PT6 Hot Sections

MikeOH58

MikeOH58

Well-Known Member
Lets say red line ITT is 800. Will there be a major difference between an airplane always run at say 680-700 in cruise, compared to one that runes 770-780?

You always hear this discussion go back and forth, and if running 100-120 degrees cooler saves money, i'm for it, but I lose about 15 knots doing so.

So whats the truth?
 
Basically, it's like this:

Until you own the airplane, just fly the power settings the people who sign your paychecks would like you to fly. ;)
 
Some say that if you run the engine at 100 deg C low you run the risk of problems from corrosion. I forget the name that they call it but basically the higher temps burn something bad off of the turbine blades.

Also the engine is derated much more than you would think so as long as you run it within limits your good.
 
When I was flying T-34C's, we had a self imposed max torque (and EGT) that was meant to prolong the life of the motors, though they were rated up to figures beyond the limits that we used.
 
So you have -42s -- lucky.

Torque limit or temp, but I do keep it 20 degrees below max. It's 750 Max Cruise for the -41s. Of course, they are never matched up.
 
Yes, -42's max cruise 800 ITT. Unfortunately I also have the beech bridge, which makes this a 260 knot airplane at max power, and about 245 knot airplane at 700 ITT =(
 
Our -66's our limited 820C @ cruise. We run them at 785C. The boss has been flying them that way for 7 years now with no problems or adverse effects. We match temps at cruise. When we match temps on these engines the Ng is within .3% and the PPH is within 3-5lbs. The engines seem happy, the prop sync seems happy, and the fuel stays pretty well balanced. Then we don't touch it until getting back down into the 20K feet range where torque comes back up. Torque at cruise seems to be a bit more unreliable. I don't know if it is our prop combo or air density or what? It will vary 50-100lbs with the power levers matched compared to when they are matched down low they are nearly the same. It's weird to me but it seems to work?
 
There are programs for 135 ops where they lower climb/cruise temps and perameter monitoring that extends the life of the TBO for turbines. There must be something to reducing temps. It's usually not lower than 50C from max published cruise temp.
 
We had pretty low temps for the PT-6's I flew to extend their life when I was on king airs, never heard the corrosion argument. When I flew the same engine on the E-110 they were more worried about torque.

In my GE-CT7-5A2 days we ran them very cold compared to other operators and the climb/cruise perform sucked for it as we continually got out performed by our competators.
 
"When a pilot operates engines at a lower temp than red line it does seam to be a lower cost to complete the hot section inspection. You do not want to operate them at a too low of a temperature because the heat burns off all the pollutants from the CT blades. If the pollutants from the air do not get burned off then the blades will start to suphidate and at hot section it will be very costly. We see it best if the engines are operated per the P.O.H."

From my mechanic.
 
I fly the -42 and our mechanic asks us to limit max cruise to 750. He believes it increases the chances our motors will go to TBO. Our sister squadron does not use the same limit and I've seen them drop engines prior to TBO. This is hardly proof that a lower limit increases the lifespan, but it keeps our mechanic happy and he keeps our plane happy, which keeps us happy. In the end the few knots we give up are inconsequential.
 
deadstick said:
and you always do what the crew cheif "asks." :beer:
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Actually, we do. They make the best & cleanest airplanes I've ever flown, so we do what we can to keep them happy. We have a small squadron and only three mechs, so everyone is on board with catering to their wishes or they find themselves off the schedule. The only time we exceed this recommendation is when we are climbing through icing when the extra temp is the difference between climbing or not. The only other thing they ask us to do is to fly less than 200 KIAS in rain to keep from stripping off the paint. It's pretty easy to grant their requests.
 
Oh, no. I know. Our crew chiefs were always kind enough to let me fly their helicopters. Before, I was affirming that crew chief/pilot relationship.
 
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.
 
MikeOH58 said:
"When a pilot operates engines at a lower temp than red line it does seam to be a lower cost to complete the hot section inspection. You do not want to operate them at a too low of a temperature because the heat burns off all the pollutants from the CT blades. If the pollutants from the air do not get burned off then the blades will start to suphidate and at hot section it will be very costly. We see it best if the engines are operated per the P.O.H."

From my mechanic.
Click to expand...

Thats the word I was looking for...
 
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