Camarillo Airshow!

[Mike]

Yeah, there are a bunch of aerodynamic phenomea happening when a helicopter transitions from a hover into forward flight. The disc gets more lift, etc. etc.
But without going too much into that, one thing that happens is a vibration which you usually feel more with rigid rotor systems and when the gearbox is mounted fairly rigid to the frame. The Astars and Jet Rangers have rubber mounts which the gearbox sits on. On the BO 105 where everything is tied to the airframe as tight as possible with no give I am sure you will feel the ETL vibration a lot more pronounced....

[fireflyr]

Can ETL cause any problems?

[Mike]

No, not really. Part of it is the vortices that are at the blade tips (just like wingtips) which in a hover "surround" the helicopter in a hover. When you move into forward flight they get "blown" towards the back and move through the airframe as they do that which causes a vibration. Then there are a few aerodynamic things, i.a. lift and angle of attack changes, which will have an effect on the blade and therefore the gearbox it is essentiallly attached to.
 If I get some extra time one of these days I'll try to explain it in more detail.

But it's pretty much "normal" for every helicopter....


Like the fat back kid says in the "Me, myself, and Irene" movie:
"How hard can it be? It's just lift versus drag and rotation!"     
(one of the most stupid movie line EVER!!!!!)

[Mike]

So, the Red Bull helicopter has been repainted. . .

BUT:

It again got that really important addition !!!!!
not bad, huh?!?!

Did anybody see the show at the Nellis AFB ??
Apparently the real Chuck outdid himself this time . . .

[Mike]

Check out what Chuck is up to for Christmas:

http://www.flyingbulls.at/xmas/xmas06-1.html

you have to double-click on the "packages" when the animation pauses....
(oh, and the show might want you to close the forum, just do it, no big deal....)

  Merry Christmas!

[Frank N. O.]

Lol, nice little thing, thanks for sharing the link

Also found some helicopter info on the BO from the website that follows, and that they have a Cobra helicopter! 
Chuck is cool, if we get the Focus then I got just the spot for a Capt. Chuck sticker under the Focus logo on the left of the big trunk, if only I could get one sent over.

Frank

[undatc]

I know I asked awhile ago in another thread, but I think it got missed by Mike or whoever knows...

Why is it such a big thing for helo's to go inverted, or do barrel rolls?  I know the Apache was the first to be able to, but hadnt heard of other ones that could, till now.  I understand the principal of how planes do it, angle of attack and chamber, isnt it the same, and as you can control the pitch of your blades, shouldn't it actually be easier for you to do it?  Given all of the controls would be reversed, i think....

[Baradium]

I know I asked awhile ago in another thread, but I think it got missed by Mike or whoever knows...

Why is it such a big thing for helo's to go inverted, or do barrel rolls?  I know the Apache was the first to be able to, but hadnt heard of other ones that could, till now.  I understand the principal of how planes do it, angle of attack and chamber, isnt it the same, and as you can control the pitch of your blades, shouldn't it actually be easier for you to do it?  Given all of the controls would be reversed, i think....

Without having any actual first hand experience...  all that torque is going through that little (albiet strong) rotor shaft, that's a lot of stress to be asking.  Additionally, instead of being close to in line to the CG like with an aircraft, the rotors are *above* the CG in a helo.  This will require much more power to overcome, and then you have all the lift created well below the CG (read: less stable than before!)

I think it's a torque issue (rotationally about the axis) that gets choppers in going inverted.  It just takes so much torque to get the CG to go above the rotor blades...

[Mike]

I know I asked awhile ago in another thread, but I think it got missed by Mike or whoever knows...

Why is it such a big thing for helo's to go inverted, or do barrel rolls?  I know the Apache was the first to be able to, but hadnt heard of other ones that could, till now.  I understand the principal of how planes do it, angle of attack and chamber, isnt it the same, and as you can control the pitch of your blades, shouldn't it actually be easier for you to do it?  Given all of the controls would be reversed, i think....

Let me try to answer this as best as I can. Rotors are usually designed only for positive loads. It is actually possible to do a flip in a bunch of helicopters (I say "a flip" because it's not really a loop, the helo rolls and then just falls through until it hopefully rights itself before hitting the ground). But you couldn't hover upside down like in a RC helo because you would need to reverse your collective to pitch the blades down instead of up.
In my aircraft (Panaca Jane) the problem would be the hydraulics. They would lock up during such a maneuver because they were not designed for those high loads (experts call it "servo transparency").
On most of the others I would simply be afraid of my blades touching my airframe at one point or another during the maneuver. The BO 105 is designed with a very rigid rotorhead and the gearbox is attached by mounting it directly to the airframe. In most helicopters, the gbx is mounted on elastomeric bearings for a little give and a smoother ride and the blades usually like to flap more....
There are other things as well, low G considerations for example where in a 2 bladed system you could break the mast and have the rotor depart the airframe and so on...

[undatc]

I know I asked awhile ago in another thread, but I think it got missed by Mike or whoever knows...

Why is it such a big thing for helo's to go inverted, or do barrel rolls?  I know the Apache was the first to be able to, but hadnt heard of other ones that could, till now.  I understand the principal of how planes do it, angle of attack and chamber, isnt it the same, and as you can control the pitch of your blades, shouldn't it actually be easier for you to do it?  Given all of the controls would be reversed, i think....

Let me try to answer this as best as I can. Rotors are usually designed only for positive loads. It is actually possible to do a flip in a bunch of helicopters (I say "a flip" because it's not really a loop, the helo rolls and then just falls through until it hopefully rights itself before hitting the ground). But you couldn't hover upside down like in a RC helo because you would need to reverse your collective to pitch the blades down instead of up.
In my aircraft (Panaca Jane) the problem would be the hydraulics. They would lock up during such a maneuver because they were not designed for those high loads (experts call it "servo transparency").
On most of the others I would simply be afraid of my blades touching my airframe at one point or another during the maneuver. The BO 105 is designed with a very rigid rotorhead and the gearbox is attached by mounting it directly to the airframe. In most helicopters, the gbx is mounted on elastomeric bearings for a little give and a smoother ride and the blades usually like to flap more....
There are other things as well, low G considerations for example where in a 2 bladed system you could break the mast and have the rotor depart the airframe and so on...

So then, wouldnt it simply be a matter of making a system that allowed more adjustability for pitch in the blades (upwards and downwards), making the rotarhead further away, stronger, and with a more powerful engine.  Hmmmm, shouldnt be to hard.....

[Mike]

Oh yeah...definetly!

All you would have to do is design a new gearbox, a special rotor head, stiffer blades, a new airframe which can take these new loads, a fuelsystem and engine that can run upside down, find out how to reverse the cyclic and make it go down as well instead of just up, of course add more powerful hydraulics, ground test it,  flight test it, train pilots, get it approved . . hmmm

can't be that hard... I mean especially since it's been done before with the RC helos
heh heh . . .


Maybe Chuck and Julio can come up with something.... 

[Panzerrat]

Even if you designed the helioflipter they way you mention, wouldn't rolling 'er onto her back be a real "Mother!" event?

[undatc]

ah hell, if we can deep fry ice cream, and make a ski slope in kuwait, we can build us a chopper that can do it.

[fireflyr]

ah hell, if we can deep fry ice cream, and make a ski slope in kuwait, we can build us a chopper that can do it.

Ain't that ski slope in Bahrain?

[undatc]

could be, all i know is that its in the middle east somewhere, and figured it was in kuwait.