Flex81

Hey all,

I was recently flying with a guy that matched up his ITT in cruise and not his torque. Our ITT was matched but our torques were off by 6%. I have always been taught to match up torque in cruise. When I was flying, he asked why I was matching up the torque I replied "because that is the correct way to do it". He asked "who told you that?" I said I thought it was common knowledge. Our manual does not say one way or another (my plane has PT-6's) Anybody know of any documentation I can reference on this matter? Maybe I was taught wrong... anyone?

Flex

JOHNSCHR

I fly with the same engines and we are taught to match torque but limit the torque to maximum allowable ITT depending on altitude. The reason we match torque is because the ITT will vary depending on the condition of the engine (e.i. the more time on the engine...the hotter it will run). If you matched the ITT on an older engine to a newer engine there is a chance you could over torque the the newer engine

plasticpi

At Colgan, we use torque as our power indication. ITT is just something we don't let get over a certain number, depending on what phase of flight we're in.

But, we don't set 850 degrees on both engines and call that cruise power or anything like that.

We don't have PT-6s, but I can't imagine it being any different no matter who made your turbine engine.

I think the misconception comes from the fact that the cruise powers are charted with the intention of keeping ITTs at a desired level, so the manufacturers tell you to set 80% torque, but what they really are concerned about is keeping the ITT below some number. Pilots who know this then try to put the cart before the horse and just set the ITT to that number. While they are not exceeding anything (as long as the other indications stay in the normal range), they are not doing the engine any favors, and are shortening the time before it needs a hot-section or overhaul.

Luv2Rotate

There really isn't documentation. ITT will vary with altitude and temp therefore; in many cases it would be almost impossible to match torque and ITT for cruise. Take a look in the POH its gives various limitations regarding torque, ITT and RPM settings. These are the numbers I would follow because they are considered operating limitations.

BIrwin

Just my take...

When I used to fly the BE-1900 I set the power via Torque, with two notable exceptions:

1) ITT when temperature limited in the climb (think old BE-1900C model)

2) Fuel flow with an MEL'd fuel guage

As for a reference Airplane Flying Handbook 14-7 (FAA-H-8083-3A) or the procedures/performance sections of the respective flight manual.

From my perspective if he/she is PF then they can set the power any way they like (within reason). I would be curious what their reasoning is. Is it a maintenance/save the engine type mentality?

WJI

Rightseat Ballast

When I was flying the SAAB, I was taught to match up the torques. We noted the difference in ITT values, and recorded the trend in those "delta-T's" to monitor engine degradation. Those were GE engines, which of course are not what you flying. Perhaps P&W designed your engines to be flown a different way, but matching ITT does not make sense to me. Torque is pretty much your best measure of power output in the props. Would you intentionally set differential thrust? I'm going to back you up on this one. Of course, some of those old timers bring along the baggage of the "way it used to be done" and substitute that for the correct way.

FR8DWGIE

In the saab the power setting is set by % torque for current conditions, i.e. altitude, oat, whether or not anti-ice is being used, and prop RPM. Though that setting can be limited due to ITT. So for example set both engines at recomended torque and if one engine is exceeding an ITT limit, pull the hot engine back until it is within limits. So to answer your question in the saab we match the torque, but I don't have any experience on other turbo props.

FR8DWGIE

Wow, a bunch of you beat me to the punch.

SnowMan

Old Convairs we used temp to set cruise power, and horsepower for takeoff power.

The Juice

Anyone who uses ITT to set cruise has a lack of system understanding. Imagine if you have a plane with a 10% torgue dif when matching ITT, does it seem logical to fly with a 10% torgue split? Better get ready for some trim to keep the plane from flying sideways.

There are times as mentioned where torgue is limited due to temp, so you need to bring both engines back down to allowable torgue while maintaining ITT limitations, you still do not need to match ITT

We have a FO in IAH who matches ITT and is looked at like a buffoon