Max RPM, and other things

[NoahBryant 26]

Okay now that I have delved into the plane I have some questions. Since there is no tutorial or systems manual, hopefully you guys can help me out...Cruise PerformanceLooking at the performance charts, they all indicate 2200 rpm. 2200 rpm is what I get when the prop level is full forward. Is that normal? If so, when would I ever do anything at all with the prop level except in an abnormal situation or when shutting engine down?Fuel Pressure:It always reads 6.0 is that normal?Flight Timer:Only one button works and all it seems to do is switch between two different times, neither of which makes sense. Any ideas, right now it says 1: 8 0 :31?Oil Door:What is it for (Cooling?) and when do you close it? I see in the Norm. Procedures to open it prior to take off, but it never says when it should be closed.Fuel GaugesThe needles don't match the digital readout, a bug?Where isAlternator switchFuel Firewall Shutoff LeverFuel boost pump (is that the one next to the starter?)What isSlaving SystemOverspeed Governor TestIce DeflectorGround Clear Switch

[Yoda967 23]

Noah,The only time you would normally have the props at max RPM is when the gear is down...takeoff and on final approach. After takeoff, you should pull the prop back to 2050 rpm. The technique I've seen recommended is to takeoff with 1000 ft/lbs torque and max RPM, then once the gear and flaps are up, pull the prop back to 2050 rpm and increase torque to 1200 ft/lbs for the initial climb. Keep in mind the ITT red line of 690 degrees C, and don't exceed that. As you climb, the torque will fall off, so advance the power lever to maintain 1200 ft/lbs (or as close to it as you can get without exceeding the ITT limit). Climb at 140 KIAS, adjusting power as I've described, and controlling airspeed with pitch or by adjusting the vertical speed on the AP. At cruise altitude, you can come back on the torque to between 600 and 900 ft/lbs. Economical cruise is always going to be 600 ft/lbs torque, but in the real plane, the cabin heat and defrost run off the engine so at higher flight levels, you'll be more realistic if you run at 800-900 ft/lbs.Leveling off in cruise, keep in mind that the faster the prop is turning, the more noise it makes, so you will want to pull the prop rpm back. This will give you a speed increase, and decrease fuel consumption...like putting your car into a higher gear. Watch the engine limits as you change things, and keep the torque at the desired cruise power. Also, watch the airspeed and don't exceed the red line on the airspeed indicator. Descending with a turboprop is really easy -- you pull the power back as far as you want and descend. It works well if you pull the torque back to 500 ft/lbs and control the airspeed with pitch. You'll have to adjust the power lever to maintain 500 ft/lbs as you descend, but you'll have your power set for the approach when you get down to the IAF. Bernt will have to chime in on this for the Carenado P46T as I haven't tested it yet, but in a real turboprop, pushing the prop lever full forward while descending is like popping open a big speed brake. I've read that you can get as much as 4,000 fpm in the descent in the P46T this way.There's a lot of helpful info at www.pa46t.com.The only other question I'll address is the ice deflector: The PT6 air inlet is actually at the rear of the engine, so there is a bend in the air intake duct. At the bottom of this bend, there's a door to the exterior that can be opened and closed, and inside the duct, a vane that can be extended to further "bend" the air flow in the duct. When the vane is extended and the door open, any particles (like ice) will be deflected out the door instead of passing all the way to the engine inlet. It's pretty common practice to run with the ice deflector on/open while taxiing to help protect the engine from FOD. When the deflector is on, you should see a decrease in power, since the volume of air going to the engine inlet is reduced.

[Guest bstolle]

Hey Kurt, thanx for the extensive and brilliant explanation.Most videos I've seen and the very informative link you posted mention 400ft-lbYes, with the throttle at idle a free turbine like the PT6 produces a lot of negative torque and drag. The prop RPM isn't such a big factor on the JetPROP, because the minimum blade angle in flight is a rather high 20deg.BTW, I didn't know this link and of course I had to test this high rate descent thing immediately, result..... -4000fpm at 170kts...

[NoahBryant 26]

Thanks so much for that Kurt that was a great explanation, pulling the RPM back to the 2050 range for cruise is what I have become accustomed to in other planes so that makes more sense. Why then, is 2200 RPM listed in performance charts (for both the real plane (DL) and the Carenado one). Further checking led me to different (RW) performance charts that listed 2000 RPM in the DLX model of the plane. Not sure which model Carenado modeled though. Not sure what use performance charts are that only list performance for max RPM.

