Questions raised by Henra and RG:
Let me add some background ( think I've covered this before but probably in a PM. If so, apologize for the repetition ).
The US Army Request for Proposal for UTTAS had a requirement that the vehicle be able to fly at the speed for best endurance in level flight and at a sideslip angle that was 20 0r 30 degrees ( and I cannot remember which ). Tough requirement, and if you recall the pictures of the huge ( and very cambered ) original vertical tail, that was the reason. After getting the flight envelope opened up, we attacked verifying the tail allowed us to meet the requirement. ( Aside: SA flight test had done a similar program on the original S-58 design. That tail rotor had flapping hinges, which allowed the determination of zero tail rotor thrust to be done fairly easily ). A very long story short, with a good number of frustrating flights, meetings, different technical/instrumentation approaches etc left us unable to determine when we were at precisely zero thrust with the rigid, crossbeam tail rotor. That, in addition to the fact that the huge tail incurred a list of penalties that was significant, led us to make the decision to take a proposal non-compliance on that requirement*. As the company strategy was to take zero exceptions, that was a serious internal issue. Result was that we cut the tail down significantly to what it is today. For those who espouse the position that a tactical helicopter can never have too much tail rotor thrust ( I am in that number ), it was the correct compromise.
*I can't say this with surety, but from the size of it, the Boeing UTTAS did not appear to be configured to meet that requirement either.
Now to Henra's and RG's question. I believe that the data that we did generate during the unsuccessful testing, in addition to a few incidents in the field over the years, the answer is that I am not aware of anyone achieving stable level flight ( yes, with a significant sideslip ) following a TR thrust loss, and thus am of the opinion that the existing emergency procedure ( not aware it ever changed ) is correct. RG, I will bring your note to the attention of the now retired test pilot who took over the UH-60 program and who has an excellent memory. Perhaps we can close that loop.
Good posts.