Engine not starting during pushback - uncommon?

[Fantic125]

Leaving MEL yesterday on QF093 we had commenced pushback from the gate, and was part way out to the apron when the Captain came on the PA and announced we needed to head back to the gate as engine 4 had failed to start.

We trundled back to the gate and were told engineers were on their way to look at it (which they did) and managed to get it started within 15~20 mins, and then we were on our way.

I don't have any complaints about the delay or service, and the rest of the flight was perfectly normal, but it's the first time in the past 20-odd years of flying that I've experienced an engine not starting.

Purely out of curiosity, have any other people had a similar experience?

 

[medhead]

A few years ago the pilot told us the APU was non functional. There was a bit of a delay while they got out the jumper leads.

 

[Flying Fox]

HNL-SYD on a QF 747. We had a failed APU that took 1+ hours to resolve (prior to boarding).

Once we were on board, the APU failed again (according to the captain) and we were told that we could go on 3 but they would like to finalise conversations with engineering in SYD before making a decision.

30mins later it was resolved and we got home without incident.

 

[Ewok]

HNL-SYD on a QF 747. We had a failed APU that took 1+ hours to resolve (prior to boarding).

Once we were on board, the APU failed again (according to the captain) and we were told that we could go on 3 but they would like to finalise conversations with engineering in SYD before making a decision.

30mins later it was resolved and we got home without incident.

There is only one APU on a 747.

 

[harvyk]

Never had an engine not start.

Been on a 737 with a non-functioning APU. The Cap't said over the PA that the start up procedure would be slightly different than normal for this reason. He started engine 1 using ground power ( \ air), we where then pushed back with engine 2 not yet started.

He then said we would be shaken around a bit as he would need to "spool the left engine up to be able to start the right engine". He reved the left engine up (probably putting massive amounts of force onto the brakes which where struggling to keep the plane still) and soon engine 2 was going as well.

 

[NM]

There is only one APU on a 747.

Unlike a BAe146 which has 4, located under the wings

 

[markis10]

There is only one APU on a 747.

On most 747s there is one, however some have two - namely the VC-25's. Interestingly the nightwatch aircraft that accompany the VC-25a stick with the 747 standard APU, I would have thought they would have two as well given the gear thought to be on board.

 

[straitman]

He then said we would be shaken around a bit as he would need to "spool the left engine up to be able to start the right engine". He reved the left engine up (probably putting massive amounts of force onto the brakes which where struggling to keep the plane still) and soon engine 2 was going as well.

I suggest that struggling is really an overstatement and a better wording would be that the brakes were working hard to hold the aircraft.

The brakes will hold the aircraft at or near full power on both engines.

 

[markis10]

I suggest that struggling is really an overstatement and a better wording would be that the brakes were working hard to hold the aircraft.

The brakes will hold the aircraft at or near full power on both engines.

You see that a lot at HTI, especially with the 767 departures

 

[Flying Fox]

There is only one APU on a 747.

Oh??? I'm pretty sure that I recall the story correctly (quoting an APU) but I must be wrong.... yet again.

 

[NM]

Oh??? I'm pretty sure that I recall the story correctly (quoting an APU) but I must be wrong.... yet again.

There is only one APU. The APU provides power for many functions. There are also 4 engines. The engines also have generators that can also be used to provide power for many functions.

The APU is generally used to provide aircraft power when in the ground. Without a functioning APU the aircraft requires a ground power unit/cart. The APU is generally used to provide the required power to start the engines. But once an engine is running, its power generator can be used to provide the power needed to start the other engines.

The APU can also be used during the flight. On many aircraft types its not required to be operation for some flight missions. Each flight mission will have a MEL (Minimum Equipment List) defined. For long over-water flights the MEL may require an operational APU. For short flight it may not require an operational APU. Or the MEL may require/impose other restrictions if the APU is not functional.

I am sure JB747 can provide more specific details about when an APU is used and not used during flight operations, at least for 767, 747 and A380 types. I do expect it is very dependent on the type of aircraft and the flight being operated. So there is not likely to be a simple yes/no answer.

Last year I was on a CX flight HKG-SIN that was changed to depart from a remote stand at HKG. The reason was because the aircraft APU was not functioning and so the aircraft required ground provided air conditioning that was not available at the regular gates. So we were bussed to the remote stand for boarding. A ground generator/cart was used to provide power for engine start and then the engine generators took over the power provision task for the flight.

 

[markis10]

The 747 APU cannot be used in flight above 20000 ft, between 15000-20000 only in a no load condition electrically while providing 1 pack pneumatic pressure/bleed air, it provides power through two generators as well as pneumatic pressure/bleed air. The reference to working on 3 probably refers to the generators on the normal engines in-flight. The twins certainly have an operational APU available in flight, and thats reflected in the different mounting of the door for the air intake.