Y apu IN ETOPS ??
Joined: Jan 2007
Posts: 200
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From: Vermont
ETOPS requires routine sampling data to verify that the maintenance practices used by the operator are meeting the specified criteria for a third source of electrical power. Periodic airstarts, at the most critical, cold-soaked point of the flight, top of descent, provide that data.
Joined: May 2006
Posts: 40
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From: Calgary, AB, Canada
The logic behind it is that since the NG has no emergency source of electrical power (RAT) the APU is kept running so that in the event of a loss of a single or double source of electrical power, it can be selected on as quickly as the checklist requires without the worry that a cold soaked APU may not start when required.
The fuel burn (+/_ 300lbs/hr) is accounted for from departure to ETOPS Exit Point.
The fuel burn (+/_ 300lbs/hr) is accounted for from departure to ETOPS Exit Point.
Per Ardua ad Astraeus
Joined: Mar 2000
Posts: 18,575
Likes: 4
From: UK
Oh dear! Why are we talking about 757/767/AB etc?????
Here is the question:
"Why Do We Start Apu In Etops Flight ??? {boeing 737 Ng }
#4 is the answer. Does the 737nG have a RAT?
No
That's all!
Here is the question:
"Why Do We Start Apu In Etops Flight ??? {boeing 737 Ng }
#4 is the answer. Does the 737nG have a RAT?
No
That's all!
Joined: Jan 2007
Posts: 200
Likes: 0
From: Vermont
A-ha. I may have misunderstood the question; I thought we were referring to periodic APU starts. I believe we need more information on the equipage and certification of the airplane. Looking through my handy 737 NG FCOM, I don't see any evidence of a RAT, which is interesting (I am not typed on the airplane), but then the device most of you are referring to is the HDG (or HMG, depending on who wrote your manuals), which is the hydraulically driven generator. That is the ETOPS backup which automatically picks up critical services if both main generators fail. The RAT, at least on the 767 and 757, only provides basic hydraulics for flight controls.
If the question refers to continuous operation of the APU during ETOPS, that is interesting...there are 757s that are not equipped with the HDG and thus not ETOPS capable, and then there are those that are equipped with the HDG and thus (with other additions as well) are ETOPS capable. What is interesting to me is that the 737 NG could be ETOPS capable without the HDG or similar device, as I can't see my current employer failing to utilize non-HDG equipped 757s on ETOPS if there were a way to do it...
Of course, if you blast off into subspace with one generator inoperative, then the APU has to be running whether ETOPS or not.
If the question refers to continuous operation of the APU during ETOPS, that is interesting...there are 757s that are not equipped with the HDG and thus not ETOPS capable, and then there are those that are equipped with the HDG and thus (with other additions as well) are ETOPS capable. What is interesting to me is that the 737 NG could be ETOPS capable without the HDG or similar device, as I can't see my current employer failing to utilize non-HDG equipped 757s on ETOPS if there were a way to do it...
Of course, if you blast off into subspace with one generator inoperative, then the APU has to be running whether ETOPS or not.
Joined: Oct 2009
Posts: 1,270
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From: UK
Is it possible for an Airbus to start the APU at any altitude? I always though that APU start can only be done below 25k pressure altitude.
The APU may be started up to FL 410 (it should start within 3 consecutive attempts).
Joined: Mar 2006
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From: Choroni, sometimes
Ia always though that APU start can only be done below 25k pressure altitude.
Some are able to start up to 41.500 feet.
Joined: Oct 2010
Posts: 430
Likes: 37
From: Germany
hey aussie.. theres no engine failure so whats with galley shedding?
warm coffee without engine failure regardless of apu and cold coffee with engine failure regardless of apu afaik regarding to
this:
so that the pax can still enjoy the warm coffee when the 2 engines stop turning.
statement of you...
warm coffee without engine failure regardless of apu and cold coffee with engine failure regardless of apu afaik regarding to
this:
so that the pax can still enjoy the warm coffee when the 2 engines stop turning.
statement of you...
Joined: Aug 2003
Posts: 481
Likes: 23
From: Melbourne
Take a look at the Airbus A320 FCOM Duyentranvan 
In particular FCOM 1.24.20 p4 Electrical Controls and Indicators
Here is a quote from the manual :
Therefore, when both engines stop, this means both generators stop. Engine failure is relevant here.
Even if the APU is running, the galley will be shed as only 1 generator is operating.
Therefore, unfortunately, the pax CAN NOT enjoy a coffee when the 2 engine stop turning.
In particular FCOM 1.24.20 p4 Electrical Controls and Indicators
Here is a quote from the manual :
The main galley, the in-seat power supply and the IFE system are
automatically shed :
– In flight : when only one generator is operating.
automatically shed :
– In flight : when only one generator is operating.
Therefore, when both engines stop, this means both generators stop. Engine failure is relevant here.
Even if the APU is running, the galley will be shed as only 1 generator is operating.
Therefore, unfortunately, the pax CAN NOT enjoy a coffee when the 2 engine stop turning.
Last edited by John Citizen; 28th October 2010 at 05:54.
Joined: Jul 2001
Posts: 4,960
Likes: 17
From: Australia
The RAT, at least on the 767 and 757, only provides basic hydraulics for flight controls.
I guess it may vary with particular aircraft, and it is a while ago since I operated one, but my memory tells me that the RAT on a B767-200/300 also powered a hydraulic driven generator.
Tootle pip!!