BBN radar, I find your scenario hard to believe. First off the D8 fleet has has over 20 million hours, this would have happened a lot more times, and we would know about it. This engine/ propeller system is used on other aircraft and as far as I know, what happened here has not manifested itself as being a problem.
I agree, it is hard to believe, but apparently, this is the 11th time this has happened (but maybe the only time it's happened to both engines?). We do know about it, that's why there are multiple ADs issued worldwide to prevent it; FAA, UK CAA, and now PNG CAA and shortly Australian CASA. Transport Canada will not mandate it, because to do so would make Bombardier admit fault and this would cost them hundreds of millions of $$$$ in law suits worldwide. Bombardier supply the kits for the beta-lockout (at a nice cost of course
) and if they admit a design fault, then they would probably have to supply them free of charge worldwide.
I was told of a similar case happening in a Brasilia where they lost one engine under similar circumstances and the remaining (badly damaged) engine just got them home. I'm fuzzy on details so maybe someone else knows the story?...
How many times has a crew oversped an airplane with this engine/ propeller combination, what would they do first if they're overspeeding and they have the power levers forward? I'm sure pulling back power in response to an overspeed is not unusual. If this is some kind of anomally that shows up once every 10 years, why did both props overspeed at the same time?
good questions. If I was flying Dash 8s for a different company and after reading this I wouldn't tempt fate and would make sure to raise the nose to reduce airspeed as well as reducing power. Something interesting to note is that after the left engine destroyed itself (less than 3 seconds after initial airspeed overspeed, and reaching 2000rpm) the right engine also oversped and then
feathered itself. Neither P&W, Hamilton standard nor Bombardier have been able to explain why this occured.
One thing that does come to mind here is a malfunction of the gate itself. The gate is spring loaded down, if for some reason it wasn't down and the crew pulls the PL's back to flight idle and the gate isn't there... Anyway, the beta lockout system on US registered D8's is there to prevent this, it should mandatory worldwide.
Yeah, possible. Or the PF may have accidentally raised the gate release triggers. Only one of them needs to be lifted 2mm for both power levers to come back from flight idle! Since the accident, our new flight standing orders are; that airspeed must not exceed Vmo minus 30 knots, condition levers must be at 1050 rpm (up from 900 in cruise) prior to descent AND (basically) that fingers must be kept well away from gate release triggers until wheels are on the ground.
Yes, the beta-lockout should be mandatory worldwide! No arguments there!