Rotor Rpm Vs Vne

[cap]

The 'beeping down' of the N2 has a valid purpose on some machines. All of this has come from the Vietnam era Hueys (NOT including the 212's) and led to some confusion about 'beeping down the N2'. Whatever the case, one should know when to do so and do it carefully and slowly as it is putting more strain on certain systems. It can be a way of reducing EGT and N1 on a hot day. The wind/breeze 45 degrees to the right of the nose, a 'beep down' to 97%-98% and a little right rudder as she 'augers out' can keep her performing well for a number of occasions. Done all the time.......well ya better find another spot to sling from or lessen the load. The bad side of that ability is it's mis-use. That same aircraft will get airborne with horrendously overgross loads on a cold winter day. The intention 'combat-wise' was to provide an area for one to go into to save one's ***........not to sling 10 drums, instead of 8, just to impress the customer. If you had to go into the N2 range all the time then it was only a matter of time before you went home to 'the World' in a zip-up body bag because it meant you were 'pushing your luck'.

[Heli-Raiser]

Cyclic M......thanks for the info, you may not be a Math major but you are light years ahead of my cyphering. Following your numbers, would you not be able to INCREASE your vne. The retreating blade would be going that much faster no? Hence stall later? Great stuff, thanks again

Going back to the original question it is my understanding that Vne exists because of the blade angles on the retreating blade. It is ture that the retreating balde would be going faster however this results in greater separation of air and a lower useful angle of attack. This is why retreating blade stall starts at the tip and moves in. The faster tip of the blade has a smaller useful range of angles to create lift. As the speed increases the useful angle of attack decreases until it reaches a breaking point...stall. This is also complicated by the advancing blade and the nasty vibrations and structural limitations related to the blade.

I do agree with Cyclic Monkey though...SLOW DOWN...WAY DOWN. :up:

[Big Duke 6]

I think that cyclic monkeys view on NR vs VNE is bang on ! His thoughts 0n NR and its effects on LTE are exactly how it was described to me by FlightSafety. It might be a stretch, but those limits that are posted in the flight manual are there for a reason. Somebody with a lot of time, money, and experience has played with these limitaions ( Company Test Pilots). My own personal experince has shown me that when NR decays, LTE does occur and the more you pull the worse it get's. Lowering the collective is a hard thing to do, when cumulo granite is rushing the cockpit. In my humble opinion, regardless of which helicopter you're flying, always know your limits as well as those of the aircraft. :afro:

[VERTICAL REF]

if you cannot lift it at 100%, then you sure as **** should not be trying to lift it at say 97 or 98%. at least not with an aircraft that i own!!!

 

so Big Duke, speaking of lifting. was the twin pac able to launch that aluminium fly tank FULL of jet A this summer? did the tank get smaller or its contents reduced?

[Big Duke 6]

Vert-Ref, Not to get off topic but the boys in green and gold don't use fly tanks, our production speaks for it's self. The NR vs LTE was in regards to ski operations. Thank GOD for powder landings. :up:

[VERTICAL REF]

so i guess you could'nt lift it eh?

 

you will have to tell me about that production over coffee some day! :up: when you all going sking?

 

 

my first comment was in agreement with what cap said...i think!

[Phil Croucher]

cyclic monkey - the quiet cruise is there because the 407 can actually fly quite happily at lower RPM - they apparently were increased to suit customer demand. Memory escapes me as to what the limits were (you weren't supposed to have it on below about 200 feet, I think), but it certainly reduced the noise complaints at the Falls. Not quite Blue Thunder!

 

Phil