Originally Posted by
safetypee
lemme, et al.
Most of the diagrams presented are too simple for this discussion.
agree. Your description is marvelous, thanks! Designing a four-engine airplane with loss of all engines is a fascinating challenge. The devil lives in the details. I dig deep to understand these issues in my blog.
Satcom Guru: LMI2933 LAMIA AVRO RJ85 Medellín Deadstick
Originally Posted by
safetypee
The engine windmill characteristics involve a relatively fast N1 but slow N2, even to the point of stopping (170kts?).
Hydraulic and elect services require high N2. Normal operations use a flight idle stop.
I believe they established about 125 KIAS from 16,000 down. From your statement, that would not generate much windmill hydraulic power (if any).
Originally Posted by
safetypee
Some of the calculated speeds appear very slow for what could have been a low or zero flap setting. Thus unless the flaps were selected before all power loss, it would be more consistent speculation to consider stall or near stall conditions.
From deep and failing memory, I recall that the stall warning was available on essential AC and possibly emergency DC.
I think that they configured for landing under engine power ahead of flameout. It does not look like a deep stall scenario, rather a steep, controlled descent. They had 11,000 feet to lose by the FAP in about 16 nm, and they started clean.
from FCOM:
There are two electronic stall protection channels: channel 1 and channel 2. Either channel can provide stall warning and stall identification. With one channel failed, the working channel can provide complete stall protection. Each channel requires power from the ESS AC and the ESS DC busbars.
Originally Posted by
safetypee
flynomore; fungus, yes it can, first hand experience of gauging problems, world wide; and corrosion (Columbia!). Also there were reports of possible fuel pump blocking and engines stopping - far east.
noted, I have one referenced.