737 centre fuel tanks

[BISH-BASH-BOSH]

I have been advised by the fuellers here this morning that various operators in Dublin, as of this morning are placing a minimum fuel load in the ctr tank of thier 737's,anyone aware of what the basis for this thinking is.All i can find is a faa ad on thier site regarding operation of ctr tank fuel pumps in a empty tank to be implemented by 10/05 (boeing amendment 39-12201),cos its the weekend and we have no support from our qc during this period,can you enlighten me as to the situation, all info greatly recieved before we drop a clanger on a third party aircraft.

[spannersatcx]

Sorry don't know the answer, however you raise the point that you do not have 24hr cover from Quality, surely there must be somebody on call from QA, how can you operate without it? Next you'll be saying you don't have Tech Services support either?

[OLD_EGG_BOUND]

Maybe to stop the pumps from overheating when running dry try the 27 April AD link from this page below

www.b737.org.uk (http://www.b737.org.uk)

[BISH-BASH-BOSH]

Well spanners you raise an valid point there, We get f*** all support from the company, this is a sore point with me, this is the first and last company i will work for that has only one person on shift at a time covering a seventeen hour day on a split shift( we are told this is ok by our french management) on a four on four off basis. This is only one small reason why next week will be my last with this company.

[avmech]

Here in the states we had an issue come up with the float sw's for fuel valve shut-off.apparently this all stems from the TWA 800 accident.The first step of the process in"fixing" this problem was to de-activate the top-off float sw.'s.When these sw.'s are de-activated, the center tank can only be filled to a pre-determined maximum, well short of actual capacity for obvious reasons.The next step is to replace the wiring into the tank and add an upgraded type float sw.Once this is accomplished, normal operation is restored.Hope that helps.

[SchmiteGoBust]

Our tech support are available 24 hours 365 days, Spanners!! They even come out and help on Christmas day night with wheel changes in the snow and get paid a pittance....MY ARSE!

[Dragonspet]

BBB
It is my understanding that an Aircraft exploded on the ground on March 03, 2001 it was a Thai Airways 737-400 series. The source of the explosion was comfirmed to have originated from the center tank.After sitting approx. 40 minutes. An Airworthiness Directive has come down the pike ref. AD 2001-08-24 incorporating a revision to the flight manuals stating the importance of prolong operation of the fuel pumps when dry, due to the heat generated in a confined area filled with vapors could be a cause for ignition. This AD will have an effectivity date of MAY 10, 2001.
Not saying the two are related as an official statement has not been forthcoming, but the chronological chain of events insinuates relevance.
Good day to all...

[This message has been edited by Dragonspet (edited 01 May 2001).]

[lame]

It is a little deeper than that.

Centre tank pump switches must NOT be on unless 1000 LBS (453KGS) of fuel in centre tank, except for defuelling or transferring.

Any time the pumps are on, someone must be in the cockpit monitoring them, and they must be turned off as soon as the low pressure lights illuminate.


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"I USED to be a PPRuNaholic, but now I'm CURED"

[Dragonspet]

Hey "LAME"
"Sometimes a cigar is just a cigar"
The fact that qualified personnel are to be in the cockpit goes without saying, as we all know safety protocol is strictly adhered to in this industry.The above mentioned incident did however occur shortly after refueling of the wing tanks so the pumps would have been on IAW procedure, perhaps the low pressure caution light was burnt out it really doesn't take much heat to ignite jet fuel I think thats why it works so well.
Occasionally things are simple, as engineers do we not search for the simplest solution first in an effort to eliminate possibilities?
If you would like to read more log onto this website , most informative.As I said purely speculation on my part but I see the connection.
http://sea-web-01.ca.boeing.com/field/FTQAPLANNING/Website/Pw051/AD2001-08-24pdf.pdf


"Arguing with an inspector is like wrestling with a pig in mud, after a while you realize the pig likes it"

Whats that I hear a beer calling see ya!

[lame]

Tried to several times, doesn't seem to work?


