Jim Wilson said: > Hi Thomas, > > A couple questions below. > > Thomas Holland <[EMAIL PROTECTED]> said: > > > The CLB and CON (max. continuous thrust) you mentioned above (and the other > > two modes CRZ and TO/GA) are just limits. This means, that they set an upper > > limit on how much thrust will be provided by the autothrottle system. The > > autothrottle will decide on how much thrust is actually needed and the > > autothrottle will give that thrust up to the selected limit. > > So if in SPD mode the selected speed was too high, the autothrottle would > still cut off at the max for whatever mode.
SPD mode will always try to achive the selected IAS, but it can't go over the selected engine limit. If you would select a V/S climb with 4000fpm and select a speed of 340 kts, with CLB thrust selected, the autothrottle will give you full climb thrust (and after a while you would stall, because the autopilot would continue to pitch up to get the climb rate and CLB thrust is not enough to maintain any speed with such a climb rate.) > Are the CLB and CRZ preset to a > given thrust? And CON is that preset to the max rating of the engine or is it > adjustable? Finally what is "TO/GA"? TO = Takeoff and GA = Go Around thrust. GA thrust is the maximum thrust the engine can deliver for a limited time (5 or 10 minutes, depending on engine type and certification). Can only be selected in flight. TO thrust is like GA thrust, but can only be selected on the ground and can be adjusted between 100% and 75%. CON (Max. continuous Thrust) is fixed for the engine and is not adjustable. Maximum sustainable engine thrust setting. CLB thrust can be adjusted in three steps, CLB (full climb thrust, about 75% of takeoff thrust), CLB 1 (about 94% of full climb thrust) and CLB 2 (about 88% of full climb thrust). CRZ is also a fixed maximum thrust for normal cruise ops. Note: all numbers above are for our B757s with RB211 Engines. They will be different on other engine/airframe combinations. I should have noted on my previous message, that these limit modes are actually controlled by the engines control systems, the autothrottle just observes them. The pilot does not have to observe them, firewalling the throttles will always give Go Around thrust, no matter what limit was selected. > > > * ALT HOLD will maintain the current altitude by adjusting the pitch. The > > autothrottle will go to SPD mode. > SPD mode at current IAS? Actually: selected IAS. So if the aircraft was still slower than the selected speed at level off, the autothrottle would accelerate until the selected speed is reached. > > > * FLCH is the most common Mode for climb/descents. In this mode the > Thank you for this description. This is very helpful. If you have more questions don't hesitate to write a private eMail (I can't read this list regularly). thomas > > Best, > > Jim _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
