BA B777 Incident @ Heathrow (merged)

[Kapitanleutnant]

PaSoundMan

If I'm not mistaken, the 777 has an automatic icing detection and activation system on it. Been a few years since I flew it at my airline as FO, but it was essentially a no brainer system and whenever the system detected icing, it atuomatically turned the anti ice system on for the engines. No real input needed by the flight crew. Can someone confirm?

Not to say that system was inoperative, though.

K

[Halfnut]

ankh,

With three recorders taking a constant pulse of this plane I would think the AAIB will be able to narrow down the cause of this accident real quick. The AAIB has already said they will be coming out with an initial report in thirty days so I’m confident a “fix” will be out well before the final report which can take as long as two years.

I fly a “Cable Car” plane so I try to stay out of these kinds of discussions but giving the excellent safety record of the triple seven (and all others), the length of service the triple seven has been operating i.e. how many approaches/landings it has done successfully, I don’t see this happening again.

The landing profile that is currently flown by all operators has been honed over many years by other accidents so to compensate because of this accident will only off set the curve somewhere else. I’ll stick to flying the plane the way we’re trained (for now).

[cwatters]

The spokesman (AAIB?) I saw on TV last night said the plane was at 600 foot when it dropped very slightly below glide slope (journalists - note he didn't say that in itself was abnormal) the auto throttle commanded more power as it is designed to do but engines didn't respond, (can't quite recall exact words but something like) pilot then switched to manual and advanced the throttle but the engines still did not respond. Presumably they continued to drop below glide slope (which obviously was abnormal!).

[Ex Cargo Clown]

Ok, I'll bite.

Some of the speculation on here is just insane. We've had ridiculous, unfounded suggestions, including and Electro-Magnetic "weapon" fired at the aircraft, lightning etc, I'm only suprised Aliens haven't had fingers pointed at them yet....

It also seems people are either completely oblivious, or just ignoring the facts.

As far as I know the facts are.

1) The engines did NOT "stop", they just ceased to produce commanded thrust.

2) The aircraft did NOT run out of fuel (see 1)

3) Wx was NOT an issue

As for those "barrack-room" pilots criticising the pilot for not been stabilised at 1500ft Ever heard of the 160 to 4 requirement at LHR ?

I'm not going to speculate anymore on this, applying Occams Razor to this is clearly a difficult exercise.

[Earl]

On the RR 524 I seem to remember a switch that could be placed in over ride that would reset the fuel control in sub idle conditions.
Did something to the fuel control amplifier.
Over speed protection was out the window then and had to be watched.

[Ian W]

Full Flap Selection

"It is unlikely that the pilot would lower the undercarriage at such a low altitude (approaching 400ft), unless he was already aware that he had to stretch the glide slope by keeping the aeroplane in a clean configuration, and there is no evidence of that (yet)."

It is more likely that full flap was selected at around 2 miles and as the drag increased there would/should be a demand for more thrust from the engines. If they then remained frozen at the previous percentage the perception would be loss of power.
Does anyone know: (1) the flap settings and speeds/altitudes in a B777 on finals? (2) if there is a possible common mode failure with FMC thrust demand control?

[Skydrol Leak]

I am not sure about that 600 feet on 2 mile final???????
That seems really low from the get go.No?

[Kapitanleutnant]

Skydrol...

That's the perfect 3 degree Glide Slope and is the standard around the world. There are some a bit more and some a bit less, but that 3 degree glide slope is standard.

3 Degrees at 2 miles (3x2 and add the zero's) is 600 ft!!

K

[Ex Cargo Clown]

Nope it is the correct altitude on a 3 degree slope.

Do the trig

2 miles is approx 10560 feet

10560 * tan 3 = 552 ft

Little bit more complicated than this, but that is the idea.

[sevenstrokeroll]

lost in saigon...

there is no indication published that the engines were at "approach setting" at six hundred feet.

pratt and whitney jt8d, cfm 56 among others, it is a company wide procedure.

try it, you'll like it.

[NSEU]

...and if we're talking two Nautical Miles along the surface of the earth (using tan as an operator), on a 3 degree glidepath, it puts the aircraft at about 637feet.

[HEATHROW DIRECTOR]

I was always taught 318 feet per mile on a 3 degree glidepath..

[NSEU]

Wouldn't need to as the RAT would deploy for the loss of either. I have on a few occasions, observed hydraulic pressure indication from a windmilling RB211

Engineers are warned that hydraulic pressure will move control surfaces even when dry spinning an engine using the starter motor.

