APU operations

[BAW9DV 2]

Good evening,Sorry, you still don't give your name so I can't greet you properly...>>Sorry for the delay. The information I posted above was directly from the latest version of the BA flying manual, so is fairly correct. However in order to authenticate it I have just spoken to acurrent senior captain on the jumbo with BA.<

[Triple7 1]

Hello Lee,"Hmm, this is interesting! There must be conflict in the ranks! I also re-checked my information with the FO I flew with, in the BA 744 simulator with on my 50th birthday present in 2006. His information, along with that stated by my friend's wife who also flies the 744 for BA, is contrary to what you say here."There is no conflict in the ranks. The information you posted is wrong. "They both insist that packs 1 and 3 are turned OFF during start - unless there is a good reason for doing otherwise. So far neither of them can recall a time when they ever stared up with all packs OFF, neither did they carry out a takeoff with all packs OFF - again, packs 1 and 3 were left ON."That information is old. The procedure I outlined is the current procedure."They further confirm that takeoff is performed with packs 1 and 3 OFF unless the takeoff weight is over 300 metric tonnes (as you say)."Again old information."You don't give your name or any indication of what business you are in so I find it hard to accept your version stated here against the statements of my colleagues in the Airline."Personally I have no connection with BA. However the information I posted come from the BA Flight Manual (latest edition) and from a BA Senior, current, captain - oh who also happens to be a training captain for them too!Perhaps your friend FO could book in with him for some additional SOP training?"However, the disparity between these statements might just be down to the way some commanders fly, whilst the BA manual serves only as a guide to general practice."Err no. Things such as packs are SOPs and do not differ at all between commanders or crews."As well as three hours in the 744 sim at Cranebank, which was a 50th birthday present for me from my wife and BA friends - and sitting in the cockpit for the complete 11 hour 58 minute flight from Tokyo to Heathrow in July of 2000 - at no time did we ever use all packs OFF - in fact it was the pack 1 & 3 OFF regime that was used - also at Tokyo prior to startup and takeoff."Like I say that is the old procedure and not the current state of play."I suppose if you ask five BA line pilots the same question you may well get five different answers!"No you won't.Cheers

[VHOJT 165]

Hi there Triple7:You pretty much repeated what I said old chap!:)CheersRudy

[cavaricooper 2,613]

Thanks for the information guys! As a slightly rabid BA Virtual Afficianado, I am always looking for BA SPECIFIC procedures. ALL INPUT IS GREATLY APPRECIATED! Now, to complicate things a bit further, since the APU serves as backup electrical for the Captain's Flight Instruments, why is it impossible/inadvisable to start in-flight? I'm totally ok with SOP for normals, but in case of an emergency, why is it impossible to derive electrics and bleed from the APU? I haven't tried an in-flight APU start in the PMDG yet, and can't remember ever trying it in PS1......anyone?Best-Carl F. Avari-Cooper BAW0225http://online.vatsimindicators.net/980091/523.png

[Qavion 19]

"Now, to complicate things a bit further, since the APU serves as backup electrical for the Captain's Flight Instruments, why is it impossible/inadvisable to start in-flight?"The APU is NOT a "backup electrical" for the Captain's Flight Instruments... The APU BATTERY is, however.The APU cannot provide electrical power in the air (it's locked out by the air-ground sensing system). HOWEVER, I have heard that if ALL FOUR engine generators fail in flight, that some 744's are modified to allow the APU generators to provide full electrical power to the main busses. However, if the APU has already been been turned off, you're going to have problems as you can't start the APU in the air (it is also prevented from operating by the air-ground sensing system)Cheers.Q>

[Triple7 1]

Qavion put it much better than me ! ;)

[BAW9DV 2]

Hi there,I find it a real pity that someone who states that he has no connection with the real British Airways, is unable to accept the possibility that his information might be incorrect.I was certainly able to accept that possibility - which is why I re-checked the information and discovered that it was in fact correct.Your suggestion about me asking my friend to check in with your Training Captain for some additional SOP training is unfortunate and rather offensive - and confirms my initial suspicion that your claims about having the correct information here might in fact be highly questionable. However, i don't intend to degrade the thread further by pursuing that line of enquiry.Its a pity that a really useful thread here has been threatened somewhat by your unprofessionalism in your remarks about my friends who are serving line pilots on the 744 with BA and have been for some time. I was certainly prepared to listen to the possibility that you might be correct. Now, unfortunately I cannot do that.I am always happy to be corrected if my information is wrong - which I'm satisfied that it isn't in this case - but you seem rather upset and offensive in your tone when your opinion is questioned here.A real pity. I had hoped that the discussion could have gone forward.In this case, I am satisfied with regard to the procedures and the information I have been given. And I'll take no further part in this discussion as I have answered your threatening tone and wish to go on to better things.My best regards,Lee

[Qavion 19]