[Yoda967 23]

Noah, You can, of course, cruise at max prop RPM, but the noise would be uncomfortable. I believe Carenado modeled the DL with the PT6-21 engine. Bernt, I bet that 4000 fpm descent felt good...looks like you got a lot right on this flight model. (Personally, I love the takeoffs -- pitch is highly controllable without "yanking", and then you have to crank in quite a bit of nose down trim to manage the climb out, which is exactly what the owner in that link says he has to do.) I can't WAIT to see what you've done with the C90!

Edited January 13, 2012 by Bob Loblaw

[fritzreinhart 0]

Thank you much, Kurt! I am a complete novice when it comes to turboprops and your explanation of the relation between power and pitch has been very helpful. I must admit that I still have a problem with contolling my airspeed with the propeller pitch. I don't understand it all, quite yet, maybe. I can't slow down by changing the prop pitch. Only the power lever seems to work. I know I'm doing something wrong, chaps, but I don't know what it is. All help will be appreciated as will any clever remarks.Cheers,Fritz

Edited January 13, 2012 by fritzreinhart

[Guest bstolle]

Fritz, the minimum blade angle is to high with 20deg to achieve a significant braking effect when compared to the maximum blade angle. I think the max blade angle I've seen during testing was around 30-35deg.20deg as a minimum is very unsual, e.g the C90 has 12deg. To slow down just slam the throttle closed. The PT6 doesn't care at all.If you want peak performance you can keep 2200RPM all day long. Any further questions, just ask and you will be proficient until the C90 arrives :(

[scottb613 1,186]

Man - now this is the kind of dialog I like... Sounds encouraging folks - also appreciate all the detailed information... One of my favorite planes to date has always been the DA Cheyenne... Hopefully - this one will unseat her... :Big Grin:Regards,Scott

Edited January 13, 2012 by scottb613

[Yoda967 23]

Just to be clear, when I refer to "pitch", I'm speaking of aircraft nose up/down pitch and not prop pitch. :-)

[bliksimpie 1]

thank you kurt for nice explanation

[Guest bstolle]

One of my favorite planes to date has always been the DA Cheyenne... Hopefully - this one will unseat her...

Don't think so....that will be the job of the C90! :(

[Yoda967 23]

Don't think so....that will be the job of the C90! :(

Yeah, you don't ever want to trade two engines for one. :(

[fritzreinhart 0]

Fritz, the minimum blade angle is to high with 20deg to achieve a significant braking effect when compared to the maximum blade angle. I think the max blade angle I've seen during testing was around 30-35deg.20deg as a minimum is very unsual, e.g the C90 has 12deg. To slow down just slam the throttle closed. The PT6 doesn't care at all.If you want peak performance you can keep 2200RPM all day long.Any further questions, just ask and you will be proficient until the C90 arrives :(

Many thanks, Bernt. This really is a beautiful airplane! Cheers,Fritz

[Yitzhak 0]

The alternator is the STBY ALT switch.I actually learned quite a lot from this video:

*Note: STBY ALT function doesn't seem to work in this version. Edited January 14, 2012 by Yitzhak

[demuss 2]

At the risk of being considered a nitpicker here is my list of things that don't seem to work as expected (from left side of cockpit to right).1) ICE DOOR switch INOP2) GROUND CLEAR switch INOP3) L/R FUEL QTY gauges, pointer does not match digital readout (digital readout does seem correct)4) LANDG LIGHT / TAXI LIGHT function not correct (at least according to a JetProp DLX manual): LANDG LIGHT should control the single lamp on the nose gear, not the wingtip lights. The wonderful world of Piper considers the wingtip lights the TAXI LIGHTS, so the TAXI LIGHTS switch should control them. Also, if the PULSE function were implemented on the TAXI LIGHTS switch they could be used during climb and descent as recognition lights, as I believe they are in the real airplane.Having said that I am having a ball with this airplane! I do hope Carenado will consider fixing these minor issues that detract just a little from what is very close to (and in fact could be with a couple of fixes) a perfect add-on aircraft.