Monday, 31 December 2012

The prop is installed!

Having decided that with the vile weather I wasn't going to get any more flying done in 2012, I instead had a very successful day at the airport today messing around with the new prop.

It was a strange feeling removing the existing fixed pitch propeller from JONL. After all, it has propelled JONL and its self loading freight for over 200 hours of fun flying. It's an interesting question what to do with it - I think I will keep it, in case it ever becomes necessary to revert.

Anyway, it was simple enough to remove the old prop and I took the opportunity to give the flange and surrounding metalwork a good clean. I paid particular attention to the hollow power shaft, as this has to provide a good hydraulic fluid seal at each end for the prop pitch control system.

The next task was to install the rotating hydraulic joint, carefully oiling the rubber seals and pushing the joint fully home. This seal is extremely important as any leak will reduce the efficiency of the prop pitch controller and, annoyingly, cover the engine in hydraulic oil! The rotating joint was completed at the propeller end by a cap with holes for the hydraulic fluid and a nylock nut.

Fitting the propeller came next. Firstly the spinner flange was attached to the propeller. It was then necessary to install six bushes in the power flange. These bushes provide two functions: firstly they ensure extremely accurate registration of the propeller as the bushes interlock with milled recesses in the propeller faceplate. They also reduce the size of the hole in the engine power flange to the correct dimensions for the captive propeller bolts. They were a very tight fit in the power flange! It took several attempts to get them all fully home, assisted by a little lubricant.

With the the bushes installed, it was finally time to fit the prop! There is an oil seal on the propeller that sits on the engine power flange and this was carefully cleaned and oiled. A leak here would be less problematic than at the rotating joint but it would still be a nuisance, so I did everything I could to ensure a good seal, cleaning the flange and lubricating it well.

The prop fitted easily and perfectly on the power flange, engaging with the six bushes, which held it firmly in place whilst the prop nylock nuts and washers were attached. The nuts were torqued up to the required tightness and there we were, propeller installed!

Not quite though! Now to sort out the hydraulics.I connected the hydraulic line from the electro-hydraulic pump to the rotating joint easily enough. Now to fill it with hydraulic oil.

Received wisdom is that the way to do this is using an empty sealant cartridge as an oil reservoir. The applicator is a perfect fit in the filler hole and it provides a small head of oil pressure to help drive out the air. It's also generally agreed that it helps to lift the nose of the aircraft so as to get a greater head, so I did that as well.

I poured a small amount of hydraulic oil into the cartridge and watched with satisfaction as it slowly drained into the system. More oil! Now, exercising the electro-hydraulic pump the oil gradually filled the hydraulic pipe and started running into the pump. It took a while but eventually all the air had bubbled out and the system was full of hydraulic fluid. Removing the cartridge reservoir without getting oil all over the prop was a challenge. I was only partly successful!
The screw cap that closes the filler hole turned out to be a bit of a challenge. It needs to be screwed down very tight otherwise hydraulic fluid seeps out when the system is put under pressure. Eventually I had a oil-tight system and could now play with the pitch control.

It works! In manual mode I was able to adjust the propeller pitch from the Flybox controller, demonstrating the range from fully fine to fully coarse. It seems like such a simple thing but it is the culmination of several months of planning and quite a lot of engineering work, so it was extremely satisfying.


By now it was getting dark, so it was too late to do any ground runs. I spoke with Tom, my inspector and he will come down on Wednesday (two days from now) to check out my handiwork and, hopefully sign everything off. I can then get on with the ground runs and flight testing as time and weather permit.

Not a bad note to end 2012 on. Happy New Year to all my followers and see you in 2013 for an update on the flight trials!

Thursday, 27 December 2012

Just need to fit the prop now...

With the lousy weather, Christmas and all that, progress has been slow but nevertheless I am now ready to fit my new VP propeller. All the preparatory work is completed and I have a permit to test fly the new prop that is valid until 17-Jan-2013, which hopefully should be long enough for me to get the prop fitted, inspected, released for test flying and, at long last, flying.

The last preparatory item to be completed was the installation and testing of the propeller speed control. I spent a lot of time trying to find a way to incorporate a quadrant-style control lever, in the belief that this would be more consistent with the existing throttle layout and also more intuitive in use. However, the mechanics, given the space available and the position of the throttle and (especially) choke controls eluded me in the end.

I have therefore reverted to the original plan, which was to use a linear (slider) pot and mount it alongside the throttle/choke levers. There is plenty of space for this and the end result looks fine. More to the point it also feels fine from an ergonomic point of view.

The blue throttle control knob posed an interesting challenge. Firstly, where to get one? This turns out to be difficult and ridiculously expensive, in the way that parts for C of A aircraft usually are. In the end, I decided to obtain a cheap flight simulator control quadrant and steal the blue knob from that.

I then had to fabricate a metal collet to fit onto the slider pot control lever and create a snug fit into the much larger mounting slot on the blue knob. A bit of work with some rectangular aluminium rod soon yielded a very satisfactory, robust solution.

