PJ2
My question is, how does one use the guage in operations, and how does one stay away from the stall AoA using an AoA guage when the AoA at which the aircraft will stall changes with Mach? Would the guage be calibrated, (using much the same logic as the ECAM does in Alt/Dir Law - a table was posted around Thread 4 or 5 showing this AoA calculation at which the stall warning would sound).
Our gauge was a simple round one (posted it before) with aditional tone and indexer lights in the front window for the approach and landing. I donīt know (but assume) that it was somehow calibrated. We could use it over the complete speed range from 0 to Mach 2.2 in all altitudes and under all loads and in all configurations. As our Rhino was not digital and had only an limited capable flight data computer i assume, that it is no rocket science today either to make it usable under all circumstances. With power on the aircraft and the WOW switch pressed by mintenance we hand tested it by turning the vane and observing the gauge, lights and tone at the appropriate units of AOA (donīt know even if the indicated units were equal to degrees).
PJ2
But, if I may, I think that there is more to an AoA guage than just installing and selectively watching it. Clearly, the AoA at which a transport will stall at high Mach number at cruise altitude is different (due Mach effect) than an approach AoA which is typically 8 to 12deg depending. In cruise, a stall AoA may be as low as 4deg, as it was here when the first blip of the stall warning was heard, and later, at a much-reduced Mach but at FL376 or so, the aircraft was starting to stall at an AoA of around 7deg.
Good points, but again, i think it is a calibration kind of thing and for sure relevant to the Rhino and other fighters as well. The indicated units could be calibrated to the facts you mentioned and then the numbers would be identical to all situations from T/O to Landing.
PJ2
I'm trying here to imagine how the guage would get the crew/PF of AF447 out of trouble and how the PF would use an AoA indication and what AoA he would be targeting.
First it should keep them out of trouble. There is a fast familirization with the values normal present during cruise (normally close to max range) approach and landing. In a situation where these values start to deviate from the known common values it indcates not only a state, but also a trend. Now you may say, that the speed tape does the same, wether you get fast or slow. The difference being that the AOA and consequently also an AOA indication also puts the loading of the airframe into the equation. During the initial pullup the AOA would have increased from known value to the stall threshold value thus telling the PF to ease of on the controls , reduce pitch and never let this AOA go higher than safe value. While the Stall warning is only an ON / Off indication, the reference to the AOA is a "performance state" indication with hints to the momentary trend. Changes due to loading or unloading are immidiately observable. That could have helped after stall had occurred during the recovery attempts as well. SS aft, AOA stays high, SS forward, AOA reduces, keep SS longer forward, AOA reduces further.... and so on. Even the effects of the power changes would have been seen on the gauge, thus developing a quick learning pattern what will work and what is wrong.
In all my time in the AF i never had or even heard from an AOA malfunction (except birdstrike) and understanding and working with the gauge, the aural tone and the indexer lights was no issue at all.
Just adapt it to the use in the individual airframe and go for it.