Hey all,

 

not really a specific NGX related question, but since I'd like to know in the context of me only flying the NGX anyway, I'd thought it wouldn't mind to ask here.

 

Basically, I'd like to know what the most common ground connections are for a typical 737 NG on a European large to major airport (the likes of Brussels, Amsterdam, London, Frankfurt, ...).

 

- Is a GPU common usage, both on departure and on arrival ? Or do they mainly use the APU for power ?

- Is an AC cart common usage before engine start ? Or is the APU used most of the time for bleed air for the packs ? Or does the usage of an AC cart depend on the outside temperature, ie. is it more used during summer time ?

- And is an Air Start cart common usage ? My guess is that most of the time the APU is used to start the engines, but not sure.

 

And how does that all relate to most airports restricting the use of the APU to a minimum for noise abatement ?

 

Also, when a 737 NG is parked on the ramp instead of at a gate, what ground connections are then mostly used ? Are GPU carts common in that case. What about the airco.

 

I guess a lot of the answers to these questions are probably airport specific. Any good resource to find out what the procedures are at which airport ? Is it also company-specific ?

 

Sorry to bomb you with all these questions but I'm still learning and the proper ground procedures and connections are still a bit of an unknown to me, so anybody please feel free to insert your 2 cents (or more if you like :) )

 

Cheers

 

TJ

While googling for my own research, I stumbled upon this page of London Heathrow. Interesting read:

 

http://www.heathrowairport.com/noise/what-we-do-about-it/measures-already-in-place/ground-noise-controls

From my own experience:

 

1) When fuel costs are high you will recieve a company mandate to use ground electrical as much as you can. In most locations, you use ground power often. Whether its a cart, jet bridge connection, from an electrical source that has a cable coming out of the ground or some push back "tractors" have GPUs in them. Most pilots seem to want to use the APU as much as they can.

 

2) AC carts: Only when very high temps in the North East. 99% (totally accurate number I just made up) of the time, it's not needed. It was not normal to have the AC cart still on the aircraft while turning an engine. 99.9% of the time it was APU w/bleed air...

 

3) Airstarts are very uncommon. Typically there wern't many of them (Air Start carts) available for use either. Depending on where you were, some companies do not let ramp agents even connect them to the plane. (Instead ACMX would handle it) Also, Air Start carts are noiser than the APU and GPU. From what I recall, the AirStart cart was louder than most of the new Turbofans at idle.

Ground power and air...Costs a lot of money to run the apus. An airstart is needed when the apu is inop, or the valve that diverts the air from the apu to the engines is inop. An airstart cart does not blow cold air but can be used to create enough duct pressure to run the packs if there is no ac unit available.

Most ground air in real life comes from a hose attached to the jetway too - hard to model in FSX though because the jetways are airport scenery, not part of the airplane.

Ok, so, can I conclude that the most used combo on the ground during preflight is:

 

- GPU for power

- APU for air

 

correct ?

 

Then a related question: most airports I think limit the use of the APU, and I've heard that during a 30 minute preflight procedure (you can guess I'm using FS2Crew) the APU is mostly started only within 10 to go or so.

 

So what air source is used for the first 20 minutes then ?

 

Most ground air in real life comes from a hose attached to the jetway too - hard to model in FSX though because the jetways are airport scenery, not part of the airplane.

 

Ok thanks, we posted at the same time hence my question just below your post.

 

So to mimic reality as close as possible, with the limitations of FSX, I guess GPU and AC cart are the way to go then. The AC cart would then act as ground air from the jetway so to say... correct ?

Why would you have to use an air source, unless the weather is very hot?

Why would you have to use an air source, unless the weather is very hot?

 

Air can be heated as well as cooled. :)

Why would you have to use an air source, unless the weather is very hot?

 

I'm not a regular flyer (maybe once or twice a year for business or holiday trips), but I'm under the impression that whenever I board a plane, the airco is available in the cabin even with the engines not running yet. So it has to come from somewhere obviously...

 

Maybe it's just an impression. I'll try to pay more attention next time I fly.

