Sunday, 28 February 2010

February in review

Quite a lot happened in February, despite the continuing freezing weather. I seem to have been working in a cold hangar for ever! The thing that keeps me going is the prospect of getting G-JONL flying soon, with a whole summer ahead to do it in.

With the wings on, the kit of bits at last looks like an aeroplane. I fitted the control sticks, which are best kept out of the cockpit during construction, as they really do get in the way. That enabled me to check out the operation of all the flying surfaces and, of course, finally check that the trims and radios work properly as a complete system.

With a feeling of real anticipation, the engine was filled with oil and coolant. No leaks! It is a bit of a palaver to purge the engine - a process of getting oil into all the nooks and crannies of the engine before actually starting it - but eventually I succeeded, following Rotax's excellent instructional video on the subject.

The final bit of preparation was to pitch the propeller - a task made easy by the use of a digital angle gauge.

Running the engine for the first time was very much a seminal moment - proof that the project is nearing completion. It was good to be able to share the experience with some of my friends that have helped me along the way. being able to do a couple of taxy runs was just icing on the cake but with an important purpose - building confidence in the aircraft's aerodynamics.

Finally, on the last day of the month, the inspector visited and gave the aircraft a really good going over before signing off almost all the remaining stages. I've not written about that yet but I will do, soon.

So February was very much the beginning of the end of the build project. March should see completion and, maybe, even a bit of flying!

Sunday, 21 February 2010

Running the engine

Friday 19 February 2010, Kirkbride Airfield, Cumbria

Probably the most significant day in the life of G-JONL since the project began in March 2009. Today we started the engine and the aircraft moved under its own power for the first time.

My friends Chris and Jim and I arrived at the airfield early on Friday morning. First we had to move many gyrocopters and the resident biplane, a Steen Skybolt, whose place in the corner of the hangar I had acquired for final build. I then pulled JONL out, blinking, into the brilliant sunlight and could see the finished product properly for the first time.

A few final checks on oil and coolant level and it was time to attempt the initial engine start.

Initially nothing doing. No signs of life at all. Unable to find anything wrong I had another try.

Suddenly the engine burst into life. I can only assume that it took a little while for sufficient fuel to get to the carburettors although I would have expected the electric fuel pump to have done that, so there is a bit of investigation to do there.

Immediately I realised that neither tachometer (in the D120 Engine Management System (EMS) and the backup analogue instrument) were working. Not an immediate problem but definitely needing to be investigated.

I ran the engine for a few minutes, letting it warm up, whilst carefully watching the engine instruments for any abnormal behaviour - none noted. I also checked the magneto cuts on both Mag-A and Mag-B worked OK, each causing a small drop in RPM. The Alternator was charging OK and all the alarms were extinguished.

After shutting the engine down, I started investigating the tachometer problem and discovered a rather silly wiring error, which was duly corrected. Still no joy. Further investigation turned up a broken lead to one of the connectors behind the instrument panel and when that was corrected, the EMS tachometer burst into life. The analogue tachometer problem proved to be rather more intractable, so I decided to defer further diagnostic work until the aircraft was back in the hangar.

It was time to try a bit of slow speed manoeuvring. Because the nose wheel is merely a castor, low speed steering is achieved via differential braking, so it was important to be confident that the braking system was working well before having to use it in earnest.

Everything seemed to be working perfectly so I decided to venture out onto the runway and do a slow taxy run. The runway is about 1km in length, so it was possible to get a good feel for how the aircraft handles on the ground.

A completely successful run! The rudder starts working almost as soon as the aircraft is moving, so there is almost no need to use the brakes to offset the natural tendency for the aircraft to yaw left, due to the gyroscopic effects of the engine. Time to try a faster run.

I got up sufficient speed on this run to just get the nose wheel off the ground, so the effects of the elevator, rudder and, to some extend, ailerons could be evaluated. Everything seems to be perfect.

We achieved everything I had hoped to for the first engine run and more besides. We returned G-JONL to the hangar and parked her in her new position - a promotion, no less, for she is now closer to the hangar doors!

