777/GE90 Emergency AD
 

New Emergency AD http://www.airweb.faa.gov/Regulatory...C?OpenDocument

... scary... :uhoh:

J.V.

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...:}

Breath of fresh air Mr. 411A as are many of your posts.

JV, not "scary", just a sensible precaution until the prob is fixed. Anyway, full power is more fun!

Have to agree with those sentiments. Just returned from a flight with a 330 tonne takeoff weight. At TOGA power, the beast fair leapt into the air - but the fuel burn was way higher than planned, obviously because of the TOGA takeoff. This might be something that will have to be allowed for until this glitch is fixed.

I was always taught that the lowest fuel consumption to top of climb was that achieved by a rated takeoff (NOT a reduced one) ?

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.

Check that link!

Correct link is at: http://www.airweb.faa.gov/Regulatory...D?OpenDocument

4HP

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

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!

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...!:}

ah Lockheed


some of the most beautiful planes ever built.


original electra/hudson bomber

P38

p80

L1011

Constellation


and all those skunk work planes

To be nitpicking, mass is the correct term, but the chart says weight...

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.

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... :rolleyes:

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?

A touch more than that I fear .....

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?

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).

Shades of previous GE90 'rollback' and IFSD from the early days :hmm: Only difference was in those cases it was in cruise and was caused by moisture freezing in the P3B and PS3 lines to the FADEC...........solved by increasing the tubing diameters:8
Firewalled the T/L's maybe;)

I bet those 777 guys and gals out there will be having a great time unleashing the power in those '90's! Especially at the lower weights! YEE- HA :ok: :E

Fun... I don't know the 777 at all, but reading about the problem gives me a small dose of the willies I'll admit. Wonder if there have been any problems with noise abatement procedures? I know the issue is supposed to go away past 400', but with this kind of problem sniffing at my heels I'd not only go in TOGA, I'd bloody well leave the power alone on climbout until *I* was comfortable, and stuff the NIMBYs...

R1

[quote=Ranger One;2888630]Fun... . Wonder if there have been any problems with noise abatement procedures?

As this rule is implemented by an AD,based on safety, it would take precidence over any local restrictions. I have no doubt that all the operators concerned would have let the airport authorities, also affected, know about the situation. Therefore common sence suggests that a relaxation would be imposed on the 777-200LR and 777-300ER's . However, that is based on the assumtion that the airports also use common sence and logical thought. mmmm.

Symptom
 

No, you have understood it well. The thrust rollback occured only in takeoff mode below 400ft AGL. The autothrottle restored thrust at 400ft AGL. Hence the AD rule to use only full rated thrust for now.

To add: TOGA thrust settings are still order of the day on ALL GE90115B equipped aircraft, that being the B773 ER only, until GE comes up with a revised/improved software for the FADEC(so they say).
This anomoly apparently can only, & has only(twice) occurred during derated T.O. thrust settings, which to date have almost always been the case(other than wet weather, adverse effects or just the will to feel what they can do), due the immense thrust these BRT's can deliver!

Apparently at TOGA setting, the calculation matrix of the selected de-rated thrust desired, in the FADEC, is by-passed, preventing this from occurring again until a proven SW replacement is issued.

As far as noise abatement goes... I marvel daily, at the incredible "silent power" these machines deliver @ full rated thrust!
There is still no noise, other than the vibration of the nearby earth.
All one can hear is the N1 spin up then it all goes quiet as the monster launches itself like a short sectored B767 -200 PW4060.

Very Impressive, to put it mildly!
Although, I dont want to comment on what it is doing for the life of these engines???
I think GE are going to cough big time, if a fix does not appear SOON.:ok:

The 777 is a great aeroplane...It is only missing 2 things...

An additional engine under each wing! :E

I just found out I'll be flying (as PAX) on UAE412 (B773) tomorrow from SYD to DXB. Anybody know whether those are affected?

UAE 412 will be A345 so sadly you will miss the ride of a lifetime.

......
 

actually weight is the correct term. w=mg, therefore implicit in the term weight, gravity AND mass are taken into consideration. Mass, strictly defined is m=w/g........and I assume this is not what we're looking for when calculating our take-off weights :)

UPDATE: All may be pleased to hear, or re-assured now that the latest arrivals to EK's B773ER fleet EBU & EBV,(yes that's 22) have the new version of software loaded in the fadec for reduced thrust take off calculation, & mandatory TOGA take offs are no longer required.:)

That is an excellent discovery.

Another topic here, but an entirely different sort of 4-engine rollback, and known about for many years, caused by a synchrophaser malfunction cost the lives of almost an entire C-130 crew in the 90s.
The call-sign was King 56, and they had departed Portland, OR.

Read up on what John Nance and others said about many amateurish, botched Air Force safety investigations.

What a senseless tragedy that the Air Force could have modified the systems many years ago. Never mind the need to retrofit standby ADIs.
"4-engine rollback": "wweek.com".

Wednesday evening I am SLF on the Eva air LHR-BKK flight, I beieve that their 777s have the GE90-115:eek:
I flew the same route a month ago and no problems either way:ok:

As an average passenger, one wouldnt know any difference, other than exceptional acceleration & a mean initial climb rate on short to medium sectors.
As mentioned before, these engines before the rollback incident were almost always taking off at reduced take off thrust levels, for fuel saving & engine life purposes! One just doesnt need the power which is on tap, for NORMAL everyday operations.
To date, my experience with the new GE115B(that is 115000 lbs of capable thrust, by the way) has been very good & reliable unlike the teething problems encountered with the 94B!

Couple of regular service bleed problems & naturally engine cowling; opening & closing problems, simply due to its shear size, weight & 14 cowl latches; but no engine problems, besides this Fadec software issue.

I believe Etihad report having had 2 engines with vibration problems, requiring removal?
If so please share the knowledge;) .