BA038 (B777) Thread
Join Date: Jan 2008
Location: Weedon, UK
Age: 77
Posts: 125
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by airfoilmod
In the case of the GE, where fuel icing is addressed in the design,
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
Guest
Posts: n/a
sooty
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
airfoil
Join Date: Dec 2003
Location: South of Watford
Posts: 147
Likes: 0
Received 0 Likes
on
0 Posts
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.....
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.....
Join Date: Feb 2008
Location: UK
Posts: 50
Likes: 0
Received 0 Likes
on
0 Posts
Sir Richard - min fuel inlet temp is relative, not absolute
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.
But perhaps you knew that already...
Thanks again.
Join Date: Apr 2008
Location: Right here, right now.
Age: 48
Posts: 8
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by HarryMan
...Weight, weight, weight...
Honestly, weight is really not a problem these days on commercil aircraft when we are talking of a few pounds, seriously.
Think of just a crew putting on a few pounds each, let alone big blokes Vs small blokes, or the whole pax... or just a gallon or two extra fuel - honestly, things are NOT that critical that it would come into a design engineer's decision when safety is an issue.
...
Honestly, weight is really not a problem these days on commercil aircraft when we are talking of a few pounds, seriously.
Think of just a crew putting on a few pounds each, let alone big blokes Vs small blokes, or the whole pax... or just a gallon or two extra fuel - honestly, things are NOT that critical that it would come into a design engineer's decision when safety is an issue.
...
Guest
Posts: n/a
Mismatch
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
AF
Join Date: Jan 2008
Location: Herts, UK
Posts: 748
Likes: 0
Received 0 Likes
on
0 Posts
Mismatch
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
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
Join Date: Feb 2005
Location: flyover country USA
Age: 82
Posts: 4,579
Likes: 0
Received 0 Likes
on
0 Posts
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.
Look at 747 etc. fuel schematics and you'll see what I mean.
Keeping Danny in Sandwiches
Join Date: May 1999
Location: UK
Age: 76
Posts: 1,294
Likes: 0
Received 0 Likes
on
0 Posts
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?
Join Date: Nov 2004
Location: Here, there, and everywhere
Posts: 1,146
Likes: 0
Received 19 Likes
on
12 Posts
Join Date: Feb 2008
Location: Subterranea
Age: 70
Posts: 187
Likes: 0
Received 0 Likes
on
0 Posts
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
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
Join Date: Aug 2005
Location: fairly close to the colonial capitol
Age: 56
Posts: 1,693
Likes: 0
Received 0 Likes
on
0 Posts
With Mr. G Dot's post, we've now come nearly full circle in the thread.
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.
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.
Join Date: Feb 2008
Location: Subterranea
Age: 70
Posts: 187
Likes: 0
Received 0 Likes
on
0 Posts
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.
in row 13 caused both metal-encased & shielded ECC units to go bananas.
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
Join Date: Jan 2006
Location: US
Posts: 2,205
Likes: 0
Received 0 Likes
on
0 Posts
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" ?
-----------------------------------------------------------------------
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" ?
Join Date: Jan 2006
Location: New Forest
Posts: 9
Likes: 0
Received 0 Likes
on
0 Posts
Ice
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
Monom
Join Date: Feb 2009
Location: Worcester
Age: 59
Posts: 38
Likes: 0
Received 0 Likes
on
0 Posts
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!
"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!
Second Law
Join Date: Jan 2008
Location: Wirral
Age: 77
Posts: 113
Likes: 0
Received 0 Likes
on
0 Posts
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
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
Join Date: Apr 2009
Location: Petaluma
Posts: 330
Likes: 0
Received 0 Likes
on
0 Posts
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.