphasize that the aircraft must be correctly trimmed and yoke released for the runway check. If parallel runways are it use it is well fly a 10 degree divergence from runway heading as a safety measure regardless of the wind and especially if there is a crosswind component that could carry you into the extended line of the adjacent runway. Once you have learned the standard takeoff you must be prepared to exercise different configuration, power control and pitch attitudes for the other types of takeoff.
Since so many takeoffs occur without incident, pilots are given a false sense of certainty that all takeoffs are successful. POH takeoff performance is based on an optimum technique. If you deviate from this optimum the aircraft performance will decline. In addition, with the present average age of operational aircraft you should add at least a 20% fudge factor into the book figures.
The takeoff is one instance where the aircraft should be trimmed so that after the first pilot setting of aircraft attitude than the plane does the rest. On initial power application the pilot should have anticipated the required yoke movement needed to hold a level attitude with minimum weight on the nose wheel. As soon as the elevator comes effective a fine adjustment to the yoke is used to set the desired climb attitude. These yoke movements should be anticipated before the need occurs. The sight view should be such than the aircraft nose covers the far end of the runway. This attitude is used except in crosswind conditions where the level attitude should be held until a higher pop-off airspeed is attained.
Since the rotation axle of the wheels differs from the center
of lift axis a slight change in yoke and sight picture will be
required once the aircraft becomes airborne. You are usually trying
to anticipate the trim for and then the yoke pressures to get
the Vy climb speed. Doing this correctly means that the aircraft
will fly itself off the runway with no yoke emphasis by the pilot.
Why takeoff pitch
changes
The initial lift off attitude at Vso is slightly higher than that required for Vy (best rate of climb) but is about right for Vx (Best angle of climb) so for a best rate climb after takeoff the nose needs to be lowered slightly to allow acceleration to 65 kts. The reasons behind this procedure are because the rotation of an aircraft while on the ground is about the axles of the main landing gear. Once airborne the rotation of an aircraft occurs about the centers of lift and balance..
On the ground an aircraft rotates in pitch about the wheels, in the air the same aircraft rotates about the center of gravity. This difference is the reason that on takeoff once an airplane leaves the ground there will be a perceptible difference in yoke feel and authority. The pitching moment in flight is usually much greater than when on the ground. For this reason a pilot should be prepared to counter this momentary change by immediately allowing the nose to lower after liftoff. For the same reason you should apply additional back pressure on the yoke on landing. This is needed at touchdown to hold the nose wheel clear of the runway.
Additionally you should not set your trim for a liftoff but rather for climb. This means that you will apply back pressure to the yoke for liftoff and relax this pressure to meet the 'takeoff' setting used for climb. I have noticed that this effect is most apparent with Piper aircraft in certain loading conditions.
The art of the smooth takeoff begins before lining up with the runway. The yoke should be held back so that the application of takeoff power will raise the nosewheel clear of the runway. Hold the nose so that it just touches the far end of the runway and the airplane will lift off the ground so gently and smoothly that you may not even notice breaking ground. Once off lower the nose to attain Vy since the difference in rotational forces from being on the ground and in the air makes it necessary. Knowing that this change is required is part of the art of anticipation that will make you a better pilot.
The procedure requires performance that results in the shortest
ground roll and the steepest angle of climb. Two beginning options
are available with little advantage going to either. Takeoff #1
is the rolling-running start where the aircraft tries to gain
speed while entering the runway. Full power is applied in anticipation
with runway alignment. Takeoff #2 places the aircraft so as to
be aligned at the very end of the runway. Power is applied with
the brakes applied until maximum rpm is attained. During the ground
roll the aircraft is held for minimum air resistance and best
acceleration. Figure a 1% decrease in book takeoff distance for
each knot of headwind. Any part of the runway distance not used
for initial acceleration is never to be recovered. Extending partial
flaps at moment of liftoff has not been shown to be an advantage.
Shortly before the best angle of climb speed is attained the aircraft
is rotated to that angle of attack what the pilot believes will
give the best angle of climb airspeed. The aircraft will accelerate
quickly after lift off so this change must be anticipated with
additional back pressure. Failure to hold a constant best angle
airspeed makes a significant difference in the flight angle of
the aircraft.
