Wednesday, 31 March 2010

March in review

A full year has passed since I started on this amazing project.

March was a very productive month, more noticeably so because it came after several months in which the weather, for the most part, contrived to frustrate progress. Indeed, I was really quite surprised how quickly it was possible to sign everything off from an engineering inspector's perspective.

By the middle of the month I was able to submit all the paperwork for the permit to test fly and now, at the end of the month it seems that it will only be a matter of days before we are able to slip the surly bonds.

April should be interesting!

Breaking news!

I've just got back from a few days away to find an e-mail waiting for me from the LAA. Apparently the Ballistic Recovery System installation has been signed off, following successful load tests at the Sportcruiser factory.

I have some minor paperwork to attend to but otherwise it seems that a major uncertainty has been removed and it is likely that the permit to test fly is imminent.

Pity about the weather... it's snowing again!

Monday, 29 March 2010

Fireproof plate

With the paperwork working its way through the LAA bureaucracy there isn't a lot I can do to progress the project. After a couple of weeks on other things, including recovering from a major crash on my main computer, I spent part of yesterday up at Kirkbride airfield tidying up a few loose ends.

One minor item outstanding was the requirement to have a fireproof identification plate attached to the aircraft fuselage. This requirement probably goes back to the days when aircraft were made of wood and were likely to be more or less completely consumed in the event of fire. These days it does seem a little pointless, but rules is rules, so a fireproof plate we shall have.

It turns out to be a bit of a palaver. In order to be truly fireproof, the plate must be made of stainless steel, which is not the sort of thing that engravers typically keep stock of. I fixed this problem by buying a sheet of the stuff on eBay and having it cut up into lots of small plates, 40mm x 60mm. I had rather a lot more plates than I need(!) so I offered the surplus to other Sportcruiser builders via our Yahoo! Group. The considerable take-up on my free offer suggests that sourcing the materials was a problem for others too.

The next problem was getting it engraved. We have three shops in Penrith that offer engraving services. Two were adamant that they could not engrave stainless steel because it is too hard and their machines weren't up to the job. The third shop said "no problem", even though it appears to have the same engraving machine. Go figure, as they say.

Anyway, shop number three did a nice job and the fireproof plate is now suitably attached to G-JONL's fuselage.

Thursday, 25 March 2010

One year ago today...

Exactly one year ago today Sportcruiser quick-build kit serial number 700320 arrived in Cumbria. Later it became known as LAA project number 338-14889 and some time after that G-JONL.

Along the way several thousand rivets have been set, a few hundred metres of wiring have been installed, an engine has been transformed from a mysterious thing in a box to a working propulsion unit at the front of a nicely painted airframe. The kit of parts has become an aeroplane.

It's sometimes hard to think back to those early days and the enormity of the project I took on, ably assisted by a few friends. A great deal has been learned along the way and there is a lot more to discover as we head towards flight testing and permit issue.

I hope and very much believe that the second year of this project will be every bit as exciting as what has gone before.

Wednesday, 24 March 2010

Permit application update

I was pleased to receive an e-mail from the LAA this morning, just one week after I submitted the paperwork to them. They are working on the application and had a few, easily answered, questions.

It also looks like the BRS issue is close to resolution and therefore should not delay the permit to fly much, if at all. The factory has done the required load tests and the installation passed with flying colours.

Progress is being made!

Wednesday, 17 March 2010

Documents submitted to LAA

The application for Issue of a Permit to Fly went off to the Light Aviation Association this afternoon, complete with a big stack of supporting forms and other documentation.

I now feel strangely idle, unable to really do much while the wheels of bureaucracy turn. The biggest potential issue is the Ballistic Recovery System, which is still not fully approved, even though it is a standard factory option. Hopefully that'll be resolved soon and it won't unduly delay my application.

There's still a few things I can be getting on with whilst I am waiting and as it happens I'll be fairly busy with other hobbies and activities over the next couple of weeks, so the wait shouldn't be too frustrating...

