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Guest castleberg

High altitude stall

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Guest castleberg

Hello I was in the middle of a flight from Seattle to Newark with the 744 when I got a print of type rating lesson 3. I was cruising on FL370 and reading the print, so I tried to introduce a stall at that altitude: I was in full auto-flight regime, i.e. AP, LNAV, VNAV and A/T. Now I speed-intervened on the MCP and reduced speed to around 230 kts. Thrust was reduced automatically and I got a stall warning a few seconds later. Here's what I did and what happened: I disconnected the Autopilot, left on A/T and hit TOGA on the MCP helpbutton. TOGA didn't seem to work. The upper EICAS still showed CRZ. IAS fell down to around 210 kts, stalling heavily. Then I disconnected A/T, too, and added 101% N1 manually. I could easily keep the altitude with a little pitch but IAS didn't increase any. It didn't decrease either. No matter what I did, the plane would not gain speed and was still in a dangerous stall position (well in the red dots). Only after introducing a gentle descent with around -500fpm I could gain speed and at FL 350 I was up to normal speed (some 0.85 Mach) and ready to climb back at my cruise altitude. Is this what the airplane's supposed to do in high altitude or did I mess around a little? Help much appreciated. Best regardsTom

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Guest D17S

That's the deal. You

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>Is this what the airplane's supposed to do in high altitude or>did I mess around a little? Help much appreciated. >As RR remarked in his lesson 3 stalls are very poorly modelled in the MSFS platform and in no way this PMDG aircraft will behave like the real thing once you entered the stall regime. Therefore I would not use this simulation to practice any stall recovery techniques. Michael J.http://www.precisionmanuals.com/images/for...argo_hauler.gifhttp://sales.hifisim.com/pub-download/asv6-banner-beta.jpg


Michael J.

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Tom just a note on the TOGA function for reference.It will not function in the situation you were in.the TOGA function will work for the following:1. On the TO with AT switch armed and airspeed less than 50kts. Failure to select it before 50kts means it will not engage and cannot be engaged until after passing 400ft.2. When Go around (GA) is armed. This will be annunciated as the thrust ref limit on EICAS. It is armed when the flaps are out of up or the Glideslope is captured.If you really want to appreciate the inherent problems with flying at altitude then climb to the maximum altitude as indicated on the FMC. When established in the cruise come back to min speed clean and then disconnect the AT and apply maximum thrust. Note how long it takes to accelerate back to normal speed. Have a close look at the space between the red bricks.....not much. One of the problems with flying at these altitudes is knowing which stall you have.....high or low speed. With an initial stall indication the first response should always be to agressively apply maximum thrust and lower the nose.Our company almost lost a DC10 years ago whilst doing the acceptance checks from Douglas. It entered a very deep stall and lost in excess of 20,000ft. I believe selecting the gear down helped the recovery and they recovered at around 10,000 ft. It is interesting to note that there has been a change to the thinking behind unusual attitude recovery. On recognition of a significant nose high situation rather than apply thrust to prevent speed decay that it should be reduced and the aircraft rolled to assist with the nose down pitch rate. This is due to the fact that with large powered underslung engines such as the 747 have a low thrust line and that the application of power causes a pitch up reaction. This actively works against the down elevator application and can cause a faster rate of speed decay and the delay in reduction of the aircraft attitude and cause stalled or deep stalled condition. We do this in the motion simulator and it feels really unnatural to reduce thrust with the nose so high. It goes against everything we were ever taught back in basic flight school. Anyway I digress.CheersSteve


Cheers

Steve Hall

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Guest castleberg

Hello and wowwww...Extremely helpful answers, everyone of them. Thank you very much for your support. RegardsTom

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"Then I disconnected A/T, too, and added 101% N1 manually. I could easily keep the altitude with a little pitch but IAS didn't increase any. It didn't decrease either. No matter what I did, the plane would not gain speed and was still in a dangerous stall position (well in the red dots). Only after introducing a gentle descent with around -500fpm I could gain speed and at FL 350 I was up to normal speed (some 0.85 Mach) and ready to climb back at my cruise altitude."It sounds you are in slow flight...1) usual nose up altitude2) low airspeed but high rpmben

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