Rotor blades hitting each other in flight

[aledmb]

hi,

 

i'm certain this is a noob question, but there it goes...

 

has anyone experienced rotor blades hitting each other while in flight?

i'm getting this frequently after trimming the controls.

 

the screenshots i'm sending are from a situation where i was flying

forward with the controls trimmed (forward pitch). note that the

blades are almost hitting each other after that trim.

 

that's dangerous, i know.

but then i trim it again and kabum, they hit each other.

 

hope someone can help me.

[Tango]

Hi,

 

Do the following:

 

* Avoid high speed manouvers

* Avoid pulling g and pulling collective

* Avoid rolling hard left at high speed

* Avoid yawing hard right then hard left at speed or with the collective pulled hard

* Avoid pitching hard with the collective pulled hard

 

After several blade collisions, you know when you're going to do it, and so you're more careful. The easiest way to avoid a collision is be smooooooooth.

 

When trimming, be sure to be quick sync'ing your centralization of the controls immediately after you release the trimmer. I highly recommend you put this on your stick, as it makes it easier to sync the action. After a bit of practise, you don't even know you're doing it.

 

How many ways have you broken it so far? :D I managed a new one today - slamming one lower blade into the boom. It got a bit shaky. ;) The really neat part was watching it fly off in front of me. Very realistic, and it left me thinking "OH **** there goes my rotor..........". :D

 

If you think you've done something that will result in a blade collision that didn't happen yet, drop the collective, and slow down (operating the cyclic GENTLY!).

 

Here is some background to the co-axial rotor design. Will hopefully explain why you experience what you do in certain manouvers etc..:

 

http://en.wikipedia.org/wiki/Coaxial_rotors

 

EDIT: Maybe not...

 

What you're seeing in your first pic is this: the advancing blade rises, and meets the retreating blade on the upper set of rotors, that drops relatively.

 

The faster you fly, the more lift is generated by the advancing blades, so the distance between the lower advancing blade and the upper retreating blade reduces.

 

In order to roll, you tilt the disc. To do this, you increase the lift generated on one side, and reduce it on the other. This has the effect of raising the advancing lower blades further still (if rolling left), and reducing the lift generated by the retreating blade on the upper disc, and in combination with high speed flight or lots of collective, and you get a blade collision!!!

 

Blade angles:

 

= slow, level flight

> high speed level flight

 

Best regards,

Tango.

Edited December 29, 2008 by Tango

[tusler]

Read the book for Free Online

 

You can read the FAA book for free here:

http://www.hothelicopters.com/faa_ac_6113b.htm

[Immermann]

Nice, I used PDF download for Firefox and converted the web pages to PDF.

[Shrubbo]

Aledmb, keep flying on the edge man, it's more fun :D

 

Anyway do you use a FFB joystick? If you don't like me then the following may explain why you chew up the rotors....

 

With a FFB joystick when you trim the stick stays where it is. For example you have a lot of pressure and the stick is a fare way over to the right and you hit trim it will stay a fare way over to the right.

 

WITHOUT a FFB joystick when you hit trim you have to get the stick back to neutral in a very short amount of time or else what you in effect do is trim the aircraft and then from the sims point of view instantly slam in however much you trimmed by.

 

A good way to see this is to take off and hover a couple of feet off the deck. Get it in a stable hover and then trim. If you recenter the stick in the correct amount of time then in effect the chopper won't move. If you fail the chopper will pitch forward. Now imagine that at critical speeds.

 

If you don't have FFB it is something you will just have to learn but it's not hard once you recognise what the problem is.

 

Hope that helps.

[uhoh7]

the worst is high speed, high pitch (watch that meter) and a quick roll.

 

When I'm really moving, i lower the pitch before I try anything fancy.

[aledmb]

Blade angles:

= slow, level flight

> high speed level flight

 

thanks for that tip!

i'm gonna print and glue this in front of my toilet!

never forget it! :smilewink:

 

You can read the FAA book for free here

 

thank you sir!

 

Aledmb, keep flying on the edge man, it's more fun :D

Anyway do you use a FFB joystick?

