I Was doing a flight from KDEN-EGLL in the UAL 787-10 my cruiseing altitude was FL400 i was about to go asleep to get some rest but then i relised i was loosing speed and my aircraft was not making any effort to speed up or add power i manually added power but that seemed to now work i decended down to FL330 and it was no help can someone help me to what was going on?
BOEING 787-10 Loosing speed at cruise
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I Was doing a flight from KDEN-EGLL in the UAL 787-10 my cruiseing altitude was FL400 i was about to go asleep to get some rest but then i relised i was loosing speed and my aircraft was not making any effort to speed up or add power i manually added power but that seemed to now work i decended down to FL330 and it was no help can someone help me to what was going on?
Check to see if you have cruz thrust in the n1 limit section on the fmc and not climb
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I have checked and it was set to cruz and i was still loosing speed im not sure
Was auto throttle enabled to enforce the cruise limit?
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Attach a screenshot MCP
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- Official Post
Would be interesting to know how fast you were in the first place.... The slower you are the less thrust the engines can produce at that altitude because of the better ram air effect and better air compression at higher mach numbers. So basically just stick to the default cruise speed, then the thrust should be enough to maintain that. If you fly slower you increase drag and reduce thrust, that's probably the issue here.
I still need to increase the stall speed on the PFD, so that you realize the stall is now at 230 kt or so and not at 200 kt like at lower altitudes. So anything below like 240 kt at that high altitude is too slow to maintain cruise speed.
A typical mistake would be to use vertical speed mode to climb up to cruise altitude. This will bring you into a stall situation quite easily and you just wont have enough thrust to recover without loosing altitude.