CLB 1, CLB 2 derates above 15000 ft

[Hardy Heinlin]

Thanks again, Steve.

So G-VROC is it.


Cheers,

|-|ardy

[G-CIVA]

Always a pleasure Hardy ... thing is with the 744 one never stops learning ... this is something I have never really looked closely at before.

Best

Steve

[jonb]

Yes, it's amazing what nuggets of information you pick up on simulator forums, always an education. Personally I won't go near "real world" aviation forums, too many arrogant characters.
G-VROC is my favourite , well second favourite behind G-VFAB
Cheers
Jon

[Hardy Heinlin]

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.

My washout target values are always 0%. Otherwise, this would require yet another two optional parameters. My option pages are full now :-)

To get that 5.5% at FL350, I simply set the washout end to FL388 at which it's 0%. This is probably even the case on the real versions of these aircraft; I think above FL350 it won't remain at 5.5%. This quoted text might just describe a graph that is cropped at the FL350 edge.


Regards,

|-|ardy

[Hardy Heinlin]

The washout altitudes for the above mentioned BA and Virgin models are now stored in the new model files which can be downloaded here:

http://aerowinx.com/forum/topic.php?id=2566

[Britjet]

Thanks, Hardy..
Peter.

[G-CIVA]

The washout altitudes for the above mentioned BA and Virgin models are now stored in the new model files which can be downloaded here:

http://aerowinx.com/forum/topic.php?id=2566

Thanks Hardy.

[Hardy Heinlin]

Note: The last post above is from 2015. Now it's 2019.

Another question, 4 years later ...

I've observed the EICAS "CLB1" (or "CLB2") label changes to "CLB" when the washout is 100% done. PSX models this visual EICAS effect since 2015.

But I don't know what happens on the real FMC THRUST REF page at that moment. Two assumptions:

(A) The <SEL> marker stays at CLB1 (or CLB2)
(B) The <SEL> marker jumps to CLB

In PSX it's (A).

Perhaps it should be (B), and that may be the reason why the EICAS also changes to "CLB".

If (B) is true, and when the washout is done, the pilot may directly reselect CLB1 (or CLB2) without first reselecting CLB.

However, whether a post-washout derate-reselection makes sense is a different question. The <SEL> label may move as desired and the EICAS label may change accordingly, but will the previously washed-out derate be available again? E.g. will a CLB2 reselection at FL350 provide a -20% derate again? And if so, when will that wash out? At FL400? Or never?

Some aircraft have a washout phase that only ends at altitudes way above 30000 ft. When cruising at FL250, and then changing from CRZ to CLB for a step climb, and manually selecting CLB2, you will see the CLB2 label and derated values. In real life, when you do this on an aircraft whose derate was washed out at FL150 already, you will also see the CLB2 label probably, but I doubt that you will get derated values. It may look like it due to the CLB2 label on the EICAS, but the actual thrust limit is probably equal to the CLB thrust limit since the aircraft is above the washout top altitude. I don't think a reselection at any altitude will restart with a reset washout. The aircraft specific washout altitudes mentioned in the manuals seem to be absolute, not relative altitudes.


Regards,

|-|ardy

[andmiz]

I've also seen that on the EICAS, when the washout is complete it still remains in CLB 1 or CLB 2.  I'll have a look in a few days when I'm back in a -400.  I'd suspect that the FMC selected indication shows the same.

For interest our ERF 4062's have CLB 1 up to 30,000 and CLB 2 up to 35,000

[Hardy Heinlin]

Thank you for your comment.

I've also seen that on the EICAS, when the washout is complete it still remains in CLB 1 or CLB 2.

How do you know when the washout is complete? Do you refer to the aircraft specific notes in your manual, or do you manually reselect CLB to see if the normal thrust limit is now equal to the derated limit?


|-|ardy

[andmiz]

The later method would indicate that the washout is complete.  (Our aircraft operating manual also lists the derate completion altitudes)

[andmiz]

I have emailed you some photos Hardy. The answer is A. It stays at the selected derate even when it is complete.

[Hardy Heinlin]

Very nice. Thank you!

Can you tell me if this is the NG FMC or the legacy FMC?


|-|ardy

[andmiz]

NG.