PT6 Hot Sections

[dustoff17]

Sulphidate(ing) is a serious and costly concern with regards to engine maintenance.

The theory of "less temp = less $" is flawed. Consider that a lower than POH-recommended temp setting results in a slower speed (as mentioned by OH58; 15kts).

What's that doing to the Hobbs?

Yes, you're logging more flight time but your'e also getting to TBOs and inspection criteria that much faster. A 0.2-0.3 per leg, 2 legs a day, five trips a week is 104-156 hours a year! Good for the log book, not so good for the maintenance.

If you're flying for someone else, log the flight time! Kidding; set the lowest of the temp range provided in the POH.

 

[deadstick]

Sulphidate(ing) is a serious and costly concern with regards to engine maintenance.

The theory of "less temp = less $" is flawed. Consider that a lower than POH-recommended temp setting results in a slower speed (as mentioned by OH58; 15kts).

What's that doing to the Hobbs?

Yes, you're logging more flight time but your'e also getting to TBOs and inspection criteria that much faster. A 0.2-0.3 per leg, 2 legs a day, five trips a week is 104-156 hours a year! Good for the log book, not so good for the maintenance.

If you're flying for someone else, log the flight time! Kidding; set the lowest of the temp range provided in the POH.

So here's the thing, the BE20 POH does not list a range, just a Max Observed ITT Cruise. In the Performance section, there are different RPM tables that list TQ/FF based on Altitude. No ITT. Weaker engines (pre SBones that are @ 2999.9hrs TSOH) might not make book torque before hitting the ITT limit. I've flown the "on condition" OH engines and they usually just temp out. As mentioned earlier, a stipulation of the OCOH is the max temps for climb and cruise are lowered (IIRC ~30deg). Things get fun when there is a split between the LH and RH engines.

Does the C12 -10 have a min ITT or a range for cruise?

 

[Bandit_Driver]

Sulphidate(ing) is a serious and costly concern with regards to engine maintenance.

The theory of "less temp = less $" is flawed. Consider that a lower than POH-recommended temp setting results in a slower speed (as mentioned by OH58; 15kts).

What's that doing to the Hobbs?

Yes, you're logging more flight time but your'e also getting to TBOs and inspection criteria that much faster. A 0.2-0.3 per leg, 2 legs a day, five trips a week is 104-156 hours a year! Good for the log book, not so good for the maintenance.

If you're flying for someone else, log the flight time! Kidding; set the lowest of the temp range provided in the POH.

I may be wrong as it has been awhile since I last flew PT6's but if I recall our mx program correctly the company had to pay for parts that were replaced. So it didn't matter when you got to the overhaul, what mattered was how much internal crap needed to be replaced. The less of the hot section that needed work the cheaper the overhaul was.

On the GE CT7's they were on GE's power by the hour program and GE dictated the max ITT's.

 

[///AMG]

Just my two cents but I have always been told that watching the ITT spikes is more critical to engine life than the cruise temp. That being said we flew about 60 cooler than red line in the caravan.

Kind of the same thing with automotive engines. Much harder on components/oil/lubricants when you have wide operating temp variances when compared to high mileage motors run sparingly at a near constant temp.

 

[dustoff17]

Does the C12 -10 have a min ITT or a range for cruise?

Yes.

 

[deadstick]

Yes.

Well, there you go. What is it?
(stand up and verbatim....)

 

[jergar999]

The company I work for has been operating King Air 90, 100, and 200 models forever. I've been here since early 2001. We did a two year comparative study on the -21, -28, and -42 engines and found that on four airplanes there was no difference in the cost of a hot section with different operating procedures (Firewalled vs. decreased cruise with reduced fuel flows). Fuel burn vs. lower block times also came out at just about a wash, but the decreased airframe total time means more trips between scheduled maintenance and less airframe time, which translates to a greater aircraft value.

 

[deadstick]

The company I work for has been operating King Air 90, 100, and 200 models forever. I've been here since early 2001. We did a two year comparative study on the -21, -28, and -42 engines and found that on four airplanes there was no difference in the cost of a hot section with different operating procedures (Firewalled vs. decreased cruise with reduced fuel flows). Fuel burn vs. lower block times also came out at just about a wash, but the decreased airframe total time means more trips between scheduled maintenance and less airframe time, which translates to a greater aircraft value.

Very interesting. Do you operate on the MORE program?