Pilot techniques will determine how well the takeoff occurs. Half the aircraft should project off the runway for maximum distance. Application of power should be such as to avoid 'loading-up' the carburetor. At full power the aircraft is allowed to accelerate to rotation speed. Pre-mature rotation is a major mistake and more common than delaying rotation. The technique for rotating, obtaining, and holding that attitude which will give the best angle of climb takes practice. There is a lag in airspeed indications and aircraft performance which makes much practice necessary. Using the airspeed indicator usually results in a lower pitch attitude than required.
Departure on an apparently short runway can contribute to a series of piloting mistakes which compound the problem. The pilot may mistakenly attempt to get into the air too soon, before the airplane is ready to fly, by over rotation. Sure, the nose will go up. Over rotation will require the nose to be lowered to obtain climb speeds and result in decreased climb performance both over time and distance. Aircraft speed is one way to get the lift performance to overcome an obstruction. At lighter than book speeds the speeds of performance change at a rate of 1/2 the percentage of weight change. A 20% reduction in gross weight will allow a 10% reduction of book speed for maximum performance.
The success of a maximum performance short field takeoff requires precise control of airspeed and aircraft attitude. Even a slight deviation of either initially or later will result in a significant reduction of performance.
What to avoid:
1. Not using all available runway
2. Getting to full power quickly
3. Lifting off too soon
4. Letting airspeed exceed Vx
(Introduction)
The situation is a takeoff area of unlimited length but having
a soft surface the nature of which would prevent acceleration
of an aircraft to takeoff speed without the application of special
techniques. The intention is to make a running start on to the
runway with 10 degrees of flaps and the yoke held full back. Power
is smoothly applied so as to give sufficient elevator power to
raise and keep the nose wheel off the ground. The aircraft is
allowed to lift off at a minimum flying speed that can be maintained
and accelerated only in ground effect. The aircraft is flown in
ground effect until climb speed is attained. At 200' AGL the flaps
are removed and normal climb maintained. So much for procedure.
Piloting techniques require that the elbow and arm be locked so that over rotation does not occur with sudden power application. Coordinated power and yoke is required to attain the required/desired smoothness. As the aircraft accelerates the pitch attitude is increased to attain lift off. Anticipatory rudder application is very important during this entire takeoff to maintain directional control.
Once in the air you will be behind the power curve. This means that since you have no more power available you must lower the nose to increase the speed. Unless this speed increase is carefully crafted by combining close flight to the ground and a gradual lowering of the nose an unintentional ground contact is likely. The closer you are able to fly to the ground while avoiding contact the sooner the aircraft will attain the flying speed required for climb. Most common mistake is failing to remove flaps at 200'.
(demonstration)
At controlled airports the non-assertive pilot just goes where
he is told to go. There are occasions where for convenience or
necessity that you may need to make a downwind takeoff. If a downwind
takeoff is assigned or mandated by field conditions the pilot
has a few things to think about. The pilot must understand that
as little as a 10 knot tail wind will almost double the takeoff
distance. Increase takeoff distance 10% for each 2 knots of tail
wind. Ground speed will give all the sounds, feel, and sensations
of being much faster than usual. It is. I don't suggest any takeoffs
with more. Ground speed will be 20 knots higher at liftoff than
it would be for a 10 knot headwind. Rotation and climb speeds
are indicated airspeeds and remain the same. The climb will be
flatter and even at Vx we won't clear much of an FAA obstacle
until nearly twice the usual distance. With a tailwind, we will
need a higher ground speed to make the indicated rotation speed
required for lift off. Most pilots show a lack of knowledge as
to just how much a tail wind can affect takeoff performance. Any
tailwind with a component of 10 knots is going to be full of surprises.
Tailwind accidents occur with nearly the same frequency as density altitude and low ceiling accidents. Tailwind accidents happen half as often as crosswind accidents and twice as often as carburetor ice accidents.
Short, Soft, and Rough Takeoff
Use the recommended flap setting either prior to takeoff or after reaching 30-40 knots. The idea is to get clear of the ground as soon as possible and utilize the reduced induced drag by staying as close to the ground as possible until reaching Vx or Vy as required.
