In a message dated 2/14/2003 10:04:54 AM Pacific Standard Time,
terrys@cisco.com writes:
> t message posted by: Terry Seaver <terrys@cisco.com>
>
> Hi all,
>
> I have also heard of Bill Lockwood's opinion that the gear box can suffer
> damage
> if the idle is set below 1800 rpm. I have a few thoughts on that subject.
>
> 1. Even at 1400 rpm idle setting, the Rotax/Europa recommended idle speed,
> the
> plane tends to float a little on landing (we have a short wing XS with 912S
> and
> Whirlwind CS prop). At 1800 rpm idle setting (we tried this ONCE, after
> speaking
> to Bill L.) the airplane becomes difficult to get down, a potential safety
> concern, IMHO. We are currently set to a compromise of about 1600 rpm. The
> engine
> idles fairly well and the plane eventually returns to earth at idle (except
> on
> those pesky runways with some down slope).
>
> 2. Does a gear box that can be damaged this easily belong on any airplane?!
>
> 3. I have a Honda 919 motorcycle (four cylinders, 919 cc, 115 hp at the
> crank)
> with virtually no flywheel and a very light crankshaft. It idles quite well
> at
> 1200 rpm, immediately on start-up! Why is it that a longer stroke Rotax,
> with a
> flywheel, cannot be made to idle smoothly below 1400 rpm (or 1800 rpm,
> according
> to Bill L.)? Is this 'rocket science' too much to expect in a 'modern'
> aircraft
> engine? I suspect an ignition system with centrifugal advance (or
> electronic
> equiv) and electronic fuel injection might help.
>
> We have 250 hours on our engine now. Less vibration and noise at cruise
> would be
> greatly appreciated, so we will be trying the softer mounts soon. If the
> Rotax
> engine/gearbox craps out because of this, maybe we need to start looking at
> an
> engine swap with my bike.
>
> BTW, we have had our prop dynamically balanced three times, and have
> adjusted our
> carbs with a solid state differential pressure transducer in place of the
> balance
> tube. We adjusted with the cables at high throttle settings and with the
> idle
> stops at idle.
>
Terry,
Very well said! I heard of some guy working on a new ignitions system for the
Rotax that will eliminate some of this discussion. I would be very interested
in this. You can't believe the difference in the smoothness and sound of
these mounts. My radios and electronics will thank me for this change!
'
Dave
|