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Concorde question

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Concorde question

Old 13th Dec 2017, 16:17
  #2021 (permalink)  
 
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Originally Posted by Lancman View Post
. I'm just interested in what the circumstances were that allowed this restriction to be over-ridden.
Extra taxi fuel I should think, which should be burned off before take off (it wasn't on the accident aircraft because of the change to a nearer runway).
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Old 13th Dec 2017, 17:08
  #2022 (permalink)  
 
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@Lancman

There a a lot of misinformation sculling around on this.
The final report states that the overfill was 300 litres (237kg) put into the engine feeder tanks 1 to 4. These tanks are grouped to have approximately equal moment about the CG so if it was, as seems likely, 75 kg in each there would have been negligible effect on the CG.

There was no overfill into tank 5.

It is all a long time ago, but as SSDriver says the overfill capability was probably there to cater for extended taxi or waiting time operations.

In this particular case the dispatcher ordered 2000kg rather than the standard AF allowance of 1000 kg to be loaded for taxiing presumably because he/she believed a more distant runway would be used because of maintenance work, but in the event the pilot asked for and was given the usual runway which meant that the aircraft was overweight for take off because only 1000 kg of taxi fuel was used. [Plus of course the additional baggage]
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Old 13th Dec 2017, 17:20
  #2023 (permalink)  
 
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@ CliveL.

Thank-you for your replies. As you say, it was all a long time ago.
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Old 13th Dec 2017, 18:59
  #2024 (permalink)  
 
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Originally Posted by CliveL View Post
The final report states that the overfill was 300 litres (237kg) put into the engine feeder tanks 1 to 4. These tanks are grouped to have approximately equal moment about the CG so if it was, as seems likely, 75 kg in each there would have been negligible effect on the CG.

There was no overfill into tank 5.
So Hutch is wrong when he says in the interview that tank 5 was being continuously topped up from tank 11 as fuel was burned off during the T/O? I've had a quick look at a simplified fuel system diagram and while it shows no direct transfer route from tank 11 to tank 5, would there be an indirect one via the forward trim tanks?

And as the extra baggage was in the rear hold, and Tank 11 was full, that would explain the rearward CG and the desire of the crew to get fuel out of tank 11 ASAP and into the wings, Did it all go to tanks 1 to 4 via the forward trim tanks, with none going to tank 5 ( the 'accident' tank)?
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Old 13th Dec 2017, 20:12
  #2025 (permalink)  
 
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If the intent was to get the CG forward, what would be the point in transferring fuel to anything other than the forward trim tank? In particular why to the engine feed tanks which are arranged to be CG neutral?

However, the BEA report says:
It has been established that the aircraft began taxiing with tanks completely full. Before line-up, the crew carried out fuel transfer so as to bring the CG to 54% for takeoff. During this operation, the fuel burnt from the feeders during taxiing was replaced by the fuel contained in tank 11.
As a result of the transfer, feeder tanks 1 to 4 were full before line-up. In addition, main tanks 5 and 7, which had not been called on during taxiing, had remained full.
Between 14 h 41 min 55 s and 14 h 43 min 10 s, the time when the tank ruptured, the quantity of fuel burnt by each engine is estimated at 219 kg (15 kg between 14 h 41 min 55 s and engine power-up, 204 kg between power-up and the rupture). This was therefore the quantity of fuel taken from each feeder tank.
The transfer of fuel from tank 5 to feeder tank 1 deliberately only starts when the level in the feeder reaches 4,000 kg, that is to say 198 kg less than full. This leads to estimate that 219 kg – 198 kg = 21 kg was the quantity of fuel taken from tank 5.
I can't make that compatible with tank 5 being continually topped up no matter how I try

Last edited by CliveL; 13th Dec 2017 at 20:24.
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Old 14th Dec 2017, 11:05
  #2026 (permalink)  
 
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Because the forward trim tanks were already full so not an option to put it there, unless there is a route from there to tank 5, in which case it might be being transferred to the trim tanks from tank 11, and on to tank 5? The only place to put fuel (if all tanks are brimmed) is into a tank(s) which are being emptied by feeding the engines. If there is no route from the forward trim tanks to tank 5, then perhaps in normal ops tank 5 would be topping up the feeder tanks as the engines drain them, but topping up the feeders from tank 11 meant tank 5 remained full?

The objective is to get it out of tank 11 ASAP to try to get the CG further forward.
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Old 14th Dec 2017, 12:35
  #2027 (permalink)  
 
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Tanks 5 and 7 inlet valves have an ‘override’ position, do they not?

During the t/o roll, while the trim transfer pumps in 11 will be off, the de-air pump would allow flow through the trim transfer pipes to any tank with an open valve. The valves *should* be closed, unless someone had been creative with any override selections and failed to return them to normal.
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Old 14th Dec 2017, 14:14
  #2028 (permalink)  
 
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Originally Posted by EXWOK View Post

During the t/o roll, while the trim transfer pumps in 11 will be off
Hutch says they should be 'off' for T/O roll, but on this occasion, to shift CG forward, they were 'on'.
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Old 14th Dec 2017, 14:16
  #2029 (permalink)  
 
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@SSDriver

You are quite right; I should have checked that
A simple check of BEA's figures shows that they were assuming transfer into the feeder tanks.
Their sums say one needs to transfer about 700kg to make a CG shift from 54.2% to 54% (starting with a ZFCG of 52.4%). However, the engineer's panel after the crash showed that he had dialled in the loadsheet ZFCG at 52.3% so the fuel system would have transferred only 350 kg.
I can't see anything to suggest otherwise than that fuel transfer was stopped when TO began and that tank 5 remained at 94% total capacity throughout

We crossed in post, but where did you get the information that transfer was continued through take off? I didn't find anything in the official report
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Old 14th Dec 2017, 20:20
  #2030 (permalink)  
 
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CliveL

From this video. Have you not seen it? Ignore the garish sensational 'cover'. John is a highly experienced BA Concorde captain.

