B777ER / GE115B Engines

[160knots]

Coluld somebody please explain how the bump works on this engine and what the relationship is to To, TO1 and Rated Thrust.

Thanks

160

[gas path]

Thrust bump. It's a modified FADEC software which will give an extra 'couple of percent' available thrust for the hot and/or high airfield. It uses IIRC a different assumed temperature. Entered via the CDU the FADEC takes care of the rest. It shortens the engine life and costs a lot of dosh if you're on power by the hour.
Only available whilst the engine has a reasonable EGT margin.
I think that about sums it up!

[electricdeathjet]

Does that mean you get a couple percent extra on top of the 115lbs thrust?

[gas path]

Engine Model . Max Cont.(S/L). . . . .Max T/Off (5 min)
GE90-76B. . . 75,430 lbs . . . . . . . . .81,070 lbs
GE90-77B . . .75,430 lbs . . . . . . . . .81,700 lbs
GE90-85B . . .81,230 lbs . . . . . . . . .88,870 lbs
GE90-90B . . .90,580 lbs . . . . . . . . .94,000 lbs
GE90-94B . . .90,580 lbs . . . . . . . . .97,300 lbs
GE90-110B . . 110,000 lbs . . . . . . . 110,760 lbs
GE90-113B . . 110,000 lbs . . . . . . . 113,530 lbs
GE90-115B . . 110,000 lbs . . . . . . . 115,540 lbs

The thrust bump is 2.5% at upto +42c

[electricdeathjet]

Yeah great, but do the TOGA figs. include Bump?

[160knots]

gas path

Thanks for the info but how does it compare to TO? Is the flat rated thrust maintained at a higher OAT with bump? as compared to the flat rating without bump? There seems to be very little info put out by Boeing in it's manuals

[gas path]

The 'normal' T.O thrust would be the n1 target displayed for the existing OAT. The derates applied assume the higher temperature as inputted into the CDU.
I think?? the 'bump' is a separate input that ignores the existing OAT. Maybe someone who uses it everyday could explain better?

[FullWings]

I don't know what happens internally, but the upshot of selecting a 'bump' through the FMC is that you go up an engine size . As we use datalink performance, I'd think that the assumed temps, etc. take account of the "new! improved!" thrust rating. It seems to be an airfield-specific thing, too.

[gas path]

It seems to be an airfield-specific thing, too.

Like Denver

[oz in dxb]

The 777 FCOM doesn't give too much away in regards of takeoff bump.
Takeoff bump is a thrust reference mode which allows additional takeoff thrust when the aircraft is operated in the following envelope.
Pressure altitude -2000ft to 3000ft. Ambient temperature 32 to 53C.

Even though takeoff bump hasn't been selected but you are in the above envelope, pushing the thrust levers to max will put you into the takeoff bump increased thrust.

We only use takeoff bump after other methods have failed to produce the required TOW.
Pack off takeoff, APU to L pack takeoff.

On our Boeing fleet we don't use derated thrust for takeoff.

Oz

[TopTup]

Good info on the "bump".

What about the "L" in the GE90-115 B1L1?

Also, is there any significance to the "1" in both terms? Probably just a serial number I am guesing, but can't find out for sure. Have searched many times for some info, and like 160 kts says, very little on the bump from GE and Boeing FCOMs; same about the "L" term.

[160knots]

gas path

The 2.5% increase in thrust is that above the:
1.TO value or above
2. a margin over Rated Thrust.?? or
3. 2.5% above TO and packs off Take- Off.

[gas path]

My understanding is that the 'bump' is used when the basic maximum takeoff thrust does not provide the required T.O performance.
There is no intermediate thrust between the basic maximum takeoff thrust and the 'bump'. So if the calculation were for what is nominally full power (for that airfield and temp). The 'bump' will give the extra thrust by a rescheduled increase in fuel and corresponding increase in n1 speed. (thrust!)

TopTup. The B1L1 will refer to a certain change(s) (over original) spec. Possibly an engine could come as for instance a -115b and after overhaul or modification the part number effectively changes to reflect those changes.

[sidestick stirrer]

My simulator instructor mentioned, during my recently-completed transition onto the -115-powered B77, that the "L" designation meant that the EEC logic had been changed and included something called a "Lock" into its programming.

[TopTup]

Thanks.... Like AIMS I v AIMS II for the EEC??

What is it "Locking"? Am I correct to assume it is locking the baromteric parameters (as at 100 kts when the FMC does) in order to give the data for the amount of "bump" to provide?

[BuzzBox]

Oz:

On our Boeing fleet we don't use derated thrust for takeoff.

Just curious - how come you don't use derated thrust????

[shakealeg]

He is talking about derate vs assumed temperature method. We use assumed temperature method.

[BuzzBox]

Thanks - we use a combination of both. Depending on the required performance the thrust could be TO, TO1, TO2, TO with an assumed temp, TO1 with an assumed temp, or TO2 with an assumed temp. Do you not do the same?