BA B777 Incident @ Heathrow (merged)

[sevenstrokeroll]

Trent guys

can you tell us all what the minimum n1 for being "spooled up" is for this engine?

does BA have a minimum N1 setting at 500'? Or something similiar? We have different terminology perhaps, but you should be able to get my drift.

And will you tell us what the reports indicate the N1 was in the accident plane?

[Hand Solo]

It's slightly depressing that we've gone from the "Well they must have run out of fuel, I just knew it" to "Well they must have let the engines spool down too long to spool them up again, I just knew it".

At least the fuel theorists didn't have an AAIB announcement to work on. Know we've got official confirmation the engines didn't respond the idle spool theorists want us to to think thats fiction and it was all caused by a schoolboy handling error!

I don't know what the N1 is on this aircraft, it's a RR, the primary gauge is EPR. BA requires approach power to be set at 500 ft. Approach power varies according to weight and landing flap setting. I don't know what the N1 was when the think hit the deck but reports in a UK newspaper suggest the EPR gauges were both dead before the aircraft hit the fround.

[Intruder]

The AAIB have already said both engines failed to respond. That has come from hard data, not human perception.

We don't know that for a fact. That part of the report could well have come from the interviews with the Pilots.

[moggiee]

Originally Posted by interpreter

Why at 600 feet was there a need for additional thrust? If the aircraft was at that stage being flown manually (I believe it is normal to disconnect the autopilot at approximately 1000 feet) had the sink rate become excessive and a need for more thrust? ............

It is common practice at busy, large airports to maintain a high-ish approach speed on final approach, typically 160 to 170kt - until 4 nm from touchdown. The gear would normally be up and the flaps at one of the early to intermediate settings (sorry, I donīt know what settings the 777 would use but on the VC10 I flew in the RAF it would have been the first stage, called "take-off" by Vickers).

At 4nm, the gear would be lowered and the flaps extended to reduce to "normal" approach speeds (again, Iīm not familiar with the 777 but the VC10 would have been about 120-130kt).

There are a number of reasons for the high speed approach including: all aeroplanes flying similar speeds for easier ATC spacing and low drag configuration allowing lower power settings, lower fuel usage and less noise.

The downside is that the aeroplane is not placed into the landing configuration until late on the approach and as the drag increases (gear/flap extension) thrust has to be increased to compensate. Normally, everything should be settled by 500' above aerodrome level (aal) - unless, of course, the engines fail to spool up when requested - then it becomes "interesting"! If not stabilised by 500' aal, then the normal procedure would be to execute a go-around.

Hope that helps.

EDIT: Because my post seems to have upset M.Mouse so badly, may I reiterate that I am simply quoting an example of how an aeroplane with which I am familiar would fly "160kt to 4nm". Barring differences in terminology between manufacturers and differences in speed between types, the principle hold good.

I was trying to explain how an aeroplane could end up in a position whereby a power increase was needed late on in the approach and believe that the information posted above is relevant for explaining a PRINCIPLE. What I am NOT doing is passing comment upon this incident.

In addition, M.Mouse, whilst I donīt pretend to be familiar with the 777 I am reasonably familiar with BA shorthaul operations having spent 6 years teaching the self same BA SOPs to BA shorthaul cadet pilots.

Whilst the 777 may be different, last time I looked in BA FCOs, the SOP requires that if the approach is not stable by 800' aal then "consideration" should be given to the option of exectuting a go-around and Missed Approach Procedure and that if the aeroplane is not stable by 500' aal then the crew "must" go-around. Therefore, the required power increase may quite legitimately be made very late on in the approach - and whilst 600' is a bit on the late side, it's still (just) IAW SOP.

I'm quite happy to be corrected if wrong.

[pasoundman]

HarryMann
" Seeing as no one has attempted to answer my question as to exactly where along the runway the glideslope is targeted...

I'll ask it again, please....?"

The ILS aims the aircraft at the 'touchdown zone' marked with parallel white lines which are beyond the runway threshold that's marked with multiple white lines.
See them here.

http://maps.google.com/?ie=UTF8&ll=5...&t=h&z=16&om=0

Also see ....
http://www.pprune.org/forums/showthread.php?t=88920

[Hand Solo]

Intruder - No we do know it for a fact. The AAIB don't make statements that are not grounded in hard fact and the aircrafts Quick Access Recorder has already been analysed which will have all the data on thrust lever angle and engine response. If I balls up in BA I can go into the office and ask for replay of my flight. On the PC they will show me a full run down of the incident, with a visual flight sim style picture of the aircraft path along with full representation of the instruments, FMAs and control positions. That data was all available to the AAIB. Are you suggesting they ignored that and issued a statement based solely on crew reports that they might later have to retract? You really think they are that dumb?

