777/GE90 Emergency AD
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Well, the FAA are right and truly concerned, hence the emergency airworthiness directive.
Engine rollback is NOT good, at any time, and especially at critical phases of flight.
FADEC.
Touted by many as the bees knees of reliable engine performance.
Software algorithm, my foot.
Give me a proper FLIGHT ENGINEER every darn time.Besides, he get wet on the walkaround when it's raining...
Engine rollback is NOT good, at any time, and especially at critical phases of flight.
FADEC.
Touted by many as the bees knees of reliable engine performance.
Software algorithm, my foot.
Give me a proper FLIGHT ENGINEER every darn time.Besides, he get wet on the walkaround when it's raining...
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Anyway, full power is more fun.
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Yes, I was taught the same thing. I'm ready to stand corrected, but I think you'll find that that relates more to a full rated climb versus a reduced rate climb (to cruise altitude).
It's a very different matter if you're including the takeoff power setting into consideration, particularly on an engine the size of the GE-115B. Take a look at the difference in fuel flow on a TOGA takeoff versus a 72 or even 45 to 50 degree assumed temp takeoff. It's considerable.
But as I said, I stand ready to be corrected by people far more tech savvy than I'll ever be.
It's a very different matter if you're including the takeoff power setting into consideration, particularly on an engine the size of the GE-115B. Take a look at the difference in fuel flow on a TOGA takeoff versus a 72 or even 45 to 50 degree assumed temp takeoff. It's considerable.
But as I said, I stand ready to be corrected by people far more tech savvy than I'll ever be.
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Regarding takeoff/climb power...and enroute fuel consumption
OK, lets look at this a little more closely.
When I first started on the Lockheed TriStar (-200 series, RB.211-524B02 engines), the aircraft were equipped with the first truly successful FMS in airline service, coupled to three ISS units, for navigation.
As is usual with FMS, the takeoff weight (mass for you European folks )
was entered (among other parameters) and the takeoff was calculated using the deepest engine de-rate possible, consistant the the runway analysis chart.
After takeoff, and once climb thrust was set, the FMS was engaged in three modes, LNAV, VNAV, and thrust management. The climb IAS (once above 10,000 feet/FL100) was always...min cost.
The thrust selected for climb by the FMS was always the least, considering the weight and climb rate.
Once the ROC decreased to 650 ft/min for thirty seconds, the FMS selected the next higher climb thrust, and this continued to top of climb.
These selected (auto) modes of thrust for takeoff and climb always, without exception produced the LEAST climb enroute fuel consumption.
Of course, we should not be surprised by all this, after all, LOCKHEED did it FIRST with wide-body aircraft.
Ahhhh...Lockheed, a truly remarkable aeroplane
When I first started on the Lockheed TriStar (-200 series, RB.211-524B02 engines), the aircraft were equipped with the first truly successful FMS in airline service, coupled to three ISS units, for navigation.
As is usual with FMS, the takeoff weight (mass for you European folks
)was entered (among other parameters) and the takeoff was calculated using the deepest engine de-rate possible, consistant the the runway analysis chart.
After takeoff, and once climb thrust was set, the FMS was engaged in three modes, LNAV, VNAV, and thrust management. The climb IAS (once above 10,000 feet/FL100) was always...min cost.
The thrust selected for climb by the FMS was always the least, considering the weight and climb rate.
Once the ROC decreased to 650 ft/min for thirty seconds, the FMS selected the next higher climb thrust, and this continued to top of climb.
These selected (auto) modes of thrust for takeoff and climb always, without exception produced the LEAST climb enroute fuel consumption.
Of course, we should not be surprised by all this, after all, LOCKHEED did it FIRST with wide-body aircraft.
Ahhhh...Lockheed, a truly remarkable aeroplane
Last edited by 411A; 2nd Oct 2006 at 21:44.
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Hmm... anyone bother to read the document? They're running "version A.0.4.5" of the FADEC controller software.
In PC speak, that's an alpha version... No wonder there are stuffups! Microsoft can't even get it right after version 5. ha!
Jokes aside, 411: take off weight/mass is not about european or not, it's about the *physically* correct term. takeoff weight is a useless quantity, as, physically speaking, the weight depends on the gravitational field you're in at the moment. So what you really mean is mass.
Cheers!
In PC speak, that's an alpha version... No wonder there are stuffups! Microsoft can't even get it right after version 5. ha!
