Forum: Civil and General Aviation

I find it hard to fathom that with all that metal, wiring, ground loops, and other electrically related items crammed in there that a cell signal of only a couple of watts is enough to effect the jet the way they suggest. If these components are so prone to RF noise, why not find a way to shield 'em? Find the bandwidth of the RF you're concerned with and build an enclosure to protect the thing.

Anyone here remember "Tempest" from way back in the day? Same kinda shielding would work...just gotta figure out what bandwidth to block.

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Here is the latest update

http://www.aaib.gov.uk/latest_news/acci ... update.cfm

Accident to a Boeing 777-236, G-YMMM, on 17 January 2008 - Initial Report Update

Accident to a Boeing 777-236, G-YMMM, on 17 January 2008 at 1243 hrs
Initial Report Update 23 January 2008

Since the issue of the Air Accidents Investigation Branch (AAIB) 1st Preliminary Report on Friday 18 January 2008 at 1700 hrs, work has continued on all fronts to identify why neither engine responded to throttle lever inputs during the final approach. The 150 tonne aircraft was moved from the threshold of Runway 27L to an airport apron on Sunday evening, allowing the airport to return to normal operations.

The AAIB, sensitive to the needs of the industry including Boeing, Rolls Royce, British Airways and other Boeing 777 operators and crews, is issuing this update to provide such further factual information as is now available.

As previously reported, whilst the aircraft was stabilised on an ILS approach with the autopilot engaged, the autothrust system commanded an increase in thrust from both engines. The engines both initially responded but after about 3 seconds the thrust of the right engine reduced. Some eight seconds later the thrust reduced on the left engine to a similar level. The engines did not shut down and both engines continued to produce thrust at an engine speed above flight idle, but less than the commanded thrust.

Recorded data indicates that an adequate fuel quantity was on board the aircraft and that the autothrottle and engine control commands were performing as expected prior to, and after, the reduction in thrust.

All possible scenarios that could explain the thrust reduction and continued lack of response of the engines to throttle lever inputs are being examined, in close cooperation with Boeing, Rolls Royce and British Airways. This work includes a detailed analysis and examination of the complete fuel flow path from the aircraft tanks to the engine fuel nozzles.

Further factual information will be released as and when available.

asiatrails, thank you for the reports. Respect to the crew getting their passengers and themselves down safely.
The folks at farnborough will nail this one. I can imagine the RR, Boeing and BA staff crossing their fingers on this one too, for obvious reasons....It is a real mystery isn`t it?
Engine FADEC? Not likely, not both of them. Fuel pumps? I don`t know how it works but the aircraft flew from China, so it wouldn`t have a full fuel load. Would fuel be drawn from one tank or would the fuel load be evenly distributed between the various tanks to keep CoG under control, the engines drawing fuel from different cells?

I hate pre-empting inquiries, really, but it is a good topic for discussion.

On the so called wi-fi, radio signal idea, there are good reasons why personal radio equipment isn`t used during take off and landing. It isn`t the power output of these devices at issue, it is the signals themselves.

Forum Veteran Joined: Dec 15, 2006 - 12:28 AM Posts: 760

LinkF16SimDude wrote:

I find it hard to fathom that with all that metal, wiring, ground loops, and other electrically related items crammed in there that a cell signal of only a couple of watts is enough to effect the jet the way they suggest. If these components are so prone to RF noise, why not find a way to shield 'em? Find the bandwidth of the RF you're concerned with and build an enclosure to protect the thing.

Anyone here remember "Tempest" from way back in the day? Same kinda shielding would work...just gotta figure out what bandwidth to block.

The problems is that there are miles of wiring, and many sensitive components. Also another thing that you have to consider is the proximity of a cell phone. Another thing to consider is that the aircraft itself holds in RF, so if there is a transmitter inside of the fuselage the RF will be concentrated inside of the aircraft. (it's much like yelling in a cave will typically sound louder than yelling in an open field) Another thing to consider is that sometimes the body structure can act like a parabolic reflector and can concentrate RF depending on the location of the cell phone and the vulnerable component.

With the miles of wiring, all it takes is one bad connection or damaged wire to compromise the shielding. All it takes is one bad connector or a solder blob or frayed wire to act like an RF antenna that can haul in unwanted frequencies.

Here's the latest official update, it's looking more and more like ice in the fuel.

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American Airlines incident from Flight Global

http://www.flightglobal.com/articles/20 ... ottle.html

American investigates as 777 engine fails to respond to throttle
By David Kaminski-Morrow

American Airlines is investigating an incident yesterday during which the engine on one of its Boeing 777-200ERs apparently failed to respond to throttle commands for several seconds during approach to Los Angeles.

The incident involved American’s flight AA299 from Miami and occurred at a height of around 2,000ft as the aircraft was descending to Los Angeles.

In an information statement to members, the Allied Pilots Association – which represents American Airlines cockpit crew – says the aircraft experienced a “hang-up” of its left-hand engine.

“The auto-throttles were on and the left engine hung at approach idle as the right engine accelerated normally,” says the association.

“It is believed that the left engine would not respond to throttle inputs for 10-15 seconds before finally responding and accelerating to the commanded thrust.”

All of American’s 777-200ERs are fitted with Rolls-Royce Trent 800 powerplants.

Maintenance personnel have downloaded the flight-data recorder information and will examine the fuel tanks and engine fuel filters for possible contamination. Tests will also be carried out on the electronic engine control.

Neither the US FAA nor the US National Transportation Safety Board has given any further information on the incident. The pilots’ association has not identified the specific aircraft involved. American Airlines could not immediately be reached to confirm the incident.

Investigators in the UK are still trying to determine the reasons why both Trent 800 engines on a British Airways 777-200ER failed to respond to throttle-increase commands during final approach to London Heathrow on 17 January, resulting in the aircraft crashing short of the runway.

Elite 1K Joined: May 26, 2005 - 08:39 PM Posts: 1496

That is spooky. Once is a fluke, twice is not. Let's hope it doesn't drag out for years like the 737 rudder issues did.

Forum Veteran Joined: Dec 15, 2006 - 12:28 AM Posts: 760

As I said on the UK mishap, I think it is a electromechanical or software problem I doubt the icing or fuel contamination angles.

I am a little skeptical of RF interference, but feel it should not be ruled out unless and hard cause can be found that rules it out.

Guysmiley wrote:

That is spooky. Once is a fluke, twice is not. Let's hope it doesn't drag out for years like the 737 rudder issues did.

Air France just had three significant incidents with the 777/GE90 aircraft in the last month. In the B.A. incident, I think the new approach profile they were using may be a factor.

Here is update #3, looks like some type of transient fuel restriction resulting in engine fuel pump cavitation.

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Here is the latest update, ice in the fuel caused the loss of power. No stray electrons, or outside influences.

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Forum: Civil and General Aviation

British Airways Boeing 777 Heavy Landing