Turbo Ops -- UGH!

[gismo]

I believe that's been shown (by testing) to be the wrong approach in most situations. If you are at low power on approach, and you don't run at high power during taxi, the turbo should be as cool as it will get when you get to the ramp.

At best, it does nothing. At worst, running at idle for five minutes wastes fuel, delays your trip, and can increase temps.

If I owned a turbocharged airplane I'd install some means of indicating the temp of the turbine in the cockpit. That way I could tell whether or not additional cooling time was needed or effective after landing in any conditions.

 

[Ted]

If I owned a turbocharged airplane I'd install some means of indicating the temp of the turbine in the cockpit. That way I could tell whether or not additional cooling time was needed or effective after landing in any conditions.

Furthermore (at least on all the turbocharged Lycomings that I'm aware of) the exhaust temperature limit is on the TIT (Turbine Inlet Temperature).

Although it should be noted that on certain aircraft, the TIT probe location is actually not at the turbine inlet. The Lycoming-powered Malibu is a good example, which has the TIT probe located at the wastegate (twin-turbo engine, single wastegate).

 

[bbchien]

Tom's right. I've got an IR gun (a EXTECH). The turbo is about 280 degr F when I shut it down and jump out to point at it. It's the same if I idle for three-four minutes.

I have Merlins and below 5000 the wastegate is always wide open. The last six to eight minutes, it's not compressing anything.

 

[weilke]

I believe that's been shown (by testing) to be the wrong approach in most situations. If you are at low power on approach, and you don't run at high power during taxi, the turbo should be as cool as it will get when you get to the ramp.

What has been shown is that TIT and oil-temp are the lowest at the time of touchdown and that it slowly rises while taxiing to the ramp.

I have not seen data that shows the temperature of the shaft at the level of the turbine side bearing over time. While the assumption that TIT is reflective of that temperature may be correct, I have reasons to believe that that may not be the case (heat stored in the turbine rotor combined loss of heat-sink effect from the circulating oil).

 

[Clark1961]

I have not seen data that shows the temperature of the shaft at the level of the turbine side bearing over time. While the assumption that TIT is reflective of that temperature may be correct, I have reasons to believe that that may not be the case (heat stored in the turbine rotor combined loss of heat-sink effect from the circulating oil).

The turbo housing is much more massive than the rotor. It's temperature will dominate the temperature of the internal components after shut-down, e.g. the equilibrated temperature will be very close to the housing temperature shortly after shut-down.

 

[weilke]

The turbo housing is much more massive than the rotor. It's temperature will dominate the temperature of the internal components after shut-down, e.g. the equilibrated temperature will be very close to the housing temperature shortly after shut-down.

Has that been shown in an experimental setting ?

It would be 'common sense' to be correct.

 

[alaskaflyer]

Remember that John wrote the Pelican's Perch series of articles several years ago. He now says that he (and the GA community) has learned some things that change a few of his recommendations since writing PP.

Those changes are incorporated into the APS online course, which is an incredible value, in my opinion.

Really, the APS course is an eye-opening experience for anyone running a large, piston aircraft engine, regardless of whether you have an engine monitor, injectors (balanced or not), or how you run your engine.

Nice to see you back on the board.

Any opinion about the WOT question a few posts above? I seem to remember you writing a while ago that you operate your Bonanza WOT in all phases except descent to land.