This is takeoff is like a combination dinner order. A bit of
everything and not too much of anything. We may compromise on
the amount of flaps used, we compromise on how high to hold the
nose, and we compromise the performance figures between Vx and
Vy and everywhere else. It is worth noting that loading to the
rear C.G. limit will get us into the air sooner but with a compromise
in control sensitivity. If an obstacle is present blend your combination
toward short field performance.
Once airborne fly direct to the obstacle. If you are above the
best angle of climb speed you can then fly Vx with some assurance
of passing above the obstacle. Visually, if you can see more and
more of terrain over the top of the obstacle you are higher than
the obstacle. If not Vx chop it and drop it. Given two poor choices,
it is better to hit something on the ground while slowing down
that anything while flying.
(once is enough)
It is all too common to have a seat slide back during initial
takeoff acceleration. For this reason the seat security should
be part of the takeoff checklist as well as doors and windows.
Have the student accelerate for take off and pull the power off
just before lift off. Do not apply the heavy braking that might
be required in a real situation because of possible damage to
the nose gear or tires. The idea of rejecting the takeoff with
a resulting accident off the end of the runway is not pleasant.
Running off the end of the runway while decelerating is better
than colliding with the ground after becoming airborne.
Training works provided you remember to carry the lessons learned into the situation. The takeoff is one of the highest risk phases of flight. Time is not, necessarily in your favor, at 60 knots you are going 100 yards (a football field) every three seconds. At 80 knots 200 yards in five seconds. Regardless of the runway, you should pre-decide an abort point for every takeoff. Beyond that abort point you are committed to takeoff. Due to potential hazards the aborted takeoff is best not practiced to excessive limits. Simulate but doing the real thing can be dangerous or hard on the aircraft. Once airborne the reason for aborting becomes even more complex and dangerous. Quick thinking and analysis is needed prior to liftoff. Hitting something while skidding off the runway can be far less damaging than going into an off-airport area. Use 150% of the POH landing roll distance for your required abort/stop distance.
The sooner the abort decision is made the more chance of success. On a short runway abort before lift off. Heavy braking is hard on the aircraft but it will probably be required in an aborted take off. If you have full power you may be better off not to abort. Abort problems often occur when there is a conflict of authority. If airborne, continue if door pops open. Return to land and close door. In the event of fire or smoke be prepared to evacuate.
Takeoffs are successful so often that we fail to prepare for the one failure. In fact, we will never be fully prepared for rejecting the takeoff unless we learn what to do before it happens. We must pre-decide what aircraft performance we will require over the distance remaining. We must relate what we have commonly experienced in acceleration and speed with what is occurring at a given moment. If the performance is not there, we must immediately pull the power and mixture, apply brakes up to the point of a skid but not into the skid. We must maintain a straight line with the yoke pulled all the way back to give maximum weight to the main wheels.
The aborted takeoff, often called the RTO or rejected takeoff,
is a not too common occurrence. It can occur because of a seat
sliding back, a clearance, a door opening, etc. Airlines have
RTO (rejected take off) 1 out of 2000 takeoffs more often because
of indications of failures rather than actual failures. You must
make a book determination that the runway is adequate for the
aircraft and conditions. A conservative 2.2 x book figures is
a good risk management margin for takeoff. A 10 kt tailwind will
double the book figures without any margin. If you are half way
down the available runway and performance is not as expected,
abort. Some abortions occur because the pilot has not correctly
anticipated how density altitude and changing wind conditions
along the runway. Winds can and do vary along the length of a
runway.
If you can reduce your speed by half before impact with an object
you will decrease your force of impact by 75%. Hit any objects
while turning with the wing or tail to utilize the ability of
collapsible material to absorb impact. Your survival is more important
than the insured condition of the aircraft. At impact be sure
electrical system is off.
An aborted takeoff due to engine failure should include immediate power reduction, mixture to idle/cutoff, and heavy braking on runway heading with a ground loop as required to avoid obstruction impact. Any engine failure after takeoff should be followed by setting nose glide angle and trimming (3 additional full turns from climb trim) for best glide. Select the best available within 60 degrees of heading and wind direction. Pull throttle and mixture to full off since numerous fatal accidents have been caused by sudden and unanticipated power resumption. Shut off the fuel. Avoid obstacles and use full flaps prior to ground contact at minimum speed. Turn off electric master when flaps are down. Unlatch doors.
