Jump to content

Recommended Posts

Posted

On the knowledge exam, there's a question:

 

If the pilot experiences ground resonance during rotor spin-up, what action should the pilot take?

 

The correct answer is "Close the throttle and slowly raise the spin-up lever."

 

Am I just reading this really really wrong? What exactly is the spin-up lever? The Rotorcraft Flying Handbook doesn't even use the term "spin-up lever" (so much for definitive source). Raising the collective (=spin-up lever????) is wrong (decreasing rotor RPM would decrease centrifugal force, decreasing the forces acting to restore rotor CG...I think). That logic makes the 3rd answer ("Make a normal takeoff immediately") look less wrong.

 

thx.

Posted (edited)
On the knowledge exam, there's a question:

 

If the pilot experiences ground resonance during rotor spin-up, what action should the pilot take?

 

The correct answer is "Close the throttle and slowly raise the spin-up lever."

 

Am I just reading this really really wrong? What exactly is the spin-up lever? The Rotorcraft Flying Handbook doesn't even use the term "spin-up lever" (so much for definitive source). Raising the collective (=spin-up lever????) is wrong (decreasing rotor RPM would decrease centrifugal force, decreasing the forces acting to restore rotor CG...I think). That logic makes the 3rd answer ("Make a normal takeoff immediately") look less wrong.

 

thx.

 

Pure guess: The Hughes 269A had a lever, right side of the pilot's seat, that you pushed down to tension and engage the drive belts. Once the rotor was matched up to the engine, one locked it under a detent/bracket. As obscure as the FAA's question writers can be, it's hard to believe that that's what they're referring to.

Whatever the question's putative "correct" answer, in the real world the only good response to ground resonance, dynamic divergent excitation, etc., is quit what you're doing as quickly as possible: If you're landing, takeoff again; If you're accelerating the rotor, stop. You can't, I repeat, you CAN NOT "fly through" the problem. As little as three complete turns of the rotor can destroy the airframe. That's less than a half of a second in an Astar, and in smaller rotors, less.

Edited by Wally
Posted (edited)

That is pretty wild! I was looking at that same question last night and I thought what in the heck is the "spin-up lever?" I reckon that is just one of those questions the FAA uses to prove you memorized the stuff they wanted you to.

 

Just a hint if you are working on your commercial written... Buy you a CX-2 if you don't already have one. They are awesome little gizmos that are tremendous help for just about every calculation that is on the written.

 

RotorRunner

Edited by RotorRunner
Posted

I'm not 100% sure, but I think that a "spin-up lever" is used on a Gyroplane to get the blades turning, or spun-up, faster. They do refer to it in the handbook, but they call it a Mechanical Prerotator instead, go figure. Anyway, If your're taking the Rotorcraft, Helicopter exam, doubt you'll see it.

 

Clark B)

Posted

Thanks all. It's one of those questions that if i do see it i've memorized the answer anyway, but wanted to know if i was missing something important.

 

in the real world the only good response to ground resonance, dynamic divergent excitation, etc., is quit what you're doing as quickly as possible:
Posted
I'm not 100% sure, but I think that a "spin-up lever" is used on a Gyroplane to get the blades turning, or spun-up, faster. They do refer to it in the handbook, but they call it a Mechanical Prerotator instead, go figure. Anyway, If your're taking the Rotorcraft, Helicopter exam, doubt you'll see it.

 

Clark B)

 

Don't be so sure. One of my students saw it on his test 2 weeks ago. Good thing he asked me about it when he was studying for the test. The spin up lever is the "mechanical prerotator" mentioned in the rotorcraft flying handbook.

Posted
Don't be so sure. One of my students saw it on his test 2 weeks ago. Good thing he asked me about it when he was studying for the test. The spin up lever is the "mechanical prerotator" mentioned in the rotorcraft flying handbook.

 

Found it. It's not discussed in the helicopter section of the RFH...does this mean that when I sit for the PPL(H) written exam I should know the material from the gyro section?

--c

Posted
Found it. It's not discussed in the helicopter section of the RFH...does this mean that when I sit for the PPL(H) written exam I should know the material from the gyro section?

--c

 

I wouldn't read the section unless it interests you. Just study the questions and answers for the gyrocopter questions.

Posted

i'm thinking the same thing as RotorRunner. if the spin up lever is in fact part of the gyroplanes anatomy why would it be involved in a ground resonance question. i didn't think there were any gyro's with fully articulated rotor systems.

-c

Posted

oh wow, i'll have to look into that. i had no idea. seems to me like all the extras that come with a fully articulated system would weigh the little gyro down....

Posted

Strictly tongue in cheek, but my correct answer would be, don't fly three-bladed helicopters!!

Posted (edited)
i didn't think there were any gyro's with fully articulated rotor systems.
The first successful autogiro by Juan de la Cierva was the first fully articulated rotor system, ever. It's actually thanks to Cierva that we have helicopters because he solved the problems that were limiting helicopters of the era. The next group of successful helicopter pioneer's were those with experience with autogiros, including Breguet and Focke. Edited by Linc
  • 5 years later...
Posted

This question must have been created a really long time ago. There is a description of what a "spin-up lever" is on the wikipedia page below for the McCulloch J2, of which apparently there were only a grand total of 83 ever in existance, all built in the 60's and early 70's. Nice that the FAA confuses everyone for decades with something so outdated and arcane.

 

http://en.wikipedia.org/wiki/McCulloch_J-2

 

If you are interested in ground resonance in a "real" helicopter, here is a good writeup re the Chinook

 

http://www.chinook-helicopter.com/Fundamentals_of_Flight/Ground_Resonance/Ground_Resonance.html

Posted

Excellent topic, a lot of great replies. I enjoyed reading all, thanks guys (and gals if it applies). Keep up the good work.

Posted

WHY a Gyro Question For Helicopter test ?, no the same flying technique.

Does the same licence cover both in US ?

  • 3 weeks later...
Posted

500E- No gyro's are actually a different written exam as far as I know......but I never got that certificate!

Geez, I remember this thread from 5 years ago, surprised there wasn't some smart ass reply in there from me at the time.....cause I sure was thinking it!

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...