egt limits for b744

[bone]

Need some clarification on the egt limits for PW4056 equipped B744s.The EGT brief for my outfit goes like this....

Ops Condition Temp limits Time limit
------------------ -------------- ------------

T/O 650 C 5 min

Max Con 625 C Con

Start Grnd 535 C

Start Air 650 C


For the T/O phase,when does the time limit start...upon reaching 650C or setting of T/O thrust?And if 650C is not reached during T/O, can the engines be operated at that power setting indefinitely,provided the max continuous limit is adhered to?If possible ,please provide the source of any answers so that I can disseminate the info,or deflect accusations of duff gen!

[lomapaseo]

For the T/O phase,when does the time limit start...upon reaching 650C or setting of T/O thrust?And if 650C is not reached during T/O, can the engines be operated at that power setting indefinitely,provided the max continuous limit is adhered to?If possible ,please provide the source of any answers so that I can disseminate the info,or deflect accusations of duff gen!

There is only one correct answer and no sense in shopping answers furthur.

Boeing must answer this and they will of course confirm the answer with the engine manufacturer.

Simply ask your local Boeing rep

[LEM]

and if you manage to get an answer, please let us know!

[boofhead]

Another example of people trying to make things more difficult. Refer to the Flight Manual and you will see that for all engine limits, the only valid criteria are the colours of the display. Red is the top, amber is cautionary and white is normal range. The numbers are not allowed to be used to set or decide engine limitations.
Why would anyone want to go beyond that? Anal retentives maybe.

[quid]

red lines?

bh-

Some engines are not quite that simple. On my a/c there are 4 different temperature limits. Should there be 4 red lines then???

[HotDog]

Seems pretty straight forward. A five minute limit of 650C means exactly that. In other words you are allowed to operate that engine for 5 minutes at 650C when it reaches that temperature.

I'm not familiar with the 4056 but are you sure the ground start limit is 535C and air start 650C ? It is usually the other way around.

[LEM]

And what is the limit if you only reach 649°c?

[HotDog]

T/O power EGT limit is 650C for five minutes except in the case of engine failure when it is ten minutes with most engines. I personally would regard 649C the same as 650C then reduce thrust to max continous if needed after five minutes other than in the case of engine failure. However, under normal circumstances, you never need takoff thrust for five minutes anyhow, you would set climb thrust long before that. Do you fly airplanes LEM?

[LEM]

My question was purposely provocative, and seems to have reached its goal........

Bone's question is not so silly, and your explanations are not so straitforward.
He's not trying to make things more difficult, he's got a doubt and we should try to answer clearly (and since we are supposed to know, it's interesting to see what we know before asking Boeing).

The first question was:

For the T/O phase,when does the time limit start...upon reaching 650C or setting of T/O thrust?

and the second was:

And if 650C is not reached during T/O, can the engines be operated at that power setting indefinitely,provided the max continuous limit is adhered to?

I think the mistake lies in focusing on the limit itself, rather than on the temperature range .
A range, like a segment, is defined by two points.
At takeoff, the EGT is supposed to exceed the Max Con limit, but not the 650 limit.
You are allowed to operate for 5' in this range , the Takeoff range , in which you are even if you don't necessairily reach 650.

Reverend, saying that

you are allowed to operate that engine for 5 minutes at 650C when it reaches that temperature.

only confuses ideas.
Even if you don't reach that temperature you are in the Takeoff range because you've exceeded 625.
That's why I asked about 649!

It doesn't matter if you

personally would regard 649C the same as 650C

.
The fact is that you are in the Takeoff RANGE.

Going back to the first question: when to start timing?
academically, when the EGT enters the Takeoff range (625-650).

Second question: in my opinion YES, if the EGT is kept within 625 there's no time limit, even if the setting is for takeoff.

[HotDog]

Oh my God! LEM you are playing on semantics. Once again. if 650C for five minutes is the limit EGT for takeoff and you do not reach that EGT temperature, you can certainly set max continous power if you like but why would you? Normally you set T/O thrust which rarely results in max EGT and after cleanup you set climb power, which is way below max continous. Again I must ask you if you are flying heavy jets?

[LEM]

Oh my God! LEM you are playing on semantics.

Not at all.

Once again. if 650C for five minutes is the limit EGT for takeoff and you do not reach that EGT temperature, you can certainly set max continous power if you like but why would you?

Who said I want to set Max Cont?

Normally you set T/O thrust which rarely results in max EGT and after cleanup you set climb power, which is way below max continous.

Yes sir, everybody knows that. So what?

It appears to me that all these comments have little to do with the original post.
Bone's question was very precise, and I tried to answer precisely.
Everything will be crystal clear if we point out that at 626°c we are in the takeoff range, thus subject to the 5/10 min limitation, exactly like being at 650°c.


Now we should ask Bone which reply is more clear

ps:

Again I must ask you if you are flying heavy jets?

please, don't be so puerile

[bone]

I checked the book and the inflight start limit is 650C.For engine start,the red line is at 535c until the engine reaches idle whereupon it changes to the 650c limit.Regarding why to keep the engines at T/O setting beyond 5 mins versus what normally happens,I go with LEM's reply.We know that climb power is set way before 5 mins,and that it is below max con most of the time,but its a matter of normal ops versus can it be done?Haven't managed to get in touch with the local Boeing rep,and will try to get a reply unless someone beats me to it.I asked around about the 5/10min limit and seems to be limited to the machines with two motors.