Sevenstroke - C'mon, do you really think that level of detail is going to be in the public domain 2 days after the incident. What is it with you and Intruder's head in the sand attitude to a highly regarded accident investigation body? They've already said the engines (plural) failed to respond, you're still trying to nail it on the crew?

[787FOCAL]

It is common practice at busy, large airports to maintain a high-ish approach speed on final approach, typically 160 to 170kt - until at 4 nm from touchdown. The gear would normally be up and the flaps at one of the early to intermediate settings (sorry, I donīt know what settings the 777 has available but on the VC10 I flew in the RAF it would have been the first stage, called "take-off" by Vickers).

At 4nm, the gear would be lowered and the flaps extended to reduce to "normal" approach speeds (again, Iīm not familiar with the 777 but the VC10 would have been about 120-125kt).

There are a number of reasons for the high speed approach including: all aeroplanes flying similar speeds for easier ATC spacing and low drag configuration allowing lower power settings, lower fuel usage and less noise.

The downside is that the aeroplane is not placed into the landing configuration until late on the approach and as the drag increases (gear/flap extension) thrust has to be increased to compensate. Normally, everything should be settled by 500' above touchdown - unless, of course, the engines fail to spool up when requested - then it becomes "interesting"!

As for disengaging autopilot at 1000', that is certainly NOT the SOP. Minimum height for AP disengagement will depend upon the type of approach being flown, the approvals for the ground installations and runway, crew qualification, aeroplane avionics fit, crew qualifications etc. However, a category one approach can normally be flown on AP down to about 100' above the aerodrome in most autopilot equipped aeroplanes.

Hope that helps.

Regardless of how fast you are going in a VC-10 "less noise" should not be used in the same sentance.

[MR MACH]

Here is the Precision Approach Terrain Chart for LHR 27L:

http://www.caa.co.uk/docs/64/DAP_ACD...ow_Rwy_27L.pdf

Note: The elevation of the runway is 77 feet AMSL. Elevations in feet - All other dimensions in metres.

The ILS Glide Path is aligned to give a Threshold Crossing Height (TCH) of 56 feet.

From the chart you can interpolate where the aircraft should be at 600 feet on a 3 degree glide path.

[lomapaseo]

My take is that there are lots of good questions and good postulations among the clutter in this thread.

We still have too little confirmed data and as such lots of interpretation of what little data is available.

The good and the bad of it is that there has been no smoking gun of data prior to this event that gave us a clue that this was going to happen, Sure there have been incidents (things fail) but nothing that pointed at a likely event such as this. Independent failures of the certified systems between the aircraft and the engine are unheard of in this generation of design. So the first place I would look would be either a dependent failure or a latent failure in combination with another failure condition. The latency could take the form of a safe guard or layer of redundancy that was missing and/or not detected, The other parts of the chain could be simple gotchas for any reason including crew performance leading up to the initiation of the problem.

So we need to be open about the investigation in a technical sense whilst tolerant at the same time of the human element after the fact. (no blame)

I'm still struck by the differences in the visible dirt ingested between the two engines. The one engine with the dirt stuffed into the core compressor sure appears to have been at high power.

My question at this time (which I'm sure the investigators alread know) is whether the engine (s) did actually spool up belatedly. Putting this question to rest stiffles an awful lot of speculation on this board todate.

[NigelOnDraft]

Why at 600 feet was there a need for additional thrust? If the aircraft was at that stage being flown manually (I believe it is normal to disconnect the autopilot at approximately 1000 feet) had the sink rate become excessive and a need for more thrust? If so why? Sudden tailwind component or sharp drop in nosewind component?

Elementary meteorology my dear

Suggest one reads up on what the wind does as one gets closer to the surface, particularly with a HW from the L in the N hemisphere

NoD

[Contacttower]

Just to add 'fuel to the fire' with an out of context quote: (taken from a discussion about the 777's landing speeds and liaising with ATC)


As a 777-200 operator I can't see why the 300 would be better served by 170 kts to 4d - isn't the landing flap limit speed still 170 kts like previous variants - in which case isn't it a problem to slow down inside 4 miles?

As for the 200, Just to let you know that 170 to 4dme would be quite a problem for some of us who are required to have landing flap set by 900ft or the SESMA goes off = because the speed bleeds off sooooooo slowly from 160/170 (the '200 30 flap limit speed) to the final approach speed (about 135) , and this means that we end up being below 1000RA with the landing flap still running out and the power off - not good...office job <G>.