The result looks pretty good, I think. As required by the LAA, the lever is fully labelled and the picture shows the finished article installed installed in G-JONL.

With the wiring completed I was then able to calibrate the controller to set the max/min speed ranges that the control can select. The maximum is a known quantity, 5800PRM and, in fact, that is actually the limit set in the Flybox controller, since that is the specification for the Rotax engine. For the time being I have set the minimum as 4600RPM, although I don't think I will ever want to select such a low speed cruise RPM. This will, of course, all be sorted out in the test flying programme.

So, I'm ready to go with fitting the prop. The weather is wet but mild over the next few days, so that seems like an ideal time to get moving!

Friday, 21 December 2012

LED landing light

I've always envisaged fitting a landing light to JONL, not so much in anticipation of night flying, which is, of course, not permitted in permit aircraft, but rather as an aid to visibility.

To that end I installed the necessary wiring, switch and contact breaker as part of the original build. However, when it came to installation, back in early 2010 I was unable to find a suitable LED light that combined high output with small size and reasonable cost, so I left it as an installation option for later.

At this year's LAA rally I came across a new vendor, Bailey Strobes, who had just what I wanted. An LED that is compact yet very bright and with a mounting that would be suitable for attaching to the underside on the engine cowling. A unit was immediately purchased and about three weeks later arrived at home, where it has waited patiently for me to get round to fitting it.

The time has come! Last week I installed the LED housing on JONL and then set about mounting and aligning the LED. The result is very satisfactory. A quick test flight followed and ATC reported that the light is bright and has good beam width.

Another little job completed! Now all we need is for permit aircraft to be allowed to fly at night.

Tuesday, 11 December 2012

Slow progress

It's really been too cold to get much work done on the new propeller.

Nevertheless, I did spend some time yesterday on a revised mounting arrangement for the propeller speed control. This is slightly awkward as there isn't a lot of room in the area around the throttle. An earlier design turned out to be no good, as it put the new prop control lever too close to the throttle/choke levers.

Anyway, it looks as if the new mounting arrangement will be OK, so today I am doing the associated electrical wiring. The prop control is actually a 5kΩ linear potentiometer to which I will attach a lever with a friction device to stop it flopping around too much. The controller can be configured for any range of movement, so although it is a 270° potentiometer, there is no problem with only using around 80° of arc as the control range.

Meanwhile, I've put the spinner in for painting at my local shop and should have that back some time in the next week to ten days.

It's starting to look like fitting the propeller will have to wait until the new year now. Not really a problem - the aeroplane is flyable as it is with the current propeller, so there is no real imperative to rush things.

Friday, 30 November 2012

Brrrrr!

Why do I always seem to choose the coldest days to work on my aeroplane? Hangars are chilly places at the best of times but when the outside air temperature is minus 4°C then they are like working in a cold room!

Well, anyway, today was very cold so, naturally, I was working on G-JONL in the hangar at Carlisle. I planned to get the electrical installation for my new propeller under way but I needed to keep the aircraft airworthy, as I intend to fly on Sunday.

Notwithstanding the cold, it was a successful day:

Firstly, I installed the hydro-electric pump. This is a fairly large piece of equipment and there was only just enough room for it on the firewall, to the port of the oil tank. This actually turns out to be a good place for it as the hydraulic piping has an easy, direct path from the pump to the rotary joint that fits to the engine gearbox.

I had pondered at some length how best to mount this unit and in the end I used some aluminium angle to provide a mounting perpendicular to the firewall. This has the considerable benefit of making it very simple to remove the pump for servicing, etc. which would have been much harder if I had decided to mount it directly to the firewall.

With the pump installed, it was time to turn my attention to the electrics. The Flybox propeller controller replaces the existing analogue RPM gauge, which was anyway something of a duplication as the D120 engine management system has a digital tachometer. Much of the wiring was already in place but I had to provide a higher capacity source of +12V to drive the pump motor and, of course, install new wiring to the pump and to the prop speed control lever alongside the throttle.

Several hours later, with numb hands and frozen fingers, the job was completed. I applied power and Lo! the controller burst into life and I could adjust the pump in manual mode.

I didn't have time to complete the installation of the prop speed control and anyway, I need to do some more metal bashing for this, as my original design is not quite right. Nevertheless it was a successful day and considerable progress was made. The aircraft is ready to fly on Sunday and that will also give me a chance to check the the tachometer function in the Flybox controller is working OK.

The journey home was an opportunity to thaw out, with the climate control turned up full bore and the heated seats on high!

Tuesday, 27 November 2012

Inspector says YES!

I met with Tom, my ever-helpful LAA inspector last week and he has approved me starting installation work on the new variable pitch propeller. We also checked out the nose leg and found no evidence of any cracks, so that's something of a relief.

I'm now gathering the necessary materials and tools together and should be able to start on installing the propeller controller and electro-hydraulic pump later this week. I'll still be able to fly the aircraft whilst this work is in progress - not that the weather is up to such extravagances at the moment.

