Air NZ: NZ1 - New York to Auckland.

Forums › Travel (planes, train, cruise) › Air NZ: NZ1 - New York to Auckland.

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#2972323 23-Sep-2022 21:53

Air NZ advised the fuel stop was due to “unusually strong winds in its flight path”.

I'm not a pilot, but some observations on fuel for taxing.

Airports will Queue planes at the gate, to avoid excessive numbers of planes queuing.
Some planes have a greater max ramp weight, than max take up weight, meaning that the pilots can take on fuel above max take off weight, such that estimated taxi fuel does not impact their flight range. (obviously if they take too much they won't be able to take off untill they have burnt enough to get their weight down to max take off weight).

Above means that taxi fuel burn would only likely to be an issue if the taxi duration was unexpected.

Perhaps one of the pilots here could advise if adding a fuel stop to the flight plan while waiting in the queue to take off would be viable. Obviously the pilots could instead opt to drop out of the queue, in order to take up more fuel, but I understand that would mean they go to the back of the queue...

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#2972324 23-Sep-2022 21:54

tdgeek:

Im not a pilot, although I have piloted (thanks Brent)

I doubt that idling for 60 minutes will burn the circa 10% that is carried in reserve. Plus, if the delay was that long, cut the fuse?

@Technofreak and others can comment more accurately.

All internal combustions engines use some proportion of the power produced in the combustion process just to drive the engine, this is particularly so for turbine engines. To give an example, I remember being told many years ago about the Allison 250 engine used in the Bell Jetranger and Hughes 369 (500) helicopters. I don't remember the exact figures but from memory the gas generator on that engine produces about 1000 hp but only 400 HP or so was left over to power the helicopter. Turbine engines are a very efficient power source when you need a lot of power but they consume a lot of fuel at idle in comparison to what they use at high power.

I have no idea what the figures are for a turbofan engine as fitted to the 787 but can see how sitting waiting for take off would chew through quite a bit of fuel.

I'm not entirely sure what you mean by "cut the fuse" but guess you mean shutdown. That's not generally an option for a multitude of reasons.

The aircraft will most likely have taxied off the gate because there will be another aircraft wanting that gate so there will be no longer any ground services.

All the systems on board the aircraft derive their power from the engines, things like the air conditioning. It gets warm pretty quick from all the heat generated by the people on board and the air gets stale very quickly without air conditiioning working. Plus theres all the other systems that need powering.

If the aircraft doesn't start taxying they will probably lose their place in the departure queue, plus there's probably no where for them to park anyway as they will be blocking the pathway for other aircraft.

At many large airports the taxy time can be 30 minutes or more anyway. An hour at idle power may only be a delay of 30 minutes.

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#2972329 23-Sep-2022 22:07

There appear to be pretty horrid delays getting out of JFK this evening,

Probably UN leaders related,

I was in an Uber getting in to Manhattan, and the traffic was absolutely at a crawl anywhere near the UN. Police just shut down anything within miles of the building. It was about 1 1/2hr to get from LGA to the city. My Uber driver recons for the 8:55pm flight out on NZ1 on Monday leave the city at 4pm.

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#2972330 23-Sep-2022 22:09

See my responses in Bold

Scott3:

Air NZ advised the fuel stop was due to “unusually strong winds in its flight path”.

I'm not a pilot, but some observations on fuel for taxing.

Airports will Queue planes at the gate, to avoid excessive numbers of planes queuing. Not normally an option as the gate will be required for arriving aricraft.
Some (pretty well all commercial aircraft) planes have a greater max ramp weight, than max take up weight, meaning that the pilots can take on fuel above max take off weight, such that estimated taxi fuel does not impact their flight range. (obviously if they take too much they won't be able to take off untill they have burnt enough to get their weight down to max take off weight). Max Ramp Weight will generally be used on these flights as a matter of course.
Above means that taxi fuel burn would only likely to be an issue if the taxi duration was unexpected. Correct, unless the normal taxy time/distance is such that more fuel will be burnt than that, that makes up the difference between Max Ramp and Max Take Off

Perhaps one of the pilots here could advise if adding a fuel stop to the flight plan while waiting in the queue to take off would be viable. It's my guess the take off delay was only one fairly small part of the problem, the major part was the en-route headwinds. The en-route fuel stop was probably always on the cards and was likely to be needed irrespective of the ground delay. Obviously the pilots could instead opt to drop out of the queue, in order to take up more fuel, but I understand that would mean they go to the back of the queue...With risk they end up with a rinse and repreat scenario.

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#2972409 24-Sep-2022 07:26

Technofreak:
tdgeek:

Im not a pilot, although I have piloted (thanks Brent)

I doubt that idling for 60 minutes will burn the circa 10% that is carried in reserve. Plus, if the delay was that long, cut the fuse?

@Technofreak and others can comment more accurately.

All internal combustions engines use some proportion of the power produced in the combustion process just to drive the engine, this is particularly so for turbine engines. To give an example, I remember being told many years ago about the Allison 250 engine used in the Bell Jetranger and Hughes 369 (500) helicopters. I don't remember the exact figures but from memory the gas generator on that engine produces about 1000 hp but only 400 HP or so was left over to power the helicopter. Turbine engines are a very efficient power source when you need a lot of power but they consume a lot of fuel at idle in comparison to what they use at high power.

I have no idea what the figures are for a turbofan engine as fitted to the 787 but can see how sitting waiting for take off would chew through quite a bit of fuel.

I'm not entirely sure what you mean by "cut the fuse" but guess you mean shutdown. That's not generally an option for a multitude of reasons.

The aircraft will most likely have taxied off the gate because there will be another aircraft wanting that gate so there will be no longer any ground services.

