ok , always using External power to power up the plane.

 

I also attach the Air Start Unit and Air Conditioning unit.

 

honestly I am not very familiar with the air start and air conditioning? but is it better to use them for packs ?

what does air start unit help in the startup and the air conditioning?

 

thank you

 

Air start unit will provide air for engine start-up. This air can also be used to operate the packs when engines and APU are not running.

 

The AIr Conditioning unit will provide conditioned air directly to the mix manifold. This way you can have air conditioning without turning on the packs.

how do you run the air start?

Hi Alex,

If you ask how to connect the air start unit, then have a look at the introduction manual p 0.00.131 (CDU menu>FS action>Ground connection>Air start unit).

If you ask how to perform an external air engine start using the air start unit, then have look at the FCOM v1 p. SP.7.2.
Basically:

1) connect the air start unit, start one engine following normal procedure (but usually engine 1 in this case). 

2) disconnect air start unit and GPU when the engine is stabilized.

3) Perform a crossbleed start for the second engine described in the FCOM v1 p. SP.7.2. (Increase engine thrust until 5% N2 above idle and check 25 psi minimum duct pressure).

The air start cart is rarely used because it is so loud, and probably expensive to the operator.  I imagine at least 95% of all starts are done on APU, which most airports will allow the crew to use up to 20-30 min before push back. Depends on location.  If you have an APU you're going to use it.

I saw an airstart being used on N668US - one of Delta's 747-400s in Detroit last Wednesday. I had a two hour layover waiting for a flight home, and stopped into Leo's Coney Island restaurant for lunch. The restaurant is adjacent to gate A50, and the Queen was parked right outside, so I made sure to get a seat right by the window on the airside. The aircraft was loading for departure to Narita as flight 275.

I spotted the bleed air hose from the pneumatic cart hooked up behind the two much larger conditioned air supply hoses, so I figured that the aircraft might have an inoperative APU.

Sure enough, after the doors were closed, and the airbridge retracted, the ramp crew disconnected the conditioned air hoses, but left the bleed air hose connected. They started engine 4 at the gate. They did not disconnect the bleed air supply hose, or the ground power connection until the engine had been running for about two minutes. They pushed back as usual, and I assume did a cross bleed start of the remaining engines (one at a time) once they were on the taxi line.

i also noticed that the ground crewman who disconnected the bleed air supply line, was wearing high temp firefighter-style gloves, as I imagine that the coupling at the end of the hose was extremely hot, even after the pneumatic supply from the cart had been shut off!

14 hours ago, downscc said:

The air start cart is rarely used because it is so loud, and probably expensive to the operator.  I imagine at least 95% of all starts are done on APU, which most airports will allow the crew to use up to 20-30 min before push back. Depends on location.  If you have an APU you're going to use it.

Here in the States, I don't think you're going to find much of that sort of restriction. That sort of thing is usually found in the EU, with the exception of perhaps SMO over here (which is essentially an EU airport with all of the over-regulation).

I'd also argue that the start cart is rarely used simply because APUs are usually not deferred, and it's a somewhat safer operation. The expensive part is definitely true, however, I think it's more on the fact that the units are expensive, and are usually operated by people who are prone to breaking them. I cannot tell you how many times I had to tell the rampies "turn it on, let it idle for a bit while you wait, bring it up to full power when the crew requests the start, let them start, and once they tell you to disconnect, bring it back to idle and continue to let it run while you disconnect it and tow it away. Again: leave it running while you tow it away so it can cool down." Sure enough, they'd go start one plane and then immediately turn the thing off, which kills oil circulation and causes parts to fuse up, meaning that the next plane that needed it didn't get one that worked. That maintenance bill, of course, will also be expensive. The units themselves are so expensive (and infrequently used) that the operator usually has only one of them, and maybe a second if it's a major hub. If it's an outstation, it's hit or miss, and if there is one, it's usually the airport operator or management company that owns it.

Here in the United States, the most common situation is (based on my memory of UAL/UAX and IDE procedures):

• GPU through the turn
• APU a little while before boarding (unless it's incredibly cold/hot, where the APU would be on through the turn, since gate air is only good within a range of temps)
• APU to start, and turned off after start
• [Flight]
• APU on after landing and clearing
• GPU immediately after chocks, where APU is selected off as soon as power is transferred to the GPU (temp permitting, as above)

Start cart for engine starts is rare, and usually only if the APU (or APU bleed) is deferred for some reason. Similarly, APU to pack takeoffs are pretty rare, except for certain weight situations, or specific airports due to their elevations/temps. Depending on the plane, the start cart procedure can decrease ramp safety (compared to the APU start), because certain aircraft have the high pressure port right next to the engines. Additionally, on an aircraft like the CRJ700/900/1000, you need a ladder to get up to it, and certain ramp management companies cannot differentiate between actual safety and notional safety, putting their people in a bind. As an example, one ramp company specifically forbade using the belt loader as a platform to get up to the port, simply because it was "not what it was designed for." Climbing up a ladder single handed with a semi-pressurized hose, however, was definitely less safe, and not as stable, but was the required method because "that's what a ladder was designed for." One of the many things I've stored in the "if I ever have to write ramp procedures at some point in my life" manual.