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Guest Susan27

MD11: How to perform a Crossbleed Engine-Startup?

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Guest Susan27

I would like to perform a Crossbleed Startup of the engines...to be more precise:1) Starting first engine (No3) with APU or GND-Bleed air2) Startup the other two engines (No1 & 2) via a Crossbleed Start with bleed air of the already running engine (No3)I didnt find something about in the manuals nor did I find a crossbleed switch on the overhead pnl...so I would be happy if someone could just tell me...If a Crossbleed Startup is possible with the PMDG MD11...and if so...how (which switches/buttons) to use...?Thanks very much! :)

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Guest Susan27

Thanks very much, Steven...you were so right! :)It is so "easy" that I never thought of just trying it...lol!Bytheway: 1) Is it possible to set the pneumatic pressure to "manual"? If so...is the appropriate button for this the one located right of "Pack3" at the overhead pnl...?2) Is this crossbleed somehow damaging/harmful for the engines if this crossbleed startup procedures are performed oftenly...besides the little higher N1/EPR the already running engine has to have in order to allow a crossbleed engine startup to occur...?

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2) I wouldn't think so. The engine is capable of much more, and does provide much more bleed in normal operation during flight than during start. The APU is more ecomical. The bleed from a large turbine is analogous to diverting a stream of water from a river.


Dan Downs KCRP

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Guest Susan27

EDIT:3) I now looked closely at the N1 & N2 percent values of the already running single engine (engine No3) before and during crossbleed startup of the second engine (No1):From what I know from another real world airline forum...the flight crew has to get clearance from the airports Tower for a crossbleed startup because they have to increase idle-power setting (high idle power) of the already running engine (N1) so that there is enough air-pressure for the x-bleed...the normal ("low") idle pwr setting is simply not high enough to provide sufficient bleed-air (pressure)...for a x-bleed.So the result would be a (slightly?) *higher* N1/N2/EPR for engine No1 during x-bleed startup. But those values of the PMDG-MD11 acrft just remained totally unchanged at *normal* idle-power (N1 24.3%; EPR 1.01)...as before initiating the crossbleed startup for engine No1...Question: Is the needed high-idle power setting with the higher N1 etc. values simply NOT simulated/displayed here...or is this the same at the real MD11...? If the latter:Why isnt high-idle-pwr setting not needed at a MD11 crossbleed startup anymore...? Is the "normal" low idle power (24.3% N1) perhapes already "High enough" for such a proc...? Thanks again guys! :)

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>>Question: Is the needed high-idle power setting with the>higher N1 etc. values simply NOT simulated/displayed here...or>is this the same at the real MD11...? Susan,It is simulated and will be displayed as per real aircraft.But you have to increase that required power.... sss ....by manual throttle operation.Regards,Harry

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Guest Susan27

...>But you have to increase that required power.... sss ....by>manual throttle operation.>>Regards,>Harry>Well, I do NOT increase power settings to High idle pwr (staying at 24.3% N1)...and the crossbleed startup is indeed working without any problems with this low(!) idle power...Is this realistic or asked the other way: Would I be able with a real MD11 to perform a crossbleed startup by remaining at idle-power (low = 24.3%)...in reality, too (and as it is working/simulated at PMDG MD11 sim)?

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Susan,Did you try this at an elevated airport already? or only at a near sealevel situation?Slightly above idle thrust might be required then.Observe Level 1 alert: START AIR PRES LO.Regards,Harry

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This should not be possible with idle power, afaik.Maybe it's a small bug.rgds,Tero


PPL(A)

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I would not be surprised if you can do it with one engine at idle because those things are big and strong. At idle they produce more air than the apu. Am I right or do I need to be corrected? I'm not sure, but this is what I would imagine.


Steven Penninck

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Guest rellehenk

You need 25 psi pneumatic pressure to start the engine. It is possible to start the engines with less than 25 psi, but it is just a limitation. (recommended minimum pressure for engine start).Normally, engine number 2 is the supplying engine for x-bleed start.The procedure is to select ECON OFF. If the air system is in AUTO, just pull the starter switch. Increase power of the supplying engine to 25 psi air pressure (select air page on the SD).

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