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Thread: King Air C90 approach procedure...?

  1. #1

    Default King Air C90 approach procedure...?

    Hello all... I've never flown turboprops or jets (for real or in flight simulators) and I'm having a hard time setting a (Carenado) King Air C90 for approach (FS2004, but my question is really about "real" flying). Basically, I can't get the thing to slow down... I ease the throttle on level flight (cruising at around 170 KIAS), and start trimming for descent at 160 KIAS, aiming for 1500 fpm descent as per a C90 performance reference manual that I got on the internet (PDF). The manual has a descent chart (fuel/time/distance) defaulting to 169 KIAS / 1500 fpm. Yet, no matter how much I pull back the throttle, at that descent rate the plane speed goes over 180 KIAS (overspeed at certain altitudes). Moreover, if I ease the throttle too much, I start getting "low oil pressure" warnings, so I'm at a loss at how to maintain 169 KIAS at a 1500 fpm descent rate without damaging the engine (?)... I've tried fiddling with the propellers' RPM (2000 - 1700), to no avail... Any advice about the proper procedure to slow down turboprops (or the C90 in particular) for approach greatly appreciated...!

    P.S. In another forum (reddit) someone suggested getting "flaps down". I was going to write an annoyed reply saying that if I was trying to slow down from cruise speed, the speed obviously would be much higher than Vfe... Yet, before I replied, I wisely googled up what was the Vfe for the C90, and apparently it is 184 KIAS (!!) for flaps set to "approach"... So, are flaps down set to "approach" the way to slow down the C90 to its reported 169 KIAS descent speed and keep 1500 fpm...? Thanks in advance for your advise and help on this!

  2. #2
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    Default

    but my question is really about "real" flying
    Just so you know, this probably would fit better in the FS2004 forum. Though I don't know the answer you're after, since I rarely use turboprops in the sim and have never flown a real one, I can say that the flight models in the sim, especially the default ones, are often not as realistic as they might be. It's very difficult and time consuming to change aircraft behavior to duplicate real world performance, so they often settle for a rough approximation, sometimes VERY rough. And I know that all of my Carenado aircraft, though better than the default ones, still are far from real behavior in some areas.

    But in general, for initiating a real world descent if you need to slow down, you would ease back on the power in level flight, slowing to your desired descent speed, then adjust power to maintain EITHER the desired airspeed OR the desired descent rate OR just accept the rate of descent the new power setting gives you at the desired speed.

    But be advised that it's not unusual in the real world to just ease the nose down, accepting a higher speed ("trade altitude for airspeed") while adjusting the power to keep airspeed below the yellow arc in rougher air or below redline in smooth air, letting the descent rate take care of itself, unless ATC would specify something that you need to follow.

    One other thing you could do is to use ADE to modify the drag in that aircraft (maybe even in the aircraft.cfg file -- I no longer have FS2004 installed so I can't check) but that can cause other problems, so a lot of time, trial and error would be needed to properly accomplish that.

    Larry N.

    As Skylab would say:
    Remember: Aviation is NOT an exact Science!

  3. #3

    Default

    Quote Originally Posted by lnuss View Post
    Just so you know, this probably would fit better in the FS2004 forum. Though I don't know the answer you're after, since I rarely use turboprops in the sim and have never flown a real one, I can say that the flight models in the sim, especially the default ones, are often not as realistic as they might be. It's very difficult and time consuming to change aircraft behavior to duplicate real world performance, so they often settle for a rough approximation, sometimes VERY rough. And I know that all of my Carenado aircraft, though better than the default ones, still are far from real behavior in some areas.

    But in general, for initiating a real world descent if you need to slow down, you would ease back on the power in level flight, slowing to your desired descent speed, then adjust power to maintain EITHER the desired airspeed OR the desired descent rate OR just accept the rate of descent the new power setting gives you at the desired speed.

    But be advised that it's not unusual in the real world to just ease the nose down, accepting a higher speed ("trade altitude for airspeed") while adjusting the power to keep airspeed below the yellow arc in rougher air or below redline in smooth air, letting the descent rate take care of itself, unless ATC would specify something that you need to follow.

    One other thing you could do is to use ADE to modify the drag in that aircraft (maybe even in the aircraft.cfg file -- I no longer have FS2004 installed so I can't check) but that can cause other problems, so a lot of time, trial and error would be needed to properly accomplish that.
    `Go down` or `slow down` is par for the course for most turboprops. One can always try controlling the props - it doesn't work on most Carenado product because their ignorance is matched by their ego. In this case Go for ``slow down` first, then deploy flaps and gear at appropriate speeds.
    Try asking Carenado how their `real` pilots do it - Don't wait for their reply though.

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