sooty655

Not sure about your wording there, airfoilmod. I'm sure GE, RR and others all designed for the level of fuel icing anticipated/specified by Boeing.

If the GE arrangement really is better at accepting the unexpected quantities of ice dumped from the pipework, then that is luck, not design.

Two rollbacks over the entire 777 operation is a very small statistical sample. I'm not yet convinced this is only a RR problem.

Sooty

airfoilmod

The Icing of Fuel was explicitly shown in the schematic for GE. It was not shown on the schematic from the same source for RR. I mentioned that before, and meant only that, not that RR hadn't addressed the problem as understood at the time. The presence of three separate HX on GE may or may not be more effective, and your noting that only two rollbacks have been documented for the Trent is quite valid.

airfoil

Sir Richard

tanimbar

The 3C you quote is the required margin above freeze point, not an actual temperature.

With -47 fuel the minimum fuel inlet temperature would have to be -44 for RR engines.

Similarly GE could accept -47 and CFM -42 at the engine fuel inlet.

But perhaps you knew that already.....

tanimbar

Thanks for making clear the figures in that document that I mentioned.

Not for sure. It was one possibility I identified from the words used in the document.

Thanks again.

Mismatch

Some pounds here plus some pounds there make up for two-digit tons in the end. I am sure, weight IS an issue in aviation. And it may even be an issue WHERE it is.

airfoilmod

The prior ref. to weight involved a hypothetical increase for additional system design in the Trent. Specifically a bypass for Fuel around the FOHE. The Trent is already leaner by 2,600 lbs than its GE counterpart, so some room may exist for a contemplated addition of Plumbing. Of course weight is important. Safety frequently revolves around weight. Where it is, and how much there is.

AF

HarryMann

Thanks Airfoilmod for clarifying that.

Of course weight matters, but in context... if you had 1,000 similar linkpins or rivets holding something on, you would spend a lot more time optimising the design for size, weight, material and stress levels as well as on testing to assure your final release.

But if you have 2, one per elevator for instance, over-designing them by 50% wouldn't make a bat's hat of it, would it, and in fact, because being only two in a critical path, would probably require you to apply a larger proof/ultimate factor, a wider fatigue factor and for peace of mind, a larger Reserve Factor.

I've seen one or two rather crass and ultimately deadly results from not understanding or formally addressing a sensible weight/citicality balance... e.g. a single 7/32" shear pin might suffice and meet the design case, but one day fail, a 1/4" might never go anywhere near a failure mode. Weight difference approx. zero!

If an engine needs a by-pass around a heat exchanger, being on the C.G or close to it, even if it cost one pax, or two on MTOW, if it needs it - it needs it - FULL STOP

barit1

I am really surprised that Boeing let the R-R Triple7 out of the barn without very aggressive fuel heating capability. Boeing's experience with fuel icing goes back six decades - and they have a library full of lessons learned from B-47, B-52, 707 etc.

Look at 747 etc. fuel schematics and you'll see what I mean.

sky9

The relevant point about ETOPS is that twins fly about 4000ft higher than the equivalent 4 engined aircraft. That must mean lower fuel temperatures over the same flight time. Has anyone checked?

punkalouver

Any details would be appreciated.

Green-dot

Just to reflect on the ice theory. Last week I personally experienced something totally unrelated to this incident but then perhaps not.

While extracting some money from an ATM (automatic teller machine) my mobile phone was activated as someone made a call. At that exact moment I was logged into the machine and had punched in the first of 2 digits for the amount I wanted to extract (40 euro's) when the machine went berzerk. I never got to punching in the second digit or confirm the amount by pushing the "ok" button as it spontaneously returned my card and released 100 euro's.

I finished the call and then, confused, I made another extraction with the phone off and the ATM performed as advertised in a normal way.

The incident is now under investigation.

This brings me back to BA38 and how perhaps a one in a zillion chance of EMI/HIRF could have ended its carreer prematurely.

Green-dot

vapilot2004

The PM's antenna farm radiations coupled with a nattering nymph's Nintendo DS
in row 13 caused both metal-encased & shielded ECC units to go bananas.

Ice was a related factor as there was not enough in the mother's drink in row 13 so there was just enough added vodka to knock her out keeping the woman
from such maternal duties as slapping the wayward child on the noggin when
he continued playing the small electronic aircraft systems jammer otherwise
known as a portable video game.

Green-dot

When reporting the ATM anomaly to the bank I was met with the same cynical reaction. The reaction was that it was impossible radiation from a mobile phone could cause the ATM to fail. "It was just a matter of coincidence . . . . ."

At least I'll give credit to the AAIB as they did investigate the possibility of EMI/HIRF affecting BA38. Question remains though if all conditions at the time could ever have been duplicated and if all essential data was recorded. For now I will wait until the final report has been released.

Green-dot

misd-agin

Barit1 - I am really surprised that Boeing let the R-R Triple7 out of the barn without very aggressive fuel heating capability. Boeing's experience with fuel icing goes back six decades - and they have a library full of lessons learned from B-47, B-52, 707 etc.

-----------------------------------------------------------------------

Any chance Boeing and R-R had a difference of opinion, and R-R stated "our engineering says it's good enough, and you're just operating on opinion" ?

Monom

757 is my speciality and I know why, when on the walk-round, the left wing always pours water down the back of my collar whilst the right wing remains frosty. Is the 777 walk-round similar? Without going all the way through the thread, I would assume that wing tanks were in use at the time. If so, all a bit odd?
Monom

Joetom

Thought I read, Boeing purchased MMM, that 777 appears to be a tough old bird, great landing by the crew as well.

Mmmayday38

JoeTom wrote;
"Thought I read, Boeing purchased MMM, that 777 appears to be a tough old bird, great landing by the crew as well."

If Boeing did, then they bought it off the insurers and it was in small cut up sections!

Will Fraser

May I ask a pertinent question? Anybody still breathing at AAIB? Have they been redundantated?

chris weston

Will,

AAIB are still well within their averaged time frame.

Nothing sinister here.

I also believe (naively many will say, no pun intended) this thread actively informed AAIB of sensible possible lines of enquiry...........

All covered in great detail in earlier posts.

CW

Will Fraser

chris weston - Thanks, and I agree this thread was food for thought. No acknowledgments are necessary, nor will they be likely forthcoming. That is as it should be. Honestly, I think some of the boffins at AAIB might resent some of the comment here, I probably would. I did not mean to imply any suggestion of conspiracy or anything sinister, just trying to foment a comment; thanks again. Also, I would definitely include your comments on thread on my list of very constructive contributions.