Originally Posted by vaneyck
In the BEA press conference linked by jcjeant, J-P Troadec says:
'the pilot should have applied the unreliable IAS procedure and in fact this procedure consists specifically of adopting a pitch attitude of 5°, whereas the pitch attitude that was adopted at that moment was greater.'
So once again we have confirmed, without comment, that the SOP in case of UAS in cruise involves raising the nose - just not as greatly as the PF with his large stick input raised it.
PJ2 has argued against any change in pitch before starting the checklist, and his arguments sound very convincing to me. Why would you make any change in the flight path of an aircraft in level cruise that has shown no signs of instability? And how long would you keep on at this pitch angle? Indefinitely? Surely the chances of inadvertent overspeed are less threatening than the chance of getting yourself too high, too slow.
Originally Posted by Lonewolf 50
Vaneyck Good point, in that a pitch increase to 5 deg at that power setting would seem to result in a climb and deceleration, where on wasn't required, nor desired. Indeed, some minutes before, the crew had remarked on how a planned climb could not be done since temps had not developed as forecast.
Why go from S & L to decelerating climb when there is no need for it? If this is what the BEA contact is suggesting, I am puzzled as to why.
Originally Posted by ECAM actions
More to the point: if you have an aircraft flying in a known pitch/power combination that is sustaining level flight and stable speed quite happily, why use approximations from the book in the first instance?
Ladies and gentlemen, dear fellow PPRuNers, please allow me to clear some of the misconsceptions you might have about procedure we're discussing here.
Too keep nomenclature proper: UAS procedure is not SOP. If it is to be applied, you have departed the domain of standard operation. It is
EMERGENCY /
ABNORMAL.
Emergency procedures are not written by company lawyers, they are written by test pilots. They write them in blood in of those who were unfortunate to trespass into territories forbidden to them by aerodynamics, meteorology or mechanics and underline them in blood of those who were unable to follow them for whatever reasons.
If an emergency procedure could talk this would be what it says to pilot: "I am your emergency procedure. Know me well, apply me properly, timely and precisely when you need me or die. Second guess me only if you are absolutely sure you're better off without than with me but accept you very well might die if you are wrong."
Values of 5° degrees and climb power are written in the book but they are not to be set by the book. They are memory items, they have to be known by heart and set without undue delay. On Airbi they are to be maintained until attitude and setting appropriate for flight phase and weight are read out from QRH and set. They keep you both out of stall and overspeed at any weight even if you fumble with QRH and it takes you couple of minutes to find the table or even if you maintain them until fuel runs out.
5° pitch with climb power, applied at cruise altitude/level will keep you out of both stall and overspeed on any Airbus, 318 to 380, at any weight. So on Piper Cub, ATR-42, B737, Su-27 Flanker and her derivatives (provided external stores don't affect maximum allowable speed more than drag, that is), An-225 Mriya and almost anything in between. Designs on which it might or might not work are relatively overpowered ones with relatively low limiting Mach number, such as early jet transports.
It's basic aerodynamics and performance, folks.