Jokes aside, 411: take off weight/mass is not about european or not, it's about the *physically* correct term. takeoff weight is a useless quantity, as, physically speaking, the weight depends on the gravitational field you're in at the moment. So what you really mean is mass.
Cheers!
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Mass is for those so inclined, European style
Ah, not really, weight is more appropriate.
At the top of my chart it says...weight and balance/trim chart.
As it should be...!
At the top of my chart it says...weight and balance/trim chart.
As it should be...!
411A;
Re, "Give me a proper FLIGHT ENGINEER every darn time."
Agree, and given an AD that says,
"Unsafe Condition
(d) This AD results from a report of two occurrences of engine thrust rollback during takeoff. The Federal Aviation Administration is issuing this AD to prevent dual-engine thrust rollback, which could result in the airplane failing to lift off before reaching the end of the runway or failing to clear obstacles below the takeoff flight path.",
what shall we do with the software "engineer" who wrote the code?... A scene from Python's Holy Grail comes to mind...
Re "Ahhhh...Lockheed, a truly remarkable aeroplane"
Again agree...finest airplane I have ever flown. Your description of the FMS/Autopilot/Autothrust system brought back fond memories.
Re, "Give me a proper FLIGHT ENGINEER every darn time."
Agree, and given an AD that says,
"Unsafe Condition
(d) This AD results from a report of two occurrences of engine thrust rollback during takeoff. The Federal Aviation Administration is issuing this AD to prevent dual-engine thrust rollback, which could result in the airplane failing to lift off before reaching the end of the runway or failing to clear obstacles below the takeoff flight path.",
what shall we do with the software "engineer" who wrote the code?... A scene from Python's Holy Grail comes to mind...
Re "Ahhhh...Lockheed, a truly remarkable aeroplane"
Again agree...finest airplane I have ever flown. Your description of the FMS/Autopilot/Autothrust system brought back fond memories.
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Sounds like these rollback's must have produced some "fun" takoffs. I fly with four fires on the wings, so any ETOPS crews out there; How does this fit into the stringent certification guidelines? I would assume that most GE-90s are being used on some seriously long ETOPS since they are on an aircraft with some pretty long legs.
I especially like this part of the AD...
"A dual-engine thrust rollback, if not corrected, could result in the airplane failing to lift off before reaching the end of the runway or failing to clear obstacles below the takeoff flight path."
Really?? I guess they should also state that if you have a dual-engine thrust rollback you might need to land at the nearest airport because you might not be able to glide to your destination (depending on height of course).
Gotta love those geniuses at the FAA...
I especially like this part of the AD...
"A dual-engine thrust rollback, if not corrected, could result in the airplane failing to lift off before reaching the end of the runway or failing to clear obstacles below the takeoff flight path."
Really?? I guess they should also state that if you have a dual-engine thrust rollback you might need to land at the nearest airport because you might not be able to glide to your destination (depending on height of course).
Gotta love those geniuses at the FAA...
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I am amazed that the FAA allow an aircraft with a defect that reduces engine power by up to 33% on takeoff would be considered serviceable. Surely an engine with FADEC version A.0.4.5 installed has a defect that cannot be cleared and is therefore unservicable.
But then the FAA is an American organisation looking after American interests and they cannot have a Boeing with GE engines grounded could they?
But then the FAA is an American organisation looking after American interests and they cannot have a Boeing with GE engines grounded could they?
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I am amazed that the FAA allow an aircraft with a defect that reduces engine power by up to 33% on takeoff
thrust level on the affected engine progressively dropped resulting in a thrust loss of 65 to 77 %
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I had read and understood that the potential fault is likely only at an hieght of less than 400 feet, therefore during take-off and not in climb mode.
"In both cases, the engine recovered to the proper N1 thrust level as the airplane climbed beyond 400 feet above ground level."
Have I misunderstood the EAD?
"In both cases, the engine recovered to the proper N1 thrust level as the airplane climbed beyond 400 feet above ground level."
Have I misunderstood the EAD?
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Indeed so: Mass denotes how much matter an object has whereas weight is a measure of how strongly gravity pulls on that matter. If we were to fly our 777 to the moon (ha ha, but anyway) then the weight would decrease as the effect of gravity would reduce whereas the mass (the amount of matter that the a/c is comprised of) would remain the same (fuel burn aside).