Emergency check on Boeing Fuel Pumps

[Feline]

From BBC:

The American Federal Aviation Authority has ordered US airlines to inspect more than 1,400 Boeing jets to see if they have a potentially faulty fuel pump which could lead to an exploding fuel tank.
The FAA say the pumps could have a problem with wires that were placed too close to a rotor and can chafe - although there have been no serious incidents yet.

The pumps were installed in January and April by a California company on Boeing 737s, 747s and 757s.

The airlines were given four days to inspect their fleets.

[SaturnV]

Additional details. Keep enough fuel in the center tank to keep the pumps covered.

WASHINGTON (AP) - The Federal Aviation Administration issued an emergency order Friday compelling U.S. airlines to inspect 1,440 Boeing jets to see if they have a fuel pump with potentially faulty wiring that could lead to an explosion.

The FAA stressed that no serious incidents have been linked to problems with the pumps, which are made by Hydro-Aire Inc. of Burbank, Calif., and were installed in January and April on Boeing 737s, 747s and 757s.

The airlines were given four days to inspect their fleets. The FAA estimated 1,250 pumps could have a problem with wires that were placed too close to a rotor and can chafe.

Ron Wojnar, the FAA's deputy director of aircraft certification services, said any airlines with the pumps are being ordered to keep enough fuel in the tanks to cover the devices even when the planes bank or encounter turbulence in flight.

Wojnar said the submersion would prevent any sparks from igniting fuel vapors. "This is not an unsafe condition,'' he said.

The order affects 515 of the 737s, 247 of the 747s, and 678 of the 757s operated by U.S. carriers.

Foreign airlines operate about 2,100 of the Boeing jets. The FAA is sending advisories about the pumps to its counterpart agencies in those countries.

The FAA will issue a follow-up directive in a few weeks, instructing carriers to repair or replace any faulty pumps, Wojnar said.

The pumps are located in the center fuel tank under the fuselage. Some planes may also have pumps in wing tanks.

Boeing spokeswoman Liz Veridier said her company sent the airlines a bulletin Wednesday ordering the pumps to be
replaced on 116 new planes that had been put into use this year.

Other 737s, 747s and 757s were ordered to fly only with their tanks full enough to cover the pumps until further inspections could be carried out, she said.

The problem was detected on three planes that had pumps short out and stop working, giving the crew an indication of low pressure in the tank, said FAA spokesman Les Dorr.

The British carrier easyJet sent the pump back to Hydro-Aire on Aug. 12 after the crew of one of its Boeing 737s detected low pressure, Dorr said. A week later, a Northwest Airlines 747-400 reported a low pressure indication and found the same problem, he said. A China Southern Airlines 747-400 experienced the same trouble.

[Jackonicko]

OK, now will someone remind me as to why this wasn't the likeliest cause of TWA 800? :D

[lomapaseo]

>OK, now will someone remind me as to why this wasn't the likeliest cause of TWA 800?
<

A few reasons

1) All pumps were found and examined except one.

2) The mounting positions of the pumps showed no signs of deflagration (fire)

3) The source of the fire was shown to be internal and away from the pump locatiions.

4) There was not a similar known batch problem with the pumps as identified in todays problems

5) JBS says it can't be the tank it must be a door and he's an expert isn't he?

[Lu Zuckerman]

The FAA allows the certification of an aircraft, an aircraft system or an appliance used in the system by either testing it under operating conditions or by computer analysis. The problem identified comes under the heading of batch sensitivity where if one item in a series of items suffers from a quality or design problem it can be inferred that many if not all elements of that design have the same problem. The problem identified by the FAA indicates that the pumps were inadequately tested and that batch sensitivity seems to be present.

My question is why this problem was not identified in the Failure Mode Effects Criticality Analysis (FMECA) and a further expansion of this question is was an FMECA actually performed for the pump. If the original FMECA was properly performed the problem would have been identified and when Boeing fed that FMECA into their FMECA a safety hazard would have been identified and the pump design changed.

Many companies do not wish to identify potential problems and they hope that the airframe manufacturer will identify it. That way the Airframe Company will direct the supplier to make the necessary change and a scope change to the contract will be issued and the supplier will be paid for it.

Before I get sacked for the above I will state that this is my personal opinion.

:cool:

[HotDog]

JBS says it can't be the tank it must be a door and he's an expert isn't he?

That "expert" is now asking for help to identify the aft cargo door of CA611 which is firmly latched to part of the cargo floor which got ripped out together with the door as the fuselage broke up.:rolleyes:

[moggie]

Lets not forget the Thai 737 that blew up on the apron - fuel pumps there, too.

Still, if Boeing and the FAA say it's no danger...........................! After all, there is no problem with rudder PFCUs either!

