PPRuNe Forums - View Single Post - Stop Margin is based on OAT / FLEX Temp?
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Old 15th Jan 2019, 11:23
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FlightDetent

Only half a speed-brake
 
Join Date: Apr 2003
Location: Commuting not home
Age: 46
Posts: 4,319
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STBYRUD, that’s plain wrong.

Ondrayy, your captain is perfectly right and you have been undertrained, which is what computerized performance made possible. Not your fault.

The whole of FLEX or Assumed Temperature Thrust is based on iterations using TOGA with ever increasing OAT, until you hit the limit. And then AST = TOGA (OATlim -1). Point here being the entire aerodynamic / accelerating / stopping model is calculated under the assumed temperatures. Sometimes even higher than the A/C certified limit for the actual operation.

Google for TAT Effect ASDA or similar, your thirst will be satisfied. . Three direction markers and one warning for you:

  • The 3% quoted by EGPFlyer is also found in a UK CAA approved Ops Manual of a very large airline with a deeply knowledgeable performance department. It can be quickly verified if you have access to the full Performace Engineers Package SW.
  • F = -a*m
  • Ek = 1/2 * m * v * v
  • The calculation model of the deceleration phase for RTO does not consider the effect of (wet) paint and rubber deposits towards the far runway end.

Last edited by FlightDetent; 16th Jan 2019 at 10:25.
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