A 747-400 pilot has even reported getting full electrics from a windmilling engine (but that was at cruise speeds). The crew of the BA 747 which flew through volcanic ash were also getting intermittent electrics (not just Battery/Standby power). You wouldn't be getting electrics from unpowered engines windmilling at 140kts, however (assuming the 777 was approaching at around this speed)....and you would be probably getting close to losing hydraulics for flight control. However, as repeated ad nauseum... no one is saying that the engines were windmilling.

[Ian W]

Precision on approach

"I was always taught 318 feet per mile on a 3 degree glidepath.."

If you are going to use that level of precision - then which part of the aircraft are you measuring from?

I always found that 300ft per mile was good enough for most purposes (and far easier to work with)

[GotTheTshirt]

The basic ( serious) speculation semms to point to both engines failing to respond to Autothrottle Command.
We have some technical input on the forum into the fact that both FADEC, are totally independant and with alternate sources.
The Autothrottle will vary power according to some input that is trying to maintain a specified flight path from some parameter(s). The power is constantly changing to maintain this flight path
2 questions.
1 Where is the source for the A/T and is it duplicated
2.If the A/T fails to command the crew will get a visual indication from F/D that all is not well. How long from when the A/T failed to repond and the aircraft deviates from the prescibed path would the crew realise?

[FullWings]

It was a moderately gusty day, by all reports, so as the A/P and A/T were both engaged (AAIB) the 777 would have been tracking the LOC & G/S with the engines spooling up during lulls and spooling down during gusts. Unfortunately it seems the engines "froze" at a point when they were producing less than the datum power needed to complete the approach safely in the configuration they were in (gear down, F25 or F30), leading to an inevitable undershoot.

Another factor is that as the wind backed off and reduced with decreasing height, it would lead to an effective loss of airspeed that would need to be countered by a period of above datum thrust to bring it back to near the approach reference speed. This effect is more noticeable between 1,000'AGL and the ground, e.g. at 600'.

[Max Tout]

As someone who is due to fly today on a B777 (not BA) I am interested in the following:
The fact that the crew have been publicly exposed to the media would indicate that there is no question of operator error as an immediate cause of this accident. This means that, presumably, a system failure is still a possibility. In this case I am wondering why B777s are still being permitted to fly whilst there is any doubt as to the actual cause.

[NSEU]

"The 2 FADECS for the engines are indeed independent but how about the autothrottle itself ? Is that perhaps a possible single point of failure ? Just asking."

The A/T really isn't an issue here. All the 777 Autothrottle does is physically move the thrust levers in the cockpit using little electric motors. The thrust levers then indepedently send electric (thrust lever angle position) signals directly to the EEC's (or "FADEC's" as you call them). As stated before, the pilots manually advanced the throttles with the same effect (none).

Hope this makes sense

[francophile69]

Apologies for yet another bonehead question from the SLF.
We are continually told to turn off mobile phones and laptops on landing as these can effect the aircraft systems. What systems are at risk? Presumably nothing that could have this consequence?

[OverRun]

The investigation is looking closely at the thronomister which failed when electrical power was lost, and excessive aft C of G due to waste tank overflowing on the long flight, leading to low speed handling problems and a stall.

Thronomister
The engine is managed by a dual channel FADEC system. The EEC is part of this system (the heart). The EEC controls engine systems, starts and autostarts, and T/R operation. Interruption of electrical power to either channel of the EEC causes a reset of the EEC. Interruption of power to the FADEC activates the EEC inhibit reset circuit and is intended to control spurious commands in the event of circuitry over-voltage such as lightening strikes. The fuel supply to this engine is from airplane fuel system through the engine fuel pump (two stage) to the carburettor. The pump supplies fuel to Fuel Metering Unit and servo fuel for actuators. Fuel flow transmitter and thermocouples supply fuel flow and temperature readings to cockpit via EEC. The power to the fuel pump circuit is via an independent bus. Loss of the thronomister due to electrical power loss causes the fuel pump to revert to one of four fixed settings. At low engine speed the fuel pump revert setting is idle. The electrical power loss affects many systems in the 777:

