Roost Air Lounge => Aviation related topics => Topic started by: Oddball on September 04, 2008, 04:24:16 PM
Title: BA B777 update
Post by: Oddball on September 04, 2008, 04:24:16 PM
Update from the AAIB about the BA B777 short landing at Heathrow:
Press Assoc. - 1 hour 20 minutes agoThe crash of a British Airways jet at Heathrow Airport this year was probably caused by ice restricting the flow of fuel to the engines, investigators said.
The Air Accidents Investigation Branch recommended that airlines introduce interim measures for all Boeing 777s to reduce the risk of this happening again.
One passenger suffered a broken leg and eight others received minor injuries when the BA aircraft from Beijing came down short of the runway on January 17.
The cockpit crew were unable to get the required thrust from the engines as the jet approached Heathrow and it landed on the grass just inside the airport's boundary fence.
Co-pilot John Coward, 41, took control for the landing and at a height of about 720ft the thrust of the right engine reduced. About seven seconds later, the thrust of the left engine reduced to a similar level.
The engines continued running but not with the amount of thrust demanded. By 200ft the airspeed had reduced to about 108 knots and the autopilot disconnected at 175ft.
The AAIB released its fifth report into the incident, focusing on the aircraft's fuel system. It concluded: "The investigation has shown that the fuel flow to both engines was restricted - most probably due to ice within the fuel feed system. This ice is likely to have formed from water that occurred naturally in the fuel whilst the aircraft operated for a long period, with low fuel flows, in an unusually cold environment."
Investigators said they had ruled out problems with fuel quality or quantity, the fuel freezing or incorrect procedures by the flight crew as causes of the crash. But they noted that they found distinctive and abnormal marks on the high-pressure fuel pumps from both engines of the BA 777. The experts concluded that these were formed by a phenomenon called "cavitation", which is caused by a restriction in the fuel flow to the pump.
Because there was no evidence of any mechanical obstructions, they concentrated on the possibility of ice building up elsewhere in the fuel system.
Aircraft are designed to cope with significant amounts of the ice crystals which form in fuel when they climb into sub-zero atmospheric conditions. But tests on a Rolls-Royce Trent 800 engine, like that in the BA jet, showed that restricting fuel flow to the high-pressure pump caused a similar effect to that recorded in the accident.
Title: Re: BA B777 update
Post by: Rooster Cruiser on September 05, 2008, 04:45:30 PM
So what is the solution? Add Prist to the fuel of all 777's??? ::thinking::
This is a strange situation. All transport category aircraft have fuel heaters of some sort that are supposed to melt any ice crystals before they reach the engine and cause fuel starvation. I know the Citations and PC12's have them, and even some piston engine airplanes like the Cessna 421 have fuel heaters. All large transport category aircraft have fuel tank heaters as well. Those are designed to keep the Jet fuel warm enough that it does not congeal when operating in -60C environment or colder.
I'll bet the engineers at Boeing are scratching their heads over this one. The 777 has been in service for several years now, and this is the first instance of this happening.
RC
Title: Re: BA B777 update
Post by: Oddball on September 06, 2008, 07:04:16 AM
i've heard about Boeing's oil cooled fuel heater's (or is it the other way round? ??? ) are they still in use?
Title: Re: BA B777 update
Post by: Rooster Cruiser on September 06, 2008, 03:51:04 PM
i've heard about Boeing's oil cooled fuel heater's (or is it the other way round? ??? ) are they still in use?
I believe it is called an oil-to-fuel heat exchanger. It is standard equipment on any engine that is used for high altitude flight.
Title: Re: BA B777 update
Post by: BrianGMFS on September 07, 2008, 11:26:18 PM
What I read was that there was so much water that the heat exchangers couldn't keep up with the ice at cruise power. (not enough heat) The recommendation now is to periodically increase power during cruise flight.
Brian
Title: Re: BA B777 update
Post by: Rooster Cruiser on September 07, 2008, 11:30:32 PM
If there was that much moisture, I'd suspect some fuel contamination. That just doesn't sound right.
Title: Re: BA B777 update
Post by: BrianGMFS on September 09, 2008, 10:17:28 PM
If there was that much moisture, I'd suspect some fuel contamination. That just doesn't sound right.
They got fuel in China..... I can tell you, No offense to my Canadian friends, the only time I ever found any water in the tanks of the planes where I used to work were after they had been to Canada or the King Airs had been refueled overwing in the rain.
CYUL (Montreal) was the worst. I got nearly a gallon of water out of one of the King Air's Fuel after a fuel stop in Montreal. That's pretty bad. The mechanics who do the overnight checks on the airliners at BTV regularly find several gallons of water in the tanks on the scarebusses and Jungle Jets. Most of which get their gas at JFK or ORD.
Brian
Title: Re: BA B777 update
Post by: Oddball on September 10, 2008, 12:16:53 AM
Now they are talking about putting additives into the fuel to stop it freezing ??? but correct me if im wrong but aint additives all ready added into kerosene to stop it freezing or are my college notes wrong?????? ::thinking::
Title: Re: BA B777 update
Post by: Chopper Doc on September 10, 2008, 05:17:35 AM
Jet fuels intended for high altitude use (ie: almost all the fuel you'll find at an airport) will have Fuel Stabilizing Ice-Inhibitor (FSII) added. This stuff will stop microbial growth and prevent the water that jet fuels naturally absorb when exposed to air from condensing into droplets. It does not remove the water, however, and once the FSII is saturated you can see it in the bottom of a barrel looking like watery apple jelly.
