Rotor Brake Application Nr
 

SP, a slight amplification of your longer post on the subject.

As I am sure you are aware, types rated for naval shipboard applications have an emergency stop mode in that in an urgent situation the rotor brake can be engaged at 100% Nr. This is due to the need to accommodate sometimes very difficult conditions on rolling/pitching ships in strong gusty winds.

Examples are the naval EH101, the Sea King (SH3) and the Sea Hawk (SH-60). The requirement for this is described in a USN specification, SD-24L.

Unfortunately, I don't believe there is a web copy of that specification.

Rotor Brake on Startup
 

Shy,

Didn't we start engines with the brake on in certain wind conditions in the Puma?

I know the Ferret did once on a ground run, but didn't mean to go that far! Cooked the thing.

CG

The H-53 was designed as a naval helicopter for shipboard ops. Both (or all three) engines could be started with the rotor brake on, then released to minimize the time at slow rotor rpm in gusty winds. On shutdown there was a minimum speed for brake application to avoid suddenly stopping the rotor head. It could even be applied with an engine still running.

Unlike the disk break setup commonn on other types, the huey brake had a spline directly into the gearbox. Bell's idea was to only use the brake at at low rpm. During a rapid shutdown on a UH-1 I found out that the rotor brake was indeed more rugged than the transmission gear it slowed. I got to see the chewed up gear myself when they replaced the gearbox.

CG, Yes, it was done in gusty winds to help prevent blade sailing, but iirc it had to be released by 40% Ng on the first engine.