Transmisssion Ratings for Helicopter Gearboxes 1

[Schuyler]

How are helicopter gearboxes (i.e., main transmissions, tailrotor gearboxes, etc.) typically rated (i.e. Horsepower, Torque, etc.)? Please explain. I know they can vary, however, what is a typical rating for systems currently fielded.

 

[Carburize]

I would check on the American Gear Manufacturers Association (AGMA)web site at

http://www.agma.org

to see if there are any relevant standards published.

 

[ferdo]

Hi,

Maybe this link will help you

http://www.tpub.com/air/10.htm

Regards
Fernando

 

[Tads]

When you say rated, I'm assuming you are talking about actual performances? Usually due to the rotation speeds being within a small band, horsepower isn't usually appropriate. Therefore, torque is often quoted for gearbox performances, with a maximum torque limitation placed on the component.

There are numerous ways to qualify this rating as well, and that's a whole other story!

 

[Sparweb]

I've recently been through the gearboxes of a 205A-1, so the numbers are fresh in my mind. The engine delivers take-off power of 1250 HP at 6600 RPM. The main transmission reduces the speed by a factor of 20.37, therefore the main rotor can spin at up to 324 RPM, but can go as low as 290 or so. An auxiliary gearbox reduces the engine speed by a factor of 4.0 to the tail-rotor transmission, therefore it spins at 1650 RPM. The engine is capable of delivering more power that I quoted above; it's the airframe that can only withstand 1250 HP. Get a 212, and you can use 1350 HP because the tail boom is beefed up, yet the transmission is virtually identical.
I have estimated that the main transmission is up to 90% efficient, based on my rough calculations of hover performance, but don't quote me on that. Maybe stick with 80% to be on the safe side.

You might get a few more answers if you post the question on the rotorcraft forum, too.


STF

 

[buni44]

HP and RPM (engine(s) intake and main rotor shaft)or main rotor RPM and de-multiplying factor.

a medium tonnage ussualy has a 4000 HP with main around 300 rpm and two engine couplings rated between 20,000 to 50,000 rpm (just for example)