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Old 15th Dec 2017, 00:03
  #2031 (permalink)  
 
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I’m not sure we *know* the tank 11 txfr pumps were on.

The 5/7 inlet valves were in the override position.

Even if the T11 txfr pumps were off, the de-air pump would pump fuel to the trim txfr pipes and hence to 5/7.

All assuming I remember the report correctly.

The nub being, if you ‘hide’ fuel and forget to return the 5/7 inlet valves to normal, you will still feed 5/7 even if the 11 pumps are off.
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Old 15th Dec 2017, 08:15
  #2032 (permalink)  
 
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@SSDriver

Yes, I had seen the video, but although he states things with apparent confidence his view is not supported by the formal report.
Consider the final report wording quoted in my post 2025:
Before line-up, the crew carried out fuel transfer so as to bring the CG to 54% for takeoff. During this operation, the fuel burnt from the feeders during taxiing was replaced by the fuel contained in tank 11.
The French (definitive) version uses "a effectué" rather than "carried out" which suggests they completed that task. If so, why abandon the standard Concorde procedure?

The BEA went to some trouble to establish the amount of fuel in tank 5 at the time of rupture. The process they describe makes no mention of any transfer from tank 11 into tank 5, or indeed any transfer of fuel into that tank during the take off run. In fact they concluded that there was a reduction of 21 kg as a result of normal transfer from tank 5 to tank 1 when that tank became depleted.
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Old 19th Dec 2017, 11:07
  #2033 (permalink)  
 
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To the top for users that have expressed an interest in the thread. What great reading this thread provides.

Thanks to all that have contributed.
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Old 28th Dec 2017, 22:29
  #2034 (permalink)  
CMM
 
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Excellent thread and may it continue!

I have a question I don't think has been previously posed. In terms of the BA fleet, what was the typical fleet rotation routine?

Out as BAW1, return as BAW2, then off to the maintenance area, with a new airframe for BAW3 and 4? Essentially, was there a pattern (presumably to keep the cycles even across the fleet?).

I appreciate this may have changed after 'fleet reduction', so to speak...

Thank you!
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Old 30th Dec 2017, 21:48
  #2035 (permalink)  
 
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During my 27 years as a licensed aircraft engineer on the Concorde fleet I can not recall any type of rota for flying the aircraft. Whilst in theory it would be nice to equal their flying hours it was not possible as A/C engine hours would often dictate. The engine was made up of different modules & when that module became time x then the engine was changed & went away for the module to be replaced/overhauled.

You would often face a situation where you tried to limit flying hours of an A/C so you could change an engine to coincide with a service check. Also bearing in mind the delivery dates of each A/C G-BOAC was the first due to it having the BOAC reg. followed by OAA,OAB,OAD,OAE . OAF, & OAG both arrived later.

OAC returned to Filton under warranty for a while & OAG was laid up for a long time before being recommissioned . Whilst we had 28 engines on the wing through out the fleet there were only about 8 spare engines. Don't know about Air France Engines. Like all engines they suffer from ingestion of FOD & oil leaks etc. so engines never really went to their full time x hours. As a flying spanner on several charters you always prayed for G-BOAD as it was always the most reliable of the fleet.

They all had their own characteristics. Most Captains had a favourite A/C
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Old 5th Jan 2018, 16:50
  #2036 (permalink)  
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Thanks Mexican! I am pleased to have tempted you into the thread. I would be intrigued to find out if there are any other favourites that our friends here could declare. The cynic in me makes me wonder if they chose AD for the ITVV video for the reason you say! :P
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Old 5th Jan 2018, 20:02
  #2037 (permalink)  
 
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Favourite: OAF for fuel burn and subjective personal preference.

OAC second for the reg!.

OAD was indeed the schedulers' favourite for long charters although I have to say that I didn't have fewer or greater tech issues with it c.w. the others. Def. not a favourite on BGI because it burnt a bit more fuel than some others (e.g. Fox and Golf).
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Old 6th Jan 2018, 18:45
  #2038 (permalink)  
 
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OAC was the first off the Filton line, and therefore the heaviest (they learned to add lightness as production progressed!). That would have had an effect on range and possibly CG for that aeroplane. It also had a wing repair (following an engine fire I believe) which added even more weight.
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Old 6th Jan 2018, 19:22
  #2039 (permalink)  
 
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Regarding the fuel burn differences would you have a ballpark number to quote?
.1%? 1%? More?
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Old 1st Feb 2018, 09:07
  #2040 (permalink)  
 
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Concorde at Kia Tak.

"BRITISH AIRWAYS Concorde at Kai Tak (1996)" on youtube.

It's been many years since I flew into Kai Tak. If memory serves me correctly, landing on the Southern Runway, it was a mandatory go around should the extended centre line be crossed on approach. In this clip the aircraft executes a shallow left turn on short final, proving to me at least, they went through the extended centre line.

Was BA or Concords exempt from this rule?
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