Starting 4 engines
 

Hi,

When you are starting up a 747 or 340 or something similar, I am under the impression that you can start two engines simultaneously. Is this correct? I suppose you would require an APU with an air output sufficient to spin two starters.

The reason I ask is that I watched a video of an 340-600 starting up and taxiing out, and they would start #1, pause, then start #2 while #1 was still spooling up. When #1 was at idle, #3 was started. When #2 was idling, #4 was started.

One thing that was interesting was how wide that jet has to take corners while taxiing!! It looked as though the captain was going to do some 4X4 ing, but looking at the cameras on the tail and behind the nose wheel, you could see that he had everything under control. Really cool.

On the 744 the APU is powerful enough to start 2 at a time, with 1 pack running. We routinely start 3+4, then 1+2. With ground air, only 1 at a time can be started, and usually the pack has to be turned off as well.

GearDoor

Sorry it's off thread but I've not seen a 340 cockpit video. Is the video commercially available and if so who's it by and would you recommend it.

Cheers

SW

It should be here:

www.a340.net

Click on multimedia, video library, a340 cockpit, takeoffs.

PS - Neat, you can save time starting engines, AND have the air conditioning running!

You can't start 2 at a time on a 146. Then again, my girlfriends hairdryer is significantly more powerful than a 146 APU.

Ah, I've just seen the question refers to "747 or 340 or something similar". Persumably something similar would refer to a real aeroplane so disregard first paragraph!

I love the 340. Thanks for the link.

Dan

Adition to what Intruder posted, yes you can start 2 engines at a time on a B747-400. On a classic/SP the normal way is to start one eng at a time. Preferably 4,3,2, & 1.
:ok:

Well in the (146) sim all 4 engines can be started at once. I've asked why we don't have the same button in the real aircraft but haven't got a sensible reply yet! :}

Funny how in the sim, all four can quit at once too!!:eek:

Persumably because the sim is about 20 years more technically advanced than the real aircraft!

Carpathia
 

Having taught that aircraft at BAe, I thought your girlfriend's hair dryer WAS the APU.

The APU is actually a cunning term for tail mounted ballast, required to keep the aircraft in trim.

A proportion of aircraft actually have functional ones fitted in order to keep the CAA Ops Inspectors fooled (easier done than said from what I hear).

Take care all , at least you don't have to worry about Rollback anymore!

Thanks DD, I always wondered why, in a 146, the Cap asks us all to pull down the 'oxygen' mask and then says, "All together 1-2-3 BLOW!!!" :}

We don't even get a discount. :8 So when I board a 146/RJ on Monday morning, I'll refuse to blow, unless I get paid.

--------------------
"I tell you, we are here on Earth to fart around, and don't let anybody tell you any different." Kurt Vonnegut, Jr.

If you try to start 2 at once in a classic, nothing will happen. The 744's APU has a considerably greater air output. You can even run a pack while starting 2 at once. On the classics it's strictly one at a time with no packs.

Off Thread
 

Sorry for the tangent, but if the old grey matter is still functioning I think the V force (Victor and Vulcan) could start all 4 at once. I'm sure Mike Jenvey will lets us know::

unowho

Think you are correct.

As a wee laddie living next to RAF Waddington in the late 70s the four ship Vulcan scrambles were a sight to behold. Three a/c on the runway at the same time in various stages of take-off.

I seem to remember, although it was a while ago, that all four a/c had to be airborne within something less than three minutes from the time of the alert. Will stand corrected on the exact timing though. Consequently I think a four engine start was a must.

Yes, this was discussed a year or so back and, IIRC, the V Force had a ground truck attached and ready to go. Someone said that you had to make sure the park brake was well and truly set before you gave the thumbs up!!!

Also, something about the fact that there was a limit on how many four engine starts you could do per year, due to fatique on the airframe!! But I sit to be corrected.

The Victor and Vulcan Mk2s had a rapid start system. It was known as combust start on the Victor and ripple rarid start on the Vulcan. I can't speak for the Vulcan system, but the Victor system worked like this.

The aircraft would be 'combat checked' i.e. all checks up to engine start already completed. On arrival, all the crew had to do was strap in and commence the start sequence. All four could be started at once. On selection of start, the contents of a high pressure air bottle were fed into the 'combustor' which was a cylinder with a perforated piston, one side of the cylinder contained fuel, the other side is where the air went in. The air forved the piston down the tube, the fuel was pushed through the perforations and atomised. At some point, the mixture was ignited and the results fed into the air starter motor. This wound the engine up to 75% rpm in a matter of a handful of seconds as the generated pressure was in the region of 300psi - normal air start pressure was 30. the exhaust was fed out under the engine and was pretty impressive to say the least.! On QRA scrambles, it was the groundcrew's responsibility to make sure they were not under the wing once the door had been shut. If they were and the 'tit' was pressed, it was curtains.

On the tanker version we still had it installed, but only on engines 3 and 4. It was handy at civil airfields when there was no goroung power available and we could start on battery power alone. Although a careful briefing to ATC was useful - otherwise you would attarct the attention of the airfield fire services fairly quickly.

The Vulcan ripple rapid started the engines in sequence - hence the name. I think it could be started from a button on the noseleg - a former 'flatiron' driver will no doubt confirm or 'pooh pooh' this.

777 starts BOTH engines simultaneously.

A300600r could start both engines at the same time as well (Saw a mechanic do it)

Cheers
Wino

777 starts BOTH engines simultaneously.

I'm sure it can, but does any operator do it as part of their SOPs?

There were many ways of starting a Vulcan...

Originally, back in 'Great White Deterrent' days there was the 'Mass rapid' system which used fuel/compressed air combustors to start all 4 engines simultaneously, all the PFCUs and would put all the alternators on line. This put an enormous strain on all systems and was true 'Soviet missiles inbound' stuff.

The combustor 'rapid start' system was retained in later years, but it was frequently only partially serviceable (it required compressed air bottles and trunking in the wings to be serviceable...) and was normally only required when there wasn't an external air start available (such as on the ORP). You set the throttle of the appropriate engine at 50%, then pressed the button. "Owwwoooohhh"-once it started, you brought it back to idle to shut off the rapid start fuel bleed.

The more normal technique was to use external air to start one engine at a time.

However, if all the bottles and ducting were serviceable, you could start all 4 one after another in a rippled sequence - colloquially termed a 'ripple rapid' start. Usually the captain would look after 1&2, the co-pilot 3&4... Owwwooohhh, owwwooohhh, owwooohhh, owwwooohhh - then see how many had actually started - it took mere seconds!

If there was time, but no external air, you could rapid start a single engine, then crossfeed 'engine air' bleed to start the others. There were 2 ways of doing this; either you rapid started one, then set it at 70% and started the other 3 one by one - or more dramatically set it to 93% (very noisy and hazardous!) and started the other 3 simultaneously using the 'engine airs' instead of external air. The Crew Chief was supposed to confirm that it was 'clear behind' before doing a 93% crossfeed start. My captain decided to do a 93% start at Goose Bay once when we'd been delayed - and sandblasted all the cars in the car park behind!