So how do we do it? All good landings start with a good approach (my old flying instructor told me that), which means a constant attitude and speed on the glide path. Therefore if you are constantly pushing and pulling on the elevator the speed and attitude will be constantly changing, ergo bad approach and landing.

A good approach starts on the downwind leg. So after you have finished tearing holes in the sky descend to circuit height and when established on downwind slow the aircraft down by reducing the throttle to around half throttle. When the aircraft has slowed lower the flaps to around 20 degrees (if you have only one flap setting I suggest you set them at 20 degrees. If you also have a second level then set this at around 40 degrees). At this stage you may need to introduce some down trim to maintain level flight, although some aircraft may pitch down due to the change in downwash over the tailplane. You will discover that if you lower the flaps at too great an airspeed the attitude change will be much greater and more abrupt and you also risk ripping them off the wings. You may wish to consider programming (mixing) some down elevator when the flaps are lowered. If you have retractable undercarriage then put the wheels down now.

At this stage you should be approaching the base leg. Fly gently around the corner avoiding tight turns and maintaining level flight on the base leg. Then turn onto final and reduce the throttle to a high idle and lower the flaps to 40 degrees. Again more elevator trim will be required to counter the pitch up tendency. The aircraft will now be descending. The trick here is to keep the level attitude and constant speed by controlling the rate of descent with throttle. If undershooting increase the throttle and conversely if overshooting reduce the throttle. Elevator should only be used to keep the aircraft level and not for speed control.

Once over the runway threshold the throttle can be closed completely. When the aircraft begins to sink it is a sign that speed is reducing due to the drag caused by the flaps. Now you can start to slowly ease back on the elevator trying to hold the aircraft in that level attitude all the way to the ground and a perfect landing. The operative word here is `level', do not try to extend the approach by keeping the nose up. Remember high angle of attack equals stall which equals crash.

Once you have landed and come to a stop retract the flaps and taxi back to the pits. If you leave them down a gust of wind may pick up wing and cause some damage.

Going around

If you got it all wrong and are still too high over the threshold to manage a landing then you need to go around and try again. Be careful. With full flap down the sudden application of full power will result in a strong pitch up. Be ready for it but do not be tempted to put the flap up until you have reached a safe altitude and have good control over attitude and speed because when the flaps are raised lift is reduced and the aircraft will sink unless other compensating action is taken. The natural tendency here is to pull back on the elevator resulting in a stall (not good). The initial climb out with full flap will be much less than you are used to due to the large increase in drag caused by the flaps.

If you have two stage flap you can easily fly the circuit with one stage still down thus setting yourself up for the downwind leg.

Taking Off

What about flaps on take off?

A viable option yes, but remember anything over about 20 degrees of flap will result in an increase in drag. While the take off will be good the rate of climb will make the boundary fence look like the Great Wall of China.

However given the average size of models, the enormous power advantage (models are generally significantly over powered compared to the full size counterpart) and relatively long runway we use, flaps on take off are probably unnecessary and just an added and complication.

Lessons learnt

So what have we learnt about flaps. They allow:

• a slower approach and touch down speed
• a steeper approach allowing better obstacle clearance into short fields
• a shorter `float' after flaring due to the increased drag
• a shorter ground roll after landing due to the slower landing speed and breaking effect of the flaps

  Flaps also cause

• a pitch up when extended but this can be reduced by flying at an appropriate speed before extending the flaps
• a pitch up when power is applied during a go around
• a reduced ground roll during take off but also a reduced rate of climb if too much flap is used. I hope this article has dispelled some of the myths associated with flaps and perhaps also encouraged you to go out and try. As the saying goes if you've got them, use them. You will soon work out how they can improve your landings.

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