Electric Twister - more photos

Can you tell I love this thing?

I see they have opted for the Adrian Hatton style of securing the gear leg fairings to the fuse rather than the gear leg. Also note the NACA inlet on the underside - no doubt for cooling of some component.

Woodcomp prop. 146 knots cruise!

The motor is tiny! It weighs just 13kg but puts out 100KW (approx 134hp). A big battery pack up front to control the weight and balance plus batteries in the wings too.

A very spartan cockpit.

Videos of Electric Twister

What a sweet machine.

WANT!

Nice HD video here with no sound:

https://youtu.be/2f9iovtnRwU

And this one with a short write up and some sound. 

http://www.aeronewstv.com/en/industry/general-aviation/3549-silence-twister-the-first-swiss-electric-aerobatic-aircraft.html

2 steps forward, 3 steps back

Where to start?

As the engine was running sweet using fuel from the Jerry can then I assumed it would run sweet from the wing tanks now that they were cleaned.

How wrong!

A second lot of ground running from the wing tanks gave exactly the same symptoms as before, 'catching' when I changed throttle settings and generally not sweet, smooth running.

This was using the master fuel pump rather than the backup pump - which we know is damaged in some way. In fact when I did try the backup pump this time it died completely.

I've been filming the Dynon so I can analyse the readings later on at leisure.

Compare the readings below to see the difference - the fuel pressure is different in the second lot of running which would indicate a flow restriction in the wing tank to fuel quick disconnects at the wing root. From the first test we know that the flow is good from the wing root to engine and back as it ran sweet from the Jerry can.

Funnily enough the tank pickup to wing root is the only area of fuel line that I did not flush out so perhaps the restriction lies in the flop tube pickup - which does have smallish holes in the brass end.

Despite the apparent sweet running from the Jerry can you can see that the fuel pressure is still slightly above normal - which should be 43.5 psi according to the UL Power manual. It's 49 psi from the Jerry Can and 53.4 psi from the wing tank. Max permitted is 55 psi.

The fuel lines I am using are above the minimum diameter required so I'm not sure why the pressure is so high.

Anyway we will get to the bottom of this problem eventually but now onto the other problems!

I tried to calibrate the fuel sender but moving the min level dial had no effect to the gauge. After reading the instructions again I remembered that I shortened the fuel probe - which is okay to do - but you must re calibrate the sender when you do so. This can be done with a Multimeter which I rigged up but again it did not work. A further investigation with the Multimeter revealed that the sender wire (which should only have a reading of 100mV or less) was reading 11.7 volts so there is a mistake I've made with the wiring somewhere along the line that is pushing battery voltage levels through the sender.

Something to investigate when I take the instrument panel off, which I have to do anyway as I have to wire up the Red Cube to the Dynon for fuel flow info.

Another problem was with the gear leg fairings which sit at the top of the gear legs and fair in the leg to fuselage junction and cover the hole there. As you already know these do not fit the fuselage very well at all and are tight on the gear legs. I stupidly fitted them with the fuselage upside down and with no weight on the legs, so the holes I have tapped into the legs for the attachment of the securing bolts are never going to line up now that the gear has the weight of the aircraft on it.

I was thinking of doing what Adrian Hatton did and securing the flat plate area of the fairing to the fuselage and then leave the bit further down un-fastened so that this becomes the area that moves when the gear flexes but Pete Wells warned against this saying that I need to use the factory method as the gear leg flexes so much that it will crack the fairing. 

So I've put flock into the old holes and will redrill and tap out new threads for the securing bolts soon.

And now the final problem - we always save the best (worst) for last!

After the second lot of ground running I returned to the airfield to find yet another fuel leak from the Starboard wing tank. This is not coming from the same area as before as I pro sealed the inside and outside of the securing bolt this time and this area was dry - no leaks.

The leak is coming from the tank somewhere. quite low down as I found when I was draining it and monitoring if the leak was still coming out or not. 

If I'm lucky I think it will be coming from the hole made for the fuel drain and tank vent. This is the logical first port of call as there was a hole made in the tank for these items to be fitted and if there is the tinniest of gaps in the flock then a small leak would happen. It is indeed a very small leak as the speed of the fuel coming out was very very slow. 