When I was at the LAA rally back in September, I bought an LED landing light that I intend to fit at the same time. When I first designed the electrics for JONL I envisaged a landing light and consequently installed the necessary wiring, switch and contact breaker, so this is a relatively simple addition.

Well... it all gives me something to take my mind off the dreadful non-flying weather!

Wednesday, 21 November 2012

Cracking up?

I received a letter yesterday from the LAA requiring me to check the nose-wheel fork within the next five flying hours. Apparently there have been some instances of cracks developing where the fork is attached to the nose-leg.

Hopefully this isn't going to be a problem on G-JONL but it's got to be checked and it is very much a potential airworthiness issue - failure of this part would be at the very least expensive and could even be dangerous were it to happen at any speed.

As it happens I will be at the airport tomorrow to discuss the new variable pitch propeller installation with my inspector, so I plan to dismantle the nose-leg while he is there and, hopefully, get it signed off as satisfactory. Watch this space!

It's here!

The Idrovario variable pitch propeller and associated gubbins has arrived chez Westmorland Flyer this morning. So I spent a bit of time today familiarising myself with all the various parts and thinking about how I will go about installing the prop on G-JONL.

I decided to wire up the electro-hydraulic pump and constant speed controller on the workbench to see how they operate. It all seems to work, in manual mode, at least. I can control the position of the pump from the controller and demonstrate that the fully fine/coarse end stops work properly. Further checking will have to wait until the system is installed and I have the engine running.

Electro-hydraulic
pump
This lash-up has also enabled me to determine the actual current requirements for the system. The manual says to allow for up to 7 amps, which I must say I thought was rather a lot. And so it turns out to be. The quiescent current is just 50mA and with the motor running the current requirement is steady at 500mA. Certainly there is a start-up surge and that is hard to measure accurately but it is of very short duration and I suspect no more than an amp or two peak, so that really isn't going to be a problem.

One of the things I will have to think about is how to mount the electro-hydraulic pump. It's a rather awkward shape, approximately cylindrical, around 4.5cm in diameter but with various appendages and it's about 34cm in length. There are no mounting brackets, so I will have to fabricate something and work out how best to attach it to the firewall. Things are quite cramped around there, so I hope I can find sufficient space. Others have done it so I can't imagine it will be a big issue.

I need to work out how to implement this new prop in such as way as to minimise aircraft down time. Not that it is exactly prime flying weather at the moment but I would like to be able to take any chance that does present itself!

Sunday, 18 November 2012

Time to roll up my sleeves

I've just been advised that the new propeller has arrived in the UK, so with a bit of luck I should have it this week. I have to decide when to take the aircraft off line to do the work - I'm guessing it will take a few days and then there are all the inspections and so on before I can request a permit to test fly the new configuration. So realistically I think I am looking at a few weeks yet.
Meanwhile, I have an airworthiness Information Leaflet from the LAA, requiring me to check for cracks on the nose leg wheel fork. That came as a bit of a surprise! As it, too, needs to be inspected by my engineer, I think I may try to do both jobs at the same time.

Looking forward to receiving my new toys!

Tuesday, 23 October 2012

Return of the Blogger

Dear oh dear! Well over a year since I last posted anything on here. My excuse, if one is needed, is that I have been far too busy flying G-JONL. She continues to fly beautifully and hasn't needed any significant work beyond normal maintenance in the 2.5 years since she first flew.

I thought I should resurrect the Blog because I am about to start on a fairly major upgrade - fitting a variable pitch propeller. I alluded to this 18 months ago and I've now decided to go for it. I'll be posting more about this over the next few weeks but in the meantime, it is appropriate to issue a general update...

I now have a little over 200 hours on G-JONL and have explored the length and breadth of Britain in the process. Another annual has come and gone without any problems. There have been a couple of mandatory mods that were easily implemented but apart from that no out of the ordinary maintenance has been called for.

So what's changed in the last 18 months?

One thing that irritated me and finally spurred me into action was the inordinate time taken to get the oil temperature high enough, especially on cold mornings. Sometimes the temperature would struggle to even get to the 50°C  minimum required before take off. I took advice on this and eventually fitted an oil thermostat during the 2012 annual.

What a difference! Not only does the engine warm up in a faction of the time, it also stays warm when out and about on cold days. It was particularly noticeable that the oil temperature would decrease quite alarmingly on a long descent in cold air. That problem has gone completely now and the oil temperature is stable regardless of flight profile.

I also took the opportunity at the last annual to fit the slow-start module that is generally acknowledged as improving starting on Rotax engines and reducing the tendency to "kick back". In fact I hadn't really had too many problems with this but as I had the kit I thought I might as well install it and get it signed off. It works just fine and it has probably improved the starting slightly so I'm content enough.

So I've not been completely idle! But I think that the last couple of years or so has been mainly about flying rather than tinkering. That's about to change a little so look out for further updates to the Blog in the next few months.