Boeing 777 - LHR short landing.

[empip]

A further report - no cause found yet... here

 

[megawatt]

The high pressure (HP) fuel pumps from both engines have unusual and fresh cavitation damage to the outlet ports consistent with operation at low inlet pressure. The evidence to date indicates that both engines had low fuel pressure at the inlet to the HP pump. Restrictions in the fuel system between the aircraft fuel tanks and each of the engine HP pumps, resulting in reduced fuel flows, is suspected.

My God, they're really desperate now

 

[blondini]

An interesting read.

 

[JohnD]

they're always really, really reluctant to admit it was caused by a fault in the aircraft.

 

[megawatt]

My original thought was fuel contamination by water + freezing = HP pump starvation and then subsequent cavitation.

Trouble with this theory is that it is easily proved/disproved and, if this had been the cause, we would have known by now.

A more insidious cause of cavitation could be LP booster pump issues, probably more with the computer technology which is used nowadays to keep the pressures up at the inlet to the HP EDP's rather than the pumps themselves as this would be common to all pumps and therefore a possible single point of failure.

Problem with this theory is that there would still be a sufficient head of pressure at the inlet to the EDP's without any booster pumps running at low altitudes, low to mid thrust settings (as you'd expect during the approach) and with anything but vapour in the tanks.

You can certainly rule out aircrew error as they'd be hanging by now

It's a mystery ... The game is afoot Holmes

MW

 

[empip]

The Boeing experiments will be interesting, unlike the engine makers they have not completed their rig tests yet.

....The primary challenge at Boeing is to create
the environmental conditions experienced on the flight
over Siberia, at altitudes up to 40,000 ft, in which to test
a representation of the aircraft fuel system. These tests
are collectively aimed at understanding and, if possible,
replicating the fuel system performance experienced on
the day and the potential for formation of restrictions...

--

 

[^woody^]

I thought that they were just going to swap the "More thrust" and "Less thrust" lables around?

They were also gong to change the landing lights

 

[megawatt]

I like the lights idea

 

[Gavin10]

Thank's woody,
you haved cheered me up 100% after the day ive had.
gavin

 

[Agile]

I was interested in this accident from the outset when, within 24 hours, it became clear that they did not suspect any serious design problem with the plane because they did not take the usual precaution of grounding the fleet.

My intitial thought was that it may well have been a crew operational error and I wondered if they had allowed the engines speed to reduce to far to enable them to spool up fast enough when power was required to maintain the glide path.

Unfortunately, that further interim report lacks enough technical depth to enable me to come to any conclusion or even make any guesses.

It seems to imply that the plane was in full ILS mode and the crew were leaving the systems to themselves perhaps without watching the performance as closely as I would have expected them to.

I presume the HP pumps are fed by LP pumps although no mention was made of them in that report. What evidence does cavitation leave in the outlet ports?

Tony

 

[Ricky2]

I was interested in this accident from the outset when, within 24 hours, it became clear that they did not suspect any serious design problem with the plane because they did not take the usual precaution of grounding the fleet.

Reminds me of the old joke years ago when all DC10s were grounded on safety fears

Rumour had it that Air Lingus didn't have any DC10s so they grounded 2 DC3s and a DC4

 

[empip]

There has been the odd problem with the 777... unthrustworthy sounds ominous.

http://www.iasa-intl.com/folders/belfast/BA777_Unthrustworthy.htm

In ref to an old 777 fault plus ref to others

...Some would be surprised that the FAA should allow an ETOPS aircraft with a defect that reduces engine power by up to 77 percent on takeoff to be considered serviceable. In theory, an engine with FADEC version A.0.4.5 installed has a defect that can't be cleared and is therefore unserviceable. Others might wonder how such safety critical software can make it through the validation and verification regime into world-wide fleet service. Overall, it's shades of the previous GE90 "rollback" and IFSDs (inflight shutdowns) from earlier days. The only difference was in those cases, it was in cruise and was caused by moisture freezing in the P3B and PS3 lines to the FADEC, and it was resolved by increasing the tubing diameters. Perhaps the software now needs uppercase zeroes and ones in its coding -- or a larger pitch font...

