helo question on ASTB

[mimisoko9]

I am re-taking the test tomorrow AM (recruiter messed up my test - not my fault) and I recall a helo question to which I didn't know the answer.

The study guide reviews a plane stalling and I've since done some following up on why that happens, but I can't figure out under what conditions a helo is most likely to stall.

It's been a month, but I think the options were something like: when it's in a steep climb, when it's hovering sideways, when it's hovering, or when it's moving forward a high right with its nose down.

Can anyone shed some light on this?

Thanks.

 

[kdmiller8251]

I would thing that it would stall when it is sideways... A helo generates lift thru the rotors and the angle of the rotors to the ground.. If the rotor are at a 90 degree angle which I am taking as sideways, there would be no lift thus creating a stall condition

 

[WT]

If I remember the question correctly, it is asking when will a helicopter reach a "blade stall"? (that might not be in the question though)

-Answer for a blade stall: When the helicopter has reached the maximum forward speed at which the retreating rotor blade can no longer sustain lift.

An airfoil needs to have enough airflow to create lift, since a helicopter has spinning blades at some point the blade is moving in a direction that is opposite the movement of the aircraft. As long as the spinning blade is moving fast enough to create lift, no problem. Once the aircraft is moving at a rate that the "backward" moving rotorblade cannot sustain lift, the helicopter will stall.

I know that this sounds technical, but if you read it a couple of times you should be able to understand it better.

--WT

 

[mimisoko9]

WT-

That makes sense, and I remember clearly that one of the options was something about moving forward at a very rapid rate. Don't remember the phrase "blade stall," but it's probably to what it was referring.

Thanks a lot, especially if I see it on the test again tomorrow!

-Mimi

 

[Q-ball]

It's called retreating blade stall, and WT pretty much got it right.


Q

Marine Helo Pilot