correct as is Torque curve

[Denwagg]

Why does torque go up and back down a couple of times when collective increase is smooth

[Raven (Elysian Angel)]

I'd like to know that as well. Perhaps a RL helo pilot can elaborate?

[jayst0r]

Must be some of the flight computer/govenour doing something I have noticed this too, especially when transitioning from hover to flight. While accelerating at around 100 knots and also slightly at 130 knots, I have seen rapid >10 % changes while stable flight and not touching the collective or cyclic, what follows is a sudden almost barrel roll to the left. And this is with a neutral aero trim. I dont know maybe the left roll is from retreating blade stall. But i have the feeling  it comes from sudden increase in torque. have to investigate this more.

I think this also happens in Hover sometimes, at about 3-6 knots its all stable and fine, climb at around half a bar above neutral, make small adjustment to neutral/zero climbb, all fine and suddenly it jumps and half rudder deflceting is needed to compensate to the right and then after that same to the left once it calmed down. Doesnt seem right to me.

Edited March 22, 2022 by jayst0r

[NineLine]

Will you accept and answer from a pretend pilot who asked a real pilot?

Its just stabilizing, there is more resistance as you increase pitch and the engine has to counter and catch up.

[comcat]

Real Pilot: It is correct, although it seems exaggerated in the ED AH64.

In real Helicopter dynamics:

if you raise collective, RPM dips down (slightly) Governor tries to keep up- TQ overshoots and comes back down.

If you lower collective, rpm go up ( slightly) Gov throttles back- TQ goes down, then catches back up.

If you put cyclic fwd in flight, disc load goes down. rpm down-gov goes up-then down.

if you give left pedal, Demand on engines go up, TQ goes up and vice versa on right pedal.

and so on.

all depends on your inputs---smooth is the key.

I do agree its a bit bouncy, you would think a sophisticated machine like that has a bit more systems in place that anticipate a load change from the collective...

 

 

Edited March 22, 2022 by comcat

[MrNelz]

Isn't that what the collective anticipators are supposed to prevent? Not sure if they were fitted to the Apache modelled here but we had them on the UK D variant and on every other FADEC controlled heli I've worked on.

[iFoxRomeo]

It's exaggerated for such modern engines. I need to do more testing, but the first flight was disappointing and this twitchy torque is part of it.

[Raven (Elysian Angel)]

I was also under the impression that’s what FADEC is for

At the moment it’s manageable with smooth inputs: I only have some problems in the last few moments before touchdown, when the bird is quite twitchy indeed…

I tend to turn off transition mode and go to hover mode as soon as I dip below 40 KIAS or so do, since the FPM moving all over the place is very distracting.

 

Edited March 23, 2022 by Raven (Elysian Angel)
Typo

[exil]

Noticed that behavior too. Have never seen these torque jumps in any FADEC controlled helicopters. Nevertheless, as @comcat stated, the torque in- and decreasing behavior seems about right when inputting pedals for example. It's just the 'jumps' that seem a bit off here.