"Spiral of death" in planes/winged platform is every FPV/UAV pilot nightmare. It happens after a stall event (due not having much airflow over the wings to get some lift) and the plane plunge down in spiral manner. For straight winged type its easy to recover but planes that have Di-hedral (that have wing tips bent upwards for stability) especially long tailed fuselage is really hard to recover. Below are simple steps and advice how to quickly gain control before it smacked into the ground.
So you're now spiraling down to earth, what should you do? Relax and follow this tips:
Release all the control sticks.- Don't pull the elevator! Let it go down so the gravity will do the work helping to get some airflow over the wings. Putting elevator on spiraling plane just make it worse. Your job now to stop the spiral and get some air flowing over the wings
- First we need to get the plane stop spiraling around. If it spiral to the left. Counter it by pushing 50% aileron stick to the right and 50% rudder on the right too. If it spiral to the right. Counter it by pushing 50% aileron stick to the left and 50% rudder on the left too. Don't immediately apply 100% throw on all surface control else you'll adding "air-brake/spoileron" effect causing it to stall even more.
- Slowly apply smooth throttle from 1%~100% while keep your thumbs holding/counter your aileron and rudder control. Once you get the feeling its started to slow down the spiraling effect the you can safely apply full 100% throw on aileron and rudder until it stop spiraling.
- Once you got it stable and get enough air speed. Pull the elevator up to normal horizontal flight position.
- There you go, you're safe.
Why "Spiral of death" happens on my plane.
"Spiral of death" happens when you don't have enough airflow flowing over the main wings, lost lift and then goes down nose first, the wing . Usually it happens often on plane that have Di-hedral wing tips which holds the spiral lock into spiraling position. Usually its very easy to recover from such event but a difficulty to recover indicates a badly setup plane especially on CG (Center Gravity), disturbance on wings aerodynamics and weight issue.
Here are some factor that contributes uncontrollable "Spiral of death" problem other than just being Stall:
- Over weight plane (exceeding more than 30~35% from airplane stock flying weight)
- Wrong CG.
- Extremely nose heavy plane.
- Too much "Di-hedral". (beginners biggest mistake in choosing this wing feature).
- Interrupted/bad wing aerodynamics. (usually most FPV/UAV pilot abrupt the wing surface aerodynamics by putting/embedded video transmitter module, radio antenna and other frequency emission device for better LOS (Line Of Sight) transmission.)
If you have such above setup don't fly too slow to almost stall speed especially at low altitude. If you do make sure you have enough altitude to bail out. 300m is your minimum best bet for recovery on 1.2m wing span.