correct as-is tilts to left when lifting

[skypickle]

I understand that cyclic forward would precess the rotor disc to the leftresulting in left tilt. However, when on the pad and gradually adding collective with a completely neutral cyclic, the Apache tilts to the left. Why would this be?

[Raptor9]

13 minutes ago, skypickle said:

I understand that cyclic forward would precess the rotor disc to the leftresulting in left tilt.

I think there is a misunderstanding of how gyroscopic precession affects helicopters. If I apply forward/aft cyclic, the input is not applied to the rotor system in the forward/aft portions of the rotor system. If it was, this would indeed cause a rolling motion, rather than a pitching motion. However, rotor systems are intentionally designed so that cyclic inputs are applied to the rotor system 90 degrees prior to the desired effect, negating the effect of gyroscopic precession.

You're probably seeing the translating tendency of the AH-64D, which is caused by a combination of the tail rotor thrust and the torque of the counter-clockwise-spinning main rotor. The aircraft wants to slide to the right as it is getting light on the wheels, but there is still some friction from the wheels on the ground that is holding it in place.

You can see a visual explanation of this here: https://www.youtube.com/watch?v=Jr_t9JGlPEw

[skypickle]

thank you for the link. My understanding is the the flight management computer is trying to counteract the translating tendency by tilting the rotor left.

[Raptor9]

1 hour ago, skypickle said:

My understanding is the the flight management computer is trying to counteract the translating tendency by tilting the rotor left.

This isn't the case in the AH-64D. The pilot compensates for translating tendency by applying left cyclic, which tilts the rotor disc to the left, resulting in a slight left bank.

[DmitriKozlowsky]

Aerodynamically that is correct behavior.

 

[skypickle]

9 hours ago, Raptor9 said:

This isn't the case in the AH-64D. The pilot compensates for translating tendency by applying left cyclic, which tilts the rotor disc to the left, resulting in a slight left bank.

The tilt starts before I apply any cyclic. Hands off the stick, apply collective and you’ll tip over to the left

[Raptor9]

47 minutes ago, skypickle said:

The tilt starts before I apply any cyclic. Hands off the stick, apply collective and you’ll tip over to the left

I misunderstood what you were saying because I'm not seeing the behavior you are describing. It sounds like it might be a controller input issue. Bring up the Controls Indicator overlay [default is Right Ctrl + Enter] and see where your input position is. It might be offset for some reason.

[McGraw]

You say on the pad but are you on a slope? Both brakes off?

[kgillers3]

I’d recommend including a track so people can see what’s occurring along with what your controls are doing.  It should help with clearing up the confusion of terminology and assist you with getting a more refined answer  on what’s going on. 

[skypickle]

sorry i dont know right from left. but here is the track. hot start in caucasus. controls visible in top left.

 

raising collective gradually.

apply some left boot for antitorque

tips right over.

apache.trk

Edited July 10, 2022 by skypickle

[iFoxRomeo]

13 minutes ago, skypickle said:

raising collective gradually.

apply some left boot for antitorque

tips right over.

The tail rotor pushes you to the right. But you don't lift off, you are just making the Apache light on the wheels and thus provoke a rollover. The right wheel and the tail wheel act as pivot here.

You need to clearly lift off the ground, or counter this right translation with cyclic to the left.

Edited July 10, 2022 by iFoxRomeo

[skypickle]

@iFoxRomeothank you. got it