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PostPosted: Tue Oct 06, 2009 5:01 am 
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Joined: Fri Feb 27, 2009 1:39 am
Posts: 1908
Location: Up here wishing I was down there.
I know the Level-D forums provide support for all things technical, this thread is for questions on how to do things. I've gone through the manual, but there's just no way my little brain can grasp everything in there, and sometimes I just have absolutely no clue what's going wrong.

This is a note for the next guy that can't get it up. :D I once stalled getting this bird up to altitude using the default FMC values from the manual and didn't understand why.

On the captain's panel, #22 TRP, Thrust Rating Panel, is the likely culprit. These are pre-configured engine profiles: Take-Off, Go-Around, Climb, Climb 1, Climb 2, Continuous Power and Cruise.

If you have trouble getting up to altitude, check these controls. Click on each and watch the rating over the N1 gauges change. The ratings automatically adjust according with outside air temperature, so don't be surprised when they change.

EDIT: Just to confirm that this was indeed my problem. The LDS767 now maintains AP speed through FL290 and just keeps on climbing. WOOHOO !!!



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PostPosted: Tue Oct 06, 2009 8:58 pm 
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Joined: Wed Jul 16, 2003 1:16 am
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Location: Ottawa
Robert - please clarify. I've never used those buttons and I've also never had to use them in order to climb like a banshee. Are you saying you used them during your ascent somehow? Which one, and when did you click it?

My routing to ascend to cruise is (no FMC required)
- flight director and autothrottle on
- manual throttle to 70% N1
- hit NIspr and engine spools up to full revs
- once climbing, hit Alt-HOLD (or any autopilot button) then the Centre CMD button on A/P ENGAGE

Assuming your AP altitude is set somewhere above you, you should climb right to it.



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PostPosted: Wed Oct 07, 2009 6:25 pm 
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Quote:
Are you saying you used them during your ascent somehow?


Yup.


Quote:
Which one, and when did you click it?


I clicked on Take-Off while on the ground, then Climb once positive climb and then it automatically went to Cruise once at altitude.

Consider them as gears; Climb 1 and Climb 2 are progressively "weaker" for when you don't need as much power as Climb. From what I can tell, the TRP is used with the FMC.

I don't know what setting the TRP was originally set at any more. I'm assuming it must have been set at Cruise which is weak compared to Climb or Take-Off. Now the 767 goes as it should; FL340 yesterday without problems.



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PostPosted: Fri Oct 16, 2009 7:04 pm 

Joined: Tue Aug 17, 2004 11:58 pm
Posts: 81
Location: Ottawa
Here's a small bit on the TRP (Thrust Reduction Profile) Robert mentioned. Note also that the 737Ng series has the same thing called Engine Derating and I think the Airbus has the same features associated with its Flex power settings. First, it is usual for the takeoff profile to be flown at V2+20 kts. This provides a safe speed and keeps the ac below the gear limit speed so it can be safely retracted. Also buys some time before flap retraction limit speeds are encountered but perhaps more than anything it saves wear and tear on multimillion dollar engines. Note also that airliners can produce more power than is needed for most takeoff conditions. Now, depending on weight, at max N1 the deck angle to maintain V2+20 could be very steep thus severely limiting forward visibility and being quite uncomfortable to passengers. Thus the concept of thrust reduction. There are a lot of factors taken into consideration such as runway length, slope etc along with temperature and so on on but the big thing is weight. So in prep for TO pilots consult the AC perf charts which tell them what thrust reduction mode will provide acceptable performance. So if the ac is lightly loaded they may choose to use takeoff 2 reduction which causes the engine computers (FADEC) to designate max TO power at something like 5% less than max. This will result in a lower but adequate TO climb rate at V2+20. There is no need to go skyward like a homesick angel! The Takeoff 1 setting would mean something like a 2% reduction and would be selected for heavier loads. A max weight TO and/or a shorter runway might require max N1. Bear in mind that these presets are automatically invoked when the TOGA button is used and thr red settings have been selected. The same thing applies to the climb phase which is entered when passing the Thr Reduction altitude set when initializing the FMC. The climb thrust presets are calculated based on the desired climb speed set during FMC initialization. None of this is needed to manually set power but it sure adds to the workload during a critical phase of the flight.
one last thing... if you find it necessary to manually adjust power to avoid a stall during climb, it might well be because you have selected an improper thrust reduction mode for the weight of the ac. There is also an altitude I think above which thrust reduction is discontinued so as to provide the proper power to maintain desired climb speed and rate of climb

Anyway, that's generally my understanding of how it fits into the scheme of things!



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