My thanks to Chris and Jim for their assistance during this important day. Photograph and video credits to Jim. Lunch credits to Chris!

Friday, 19 February 2010

The engine runs!

And the aeroplane has moved, rather well it must be said, under its own steam.

More later. I'm off to the pub to celebrate with the team.

Thursday, 18 February 2010

Pitching the propeller

The propeller on G-JONL is a three-blade, fixed pitch ground adjustable type. Each blade has to be separately adjusted to the same pitch as its siblings. The question is, what pitch angle to use?

A fine pitch would be great for short take off runs, whilst a coarse pitch gives better cruise speeds. It is because of the conflicting requirements at these two extremes of the flight envelope that more complex aircraft have variable pitch propellers.

Whilst I have not ruled out fitting a variable pitch propeller one day, for the time being I've decided to stick with the fixed pitch for simplicity and lower cost of ownership. Fewer things to go wrong too! So today I spent a happy hour or two setting the pitch on each of the three blades of my propeller.

Received wisdom is that a 17° pitch relative to the plane of the propeller and measured close to the tip is a good starting point. This should give a good cruise speed without compromising take-off performance too much. To measure this requires that each blade in turn is placed horizontal and then the angular measurement and adjustment made at a known point on the blade. I am using a Wixey digital angle gauge, which makes the task a lot easier.

Using a post, held vertical in my Workmate bench, it was easy to find the centre of the propeller and extend that out to the tip so that the blades could be aligned to the horizontal. It was then just a case of applying the protractor first to the hub of the propeller to obtain the reference plane and then to the tip of each blade in turn.

The whole job took about an hour to complete and the first test will be tomorrow when we start the engine. Any significant out-of-trim will give rise to vibration. Hopefully we'll have none of that!

A treatise on Mogas

Mogas, otherwise known as unleaded petrol is what my engine prefers over Avgas. I prefer it too, as Avgas has a little lead in it, which tends to gum up the valves over time. Avgas is also a lot more expensive that Mogas and using it halves the maintenance interval for the engine.

If you drive a petrol engined car then petrol is petrol is petrol. Essentially it's all much of a muchness and most motorists will go to whatever garage offers the lowest price today. Wouldst that it was so for petrol burning aero engines!

Firstly, the Rotax engine likes a reasonably high octane fuel. Fortunately, 97 octane fuel isn't too hard to find and is ideal. A bigger problem is that a lot of petrol these days has 5% or even more of ethanol, which is a form of alcohol. Our CAA forbids the use of mogas that contains ethanol because, amongst other things, it is claimed that the ethanol can damage certain components, especially aluminium fuel tanks and rubber piping. Whether this is a real threat at such low levels of ethanol is a moot point - the problem is that if the CAA forbids it then one is flying illegally if it's in the tank and in the event of an incident, even one unrelated to the fuel being used, insurance is likely to be invalidated.

Fortunately, it is still possible to get petrol that has no ethanol, though it is unclear for how much longer. It is also fairly easy to test for ethanol in fuel. It turns out that Total's Excellium 97 is ethanol free, at least for the time being, so that is what I intend to use.

Getting ready to start the engine

In preparation for starting the engine for the first time, hopefully tomorrow, I spent a bit of time today making sure all was ready.

Firstly, I purged the engine oil system. This involves pressurising the system using an air compressor, then rotating the engine by hand until good oil pressure is shown on the engine instruments. The system is pressurised by applying air pressure to the oil tank breather. I discovered that a standard quick release air hose connector is exactly the right size to make a good connection to this hose. It is also necessary to block off the oil pipe from the engine sump to the oil tank. This I achieved with a short length of garden hose, sealed at one end. A bit of gentle warming of the open end, using a heat gun and the hose slipped onto the oil tank easily. It took about 20-30 turns of the propeller to get oil pressure showing on the instruments in the cockpit.

