35% ??
Posted: Wed Oct 28, 2020 2:07 am
This is really only relevant to the DA40NG since the twins have lots of data in the AFM about one engine operation.
I'd heard that loss of the turbocharger in an Austro engine cuts the power back to about 35%. Since a DA40NG popped its boosted intake hose off last year leading to an off field landing (all safe), and there are many ways for a turbocharger to fail, I wanted to understand what 35% meant. I had previously established that 40% gave me 90KIAS in a holding pattern so I was pretty optimistic about 35%.
Today I flew at 7,500' with the AP in HDG/ALT modes and pulled the power to 40%. I waited for the plane to slow down and it eventually settled to 90KIAS as expected. Then I pulled the power to 35%.
The plane again began to slow, and then pitch up. It slowed, pitched up, and slowed and pitched up as it attempted to hold altitude. At 70KIAS and continuing to pitch up I decided this was going to just lead to a stall so I changed the vertical mode to VS -100fpm. The plane pitched down slightly and settled at 86KIAS. It continued smoothly at 86KIAS and a 100fpm rate of descent for a few minutes.
Conclusion: At 35% power I could not hold altitude, but I could hold a -100FPM descent rate at 86KIAS (very close to the 88KIAS glide speed). If in fact the loss of the turbocharger yields about 35% power, then even at 1,000' AGL, I should have some time to find a place to put down.
I hope neither you or I ever have to use this information!
I'd heard that loss of the turbocharger in an Austro engine cuts the power back to about 35%. Since a DA40NG popped its boosted intake hose off last year leading to an off field landing (all safe), and there are many ways for a turbocharger to fail, I wanted to understand what 35% meant. I had previously established that 40% gave me 90KIAS in a holding pattern so I was pretty optimistic about 35%.
Today I flew at 7,500' with the AP in HDG/ALT modes and pulled the power to 40%. I waited for the plane to slow down and it eventually settled to 90KIAS as expected. Then I pulled the power to 35%.
The plane again began to slow, and then pitch up. It slowed, pitched up, and slowed and pitched up as it attempted to hold altitude. At 70KIAS and continuing to pitch up I decided this was going to just lead to a stall so I changed the vertical mode to VS -100fpm. The plane pitched down slightly and settled at 86KIAS. It continued smoothly at 86KIAS and a 100fpm rate of descent for a few minutes.
Conclusion: At 35% power I could not hold altitude, but I could hold a -100FPM descent rate at 86KIAS (very close to the 88KIAS glide speed). If in fact the loss of the turbocharger yields about 35% power, then even at 1,000' AGL, I should have some time to find a place to put down.
I hope neither you or I ever have to use this information!