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BA038 (B777) Thread

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BA038 (B777) Thread

Old 18th Feb 2008, 21:39
  #61 (permalink)  
 
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Several people have said that the A/P did the best possible job under the circumstances. I'm sure the crew did what any good crew would have done in that situation, but.....

If they had disconnected the A/P when the engines failed to respond to the manual throttle movement and flown the aircraft towards the grass, I bet they would have had enough energy for a decent flare. The landing gear might not have liked coming down in the bog, but I'd take that over a no-flare, near the stall plonk-down. Might have saved some poor sod a broken leg.

Of course you don't expect your jet to turn into a glider on short final and it is easy to speculate with the benefit of hindsight. I'm sure somebody will try it in the simulator, let us know how you get on.

Flame on.
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Old 18th Feb 2008, 21:40
  #62 (permalink)  
 
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Bearcat wrote

from the accident report...

After the aircraft crossed the Ural mountain range in Russia it climbed further to FL380 where the ambient temperature dropped to as low as minus 76C


What is the enviornmental envelope re min temps for the 777. I know the airbus 320 is -70c
Does anyone know the answer to this question?
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Old 18th Feb 2008, 21:45
  #63 (permalink)  
 
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What about the cross feed opening and the APU start initiated while the glider was flown by the AP ? What kind of SOP is that ?
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Old 18th Feb 2008, 21:52
  #64 (permalink)  

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What about the cross feed opening and the APU start initiated while the glider was flown by the AP ? What kind of SOP is that ?
Well it is not. It is evidence of the crew trying anything to keep flying. They were not exactly in a "SOP" situation. More out of teh box desperate try anything situation.
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Old 18th Feb 2008, 21:59
  #65 (permalink)  
 
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X-feed and APU..

I imagine that these actions were initiated by the pilot in the middle (relief pilot or whatever he is called in BA).
Maybe not SOP - but sensible actions in a very stressful and confusing situation!
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Old 18th Feb 2008, 22:02
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Two odd things stand out in the report regarding the fuel.

Initial results confirm that the fuel conforms to Jet A-1 specifications and that there were no signs of contamination or unusual levels of water content.
And...

The specified freezing point for Jet A-1 fuel is -47C; analysis of fuel samples taken after the accident showed the fuel onboard the aircraft had an actual freezing point of -57C.
Is it normal for Jet A-1 to have a freezing temp of -57C? Is this really pure Jet A-1, or is it mixed with something else?
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Old 18th Feb 2008, 22:07
  #67 (permalink)  
 
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If they had disconnected the A/P when the engines failed to respond to the manual throttle movement and flown the aircraft towards the grass, I bet they would have had enough energy for a decent flare.
I somewhat agree. Not only that, if they had put it onto manual, decreased demand on the engines then the blockage/inleakage/cavitation would have subsided then full thrust may have been regained.

However, I don't feel that we can suggest that the chaps on board did anything wrong. There were no fatalities, no serious injuries, and they landed in a distance shorter than I land a Piper Cherokee into.

T.
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Old 18th Feb 2008, 22:13
  #68 (permalink)  
 
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Is it normal for Jet A-1 to have a freezing temp of -57C? Is this really pure Jet A-1, or is it mixed with something else?
A good question - any "lights" in the fuel to reduce the melting point would indeed result in a higher liklihood of caviation in the pumps, or could result in waxes in fuel lines to being stripped then passed through once the right temperature (read 'altitude') is reached.

T.

PS Is it normal for fuel not to be tested for water after fuelling?
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Old 18th Feb 2008, 22:23
  #69 (permalink)  
 
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X-feed and APU

From the first page of the report. So what are you talking about?!

avrflr,

Glad you said that. I'd duck if I were you
I'm talking about these statements from the preliminary report:


The fuel crossfeed valves were closed in flight according to the flight crew, but the switches were found in the open position and only one valve was open. In the days following the event, the flight crew has added additional details to their report. The crew now believes they opened the valves just prior to impact and the airplane lost power before both valves moved to the open position.
The auxiliary power unit (APU) began its auto start sequence, even though the buses were still powered. In the days following the event, the flight crew has added additional details to their report. The crew now believes they turned the APU on prior to impact. There was sufficient time before the impact for the APU inlet door to open, but not for the APU fuel pump to turn on or the APU engine to start spooling up.

Is the crew supposed to retract the added comments they made about it ?
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Old 18th Feb 2008, 22:27
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UUUUUUUUUUMMMMMMMMMMHHHHHHH???????????Air in the fuel pumps where normally fuel should be???? Me thinks this is starting to go in a certain direction!!!!!!!11
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Old 18th Feb 2008, 22:31
  #71 (permalink)  
 
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Post flugmann

I read so much rubbish here on PPRuNe and the 777 acident is typical of the misinformed judgemental crap which somehow seems to dominate !! It's a good idea to have these forums but who aside from the newspapers benefits ? hey ho !![
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Old 18th Feb 2008, 22:35
  #72 (permalink)  
 
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sispanys ria

I think the 'report' you quoted actually appeared on a US aviation site, and purported to be a leak from the official investigation. The initial report, and the update report on Jan 23rd, didn't mention the pilots' 'recollections'.

