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!