Sunday, 6 September 2020

Tiger Trophy aeros comp

Yesterday I competed in the first official (British Aerobatics run) comp this year.

The Tiger Trophy at Leicester.

It is a difference type of comp with all pilots from all classes competing against one another with one unknown sequence which gets progressively more complex the higher up the class goes.

I screwed up my spin - having not practised a one turn spin ever that I can remember - I am so used to doing 1 and a half spin turns that I did not recover soon enough and over rotated. So a hard zero for me on that one. The other figures flown scored well and had I done the spin right then I would have been right up there in the top 3, as it was I finished 10th from 15 competing.

A good fun day out despite my screw up.

A mate videoed part of my sequence with his phone so this is best viewed on a big screen.

Monday, 17 August 2020

The original Twister

The RC model that started it all.

It now hangs on the living room wall of Mike Friends house.

The origin story of the Twister is that Matthias and Thomas designed and built an RC model to compete in competitions. It was very successful and someone said "Why don't you build a full size version?". So they did and 10,000 man hours later the prototype Twister was finished, production soon followed.

Aeros comp

Due to Covid, this year has been without an aeros competition run by British Aerobatics so far.

Adrian Willis of the British Aerobatic Academy decided to run his own comp at Fenland.

It was a less formal affair with good flexibility from the organisers. 3 sequences were flown over 2 days. I had not practised any of the sequences so treated it as a training exercise and good practise for Unknowns. Excluding H/C competitors I finished 2nd both days so not bad considering I hadn't practised since March.

A recently completed One Design next to G-FUUN while the Extra 300 lands in the background.

The top 3 in each class.

Monday, 30 March 2020

Aerobatics FUUN

The final video that will form part of the TV/Slideshow for Friedrichshafen 2021.


FUUN with friends

Another short video that will form part of my TV/Slideshow at Friedrichshafen 2021.


Tuesday, 24 March 2020

Twister 2.0 - Unlimited Aeros capable?

Could the Twister be modified to be capable of Unlimited Aerobatics competition?

We think so.

So long as endurance is not your prerogative then with an electric motor of 200kW+ and modifications to the control surfaces - specifically the Ailerons - larger and with a horn balance to increase their 'throw' - and a larger elevator, again with horn balance (these act as 'power assistance' to the controls in place of spades) then it's quite possible a Twister could compete at Unlimited level.

Below are three pics.

The first is a 'mild' upgrade with no new molds or major changes to existing layout needed. The flaps are gone and have been replaced with full span Ailerons.

These ailerons also have a horn balance on the outboard section, which is where the mass-balancing weight would now be so that 'throw' is not limited as it currently is by being inside the wing. The outboard hinge is in the same location but on the inboard section of the tip rather than outboard as is normal on a Twister.

The elevators are a little larger in area, also with a horn balance. 

The rudder remains unchanged. The standard rudder in a Twister is already very powerful and overly sensitive compared to the other controls - due to it's too large horn balance - but ideally suited to this more extreme version.

'Mild' version of an Unlimited Twister.

The second version, below, is a more extreme version with a larger aileron surface area - particularly on the outboard area (where it has the most effect). The inboard section of the wing has been left without a control surface (as per the Extra 300SC).

The roll rate for this version would be 400 degrees per second. Roll rate being a function of aileron area and 'throw', coupled to wingspan (wing area ultimately).

The elevators are also larger for more rapid 'Flick rolls' and more control at lower speeds.

More Extreme version with 400 degree per second roll rate and greater speed of flicks.

The final image shows this extreme version overlaid with an Extra 330SC (currently considered to be the ultimate Unlimited aircraft, and with identical wingspan to a Twister at 7.5m). As you can see the ailerons are now of similar size. The elevators don't need to be as big because the Twister is considerably lighter than the Extra (approx half the weight).

Extreme version with Extra 330SC overlay.

Overall the Twister would need to be strengthened considerably so that it could deal with the increased G forces but also the expected higher Va and Vne needed to compete at this level of competition. This will add weight of course but I still don't think it would be as heavy as the steel framed Extra with it's heavy Lycoming 580. The power to weight ratio would be comparable or better than the Extra.

Sunday, 8 March 2020

Building FUUN video

5.5 years and 3,000 workshop hours compressed into about 2 mins of building G-FUUN.


Oshkosh Epic Adventure video

I finally got around to making a short video of my 'Epic Adventure' from 2017.


Monday, 3 February 2020

UL engine work

As explained in my post from August of last year, when I did my 400 hr service, there were a few outstanding maintenance items that I wanted to get done this Winter.

I managed to get organised a couple of weeks ago and flew up to Metal Seagulls (the UK, UL Power Agent) at Sleap airfield to get this done.

The two main items to fix were the leaking exhaust valve on Cyl 3 (with it's loss of compression) and the upgrade of the Throttle Position Sensor to the new 'Hall' Type sensor.

While I was up there, as my annual inspection was almost due, I got that done too. G-FUUN passed again without comment.