[cargo boy]

When I was flying the B767 there was a directive that the centre tank fuel pumps should be turned off when the fuel quantity in those tanks reached 500kg. As far as I remember this was due to a possible problem with the pumps overheating if they were not completely covered by fuel. Unfortunately it was not always possible to get to the switches before the low pressure light came on and reminded you that you had forgotten to turn them off. As far as I am aware there were no plans to 'fix' the problem by having some sort of alert when the fuel reached the 500kg level. If you had to use your 'kitchen timer' for other things on an ETOPS flight such as setting a reminder to get the alternate weather on HF or plot your 10 minutes past waypoint check then it was very easy to forget to turn them off before they ran out of cooling fuel.

[Agaricus bisporus]

"Ron Wojnar, the FAA's deputy director of aircraft certification services, said any airlines with the pumps are being ordered to keep enough fuel in the tanks to cover the devices even when the planes bank or encounter turbulence in flight.

Well just how much fuel is that, Mr Wojnar?

Mr Boeing says, " Main tanks must be full if center tank contains more than 1000lb/453Kgs"

Does Mr Wojnar state that less than 1000lb in the centre tank is sufficient to keep the pumps submerged in all aircraft attitudes, including turbulence?

In todays litiginous world I'd have thought he was sticking his neck out to suggest that without a lengthy research exercise, and to suggest we might fly around with more than that in the ctr is exceeding a manufacturers limitation.

Not very clear, is it?

[daywalker]

To add to the above:


LOW-COST AIRLINE REPLACES FUEL PUMPS AFTER SAFETY ALERT
EasyJet is replacing fuel pumps in five of its Boeing 737 aircraft following a safety alert. The Federal Aviation Administration in the US is warning all operators of 737, 747 and 757 planes around the world amid fears that a type of pump could be faulty. Experts fear that wiring on pumps placed too near a rotor could chafe, producing sparks and igniting fumes from highly flammable aircraft fuel. The devices, which are located in the central fuel tank under the fuselage and also in wing tanks, were installed in January and April. A spokesman for Boeing in the UK says that a total of 118 aircraft worldwide have been identified as having the pumps installed: 93 are 737s, 17 747s and eight 757s. It was not known how many, if any, are used by UK airlines. No serious incidents have been reported yet but easyJet was one of three carriers to raise the alarm after a pilot complained of low pressure in a tank of one of its 18 737-700s. A statement from the Luton Airport-based company said: "easyJet returned a fuel pump from a Boeing 737-700 to the pump manufacturer in early August when it became unserviceable. The airline has yet to receive confirmation as to the cause of the problem. "Safety is the first priority at easyJet. As a result, a flight crew notice has been issued and the airline will be adhering to the terms of the FAA's directive and maintain minimum fuel levels in the centre fuel tanks to ensure that the fuel pump inlets remain immersed in fuel under all operating conditions." A bmi British Midland spokeswoman said: "It hasn't affected our fleet at all. No-one need be concerned." Charter airlines Britannia and Monarch said they too had checked their aircraft but were not affected.

Copyright msn.co.uk

[Lu Zuckerman]

Once again the certification authorities and the airframe manufacturer have placed the responsibility of safety on the pilots instead of correcting the problem with the installation of pumps that are changed in design to prevent the chafing of wires on the pump rotating parts. In addition according to several posts above the certification authority has suggested to the operators to maintain a level of fuel that would keep the pumps covered under all maneuvering conditions without stating the required fuel level for the center tanks of the respective aircraft effected.

Here is a system that was designed in the 1950s that catered to a similar but opposite situation. The forward tank on the S-58 was the primary feed tank for the engine with fuel being transferred to the forward tank from the other tanks. If the fuel transfer filled the tank and the pump was not shut off by the pilot the fuel would rise in a pipe outside of the helicopter until it hit a thermistor switch which would shut down the transfer pump.

Another means of taking the responsibility away from the pilot is to equip the fuel monitoring system with a sensor that would turn off the pump when the fuel level reached a predetermined level or at least provide a warning initiated by a preset in the fuel monitoring system.

All of the above IMHO.

[atakacs]

Experts fear that wiring on pumps placed too near a rotor could chafe, producing sparks and igniting fumes from highly flammable aircraft fuel Well, last time I read the TWA800 report I thought the aircrat fuel was actually quite hard to ignitie...

[Pilot Pete]

The fuel is, the vapour isn't with the right combination of oxygen present.

PP

[I. M. Esperto]

At the time of TWA 800. 1,108 B-747's had been built, and none ever blew.

If the FAA actually believed the NTSB report, they would have had to ground all B-747's.

[GotTheTshirt]

Below is an FAA issued 1999 against L1011 aircraft. ;)

Some of the wording may seem familiar !!
The last Para fits modified pumps.

