Hi all,
A couple of things. First, I'm too busy, articles, video editing, things are
getting neglected, like my parents and friends. Lots to do before I return to
America in January. My own fault so I try not to complain.
I read a lot of the comments on Krnet.
There seem to be a few repeating issues that I thought would reply to.
Engine reliability.
Non of them are. I wouldn't expect any light aircraft engine to do more than
500 hours without a good look over. I looked at one of my exhaust valves while
repairing a leaking exhaust gasket. It looked rough, hardend plating corroded
and cracked at base at 300 hours. I replace my exhaust valves each 300 hours
now. If you don't, they will brake, or stick or both. Temps are vital, it took
a long time to make sure my engine doesn't even get hot.
Its not really the engine or designers fault. Its operating conditions,
operators and maintenance. I've read many of the reports of the jabiru engine
failures and sort of knew why most of them had happened.
Lets get real. The Jabiru engine has had next to know research or development.
During the early days, the owners were doing it. I learnt quickly about 5 vital
things to look after my Jabiru, by seeing what happened to the operating
parameters, temps pressures when various operating conditions were applied.
None of them have ever been added to any news letter or information advice from
the manufacturer and I've given up telling people now. No one listens.I even
was asked to write an article for our society about Jabiru engines. I entitled
it, "Jabiru engines and what they won't tell you about them!" Highlighting
about 10 issues, 5 I though vital for safe operation of the Jabiru engine. They
never published it,said it was too inflammatory and open to the layers...
I know people will now say that they have had thousands of trouble free use
from their engines, well all I can say to that is that , you are either a
diligent operator and maintainer, or you have been lucky.
The Rotax engine had a lot more development thrown at it, and you have to pay
for that in the cost of the thing. Get what you pay for... The Jabiru engine is
expensive as well, that's because you are paying for a decent power to weight
ratio. That's all.
Its no good really. Its still too delicate. I use it though, but monitor it and
all four egt and cht parameters rigorously and check heads and tappet
clearances for signs of change or deformation regularly. Seems to keep going.
But I don't like it. I would love to buy one and not have to think it was ever
going to quit for 2,000 hours as they say, but its a joke... Not funny when
they do break and seemingly they do. Anyway...
Next, speed brakes. A KR needs to be light and none complicated if it is going
to perform well. I haven't got flaps or a speed brake. You don't need them.
People keep saying that "They float!" How? Its got tiny wings! The problem
mostly seems to be that people need a high throttle position to keep their
poorly idling engines going on the ground at say, 700 rpm. This unfortunately
turns into about 1,400 rpm in the air. No wonder it floats, thats still about
1/4 throttle. If you remove the idle stop for your engine all together, if you
close the throttle completely, it now acts like a exhaust brake. The engine
will never stop in the air, it just windmills at 500 rpm causing massive drag
and the aircraft stops and falls out the sky. When you land and the idle gets
lower as they airspeed decreases, just crack a little throttle back on. So
don't worry about how many holes to put in your speed brake, save yourself a
lot of time and weight and complication and use the prop as a brake instead.
This only works if you have a starter motor, I've accidentally let it stop once
or twice out on the taxi way. But its safer too. No panic trying to find mag
switches or trying to turn mags switch keys, if a dog runs out, as has happened
to me. Just pull the throttle, which your hand is on anyway and it stops.
More ways to skin a cat, which is a funny saying we have here. I'm not telling
anyone anything or want any reply or discussion with this message. I'm just
saying what I do and saying that if you haven't tried it, give it a go. If it
works for you too, brill, if not well, I reckon holes add to drag. About 20 two
inch holes should do.
Keep an eye on those engines, if you have a worry, you are probably right and
you should take a look, it never hurts.
Best regards,
Colin Hales.