I just meant that AC is not essential, while GPUs are used 99% of the time, probably due to the high fuel cost and/or airport regulations (usually for noise).

 

Personally I haven't seen GPUs only at small airports where the plane arrives and then leaves in less than 30 mins. Otherwise they all use GPUs.

At my company, if we can board through a jetway, we take Ground Power and AC from there.

If we don't have a jetway but use stairs, we'll often leave the APU running so we have both. If we're on a ramp where they have GPUs, we'll mostly just use the GPU with the APU shut down => No AC.

The following is US Airports (specifically IAD), but EU airports tend to be more strict on noise and environmental concerns:

 

- Is a GPU common usage, both on departure and on arrival ? Or do they mainly use the APU for power ?

Yes. When I worked for Independence Air, our goal was something like no more than 5 minutes after the plane was parked the plane had to be on the GPU (a permanent fixture, not a cart as seen in the sim here, but same purpose), and APU off. For departure, it was up to the crew, but they had a max time before push goal, too.

 

- Is an AC cart common usage before engine start ? Or is the APU used most of the time for bleed air for the packs ? Or does the usage of an AC cart depend on the outside temperature, ie. is it more used during summer time ?

Depends on the carrier and the airport. At IAD, when I worked for United Express, they had pre-conditioned air (PCA) units for every gate. Every plane got PCA (which had a temp switch for hot or cold depending on conditions), unless the crew specifically said to leave the plane alone.

 

As Ryan mentioned, normally, jetbridges of modern airports have both PCA hoses and GPU cords.

 

- And is an Air Start cart common usage ? My guess is that most of the time the APU is used to start the engines, but not sure.

 

Depends on the airline, really, as the use of an air start cart is generally restricted to when the APU is INOP. You rarely see it, as most planes with APUs have functional APUs. For United Express out of IAD, we had a problem with a carrier that goes by a name similar to the geographic formation of a butte or plateau. Apparently maintaining APUs isn't up on their priority list.

 

Air start carts were my worst enemy: none of the rampies knew how to use them (they shut them off without allowing them to cool, which would seize the bearings - instant death to one of those carts, and you don't often see a lot of them). Further, they scream like nothing you ever want to hear. If you're not wearing hearing protection, good luck with the ringing in your ears the rest of your life...

 

 

Depending on where you were, some companies do not let ramp agents even connect them to the plane. (Instead ACMX would handle it) Also, Air Start carts are noiser than the APU and GPU. From what I recall, the AirStart cart was louder than most of the new Turbofans at idle.

I told the rampies that they were to call a sup over after I lost two in one day because they didn't know how to properly start them for warm up, and allow cooldown before shutoff. You're definitely right about the sound. I could hear one clear across the airport. You can often see it, too, as they tend to belch a lot of black smoke when you first start them up (the older ones anyway).

Thanks all for the insight !

 

Very useful info

Thought I'd share this very interesting APU usage document from the Zurich airport website:

 

http://www.zurich-airport.com/Portaldata/2/Resources/documents_unternehmen/umwelt_und_laerm/Technical_Report_APU_Emission_Calculation_Methodology_2005.pdf

 

And from that document I quote this very interesting section about an example of an airline that has implemented the Zurich regulations in its SOP:

 

4. USE OF APU

• Use of APU restricted.

Use APU for ENG – start MAX 5 MIN before block off.

If GPU U/S: Start APU MAX 60 MIN before block off.

APU OPS MAX 20 MIN after block on.

For A320 taxi-in without APU approved.

• ACFT on hard stands: switch off APU when GND Power Unit (GPU) connected.

• Terminal A/B: Preconditioned air and electrical power avbl.

• Energy saving:

The crew shall decide, depending on WX COND or technical requirements, whether air

conditioning is required or not.

Generally, the air conditioning system should be switched off with AOT of APRX 10°C to 25°C.

The air conditioning system should also be switched off after PSGR have disembarked or before

leaving the ACFT.

Well I know that in most European countries It is from on-block and 5 min after and 5 min before off-block. That you may use the APU, I was a rampie last year at CPH. :-)