Caravan AD... Ouch!

I believe this issue caused a Wiggins 208 to have a failure as well, thankfully with a good ending. From what I can remember it was 800OVC, and there was a nice grass field right in front of the pilot when he popped out of the clouds, and landed the airplane damage free.
 
Pulling the prop back does nothing to the ITT temperature in the -114/114A. ITT is measured at the PT guide vanes between the two turbines, so any changes to the power turbine would be down flow from the ITT probes and only really affect the power turbine, which isn't the turbine requiring blade inspection/replacement per the AD. Though it would presumably change the flow characteristics through the engine, I find it hard to believe it would drive up then temps around T4 and through the compressor turbine, then indicate normal temperatures at T5 just on the other side of the CT. If I remember today, I'll grab some pictures at different settings.

Dunno what other operators do but we run 1900 RPM (redline) 100% of the time with a very high TBO.

We also lost a 'van to this, fortunately with only minor injuries.
 
The F104 objects to your assertion.

You mean the F-101, don't you? Most thrust of any of the Century Series, and much higher thrust-to-weight ratio than the Starfighter.

But I'm still partial to the F-111F with those awesome twin TF30-P-100s. The sight of those bright purple afterburners with shock rings during a night takeoff would send chills up and down your spine.
 
I understand just pulling the prop back wouldn't make much a difference but of course pulling the power back would. Operating at reduced power settings will reduce operating temperatures.
 
Running at 20-40 degrees cooler might cost less than three or five knots so we are not talking huge power changes here just keeping the turbine happier
 
Running at 20-40 degrees cooler might cost less than three or five knots so we are not talking huge power changes here just keeping the turbine happier
Yeah, but here's the "rub" with this mindset; you take a 225nm trip and average140kts, it takes you about 1.6 to make the trip. Now make the same trip @135kts (top of your 3-5kt difference); it takes you 1.7 to make the same trip. If you make the trip twice a day (package haul for example), you add an hour to the hobbs every week. Great for pilot log book, not so great for maintenance. You'll reach a 100hr inspection 4 days earlier than if you ran at 140kts.
Many operators will make short order of the trips and worry about the other stuff later......don't necessarily agree but it is what it is.....
 
Running 40 degrees cooler is kind of a lot if you're flying high and need the power to get out of your own way.

For longer flights (3-5 hours) under 10k I just set the fuel flow to 360pph. This will give me at least 160 true, 13-1400#s, and ITT at 700 or less.
 
We keep our pilatipi at 700 ITT, even if that 100 hour comes a few days earlier, apparently our insurance is cheaper by doing so.
 
We keep our pilatipi at 700 ITT, even if that 100 hour comes a few days earlier, apparently our insurance is cheaper by doing so.

We use 720°, yeah, the we get a few more hundred hours per overhaul, but we're getting our first engine back from overhaul and there are NO (zero zilch, zip) problems with the hot section - which to me was somewhat surprising because of the places we take it.
 
We use 720°, yeah, the we get a few more hundred hours per overhaul, but we're getting our first engine back from overhaul and there are NO (zero zilch, zip) problems with the hot section - which to me was somewhat surprising because of the places we take it.
Between the inertial sep and the screen I'm not surprised. If anything I'd think the compressor would get wear. I think folks are overthinking this a little, I would be willing to bet that the cycles/hour ratio and in some cases the residual temp on start have far more to do with engine life than how hot you run it in cruise.
 
That's what I was thinking too. The mass airflow has to do more work to move the power turbine when it's loaded at lower RPM's than when it's loaded at higher RPM's.

Unfortunately my variety of PT6A and airplane combo doesn't give me control over Np.
It's quite noticeable on the Garrett. I don't know how much of that is due to it being a single shaft and how much is just the SRL adjusting the temp indication.
 
Between the inertial sep and the screen I'm not surprised. If anything I'd think the compressor would get wear. I think folks are overthinking this a little, I would be willing to bet that the cycles/hour ratio and in some cases the residual temp on start have far more to do with engine life than how hot you run it in cruise.

That's why even though you can add fuel at the minimum Ng/N1/whatever your manufacturer calls it, sometimes it's a good idea to let the ITT/TIT/T6/whatever your manufacturer calls it come down before you add fuel again on a quick turn. That "whump" noise if you add at exactly 12% Ng with a hot motor on a quick turn can't be good for the hot section.
 
That's why even though you can add fuel at the minimum Ng/N1/whatever your manufacturer calls it, sometimes it's a good idea to let the ITT/ /T6/whatever your manufacturer calls it come down before you add fuel again on a quick turn. That "whump" noise if you add at exactly 12% Ng with a hot motor on a quick turn can't be good for the hot section.
Honeywell strongly recommends either waiting or motoring until residual temp is below 200.
 
With the CT7-9B GE says to motor until ITT is below 175. Can't remember what the CASA was, but 200 sounds familiar.
 
I make it a point to motor until below 150 on all my turns, if it's a hot summer day I try to keep the i-sep closed through the start sequence as well, and open it once the engine is stable an a GEN is on. Also I make sure there's not alot of loose gravel around before I do that.
 
I make it a point to motor until below 150 on all my turns, if it's a hot summer day I try to keep the i-sep closed through the start sequence as well, and open it once the engine is stable an a GEN is on. Also I make sure there's not alot of loose gravel around before I do that.

We have ours open any time we're on the ground.
 
Back
Top