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"I USED to be a PPRuNaholic, but now I'm CURED"

[Blacksheep]

Don't b*gger about with mirror sites. Go direct to the origin at
http://av-info.faa.gov/ad/AD.htm

and read all the FAA ADs as soon as they are issued. You can do it for fun, or like me, do it for a living. AND Yes SchmiteGoBust, I've even been known to go down the line at midnight on Xmas day just to help out. Its such fun that I can't keep away! :)

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Through difficulties to the cinema

[lame]

Blacksheep,

Already been there, that is where I got the info, just curious what this other site was?

Best regards,

"lame"


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"I USED to be a PPRuNaholic, but now I'm CURED"

[CaptainSandL]

Dragonspet

Not sure that you have got that the right way around. The wing tank pumps would have been on, because there was fuel in them, but the centre tank pumps should have been off because that was empty. The explosion was in the centre tank, which was “empty” (ie residual fuel only) and the centre tank pumps were on.

In a nutshell, the AD is saying don’t run the centre tanks pumps dry. Most qualified personnel wouldn’t let it happen, but obviously as it has happened at least twice. Boeing has felt the need to bring out an AD on the subject, if only to serve as a reminder about good operating practices and I suppose for product liability reasons.

S & L

PS I couldn’t get your link to work either.

[lame]

For info...... CASA Australia have just finally also issued an emergency AD covering this.



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"I USED to be a PPRuNaholic, but now I'm CURED"

[aeroguru]

You would think they would put a level switch to cut out/prevent the pumps from running below a certain level, then no flight deck action would be required.Someone please tell me that is how it is on the NG -600/700/800(900?).

[lame]

The AD applies to all models of 737, so I "assume" they are all the same, never seen a NG.

The problem with a level switch is that in flight the crew want to be able to use that fuel, they still can now of course but MUST turn off the pumps as soon as the low pressure light comes on. Any switch could go through the air/ground sense? but a bit messy, what if that played up, could have a really dangerous situation where on a long flight, this switch system went U/S and crew could not use all that fuel in the centre?


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"I USED to be a PPRuNaholic, but now I'm CURED"

[Dragonspet]

Hello Captain,
My apologies for the site disconnect, in speaking with our IS people I was informed of certain export regulations being imposed restricting Boeing data from overseas internet connections, apparently some third word country was using DPS information to manufacture gun parts, we can't be responsible for everyone.After all I do work on a US Airforce aircraft KC-10. It is a useful research site with information on issues prior to the escalation to the FAA level.Heads up info for Boeing Quality personnel, statistical data, corrective action that sort of bathroom reading material.The information was in Acrobat Reader 4.0 format if you don't have that program you can download it of the internet as well.
You are correct with the center pumps not required to be, on but the report stated the APU had been running for 30-40 minutes.In an effort to make sense of it all, I was considering that the APU may have been being fed from the center tank or maybe a rag or some debris was creating a blockage of the fuel manifold starving the pump of fuel.You would be surprised at what FOD has been found inside of fuel tanks.It is not uncommom to transfer fuel from tank to during refueling to save time and perform a SPR or training.
As I stated purely speculation, but isn't it all unless you were there first hand.
What error fault message did you recieve when attempting to open the site?
Good call "aeroguru" on the cutoff switch, should try to implement an STC could be worth some profit not to mention save some lives if this continues to occur.
On the up side the 737 is a very reliable aircraft and I am certian that this will be contributed to operator error and not a design flaw.
I really like your site here and try to view it every day at least once, while we have cultural differences I can relate to many of your concerns/complaints, this industry is a b-tch somedays and other days you love it to death. We all must have a bit of insanity to endure the years.
I hope you all have a great day.

[This message has been edited by Dragonspet (edited 04 May 2001).]

[This message has been edited by Dragonspet (edited 04 May 2001).]

[This message has been edited by Dragonspet (edited 04 May 2001).]

[This message has been edited by Dragonspet (edited 04 May 2001).]

[avmech]

I believe that its the A/C packs that are not to be operated on an extended basis in hot climates.

[morroccomole]

Regarding the NG fuel pumps; there is no auto cut off for the centre tank pumos, they must be switched off manually.