Airborne Avid
Short
finals for NZFI 10
At last, after 10
months and nearly 700 hrs of work, JHW was ready to go – well almost. I had to add the water, oil and fuel, and
make sure they and the electrons went in the right places at the right time. I
was about to learn yet another lesson…
I’d arranged hangarage at Fielding and been made most welcome by the
Manawatu Microlight Club, which I’d joined some weeks before. It’s a great
bunch of people, with a positive outlook, good facilities and well worth the
two hour drive from
Finally, a Saturday
arrived when I could at least run up the engine and check out the various
systems. Roger Dixon and John Varley again helped,
abused and cajoled. All the fluids were in, we were ready to go.
STRIKE ONE
The first job was to
make sure oil was getting to the engine, as the long break and disconnected
lines meant that the galleries and pump were empty. Now the fun really started.
We decided to pull the engine through by hand to prime the pump. After 20 min,
much sweat and tired arms, nothing had happened. We loosened the connections at
the engine (uphill end), and used 5 psi to blow oil
from the tank to the engine, then tightened it all up and cranked again. Still nothing. This time I removed the feed line to the pump , set up a funnel and poured/cranked in 500mls.
Reconnect the line, hand crank and - bingo – twitches on the pressure
gauge. Right – time to do it properly. Fuel taps on, electric pump on for 15
sec, then off as it loaded up, full choke , a few turns and at last JHW was
alive again – then horror , the oil pressure dropped down below 20 psi – switch off.
New diagram Old
diagram Note lower sketch
We tried again – same
result. After an afternoon of frustration and zero progress, I went home to have
a break and a rethink. We’d followed the manual with the installation,
pre-filled the lines and pump, and still both lines would be empty after a 10
second run. The solution came from an unexpected direction. I’d been working
from the July1998 manual that came with the plane. In section 9.3 on the
lubrication system, there is a nice front view drawing of the engine, oil
cooler and oil tank. The tank detail shows that the angled tube is the feed,
and goes to the bottom of the tank, while the vertical tube is the return. BUT
when I looked through the ROTAX CD, at home on the computer, I found a nice
isometric sketch that showed the top of the tank with the tubes reversed. The
angled one was the return, and the vertical one the feed. The difference is
that the front projection diagram in the 98 manual showed the VERTICAL COMPONENT
of the angled tube, and the ANGLED COMPONENT of the vertical tube.
Had the diagram been drawn from 90 deg around
the correct relationship would have been obvious. The new CD has a nice
perspective sketch which clears this up instantly. I can only assume I’m not
the only one that had been caught!! I’d also used a generous amount of oil, so
there had been enough to just start to fill the wrong line from the tank, get a
pressure indication, and then start the engine and blow it back the wrong way.
John Varley and me on the
way to Waipukurau
The next weekend we were up there full of enthusiasm, 10 min to reverse
the connections and JHW was fired up, oil pressure excellent, and I proudly
taxied around to the MMC club rooms.
STRIKE TWO
After a number of club
members had had a good nosey around, and Bill Penman had reassured me for the
tenth time that I was quite capable for the test flight, I started up and this
time got as far as mag checks. On each side , a
massive 1000 rpm drop, and exactly the same feeling rough running. Back on both,it ran sweetly. R or L alone and 1000 down, lotsa shakes. What the hell was going on? Off with the
cowl, pull plugs – all nice. Make sure the plug leads were firmly on, check the
connections on the back of the switch – all correct and secure. Run up – same
result. I had run out of ideas, so I asked John Bolton-Riley to have a look
around, while I took a student in the Xair. I figured that a change of pace
might help and a new brain looking at the wiring might be useful. Trouble was,
I picked the brain with the most sadistic lack of tact in the club. JBR was
waiting with a big grin after I emerged from the Xair some 40 min later. The
conversation went something like this…
JBR – “Havill – you’re
a school teacher, right? “
PJH - (with some trepidation) “Yes”
-
“Do you
know how to count??” (sadistic grin, and knowing leers from those within
earshot)
-
“er – yes” (Why the
hell did I ask him? )
-
“ go and
look at the numbers on the HT leads” (evil laughter)
I did . I’m dumb –
REALLY dumb. The top leads on #2 and #4 were reversed. ARRRGGGHHHHHH! <insert
your favourite language here>. I reversed them.
