737, 777, 747, A320, do planes start at the gate on GPU or APU?

[captain420 3,099]

Which is more realistic? I currnetly have my panel state on my PMDG planes set to Short Turn Around which has the plane sitting at the gate with the APU's already running. What is more realistic, to have the plane start on GPU or APU while sitting at the gate? I would like to know also should the plane connect to GPU or APU once it has landed and taxi'd to it's gate?

What's the difference between the short turn around and long turn around panel states in the PMDG planes?

[mwilk 1,106]

30 minutes ago, captain420 said:

Which is more realistic? I currnetly have my panel state on my PMDG planes set to Short Turn Around which has the plane sitting at the gate with the APU's already running. What is more realistic, to have the plane start on GPU or APU while sitting at the gate? I would like to know also should the plane connect to GPU or APU once it has landed and taxi'd to it's gate?

What's the difference between the short turn around and long turn around panel states in the PMDG planes?

At DFW, we were encouraged to hook up the air and electric as soon as the aircraft was chocked and the engines were shut down. That way they could shut the APU down. They would restart it again a few minutes before departure. It didn't always happen that way but that was the procedure.

[Chaos81 110]

1 hour ago, captain420 said:

What's the difference between the short turn around and long turn around panel states in the PMDG planes?

I think the short turn has the IRS aligned and the APU is on. On the long turn I believe the IRS is unaligned and the aircraft is on ground power. I'm sure there are some other differences, but those are two big ones I can think of.

[SAS443 1,722]

In my neck of the woods there are restrictions for APU usage (only allowed to start APU 5 mins before pushback is the norm at Stockholm Arlanda) so for me I always start my session with GPU and Ground Air (when it is necessary)

[SKEWR 364]

Where I'm at, they do not want pilots to light the APU before 10 minutes to departure for any jet aircraft in the fleet due to concerns about the cost of fuel. (GPU is way less than the APU in terms of fuel consumption. Noise abatement was not factored into that decision). This is similar to what I can vaguely recall from the Gulf War period.

[Guest]

4 hours ago, mwilk said:

They would restart it again a few minutes before departure.

 

32 minutes ago, SAS443 said:

only allowed to start APU 5 mins before pushback

 

3 minutes ago, SKEWR said:

they do not want pilots to light the APU before 10 minutes to departure

Which leaves the question: when to start the engines. Engine 1 on GPU and engine 2 on APU using pushback? Or engine 2 and then engine 1 on APU during pushback? I don't suppose anyone would start BOTH engines on GPU, let alone APU?

[costamesa 88]

I start engines during pushback, while on APU. I would be surprised if any normal operation procedure for 777 would require engine start at the gate when the airplane is still on GPU.

[Woozie 732]

On most medium to large sized airports APU usage is restricted to 5-10 minutes before pushback due to noise abatement rules. However, in cold temperatures pilots are allowed to start the APU earlier if cabin heating is required, thats mainly on parking stands as both cabin doors will usually be open. In this case you would switch APU bleed on while remaining on ground power to reduce load on the APU. 

On small airports or remote stands, the number of GPU carts is sometimes limited so you might be allowed to use the APU for the entire turnaround. 

[Woozie 732]

40 minutes ago, J van E said:

Which leaves the question: when to start the engines. Engine 1 on GPU and engine 2 on APU using pushback? Or engine 2 and then engine 1 on APU during pushback? I don't suppose anyone would start BOTH engines on GPU, let alone APU?

On most airports the airplane has to be free of any ground equipment (apart from the pusback truck of course) before engines can be started. Thats why engine start is usually always on APU. However, as engines are usually started in sequence (or 3/4 & 1/2 for 4 engine jets), at least one GEN will be available already when the other engine is being started. 

[Driverab330 74]

Most of the time APU is used for short turnaround or when stable GPU is not available.

 

also quite often the use of GPU at some airports will incur a cost higher than Using APU or when ground air conditioning is unable to either cool down in the cabin in a hot day or keep the cabin warm enough in winter. 

 

The engines are started with bleed air and electricity supplied by the APU unless the APU is inop, in that case the normal practice is to start one engine at the bay on GPU and ground air cart for the 777/A330, after that we can start the remaining engine by using cross bleed start after pushback. 

 

And such procedure has to be carried out carefully with close liasion with ground engineers as having one powerful engine even running at idle at the bay with engineers and ground equipments located closeby is quite dangerous.

 

 

 

 

 

 

 

 

 

[Captain Kevin 586]

Short turn-around panel state has the IRS aligned and APU running, so you're pretty much almost ready to go once you punch in your flight plan and get your take-off data. Long turn-around panel state has the IRS off and GPU running, so you'd have to align the IRS and do all that, then get the APU started when you're ready to go.

[mwilk 1,106]

4 hours ago, J van E said:

 

 

Which leaves the question: when to start the engines. Engine 1 on GPU and engine 2 on APU using pushback? Or engine 2 and then engine 1 on APU during pushback? I don't suppose anyone would start BOTH engines on GPU, let alone APU?

The only time the engines were started at the gate is when the aircraft required and airstart due to the APU being inop or if the APU generator was inop and they needed the ground power to start. In either case, they would start one engine at the gate and the second one after pushback. Under normal conditions, the engines were started during pushback from the APU.

[HighTowers 1,434]

2 hours ago, Driverab330 said:

Most of the time APU is used for short turnaround or when stable GPU is not available.

 

also quite often the use of GPU at some airports will incur a cost higher than Using APU or when ground air conditioning is unable to either cool down in the cabin in a hot day or keep the cabin warm enough in winter. 

 

The engines are started with bleed air and electricity supplied by the APU unless the APU is inop, in that case the normal practice is to start one engine at the bay on GPU and ground air cart for the 777/A330, after that we can start the remaining engine by using cross bleed start after pushback. 

 

And such procedure has to be carried out carefully with close liasion with ground engineers as having one powerful engine even running at idle at the bay with engineers and ground equipments located closeby is quite dangerous.

Ugh hated those ground air starts with the diesel air starts at gate.  So loud.  Mind you that was back in the late 90s so im sure its much improved now. But really had to push a hell of alot of air to get an engine going.  APU inop= headache. 

 

[Driverab330 74]

10 minutes ago, HighTowers said:

Ugh hated those ground air starts with the diesel air starts at gate.  So loud.  Mind you that was back in the late 90s so im sure its much improved now. But really had to push a hell of alot of air to get an engine going.  APU inop= headache. 

 

Still diesel powered these days .... not much has changed I reckon....

 

i had apu inop before going in Dubai (summer), Hong Kong (summer) and Moscow (winter). 

 

Getting the airplane de-ice is just too much trouble involve..... lucky we had a 4 engine airplane back then. 

 

So so we started the engine on one side. Get the other side de ice, start the engine on the finished side, shut down the other side to allow the de ice work to be completed.  : S 

 

[Chock 17,769]

If you are including older 737s in the mix, back before noise abatement etc, it was not unknown for jets to back themselves out of the gate using their clamshell thrust reversers, although it was more common with T-tails with their engines at the back. This is known as a powerback. Stuff like DC-9s and 727s and occasionally 737s would do that and it was approved by the manufacturers on some types, but I suspect it wouldn't be tolerated these days, not least because of the risk of foreign object damage possibilities with high bypass turbofans, and damage to the terminal too lol. But of course when that did used to happen with low bypass turbojets, it would mean the engines had been cranked up at the gate. You can still see some turboprops do powerbacks from time to time.