Thermal limitation ? (MGT, TOT, ITT, T4, T5...)
All:
Mr. Lappos suggested I post this situation for discussion. For myself, this came up some time back but, I was recently browsing (catching up) through the threads and saw a couple of engine limitation question and answer postings and, well..., I suppose it fits in with those.
BACKGROUND
A while ago, I had been asked to render an opinion to some folks I once flew for as to the possible detrimental effects of continually (not continuous) operating an engine above the max continuous MGT (or whatever you want to call it) rating.
The goof's (read: pilot) "normal" operational cruise configuration is (was) pulling into the top of the five minute MGT limit for four minutes - thirtysome seconds then reducing power to max continuous MGT for fifteen to thirty seconds and back up again. Unfortunately (for him), the dude's internal timer malfunctioned, he didn't get the power down in time and the gauge recorded the exceedence. Pilot's response: "...it's done all the time..." and, "...standard practice here..." and, "...where does it say you can't...".
The Company contacted the manufacturers whose response(s) to them was: [in essence] "Refer to flight manual".
Now, lets go a step further here by establishing some constants... Company operates several of the same make/ model aircraft. All are assigned to a specific base within a region of the country (i.e., while some very limited intra-region swapping is done, the aircraft are base and crew specific). So, lets assume the aircraft in question is "Aircraft A". Aircraft A has a long history of turbine problems that could be attributed to heat and has yet to make TBO/ TBI on the hot end while Aircraft B, C, and D have experienced no similar problems. This is not engine specific as Aircraft A has had several different engine/ turbine configurations installed with "premature problems" on each. Crews B, C and D state they do not operate as Crew A and the onboard monitoring systems concur. Mission profile are identical and finally, if a difference does exist, assume Aircraft A operates in the least hostile altitude/ temerature environment.
For clarification, I ain't no Norman Einstien (or his brother Al). I'm a driver - nothing more. I been doing it for so long folks are of the mistaken impression I know **** so they end up axin' and I give 'em my opinion (which I did) based on the ol' "what would I do if it were my aircraft and operation" answer and leave the thinkin' up to the folks that are good at it.
By the way... Nick, the real Al Einstien, said he'd provide the real answers to the question.
Anyway..., have fun - it'll be interesting to see how FUBAR I wus.