 

yeah Shrubbo, i'll try to keep that the way it's meant to be played...:joystick:

i have a cougar and already have disabled FFB in the "Producer.cfg"

file, because of my FFB wheel, so now i have the trim function working.

 

thank you all for you replies.

your help is being extremely valuable!

[Mugatu]

Man this is one chopper that needs to be FBW :)

[ARM505]

Definitely. FBW would allow pilots to safely unleash this things full potential. See how quickly those Commanche prototypes could roll?

[aledmb]

well, after a few days working on it, i can't help but ask for help

again...:helpsmilie:

 

one strange pattern i noticed with this problem i'm having is that

the blades only lean towards each other on the right side of the

chopper.

 

i tried to make them contact on the left side several times, but

no success, even trying to roll to the other side. they always

go for a hit in the right side.

 

i also ran some tests in game to see if my controllers were

calibrated, and they're all ok (collective, stick and rudder),

as you can see by the track file attached.

 

please if you could look at this video on youtube...

http://www.youtube.com/watch?v=2GLuubKUUys

 

.

calibrado.trk

[Vortex]

Yes the lean to the right is normal.

 

It's a problem of having two blades spinning in the opposite direction.

 

The advancing blade has to flap up to reduce the angel of attack, while the retreating blade has to flap down to reduce the angle of attack. They do this because the advancing blade is producing more lift given it's extra speed in forward flight.

 

Now why do they do this? Because if they didn't the aircraft would constantly bank towards the retreating blade (like a plane with one wing producing less lift than the other).

 

It's called "Flapping to equality". The faster you go the more they have to flap to equality.

 

Now add another blade ging the other way and you have problem, The bottom blade goes up, and the top blade goes down.

 

Simply keep from exceeding VNE (the warning light and alarm that comes on just before you have a mid air collision with yourself) and do not use the controls to their full extent, enter all movements smoothly, and when travelling at high speeds be careful of how much collective you use.

Edited December 31, 2008 by Vortex

[aledmb]

now i see the other posts have told me the same thing...

and i didn't hear to them! so, my whole problem is not

controlling airspeed.

 

i'll try to give more attention to the collective and doing

smooth movements with the cyclic now.

 

thank you very much.

thank you all!

[fox_111]

So this little buzer that seam to come randomly, is a warning saying my maine rotor is about to crap? (Buzzer that don't light the master warning light)

 

I just screwed a flawles CAS mission today. I was egressing home at max speed and as I trimmed the aircraft in a tight turn, my blades came appart... That's frustrating!

[Vortex]

Any warning buzzer must never be ignored.

 

/Reminds me of a fairly ordinary pilot I know who has a PPL, he was in a borrowed plane and was on final for landing when a warning buzzer came on. Everything seemed fine to him so he just continued the approach. Luckily for him just as he approached the threshold he realised he hadn't lowered the landing gear :doh:

Edited January 1, 2009 by Vortex

[graywo1fg]

one thing to look at is your 2 lights above your hud when your engines are over torqued... 2 yellow ones will turn on and that means back off a little on the collective and if you dont and then the Rotor RPM warning comes on its really REALLY bad because they are about to hit! :D the higher pitch of the rotors may very be more lift of course but introduces more drag slowing them down and flaping up more. have fun ;)

[Tango]

The two manouvers that guarantee a blade collision are:

 

* Hard left roll

* Hard right yaw

 

at speed and with collective pulled. That's just how it is.

 

To help alleviate a collision, just drop collective during the manouver, and you should be OK! Altitude lost will occur, but can't be helped unless you want to bleed off speed instead.

 

Best regards,

Tango.

[aledmb]

The two manouvers that guarantee a blade collision are:

 

* Hard left roll

* Hard right yaw

 

at speed and with collective pulled.

 

to me, depending on the trimming applied, they will

collide even with smooth rolls to the left (as in the

video) but, as you said, that guarantees the show.

 

i'm doing fine for 2 days now. the blades aren't even

getting close to each other. what i do is constantly

watch how and when i'm using the collective.

 

thanks a lot for your help!

[Vortex]

No worries. In real life you get to go to ground school and have an instructor go along for the ride to keep you out of trouble, this sim shows exactly why that is a good idea.