All the systems on board the aircraft derive their power from the engines, things like the air conditioning. It gets warm pretty quick from all the heat generated by the people on board and the air gets stale very quickly without air conditiioning working. Plus theres all the other systems that need powering.

If the aircraft doesn't start taxying they will probably lose their place in the departure queue, plus there's probably no where for them to park anyway as they will be blocking the pathway for other aircraft.

At many large airports the taxy time can be 30 minutes or more anyway. An hour at idle power may only be a delay of 30 minutes.

All onboard systems such as air conditioning are powered by the APU while the aircraft is in the ground with the main engines off. The APU is a relatively tiny gas turbine in the tail of the aircraft.

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#2972411 24-Sep-2022 07:36

johno1234: All onboard systems such as air conditioning are powered by the APU while the aircraft is in the ground with the main engines off. The APU is a relatively tiny gas turbine in the tail of the aircraft.

Not if there’s a PCA (preconditioned air AHU) and GPU (ground power unit) on the gate or hard stand.

There’s a significant scope 3 emissions savings by doing this.

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#2972413 24-Sep-2022 07:43

Technofreak:

All internal combustions engines use some proportion of the power produced in the combustion process just to drive the engine, this is particularly so for turbine engines. To give an example, I remember being told many years ago about the Allison 250 engine used in the Bell Jetranger and Hughes 369 (500) helicopters. I don't remember the exact figures but from memory the gas generator on that engine produces about 1000 hp but only 400 HP or so was left over to power the helicopter. Turbine engines are a very efficient power source when you need a lot of power but they consume a lot of fuel at idle in comparison to what they use at high power.

I have no idea what the figures are for a turbofan engine as fitted to the 787 but can see how sitting waiting for take off would chew through quite a bit of fuel.

I'm not entirely sure what you mean by "cut the fuse" but guess you mean shutdown. That's not generally an option for a multitude of reasons.

The aircraft will most likely have taxied off the gate because there will be another aircraft wanting that gate so there will be no longer any ground services.

All the systems on board the aircraft derive their power from the engines, things like the air conditioning. It gets warm pretty quick from all the heat generated by the people on board and the air gets stale very quickly without air conditiioning working. Plus theres all the other systems that need powering.

If the aircraft doesn't start taxying they will probably lose their place in the departure queue, plus there's probably no where for them to park anyway as they will be blocking the pathway for other aircraft.

At many large airports the taxy time can be 30 minutes or more anyway. An hour at idle power may only be a delay of 30 minutes.

Thanks for that. I thought if the delay was an hour they could shut the engines down and wait using the APU, to save fuel

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#2972422 24-Sep-2022 08:23

tdgeek:

Thanks for that. I thought if the delay was an hour they could shut the engines down and wait using the APU, to save fuel

Unfortunately the delay is often after pushback but before take off. The portion of the journey where ATC will require you to move the aircraft on a regular basis. Added to that is the fact that turbine engines don’t like thermal cycles, particularly short duration ones. So starting and stopping engines frequently has a maintenance burden (and cost). Many airports have “co-ordinator” frequencies whose sole purpose is to organise the queue and provide start times so that there aren’t too many aircraft in the departure queue (wasting fuel). The flow on effect of that though, is inbound aircraft are left waiting for gates and congesting the tarmac. However, from a safety perspective, a landed aircraft is of lower priority.

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#2972434 24-Sep-2022 09:43

With an efficiency of only 8-14%, I wouldn't trust the APU alone to have too much fuel-saving potential with a fully occupied cabin on the apron. A single engine taxi out for a twin engine would be more of a solution - and would also be sufficient for the ECS. Cross Bleed Valve to open, Pack 1+2 on and here we go. :-)

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#2972480 24-Sep-2022 12:52

And, in the end, the weather conditions improved on route, so the planned fiji fuel stop was able to be scrapped. (guess they took up fuel to max out their take of weight in New York, in hope of improving conditions).

https://www.stuff.co.nz/travel/travel-troubles/300696817/air-nz-flight-from-new-york-touches-down-in-auckland-after-avoiding-fiji-diversion

Interesting quote:

“Refuelling in Nadi is our standard contingency plan for these circumstances and has also been used in previous years for other routes on our network.”

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#2972483 24-Sep-2022 13:38

Diversion Decision Point (DDP) flight plan.

Fuel above level prescribed at DDP = Continue to AKL (with required reserves).

Fuel below level prescribed at DDP = Divert to NAN.

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#2972656 25-Sep-2022 00:24

Sam, I presume gets flown basically everywhere free now. Just to review.

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#2972767 25-Sep-2022 17:21

@sbiddle and other frequent flyers ... the seats seem to have gone backwards?

i recall precovid the business class seats seem bigger and you could lie flat by pressing a button the moment you get on the plane

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#2972795 25-Sep-2022 18:58

Voluntary offload and free hotel again

https://www.nzherald.co.nz/nz/air-new-zealand-new-york-direct-troubled-route-hits-more-issues-as-passengers-paid-to-offload/T6JYYDEABZDWAKH3QWUZCP26NQ/

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#2972841 25-Sep-2022 22:34

I'm struggling to come up with a reason why I would take this flight.

I can see the advantage if I was heading for LHR: land in New York with only a relatively short transatlantic hop (could have been very short indeed if Concorde still flew!) but to be honest it looks very marginal from a reliability pov as a passenger. I think I would opt for LA or Houston then go from there.

We were looking at flights to UK/Europe for next year and to be honest we considered this route for all of 30 seconds before picking a 4 day stop in Singapore each way instead. 17 hours just does not appeal to me, even if someone else was paying for Business. Maybe in an Emirates Suite or something but nothing less.

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