EGT Limit

[Skybird]

Hello,

Using PSX 10.70
CF6 engines
Malfunction>Engines>Foreign object ("Else" condition)

During takeoff, EGT went to 989°C and indication remained white. It should be red when passing 960°C.

EGT indicating system:
On the vertical bar, there is an amber band limit that shows the EGT caution range. If the EGT gets to the amber band limit, the vertical bar and digital display change to amber.
If the airplane is in TOGA mode, the vertical bar and digital display stay white during takeoff or go-around.
FCOM says: EGT indications are inhibited from changing color to amber during TO or GA for 5minutes (10min if minus 1Engine) after TOGA switch pressed.

However, it does not specify that the Red indication is inhibited. Once the red limit is reached, the vertical bar and the display should become red (any phase of flight)

CF6 operating limits:
MAX CONTINUOUS = 925°C
So normally above 925 till 959 = amber caution range. (I noticed in PSX that amber comes too early at 870).
TAKEOFF= 960°C = and above = red

I didn't checked on PW, but philosophy remains the same.

Do you agree with this?

Steve.

[Hardy Heinlin]

Hello Steve.

"If the airplane is in TOGA mode, the vertical bar and digital display stay white during takeoff or go-around."

"However, it does not specify that the Red indication is inhibited. "

Yes, it does: It says the entire indication "stays white". That means to me it won't turn red but will stay white.


|-|ardy

[Skybird]

Hi Hardy,

No, it doesn't say the "entire" indication stays white...

It says: "EGT indications are inhibited from changing color to amber...

Source: FCOM and AMM

The 5 minutes all engines/10 minutes minus 1 engine, in the caution (amber) range are part of the engine certification.
Beyond the red limit, you are outside the certification.

If this happens during takeoff (above red limit), a crew action is required. Procedure-wise, no action will be done before reaching 400ft Above Field Elevation. At 400ft, the ENG LIMIT QRH Check-list applies and the thrust lever on the affected engine must be retarded until indications return to normal.

You never leave an engine running above any red limitation, this is violating its certification...

[Skybird]

Also, the Airplane Flight Manual says:

The engine limit display markings on the EICAS must be used to determine compliance with the maximum and minimum limits and precautionary ranges.

ENGINE RPM:
The maximum operational limits are:
N1 117.5%
N2 112.5%
ENGINE EGT:
Operating condition - Takeoff 960°C - Time limit 5 minutes (10 minus 1 #)
                               Maximum continuous 925°C - Continuous

[Hardy Heinlin]

OK, I believe you.

But I don't understand this context:

"Procedure-wise, no action will be done before reaching 400ft Above Field Elevation."

Why should the crew be distracted by a red warning if no action will be done anyway until 400 ft?

[Hardy Heinlin]

I'm not quite convinced yet. Another AOM says:


EGT (degrees C), displayed:
• (white) - normal operating range
• (amber) - continuous limit reached
• (red) - start or takeoff limit reached

Note: During TO or GA, indication remains white for five minutes when continuous EGT limit is reached or exceeded.


The "Note" in this text layout does not explicitly exclude the red limit of the text section above. "White" is the only color mentioned in the "Note".


P.S.:
Steve, do you have a source to confirm that the amber range begins at MAX CONTINUOUS and not at 870?

[Skybird]

I agree with you.

I guess you mean: why not inhibit an engine exceedence until 400ft AFE if anyway, no action is done before this height.
Talking about distraction: EICAS messages are never inhibited even during takeoff phase. So red warnings may also appear. It's only from 400ft AFE that crew actions will be done.

Note: During TO or GA, indication remains white for five minutes when continuous EGT limit is reached or exceeded.

When "continuous is reached or exceeded"... up to the maximum operating limit.

Note the AFM wording:"...compliance with the maximum limit"

[Skybird]

Steve, do you have a source to confirm that the amber range begins at MAX CONTINUOUS and not at 870?

FCOM ENGINE section, same page as yours most probably:

EGT Amber band: displayed (amber) - continuous EGT limit
EGT Indication: (amber) - continuous limit reached
Then, if you go in the limitations chapter in AFM: Max Continuous 925°C - Continuous

The 870 is the maximum EGT peak value during engine start. There is a maximum of 40 sec of overshoot above 750 with the max limit of 870.

