Hi Jonathan,
Thank you for your interesting and informative emails regarding idle
speed for tailwheel Europas. It is certainly true that tailwheel Europas
will float if too much prop thrust remains. However, if one has a
constant speed prop it does change the picture.
I have just returned from Sun N Fun in Florida - an enjoyable trip with
no problems in the trusty Europa. 1100 miles round trip as the crow
flies, using 45 US gal of 100LL. Trip down was somewhat below the scud
but never below 1,000 ft agl. Stop was in Georgia at Brunswick on the
coast. Coming back, I had to bob and weave to dodge some showers and
rain but it soon improved to clear blue and this time I stopped at
Waycross in Georgia to fill up. Waycross is just north of the Okefenokee
swamp which is a large national park with lots of alligators!
Anyway, getting back to idle speed. Before the trip I had just finished
my annual and had replaced my throttle cables with solid music wire. I
carefully set the idle speed and full throttle with the mechanical
adjustments as per the Rotax procedure and followed Lockwood Aviation's
recommendation of not less than 1,800 rpm which is about where I had it
previously. (Lockwood is a big Rotax dealer here.) On this occasion, I
did not do the pneumatic synchronisation. However, the engine ran very
smoothly. Most of the landings on the trip were in less than perfect
conditions but I did not have any problem with float. I normally come in
over the numbers at ~55 kts and when I close the throttle at the flare -
it lands. With a large passenger and a load, it emphatically lands.
I suspect that the big difference between your experience and mine is
the constant speed prop. See
http://www.whirlwindaviation.com/series100.php During landing, the prop
is set fully fine for max thrust in the event of a go-around. In effect,
it acts almost like an air brake when the throttle is closed. I noticed
that when I had the idle set at ~1,500 rpm on previous occasions, the
a/c used to fall out of the air quite rapidly as I rounded out at the
flare. For this reason I usually leave a little power on at the flare to
smooth the contact. Incidentally, there was a very nicely finished new
tri-gear at the Sun N Fun stand which had the same type of Whirlwind
prop which uses a hydraulic governor for control.
Wishing you many more smooth landings.
Cheers, John
N262WF, mono XS, 912S, 590 hours
Mooresville, North Carolina
ORIGINAL MESSAGE
From: Jonathan Milbank <jdmilbank@hotmail.com>
Subject: FW: Europa-List: FW: Rotax idle speed. Tailwheel Europa
Well, there it is folks. Andy Draper's reply below must be the last word on this
matter. I don't want to be guilty of suggesting something against the
manufacturer's
recommendations. Just because my experience with the way I adjust and
operate my engine is satisfactory, it doesn't follow that others will enjoy the
same benefit.
Do it by the book and no-one will be able accuse you of irresponsibility.
Sincerely.
Jonathan
Subject: RE: Europa-List: FW: Rotax idle speed. Tailwheel EuropaDate: Mon,
Hi Jonathan,
It is relatively rare to find a Rotax engine that will idle happily at below
1200
rpm, in my experience, even with balanced carburettors, so we would always
set the idle speed to be around 1500rpm (between the recommended 1400-1600rpm
band) on our demonstrators. This enabled us to operate the aircraft without
excessive
float, but I guess that we all just got used to that set up.
I would expect that gear box wear will be accelerated if the slow idle is
'chattery'
but if it's smooth and especially as you minimise the time at slow idle,
then you probably won't suffer excessively. I'm not sure, though, that I would
want to go into print to recommend others to set their engines up similarly
to yours if it contravenes what the manufacturer says.
Best wishes
Andy
From: Jonathan Milbank [mailto:jdmilbank@hotmail.com] Sent: 14 April 2008
10:27To: Andy DraperCc: editor@europaclub.org.ukSubject: FW: Europa-List: FW:
Rotax idle speed. Tailwheel Europa
Hello Andy, The emails below are for your interest and comments, if you have
any.
If not, then I'll go ahead and submit an article to "The Europa Flyer". Maybe
I'm going over a subject which has been dealt with before, in which case I
apologise. Should you spy any traps for the unwary in what I'm advocating,
please
let me know. Thanks. Jonathan
From: jdmilbank@hotmail.comTo: europa-list@matronics.comSubject: Europa-List:
FW:
Rotax idle speed. Tailwheel EuropaDate: Sun, 13 Apr 2008 22:45:10 +0000
Pilots/Owners of tailwheel Europas, My email to Conrad Beale and his advice that
I should post these communications on the forum are set out for you below. The
four of us who have been flying G-EIKY since 1997 (865 hours in tech. log)
have no problem in remembering never to allow the engine to idle below 1500 rpm.
