Confabulous,
Flight idle prop pitch is supposed to be 12 degrees, the only time the blades go flat to zero pitch in flight
is if the Pilot moves the powerlevers over the gate into Beta mode- a very big no-no!!!!!!! on any fixed-shaft turbine engine. On the TPE-331 series - many BAD things can happen as a result of going into beta in flight: engine overspeed, blanketing of airflow over the wings and my favourite: one engine comes out of beta before the other, and the aircraft snap rolls into terra-firma as the crews of a CASA 212 as well as NASCAR racer/pilot in his Merlin IIB all found out with tragic results.
That Mu-2 that RodtheSod spun and recovered, i believe had insidious problems causing a subtle powerloss on one engine and therefore was in effect "windmilling" creating just enough power not to trip the NTS but not enough to produce zero thrust (As torque output is also a function of blade angle) hence the spin during the stall sequence(As was later found by Garrett PHX) and the need for assymetric power to recover. He was very lucky that he had significant aerobatic skill.
Known of a couple Mu-2s being spun without needing assymetrical power to recover and using standard spin recovery technique, but then again this was being done for giggles over the Gulf of Mexico by ex -fighter jocks bored with drone controlling on a USAF contract, engaging in mock ACM before recovering to Tyndall AFB.
Ok! so its not approved, but US military and their contractors march to their own tune. Vagely remeber spinning a T-42 Baron during my init multi training course at Cairns AAF handle pretty well, I havent personally spun a MU-2 but have lost both engines in flight twice!!!!!!
Once after shuting down and securing the left Engine during an NTS testflight, the right engine flamedout
my trainee in the left seat had the bright idea
to SEE what would happen if he turned the left fuel solenoid-valve off, he didnt look, confirm or announce his bright idea and prompty shut the right valve off
, I had my head down filling out the flight testcard
Know this both engines can be air-started simultaineously!!!, The second occasion was wamy of mechanical failure, my faulty troubleshooting ( differences in systems between J,L and -60 longbodys) and stupidity ( which i'm still in therapy for
) but i am ever so gratefull for the gut feeling i had to conduct the air test over the airfield at 8000; (much to the humbug of TWR and APRCH controllers) instead of 20 -40 nm away as was my standard practise, after that fiasco, no more airtests with both engines fresh off the teststand that i hadnt personally seen run the full profile on testcell first.
Still a good airplane, would buy one in a heartbeat