Blades clashing ( Again, but different reason)

[mrtube]

Hi Dudes, wonder if you can give me some help again. Been doing lots of practising, getting to know how to fly and use the autopilot system, trim etc, and am getting it slowly.. However, i am being plagued by sudden snapping of the rotors. In a previous thread, I was given some great advice as to how avoid this, in particular, paying attention to the red and yellow warning lights ( yellow, reduce collective, Red, pitch nose up ) This works great. However, I keep getting the blades snapping in what seems like perfectly normal flight, not manouvering hard, usually in a straight line, with no prior warning lights. after a very minor input. Sometimes, but not usually, one or other of the engine limiter lights may come on - what causes this ? I am also being pretty subtle with my control inputs, so dont think its me being hamfisted. Any advice would be gratefully received as its driviing me nuts!! Thanks, Mark

[jctrnacty]

Just be carefull, avoid to exceeding speed over 250 and to hazardous manouvres.

[Nate--IRL--]

Left banking or right rudder (or even applying right rudder and left bank trim to fly straight) will cause the blades on the right hand side to move closer together. If you are moving at high speed and/or raise the collective sharply at high speed, the likelihood is that the a blade clash could occour.

 

The yellow warning light indicates low rotor RPM (less centripetal force - more flex of blades = Bad)

 

The Red warning light is indicating that you are flying too fast and the blades could intersect, with the above conditions.

 

Nate

 

Edit - Simple answer never fly over 270 Indicated airspeed (guage + shkval reading) at ground level, reduce this as you fly higher.

[mrtube]

thx guys, but my problem is I was not doing either of those things as far as I can remember. And as I said, had no warning lights first, I will try some more flying and note carefully the speed, perhaps see if I can post a link to a track, any other ideas please feel free to help.. thx, Mark

[Nate--IRL--]

You won't get warning light unless you are over MAX IAS or have low rotor RPM. There are plenty of other opportunities to clash blades, without these two conditions.

 

A track would be ideal to diagnose the problem.

 

Nate

 

Edit - it should be noted that if you are flying straight and level at say 270kph IAS you will have considerable Left bank and right rudder trimmed in, to maintain straight and level flight. So if you bank left or use right rudder even a little bit at these speeds - clash.

Edited March 1, 2009 by Nate--IRL--

[mrtube]

Hi guys, just re flew the mission, managed a 45 minute flight with no incident, apart from when I landed, which was not too tidy, no crashes! I kept the speed between 200 & 250, and was very gentle. Seemed to work, thx

[WynnTTr]

You checking your yaw with the ball? You'll probably find that you're yawing excessively to the right, and cos of rudder corrections, probably didn't know it.... until you make that minor attitude change that's equivalent to the proverbial hair.

You shouldn't have to treat the BS gently. It can be thrown around, even do some acrobatic moves.

[tusler]

Ok Here is what I found. I was flying to fast "with the rotors on auto".

Thats the key. set your throttle to a good key press for you, I think it is PageUp and PageDn default. Now when you get going to fast reduce the throttle (rotor rpm) I have found coming down from cresting a mountain I can attain very high speed without crashing rotors just by reducing the speed of the rotors. Even flying level if you start to get any kind of warning dropping rotor speed instantly helps, of course you have to feed the spped back in slowly inorder to recover and continue.

Hope it helps.

[slug88]

Ok Here is what I found. I was flying to fast "with the rotors on auto".

Thats the key. set your throttle to a good key press for you, I think it is PageUp and PageDn default. Now when you get going to fast reduce the throttle (rotor rpm) I have found coming down from cresting a mountain I can attain very high speed without crashing rotors just by reducing the speed of the rotors. Even flying level if you start to get any kind of warning dropping rotor speed instantly helps, of course you have to feed the spped back in slowly inorder to recover and continue.

Hope it helps.

 

decreasing rotor speed is the last thing you want to do here. Increasing the rpm will increase the centripetal force on the blades, which pulls them out to the sides, thus reducing flapping. This is why you need to lower collective as you build speed; lowering collective increases rotor rpm. If the method you're describing actually works, then there is something seriously wrong with the game.

 

Note also that the blinking yellow RPM warning is actually a *low rpm* warning. It's telling you that you need to increase rotor RPM.

[AlphaOneSix]

During extended descents, it is possible to overspeed the rotors (noting that this does not necessarily have anything to do with them colliding with each other). That's why there is a switch on the collective to lower the RPM of the rotor.

 

“ОБОРОТЫ” Control selector for re-adjustment of the free-turbine (rotors) RPM governor. To low [NUMPAD - + RALT] and to nominal [NUMPAD + + RALT].

 

It's normally set to nominal, but during long descents you should switch it to low to help avoid rotor overspeeds. At the end of your descent, switch it back to nominal.

 

It also goes without saying that unless you have an engine failure or a governor failure, you should never move the throttles from the AUTO position during flight, ever.

[EtherealN]

That overspeed during descent, would I be correct in assuming that it is caused by conservation of angular momentum?

[sobek]

That overspeed during descent, would I be correct in assuming that it is caused by conservation of angular momentum?

 

That causes very little differences in total rotor rpm and affects mostly single blades, IIRC. The effect is caused by the same phenomenom that allows autorotation. Just floor the collective during a highspeed flight and pull on the cyclic. As air starts to flow upward through the rotor instead of downwards, the rotor rpm will increase despite the EEG lowering ggt rpm. This happens only for a brief period until your forward speed is too low, but it is noticeable.