Hard to understand how it could have been in limits if the brake was unable to stop the rotation. How was that certified? Shutting down outside limits with another technical problem is an ever present dilemma, with no guarantees how it will go. But, in limits? You would reasonably expect to be able to stop the rotor!

I’ve seen a situation where the wind was so strong that after shutting down the engines the blades continued to autorotate well above the maximum rpm for the use of the rotor brake.

Interesting. Sikorsky rotor brakes (S61, S76, S92) may be applied in emergency immediately after engine shutdown with NR still at 100% / 107%, and the AW139 permits application at 90% NR in that situation.

Yes but they work...

They can also be applied with the engines running (as you know)

Perhaps it would be more accurate to state that the wind strength reported to the crew was within the shut down limits. As PlasticCabDriver mentions, the rotor brake itself on the H175 isn't the best. Sometimes you select it on and don't perceive any change in the rate of Nr decay!

Apologies if this can't be viewed without a subscription:

Video: Footage shows moment Storm Otto rips blades off helicopter

I’m guessing it’s the same video I posted earlier?

Newton Three!

Update from the AAIB:This statement provides an update on the AAIB investigation into a serious incident involving an EC175 B on the Elgin Platform in the North Sea on 17 February 2023.

The aircraft had shut down on the platform due to a technical fault, but a problem with the rotor brake meant the rotor blades continued to rotate slowly, preventing the application of the rotor blade tie downs. The platform was in the path of Storm Otto, with associated high winds resulting in four of the five main rotor blades breaking off the aircraft. No one was injured.

The AAIB investigation has focused on the cause of the rotor brake failure and the breaking of the rotor blades. It has also looked into operational factors, including weather reporting. The investigation has identified issues with the flight recorder on the aircraft and is working with the aircraft and recorder manufacturers to rectify this.

The full report will be published by the AAIB when complete.

Interesting on the issues with the flight recorder, any ideas on what this could be?

Just to update, MCSH returned to the skies on Monday after 415 days and a lot of repairs! Including a new tail boom!