BA038 (B777) Thread
the lunatic fringe
Join Date: May 2001
Location: Everywhere
Age: 67
Posts: 618
Likes: 0
Received 0 Likes
on
0 Posts
Would anybody be willing to make a guess as to the likelihood of the FAA ordering a worldwide grounding of the 777-200ER with the Trent 800
The operators of the aircraft have been aware of these results for some time. So have the FAA. Aircraft rotations and new methods of operation have long since been implemented.
Join Date: Apr 2004
Location: leafy suburbs
Posts: 308
Likes: 0
Received 0 Likes
on
0 Posts
DeScally
The "authorities" do not take the decision to ground aircraft lightly. I would suggest this is not a grounding candidate.
I would expect the operation of the aircraft to be restricted. eg No flight sectors over 10 hours to be undertaken, Cruise altitude reduced in areas of extreme low temperatures etc.
Implementing of any mod action to be done within a time scale of perhaps, say, 24 months?
The "authorities" do not take the decision to ground aircraft lightly. I would suggest this is not a grounding candidate.
I would expect the operation of the aircraft to be restricted. eg No flight sectors over 10 hours to be undertaken, Cruise altitude reduced in areas of extreme low temperatures etc.
Implementing of any mod action to be done within a time scale of perhaps, say, 24 months?
Join Date: May 2006
Location: London
Age: 69
Posts: 237
Likes: 0
Received 0 Likes
on
0 Posts
Quote :
Phil, I beleive it does at least allude to where it came from...
The varied (and higher levels) of water can come from less than homogeneous distribution in the tank, but mainly from prior upstream ice melting, either from the boost pump screens or from pipewrok less far upstream.
As I took it to mean ppm at the point of interest e.g. in the pylon pipework or adjacent main tank pipework.
I believe they also inferred that concentrations could vary wildly from time to time in the fuel passing through the critical pipework sections, up to possibly 125ppm.
.. without of course re-reading or quoting directly.
unquote
I could well be wrong, but I believe that is more a coment on the problems of measuring water content, rather than anything to do with actual water in the accident aircraft. The report does say it expected a lower than maximum water content because of ice forming at the bottom of the fuel tanks, so that the fuel circulating would have a lesser ppm of water. What the comment MAY imply is that the tests on fuel either for ground supply or in aircraft sampling may need examination.
.
Phil, I beleive it does at least allude to where it came from...
The varied (and higher levels) of water can come from less than homogeneous distribution in the tank, but mainly from prior upstream ice melting, either from the boost pump screens or from pipewrok less far upstream.
As I took it to mean ppm at the point of interest e.g. in the pylon pipework or adjacent main tank pipework.
I believe they also inferred that concentrations could vary wildly from time to time in the fuel passing through the critical pipework sections, up to possibly 125ppm.
.. without of course re-reading or quoting directly.
unquote
I could well be wrong, but I believe that is more a coment on the problems of measuring water content, rather than anything to do with actual water in the accident aircraft. The report does say it expected a lower than maximum water content because of ice forming at the bottom of the fuel tanks, so that the fuel circulating would have a lesser ppm of water. What the comment MAY imply is that the tests on fuel either for ground supply or in aircraft sampling may need examination.
.
Join Date: May 2006
Location: London
Age: 69
Posts: 237
Likes: 0
Received 0 Likes
on
0 Posts
Having slept on it, I believe the AAIB interim Report no. 2 is rather odd.
If one believes in a total safety (non-commercial) attitude, then three cheers, but I do feel that the NTSB and FAA have "bounced" the proper authority, the AAIB, still that's the real world.
Just a look at the actual recommendations ;
Safety Recommendation 2009-028
It is recommended that Boeing and Rolls-Royce jointly review the aircraft and engine fuel system design for the Boeing 777, powered by Rolls-Royce Trent 800 engines, to develop changes which prevent ice from causing a restriction to the fuel flow at the fuel oil heat exchanger. (to which was added : ‘Boeing and Rolls-Royce have accepted the above recommendation. To mitigate the potential for a future fuel system ice accumulation and release event, to cause a blockage at the inlet to the FOHE, Rolls-Royce have developed a modification to the FOHE. The modification will improve the FOHE’s capability in the event of a fuel system ice release event.’)
Safety Recommendation 2009-029
It is recommended that the Federal Aviation Administration and the European Aviation Safety Agency consider mandating design changes that are introduced as a result of recommendation 2009-028, developed to prevent ice from causing a restriction to the fuel flow at the fuel oil heat exchanger on Boeing 777 aircraft powered by Rolls-Royce Trent 800 engines
Safety Recommendation 2009-030
It is recommended that the Federal Aviation Administration and the European Aviation Safety Agency conduct a study into the feasibility of expanding the use of anti-ice additives in aviation turbine fuel on civil aircraft.