I also put about 20 litres of fuel in the port tank (the one with the vapour return line) and checked that the electric fuel pump gave fuel pressure and fuel flow. Due to the vapour return line, there is always a small fuel flow, even with the engine not running. I measured the vapour return flow at around 2.5 litres per hour, which is about what I was expecting.

So now we have coolant, oil and fuel all in the engine at the same time. The only other thing needed is a spark. The plan is to apply that to the mix tomorrow, when we attempt to start the engine for the first time.

Saturday, 13 February 2010

Is it really a year?

My pal Chris phoned me today and said "it must be about a year since you first went to see the Sportcruiser". In fact it turns out to be just a little more than a year - I made the trip down to Cornwall to view the kit for the first time on 3rd February 2009, having seen an advertisement in Flyer Magazine.

So the project is slightly more than a year old. That said, I didn't actually get my mitts on the kit until 25 March, so perhaps that should be the first anniversary? It's certainly been an interesting year! I'm at the stage now where it feels like the build project is part of my life (sad, eh?). In fact I have thoroughly enjoyed the whole thing, even if occasionally it has been frustrating.

As we move into the final phases of the build programme, I do occasionally find myself wondering what I will do with all the spare time when I am no longer building an aeroplane. Ah! I know - I shall be flying her!

Friday, 12 February 2010

Engine fluids

The concentrated coolant for the engine arrived a couple of days ago, so I decided the time had come to start filling the engine with fluids. Firstly I mixed the concentrate antifreeze with Halfords' best deionised water to obtain the 50:50 ratio required for the Rotax engine.

The engine only needs a little over two litres of coolant. There is an overflow bottle that is supposed to be half full when the engine is cold, so I also part filled that. I'm assuming that air in the pipe between the header tank and the overflow bottle will be blown out with fluid once the engine is run.

I also filled the engine with oil. About 3.5 litres of AeroShell Sport Plus 4 oil is required but for now I've only added 3 litres. The remainder will go in when I purge the engine, to get the oil flowing into all the oil channels, the cooler and so on. Once that's done it will be easier to avoid overfilling.

Various reports have indicated that it's not unusual to find odd bits of swarf in the fuel tanks and for these sometimes to get jammed in the drain plug at the lowest point in the tank, causing it to drip. The top tip, therefore was to put a few litres of petrol in each tank, swish it about a bit, then remove the drain plug completely to quickly drain the fuel back out again.

I did this yesterday on both tanks. Both the drain plugs were completely clean when removed and despite vigorously swilling the fuel around the tanks, no noticeable solids came out when the tanks were drained. A little Loctite on the threads and the drain plugs were reinstalled, ready for filling the tanks with fuel for the engine tests, which should finally happen next week.

I also completed the installation of the exhaust gas temperature probes in the cylinder 3 & 4 exhausts. This involves drilling a small (0.125") hole in each exhaust, close to the cylinder head, inserting the probe, sealing it with some high temperature silicone sealant and holding the whole ensemble together with a large jubilee clip. Not for the first time, I approached this small job with a certain amount of trepidation!

Wednesday, 10 February 2010

Odds and ends

With the wings on, it was time to make up a list of all the jobs still to be done. Many tasks are simple, 2 minute jobs, such as wire locking the oil tank drain plug. Others are more time consuming, for example, alignment of the flying surfaces. Anyway, I've got a little list.

I've spent the last few trips to the airfield knocking some of these little jobs on the head. One such was the mounting of the air filter. The method proposed by the manufacturer fell well short of what my engineering pride would tolerate, so I spent some time on the PC designing a suitable plate to give a good solid mount. This holds the filter in place in the lower engine cowling but it can easily be removed by removing four screws.

The fibreglass cowling is not particularly thick in this general area and I was worried that it might not hold the rivnuts very well but it seems to be OK, for now at least. If the rivnuts work loose with vibration then it will be comparatively easy to reinforce the holes - a bridge to be crossed should I get to it.