No fatal accidents thus far for 777 - but overall the USA is catching up -

...As hundreds of thousands of air travelers learned last week, the number of fatal accidents is not the only measure of air safety. Last week, American Airlines alone canceled nearly 3,100 flights affecting 250,000 passengers as the Federal Aviation Administration forced it to inspect wiring in its Boeing MD-80 jets. Alaska Airlines, Midwest Airlines and Delta also canceled flights for similar inspections.

The FAA was finally insisting on compliance with a September 5, 2006, order that it had given airlines 18 months to obey. The tougher FAA stance followed the revelation last month that the agency's lax enforcement of its own safety rules had allowed Southwest Airlines to fly dozens of its Boeing 737s without inspecting them as required for cracks in the fuselage.

The FAA fined Southwest a record $10.2 million and ordered an audit of maintenance records at all domestic carriers to see whether its rules had been obeyed. United had to pull some of its Boeing 777s from service to test their cargo-fire suppression systems.

No one knew whether the audit might turn up other planes that would have to be pulled from service.

"The U.S. aviation industry has produced an admirable safety record in recent years," NTSB Chairman Mark Rosenker said. "However, we must not become complacent. We must continue to take the lessons learned from our investigations and use them to create even safer skies for all aircraft operators and their passengers."

The government figures showed that scheduled U.S. airlines flew 18.7 million hours in 2007 with 24 accidents but no deaths. There was one fatality among nonscheduled U.S. carriers: A mechanic was fatally injured while working on a Sky King Inc. Boeing 737 in Tunica, Mississippi, on July 10.

Commuter airlines had 3 accidents in 302,000 hours of flight but no fatalities.

On-demand carriers had 43 deaths in 62 accidents over 3.7 million flight hours.

General aviation saw its accident fatalities plummet from 703 in 2006 to 491 in 2007. But during 23.8 million hours of private flights in 2007, the number of accidents rose to 1,631 from 1,518 in 2006.

Foreign registered aircraft accounted for 11 accidents in the U.S. in 2007, with three deaths in a single accident. Unregistered aircraft had 14 accidents, which claimed 7 lives...

 

[Agile]

Thats very interesting!

Have you heard any suggestions on the cause of the Kenya Airlines new 737 which crashed during May 2007 in the Cameroons killing 114 people?

This link to their earlier crash into the sea is a well written and very informative and makes very interesting reading although it stops short of a single cause:-

http://findarticles.com/p/articles/mi_m0UBT/is_5_19/ai_n9495634/pg_1

Tony

 

[megawatt]

I was interested in this accident from the outset when, within 24 hours, it became clear that they did not suspect any serious design problem with the plane because they did not take the usual precaution of grounding the fleet.

This action is far from usual Tony and is only taken when there is significant indication it could affect other similar aircraft ... Too many £'s involved

My intitial thought was that it may well have been a crew operational error and I wondered if they had allowed the engines speed to reduce to far to enable them to spool up fast enough when power was required to maintain the glide path.

Extremely unlikely, modern jets do not follow a glide approach like light aircraft they approach under power to prevent spooling delays ... Besides, most turbofans nowadays aren't that unresponsive even from flight idle.

It seems to imply that the plane was in full ILS mode and the crew were leaving the systems to themselves perhaps without watching the performance as closely as I would have expected them to.

Again, not very likely ... Pilots may doze off across the Atlantic but the two phases of flight where they are always on the ball is Takeoff and Landing ... Takeoff in particular as it's by far the most dangerous phase of any flight.

I presume the HP pumps are fed by LP pumps although no mention was made of them in that report. What evidence does cavitation leave in the outlet ports?

You presume correctly in all aircraft I've ever come across though I've no specific knowledge about the 777. Cavitation usually damages either the pump inlet guide vanes, its impellor, the outlet guide vanes or any combination of the three.

My money's on the computer system ultimately but we may never find out for sure and, if someone know's what it is, it may have been included in a recent upgrade covertly anyway

MW

 

[blondini]

I think the extremely low temperatures encountered during the flight could become more significant.

The aircraft's flight plan required it to descend from 10,400m to 9,600m at the border between China and Mongolia because of 'Extreme Cold', but instead the crew accepted an ATC request to climb to 10,600m where the ambient temperature was approximately -65C, and they closely monitored the fuel temperature.

Furthermore there are reports of temperatures as low as -76C in the area between The Urals and Eastern Scandanavia.

Could the fuel temperature in some part of the fuel system have fallen below that indicated to the crew and eventually lead to a partial blockage?