Use of Flaps
Take-off run
In general, setting a negative flap setting gives you better aileron control at all speeds, for this reason typically we set a stage of negative flap during the initial stage of the take-off run. Once we have built up sufficient aileron control, we can then shift the flaps to the recommended positive flap setting for the remainder of the launch. When it comes to winch launches, consult your flight manual.
Approach to land
The most important thing first, do not change flap settings toward negative (from positive) near the ground, followed by, never select your landing flap until you’re assured to make your aiming point – otherwise your flight may end in a very different way than you had hoped, a disaster...
Talking about accidents, many have happened when the pilot has changed their flap settings while in close proximity to the ground. An UN-flapped glider does about 10:1 with its airbrakes out, suddenly the pilot realizes that they’re low on approach, closes the brakes and the glider resumes its 35:1 glide ratio, correcting its flight path easily. Sadly, the same isn’t true for a flapped glider, the flapped glider when it has its flaps (only) out is doing, maybe doing 20-25:1, so when the pilot closed the airbrakes (from 7-10:1), it only recovers its glide to the flapped best glide figure – which may not be enough to get you safely to the airfield.
In this situation, the pilot might then decide to reduce the flaps to restore full glide performance, however, there is a catch, an important catch to know. When you reduce your flap setting, it reduces lift initially, causing a drop in altitude, done low enough, this can cause an accident, a broken glider, perhaps a broken back too... The secondary effect of this rapid drop in height low down is that the pilot might counteract this drop with pulling back on the stick, causing a stall. Naturally, both these situations should be avoided!
The important bit that was first and now repeated again, do not change flap settings toward negative (from positive) near the ground, followed by, never select your landing flap until you’re assured to make your aiming point.
After touch down
As we said for the takeoff, negative flaps provide better aileron control, which makes it advisable to select them once we start to lose aileron effectiveness – read that again, once we start to lose aileron effectiveness. If we select negative flap immediately after landing, all the lift will be dumped at a high speed, causing the wingtips to drop very quickly towards the ground, add in there superior aileron effectiveness and sensitivity to your input. What can result is an unexpected, high-speed ground loop, naturally something you want to avoid! So my advice is this, settle into your ground roll, plan your stopping point, once you start to lose aileron effectiveness, slowly and deliberately, set your flaps to negative to maintain control. The last advantage of negative flaps before your wings touch the earth again is that you’ll be saving your ailerons from a graze!
Happy landings!
Banner photo by John Absolon, 'Got that shot' Images
Adam Woolley was born into the gliding world, being the 3rd generation in his family. Going solo at 15, his thirst for efficiency in soaring flight & quest for a world championship title to his name has never wavered. One big passion is sharing his experiences & joy with other glider pilots all around the world. Adam is an airline pilot in Japan on the B767 & spends his off time chasing summer around the globe. He has now won 7 national Championships & represented Australia at 5 WGC's & 1 EGC.