Sunday, 14 March 2010

Inspector says YES

Tom, my LAA inspector, signed off all the remaining paperwork for G-JONL this morning. "As far as I'm concerned, you can go flying today" said he.

Well... not quite. I now have to negotiate the bureaucracy that stands between my signed off aircraft and its first test flight. Apparently this takes around a couple of weeks... we shall see. And there's the small matter of insurance. I not only need to upgrade the ground risks cover to all risks, I also have to demonstrate to the Civil Aviation Authority that I have done so.

Nevertheless, it is a big step forward. The build is completed, more or less one year after I started. Not bad. Not bad at all! I feel a celebratory pint coming on.

Saturday, 13 March 2010

Paperwork, paperwork!

I've spend much of today sorting out the paperwork for submission to the LAA. Tomorrow I am meeting my ever helpful LAA inspector to get the last few items signed off and with a bit of luck I should be able to get all the documents off to the LAA some time next week.

The list of documents is really quite daunting but, in fairness, each document is important and necessary. It just takes a long time to collect all the information together and make neat copies of everything. Here's the list so far
  • Application for Permit to Fly
  • Inspection Schedule and Record book
  • Engine installation checklist
  • Fuel flow check sheet
  • Airfield information
  • Pilot information
  • Weight and Balance report
  • Aircraft radio installation approval form
  • Certificate of Registration
  • Aircraft radio licence
  • And last but not least, a cheque for the hefty initial permit to test fly fee (£540)
I think it's pretty well all there now, so I've put my inspector on mass signature alert for tomorrow morning!

Weight & balance

The final major build task was completed yesterday, 12th March - weighing the completed aircraft. Necessarily this is the last job, as the aeroplane has to be in its final, ready to fly configuration.

There are two distinct aspects to the weighing - weight and balance.

Weight is the easy one. It is the overall weight of the aircraft, usually expressed as the empty weight, that is without fuel, baggage, crew, etc. The empty weight does include engine oil, coolants, etc. All aircraft have a maximum take of weight (MTOW) and the difference between MTOW and the empty weight is the available load.

Balance is a little more complicated. There are limits on how the weight can be distributed around the airframe. For example, if heavy baggage were to be loaded well aft this might give such a large nose-up attitude that there is insufficient elevator authority to control the aircraft in the descent. Take off would be no problem but the landing would really spoil your day! There are fore, aft, port and starboard limits for all aircraft and these collectively define the permissible weight and balance envelope, within which flight is safe and legal.

This is clearly a job for a specialist, so I enlisted the assistance of PlaneWeighs Ltd. These people weigh everything that flies, from microlights to 747s so they probably know what they are doing.

Chris and I arrived at Kirkbride just after 9am to find Steve Fail already on site and unloading his van. We quickly set up three weighing pads, one for each wheel. These pads use a hydraulic system and are good for 13,600kg, rather more than this particular task will require! The pads take a few minutes to stabilise, so we pulled G-JONL on to the pads and left  them for a few minutes whilst Steve set up his computer.

The actual weighing process is, of course, very quick. Bottom line was 385kg, which is about what I was expecting, given that G-JONL is well loaded with avionics and has the ballistic recovery system fitted.I'd reasoned that anything under 400kg would be just fine.

Slightly more complex is determining the balance. This requires a datum, which is defined as the leading edge at the fourth rib out from the wing root. Using a couple of laser markers, Steve was able to accurately measure the precise location, aft for the main landing gear and forward for the nose wheel. These distances are the arm at which the weight is located and from the combination of arm and weight, one can compute the balance - in effect, the centre of gravity.

With all these figures it was now possible to construct the empty weight and balance report. In addition, a couple of reasonable real life examples have to be prepared, allowing the weight and balance envelope to be explored. We chose pilot, no passenger or baggage for one case and pilot plus passenger and baggage in the aft baggage area as the other case. Both yielded C of G measurements well within the limits defined for the aircraft.

