BA 777 Update

That is kind of weird. We turn down the center tank to about 1000 lbs immediately and then go tank wing to engine... on the 757/767.
 
Doug Taylor said:
That is kind of weird. We turn down the center tank to about 1000 lbs immediately and then go tank wing to engine... on the 757/767.
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Burning the fuel out of the center tank first, and leaving fuel in the wings for last, makes sense from a variety of perspectives. It is probably required, due to wing bending limitations. Of course, that leaves the coldest fuel for last, but I would assume the 777 has an auto fuel circ system, (or, considering Boeing, a procedure the crew has to follow...), to keep the wings mixed with the (probably) larger center tank.
 
Alright, so hopefully nobody flames me for even posting this, but this is a conversation I overheard my airline's manager of safety and manager of training having the other day while I was waiting nearby for my oral.

Safety guy comes in and says there is a new theory about what happened to the BA 777 at heathrow...i didn't catch where he said he heard it from. Anyway, he said something to the effect of there being a royal family motorcade that was passing the airport on a road that would come near final approach course of the 777 and that the motorcade has equipment that gives of some kind of electric scrambling signals of some sort. Theory is that the signals somehow interfered with the FADEC's and caused the engines not to respond to the pilot inputs.

It sounds pretty crazy but I just thought I'd share in case anybody was interested.

Oh yeah, as for the oral, I passed! On to the sim!
 
Copperhed51 said:
Alright, so hopefully nobody flames me for even posting this, but this is a conversation I overheard my airline's manager of safety and manager of training having the other day while I was waiting nearby for my oral.

Safety guy comes in and says there is a new theory about what happened to the BA 777 at heathrow...i didn't catch where he said he heard it from. Anyway, he said something to the effect of there being a royal family motorcade that was passing the airport on a road that would come near final approach course of the 777 and that the motorcade has equipment that gives of some kind of electric scrambling signals of some sort. Theory is that the signals somehow interfered with the FADEC's and caused the engines not to respond to the pilot inputs.
Click to expand...

Don't know about any royals, but Gordon Brown's 777 was on the taxiway fixin' to leave for China at the time of the accident.

My favorite theory so far is:
  1. A significant amount of water froze in the center tank, which hindered the function of the scavenge pumps (a low output pump pressure should have triggered an EICAS message. I'm not aware of any water/contamination detection, other than filter bypasses).
  2. During descent and approach, ice melted enough to let the scavenge pumps move more fluid again, which belched water/fuel into both mains (both, being the key there)
  3. Enough ice made its way into the preheater and on to the engines to hinder the ability to respond to an increase in thrust.
The only problem with that theory is that the temperature of the fuel in the tanks doesn't get back above 0°C until a long time after the aircraft has landed and parked. There are heat exchangers for the hydraulic system in the center tank, but they'd have to be abnormally warm to keep the temperature above freezing. I guess, if the liquid water were agitated by a pump it might freeze into smallish crystals in the mains.

The EEC does relay the thrust command it thinks it received, so I'm confused as to why there is speculation about the improper function of the EEC (due to EMI or whatever). The EEC's echo of the received command should be in the recorded flight data. I would expect something much more complex like an engine computer to be affected by noise much more easily than a wire and servo for a fuel metering unit ... at least, affected more consistently.
 
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