At some later point in the training a no-airspeed-indicator takeoff should be made. The student will be required to visualize the nose attitude that gives a desirable airspeed. Requiring visualization is good for the student because they must have in their mind a picture of what they are doing. With the airspeed and perhaps other instruments covered makes the student feel and hear aircraft performance.
I have only aborted one takeoff in 30 years. I did this when engine power did not seem adequate. Twice I did not pick up the lack of airspeed indication on takeoff and proceeded to takeoff when indicator showed only 60 knots or less. I one case, at night, I returned for an uneventful landing and removal of the pitot cover. In the other pitot heat melted the ice in the pitot tube in less than a minute. Preflight could not have picked up the ice blockage. In cold weather preflight use of pitot heat is a viable consideration. An aborted takeoff gives you three results. First, you have time and distance to stop. Second, it is better to go off the end of the runway at a slow survivable speed than, third to become airborne in an uncontrollable configuration that will result in injury or worse.
The crosswind takeoff requires some timing skills that are not present in other landings. On full power application the yoke is held full over into the wind but not back as in normal conditions. The intention is to hold the up-wind wheel on the ground while remaining firmly enough on the ground to prevent any sideways skipping of the aircraft. As the ailerons become effective only enough is used to prevent side movement.
Although the student has been making takeoffs from the very beginning of training, the crosswind takeoff has a special technique. During the application of power and acceleration the plane must not be allowed to lift off the runway until you are certain that flying speed is acquired. In the C-150 this will be about 55 knots. As with taxiing, the yoke is held full over into the crosswind to prevent the upwind wing from lifting. The nose wheel is kept lightly on the ground.
One of the reasons you should always practice estimating winds at airports that have wind reporting is to develop some skill at direction and velocity estimates. A wind less than 10 knots will take the droop out of a wind sock. Over 15 knots straightens out the sock. The headwind of a 30 degree off runway heading wind should be given full value. Up to 60 degrees off heading should be given only half its velocity value. Beyond 60 degrees the headwind has no value. Rule of thumb says every 10 knots of wind speed reduces takeoff distances by 15%. A 10 knot tail wind will double all distances.
The crosswind takeoff requires a somewhat longer roll before
liftoff since there is aerodynamic drag due to the deflection
of the control surfaces. This deflection will slow the acceleration.
Additionally, the forward yoke pressure required to keep the crosswind
side-load from sliding the aircraft sideways prior to liftoff
will slow acceleration. When liftoff flying speed is attained
at 55 kts the yoke is leveled and given a rather abrupt movement
to 'hop' the plane into the air before side loads or skidding
can affect the landing gear.
The crosswind takeoff requires some timing skills that are not
present in other landings. On full power application the yoke
is held full over into the wind but not back as in normal conditions.
The intention is to hold the up-wind wheel on the ground while
remaining firmly enough on the ground to prevent any sideways
skipping of the aircraft. As the ailerons become effective only
enough is used to prevent side movement. This aileron change depends
on the pilots sense of takeoff speed and the crosswind effect.
Once the speed reaches within five knots of your normal rotation speed a combined series of events should occur. The yoke is leveled and moved relatively abruptly to 'pop' the aircraft off the runway. Once off the runway the plane is held into ground effect and crabbed into the wind with rudder application. The intention is to allow the plane to accelerate quickly while maintaining runway alignment. Unlike the landing, no effort is made to keep the aircraft parallel to the runway centerline.
In the air, rudder is applied to turn the nose into the wind. The hop and rudder application is about simultaneous. The ball is centered. Slight forward yoke is held to set the angle of attack required for normal climb. Once off the ground the aircraft will perform the same without regard to the wind. No effort is made to keep the plane parallel with the runway as when making a crosswind landing. Rather, the plane is crabbed into the wind with the ball centered by rudder. Heading is adjusted to correct drift so as to maintain a ground track in line with the runway center line. When operating from parallel runways it is always a good idea to take a 10 degree cut away from the adjoining runway regardless of the wind. Skill in tracking a line in a crosswind is directly related to ground reference skills.
From an instructional viewpoint the best initial lesson should
occur in a crosswind of about 10-12 knots. You want enough to
make the cross control position for takeoff necessary but not
so much that mistakes will create a hazard. Later lessons should
be deliberately planned with ever stronger winds. The student
needs to be exposed so as to determine how his ability in this
aircraft.