We then retired for a much needed cup of coffee and some warmth in the LAA Strut caravan, where Steve and I completed the LAA weight and balance report. Steve also produced a nicely bound full report with rather more details of the methodology, etc.

Some people try to cut costs by doing the weight and balance report themselves, using domestic scales or whatever comes to hand. For the cost of getting it done professionally, I am more than happy with the end result and consider it to represent good value for money.

Thursday, 11 March 2010

Getting ready for the weigh-in

With the aircraft weighing booked for Friday 12th March, I spent a few hours at the airfield today, getting everything ready.

The object of the exercise was to to get the aircraft into its completed, empty configuration. Firstly I fitted the wheel spats, something that I had not done since the aircraft was painted. They certainly make it look very pretty, although I am quite nervous of such close-fitting spats for flying into grass strips. They look like they will probably fill up with mud and grass clippings rather quickly! So whilst it is right to do the weigh-in with them fitted, I'll probably not keep them on for long.

I also finally fitted the wing root fairings. I'd been a bit nervous of riveting these on, in case I had any reason to get at the wing root again. I think that time has now passed. I hope the wings won't need to come off for a long time.

Next, I had to empty the fuel from the port wing tank. I'd loaded 20 litres for engine tests and despite quite a few engine runs and some taxying trials, it would good to see that about 15 litres came out. Either someone has been kindly filling the tank for me or the Rotax engine is satisfactorily abstemious!

The cockpit was next. I've tended to use the rear baggage area as a place to store odds and ends so these were all removed for the duration. Whilst inside the cockpit I also took the opportunity to fit the compass card.

Finally, I had to remove the fuel pressure testing system in the engine bay and I concluded with a walk around to make sure that everything that should be there is there and nothing else.

Ready for weighing, Sir!

Wednesday, 10 March 2010

Aligning the control surfaces

It is essential that the flight control surfaces are properly aligned and symmetrical. The deflection ranges are also tightly controlled. Accordingly, there is a certain amount of adjustment available for each of the control surfaces and trimmers. The control surfaces are:
  • Ailerons
  • Elevator
  • Rudder
  • Flaps
  • Aileron trim
  • Elevator trim
Acceptable deflection values and tolerances for most of these control surfaces are documented in the LAA type acceptance data sheet (TADS) and the task before us yesterday was to first measure and then, if necessary, adjust each surface to be within spec.

This activity is greatly assisted by a clever new gadget that has come on the market in recent years - a digital angle gauge. This is able to measure any angle from any baseline, to an accuracy of ±0.1°, which is a considerable improvement on the old fashioned protractors that we used to employ. To make a measurement, it is merely necessary to place the gauge on the surface in question, adjust the surface to its neutral position and then zero the gauge. Deflection angles can then be read directly off the gauge. The picture shows the digital protractor in use on one of the ailerons, before adjustment, showing a 15.6° downward angle from neutral.

The flaps were easily adjusted and checked. The flap control mechanism features an eccentric pin, which engages with the flap and can be rotated to fine adjust the flap position. Each flap was adjusted in turn for the same deflection from horizontal whilst in the up position. This position became the neutral reference point for checking flap deployment at 15° and at 30°. Clearly it is a good idea that the flaps deploy symmetrically and the checks proved that indeed they do. You can see the final results in the table below.

First the ailerons had to be adjusted so that they are both in the neutral position with the stick centralised. This is easy enough to do by making small adjustments to the control rod end nearest the aileron. Both ailerons were very close and it was therefore only necessary to unscrew the rod ends a couple of turns to achieve perfect symmetry. Next, we checked the up and down deflections. Both are controlled by end stops in the cockpit and both were initially set a little to high. Again, minor adjustments brought the deflections into spec as shown below.