The engine ran sweetly. Mag drops were minimal. The
club was entertained greatly, and strike three began polishing its’
opportunity, shortly to be employed.
At last the time had
come, and I was about to test fly my beautiful rebuilt Avid. I’d dreamed of
this day for months, and here we were, all problems fixed, a lovely day,
supported by club mates capable of the highest and most thoughtful levels of
personal abuse. It doesn’t get much better.
“Post JBR”
mag check (Photo Bill Penman)
STRIKE THREE
I fired up, checked
everything about three times and taxied for 28 grass. The radio worked well,
noise canceling headset was great, etc – all sweet. I called “Fielding traffic,
Juliet Hotel Whiskey lining up 28 grass for test flight”, turned onto the
grass, took a deep breath and open the throttle. It worked! We had a reasonably
straight, slightly protracted take-off. All the numbers looked good, and the
Avid flew well as I tracked around the circuit and called the traffic to advise
I was climbing to 1300’ overhead the field for 20 min. My plan was to orbit
overhead, look for stable temps, feel out the plane and generally get my feet used
to the rudder pedals again. This was going to need some practice, as the ball
slammed from one end to the other. I decided to stop trying and lo and behold,
it stopped ricocheting around the panel. After about 12 min, the third strike
surfaced. I heard a PHUTTT sound from behind the panel, and white smoke poured
out and rapidly filled the cockpit, IFR with the cloud enclosed in the cabin!
It stunk horribly of burnt paxolin. The first priority was fly the plane.
Everything was still working so there were no worries there. A brief crack of
the door cleared most of the smoke, and I called “Fielding traffic, Juliet
Hotel Whiskey has smoke in the cockpit. Joining downwind and expediting
landing”. Bill Penman immediately replied to check that I was OK, and then left
me to get on with the somewhat abbreviated circuit and landing. I hadn’t called
PAN PAN PAN because I was already at the right place, and the fault had not
caused any difficulties in the handling of the plane, nor had it affected the
running of the engine. As I descended to my brief circuit, I thought about what
was behind the panel and decided it was almost certainly the large 22000 microfarad
capacitor that smoothes the voltage regulator output. For some reason it had
spat the dummy. I decided that fire was unlikely as the smoke had come with
sound effects, then no more - yes it had to be the cap.
Landing was
uneventful, and on return to the club room, and removing the upper cowl, we
found that the cap had indeed blown, spraying evil smelling yellow muck all
over my nice neat wiring. My voltage regulators had protected apparently
protected the radio, comms and GPS from any spikes,
so all there was to do was to cleanup, remove the cap and organize another.
I tracked down a
replacement from 
After the big smoke
First of all, several
people told me that electrolytic caps, if left for a long time with no voltage
applied, can suffer degradation of the dielectric layer. When powered up again,
they can “cook off” as mine did. The other contributing factor was that the
maximum working voltage of the capacitor was 25 V, and the regulator can put
out 33 volts (no load), so really at least a 35V, or preferably 65V rated
capacitor would be indicated. The remaining unknown was that in the process of
cleaning up the mess, I’d disconnected the “alternator disconnect” relay and so
later, when re-installing, was unable to be sure that my problem had not been
caused by a mistake in connecting the relay to join the output of the rectifier
to the battery (load). This system is needed to prevent the battery from
discharging through the rectifier and alternator when the engine is off (
aircraft is left in the hangar for a week or two –flat battery).
Whatever it was, the
replacement works OK and all seems well now.