Anyway so that dripped out all over the fuselage bottom and stripped the paint off again just like the other side (the previous leak happened on the Port side).

So now we have matching shittyness underneath on the black paint. No problem here as the fuse base has to be repainted anyway in it's entirety. This just proves that the wing root area and fuselage base were not painted correctly all over.

Hopefully I will have a more positive post next time round.

Trying to calibrate the fuel sender - I had to jury-rig up these wires to connect up the sender to the power source and give access to the dial on the sender at the same time.

1st ground run from Jerry Can after sustained full power run and back to warm up revs - fuel psi is okay here.

1st ground run from Jerry Can at Max Static RPM. Good that the oil temp stabilises at this figure but bad that the fuel pressure is so high at 49 psi. Still running sweet at this though.

2nd ground run from Wing Tanks this time. Note the higher fuel pressure. 53.4 psi now. This is from the start of the run so the CHTs and EGT's are lower.

 

Final inspection, ground running again and more.

I’m very happy to report that G-FUUN went through it’s final inspection with no issues!

Pete Wells flew over on Tuesday evening in his Twister and had a thorough look at everything and long chat with Rex my inspector.

Pete concluded by saying “Well, I can’t find anything wrong with it”.

High praise indeed.

Rex has gone to France for 1.5 weeks so we will complete the last lot of paperwork for the permit to fly on his return. Then it will be in the hands of the LAA as to how long it takes for all this paperwork to be processed.

I’m thinking 2 months at the moment for that to happen - if it happens sooner then I will be pleasantly surprised. This now puts us into November for a first flight - not a month known for it’s balmy weather...

Regarding the rough running engine. I took the fine filter to pieces and was surprised to see that it was clean inside. Before disassembly, after waiting 3 days for the residual fuel in it to evaporate, I tried the blow test again and could find no real difference between it and a new filter. So the fine filter was not the cause of the rough running.

Time to do some more investigating.

I phoned Pete Wells and asked what static RPM he got with his Hercules and he said about 2,400 to 2,500. I am getting 2,500 so that is all good. So the engine is revving out correctly and giving the correct static RPM.

He said that with his GT props one is slightly finer pitch than the other - so Chris Burkett can keep up and accelerate better when formatting on Pete (Chris has the finer pitch propped plane)

Pete also said so long as he gets 2,400rpm static then they are good to go.

I found out on my second engine run that the backup fuel pump was not delivering the correct PSI - it dropped to 36 PSI and stayed there and is also making a funny noise - so I am going to replace it. That would explain my rough running engine when using that pump. The other pump has the correct PSI.

When run on the master fuel pump the engine runs sweetly and smoothly.

I also found out from Mark Jones at Galaxy what happened to the fuel pump that failed last year - you may remember when I switched it on for the first time it ‘popped’ then failed to work. Mark’s reply is below:

Indeed there was a fault, ULP looked investigated it and found a manufacturing fault by the pump manufacturer. A small piece of swarf was found in the armature and that is what jammed it up. A very rare and isolated case.

Quite a few little jobs to do now. A compass swing, and calibration of the Dynon compass, fuel sender calibration and a few other things, not to mention that paperwork!

I've been getting many compliments on the cowl and G-FUUN's general good looks.

Further evidence of the paint screw up. Note that the orange (without clear coat here as it is under the black) has chemically bonded to the primer (unlike the black) and has not been affected by the fuel.

 

Twister TV star

https://youtu.be/Q1HoRWTxqJc

Pete races a Jeep for a TV ad. 

Just like on Top Gear it's a fixed race so the Jeep 'won'.

Mystery Twister identified

An electric Twister!

How cool is that.

This is the future for pure aerobatic machines for sure.

Even better with a Twister as it is an easy de-rig to trailer to an event should you need to.

http://www.hamiltonwatch.com/news/hamilton-reveals-first-swiss-electric-aircraft-made-aerobatics

And weighing in the left corner of the hanger is...

...G-FAAT

at least that's what I should change the rego to.

309kg to be exact.

