I can't get the engines started

[El padrino 2]

HYD SYS 4 is turned to AUX during engine start to provide pressure to the main brake system.

Good to know (although what I wrote comes from a tutorial) however I can't understand why the brake system should have pressure at this point of the startup procedure. Isn't the plane supposed to be with Parking Brake ON?PS I assume the AUX pressure is provided by the APU...

[El padrino 2]

I'm pretty sure the passengers won't die if all the packs are switched off (on the ground) ;-) Engine start only takes a few minutes... not really long enough for the cabin temperatures to change.

I guess it's a matter of convenience. The packs are more like a suggestion rather than an obligation. I read somewhere that leaving the Left Pack will provide a bit higher pressure compared to the other two. Is this correct?Is it possible (in the real world) to leave all Packs to ON and start then engines or would this lead to other problems?

There may be a requirement to run one pack during engine start due to pressure shock (going from almost no air usage to 50psi during engine start can be hard on the bleed system) However, many aircraft have been modified to allow you to start without any packs without getting excessive pressure shock.

Good and logical argument!

Yet another variation in crew procedures. We pull the start switch first (manual or autostart). No, system logic-wise, it doesn't matter which you do first during Autostart, but I'd be interested to know why Delcom's airline puts fuel on first : )

I think Delcom's order is in the PMDG manual checklist. Fuel first and then pull the switch.Good info, thanks for the feedback folks!

[FLEX1978 373]

Good to know (although what I wrote comes from a tutorial) however I can't understand why the brake system should have pressure at this point of the startup procedure. Isn't the plane supposed to be with Parking Brake ON?PS I assume the AUX pressure is provided by the APU...

Engine start is normally done during pushback, the aircraft still needs brake pressure in case something goes wrong. Also in order to use the parking brake you need brake pressure :) Another reason Engine 4 is normally started first is the provide HYD pressure to system 4 but system 1 is also used for brakes.

[El padrino 2]

Engine start is normally done during pushback, the aircraft still needs brake pressure in case something goes wrong. Also in order to use the parking brake you need brake pressure :) Another reason Engine 4 is normally started first is the provide HYD pressure to system 4 but system 1 is also used for brakes.

Sorry for insisting, but I thought that Parking Brake was functional even when engines are off. How is it possible to park the aircraft if the Parking Brake has no pressure? How are planes kept from moving in reality if parking brake has no pressure and is therefore useless?Is pushback more difficult while engines start? I mean, do engines provide forward thrust (even a little) that makes pushback harder as it applies an opposite power? Is it also safe for the ground crew?

[Turbine777 13]

I enjoy threads like these because it uses the forums in the ways they are better meant to be use, A Knowledge base. So, here is my added contribution.As for engine start procedures on the 747-400 with RR engines. I just dug through some boxes and loaded a great Cathay Pacific dvd. A great video for the 747-400 that is highly recommended for other 744 entusiasts. Their way was as follows:

• Pull ignition switch
  • Duct pressure increases as the APU provides air to the engine (as observed on screen)
  • The outer spool of N3 starts to rotate (as observed in N3 values increasing) and pulls air over N2, and N2 starts to rotate (as observed in N2 value increasing)

  [*]At 10% N2 (This shows a match between the spools) and airflow is within normal perimeters, select that engines fuel to run

  • Fuel flow begins as observed on screen
  • EGT rise observed (exhaust gas temperature) Within 10 seconds
  • EGT is continually monitored at this time to make sure it does not exceed the laid down parameters from the engine manufacturer (for this RR it started to fall (stabilize) at 370)
  • Around this time you may hear a pop, which is the starter motor disconnecting
  • Engine stabilized at about 25% N1 with an EPR (Engine Pressure Ratio) of 1.02

  [*]Proceed to next engine as SOP, and of course as instructed by ground control.