In fact after starting we use the throttle to maintain warm-up above 2000 rpm
and don't taxi below 1500 rpm. Only briefly after checking the ignitions do
we pull the throttle all the way back for a couple of seconds to check slow
running
around 800 rpm before commencing take-off. On
rounding out for a landing, the throttle is closed fully until the landing roll
is completed and re-opened once the aircraft reaches a safe taxi speed. Thus
the percentage of time that our engine spends below 1500 rpm is almo
st negligible. I learned to fly on Harvards 40 years ago and clocked 274 hours
on that type. The combined experience of my fellow group members on tailwheel
machines totals in the 1000's. All this might not make us any safer than others
with less time in tail draggers, but I certainly wouldn't have been wanting
to land any such aircraft in a crosswind with the engine idling quickly. Get
squarely
in contact with Mother Earth a.s.a.p. after rounding out is my fervent
hope and intention! If anyone has comments or criticisms, I'd be grateful for
your input. Thanks. Jonathan
From: louise@conairsports.co.ukTo: jdmilbank@hotmail.comSubject: FW: Rotax
912/914 idle speedDate: Tue, 8 Apr 2008 18:58:06 +0100
Jonathan,
Thank you for your comments regarding the article. I am grateful for your
feedback,
especially about the idle speed, and I understand your concerns. As you are
aware the gearbox wear will be a problem if the idle speed is too low. I can
see you have accepted this as a consequence for your set up, but you benefit
---From an aircraft that is easier to keep on the ground. Normally it is
difficult
to achieve a stable speed below 1200, and the engine will often stop if set
any lower. Rotax suggest 1800RPMI think your experience would be of benefit to
other (if you were to post it on the Europa (Matronics) forum), but it needs
to be backed up with the warning about increased risk of engine stoppage and
increased gearbox wear t
hat will ensue.
I will bear your comments in mind when I am working on installations that might
benefit from our feedback in particular the mono wheel Europa..
Regards Conrad Beale ConAir Sports Ltd www.conairsports.co.uk ONLINE SHOP +44
(0) 1295 771088
From: Jonathan Milbank [mailto:jdmilbank@hotmail.com] Sent: 08 April 2008
10:23To: service@conairsports.co.ukCc: mo@moragjones.demon.co.ukSubject: Rotax
912/914 idle speed
Hello Conrad, I thoroughly enjoyed reading your very helpful, clear and valuable
articles on servicing Rotax engines and I look forward to the next one. Now
I'm going to take the risk of slightly contradicting something you wrote and
hope
you won't think too ill of me. I know that your articles and advice are not
aircraft type-specific, but idle speed is a sensitive issue with Europa
mono/tailwheel
aircraft during the touch-down phase. With its laminar flow wing and
slippery profile, the Europa mono is a bit notorious for departing from the
runway against the pilot's wishes and efforts. It wil
l float after rounding out and can easily "balloon" upwards if just a little
wind
gust should happen. Once the Europa is squarely planted on the ground with
the stick held fully back and the tailwheel solidly gripping the surface, then
it is easy enough to keep it running straight. It's during the tricky period
between raising the aircraft nose to round out and getting well settled on the
runway that directional control can be awkward, particularly in a crosswind.
Therefore it follows that this period of floating above the surface must be kept
to a minimum. A fast idling engine will exacerbate
any problems. I keep the carburettors adjusted so that at full engine operating
temperature and with the aircraft standing still in nil wind, the idle is around
800 rpm and the engine is on the verge of cutting out. Of course this means
that the engine is safely idling at around 1200 rpm with the throttle fully
closed while gliding. We who belong to the group that flies this Europa are all
fully aware that allowing the gearbox to clatter at low rpm on the ground will
drastically shorten its life, so we always set the throttle to keep the rpm
above 1500 after start up and when taxying. Possibl
y the reason why our monowheel Europa has survived relatively unscathed for 11
years ( touch wood ) is that we are nearly all professional pilots with a lot
of general aviation experience and tailwheel experience. But we all also
appreciate
the importance of minimising the floating period after rounding out for
a landing. Thanks for your superb contribution to better understanding the
maintenance
of our engine. Sincerely. Jonathan Milbank
|