Tinworm-wings: Power, venting and psychology

Friday, 3 September 2010

Power, venting and psychology

On the very last day of a summer holiday spent grounded by winds, I finally got airborne. This day's other great significance was that it was the first take-off since I ploughed into a field of crop when my big end bearing failed on the climb-out in June.

And this time, as I took off I was clearly under-powered and naturally this alarmed me more than it might otherwise have done and, aware that I had to immediately set myself up for an emergency landing, (and not get caught out by continuing into wind as I did last time - running out of runway), I called Mayday and did a tight turn downwind and then, still high, lined up at the start of the runway (and this is the funny thing with the Dragonfly wing) couldn't dump sufficient height to get in on the first run, so had to go around, but again in a very tight circuit. Once down, the engine died at idle. I restarted and Dave Garrison (who had given way to me in the circuit) reminded me to cancel the Mayday, after which, I taxied in to work out what was wrong.

A quick call to Paul Bailey suggested the main reason:- I had flown on a tank full of fuel that had been venting since the 6th July. No wonder it had lost its potency at the top end! Also, he said, having left the fuel in the carb the jets would be (what word did he use?) coated in the residue of the old fuel and this would affect the settings. He said that running new fuel through the carb would clean the jets. Never leave fuel in a carb for more than two weeks.

Lesson learned.

Steve has mentioned this before and I had forgotten. Others say they top up with fresh fuel, but this time I drained mine off completely and filled with new stuff and that did the trick.

I flew another circuit, but again came down very quickly because my throttle was slipping, so that I couldn't fly without keeping one hand on it. Once down, I tightened it.

Dave Broom kindly took G-CFKK up and confirmed that it was now climbing well but said he too had trouble with a slipping throttle. I tightened the throttle as best I could without the right allen key, and then went to test it again but aborted when the runway vibration made the throttle slacken again.

Today I have bought some nuts and super glue for the throttle job and next time, and from now on, will be monitoring engine revs with a Tiny Tach *, a very nice little tachometer which works by induction (by wrapping a lead around the HT lead) to measure the number of sparks per second - and giving an RPM read-out. That should take the guess work out of power settings. Then all I need is a good flight to overcome the psychological block at take-off....the anxiety, which I didn't know was there, that I won't have enough power to get airborne.

*The Tiny Tach cost me £45, which includes VAT and postage. You pay by return, once the item has arrived. I thought that very reasonable. The one done by Bailey was more expensive and anyway has been discontinued by their distributor because the price has been hiked by the manufacturer by 30%!

2 comments:

Colin said...: Maybe the foot throttle is a better option? Surely being able to keep both hands on the bar or be able to transmit on the Radio while having power control would be useful.
The Tacho/Hobbs looks very good. Nice and simple.
Fuel business:- I would have thought just mixing some fresh in the tank should suffice? That should purge through within a few minutes running?
How many small capacity single cylinder Bikes do you here of having to drain & refreshing fuel?; 4 September 2010 at 20:07
Tinworm said...: Was talking about a foot throttle this weekend, Colin...and may make one myself.

I think you are probably right about fuel....as long as I don't leave it standing too long.

The tacho worked well....but may have given me TOO MUCH info....because now I could see what a large variation in revs I got....hard to set up throttle. But now it its stable, I should get a good, positive read-out.; 20 September 2010 at 21:11

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Ground handling (how to store an aeroplane at home and get it to the airfield)

A trial flight in a Thruster, when I was 28, c.1991

I have started to learn to fly before...TWICE! First time round I had just graduated and got a job at an aerodrome in Cornwall, where I earned flying hours by fuelling microlights, giving hourly weather reports to the Met office etc. The weather was bad, so there was little flying to be had...and in the end I was paid with broken propellers and bits of crashed fuselage to hang on the wall. The boss was a great bloke called Ian Stokes, who had been a leading light in forming the BMAA and had manufactured Thrusters in the early days . In retirement he moved to The Gambia and became a publican and, shockingly, was murdered this year.

Flying Rogues

ten years on from my first experiences at Moorland Flying School (and now nearly ten years ago) the flying school was under new management and my girlfriend and I booked full courses. We both made good progress initially but never felt we were being moved on and had difficulty pinning the instructor down to signing our logbooks. When another instructor signed himself as P1, we got suspicious, contacted the CAA and were horrified to learn that our instructor did not have a current instructor rating, that we had not been insured and that none of our hours counted towards our licences. We were eventually refunded and the instructors were prosecuted by the CAA.

The very sympathetic CAA investigator spoke to the BMAA on our behalf and my hours have been allowed to count (at the discretion of the school). But in point of fact, I flew way over the minimum number of hours subsequently, so it is really quite academic in the end.

Around 2001 an instructor in Norfolk tried to convince me that if I bought his aeroplane he could teach me at a cut rate, as I'd then be using my own plane. Great idea, I thought, except that it turned out that the aircraft in question had failed a noise test and could not be used from the instructor's field. He later admitted that I would have to learn on his aeroplane at the normal rate. He resisted showing me the paperwork, kept avoiding me and eventually, when it was quite clear I wasn't going to buy without the paperwork, told me to F-off.

So far my experience has been that there are a lot of rogues in flying, which is one reason why I was so very impressed by the professional set-up at Sywell.

by air to Africa

My sister and I were lucky to fly many thousands of miles in the 1960s and '70s in many aircraft types, including BOAC VC-10s, Boeing 707s and even a Nigerian Airways Dakota, as our dad (and later our mum) had teaching posts in Kenya and Nigeria. Those were still the romantic days of flying, when passengers walked across tarmac and up steps, rather than walking down the tubes that have turned passenger flying into a mundane affair. (Mind you, aren't take-offs still incredibly exciting!?)

Back then air hostesses GAVE children the sorts of nick-nacks that their parents have to pay fortunes for from the airline catalogue these days; things like model aeroplanes, keyrings etc. We were also given sweets to help us cope with depressurisation. (And they were hostesses, so nobody give me a hard time)

Mum says that I cracked my first joke when I was small, on a flight out to Kenya, when I said, "Mummy, shouldn't there be a wing on this side of the plane too". Apparently I got her with that one.

At Kano airport I remember standing behind an engine and thinking how hot it still was....and then being told that the engine was cold. The heat was Kano. I got a headache and took several days to aclimatise.

The airport perri-ways at Kano were littered with aircraft that didn't make it, including a burnt-out Mig 15. The Nigerian Airforce flew them and my dad played squash with one of their pilots, Ben, at the Kano Club. I recall a Mig fly-past on my birthday. Was it arranged with Ben over a beer? Was it a pure coincidence?

At Entebbe airport (Uganda) I remember climbing down the steps on to the runway and being encircled by soldiers with machine guns, who then went through all our belongings and confiscated my cherished Swiss Army penknife, purchased on one of numerous European stop-overs. That was in the twitchy time after the Israeli hijacking ...and mum had to stifle my protests.

Before my first flight to Nairobi, as an infant, I was scared stiff. I didn't understand that I wouldn't have to sit astride the fuselage, as I did on my pedalcar! In a funny way, I not only overcame that fear but have come full circle; microlighting is just like sitting on that pedalcar......open to the elements - real flying!