Yawing and tilting on the ground?

[Asset]

Hi pilots,

I am trying to hone my Mi8 skills. And what better place to start other than the start(up)? :lol:

 

How do you get the Mi8 into a steady state to start taxing and lift of without tilting over?

During startup when increasing the throttle to full to get 96% rpm and engage the automatic rpm govenor, the helo will yaw to the right. I either have to apply significant pedal or use the wheel brake to prevent that. During takeoff I have to apply significant right pedal to compensate for the increased torque, so opposite of what I originally applied to stop the yawing.

Also when taking off the helo has a tendency to wanting to fall over to one sight and I do not understand why. What are the reasons, what are the forces involved?

The manual says the following:

As the helicopter is initiated into motion on the ground, during taxi, ground run, and at the moments of takeoff and touchdown, conditions may develop in which the
helicopter will tend to roll on its side with respect to an imaginary diagonal between
the nose gear and one of the main gear wheels, a condition known as a dynamic
rollover.

aha, sounds like my problem. Go on...

When positioned on the ground, the forces acting on the helicopter with running
engines are gravity, main rotor thrust, tail rotor thrust and the ground reaction forces
acting on the wheels. The tilting forces that may result in a dynamic rollover are tail
rotor thrust, lateral components of ground reaction, lateral forces acting on the
helicopter during taxi turns and, in case of incorrect pilot actions, a component of
main rotor thrust. The corrective forces are the vertical components of ground
reaction and, in case of correct pilot actions, a component of main rotor thrust.

As main rotor thrust increases, the vertical component of ground reaction forces is
reduced and its stabilizing effect weakened. The addition of any roll angle shortens
the arm of this force and further reduces its stabilizing effect. Crosswind, low
stiffness of the landing gear, a high center of gravity (CG) position - all contribute to
a potential dynamic rollover condition.

I do not understand the part with the forces, in particular the reactive ground forces. Isn't that just the force that counteracts the forces I inject with my rotors? If I pull the cyclic to one side and the grip of my wheels on the ground prevent me from sliding over it. That is what I would consider reactive forces. So if I trim my main rotor slightly aft-right I compensate its built-in trim for straight forward flight and the thrust vector should be straight up and not pull me into a tilt, right? (assuming no wind) However this doesn't really to do the trick and the force that is trying to tilt my helo seems pretty strong, requiring a lot of counter-cyclic.

 

What are your secrets to professional lift-offs and looking good doing so?

[Pocket Sized]

Some general info/tips for takeoff:

 

The tail rotor produces a significant amount of thrust when the pedals are centered (enough to hover with a lightly loaded aircraft), this lightens control forces during normal hover and cruise operations. It does, however, push you around during ground ops and autorotation so a bootfull of rudder is often needed to compensate.

 

The only defense against this dynamic rollover behavior is muscle memory. I seriously have no idea where I push the stick prior to liftoff, its second nature at this point.

 

Spooling the rotors should be the last step in your startup aside from enabling pitch/roll autopilot. Be ready to start "flying" as soon as the rotors begin accelerating from idle speed. I'd also recommend leaving the parking brake on until liftoff/taxi.

[cthulhu68]

One thing that helps is pre-setting your "hands off position" with trimmer to counter the forces of the helo when taking off.

Bring up the controls indicator (R.Ctrl+Enter)

Press trimmer, pull back and to the right a little and add a little r. rudder, and release trimmer

This gives you a little better starting point

[Asset]

Bring up the controls indicator (R.Ctrl+Enter)

 

 

 

Hmm, I thought that much. Thing is I play in VR and there is no controls indicator available.

 

So I guess it is all down to setting parking brake, spool up, once ready for taxi put some load on the rotor, and then guess how much to trim the rotor aft-right and pedals right before releasing the brake. Practice makes perfect.....

[gospadin]

Hmm, I thought that much. Thing is I play in VR and there is no controls indicator available.

 

So I guess it is all down to setting parking brake, spool up, once ready for taxi put some load on the rotor, and then guess how much to trim the rotor aft-right and pedals right before releasing the brake. Practice makes perfect.....

 

IMO, you should be releasing the brake before you add any collective. Better to roll or rotate than to tip over.

 

And you aren't really guessing about left/right pedal input, you just apply whatever input you need to counter the yaw. Same with applying collective, if the helo starts to pitch or roll, just move the cyclic.

[Pocket Sized]

+1 to what gospadin said.

 

It doesn't matter where the controls actually are, just move them as necessary to make the aircraft go where you want. (This helped me a ton when transitioning to real flying :D )

[Cibit]

+2