Opinion
There are two distinct techniques used:
1. Keeping the longitudinal axis of the aircraft aligned with
the centerline of the runway and maintaining a certain bank-angle
to compensate for the crosswind; and
2. Maintaining a crab angle on approach, and applying some rudder
just before touchdown to get the aircraft aligned with the runway.
Opinion
Technique #2 actually consists of crabbing into the wind and
remaining coordinated for most of the final approach and then
converting to technique #1 just prior to touchdown. The trick
is in judging just how much slip is required to eliminate any
sideways motion at touchdown.
Opinion
Practice makes perfect, but don't get in over your head. Start
with a modest, steady crosswind and work up as you become proficient.
Don't practice alone, make sure your instructor is there to give
advice and keep you out of trouble.
Opinion
Sometimes the simplest explanations are the best.
From a former instructor:
Use the ailerons to compensate for drift away from the centerline,
and the rudder to keep yourself aligned parallel to the runway.
With this in mind, you'll be using the controls automatically
to compensate without realizing it. Like driving a car; do you
consciously think of how much pressure to apply to the brakes
to stop in a certain manner, or how far to turn the wheel to turn
into another street? Probably not; you just do "whatever
it takes". Of course the landing/driving analogy breaks down
when one considers that you can always see which way the road
will go when driving, but you can only react to gusts when landing.
But that makes it fun.
Opinion
Put aileron into the wind with opposite rudder during the
final approach. If strong winds are present then use a no-flap
or partial flap approach. It's that simple. Don't make it more
complicated than it is.
Opinion
Wish I could have made it that simple and easy for the students
I have taught over the past thirty years. Seems that students
have trouble with all the variables of airspeed, wind velocity,
bank angle and rudder application. Of all standard flight maneuvers
the crosswind landing requires the greatest variety of contradictory
control applications.
Opinion
The trick is to separate in your mind the function of the
controls. Once you turn on finally, the rudder has one purpose
- keeping the nose aligned parallel with the runway, regardless
of the position of the runway centerline. The ailerons have just
one job, maintaining position over the centerline.
Opinion
Every aircraft is certified as having a demonstrated crosswind
capability. This is determined by the winds available at the time
of certification. An average pilot should be capable of landing
in such conditions. As crosswinds exceed this demonstrated minimum
a pilot should minimize flaps and increase approach speed. The
maximum aircraft capability is exceeded when full control input
is not capable of maintaining directional control even at increased
speeds.
Class
C Mountain Departure
Had a situation late this afternoon when departing Reno for
Concord, CA. To go west from Reno you must cross a ridge that
is nearly 8500 feet. I try to give at least a 1000' cushion even
in light winds. In strong winds 2000'
In order to give my C-172 some extra climb time I requested a left 270 off 16L. My clearance was, "Proceed on course, VFR, Departure 126.3 and Squawk 3454." I confirmed with Reno Tower that the left 270 was not contrary to the clearance.
On my arrival to Reno I had been told to cross midfield for a left downwind arrival to 16L at or above 6500. I quired the tower as to whether there was a minimum crossing altitude on my departure and was assured none was required.
However, just as I turned to cross the airport, a Navajo called in and was told to enter right downwind for 16R. It was apparent that we were in conflict. I immediately told the tower that I did not have the traffic and requested a vector. I was told to turn to 160 which is parallel to my departure runway. I found the traffic and told the tower that I had contact and requested to proceed on a course that would take me behind the Navajo. On course was approved and I was then turned over to Departure.
Several problems were resolved in my departure. All of these suggestive solutions to ATC required that I be assertive in my proposals. Knowing what to say in such a situation comes with experience. I make a point to expose my students both to the situations and how to use the radio to get what you want/need from ATC.
What every pilot needs to work on is saying what needs to be said in a timely and efficient manner. I am presently working with a 'retread' who has great difficulty thinking of how to send a verbal telegram instead of a letter. I am having him write out word for word what he is going to say in a particular planned situation. By always giving your accurate position, direction of flight, and altitude you will set an example that will be 'catching'.
--The open door is no emergency
--Noise and sense of speed are increased.
--Some loss of climb
--Ignore door, land and close door
--Simulate approach at altitude for practice
--Airborne closing is possible.
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