_115VAC STANDBY BUS-MAIN_
ADC LEFT POWER (34-12-01)
NAV RADIO RMI (Optional)
NAV RADIO MKR VOR LEFT (34-51-01)
NAV RADIO ADF RIGHT (can also be found on 115AC Bus #1 on some airlines)
NAV RADIO ATC LEFT (34-53-01) Optionally found on 115VAC Main Bus #3
STANDBY IGN ENG 1 (74-31-01)
STANDBY IGN ENG 2 (74-31-02)
STANDBY INSTR LIGHTS (33-11-04)
FLIGHT CONTROL ELEC 1L AC (Also known as FCE Power Supply or PSM. NAV RADIO MLS-L (Optional)
EFIS CONT LEFT (31-61-01)
UPPER EICAS (31-61-01)
THRONOMISTER FUEL ENG 1 (79-31-01)
THRONOMISTER FUEL ENG 2 (79-31-02)
EIU LEFT (31-61-01)
FLIGHT CONTROL ELEC 2L AC (Also known as FCE Power Supply or PSM. One of four. See Notes)
MAWEA POWER A (31-51-01) Modularized Avionics Warning Electronics Assembly power supply A.
FMCS CDU-LEFT (34-61-01)
MAIN AC STBY BUS VOLTAGE (24-34-02)
MMR LEFT (MULTI MODE RECEIVER) 34-31-01

_115VAC STANDBY BUS- APU_
PFD-LEFT
ND-LEFT
FMCS FMC-LEFT

_28VDC APU BATTERY BUS_ (Normally supplied with DC power from TRU #3 unless forced to use APU Battery Charger or APU Battery)
ENG START AIR CONT (Provides elec power to Start Switches and Pneumatic Start Valve solenoids. Valves are electrically controlled, but pneumatically driven... They won't open without bleed air). Power for light in Start Switches comes from the #1 DC Bus.
APU DC FUEL PUMP (Required if #2 AFT MAIN BOOST PUMP is not providing pressure. APU switch must be in ON or START and the following CB's must be set: APU PRIME CONTROL (or APU ALT CTRL) and APU START)
THRONOMISTER FIRE WARN HORN (Horn located in RH Body Gear Well)
NACELLE LE ANTI-ICE 1 (30-21-01) Also known as NAI. Provides power to VALVE solenoid). Auto Anti-Ice Systems appear to use Main Bus power however
NACELLE LE ANTI-ICE 2
LOOP A FIRE 1 OVERHEAT 2
LOOP A FIRE 2 OVERHEAT 1
LOOP B FIRE 1 OVERHEAT 2
LOOP B FIRE 2 OVERHEAT 1
FIRE DET APU LOOP A
FIRE DET APU LOOP B
ENG 1 SPEED SENSOR 1 (77-12-05) Provides power to engine #1 "N2 speed card" Channel 1. N2 > 50%, N2 > 52%, N2>83% data is used for airplane system logic.)
ENG 1 SPEED SENSOR 2 (As above, Channel 2))
ENG 2 SPEED SENSOR 1
ENG 2 SPEED SENSOR 2
EEC CH A RESET/INHIBIT 1 (73-21-15) EEC Hardware reset
EEC CH A RESET/INHIBIT 2

Excessive aft CofG

The original design of the 777 was for the A market: 7,200 to 9,630 km range. When the longer range versions were introduced, the potable water system and lavatory waste system capacities were increased by an additional 383 litres of potable water, and 513 litres of waste-tank capacity. The larger tanks are located in the rear cargo compartment area and have reduced the available rearmost cargo area to 9.77 m3. This is offset by increases in forward and aft cargo compartment capacity. The original tank was 33 metres aft of the nose. With the extended range 777, the new toilet tank is 55 metres aft of the nose. The effect of this larger tank and more rear location on the centre of gravity is significant.

On very long flights (such as China-London), as the toilet is used over time, the tank overfills and spills, and the CofG can go outside the aft limit. In cruise, operating near the aft CG limit, the download on the tail is minimized and angles of attack and drag are reduced which improves performance. However, moving the CG aft reduces the longitudinal static stability of the airplane. At low speeds, at the end of a very long flight when the waste tank is over full, waste has spilt into the rear cargo area, and the CofG is outside aft limits, the aircraft is difficult to control and is tail heavy; it is more likely to stall at very low speeds.

This had been a problem before, and the incident affecting Boeing 777-236, G-VIIC, in the cruise between Barbados and London. Approximately ten and a half hours into a scheduled flight from Barbados to London, a crew member noticed an unusual odour in the cabin. Two minutes later a toilet smoke warning sounded and smoke was seen emanating from beneath the door of toilet 'N'; located by the R4 door. Fire fighting equipment was gathered and the toilet door was partially opened revealing flames and smoke. A BCF fire extinguisher was discharged into the toilet compartment and the door closed. When the fire was confirmed as extinguished, the area was investigated. The source of the fire was found to be overflowing of the waste transfer pump due to the waste tank being too full and an electrical short circuit causing the fire.

Boeing have just issued a service letter 777-SL-38-009 which requires that for Boeing 777s after 8 hours flight duration, all the economy toilets except one for emergency use should be closed off to prevent overflowing until changes to the waste tankage system can be made.