  • There sop (at least back when this was done) was 4,1,2,3 (4 first as explained in an above comment)

To better understand, N1, N2 & N3 are the shafts of the engine.N3 is the outer shaft of a 3 shaft engine with a Compressor on one end and the other end a turbine.N2 is the center shaft, also with a Compressor on one end and other end with a turbine.N1 has the fan on one end (that you see when looking at the front) and the other end is another turbine.The one mentioned here is a Rolls Royce RB211-524H engine (use of this engine, was a reason the -400 was unique, other than the more known "Glass cockpit"), not sure about about the exact parameters for the others,,, PW's and GE's, but it's enough to give you proper understanding. Some other specs can be found here.The video is great, and am surprised it's still available but glad to see it is.

[Turbine777 13]

Sorry for insisting, but I thought that Parking Brake was functional even when engines are off. How is it possible to park the aircraft if the Parking Brake has no pressure? How are planes kept from moving in reality if parking brake has no pressure and is therefore useless?

Tires are chocked when the AC is shut down fully.

[FLEX1978 373]

Sorry for insisting, but I thought that Parking Brake was functional even when engines are off. How is it possible to park the aircraft if the Parking Brake has no pressure? How are planes kept from moving in reality if parking brake has no pressure and is therefore useless?Is pushback more difficult while engines start? I mean, do engines provide forward thrust (even a little) that makes pushback harder as it applies an opposite power? Is it also safe for the ground crew?

You need brake pressure for the parking brake to work, as stated above chocks are put in place when the aircraft is shut down.Engines do provide slight forward thrust at Idle, if the aircraft is light it will start to roll forward. These pushback trucks are designed to move a fully loaded 747 so Idle thrust is not going to make a difference.As far as ground crew safety, Your company will train you properly before putting you anywhere near those beasts and also why you should turn the beacon ON before engine start.

[Guest hangar744]

Yet another variation in crew procedures. We pull the start switch first (manual or autostart). No, system logic-wise, it doesn't matter which you do first during Autostart, but I'd be interested to know why Delcom's airline puts fuel on first : )Cheers.Q>

Q,my airline instructs to pull the start switch first as well, it's just the PMDG bird autostart logic that dictates it otherwise. :( George,rereading my own post from last night again...I think I owe you an apology. I didn't mean to be rude, and to hurt you in any way. Sorry, you are right, we're here to ask, learn, help and share knowledge in order to enhance our experience in our virtual skies.Happy to see all the feedback on engine start.regards,delcom

[El padrino 2]

Q,my airline instructs to pull the start switch first as well, it's just the PMDG bird autostart logic that dictates it otherwise. :( George,rereading my own post from last night again...I think I owe you an apology. I didn't mean to be rude, and to hurt you in any way. Sorry, you are right, we're here to ask, learn, help and share knowledge in order to enhance our experience in our virtual skies.Happy to see all the feedback on engine start.regards,delcom

No need to apologise delcom. I understand that sometimes written speech cannot express what we really mean and may be a bit offensive.However what I wrote is absolutely true; I am more than willing to learn new things and at the same time not afraid to make mistakes, as long as I learn from those and do not repeat them (if possible). Of course in a flight simulation environment this is not of much importance, however since it's something that we all seem to like more than a simple PC game, some additional knowledge is always good!As already mentioned, forums are meant to be knowledge exchange areas and even seemingly silly questions can lead to useful information. Nobody was born knowing 747s, Aux Pumps, ZFWs etc; IMO people who really love something must try to spread their passion through sharing their knowledge with newbies.So no offence mate. The pleasure of getting deeper into this is all mine!

Tires are chocked when the AC is shut down fully.

It's probably the indication of "Parking Brake Set" in FS that confused me as it appears even with engines shut...

[Qavion 19]

The OVRD Pumps 2 & 3 must be on to provide additional fuel pressure for the engines and x-feed valves should be to on in order not to end up with an non-balanced aircraft. CTR L&R tank pumps should also be ON if there is fule in this tank as well.

With such a low fuel load, the airplane will be in a tank to engine configuration. In this case, the OVRD pumps should be turned off. The EICAS shows the fuel quantity in lbs (pounds).Cheers.Q>

[Qavion 19]

Their way was as follows: