Y apu IN ETOPS ??
 

Why Do We Start Apu In Etops Flight ??? {boeing 737 Ng }

Why should you?

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.

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.

well the airbus requires the APU to be on as well and its not only for boeing.so that the pax can still enjoy the warm coffee when the 2 engines stop turning.

We dont start the APU at all in the A320. I dont think that you can still enjoy a warm coffee as I believe the galley will automatically be shed.

Never started the APU on any A330 ETOPS flights, has never been required. APU can be U/S prior to dispatch and we can still do ETOPS sectors. Maybe as we have a RAT and emergency generator.

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!

Though to go further off topic, can anyone explain why the 777 is 180ETOPS with a US APU, but rquires it to be sevicable to extend to 207?

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...:hmm:

Of course, if you blast off into subspace with one generator inoperative, then the APU has to be running whether ETOPS or not.

Is it possible for an Airbus to start the APU at any altitude? Ia always though that APU start can only be done below 25k pressure altitude.

There is no RAT, HMG or HDG for the 737, but it is still ETOPS capable.

The 25K ft limit is when you are in Emergency Electric Config (with no main working generator) - so you need to guarantee a start on the first attempt.

The APU may be started up to FL 410 (it should start within 3 consecutive attempts).

It depends.... Which airbus? And there are also differences within one type/family.

Some are able to start up to 41.500 feet.

hey aussie.. theres no engine failure so whats with galley shedding?

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...

Hey Duyentranvan...Galley Shedding is all to do with the failure of the generators, and not the failure of an engine

dont mess with spanish ... :=

Take a look at the Airbus A320 FCOM Duyentranvan :ugh:

In particular FCOM 1.24.20 p4 Electrical Controls and Indicators

Here is a quote from the manual :

:eek:

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. :eek:

Therefore, unfortunately, the pax CAN NOT enjoy a coffee when the 2 engine stop turning. :eek:

Folks,
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!!