CLB 1, CLB 2 derates above 15000 ft

[Hardy Heinlin]

Good morning,

some manuals say the CLB 1 and CLB 2 derates disappear gradually with the rising aircraft altitude when climbing through the 10000-15000 block; at 15000 the derate is completely removed, and there are no differences anymore between
CLB 1, CLB 2, and CLB.

This gradual removal is implemented in PSX for all engine models.

However, a complete removal should possibly not be applied to the RR model. Does anybody know how much derate should remain on the RR when above 15000 ft?


Cheers,

|-|ardy

[Jeroen D]

Why would some derate remain for the RR engines? Any thoughts to the reason to do so?
Jeroen

[Jeroen Hoppenbrouwers]

They're British.

[Britjet]

Hi Hardy and Happy New Year!

I cannot be specific but I do know that the climb derates continue to all levels.
They are used fairly routinely to lessen the pitch change in the climb for passenger comfort.
Basically you select the climb and then override the CLB reference on the THR LIM page.
You get about .03 to .05 EPR (CLB1 or CLB2) less with the respective derate, as far as I can remember.
Sorry I can't be more accurate. My memory is getting hazy!

Regards,

Brit
(as in LOL)

[Hardy Heinlin]

Hi Brit :-)

I just rechecked my Cargolux AOM; it usually explains RR features and GE features separately (Cargolux have two engine models in their fleet). Regarding the CLB derate stuff, it describes it like I did above, for both engine models. So I assume it's rather a BA airline option than an RR standard feature.


Cheers,

|-|ardy

[Vnav]

Hi

If you are looking for more information on the subject, there's a RR paper available at this location: http://www.smartcockpit.com/download.php?path=docs/&file=Derated_Climb_Performance.pdf

GE also produced a paper about climb derate some years ago.

It presents the different kinds of climb derates available (CLB, CLB1, CLB2, fast or slow taper) and their impact.

I don't know for the 744, but for the 777/787, the choice of a fast or slow taper is an airline option.

Regards,
Vnav

[Hardy Heinlin]

Hi, thanks for the tip.

So I guess BA's 744 fleet has this slow washout that ends at 30000 instead of 15000.

Does this make sense, Brit?

All versions seem to start the washout at 10000. On the 744 the washout normally ends at 15000 (on the 777 normally at 12000).


Cheers,

|-|ardy


The paper is slightly inconsistent, isn't it?

Page 6.4:
CLB 1 with washout to 30000 is called "fast taper".
CLB 2 with washout to 30000 is called "slow taper".

Page 6.10:
CLB 1 & 2 fast washout is called "fast taper".
CLB 1 & 2 slow washout is called "slow taper".

[Will]

Another option in the preferences section...?

:-)

[Britjet]

Hi Hardy.

That makes sense, yes, although I think it worked above 30,000, because that's where we used it on the majority of occasions.

Brit

[jonb]

I think this is another company option for the airframe rather than the engine type, as some of our fleet have the earlier climb derate washout and some the later version, but they are all GE powered aircraft. I hope that helps.
Jon

[Jeroen Hoppenbrouwers]

Also it is not impossible that the washout only works for as long as the derate is active, i.e., once you switch out of CLB to another mode, it may simply be reset and start over.  It would pose interesting questions on an intermediate climb leveloff, though, so it isn't straightforward. But never underestimate "smart" software and the tricks it can pull.


Hoppie

[Hardy Heinlin]

Hi Brit & Jon,

would you be able to check if your washout altitude is raised to an altitude above 30000 (e.g 45000) or if there is no washout at all?

I will add an option to the Model > Programming page. I need to know whether the option should be selected by a simple checkbox, or a set of radio buttons, or an edit field for an altitude entry ("0" would mean "no washout").


Cheers,

|-|ardy


Edit: I think I'll just add an edit field, to be on the safe flexible side.

[jonb]

Hi Hardy,
Having just checked the manuals the newer portion of the fleet which were originally specked by Alitalia start to washout the derate at 10,000 until it is fully removed at 15,000.
The remainder of the fleet start to remove CLB1 at 10000 until it is removed at 30000, however CLB 2 starts the same at 10000 but  isn't  fully removed until 35000.
Cheers

Jon

[Hardy Heinlin]

Great. Thanks, Jon!

You've got 747-400s from Alitalia?


Cheers,

|-|ardy

[jonb]

They were Boeing whitetails that had originally been ordered by Alitalia but they cancelled the order so we bought them. They have an extra far reclining pilot seat to accomodate Italian style afternoon siestas !

[Britjet]

Sorry Hardy, I don't have any written info on that.
Brit

[G-CIVA]

Hardy,

Could this be what you are looking for?:

(B747 FCOM Vol 2 Flight Management, Navigation - Flight Management Computer)

Derated Thrust Climb

During climb, CLB 1 and CLB 2 derates are gradually removed. In cruise, the
thrust reference defaults to CLB or CRZ as set by maintenance.