Safety Recommendation 2009-031
It is recommended that the Federal Aviation Administration and the European Aviation Safety Agency jointly conduct research into ice formation in aviation turbine fuels.
Safety Recommendation 2009-032
It is recommended that the Federal Aviation Administration and the European Aviation Safety Agency jointly conduct research into ice accumulation and subsequent release mechanisms within aircraft and engine fuel systems
All very sensible, but the ones that interest me are numbers 31 and 32.
31 is sensible but a can of worms, it is open ended, but very important and likely to be long and expensive.
32 is the one that really worries me. It is non specific and non-urgent. However, having found potentially worrying new fuel/water/ice inter-actions there seems no worry over testing ALL aircraft/engine installations and establishing new rules for design and operation. VERY ODD. How does anyone know whether their aircraft is prone to this problem ?
.
If one believes in a total safety (non-commercial) attitude, then three cheers, but I do feel that the NTSB and FAA have "bounced" the proper authority, the AAIB, still that's the real world.
Just a look at the actual recommendations ;
Safety Recommendation 2009-028
It is recommended that Boeing and Rolls-Royce jointly review the aircraft and engine fuel system design for the Boeing 777, powered by Rolls-Royce Trent 800 engines, to develop changes which prevent ice from causing a restriction to the fuel flow at the fuel oil heat exchanger. (to which was added : ‘Boeing and Rolls-Royce have accepted the above recommendation. To mitigate the potential for a future fuel system ice accumulation and release event, to cause a blockage at the inlet to the FOHE, Rolls-Royce have developed a modification to the FOHE. The modification will improve the FOHE’s capability in the event of a fuel system ice release event.’)
Safety Recommendation 2009-029
It is recommended that the Federal Aviation Administration and the European Aviation Safety Agency consider mandating design changes that are introduced as a result of recommendation 2009-028, developed to prevent ice from causing a restriction to the fuel flow at the fuel oil heat exchanger on Boeing 777 aircraft powered by Rolls-Royce Trent 800 engines
Safety Recommendation 2009-030
It is recommended that the Federal Aviation Administration and the European Aviation Safety Agency conduct a study into the feasibility of expanding the use of anti-ice additives in aviation turbine fuel on civil aircraft.
Safety Recommendation 2009-031
It is recommended that the Federal Aviation Administration and the European Aviation Safety Agency jointly conduct research into ice formation in aviation turbine fuels.
Safety Recommendation 2009-032
It is recommended that the Federal Aviation Administration and the European Aviation Safety Agency jointly conduct research into ice accumulation and subsequent release mechanisms within aircraft and engine fuel systems
All very sensible, but the ones that interest me are numbers 31 and 32.
31 is sensible but a can of worms, it is open ended, but very important and likely to be long and expensive.
32 is the one that really worries me. It is non specific and non-urgent. However, having found potentially worrying new fuel/water/ice inter-actions there seems no worry over testing ALL aircraft/engine installations and establishing new rules for design and operation. VERY ODD. How does anyone know whether their aircraft is prone to this problem ?
.
From the AAIB recent interim report:
And:
It does seem that there is a lot more to learn here that may apply to other types of 777 or even other types of aircraft. It's nice to have a "quick fix" in redesigning the RR FCOC but it may only be fixing part of the problem...
Whilst this is considered to be the most likely cause of the engine roll backs on G‑YMMM, and is consistent with data from the incident to N862DA, it has not been possible, due to limitations in the available recorded data, to totally eliminate the possibility that a fuel restriction, from ice, formed elsewhere in the fuel system which, in addition to an FOHE restriction, contributed to the engine roll backs on G‑YMMM.
Tests carried out by the engine manufacturer demonstrated that fluctuations in the P30 burner pressure, fuel flow and spool speeds, recorded on the FDR and QAR during the engine rollback on G‑YMMM, were generally more closely matched when a restriction was placed in the fuel feed pipe approximately 25 feet or more from the aircraft to strut interface.
Quick question...
Who will actually fund the rectification of the 777/Trents? How many aircraft are affected?
a) Will this be picked up by the airlines?, or
b) Will it be paid for by Boeing as its a system problem (for which the solution resides in the RR engine), or
c) Will it be paid for by RR for all affected Trents on 777?
d) a share between b) and c)?
I assume Trent 800s that are not on 777s are not affected? If so this suggests it is the installation of this engine in a 777 that precipitates the problem - hence its a system issue, not just down to the engine (I assume Boeing are the DA for the complete fuel system).
