Well-hung Start
Well-known member
- Joined
- Dec 16, 2004
- Posts
- 69
Caw Loch
I'm not a GE Engineer, but I did stay at a Fleabag Inn last night on my layover......I have a few good points here, so lissen up!......
Core lock is a possibility even WITHOUT overtemping the engines: For each new CRJ aircraft in pre-delivery tests, Bombardier INTENTIONALLY shuts down an engine during high-power operation at altitude. They consider this a high-temperature shutdown, and the intent of this is to INDUCE core-lock in susceptible engines.
The ones that do "lock" (evidenced by inability to generate ANY N2 speed during a CORRECT windmill procedure at >300 KIAS) are then put through a high-tech "grind-in" procedure: starting the engine with the APU to over-torque the bound-up core bearings and wear down the grooves responsible for this lock-up.
A few points from this:
1) There is no guaranty that, even if done properly, a windmill start will succeed. And if done improperly (eg: IAS 248 instead of 335), fuggedaboudit!
2) A sudden stoppage of the engine by fuel shutoff at high altitude is Bombardier's recipe to induce "core-lock."
-------BUT-------
----->A gradual stoppage at high altitude, like happened in the Pinnacle disaster, whilst still pouring fuel into an overtemp engine, is Pinnacle's recipe for "core-melt"
3) Not even Bombardier test-pilots would allow the plane to stall at 158 KIAS at 41,000 without taking extraordinary measures to protect themselves and the airframe from likely damage.
I'm not a GE Engineer, but I did stay at a Fleabag Inn last night on my layover......I have a few good points here, so lissen up!......
Core lock is a possibility even WITHOUT overtemping the engines: For each new CRJ aircraft in pre-delivery tests, Bombardier INTENTIONALLY shuts down an engine during high-power operation at altitude. They consider this a high-temperature shutdown, and the intent of this is to INDUCE core-lock in susceptible engines.
The ones that do "lock" (evidenced by inability to generate ANY N2 speed during a CORRECT windmill procedure at >300 KIAS) are then put through a high-tech "grind-in" procedure: starting the engine with the APU to over-torque the bound-up core bearings and wear down the grooves responsible for this lock-up.
A few points from this:
1) There is no guaranty that, even if done properly, a windmill start will succeed. And if done improperly (eg: IAS 248 instead of 335), fuggedaboudit!
2) A sudden stoppage of the engine by fuel shutoff at high altitude is Bombardier's recipe to induce "core-lock."
-------BUT-------
----->A gradual stoppage at high altitude, like happened in the Pinnacle disaster, whilst still pouring fuel into an overtemp engine, is Pinnacle's recipe for "core-melt"
3) Not even Bombardier test-pilots would allow the plane to stall at 158 KIAS at 41,000 without taking extraordinary measures to protect themselves and the airframe from likely damage.
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