Starting 4 engines

[GearDoor]

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.

[Intruder]

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.
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.

[Sky Wave]

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

[GearDoor]

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!

[Carpathia]

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!

[Tonic Please]

I love the 340. Thanks for the link.

Dan

[tournesol]

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:

[Capt Claret]

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! :}

[GearDoor]

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

[Maxiumus]

I've asked why we don't have the same button in the real aircraft but haven't got a sensible reply yet!

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

[Dengue_Dude]

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!

[PAXboy]

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.

[Dan Winterland]

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.

[unowho]

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::

[foxile]

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.

[PAXboy]

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.

[Dan Winterland]

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.

[Wino]

777 starts BOTH engines simultaneously.

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

Cheers
Wino

[BahrainLad]

777 starts BOTH engines simultaneously.

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

[BEagle]

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!

[HZ123]

At BA one engine at a time is started on the 777 and 2 at one time on the 747.

[Cartman's Twin]

Sorry but I despise it! All apart from the -600.

It's a sad day when a 70s vintage 747-100 outperforms an A340 of the deck. Crawling along at 180knts climbing solely due to the curvature of the earth.... The Virgin reports "we are accelerating"..... My a@%e!

In answer to my query "if given further climb can you increase your rate?". The Virgin crew simply replied "Nope!"

Honesty if nothing else!

[PAXboy]

CT: It might be nice to have lots of Ummpphhff but the designer knows the client wants to save money on fuel. :ok:

BEagle: Thanks for the run down. Sounds like good fun. The last time I saw a Vulcan in action was Bournemouth air show in 1989 (I think). They did a low level pass, then eased the nose up and 'put their foot down'. The noise of ten thousand cows bellowing was remarkably sweet. :}

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

[BEagle]

We used to call that the 'Rutting Dinosaur' sound! Great, wasn't it!

[Cartman's Twin]

True BEagle, and dont we dont just know. A340 and ancient DC10 are the only aircraft I've had to pass traffic info on a/c below controlled airspace as they couldn't even keep up with the climb profile on the SID.

Can't help but wonder how it would cope with an engine failure/loss of power. From an ATC perspective, better climb/descent performance makes it far easier to get yourself out of the proverbial hole!

(Not that performance is ever used to ensure separation of course..)

[Milt]

The Roar of the Vulcan.

I'm still hoping to hear from someone who was on that aircraft carrier in Lyme Bay when I did everything but catch a wire before slamming throttles during a pull up.

The carrier wasn't supposed to be there particularly as we had just unloaded a full weapon bay of inert bombs through cloud in the same restricted area.

[Proceed As Cleared]

Yes yes, the A340 (aka transport glider).
A true pain in the @rse... (for ATCOs at least). :{

[GearDoor]

"340" must be some kind of mathmatical code for "doesn't climb worth a crap!" I flew the Saab 340A, and even at a medium weight during the summer, it was painfull to climb past 12000!

PS - Never fly the A model of anything.

[Trislander]

The difference with the BAe 146 of course is that it utilises DC starter/generators. It lacks enough electrical power to start 2 simultaniously!

T

[Khaosai]

Hi Baharain lad, we start both B772/773 engines at once with serviceable Autostart system, except for 300ER which are always started one at a time. Rgds.

Hi gear door, correct 3+4+0=7. Therefore any aircraft with less than two sevens is going to be struggling to perform. Sorry airbus guys.

[Irish Steve]

777 starts BOTH engines simultaneously.

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

Delta used to start both on the push, invariably when the tug being used was one of the weaker ones, and the push back included several tight turns. Depending on how quickly they spooled up, it made things "interesting" on occasions!

On a couple of occasions, I managed to "persuade" the crew to hold the start till the push was completed, as I knew that if they got both turning before we got to where ATC wanted us to be, there was no way that the tug would get it there, it just didn't have the power to fight both engines.

757's used to be interesting in that respect as well, I'm not sure if it's the older design or what, but they always seemed to spool well above ground idle before settling back down to a much lower N1, which again could make push back a little more than interesting.

Classic 747's were the other extreme, the headset man ended up waiting by the nose gear for ever as they spooled up all 4, and one operator required a confirmation for each engine that the fan was turning before they'd continue the start, which used to cause all sorts of problems if the headset that was being used was the normal pushback headset quality. Trying to be heard above the howl of 3 engines live and one just spooling up was sometimes quite challenging. I never did find out why they had to get the headset man to confirm rotation, as it was only one operator that did it, and we didn't get much chance to talk to the crews other than during push back.

[PanicButton]

Do you guy's know of any DVD's about the Vulcan and the Victor?