Thoughts?
PS The research proposed in the post above #31/32 is appropriate - you'd first try and properly understand the issue by studying the basic mechanisms for icing, then you could relate it to current designs. If you just started by analysing current designs, you could end up learning very little and it would take longer to technically solve and create robust solutions.
Who will actually fund the rectification of the 777/Trents? How many aircraft are affected?
a) Will this be picked up by the airlines?, or
b) Will it be paid for by Boeing as its a system problem (for which the solution resides in the RR engine), or
c) Will it be paid for by RR for all affected Trents on 777?
d) a share between b) and c)?
I assume Trent 800s that are not on 777s are not affected? If so this suggests it is the installation of this engine in a 777 that precipitates the problem - hence its a system issue, not just down to the engine (I assume Boeing are the DA for the complete fuel system).
Thoughts?
PS The research proposed in the post above #31/32 is appropriate - you'd first try and properly understand the issue by studying the basic mechanisms for icing, then you could relate it to current designs. If you just started by analysing current designs, you could end up learning very little and it would take longer to technically solve and create robust solutions.
I still don't see any analysis of the following :
1. How can the engine design have been in service for 15 years before such incidents happened. What caused it to work fine on comparable flights until now ?
2. What are the specific aspects of the design that cause this to be a problem, which are not present in engines from other manufacturers, or other designs from the same manufacturer ?
3. Is there any relevance that both aircraft involved in the incidents originated at the same airport, and were quite likely refuelled from the same supply system with the same national fuel spec ?
1. How can the engine design have been in service for 15 years before such incidents happened. What caused it to work fine on comparable flights until now ?
2. What are the specific aspects of the design that cause this to be a problem, which are not present in engines from other manufacturers, or other designs from the same manufacturer ?
3. Is there any relevance that both aircraft involved in the incidents originated at the same airport, and were quite likely refuelled from the same supply system with the same national fuel spec ?
Join Date: Feb 2008
Location: Belgium
Posts: 58
Likes: 0
Received 0 Likes
on
0 Posts
Robust solutions
Originally Posted by AAIB
A solution to the early icing problems was to produce a remedy for the specific problem: fuel heaters and filter bypasses were introduced and the optimum mesh size for the boost pump inlet screens was determined. The USAF, like other military organisations, introduced Fuel System Icing Inhibitor (FSII), which can help to prevent the formation of ice.
Robust solutions ... they are available since the fifties!
The Reverend
Join Date: Oct 1999
Location: Sydney,NSW,Australia
Posts: 2,020
Likes: 0
Received 0 Likes
on
0 Posts
WHBM,
I think you'll find that the BA777 originated from Beijing. Back to the drawing board.
Is there any relevance that both aircraft involved in the incidents originated at the same airport, and were quite likely refuelled from the same supply system with the same national fuel spec ?
Join Date: Oct 2004
Location: Torono
Age: 56
Posts: 150
Likes: 0
Received 0 Likes
on
0 Posts
The issue is the amount of protrusion of the heater matrix tubes above their support plate within the FOHE. These are notoriosly difficult to manufacture and the protrusion height is largely driven by their method of attachment, i.e. brazed joints.
If they protrude above a certain dimension then it is likely that any upstream release of a "snowball" will not pass cleanly through the FOHE and will "stick" or "cling" at the FOHE heater matrix inlet plate and hence restrict fuel flow.
The solution is to provide a bypass within the FOHE, similar to that provided for Fuel Filters, which is where, I believe, RR are heading.
The problem is that the current EASA fuel icing cert requirements do not include testing with fuel at a temperature conducive to "sticky ice", ("Snownballs" or "Sticky Ice" occur in fuel at or around -8°C). However sticky ice does not seem to be an issue if, as above, heater matrix tube protrusion is below a certain value.
ps, according to Today's Telegraph (online) the FOHE is there to cool the fuel................
If they protrude above a certain dimension then it is likely that any upstream release of a "snowball" will not pass cleanly through the FOHE and will "stick" or "cling" at the FOHE heater matrix inlet plate and hence restrict fuel flow.
The solution is to provide a bypass within the FOHE, similar to that provided for Fuel Filters, which is where, I believe, RR are heading.
The problem is that the current EASA fuel icing cert requirements do not include testing with fuel at a temperature conducive to "sticky ice", ("Snownballs" or "Sticky Ice" occur in fuel at or around -8°C). However sticky ice does not seem to be an issue if, as above, heater matrix tube protrusion is below a certain value.
ps, according to Today's Telegraph (online) the FOHE is there to cool the fuel................