"Your suggestion about me asking my friend to check in with your Training Captain for some additional SOP training is unfortunate and rather offensive - and confirms my initial suspicion that your claims about having the correct information here might in fact be highly questionable."On the contrary. It never hurts anyone to recheck their "facts". Both F/O's and Training Captains have been known to be wrong from time to time. Ask Mr Randazzo :(Re the one pack/no pack debate for start. This is dependent on the modification status of an aircraft. It was found on aircraft with older pneumatic system software (or hardware... can't remember), that the shock to the pneumatic system was too great going from "no packs" duct pressure to "main engine start" duct pressure. For a while, it was necessary for crews to select at least one pack on during start. Some crews may still use one pack out of habit (or can't find information in their books stating for sure which aircraft have been modified). I don't recall seeing any amendments in our maintenance manuals, so we usually do the same thing. Having one pack is not going to hurt the engine, whereas no pack might.If I get the opportunity, I'll ask a BA crew this week about procedures... Pilots sometimes have different views/recollections on certain matters however... So I'll try to catch them when there are at least 3 in the cockpit ;)Incidentally, I was originally under the impression that APU~Pack ops was dependent on weight AND temperature.... but I'm quite willing to accept that _I_ am wrong on this issue.Regards.Q>

[BAW9DV 2]

Hello Q,>>On the contrary. It never hurts anyone to recheck their>"facts". Both F/O's and Training Captains have been known to>be wrong from time to time. Ask Mr Randazzo :(<>Re the one pack/no pack debate for start. This is dependent onthe modification status of an aircraft. It was found on aircraft with older pneumatic system software (or hardware...can't remember), that the shock to the pneumatic system was too great going from "no packs" duct pressure to "main engine start" duct pressure. For a while, it was necessary for crews to select at least one pack on during start. Some crews may still use one pack out of habit (or can't find information in their books stating for sure which aircraft have been modified). I don't recall seeing any amendments in our maintenance manuals, so we usually do the same thing. Havingone pack is not going to hurt the engine, whereas no packmight.<>If I get the opportunity, I'll ask a BA crew this week aboutprocedures... Pilots sometimes have different views/recollections on certain matters however... So I'll try to catch them when there are at least 3 in the cockpit ;)<>Incidentally, I was originally under the impression that APU~Pack ops was dependent on weight AND temperature.... but I'm quite willing to accept that _I_ am wrong on this issue.<

[cavaricooper 2,613]

Thanks Q and all others! I appreciate the information and look forward to utilizing these procedures in my "flights" :). One of PMDG's greatest strengths is the RW aviation community that frequents this forum and I am grateful for all the viewpoints.Best-Carl F. Avari-Cooper BAW0225http://online.vatsimindicators.net/980091/523.png

[Qavion 19]

"Yep, fair enough. For newer variants or brand new versions of the 744, this makes sense to me. However, I don't know that BA have bought any "new" 744's - and by that I mean recent -"The modification was carried out, progressively, on older aircraft (perhaps in the last 5 or so years). I'm still not sure if all our aircraft have been modified. It's probably the same for BA.... Not all the crews may know if all their aircraft have been modified, so they are still reverting to one pack starts.I haven't really paid much attention to it (until now). Next time I do a pushback, I'll listen for pack shutdown (above the noise of the tug and the APU).It may have taken time for the effect of rapid duct pressure changes to be known. The Classic 747's have a different bleed demand system and possibly a weaker APU, so the effect is relatively new. OTOH, maybe the effect has been known for a long time, but the cause has not.Note that there are hundreds of system-related memos issued each year... It's difficult to keep track of all of them. Cheers.Q>

[Triple7 1]

Hello.I'll admit I am wrong if it makes you feel better?However to admit I am wrong also means that the Flight Manual is also incorrect.To admit I am wrong also means that the procedures and techniques been taught to pilots during their type conversions, type ratings, line training, line checks, sim checks, etc are all wrong.That reminds me to let the CAA know to revoke the TRTO status of BA!Like I have said in my previous posts the information you are posting about the packs is the OLD procedure. It used to be correct, it no longer is. The CURRENT procedure is the one I outlined.However we will end up going around in circles. P.s. I notice on the checklist that you created on the speedbird online forum it says "packs ... OFF" ;)

[cavaricooper 2,613]

Q (with the maintenance background) and others-Why did Boeing lock out the APU through the ground sensing system? There are other aircraft that allow for in-flight starts. Even in the 744 APUs can continue to run in the air (up to FL200 if I recall correctly). I realize the possibility of 4 generator failure, or 3 pack (a and b I suppose make 6) failure is tiny, but wouldn't it make sense to allow for a redundant system already on board to be utilized to its full potential? Is there a negative present that I am unaware of?BTW if anyone has a copy of RW BA checklists and wouldn't mind sharing, I'd LOVE to find one in my inbox!!!!Thanks!Best-Carl F. Avari-Cooper BAW0225http://online.vatsimindicators.net/980091/523.png

[RaptyrOne 1,398]

Great thread:A quick question then - if only one pack was running at start, which one is used? Two or Four perhaps?GregH

[cavaricooper 2,613]

Greg:Worldwide, the preference seems to be Pack 1 (of the 3 packs) as it conditions the cockpit air the best ;).BA seems to prefer pack 2, isolated and on APU- perhaps as it is the most central......??Hope that helps!Best-Carl F. Avari-Cooper BAW0225http://online.vatsimindicators.net/980091/523.png