I also wanted to improve on the throttle/choke control housing. This is just a piece of shaped aluminium with a large slot for the levers to protrude through. Small objects could easily fall through the hole. It also looked untidy and there are reports that a cold draught blows through the hole too. All in all, a better solution was needed!

I decided that a brush draught excluder - the sort used on doors might do the trick of filling in the slot yet allowing free movement of the control levers. A trip to B&Q yielded the necessary hardware and it was a fairly simple matter to glue a couple of pieces of brush strip in place, either side of the slot. The end result looks much nicer with the large gaping hole largely hidden from view by the brushes.

Other jobs have included securing the throttle and choke control cables within the engine bay, wire locking the ends and generally checking that everything will stay in place when the engine is first run. I also installed some heat shield material between around the water hoses to the radiator, where they pass perilously close to exhaust pipes.

This week I should get coolant and oil supplies delivered, so I'll be able to get the engine ready to be fired up. That's the next big job!

Thursday, 4 February 2010

Fitting the control sticks

Today was the first chance I'd had to get to the airport since fitting the wings last Sunday. In the meantime, I've made a rather lengthy list of jobs remaining to be done to complete the build and today I made a start of clearing a few items off said list.

The most important task was to fit the control sticks. I'd deliberately left this as long as possible because they really are in the way when doing pretty well any other work in the cockpit. With virtually everything done, there is now no reason not to fit them. In addition, there are various other tasks that are dependent on them being fitted.

It's not a big job but it is a bit of a fiddle. The sticks have to be manoeuvred into their mounting slots and there is a definite knack, which I clearly haven't fully mastered, to getting them to twist into place. I got them both in eventually but I'm not sure I could really tell you how I did it!

With the sticks installed, the cockpit area really does look the part. I couldn't resist sitting in the P1 seat and waggling the stick around whilst making dakka dakka dakka noises. Fortunately there was no-one else in the hangar. I think.

I also torqued the main spar bolts and aligned the flaps using a digital protractor. Finally, I installed the port wing locker Camlock fasteners.

All of which was totally eclipsed when David offered me a brief flight in the other resident Sportcruiser, G-SCZR. It was actually the first time I had ever flown in a Sportcruiser, even though I've been building one for nearly a year! Shortly after take off, at about 300ft, with me in the P2 seat, David said those immortal words "you have control" and indeed I had. It took a few moments to get used to a) the very light stick action, b) using a stick at all - all the other aircraft I fly have a control wheel c) flying a completely new aircraft type and d) doing so from the right hand seat - I don't often fly P2.

Well it didn't take long to get a reasonable level of proficiency and I obviously didn't scare David anywhere near enough because after 15 minutes or so of flying he left it to me to pole my way back to Kirkbride and land the beast. Not a bad landing either, even if I say so myself.

So I now have an enormous 20 minutes of Sportcruiser P1 time in my log book! I think I am going to enjoy flying G-JONL.

Monday, 1 February 2010

January in review

The last fortnight of December and the first half of January were lost due to vast accumulations of snow and ice which had me more or less snowed in for over three weeks. Fortunately around the 13th a bit of a thaw set in and I was able to get to the airfield again for the first time in almost a month.

Getting the tail plane on was a major step forward. Even though it was hardly a big job, suddenly JONL started looking a bit more like an aeroplane. Enthusiasm to get on with the job despite having to work in the cold hangar was reignited.

The next major success was getting the instrument panels finally installed, fully connected up and working. The panel has probably been the biggest sub-project with hundreds of hours of designing, building, documenting, testing and debugging. It was great to have the whole thing finally installed and working.

And then, on the last day of January the wings were installed. Of all the work over the past ten months, this was certainly the most rewarding, for I now have a project that has, in the space of a few hours, turned into an aeroplane. Putting the wings on signals the beginning of the end of the construction phase. Before long it will be time to start on flight trials. It is exciting!

More about the wings

After all the excitement of getting the wings mounted yesterday I was exhausted and definitely not in the right mood for a lot of writing. I went to bed early instead! So let's now add a bit of detail to yesterday's story.