Last edited by Dak Man; 13th Mar 2009 at 10:54.
Join Date: Mar 2007
Location: In my head
Posts: 694
Likes: 0
Received 0 Likes
on
0 Posts
Dr Daniel Hoeltgen from EASA
Is this fellow one of our guardians of public safety?
Just heard him talking at length on BBC News. Very sadly for him, because I am sure he considers himself a nice knowledgeable sort of chap, this morning he sounded like a poor example of a spin doctor caught in the beam of someone's headlights, but one paid to spin regardless. NB I said "sounded like".
I think he wanted us to know that an AD was issued long since, which apparently bounds operations in such a way as to keep the gremlins at bay whilst Boeing and RR flush them out.
He also seemed to be wanting us to know that suggestions of grounding were obviously groundless since NTSB and others had not ordered it. I guess that means grounding is off his menu, or we can whistle for it.
I see he talks a lot for EASA (and the following was from an article about Helios but I make no apology for that):
From The International Herald Tribune
By Nicola Clark and Heather Timmons
Wednesday, April 23, 2008:
What proportion of the Trent engine 777 fleet is directly under auspices of EASA?
Just heard him talking at length on BBC News. Very sadly for him, because I am sure he considers himself a nice knowledgeable sort of chap, this morning he sounded like a poor example of a spin doctor caught in the beam of someone's headlights, but one paid to spin regardless. NB I said "sounded like".
I think he wanted us to know that an AD was issued long since, which apparently bounds operations in such a way as to keep the gremlins at bay whilst Boeing and RR flush them out.
He also seemed to be wanting us to know that suggestions of grounding were obviously groundless since NTSB and others had not ordered it. I guess that means grounding is off his menu, or we can whistle for it.
I see he talks a lot for EASA (and the following was from an article about Helios but I make no apology for that):
From The International Herald Tribune
By Nicola Clark and Heather Timmons
Wednesday, April 23, 2008:
Hoeltgen said there had been a number of cases in recent years where either a national regulator or an airline had been found to be not in compliance with EASA directives, though he declined to cite specific examples.
"In these cases, it has been up to the member state authority to design corrective action," he said. "They also have to convince us that this has been done properly."
Out of general interest, was there, or has there now been an EASA directive applying in this case? Would EASA be the authority ultimately responsible for any decision on grounding European airline Trent engined 777s?What proportion of the Trent engine 777 fleet is directly under auspices of EASA?
Guest
Join Date: Nov 1999
Location: In the shadow of R101
Posts: 259
Likes: 0
Received 0 Likes
on
0 Posts
WHBM
In one of the earlier AAIB preliminary or interim reports, it was stated that this aircraft simultaneously flew through abnormally cold air and unlike other aircraft on the route did not descend due to temperature effects *and* it's engines were operated at unusually low fuel flows and unusually gentle step climbs were performed. It seems that these parameters were right at the lower end of many tens of thousands of 777 operational data records.
Further to this a long continuous (or nearly so) descent occurred, so the first time any significant thrust was needed was as the drag rose when the aircraft was configured for landing.
That is likely to explain why the event was, at the time, unique.
In one of the earlier AAIB preliminary or interim reports, it was stated that this aircraft simultaneously flew through abnormally cold air and unlike other aircraft on the route did not descend due to temperature effects *and* it's engines were operated at unusually low fuel flows and unusually gentle step climbs were performed. It seems that these parameters were right at the lower end of many tens of thousands of 777 operational data records.
Further to this a long continuous (or nearly so) descent occurred, so the first time any significant thrust was needed was as the drag rose when the aircraft was configured for landing.
That is likely to explain why the event was, at the time, unique.
Join Date: Jul 2007
Location: Germany
Posts: 556
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by WHBM
I still don't see any analysis of the following :
1. How can the engine design have been in service for 15 years before such incidents happened. What caused it to work fine on comparable flights until now ?
1. How can the engine design have been in service for 15 years before such incidents happened. What caused it to work fine on comparable flights until now ?
1- There have been some previous incidents, but all happened at altitude, as with the Delta flight, and were thought to have been non-events, except for a driftdown. They may also have been wrongly attributed to core-icing or other factors.
2- With ETOPS extensions, extended flights over arctic regions, even in the Northern winter, have increased in recent years, leading to a much higher number of flights with very cold fuel.
2. What are the specific aspects of the design that cause this to be a problem, which are not present in engines from other manufacturers, or other designs from the same manufacturer ?