LESSONS (RE)LEARNED
Always, always, always
arrange for another brain to cross check your work. Especially, arrange for
them to take the time for a thorough, leisurely and undisturbed check of
electrical, fuel and oil systems. Where I got caught was that many friends had
looked over my work as it had progressed, helped, fixed problems and been
involved in very knowledgeable ways. Each part of each system was checked, but
only one brain looked at the whole thing, and that had been too close for too
long. The Annual condition inspection given prior to flight was thorough and
picked up a few split pins, washers etc as such inspections go, but not any of
the more tricky permutations that surfaced as we tried to get JHW airborne. Nor was it the function of such an inspection.
What I was pleased about was that when something went wrong in the air, I FLEW
THE DAMN PLANE FIRST, and troubleshot second. I’d spent some time thinking
about the test flight, planning what to do for engine failures at various
stages, total electrical failures etc. As usual, the inflight
problem you often encounter is not exactly what had been planned for, but the
decisions made weeks previously worked like clockwork. Overall it had been a most
satisfactory process.
FLY TIME
J
Once the new capacitor
was fitted, JHW was away. The following weekend was a real pleasure – I took my
son Robert as my first passenger, then Roger Dixon (general workshop pariah and
abuse merchant). We did a couple of hours and went home well satisfied. Rog and I had been complete idiots once clear of the
circuit, cheering , yelling and yahooing in the cockpit like the real pillocks we profess to be.
The next weekend was a
real eye opener. We went up to Fielding to play in the plane. By the end of the
day, I’d done 6.2 hours – more flying than on any other day in my entire
experience. I took anyone for a fly, my daughter Annelise, JJ , a trial flight,
John Varley, and a couple of other club members. I
was amazed at the contrast to MYC, our Challenger. In the Avid, a 20 min flight
took us to Woodville and back. John and I headed for Dannevirke,
decided it was too quick, and went on to Waipukurau
and back. These would be quite reasonable cross-countries in MYC, but were a doddle in JHW. What a blast.
Jennifer still smiling as we head back into the
sunset
I also had a chance to
take Peter Dunning and his daughter Jennifer for a fly. Peter and I have become
close friends as committee at club level, and building our machines. It was a
great early evening fly, and for Jennifer, a literal eye-opener. She’d had a
Bantam ride in less than ideal conditions a couple of years previously, and was
a little unsure of another microlight flight. As we
lifted of the wide-eyed “Wow” from the right seat was music to my ears.
We’ve been at it since
then – any excuse for a fly and since that 19 October test flight, JHW has
logged 44 hours, including a 24 hr/ 10 day excursion down the east coast of the
South Island, stopping at Waimate to stay with the inlaws and visiting Croydon
Aircraft at Manderville (excellent – GO THERE - trust me – just do it)
And managed to catch
up with Stuart Tantrum at Omaka and have a look at the WW1 collection there. I
learned a lot about transponders, controlled airspace, the
Peter Hancox – he helped me with the original
purchase of JHW (see episode 1)
Summary
The bottom line is
that the whole process has been very satisfying and I have a plane I’m
passionate about (as if you couldn’t tell ), I’m intimately familiar with all
it structure and systems, and have much to learn in the flying, and ground
handling side of things – all of which I set out to do. Yes it was a good
decision to buy a tired plane and rebuild it, and yes there are still some
compromises I must live with, particularly a limited baggage space (compared to
a RANS). It flies well although I only
get about 5200 rpm at takeoff, instead of the preferred 5800, but in the air,
5500 yeilds 100mph and 5200 about 90. I have much to
learn about wheeler landings and can manage 3 point OK. I can fly for 30 min,
just touching the rudder pedals occasionally, perform really good slips, and
bank angles way beyond the capability of our Challenger. 44 hrs in 3 months is
great and by the time I reach 100 hours I’ll be well on the way to learning the
niceties JHW is capable of. In the meantime, JBR has come up with a cunning
plan involving the
Heading down the Kaikoura
coast, Jan 04