AD 99-24-12

To prevent a potential fire or explosion in the wing fuel tank, accomplish the following:

RESTATEMENT OF REQUIREMENTS OF AD 98-08-09, Amendment 39-10492
AFM Revision
(a) Within 50 flight hours or 10 days after April 28, 1998 (the effective date of AD 98-08-09, amendment 39-10492), whichever occurs first, revise the Limitations and Procedures Sections of the FAA-approved Airplane Flight Manual (AFM) to include the following information. This may be accomplished by inserting a copy of this AD into the AFM.

Add to Limitations Section:

FUEL SYSTEM
Fuel Pumps
Do not operate the fuel boost pumps of the affected wing tank in the air or on the ground when fuel quantities are less than the following:

Wing tanks 1 and 3: Less than 1,200 lbs. (545 kg) in each tank.

Wing tanks 2L and 2R: Less than 1,200 lbs. (545 kg) total in the two compartments (inboard and outboard) of each tank.

These quantities should be considered unusable fuel for the purposes of fuel management.


Placard Installation
(b) Within 50 flight hours or 10 days after April 28, 1998, whichever occurs first, install a placard on the engineer's fuel panel that states:

"If FQIS is operative, do not operate the fuel boost pumps when less than 1,200 pounds of fuel are in the corresponding wing tanks."

NEW REQUIREMENTS OF THIS AD
Modification
(c) Within 18 months after the effective date of this AD: Modify each fuel boost pump assembly in accordance with Parts 2.A. through 2.I. inclusive of the Accomplishment Instructions of Lockheed Service Bulletin 093-28-093, Revision 1, dated February 8, 1999. Accomplishment of this modification terminates the requirements of this AD. Following accomplishment of the modification, the AFM revision may be removed from the AFM, and the placard may be removed.

;)

[Flight Detent]

Hey Agaricus......,
Isn't that 10,000lbs or 4,530 kgs in the centre tank of the B747!!

just curious!!

Cheers

[Lu Zuckerman]

To: I M Esperto

Quote:

"At the time of TWA 800. 1,108 B-747's had been built, and none ever blew.

If the FAA actually believed the NTSB report, they would have had to ground all B-747's".


The FAA has overruled the NTSB on many of their recommendations. For instance when TWA 800 exploded the NTSB issued their findings and made the required recommendations to correct the problem. The FAA, which operates in support of the airline industry, will perform a cost benefit analysis. This analysis pits the cost to the airlines to make the necessary changes and factors in the downtime loss to the airline in revenue, the physical cost of making the change and any other factor that might impact the bottom line of the operators of the effected aircraft series.

These cost figures are compared to the cost in dollars to the airline to replace the downed aircraft, the payments to the survivors figuring 2.5 million dollars per person for a full load. The Department of Commerce derives this figure for a human life from calculations,which are updated on a yearly basis taking into consideration the cost of living, the present economy and other factors. The FAA will compare the two figures and their recommendations are based on the difference between making the change and not making the change. If it costs more to make the change Vs the cost of not making the change the FAA will recommend against making the change.

This fuel pump problem seems to support the findings of the NTSB at least in changing the pumps or the pump design but it falls short of the NTSB recommendation to change the wiring as the NTSB felt that the wiring not the pump caused TWA 800

:cool:

[Old Phart]

Much ado about nothing? Perhaps not, but its a lot of fuss about a routine safety precaution affecting roughly 180 of the world's several thousand Boeing airliners. The press had a field day, scaring an already jittery public witless by yammering on about exploding fuel tanks. The AD sold a lot of newspapers, as they so often do, but any resulting loss of public confidence threatens our jobs in aviation. We have a responsibility to reassure the public, not wind them up even more.

So, lets keep things in perspective; a problem has been identified and action put in place to prevent further hazard. Last Thursday Boeing advised all B737, B757 & B747 operators of the situation, giving advance notice of the impending Emergency AD and provided figures for minimum fuel quantities at both departure and arrival for all affected models, to assure safe operation. It appears that all parties behaved responsibly once it became apparent that a problem existed in at least one example of a redesigned fuel pump. We quite rightly expect no less, but can anyone demand more? Can a world without risk ever become reality?

The AD applies only to a recent (dash 4) model of Hydro-Aire's Fuel Pumps introduced on new build aeroplanes earlier this year. On other aeroplanes delivered prior to 2002, pumps may have been modified to dash 4 status and installed by Boeing Service Bulletins issued only in June. Given the time it takes to assess SBs, arrange roll-over modification programmes and route pumps through the shop, I doubt if many (or any!) pump retrofit modifications have been accomplished since June.

BTW, why were the pumps modified in the first place? To provide closing action for an AD issed previously in 1997 (arising from TWA800 no less) calling for repetitive inspections of fuel pumps...