I still don't understand the Thrust Limit assumed temp

[dmwalker 611]

 

 

As for the combination of derate and assumed temperature -- I have to say I'm a little surprised to see that in the manuals. Most airlines that I'm aware of tend to have procedures requiring the opposite -- i.e. prohibiting the use of reduced thrust on contaminated runways.

It is prohibited on contaminated runways but, on page SP.16.1, it states that fixed derate, assumed

temperature method, or both are allowed, with certain provisions, on wet runways ( meaning without standing water, etc).  On page PD.30.1, it states that the use of a lower thrust rating and/or the assumed temperature method of thrust reduction is required for below minimum take-off weights.

 

Anyway, "financial" seems to be the answer I was looking for. Thanks.

20 minutes of flight with 15000kg of fuel and empty load

That certainly sounds like a below minimum take-off weight situation where PD.30.1 would apply.

 

 

I hope I didn't confuse you.

Not at all but I think I detected a sense of nostalgia.

[Budbud 227]

That certainly sounds like a below minimum take-off weight situation where PD.30.1 would apply.

 

 

It may be but the FCOM doesn't give you the minimum takeoff weight (which is given in the FPPM, not provided with the addon).

PD.30.1 (or PD.60.1 for -300ER) gives you the max takeoff weight.

 

And by the way I have just tested in the same conditions with full thrust... 9000fpm during initial climb. My stomach got down to my feet! 

[TailDraggerPilot 17]

It may be but the FCOM doesn't give you the minimum takeoff weight (which is given in the FPPM, not provided with the addon).

PD.30.1 (or PD.60.1 for -300ER) gives you the max takeoff weight.

 

And by the way I have just tested in the same conditions with full thrust... 9000fpm during initial climb. My stomach got down to my feet! 

PMDG did provide the performance charts for the 777X, both LR and F, it's in the FCOM Vol.1. PD.30.1 gives you Minimum Takeoff Weight.

[Budbud 227]

Hi,

 

Ok you are right! My fault sorry. However, the minimum weights are given only on the PD.30.1 and PD.40.1 (B777-200LR & -200F)? What about the -200,-200ER, -300 & -300ER? Or is it another mistake from me?

Thanks.

[dmwalker 611]

I referred to PD.30.1 because it applies to the Tutorial 1.5. Minimum take-off weight for the B777-200LR with the GE engines and flaps 15 and OAT 20°C at sea level or below is 190.5 kg or 419,100 lbs so I estimated 416,900 lbs for the 313 ft altitude of KIAD. As I recalculate, it's more like 416,200 lbs.

 

Edit: You beat me to it. I really have to learn to type faster. I believe you are correct about the -200,-200ER, -300 & -300ER.

[TailDraggerPilot 17]

Hi,

 

Ok you are right! My fault sorry. However, the minimum weights are given only on the PD.30.1 and PD.40.1 (B777-200LR & -200F)? What about the -200,-200ER, -300 & -300ER? Or is it another mistake from me?

Thanks.

That's correct, only the -200LR/F have the minimum take off weights. The provided FCOM does provide most of the performance data for:PD.10 -200 GE90-76B, PD.20 200ER TRENT892, PD.50 -300 PW4090, and PD.60 -300ER GE90 

[Budbud 227]

Thanks for confirmation.

Sorry to get a bit off topic here.  :rolleyes:

[ICSimulations 2]

I had a flight today from KMEM to KHOU in a 777. PPFX/TOPCAT stated the assumed temp is +70C. OAT was 28C. The FMC on the PMDG 777 did not derate to T-01 as Topcat had recommended. I selected T-01. What the FMC did do was switch to CLM2? What are the differences between the left and right columns on the  Thrust limit page? What are the differences between the CLMB settings? 

 

Thanks. 

[sosuflyer 30]

I had a flight today from KMEM to KHOU in a 777. PPFX/TOPCAT stated the assumed temp is +70C. OAT was 28C. The FMC on the PMDG 777 did not derate to T-01 as Topcat had recommended. I selected T-01. What the FMC did do was switch to CLM2? What are the differences between the left and right columns on the Thrust limit page? What are the differences between the CLMB settings?

 

Thanks.

If Topcat is telling you to do TO-1 plus assumed temp, you have to select the key next to TO-1 first, the 777 will never select it for you. For climb thrust, the FMC automatically selects the highest climb setting that is still below the selected takeoff thrust. Although, some carriers use max climb thrust no matter what

[ICSimulations 2]

Thanks. Is the lower CLMB thrust selected because it was hot in memphis at 28C?

[Budbud 227]

Hi,

 

The FMC never derates the takeoff thrust on its own even when selecting an assumed temperature. 
However, it selects a derate climb thrust depending on the derate takeoff thrust and/or assumed temperature selected.
That is a normal behaviour and it prevents an increase of thrust when switching to climb thrust if full climb thrust was to be higher than the selected takeoff thrust.

 

The principle of the derated climb thrust is the same as for the derated takeoff thrust:

CLB-1 = 10% CLB

CLB-2 = 20% CLB

 

So basically, you first enter the assumed temperature and/or select the derated takeoff thrust on the left.
The FMC will then "proposes" a climb thrust (derated or not) depending on the takeoff thrust.

You can then keep that climb thrust or change it depending on your SOP and other considerations.

Thanks. Is the lower CLMB thrust selected because it was hot in memphis at 28C?

 

No the FMC selected CLB-2 because it is the highest climb thrust below the TO-1 + 70deg assumed temperature.

Any climb thrust higher than CLB-2 in that condition would result in an increase of thrust when the FMC changes the thrust command from takeoff thrust to climb thrust.