View Full Version : 737NG max start temp red line

sudden Winds
23rd Jun 2015, 13:55
Hi folks,
I seem to recall that the max temp start red line is fixed at 725c regardless of OAT. I think I read that in the afm. Please clarify.

23rd Jun 2015, 15:42
FCOM1&2 and QRH. Pls read.

23rd Jun 2015, 19:01
I apoligise that I haven't the books to hand, so please read and correct me, but;....
I was always told that the start max temp magenta bug was variable. It depended on many ambient variables, e.g. OAT, altitude, density etc. For an Inflight Start 725c is specified.

23rd Jun 2015, 19:37
Yup AFM limits for GND start, 725C.

sudden Winds
23rd Jun 2015, 20:14
FCOM1&2 and QRH. Pls read.
Thank You for your pointless response.

sudden Winds
23rd Jun 2015, 20:16
Yup AFM limits for GND start, 725C.thank you. What I thought. Do you have the afm page number? Could you send me a screen capture of that ?

24th Jun 2015, 08:19
I'm on an iPhone so don't know how to post a pic.

It is in section 1 page 7A. It's not written in the FCOM.

24th Jun 2015, 10:30
With the introduction of the NG Boeing removed the references from the Limitations section in the FCOM and used Red Line as a limit, the display telling you when you had an overtemp situation.
Prior versions of 737 had the temperature limitations mentioned in the FCOM (their engine instruments were a lot smaller and thus harder to read, their numeric display was easiest to read).
Engine limitations are still contained in the Limitations section of AFM though, even though Red Line limits were introduced. It is one of the few limitations not contained in FCOM for crew reference.

NG: 725/925/950
CL: 725/895/930
[Maximum temperatures for: start/continuous/takeoff]

25th Jun 2015, 00:19
To get to the basics of the issue: why would a max EGT, function of Turbine temp, be variable with OAT or pressure?

29th Jun 2015, 12:45
Good question, actually.

While I've been out of the circuit too long, in practice I recall there was a normal correlation between max start EGT for a given engine and residual EGT and OAT. (Not so much PA).

And I should think that a conscientious engineering organization could employ this relationship to create an alert level, objective being to flag an engine that is approaching a need for maintenance - despite no redline exceedance.

All of which might create another tug-of-war between ops and engineering. :}