With the ailerons correctly aligned, it was now possible to check the deflections on the aileron trim tab. The permissible range for this tab is not specified, so the measurements were taken merely for the record.

The rudder poses a pit of a problem, as it is a vertical surface that remains more or less vertical throughout its operating range, making it impossible to use the digital angle gauge. The approach we took was to place some masking tape on the horizontal stabiliser and mark the centre position and the two full deflection positions on the tape. The distances from the root of the rudder to the centre mark and from the centre mark to each extremity of movement were then measured. This gives a right angled triangle of measurements from which the angle of deflection can be calculated. My O-level mathematics came to the fore, reminding me that the angle is given by Θ=arctan(opposite/adjacent). I decided to spurn my old book of mathematical tables and instead used Google's excellent calculator function to compute the angles. The results were well within specification!

Very satisfactorily, the elevator deflections were spot on when measured, so no adjustment was required. However, the elevator trim tab was a little way out, so it was necessary to adjust the reach of the actuator arm slightly.

The final results are shown in the table. All deflections are well within specification, so it now just remains for my inspector to sign off the associated paperwork and that'll be another major task completed.

Swinging the compass

Another job completed! Yesterday, Chris and I performed the compass swing on G-JONL. The aircraft has a compensated magnetic compass mounted on top of the instrument coaming, which is used to set the Direction Indicator before and, where necessary, during flight. In effect, the magnetic compass is a reference instrument and therefore needs to be calibrated as accurately as possible.

Unfortunately, aircraft have lots of magnetic materials, including parts of the engine and , of course, electrical circuits that can generate magnetic fields. So, rather like a ship's compass, it is necessary to compensate for these fields and to calibrate the compass at all points on the compass rose.

Using a prismatic compass, We carefully aligned the aircraft on magnetic North. This was greatly assisted by lining up the two comm antennas and the tail plane to determine the precise centreline of the aircraft. A quick check of the aircraft compass and, yay! it shows exactly North. The engine was run and all instruments, etc. switched on. No change. This is going the be easy!

Next up was East. Here the compass was quite some way out, reading around 70°. There are compensation magnets to correct these errors, one for N/S and another for E/W. A quick tweak of the E/W screw and 90° was easily obtained. From there to South and about a 3° error. The trick here is to halve that error and apply 1.5° correction using the N/S adjustment. Finally round to West, which showed a negligible error of 1° - not worth attempting to correct.

With the four cardinal points sorted, it was time to swing around the compass rose at 30° intervals. All readings were within three degrees, which is perfectly acceptable. Being somewhat unimpressed with the scruffy piece of paper provided for recording the results, I made up a new compass record card using Visio and that is ready to be attached to the compass when I am next at the airfield.

Another significant milestone on the way to the permit to test fly!

Friday, 5 March 2010

A flight to Cark

All work and no play makes John a dull boy, so it was particularly pleasant to be able to fly with my Chief Test pilot designate, David, down to Cark, which is a small airfield on the southern edge of the Lake District.

It was a lovely day, with excellent visibility. There is still an awful lot of snow on the Lake District fells! I'd never been into Cark before, so it was nice to get another new airfield in the log as well as getting a bit more experience of flying in a Sportcruiser.

Monday, 1 March 2010

Test pilot

As the prospect of flying G-JONL gets ever closer, it is time to get my chief test pilot organised.

Although I was a little put out that another Sportcruiser turned up at Kirkbride, all finished and flying, before I even had the wings on my bird, the fact is that it's ended up by being very convenient for, as a result, I have easy access to local pilots with actual flying experience in a Sportcruiser.

David is that man. He has 1300 hours or so of flying experience, which is a lot more than I can muster and he has 20 hours on the Sportcruiser so far, and incrementing.

To register David as a test pilot we had to fill in yet another a form, naturally, this one detailing his experience and willingness to undertake the test programme. The form has now been sent off to the LAA and we await their deliberations.