This is not overly surprising given the mods.

Pete's heaviest Twister is 296kg and Johan's is 303kg.

As it is my first build (never say never) I did the usual thing and made things too heavy. Lucky for us that cruise flight is not that effected by weight as induced drag in the cruise is only 5% of total drag. Hopefully my 'speed' mods will recoup some of the drag points back from the extra induced drag from the weight.

Yesterday I washed G-FUUN and used Car Lack polish on the upper surfaces. This is what the glider lads use so it must be good stuff. It certainly feels silky smooth to the touch now. I must have lost a kg of sweat doing this as it was the hottest day in September since 1911 yesterday. That might help me get under weight for G-FAAT?

The last few days have been spent cleaning out the fuel tanks. It's a shitty job but someones got to do it. I did 9 cycles of Vaccum, part fill with petrol, shake around and upside down, drain petrol, clean out areas I can get to with rags, boroscope inspection then repeat. So 9 cycles of this on the Port tank until it was clean then 8 cycles on the Starboard tank. Both are immaculately clean now - even in no mans land in the middle.

This afternoon after the weighing I started to strip out the filters.

The pre filters were surprisingly not that dirty.

After much swearing and skinned knuckles I had the fine filter out and gave it the 'blow' test. Compared it to a new fine filter the difference was huge - very easy flow through the new filter and asthmatic flow through the old filter.

So that was the root of the problem with my rough running engine - the fine filter was all clogged up.

Lots more work to do before final inspection (proper one this time) on Tuesday.

Roy Sears of EeziWeigh doing his thing.

Roll on wireless scales.

Tailplane has to be level for weighing.

Porky Pig!

Pre filters cut open

Bit of crap but not too bad.

Stripping out the filters and return line.

A new Twister at Termikas

Just spotted a new Twister being built in Lithuania by Termikas.

Not sure what engine this has in it though?

Looks like it could be liquid cooled. A Rotary perhaps?

Mystery Twistery

A day that didn't go as planned

Tuesday did not go according to plan.

The weighing guy phoned me in the morning to say he had an accident on the motorway - some one rear ended him. So he was a no show.

Rex only did a light inspection as he wants to wait till Pete Wells is there for the final inspection where we take everything to pieces.

Anyway there is more than enough to be going on with in the meantime. I have a list of things to do from Rex.

Rex also has very kindly lent me his Boroscope to see inside the fuel tanks. It's really handy to see the state of 'no mans land' in the middle section of the tanks. Just look at the crap in the photo below!

Also re the paint problem I noticed that the landing gear fairing has not been affected by the fuel at all - despite being soaked in it for 48 hours the same as the surrounding fuselage areas. 

The fairing has clear coat on it and Rex agrees with me that areas of the base of the fuse do not look like they have been clear coated - it is patchy in places. Rex also said that the fact that the black and primer is not chemically bonded to one another is wrong. 

I will also seek the opinion of Pete Wells as another paint expert to see what he says before I take it any further.

View inside 'no mans land' in between the baffles in the middle of the tank - it's full of crap!

Note the gear leg fairing which has not suffered any damage due to fuel despite being soaked in it the same as the fuse.

Sywell Rally and UL Power inverted oil sump

I had a great day out at Sywell yesterday.

The top men from UL Power were there and I had a good chat. They agreed that the most likely cause of my rough running engine was fuel supply.

Also interesting to see was a cut away of the UL260iSA sump - how the inverted oil pickup works.

More pics on this link: https://www.flickr.com/photos/andymac53/albums/72157673355339965

UL260iSA inverted oil pickup in the sump.

The Good, The Bad and The Ugly

First the good.

I spent Tuesday putting G-FUUN together at the airfield. 

All went well, the tail planes I am very pleased with - how the mod works and the extra security it provides.

The next day (after moving 5 other planes out of the hanger first - as mine was at the back) I fueled up one tank and decided to do some engine runs and taxiing.

The good news is that the cowling and oil cooler scoop seem to be working very well. The oil temp on a sustained high power run (for 2 mins) stabilised and then actually came down a little bit to hold at 92 degrees. This is exactly in the middle of the required range of 80 to 100 degrees. I was not facing into wind either which I thought would be a better test for it. So far so good...