Prior to the event I recruited five helpers, most of whom have helped me with the build before. We also had an Air Cadet from the local squadron where I am a civilian instructor and a Sportcruiser pilot based at Kirkbride. We were on site by 10:30 and after a bit of a briefing we set to work on the starboard wing. I had already made all the electrical and fuel connections so it should just be a case of sliding the wing into place, eh?

Well not quite. At first we couldn't see a way to get the rear spar correctly aligned. The book says that the wing spar goes forward of the fuselage connection but it seemed quite adamant that it wanted to go the other way round! So we tried that.

Well the book was right. Although it seems improbable as the wing is being offered up to the fuselage, it soon becomes obvious that the wing simply will not slide fully home with the rear spar connections the wrong way round. With about 2cm to go it was apparent that the fuselage rear spar mounting was under forward stress and that any attempts to force the wing further into the fuselage would result in some expensive damage!

Back to the drawing board.

I reasoned that the forward rake of the fuselage mount was to ensure that it butts up tight against the wing main spar and therefore it was perhaps raked a little too far forward. It turns out that this mounting is fairly springy in the forward/aft plane, so rather than attempt to ease the rake aft, we tried setting the wing rear spar against the fuselage mounting first, then pushing against it and swinging the wing round to engage the main spar.

With a bit of gentle persuasion, pushing on the leading surface of the wing route, the main spar slid smoothly into place. Once in place, it was very obvious that this was now the correct way round for the rear spar. The wing easily slid fully home and the rear spar mountings lined up perfectly.

Now to try and get the wing mounting pins in place. There is nothing to position the wing vertically other than when the spar bolts are inserted, so it is necessary to adjust the wing vertically until the holes line up. It turned out to be relatively easy to do this and the first mounting pin slid home into the upper middle bolt hole without too much ado. Getting the lower bolt holes to line up for the second pin was a bit more of a challenge and involved some gentle rocking of the wing tip. I found it useful to squint into the hole using a torch to see what the alignment error was and thereby give instructions to resolve the problem. The second pin slid home.

In principle, all the holes should now be lined up but the tolerances are so tight that it was still a bit of a struggle to get the bolts into place. More wing waggling was required, together with some gentle persuasion with a small hammer to get bolts into the four vacant holes. The two wing hanging pins were then removed and the last two bolts slid into place.

With the main spar bolts installed, the wing was, of course, self supporting but I still needed to get the rear spar bolt in place. I was a little surprised to find that the back of the wing was significantly (perhaps 6mm or so) lower than it needed to be. Eek! It turns out that the wing had drooped under its own weight and it was a relatively easy matter to lift it until the rear spar holes lined up and then insert the bolt.

Wing one installed! We checked the wing electrics (lighting and aileron trim) and all was well. Fuel supply and sender checks will have to wait until I am ready to put some petrol in the tank.

At this stage, my younger helpers were beguiled into accepting a short flight with Dave in his Icarus C42. It was a beautiful day, so I can't say I blame them!

Not a problem, for I had an hour's work to get all the connections sorted out for the port wing. This wing has the pitot and static pressure pipes, together with a vapour return to the fuel tank, so it's a bit more busy than the starboard wing. I set to work.

With the team back from aviating, we set to work mounting the port wing. With the experience of earlier in the day it was relatively painless and the wing was in place in short order. With both wings mounted, the call for lunch was unanimous so we headed off to the local pub for an enjoyable pint and Sunday roast.

Back at the airfield, we connected up the aileron control push rods and, joy of joys the ailerons worked... and in the correct sense. I will have to sort out the alignment, as there is a slight imbalance between the two ailerons but that is a job for another day.

We also fitted the wing fairings, temporarily held in place with cleckos. Finally, we fitted the flaps and checked out the operation using the electric flap controls. Again there is alignment work to do but in principle everything works just fine.

With time marching on and everything I had hoped for achieved, it was time to stop work for the day and head home, tired but happy that another major part of the project is completed. Once again my thanks to my helpers for turning out on a chilly January day to make it possible.