As a flying instructor, a common problem that I hear from pilots is that they float too much during landing. At aerodromes with shorter runways, it can often make the pilot feel like they are going to run out of runway. The temptation is to push the control column forwards to push the aircraft on the ground. However, this can turn an uncomfortable landing into a disaster. If the pilot has to force the aircraft onto the ground then it is likely that the wings are still producing lift and the aircraft is not ready to land. The most likely result of forcing the aircraft onto the ground is that all three wheels will touchdown at once and it will wheelbarrow.
Wheelbarrowing is said to occur when the weight of the aircraft becomes concentrated about the nose wheel. If the nose wheel strut is compressed heavily, it is likely to rebound causing the aircraft to pitch up and become airborne again. It may also pitch up due to a bump in the runway or even a gust of wind may cause it to take-off again. Bearing in mind that the aircraft still has flying speed because it was not allowed to land naturally, anything that causes the aircraft to become airborne again will cause the aircraft to fly. However, if the nose has pitched up, the airspeed will rapidly decrease, causing the aircraft to naturally pitch down. Without pilot input, the nose wheel will contact the ground again and the process repeats. The result is a series of rapid bounces which increase in severity until the pilot takes corrective action or the nose leg gives way. A light aircraft is unlikely to tolerate more than two or three bounces.
How should a pilot avoid excessive floating and wheelbarrowing?
The primary cause of excessive floating during the landing phase is an excessive approach speed. The Pilot’s Operating Handbook will detail which speed should be used for normal landing, short-field landing and crosswind landing. Despite this, many pilots choose their own approach speed, adding a few knots “for control authority”. The result is that the aircraft ends up above the threshold five or ten knots faster than the manufacturer intended. This excess speed has to be burned off during the flare before the aircraft can be in the position that it should have been in at the threshold.
Another cause of excessive floating is approaching too high. This is actually the same as approaching too fast. The pilot approaches too high and realising they will overshoot the runway, they push forward on the control column in an effort to increase the rate of descent. The bottom line is that the aircraft has too much energy and pushing the control column forward will only cause the aircraft to accelerate. This hasn’t solved the problem, because now the aircraft is no longer overshooting but it arrives at the threshold too fast just as described in the previous paragraph.
When approaching a runway in calm wind conditions, or when the wind is entirely crosswind, the pilot may also feel like the aircraft is floating for too long. Although the time it takes to lose speed for landing is the same, it will use more runway in these conditions because the ground speed is higher. Touching down close to the threshold will reduce the chance of running out of runway, so accurate flying is required on final approach. It is also important to check that the aerodrome you are visiting is suitable for your aircraft. Refer to the flight manual for runway performance figures.
What should a pilot do if wheelbarrowing commences?
Porpoising can get ugly very fast! Firstly, if you are approaching too fast in the later stages of final approach, or you are excessively high to make a safe landing, then you should go around. It is better to go around and fly a stable approach than to try to “fix it”.
"If the aircraft begins to wheelbarrow, then there is a difficult decision that the pilot has to make rapidly: Can I fix this or should I abort the landing?"
If the aircraft begins to wheelbarrow, then there is a difficult decision that the pilot has to make rapidly: “Can I fix this or should I abort the landing?”. A low-houred pilot should go around. An experienced pilot may have sufficient judgement to regain control of the aircraft after the first bounce and stabilise the attitude, but this is difficult for inexperienced pilots. If the pilot attempts to salvage the landing, this is done by applying sufficient power to cushion the subsequent touchdown and smoothly adjusting the pitch to the proper touchdown attitude. However, all pilots should go around from a severe bounce and must not let the aircraft make contact with the ground again.
If a pilot attempts to make corrections from a severe bounce, then the control and power inputs are likely to be untimely and out of sequence with the porpoising, causing them to be further exaggerated.
Conclusion.
Make a concerted effort to nail your approach speed and fly a stabilised approach every time. Avoid aerodromes with runways that are too short for your aircraft or abilities. Remember, if it goes wrong, go around. Keep these things in mind and you will avoid bending your aeroplane.
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