The cowling and sealed plenum are also doing their job very well. The front two cylinders were actually running too cold and were about 20 degrees cooler than the rear cylinders. I have some plates in front of the front two cylinders already but it seems that they will need to be made bigger still to even up the temperatures.

Now the bad.

Although I thought I had cleaned out all the crap in the fuel tanks I was very wrong. This extra crap got sucked into the pre filters and has most likely blocked them up. Maybe even the fine filter too.

This resulted in rough running of the engine at most revs and a poor throttle response. It did run smooth at the warm up revs of 1,200 though. Maybe the fuel supplied just happened to be correct for the air at these revs - as the ECU does not know how much fuel is being supplied - it just knows throttle position and air temps, pressures etc.

This meant that the engine would not rev out properly on the high power run and the best it could do was 2,500rpm.

After I taxied back and investigated inside the tank there again appeared a heap of crap. I think some of this has come from the top of the tanks and also the 'no mans land' in the middle in between the two baffles which make it impossible to get to 1/3rd of the tank.

Lots more cleaning of the tanks and a thorough flushing out of all the fuel lines plus new pre filters (and a fine filter too I think) and we should be okay.

I had a long conversation with Pete about this and he agreed that according to the symptoms I described that this was the most likely problem.

I also had a chat to Mark Jones (UK agent for UL Power) yesterday at the LAA Rally and he also agreed that this was the most likely cause.

I tested both ignition systems and saw no change and also the EGTs were all the same so it's not an ignition or blocked injector problem.

In the video below you can hear the fuel pumps straining away so they may need to be replaced too if they have become damaged.
Also Pete told me that he does have one 'Red Cube' (Fuel flow meter) installed in the fuel line so he can monitor flow rates - it is an early warning sign if the rate drops that the fuel filters are becoming dirty or blocked. 

If you'll remember I was going to have two cubes installed so that the actual fuel used could be calculated but it got too complicated and expensive so I opted not to have any at all. This is a mistake and so I will be installing one of the Red Cubes back in the return line. 

As we know from my fuel flow test the other week the hourly rate delivered by the fuel pump is 136 litres so if we are burning 17 litres in the cruise then the Red Cube should show a rate of 119 litres per hour in the return line. The most it should drop to should be 109 litres per hour as this would be on full power which is 27 litres per hour. Any lower figure than the difference between flow and usage and it shows a restriction in fuel flow which would automatically ground the aircraft and warrant further investigation.  

Video here: https://youtu.be/YrdZcJ8ZhSA

Now the ugly.

This afternoon I went out to the airfield to configure the Dynon a bit better and start on cleaning out the fuel tanks when I discovered a pool of fuel under the aircraft.

A fuel leak is never a good thing but in this case it was even worse as the fuel had got to the black paint and eaten it. The paint just peeled off. Only the black top coat mind - not the white primer underneath. This just seems wrong to me - that automotive paint cannot handle exposure to automotive fuel. I think something is really wrong here but cannot begin to think about it too much as I will just get more upset. There was another home builder at the hanger (who has painted his own aircraft) and he agreed that something was not right about the paint coming off the way it did.

The photos below reveal just how ugly it is.

The leak BTW was coming from the one screw that I could not Proseal as it is the fastening screw for the threaded tube which holds the fuel tank end plate on and needs to be clear of Proseal to get on and off.

I thought I did this up fairly tight and didn't want to go any further in case I damaged the threaded tube. I think the rubber seal may be to blame as it seems to be protruding out around this area.

It's a bit strange that it leaked now as it did not leak when I filled the tanks up with fuel to clean them last week.

Assembly in the hanger

All done and with the cover on and 'noodles' to protect the wingtips from hangar rash.

The Good

The Ugly

Fuel shouldn't do this to paint.

Peeling off top coat but the primer stays intact - this isn't right.

The full extent of The Ugly.

The cause of the leak - from the screw that holds the tank end plate on.

All this crap appeared in the tank after the taxiing.

Strips of paint that show that the primer was not chemically bonded to it.