Tuesday, 29 September 2015

Great photo

A really nice shot of Chris Burkett in close formation with Pete over Gibraltar.

Notice the inlet (in white on the top of the cowl) for the engine air.

It seems like an attempt to get colder more high pressure air into the engine for more power.

If it's not sealed to the rest of the low pressure area of the cowl then the penalties could outweigh the benefits, because as we know introducing high pressure air into the low pressure area of the cowl reduces the difference in  pressures and thereby reduces cooling efficiency.

It will be good to have a closer look at what Pete has done here before drawing any final conclusions.

Monday, 28 September 2015

2000 hours

On Saturday I passed 2000 hours.

I had a large whisky to celebrate...

Tuesday, 15 September 2015

Week 214 - Flap drive and engine start (attempt)

Hours to date: 1984.75

Another couple of weeks of (mostly) backwards progress I'm afraid.

I figured out that the throttle cable that was supplied with the kit was a solid wire type and more suited to a choke than a throttle. So I bought a new cable and installed that - the action was now much smoother and not catching on anything but when I looked up to the engine I found that the full travel of the lever in the cockpit was only giving 0 to 40% throttle on the engine.

So this will need a major mod to fix. I will have to remove the existing lever and put in a vernier type throttle - the same set up as Pete has. This will need a mounting point and cover built into the side of the cockpit. Joy!

When testing the fuel pumps one worked perfectly and when I tried the other one it worked for about one second before stopping and making a 'pop' noise. So one fuel pump has failed - I will see about getting a replacement sent.

Then I went to try an engine start for the first time and despite giving it a good crank it did not want to fire up.

As there was no popping or any un-burnt fuel in the exhaust pipe then this led me to believe that it was the ECU that was not working. The ECU controls both the ignition and fuel injectors. 

After a bit of fault finding I found that the fuse on the power supply to the ECU was blown. Upon replacing it and turning it on again the fuse blew again within one second so there is some fault in the wiring to do with the ECU. I've ordered a circuit testing device that is non invasive, that is, it can detect current through the insulation of the wire so no need to butcher my wiring to find the fault (we hope).

I also found a couple of small fuel leaks from the fuel pumps - where they connect to the joining tube and fine filter. The copper washers there obviously were not done up tight enough. I will sort that out when I replace the faulty fuel pump. Good to find these things before bonding on that lower fuselage panel methinks.

Let's end on a positive note shall we!?

I managed to bond in the plastic bearings for the flap drive and then rivet everything together. All works good! As I said last post I would not want to do this job after the fuselage base had been bonded on.

The order to do this in (after the plastic bearings are bonded in) is: 

1. Put wings on and align flaps to fuse with clamps - making sure that the flap pins are fully in the plastic bearings on the drive ends.

2. Rivet on the loose bearing end - access will only allow a couple of rivets at this stage but that is okay for the moment.

3. Once you are happy with everything drill and rivet the motor arm - again 2 rivets is enough here.

4. Take the clamps off and fire up the electrics. Test the flaps for operation.

5. If all is well mark the tube and arm position with a pen (not absolutely necessary as you have the holes already drilled to line it up again) then drill out the 2 rivets previously put in the arm - so the tube can now be rotated 360 degrees.

6. Rotate the tube in stages (by hand) to complete the drilling and riveting of the loose bearing end.

7. Align the tube again with the motor arm to your mark (and holes that were already drilled). Rivet those two holes and complete the rest of the drilling and riveting. 

8. You're done - go have a beer.

As you will have noted I pre-drilled both the motor arm and loose bearing end to make life easier.

Hopefully I will have a more productive next few weeks!

New throttle cable set at idle

Full throttle in the cockpit is only giving 40% throttle at the engine end - time for another mod!

All set up for the engine run - chocked and tied down to a tree.

Oil cooler inlet taped in place for (supposed) engine run.

Flaps working for the first time! See video below.

Flap drive bearing bonded in with flock.

Flap drive all done - tube riveted to motor arm

Loose end also now riveted to tube.

Few small leaks from the copper washers here - need to really nip these up tight.

Flap drive working for the first time - yes I finished the job in the dark!

First attempt at an engine start.

Tuesday, 1 September 2015

Week 212 - Flap drive, Control surface gaps and engine crank

Hours to date: 1964.5

Another few weeks of very little progress - too many social things going on this time of year.

Good news is the Push to talk is now working. It was such a simple fix - just plug in the earth wire! Doh! What is it they say "always look for the simplest solution".

On the Fuel Flow things are not quite as straight forward as my last post suggested. I contacted Dynon and they said they do not support the UL Power ECU fuel flow output and recommended the red cubes. However they then did say it is worth a try so we will see.

The Dynon already has a very good fuel computer in it which if calibrated should give very accurate fuel usage. The flow is based on engine revs.

Onto the flap drive.

Firstly though I had to make sure all the control surface gaps were correct. To do this Pete uses Nylon bushes on the pins. So that's what I'm doing. They are easy enough to cut down with a mini hacksaw to the required width.

I'm aiming for a 2mm gap on all surfaces.

We had a few nice days so I decided to wheel the Twister outside and get going on the flap drive again.

Good news is the flaps went straight on - sort of - the pins were only 1mm out vertically - so a little Dremel work on the flap tube hole saw this fixed and they went in easily. They were in perfect alignment horizontally.

When I was making the flaps I made the pins purposely too long. So then it was a simple case of reducing them down to the required length. If they are too short there is nothing you can do except start over with the flap which would not be good.

Next thing to do is wait for 48 hours of nice weather so I can bond in the flap drive plastic bearings - which has to be done outside for me as there is not space inside the garage to get both wings on.

Once those bearings are bonded the loose flap drive end needs to be riveted to the tube  and then the drive arm is also riveted to the tube. I am not leaving this off until after painting - as the manual suggests - I think it would be a major pain to rivet this when the bottom fuselage is bonded on! I'm not worried about the paint in the wing root as this will not be visible when the wings are on.

As all the wiring is now done I decided to fill the engine with oil and give it a crank over to get the oil through the system.

Due to my oil cooler mod and the length of the hoses it means I have about 600ml more oil in the system than a standard set up (3.5 litres) which I think is only a good thing as these engines don't have nearly as much oil as a Lycoming. It will help with keeping the oil cool.

It took a bit of cranking then checking the level - which had gone down. Refilling to Max and then cranking again until I got a reading on the Dynon of oil pressure. So all the air has been purged from the system and it should be good to go for an engine start in 2 weeks time.

I'm still not happy with the throttle set up and am changing that so will report on that in my next post.

Nylon bushings cut down with mini hacksaw

Gap of 2mm on Aileron

Bush in place.

Getting wing on for flap drive job

Add caption

Almost right - need to go up by 1mm or so on the tube to match the pins

Pins are too long on purpose - cut down in stages to fit perfectly

Fuse and flap do not line up here so a bit of an extension to the fuse is required.

Okay on the Starboard side though.

Flap/Aileron gap too tight here - now fixed with another bush
Video of Engine cranking.