T-6 acronyms

[Guest ynotminot]

Just looking over the T-6 Ops limits and was curious on the definition/abbreviation of the following:

1. ITT - Inter Turbine Temp?

2. N1 - ?

3. Np - ?

4. PMU - ?

Thanks in advance.

[Gravedigger]

PMU- Power Management Unit

[HerkDerka]

I have yet to fly the T-6. But in T-44s ITT was Interstage Turbine Temerature and N1 was Engine RPM. My best hypothesis is that Np is Prop RPM which is called N2 in the Peg. It gets even better when you get to the Herc and have TIT! (Turbine Inlet Temperature).

HD

[ 17. May 2004, 18:41: Message edited by: HercDriver24 ]

[Guest C-21 Pilot]

In the C-21, we have the following:

N1: This is the fan RPM, read from a monopole sensor, and states the low pressure compressor output.

N2: This is the turbine RPM, read by a monopole sensor, and states the high pressure compressure readout.

Pt2/Tt2: This is a pressure and temperature sensor that sends various signals to our fuel computer.

ITT: Interstage Total Temperature, it's the temperatur read at the 3rd stage turbine, where in the C-21, is how you usually fly...ex, setting a 795 ITT, or 832 for 30 minutes max, etc.

[HerkDerka]

That's pretty intresting C-21. So you don't measure EGT? I remember the Tweet used EGT, but that was probably because it was a single compressor wussy jet.

HD

[BFM this]

Haven't flow the T-6 but I do have some time with the PT-6 series engine.

If you can visualize the reverse flow, compressor section spooled directly to the first stage turbine. There the spool stops and right next to the first turbine is another turbine: a power stage turbine which is geared to the prop.

N1: the speed of the first stage turbine and compressor section, in percent of rated rpm.

Np: the speed of the prop, typically in rpm's (IE 1700-2200 normal range for an early model King Air -90), but not always.

ITT checks as C-21 talked about. As far as EGT vs ITT, it all depends on where the designers decided to stick the probe (STS). For the T-56 that's on the Herc, it was at the turbine inlet (TIT), PT-6 it was around the interstage point (ITT), J-69: you get the picture.

PMU: sure, what C17wannabe said...

[Mild]

N1 = speed of the engine in percent of max rpm

Np = speed of prop in percent of max

PMU = is the brains of the engine controlling fuel, engine, prop, . . .

ITT what others have said

[Guest mchollar]

You're gonna love the PMU. It won't let you overtemp or overtorque the engine. Plus it monitors the start sequence for you and kills the engine if something goes wrong.

Not the case with other turbo props.

[Guest ChrisC]

doesnt ITT = TIT .. turbine inlet temp...

[HerkDerka]

ITT and TIT are actually two different things.

Although both are engine temperature readings, they are measured in different places.

The T-44 used ITT (Interstage Turbine Temperature) because the thermocouples were located between two stages in the turbine section (That might not be spot on, I've forgotten almost everything about the Peg's engine). Regardless, ITT is measured between the turbine stages.

TIT (Turbine Inlet Temperature) is measured prior to the turbine section and after the combustion section. TIT is what you'll find on the Herc.

In others words, both are heat readings, but just measured in different locations. The place where the heat is measured changes from engine to engine.

HD

[ 27. May 2004, 18:27: Message edited by: HercDriver24 ]