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View Full Version : cfm-56-7b24k giving power 26k on go around


saurabh
8th Jun 2006, 11:11
I want to know that whether b737-800 fitted with cfm-56-7b 24k can provide 26 k power on a go around? :rolleyes:

IFixPlanes
8th Jun 2006, 13:21
No, when Engine Identification Plug says 24k you canīt go beyond this trust without reprogramming the Plug.

RYR-738-JOCKEY
8th Jun 2006, 18:27
The answer is simply no, but the engine would with a small alteration produce up to 27k. CFM-56-7B is capable of up to 27k. Most operators use 26k, for costcutting purposes, or even 24k as you mention.

IFixPlanes
8th Jun 2006, 18:38
...or even 24k as you mention.
... or less:
http://img518.imageshack.us/img518/9840/cfm567b5yd.th.jpg (http://img518.imageshack.us/my.php?image=cfm567b5yd.jpg)

RYR-738-JOCKEY
8th Jun 2006, 19:16
Excactly...24, 26 or 27k for that type and model of eng.

rudderless1
17th Jun 2006, 12:06
saurabh, you are correct the 800's with the 24k have this abilityon the QF fleet.It was mentioned during my engine course.:ok:

BAe 146-100
18th Jun 2006, 00:12
Is that table correct cause I'm sure there is a 22K option available on the B737-800. :confused:

Ryanair seem to drop down to it on takeoff when possible.

BAe 146

IFixPlanes
18th Jun 2006, 05:50
...
Ryanair seem to drop down to it on takeoff when possible.
Sorry, but what do you mean with this?

captjns
18th Jun 2006, 08:53
Is that table correct cause I'm sure there is a 22K option available on the B737-800. :confused:

Ryanair seem to drop down to it on takeoff when possible.

BAe 146

It appears what you are referring to is de-rating thrust. Lets forget the 27k bump option. The engine is fully rated at 26k of thrust. The crew has the option of selecting 26k, 24k, or 22k via the FMC. From the selected rated, or de-rated thrust, if 24k or 22k are selected, an assumed temperature can be selected via the FMC either full 26k, or de-rated 24k, or 22k are not required. The second trust reduction is referred to as double de-rate.

IFixPlanes
18th Jun 2006, 10:20
We are talking about the maximum Thrust an Engine can give, right?
The mounted Engine is controlled by the Ratingplug belonging to the Engine.
You can see the Rating on the Nameplate:
http://img205.imageshack.us/img205/3003/nameplatecfm567b4qu.th.jpg (http://img205.imageshack.us/my.php?image=nameplatecfm567b4qu.jpg)
You can do a thrust limitation via FMC, but you can not go above the Thrust programmed by the Ratingplug and written down on the Nameplate.

captjns
18th Jun 2006, 14:53
You can do a thrust limitation via FMC, but you can not go above the Thrust programmed by the Ratingplug and written down on the Nameplate.

Without going into the complexities, on some 737-800s you can imput a derated thrust setting from 26k to 24k or 22k, and further reduce that derated thrust using an assumed temperature... thus the term double de-rate. If you have friend that flies the -800 with this feature, grab his FCOM. The determining factor in which derated thrust setting depends on the ATOGW.

IFixPlanes
18th Jun 2006, 15:09
I think that we dont speak over the same thing.
If you have a 737-800 with an 24k engine mounted you can not get 26k without reprogramming
the Ratingplug .
Sorry, but i dont need an FCOM. I use the AMM.
If you have friend that repaires the -800 ask him about AMM. ;-)

sets
18th Jun 2006, 16:48
It is possible to get 26k on an 737-800 with a 24k plug. Its not a widely known fact.

IFixPlanes
18th Jun 2006, 16:53
It is possible to get 26k on an NG with a 24k plug. Its not a widely known fact.
Would you introduce me into this secret?

sets
18th Jun 2006, 17:46
Its called Emergency Reserve Thrust. On each minor model of the 737NG you will get the next highest certified thrust rating for that model/engine combination if you firewall the levers. So on a 737-800 with a 24k plug you get 26k. There are altitude and airspeed restrictions to limit this to the takeoff/go-around regime. It should be noted that if there is no higher certified rating for that model/eng combination you do not get any extra. So on a 737-600 with 22k plugs thats all you are going to get. A little something extra from Mr. Boeing to take care of Mom and kids.

IFixPlanes
18th Jun 2006, 19:40
Damn, i hate this. When this is true, i must get some more infos about it.
I donīt like surprises like this when i do a high power test run on ground.

sets
19th Jun 2006, 00:24
Remember its only if you firewall the lever. If you set Takeoff or G/A thrust using the normal procedures (set to the green bug) you get the rating plug thrust. This emergency thrust is where you push the thottles all the way to the forward stop.

luckyirishlad
19th Jun 2006, 00:26
Theres a long and short answer really!

Practical terms in most airlines....NO
Theoretically...........................Yes

thrust is limited by pin configs. FADEC can be set in such a way that they provide 24k in take off power, but, when the pilot pushed beyond takeoff power, into the "cushion" range during an emergency, the FADEC will allow the engine to churn out out the 26 or 27k The max available again depends on what the frame can safely handle.

captjns
19th Jun 2006, 08:16
Theres a long and short answer really!

Practical terms in most airlines....NO
Theoretically...........................Yes

thrust is limited by pin configs. FADEC can be set in such a way that they provide 24k in take off power, but, when the pilot pushed beyond takeoff power, into the "cushion" range during an emergency, the FADEC will allow the engine to churn out out the 26 or 27k The max available again depends on what the frame can safely handle.

Hopefully this will add clarity to the mystery of the EEC

EEC Normal Mode

In the normal mode, the EEC uses sensed flight conditions and bleed air demand to calculate N1 thrust ratings. The EEC compares commanded N1 to actual N1 and adjusts fuel flow to achieve the commanded N1. The full rated takeoff thrust for the installed engine is available at a thrust lever position less than the forward stop. Fixed or assumed temperature derated takeoff thrust ratings are set at thrust lever positions less than full rated takeoff. The maximum rated thrust is available at the forward stop. The EEC limits the maximum thrust according to the airplane model as follows:

• 737-800 – CFM56-7B27 rating

Takeoff Bump Thrust - Specific Aircraft Only

Takeoff bump thrust is available when increased thrust is needed for takeoff, above the normal maximum takeoff thrust setting. When selected using the FMC N1 LIMIT page, takeoff thrust is increased by either the flight crew or the autothrottle positioning the thrust levers to set N1 to the reference N1 bug. Bump thrust applies only to the takeoff rating; maximum climb, maximum continuous and go-around thrust ratings are not affected.

Dookie on Drums
20th Jun 2006, 04:44
Is this something that you can plan to use on lets say a limiting runway?

Would a BLT analysis offer a "bump" rating or is this purely a get out of jail card to use when the end of the runway is coming awfully close? :eek:

TyneQNH
20th Jun 2006, 22:31
So, if I've got this correctly it's suggested that a 737-700 with engines rated for 22k should give 24k if the thrust levers are pushed to the forward stop.

Can someone point me to a reference for this in the aircraft manuals please.

Many Thanks

TyneQNH

Dehavillanddriver
21st Jun 2006, 00:41
For a 737-700 with any thrust rating available (the max you can buy for a -700 is 24k) when you push the thrust levers fully forward you get 24k

for a 737-800 with any available thrust rating when you push the levers fully forward you get 27k.

The reference to this is in the FCOM vol 2 (from memory)

I'll look up the page references later and edit the post....