The initial flight has to be done solo, so David will be on danger money for that! After the first outing, we can travel together, with one of us flying and the other taking notes. There's 17 pages of flight tests to be done that explore the entire flight envelope. I'm delighted to have David to help me.

The inspector visits

Tom, my friendly and ever helpful LAA inspector came to give JONL a thorough inspection yesterday. He was particularly interested in the flying surfaces and flight control systems so we spent a good hour poking around in dark recesses with a torch and waggling control surfaces back and forth.

There were a couple of observations that I will attend to, even though Tom was content with them as they were. We had a good furtle around in the engine and propeller department and a bit of a peek at the avionics and instrumentation, though, as Tom succinctly put it, "you probably know rather more about that sort of thing than I do"!

We also spent a while checking out the undercarriage and Tom carefully inspected the wing main spar connections and bolt torquing at the wing roots. All in all it was a pretty exhaustive inspection, which I am very glad of.

With the inspection complete, we repaired to the club house for some much needed warmth and refreshments. Tom then went through my build  stage log and signed off everything apart from the weight and balance (yet to be done, scheduled for 12-March) and the final inspection. We also filled in lots of information in the airframe and engine technical logbooks, making sure that all the mandatory mods are properly referenced and addressed.

So I'm almost there! I'm starting to collect all the various bits of paperwork together for submission to the LAA and with a bit of luck I should be able to get everything to them before the end of March.

Fuel flow (electric pump)

After a week of little progress due to some consultancy work and a rather nasty cold, I'm back on the project!

One of the remaining tasks was to measure fuel flows. The engine requires 27 litres per hour at full chat and the fuel system must be able to provide 125% of the maximum consumption, i.e. 33.75 litres per hour. The minimum permitted fuel pressure is 0.15 bar and it must be possible to deliver the required throughput  whilst maintaining the minimum pressure.

All of this means that a test rig has to be constructed that allows fuel to be metered and measured. The LAA provides guidance on how this should be achieved as shown in the diagram to the right. I needed to procure a couple of small fuel taps and some hose. Fortunately, I already had a suitable pressure gauge, previously rendered redundant by the decision to go for an electronic engine management system. The picture below shows my practical implementation.

The Sportcruiser has both electric and mechanical (engine driven) fuel pumps. Both must be able to separately deliver the required throughput. One of the known problems with the electric pump is the ability to deliver the necessary pressure and fuel flow simultaneously. In part this is because of the unique (to the UK) requirement for a vapour return line, which continuously siphons 3-4 litres per hour back to the port fuel tank. Recently the LAA has agreed that the pump cam be upgraded to a more powerful version.

Sure enough, I couldn't get anywhere near the required fuel flow with the standard pump. The pump would just about provide 0.2 bar of static pressure , i.e. with no fuel flow, but as soon as any significant fuel flow was permitted, the pressure dropped way below the 0.15 bar minimum. At 0.1 bar, I obtained a paltry 380ml of fuel in one minute, the equivalent of 22.8 litres per hour - well below the required throughput. Fail!

In anticipation of this problem, I had obtained the higher pressure pump and this was duly installed and the tests re-run.

What a difference! Firstly, the static pressure is now around 0.3 bar, which is nicely in the middle of the permitted range. I set the fuel pressure adjustment tap to 0.15 bar and recorded 320ml in 30 seconds, the equivalent of 38.4 litres per hour - comfortably above the 33.75 required.

I still need to do the mechanical fuel pump throughput tests. Rather alarmingly, this involves running the engine at full chat and measuring the residual fuel flow, which must be at least 25% of the maximum engine consumption. This is clearly a test to be done on a nice day (which we have notably not been getting recently) and with the assistance of a friend or two. Frankly the idea of making fuel flow measurements with the propeller whizzing around at full speed less than one metre from where I have to stand terrifies me and offends against my every safety instinct. It'll have to be done but I am not looking forward to it!