Normally, since the droplets can't form, they can't form ice crystals either. This is the real reason for putting FSII in the fuel anyways: no ice crystal formation, no fuel filter plugging resulting in in-flight engine shutdowns. For light, lower altitude aircraft the FSII just makes a simple problem into a big one: instead of checking your barrels before you pump or checking the bowser sumps and filters daily, you have to assume there is entrained water and try to find the apple jelly wherever it accumulated in your system. I find that it's easier to look for water carefully, drain your sumps, and pay attention to what you're burning rather than trust a chemical to do your job.
Just one more reason why I like the P&W PT6-T's in the 212: they'll burn anything from gasoline to stove oil, with or without entrained water and FSII (not a slug of water, mind you, 'cause water won't burn - even in a PT6).
Title: Re: BA B777 update
Post by: TheSoccerMom on September 10, 2008, 07:08:38 AM
That anti-coody and anti-ice crap does work, but it also can wreak havoc on seals inside the fuel tanks.... we reduced the intentional use of it dramatically, and the incidence of flapper valve failure dropped off steeply in coincidence. Skipping it works out fine -- it's not like we're flying any higher than the ridgelines to begin with.
Seems like everything has a trade-off.
8)
Title: Re: BA B777 update
Post by: Baradium on November 05, 2008, 05:08:15 AM
I've heard there is still another possibility or two for a cause, but they are severely downplaying them...
Title: Re: BA B777 update
Post by: Mike on November 05, 2008, 10:48:07 PM
I've heard there is still another possibility or two for a cause, but they are severely downplaying them...
and they are?
The radio jamming equipment that travels with blair to make sure any remotely detonated bombs and other ordnance would be inneffective is powerful enough that it may have caused the FCUs to lock up.
Otherwise, intereference malfunctions from other sources.
From what I understand, they haven't ruled those out yet.
Title: Re: BA B777 update
Post by: leiafee on November 08, 2008, 12:47:59 PM
The radio jamming equipment that travels with blair to make sure any remotely detonated bombs and other ordnance would be inneffective is powerful enough that it may have caused the FCUs to lock up.
Otherwise, intereference malfunctions from other sources.
From what I understand, they haven't ruled those out yet.
The interim report from the AAIB (http://www.aaib.dft.gov.uk/sites/aaib/publications/interim_reports/boeing_777_236er__g_ymmm.cfm) I read, suggested they had
Quote
Tests were conducted on the effects of HIRF and EMI on the spar valve control system up to power levels well in excess of published standards and no anomalous behaviour was experienced. In addition, the EECs were originally tested satisfactorily to power levels in excess of those that would have affected other more sensitive aircraft systems. During the accident light no anomalies were evident with the electrical, navigation or communication systems, which are much more susceptible to such interference. There is therefore no evidence to suggest that HIRF or EMI played any part in this accident.
Much as the irony might be amusing, I suspect that theory is a non-starter.
Title: Re: BA B777 update
Post by: Rooster Cruiser on November 09, 2008, 01:40:08 PM
Quote
Much as the irony might be amusing, I suspect that theory is a non-starter.
Aw heck, Leia! Never let the facts get in the way of a good conspiracy theory! ::banghead::
Title: Re: BA B777 update
Post by: Oddball on November 09, 2008, 02:09:23 PM
I blame the visitors from outer space myslef. if you cant find out what happened they are always behind it ::whistle:: ::whistle::
Title: Re: BA B777 update
Post by: leiafee on November 09, 2008, 04:25:15 PM
Much as the irony might be amusing, I suspect that theory is a non-starter.
Aw heck, Leia! Never let the facts get in the way of a good conspiracy theory! ::banghead::
Point! ;)
Title: Re: BA B777 update
Post by: Chopper Doc on December 26, 2008, 03:38:03 PM
With regard to radio-magnetic interference, there are plenty of instances where poor shielding, ground loops, or other wiring ghosts can allow spurious signals to effect electronics. Once installed in your aircraft, a ghost can become the defining factor in an aircraft's performance - or, as in this case, lack of performance.
Many years ago a Canadian Air Force C-130 Herc had such a ghost: if, when configured for landing, one specific radio was used (for instance, to call short) the aircraft would yaw dramatically - a rather unnerving evolution to manage while crossing the fence. It turned out to be RMI related to an interaction between the antenna lead and a yaw damper, IIRC.
Anyway, radio frequency ghosts are a potential hazard and may explain our 777 loss of power.
Title: Re: BA B777 update
Post by: Frank N. O. on January 06, 2009, 02:10:45 PM
So does that also mean that there's still a reason not to use electronic devices while onboard a plane? What about a laptop computer when on a overseas flight?
Frank
Title: Re: BA B777 update
Post by: Chopper Doc on January 07, 2009, 02:09:45 AM
Most consumer electronics are shielded well enough not to cause interference with other consumer electronics.
Which brings us to the consumer electronics made to radiate: cell phones, Bluetooth enabled devices, WAN enabled phones, computers or PDAs, etc. All are made to radiate RF energy and they do have the potential to add ghosts. That's the reason the cabin crew tell us to ask them before turning on any electronics. It's also why they insist that all gear is turned off for the critical flight phases at launch and landing.
Otherwise, a very small likelihood that your iPod will crash the jet.
Title: Re: BA B777 update
Post by: Frank N. O. on January 27, 2009, 05:20:53 AM
Thank you for the reply. I'd be happy with just a normal laptop computer without wireless anything, or a webcam for that matter, I won't need those at all.