(between u, me and the gatepost we already have to cheat a little - depending on hwc we normally start the reduction to final at 5 miles - and it will take some 15 seconds before anything significant happens on the speed (= about a mile) so you wouldn't even notice it on the radar - I hope!)

Maybe approach power wasn't set? Maybe they had been kept fast and consequently the throttles did get stuck at a much lower setting than they otherwise would have been?

[Feathers McGraw]

Hand Solo

If the EPR gauges were dead, does that mean that EPR data wasn't available to the EECs on the engines? Might lack of EPR data to the EEC be what caused the engines to not respond to thrust lever inputs?

I have to say I would expect there to be more than one EPR measuring "channel" for each engine, is that the case on a Trent 800?

[30mRad]

Sorry to be a military pilot bore, but what is SESMA? There has been a few comments on it?

And as for each engine having sucked up different amounts of dirt, any thoughts that the one that ate more might have hit first? My guess is it slid right because there was right bank/yaw at impact, and therefore you'd expect the right engine to have more earth in it.

Just my humble thoughts.

[Propjet88]

EMI

There was an interesting comment a few pages earlier about it being SOP for the police to use cell jammers at certain times. Noone has picked up on it. Does anyone know the timing / location of the PM's motorcade at the time of the accident? Any technocrats have any idea how much RF power is put out by these jammers and over what distance they work?

[ChristiaanJ]

Originally Posted by lomapaseo

I'm still struck by the differences in the visible dirt ingested between the two engines. The one engine with the dirt stuffed into the core compressor sure appears to have been at high power.

Didn't expect that from you.
The aircraft probably wasn't entirely level during 'touchdown'.
Then one of the main gears was shedded, the other was stoved through the wing.
With such dynamics, you expect both engines to 'shovel' up the same amount of dirt? Come on....
Let the AAIB sort out at what rpm the engines were.

[sandbank]

Malaysia Airlines 777 Perth?

Is there any parallel with the incident in 2005 involving a Malaysian Airlines 777-2H6ER (9M-MRG) ?

Climbing through FL380 rhe crew reported a low airspeed warning on the EICAS. Then instruments showed the aircraft was approaching the overspeed limit and the stall speed limit simultaneously.

The aircraft pitched up and climbed to FL410 and the indicated airspeed decreased from 270 kts to 158 kts. The stall warning and stick shaker devices also activated.

The captain disconnected the autopilot and lowered the nose of the aircraft. The autothrottle commanded an increase in thrust which the captain countered by manually moving the thrust levers to the idle position. The aircraft pitched up again and climbed 2,000 ft. Both left and right autopilots caused the aircraft to bank and the nose to pitch down, so the captain decided to fly the aircraft manually. During the approach, the aircraft warning system indicated a windshear condition but the crew continued the approach and landed the aircraft without further incident.

It was found that "An anomaly existed in the component software hierarchy that allowed inputs from a known faulty accelerometer to be processed by the ADIRU and used by the primary flight computer, autopilot and other aircraft systems".This hadn't been identified in the original testing and certification

The FAA issued an emergency AD to prevent the operational program software using data from failed sensors

[Clarence Oveur]

Would anybody have access to schematics of the engine control system? Preferably at AMM level, but an FCOM description would be welcome as well.

If schematics are unavailable, I would be grateful if someone would take the time to give a detailed description of the system.

I am particularly interested in sensor and command input/output to/from the EEC.

[Contacttower]

Noone has picked up on it. Does anyone know the timing / location of the PM's motorcade at the time of the accident? Any technocrats have any idea how much RF power is put out by these jammers and over what distance they work?

There does seem to be some confusion over this (some newspapers initially reported that GB was travelling on the road under the approach at the time of the accident)...but it would appear that he was on board his aircraft when the accident happened.

[Feathers McGraw]

Propjet88

Jammers work by exploiting the difference in signal received by a receiver from a nearby and remote transmitter.

Since the receiver sees signal levels essentially related to distance squared from the transmitter, it means that a fairly low powered jammer can prevent the receiver hearing a more powerful transmitter at a greater distance.

What is more difficult is when you need to jam a significant bandwidth, say a whole cellular band, with a noise-like signal. The power needed is then integrated over that bandwidth so the design of the jammer needs to allow for that fact.

Since GB and co were about 1km away at the time, it would have taken a stupendous output power to affect the 777 from there, such a power level would probably be enough to disable everything electronic local to them and possibly the humans too.

[Contacttower]

Sorry to be a military pilot bore, but what is SESMA? There has been a few comments on it?

I believe it stands for 'Special Event Search and Master Analysis' and is part of BA's on board telemetry system which monitors and records aircraft performance/configuation etc.