My post was obviously not worded clearly. If you were flying 300kts at 96% and 650C you could increase RPM and temperature will drop because more air is being supplied by the compressor. Power will also drop because more energy is now being consumed by the compressor. If you add enough fuel to regain your 300kts your temp will be significantly less than 650C, probably 630C. So, to go 300kts you have a choice 96% 650C or 100% 630C.

Any turbine engine will be more “efficient “ (BSFC) as the EGT goes up. Your TPE331 will be VERY “efficient “ at 670C for the few seconds before it grenades. Efficiency and longevity are at odds with each other

My first MU2 was an N model and I only had it a year before Frank Borman convinced me to get a Marquise and I don’t recall the details of -6 engine operation. I never had a -10 converted airplane . My understanding is that that the SRL system was introduced to allow the temperature sensors to be installed in cooler conditions which extended their life. An operating ITT/EGT gauge for each engine is required for any flight so failed ITT sensors were a big deal. The same thing could have been accomplished by giving the pilot a table showing what temperatures could be used under which conditions. The SRL system reduces the pilots workload allowing automatic starting and a single temperature redline to be used under all conditions.

As you stated, the engine will go between HSI at 100% RPM and 100% ITT/EGT. However there is no room for operator error and the HSI might be more expensive. In my Solitaire, I run 96% and 640C. If find the noise less obnoxious, the speed adequate and there is some room for error or creep on the EGT. Periodically, I will run 96% 650C and verify that I’m getting book performance numbers.

Helmuth sometimes didn’t go into detail on whether he was referring to measured EGT, the “massaged” EGT on an SRL equipped aircraft, or the ITT those numbers actually represented. Obviously, the first stage turbine blades only care about the temperature they are being exposed to, not the temperature somewhere else. I don’t think all pilots understand how this all works.

My prior MU2 was a Marquise. Pre RVSM, I would fly long legs at FL290 which would require 100% 650C when heavy if the temp was ISA +10C or higher. The Marquise is a pig compared to the Solitaire. Same wing, same engines and 1000lb weight difference!

FWIW, I've operated 2 MU-2 -10 conversions (an M and a G). They both had SRL systems and 650C redlines.

Yup, really. The current owner of the G is on BT often.

My post was obviously not worded clearly. If you were flying 300kts at 96% and 650C you could increase RPM and temperature will drop because more air is being supplied by the compressor. Power will also drop because more energy is now being consumed by the compressor. If you add enough fuel to regain your 300kts your temp will be significantly less than 650C, probably 630C. So, to go 300kts you have a choice 96% 650C or 100% 630C.

Any turbine engine will be more “efficient “ (BSFC) as the EGT goes up. Your TPE331 will be VERY “efficient “ at 670C for the few seconds before it grenades. Efficiency and longevity are at odds with each other

My first MU2 was an N model and I only had it a year before Frank Borman convinced me to get a Marquise and I don’t recall the details of -6 engine operation. I never had a -10 converted airplane . My understanding is that that the SRL system was introduced to allow the temperature sensors to be installed in cooler conditions which extended their life. An operating ITT/EGT gauge for each engine is required for any flight so failed ITT sensors were a big deal. The same thing could have been accomplished by giving the pilot a table showing what temperatures could be used under which conditions. The SRL system reduces the pilots workload allowing automatic starting and a single temperature redline to be used under all conditions.

As you stated, the engine will go between HSI at 100% RPM and 100% ITT/EGT. However there is no room for operator error and the HSI might be more expensive. In my Solitaire, I run 96% and 640C. If find the noise less obnoxious, the speed adequate and there is some room for error or creep on the EGT. Periodically, I will run 96% 650C and verify that I’m getting book performance numbers.

Helmuth sometimes didn’t go into detail on whether he was referring to measured EGT, the “massaged” EGT on an SRL equipped aircraft, or the ITT those numbers actually represented. Obviously, the first stage turbine blades only care about the temperature they are being exposed to, not the temperature somewhere else. I don’t think all pilots understand how this all works.

My prior MU2 was a Marquise. Pre RVSM, I would fly long legs at FL290 which would require 100% 650C when heavy if the temp was ISA +10C or higher. The Marquise is a pig compared to the Solitaire. Same wing, same engines and 1000lb weight difference!

Of course the climb charts are at 100%. Cruise charts are 96% 650C

….

With respect to the time exposure during over-temp excursions: how do the test cell temp margin numbers come into play ?