Question: When an aircraft has its flight plan filed, and is all set for pushback. Should they start the engine before pushing back, or should they push back, and then start the engine? Does it matter on airline, aircraft, or airport?
Thanks in advance!
-Will
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I think most aircraft start there engine while doing push back or at least one or two the engines then the rest after pushback.đź‘Ť
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Usually, they do it when pushing back, but sometimes, there are things that can be sucked into the engine if they start it whilst pushing back. In this case, they wait for the “ok” from the person walking during pushback to start the engines.
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I’m pretty sure after pushback they’ll have the APU then the engines
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APU is already started well before push back - typically 15 minutes before. Once you are getting ready for pushback the ground power is disconnected- you will already be using the APU as power source by then.
On the pushback the ground crew will tell you when you are clear to start engines. This is usually as soon as you start pushing back, but can be a little way in to the push back depending on what is around you.
The above is fairly typical. However power backs can and do happen - one example was the ATR I was on last week where they start engines on stand and then power back without the need for a push back tug.
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Yeah that’s what I said - they already have APU started then the engines after pushback (i think)[quote=“ATK, post:5, topic:125648”]
APU is already started well before push back - typically 15 minutes before
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You said “after pushback they’ll have the APU then the engines”. The APU is started before pushback.
Anyway, I have given a bit more detail to explain the timing now.
Like already started…
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On the A320 we need bleed air to start, Hence APU is started before push and it also needs to be started so we can disconnect the Ground Power Unit (GPU) If you’re cleared push and start, you start the engines in the push.
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Some airlines do a 1 engine taxi. This is where you start one normally during push, then you turn off APU and taxi to the runway. When near the runway start the other engine.
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have heard of one engine taxi after landing but didn’t think it was that common on taxi out to the hold.
On very rare occasions you start up an engine whilst on stand. A friend was a FO on a A340 with a UK based Red Tail outfit and he told me once that APU had failed and they had to start up on one of the inboard engines on stand prior pushback so that they could take the feed to start up the other 3. Not sure if it was a ferry flight or revenue but he said there was a lot of safety procedures (understandably) in place for it to take place!
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One engine taxis can be common at large airports where taxi times are routinely 10 minute s or more. LHR is one example and BA A320 aircraft normally do a one engine taxi out. The other engine is usually started well before reaching the runway hold point as it needs to run for a few minutes before take-off thrust is set.
For smaller airport and those where taxi times are shorter there is little advantage in one engine taxi when departing so it usually isn’t seen very often.
Failed APU does happen sometimes and I have been on a few flights where it has happened. As you noted, usually you have to start one engine whilst still on stand and hooked up to ground power and ground air. Once that engine is going you can push back and then once the ground crew are clear you use the bleed air from the started engine to start the other.
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every day is a school day! Makes sense, have sat in the queue at LHR for a few minutes once or twice whilst waiting for our slot!
That makes sense. Also on quad jets you could just use the inner 2 engines to taxi. With tri jets i will probably use 2 to taxi and start up 3rd later
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The 747 is different though right? If I remember correctly they always start engine 4 because it has the hydraulics needed for nose steering or something along those lines. I think :)
I’m not really sure. I know on 2 engine planes they normally start engine 2 first I’ve seen that on the a320 and 737 so that right side might have somthing like that on a lot of plane.
Yeah that seems to be the case with most twins. Maybe the quadjets are more varied.
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Depends with the twin jets. What drives the decision is which side the ground air plugs in to. If it goes in the right side then the cart and crew can remain on the right side whilst you start engine 1 on stand.
With a 737-800 it is normally engine 1 you would start on stand if the APU was unavailable. Where the APU is running as normal I think the start sequence during push back would be 2 then 1.
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This might be wrong, but I heard for the a320 series you start while pushing, unless its de-icing conditions, then you start after push is finished.
Oh, I know all about the 320. I relentlessly pester @RAH with just about any aviation related question I can think of.
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