So I think we can discount the leak?
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Old 18th Feb 2008, 22:50
  #73 (permalink)  
 
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Originally Posted by tiggerm0th View Post
A good question - any "lights" in the fuel to reduce the melting point would indeed result in a higher liklihood of caviation in the pumps, or could result in waxes in fuel lines to being stripped then passed through once the right temperature (read 'altitude') is reached.

T.

PS Is it normal for fuel not to be tested for water after fuelling?
Yes, it is normal. The fuel gets sample tested during the refuel, and for various reasons it is highly unlikely that water can get on to the aircraft at this point. The AAIB reports states that there was not an unusual amount of water in the fuel recovered from the aircraft, so water does not look like a likely culprit.

Also the schedule for water drains and the likely freezing temperature of the fuel was previously explained/predicted by other posters on the forum, so nothing unusual or unexpected there. Even the FOD in the tanks doesn't really explain much. Still a big bloody mystery.

Last edited by avrflr; 18th Feb 2008 at 23:01.
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Old 18th Feb 2008, 22:51
  #74 (permalink)  
 
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Water Drain Checks

PS Is it normal for fuel not to be tested for water after fuelling?
Yes.

The fuel at the bowser will be checked by the refueller before and after refuelling.

The fuel in the tanks will only be checked as required by the maint schedule. (Daily Check, First flight of the day, 'x' hours on the ground etc).
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Old 18th Feb 2008, 23:02
  #75 (permalink)  
 
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Is the crew supposed to retract the added comments they made about it ?
In light of the first reports, I took the last report to indicate that, prior to the event (during the normal part of flight down to 700'), the crossfeeds were not activated.
As previously discussed, the 777 SOP for low fuel is to open one crossfeed. The Captain may have suspected low fuel. And two sources are better than one (electrically, too, it seems... cf spar valve comments in the report).

Re the comments about seals....
The fuel is being pumped from the tanks under pressure (by wing tank pumps). Any leaks in seals are going to put fuel to atmosphere, not air to fuel lines. The wing pumps were working normally.

Re the comments about foreign objects being in the tanks being put there by maintenance...
Not diverting attention away from maintenance, but how big are the filters (if there are any) on the refuel bowsers?
Also, I've never been inside the tanks of a 777... Just wondering how big the screens are on the pump inlets (frying pan size?).

I'd love to know what caused this...I've been having similar problems with my car for weeks... and can't figure out whether it's the ECU or fuel flow (coincidentally, I found a plastic foreign object under the pump inlet.... the problem still there after removing it, however)
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Old 18th Feb 2008, 23:19
  #76 (permalink)  
 
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Re the references to JetA1 in the report....

Would this be because the fuel loaded in Heathrow was Jet A1 and flight crews are told, where there are combinations of fuel types in tanks, to enter the freeze temperature of the fuel type with the highest freeze point into the FMC/CDU?

If they entered -47, then the aircraft would have warned them at -44 (3 degree buffer)....well above the freeze point of the remaining fuel.

I notice the word satisfactorily is used in several places in the report. What margin of error does "satis" allow?
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Old 18th Feb 2008, 23:32
  #77 (permalink)  
 
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Originally Posted by NSEU View Post
Re the comments about seals....
The fuel is being pumped from the tanks under pressure (by wing tank pumps). Any leaks in seals are going to put fuel to atmosphere, not air to fuel lines. The wing pumps were working normally.
Not sure I follow you there. If there's a blockage upstream of the HP pump the pressure in the line feeding into it is going to go from positive to negative pretty quickly (the pumps cavitated for some reason - not enough pressure being delivered to them is a reasonable inference).
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Old 18th Feb 2008, 23:37
  #78 (permalink)  
 
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Originally Posted by NSEU View Post
Re the references to JetA1 in the report....

Would this be because the fuel loaded in Heathrow was Jet A1 and flight crews are told, where there are combinations of fuel types in tanks, to enter the freeze temperature of the fuel type with the highest freeze point into the FMC/CDU?

If they entered -47, then the aircraft would have warned them at -44 (3 degree buffer)....well above the freeze point of the remaining fuel.

I notice the word satisfactorily is used in several places in the report. What margin of error does "satis" allow?
Given that the lowest recorded fuel temperature was -34 degrees, it's a moot point.
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Old 18th Feb 2008, 23:47
  #79 (permalink)  
 
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I don't think you can enter the fuel temp in that way. I believe the Boeings are hard wired to warn you at -37C.
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Old 18th Feb 2008, 23:56
  #80 (permalink)  
 
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Four pages of speculation based on an interim report of a basically intact a/c has produced suggested
1. Fuel contamination - culpable
2. FOD blockage of tank outlet - culpable
3. Loss of sealant plasticity due to abnormal low temp (as per Challenger O rings?) which may allow air to be sucked into the fuel flow - not predicted
May explain fuel leak on landing but more likely due to heavy landing
4. Cavitation damage to fuel pump insufficient to impair pump performance, suggesting recent damage - symptom not cause
5. Loss of thrust from both engines at ~200' -SOD's law

Would not partial blockage at tank outlets cause low pressure downstream causing a dose of the 'bends' in the fuel system or draw air in via any sealant crack, thus causing cavitation?

It appears that all pilots, both human & auto, remained fully functional

I await the final report with interest
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