One of the main design differences is that in the Trent design, the fuel first goes through the low pressure pump (this is not the boost pump or override/jettison pump in the tank, but a mechanically driven engine pump), then through the FOHE, and then through the HP:
LP-Pump -> FOHE -> HP pump
In the GE design, the fuel first goes through the LP and HP pumps, and then through the FOHE:
LP-pump -> HP-pump -> FOHE
The HP pump heats the fuel somewhat, which may be enough to avoid ice accretion.
I'm not certain about the PW design.
Another point may be the structure of the FOHE fuel inlet face, which in the Trent design, as we have seen, has protruding fuel pipe ends, upon which ice may accrete.
Your point 3) has already been answered.
Bernd
Join Date: Sep 2006
Location: UK
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
T800
I assume Trent 800s that are not on 777s are not affected? If so this suggests it is the installation of this engine in a 777 that precipitates the problem - hence its a system issue, not just down to the engine (I assume Boeing are the DA for the complete fuel system).
I thought the T800 was only on the B777 varients?
What proportion of the Trent engine 777 fleet is directly under auspices of EASA?
If the fix is a redesign of an engine certified part than the regulator for the manufacturer (EASA in this case) is the one that sets and approves the limitations and announces them to the world wide authorities to incorporate in maintenance actions. Of course the FAA would accept and announce them simultaneously
If the fix is a redesign of the aircraft plumbing, then it's Boeing and comes under the FAA and EASA would embrace these as well.
Dak Man
Good explanation of what appears to us (out of the direct loop) a plausible explanation of the uniqueness of one installation vs the rest.
Now if only the continued new posters would take note of these kinds of explanations before asking the same questions over and over
The issue is the amount of protrusion of the heater matrix tubes above their support plate within the FOHE. These are notoriosly difficult to manufacture and the protrusion height is largely driven by their method of attachment, i.e. brazed joints.
If they protrude above a certain dimension then it is likely that any upstream release of a "snowball" will not pass cleanly through the FOHE and will "stick" or "cling" at the FOHE heater matrix inlet plate and hence restrict fuel flow.
The solution is to provide a bypass within the FOHE, similar to that provided for Fuel Filters, which is where, I believe, RR are heading.
The problem is that the current EASA fuel icing cert requirements do not include testing with fuel at a temperature conducive to "sticky ice", ("Snownballs" or "Sticky Ice" occur in fuel at or around -8°C). However sticky ice does not seem to be an issue if, as above, heater matrix tube protrusion is below a certain value.
If they protrude above a certain dimension then it is likely that any upstream release of a "snowball" will not pass cleanly through the FOHE and will "stick" or "cling" at the FOHE heater matrix inlet plate and hence restrict fuel flow.
The solution is to provide a bypass within the FOHE, similar to that provided for Fuel Filters, which is where, I believe, RR are heading.
The problem is that the current EASA fuel icing cert requirements do not include testing with fuel at a temperature conducive to "sticky ice", ("Snownballs" or "Sticky Ice" occur in fuel at or around -8°C). However sticky ice does not seem to be an issue if, as above, heater matrix tube protrusion is below a certain value.
Now if only the continued new posters would take note of these kinds of explanations before asking the same questions over and over
Join Date: Nov 2007
Location: Cambridge
Posts: 53
Likes: 0
Received 0 Likes
on
0 Posts
I thought the T800 was only on the B777 varients?
Join Date: Oct 2004
Location: Torono
Age: 56
Posts: 150
Likes: 0
Received 0 Likes
on
0 Posts
If it hadn't been for B777, T800 would have been cancelled, the SIA order saved it.
Also, BA, traditionally a RR customer specified GE90 for it's initial B777 order. This was unashamedly done as part of a deal whereby GE bought BA Engine Overhal Limited (BAEOL) in South Wales, this deal also saved the GE90 from extinction at that time.
Off topic - Sorry
Also, BA, traditionally a RR customer specified GE90 for it's initial B777 order. This was unashamedly done as part of a deal whereby GE bought BA Engine Overhal Limited (BAEOL) in South Wales, this deal also saved the GE90 from extinction at that time.
Off topic - Sorry
Last edited by Dak Man; 13th Mar 2009 at 15:00.
Quote:
I thought the T800 was only on the B777 varients?
I thought the T800 was only on the B777 varients?
Still it could still be argued as a system issue, given the "end-to-end" aspects of this problem.
I'd be interested to know how the fix will be funded. If this was a car with an ABS brake problem then the manufacturer would be doing a "recall" with a free replacement of the defective item at their cost. Is it the same for an aircraft manufacturer? Would Boeing and Rolls have separate contracts with the airlines, or would it all go through Boeing? Some interesting commercial/liability interfaces here.....