This question was posed on a forum that I was included on. The short answer is “yes,” but there’s a lot more to it.
A few years ago I was offered this immensely powerful machine to try out. It was normally used for tandems, weighed nearly 100 pounds, and had probably 200 pounds of thrust with the large prop it spun. It was a handful for my 140 pounds, but there was enough wind to make a forward launch easy so I went for it.
High power machines are best treated with great respect, especially during takeoff, so I got on the thrust fairly slowly while running then climbed out at half power or so. Once up a few hundred feet I got some feel for the motor and went to check out full power. Slowly. At some point, the angle looked so steep I chickened out. There is an angle beyond which physics will cause “unwanted aircraft states” as the lines go slack and torque plays out a discordant riff. I didn’t want to be the guinea pig.
That was one of only two machines I’ve ever had to beg off on the power due to steep climbs. Most don’t manage torque well enough to get that far, let alone have enough thrust to cause a concern.
This suggests that a properly adjusted wing will at least be difficult to stall solely from power. Most of the angle is simply from the flight path being angled up as described in the PPG bible. But this isn’t the end of the story.
Yup, And it Happened to Me
Many suns ago, in my early years, I was trying anything I could get my hands on. There was a pilot who had been trying to launch his wing and couldn’t. Always up for a challenge, I asked if I could try.
For starters, it was a big wing but not much bigger than what I was flying (also a big wing by today’s standards). I committed to holding the A’s well into the run and managed to launch, holding them almost all the way into flight. When I reached for the breaks and felt immediate tension I knew it was a bad situation, even as a relatively new pilot.
Sure enough, without any brake input the wing slowed down and went parachutal. It stalled. Amazingly, I was completely unhurt having landed on a softish surface and my machine taking the fall. What happened? Simple: the brakes were tied too short. Even in their pulleys, they were slightly pulling some trailing edge. The owner was a free flight pilot who weighed 40 pounds more than me.
This was the SECOND time I had gone parachutal under a big wing.
The main lessis is that power will absolutely aggravate a stall situation, especially for lightweight pilots on powerful machines or wings trimmed slow. That includes wings where the rear lines have shrunk. If your wing is getting hard to inflate in still air, it’s probably in this category. I’ve recently flown a wing where the brakes were tied short enough that the pilot had begun to launch with the trims fully out.
Aerodynamics of It
Power imparts a torque on the wing that slightly increases angle of attack that can hold a wing in a stall where it would otherwise recover. It’s not as simple as multiplying thrust by distance from the wing because of gravity. In a climb, gravity opposes the force, neutralizing most of it. So it’s not as bad and too-simple math might suggest.
Indeed, the affect is usually pretty minor, as my experience, and physics suggests, but still causes crashes, usually to pilots already compromised as described above. It happens far more often when combined with torque. The machine twists a pilot left, for example, causing the wing to go right. He doesn’t want to go right and pulls brake. A spinning stall soon follows.
Risk is mitigated by:
- Taking off at a faster (let out) trim setting.
- Making sure the rear lines aren’t shrunk.
- Making sure the brakes aren’t tied too short.
- The MOMENT you feel any excessive twist or slowdown in airspeed, immediately, smoothly, reduce power, reduce brakes, THEN steer, mostly with weight shift.