[Hardy Heinlin]

Convinced now. Thanks :-)

[Hardy Heinlin]

The modifications are now available in PSX 10.72:

http://aerowinx.com/board/index.php?topic=4191.0


|-|ardy

[Skybird]

Hi Hardy,

Sorry to bring the subject back... I have "Foreign Object Damage (No severe)" in malfunction, and I see during my go around an EGT of 983°C taped white (CF6) iso red.
I did the same with P&W (Basic 022 situ - Go around, same failure) and I have a white EGT tape showing 693°C iso red.

Same in cruise, passing the 650° (P&W), or 960°(GE), EGT stays amber iso of red...

Did I missed something?

I'm using 10.76 version

Thanks
Steve

[Hardy Heinlin]

Hi Steve,

I see no problem here. I get red tapes on all models in TO/GA and in cruise.

How long do you wait?

On GE and PW there is a 20 second delay before the red condition turns the tape red.

On the RR the delay is bypassed instantly when 805°C is exceeded.


Regards,

|-|ardy

[Skybird]

Ok, I didn't know about these 20sec...

"...If the EGT is more than the redline limit, the analog and digital indications change to red. During a redline exceedance, the vertical bar moves by the increase in exceedance but with a limit of 0.05 inches above the red line..."
From Maintenance Manuel.

There should be no delay in exceedance display as you operate beyond authorized limits.
Any exceedance requires an "Engine Overtemperature Inspection" (Task 72-00-00-206-064-N00). The inspection type depends on the time vs the highest EGT that occured.

With 20 sec delay, how would be an exceedance of e.g. 15s be noticed (and reported) if not red displayed and boxed  (stored in NVM)?

Hardy, where did you get this info?


Cheers,
Steve

[Hardy Heinlin]

I guess I derived this info from certain diagrams. Regarding the RR, Peter once told me that he used to demo the 785 exceedance going red after 20 seconds on take-off (in the BA sims). However, as I wrote above, the delay is bypassed instantly when 805 is exceeded. Perhaps I should apply this bypass function not only to the RR but also to the GE and PW (at the respective model specific limits). I think it makes sense to ignore harmless momentary farts in the lower part of the red range; just turn it red when it exceeds that intermediate level. On the RR the red range starts at 785 and that may be exceeded for 20 seconds without a red alert; only when 805 is exceeded, the tape turns red immediately. The gap is very small -- just 20°C. So just a minor detail. It could also be that only the RR system incorporates this delay. I can't remember at the moment.


Regards,

|-|ardy

[Britjet]

As far as I recall the 20 secs delay is correct..
Peter.

[Skybird]

I don't know the RR engine. I'm only familiar with GE and P&W.
LH sims do not have this 20s feature.

Check also this video:
https://www.youtube.com/watch?v=3tMeTR5AkZQ


Regards,

Steve

[Hardy Heinlin]

I agree that it makes sense to bypass the delay when a certain limit is exceeded. But it also makes sense to have a delay for low shortterm peaks (e.g. 20°C) like on the RR. Did you check this in the LH sims, or can you see this in that blurry video?

Before I remove that delay entirely from the GE/PW I'd like to be sure these models don't have such a "peak buffer".


Regards,

|-|ardy

[Skybird]

I saw it in LH sim, Hardy. I had engine failure on takeoff with the EGT getting red immediately after the "bang". But I don't remember the boxed value to be honnest.

[Hardy Heinlin]

I believe you, but I think you're misunderstanding me. I'm just talking about a 20°C buffer like on the RR. If your engine failure shoots the EGT more than 20°C into the red range within a nanosecond, the tape will turn red within a nanosecond. I.e. you won't see any delay.

[Hardy Heinlin]

Hi all,

any opinions on whether I should implement the "RR style" delay in the GE and PW as well?

I'm planning to implement (1) or (2):

(1) EGT immediately turns red when limit+0 is exceeded.

(2) EGT immediately turns red when limit+20 is exceeded or when limit+0 has been exceeded for 20 seconds.


(2) is "RR style". I don't know if the GE and PW have a similar 20°C buffer. What do you think, guys?


Regards,

|-|ardy