G-BNLA - G-BNLZ, G-CIVA - G-CIVP

Two fixed climb thrust derates can be selected on the THRUST LIM page. CLB 1
uses a 10% derate of CLB thrust to 10,000 feet, then increases thrust linearly with
altitude to CLB thrust at 15,000 feet. CLB 2 uses a 20% derate of CLB thrust to
10,000 feet, then increases thrust linearly with altitude to CLB thrust at 15,000
feet.

G-BYGA - G-BYGG, G-CIVR - G-CIVZ

Two fixed climb thrust derates can be selected on the THRUST LIM page. CLB 1
uses a 10% derate of CLB thrust to 25,000 feet, then increases thrust linearly with
altitude to CLB thrust at 35,000 feet. CLB 2 uses a 20% derate of CLB thrust to
25,000 feet, then increases thrust linearly with altitude to 5.5% derate at 35,000
feet.

Use of an assumed temperature reduced thrust takeoff or takeoff derate affects
automatic selection of climb derate. For a thrust reduction less than 5 percent, maximum climb thrust is selected by the FMC. For takeoff thrust reductions or derates from 5 percent to less than 15 percent, CLB 1 is selected. CLB 2 is selected for all takeoff thrust reductions or derates equal to or greater than 15 percent.  On the ground, the pilots may override the automatic climb derate selection after the
takeoff selection is complete.

Cheers

Steve B

[Hardy Heinlin]

It is, indeed :-)

Thank you, Steve!


Cheers,

|-|ardy

[Hardy Heinlin]

Can somebody, or Jon, tell me whether among the Virgin aircraft G-VAST, G-VFAB, and G-VROC is an "Alitalia" type, and if so, which one?

[G-CIVA]

Hardy,

This is the same reference as I quoted for BAW but for VIR - vintage late 06 ... things might have changed - I don't have access to the AFM for the specific info on derate percentages I hope it helps ... without stepping on Jon's shoes    

Reduced Thrust Takeoff

Reduced thrust takeoffs lower EGT and extend engine life.

Derate/Variable Takeoff Rating

G-VGAL, G-VLIP, G-VROC, G-VROM, G-VROS, G-VROY, G-VWOW, G-VXLG

Two fixed derates, TO1 and TO2, can be selected on the THRUST LIM page.

G-VAST, G-VBIG, G-VFAB, G-VHOT, G-VTOP

Two fixed derates, TO1 and TO2, can be selected on the THRUST LIM page. TO1
and TO2 reduce takeoff thrust by percentages specified by the operator [Airline
Selectable Option]. The derate percentages can be set between maximum takeoff
thrust and the maximum certified derate in one percent increments. The Airplane
Flight Manual (AFM) provides performance data for these derates.

With both TO1 and TO2, the thrust setting parameter is considered a limitation for
takeoff; therefore, thrust levers should not be advanced further except in an
emergency. A further thrust increase following an engine failure could result in a
loss of directional control. Use the takeoff speeds calculated by the FMC for the
selected derate or variable takeoff rating condition.

Assumed Temperature Thrust Reduction Takeoff

Entering an assumed temperature higher than the actual temperature reduces
takeoff thrust.

The maximum thrust reduction authorized is 25 percent below any certified rating.
The assumed temperature thrust setting is not considered a limitation. The
assumed temperature reduction can be removed. If conditions are encountered
where more thrust is necessary, the crew can manually apply full thrust.

Derated Thrust Climb

During climb, CLB 1 and CLB 2 derates are gradually removed. In cruise, the thrust reference defaults to CLB or CRZ as set by maintenance.

G-VGAL, G-VLIP, G-VROC, G-VROM, G-VROS, G-VROY, G-VWOW, G-VXLG

Two fixed climb thrust derates can be selected on the THRUST LIM page. CLB 1
uses a 10% derate of CLB thrust to 10,000 feet, then increases thrust linearly with
altitude to CLB thrust at 15,000 feet. CLB 2 uses a 20% derate of CLB thrust to
10,000 feet, then increases thrust linearly with altitude to CLB thrust at 15,000
feet.

G-VAST, G-VBIG, G-VFAB, G-VHOT, G-VTOP

Two fixed climb thrust derates can be selected on the THRUST LIM page. CLB 1
uses a 10% derate of CLB thrust to 10,000 feet, then increases thrust linearly with
altitude to CLB thrust at 30,000 feet. CLB 2 uses a 20% derate of CLB thrust to
10,000 feet, then increases thrust linearly with altitude to CLB thrust at 35,000
feet.

Use of an assumed temperature reduced thrust takeoff or takeoff derate affects
automatic selection of climb derate. For a thrust reduction less than 5 percent,
maximum climb thrust is selected by the FMC. For takeoff thrust reductions or
derates from 5 percent to less than 15 percent, CLB 1 is selected. CLB 2 is selected
for all takeoff thrust reductions or derates equal to or greater than 15 percent.On
the ground, the pilots may override the automatic climb derate selection after the
takeoff selection is complete.

Best

Steve