Then while we were waiting for parts to arrive back a Service Bulletin was issued regarding the Oil Thermostat failing. Good timing! The issue was the smaller of the two springs inside the Thermostat was breaking. The fix was a new grade of springs and those parts were supplied free in the UK by Metal Seagulls. 

Whilst I was taking the old thermostat springs out it was obvious that the small one had broken yet again - see pic. So that is a total of 3 failures for me with the oil thermostat. Hopefully the new springs will do the job and we won't have it fail again. I am lucky that my engine runs so cool I can actually still fly without the oil cooler working - it's certainly not a problem in the Winter although I would not want to fly without my cooler operating in the Summer.

Onto the two main issues.

The throttle sensor replacement was fairly straightforward. The biggest pain was removing my ECU as I have it located up under the footwell area of the safety cell so it's out with the instrument panel and then an awkward reach to undo the bolts. No matter, it is only the first time it's been out since it was put there and I don't envisage having to take it out ever again.

The ECU has to be removed because it has to be sent to Belgium to have it's firmware upgraded to 'talk' to the new throttle sensor type.

The whole throttle body was removed and replaced with the new body and sensor. There is also an intermediary connector to fit which converts the round plug of the new sensor into the 3 pin plug of the old connector. 

Of course the idle then needed adjusting once the engine was warmed up.

All seems well with it, although I did notice a hesitation from the engine when the throttle is moved rapidly. Slower movements are better. There was always a hesitation with the old style throttle when going from high idle to full power at take off but this new throttle seems to suffer from the brief hesitation at any setting change if done too rapidly.

Finally onto the Exhaust valve for Cyl number 3. There was a discussion with Jonathan about whether to repair or replace. In the end we decided to replace the whole head as the amount of labour involved to fix it ends up being almost the same as a new head. Also there was the problem of the leaking gasket on this head which had been there from new so it became a 'no-brainer' to replace the head to fix this issue at the same time.

All seems well so far. I need to fly it a bit more to let the head settle down but it seems to run well so far.

Hopefully we will have a good season of flying without any more issues. Fingers crossed.

At Metal Seagulls hangar for the work.
New Throttle Position Sensor, Made in the UK!
New parts. Throttle body and Hall type position sensor and the Oil Thermostat springs
The broken smaller spring from the Oil Thermostat

Detail view of the area where the leaking head gasket let combustion byproducts seep out.
General view of the old cylinder head from Number 3. 

Detail view of the Exhaust valve seat. It seems it was the valve rather than the seat that was damaged.

Exhaust valve showing evidence of damage and leak.
Jonathan cleaning up the gasket area before installing the new head.

General view of the piston and cylinder before the new head goes on.
New Cylinder head in place. Torqued down very carefully and progressively to ensure the gasket seals well and evenly.

The Metal Seagull...

Saturday, 21 December 2019

French Twister article from 2013

For some reason this article had slipped by me until recently. I bought a copy of the magazine and share the article here.

Whilst my French is non-existent I get the impression the author was very impressed with the Twister.

Sunday, 17 November 2019

Trim fail

I had a bit of a scare last week.

Just after take off I heard a 'bang' and had to use more back pressure on the stick than normal to keep the climb attitude the same.

I decided to continue to climb up to a safe altitude - 3,000 ft - before investigating what had gone wrong.

After thinking about it for a little while I concluded that one of the trim springs must have either broken or come loose.

The rest of the flight continued without incident and I made a normal landing. The stick forces were not much more than normal - thankfully the Twister does not really need a trim in the first place as the forces are so light.

That evening I investigated and sure enough the rear spring securing bolt had come right out. 

This explains the stick forward bias as only the front spring was acting against the elevator push rod tube - requiring a constant rearward force to overcome it.

I noticed that the bolt thread did not have evidence of Loctite on it so that is a failure on my part. It's taken just over 400 hours for this to happen.

I've used Loctite this time! And also added TorqueSeal to the outside so that at each annual it can be inspected for movement.

Something to be aware of if you have not used Loctite - but certainly an inspection item (with the TorqueSeal) to add to the Annual if you have already not done so.

After removing the baggage tray it was instantly obvious what had happened. The bolt holding the rear spring had worked loose and come completely out.

Closer view.

After fixing with Loctite on the thread of the bolts and also now with TorqueSeal (in Blue) which will aid inspection.

Saturday, 9 November 2019

New spinner

It has taken me many months but I have finally finished getting a new spinner installed after the old one 'departed company' in May.

In my usual fashion it has been 'modded'. I always found the original design of spinner to be a bit blunt looking compared to the rest of the aircraft, so this was my opportunity to change it's shape.

My boss loaned me an old spinner from his plane and I used that to make a 'splash mold' part off the front of it. I then combined that part with a replacement spinner that was kindly sent by Matthias.

The result is a sharper look - more Mark 9 Spitfire than the old rounded Mark 1 looking spinner.

The other modification is the addition of a front plate. This has added a great deal of rigidity and security to the attachment of the spinner, I feel quite confident it will not come off again!

The front plate is made using the same schedule as the back plate. A 3mm thick sheet of carbon is cut out and drilled to match the bolt holes in the crush plate. Then an angled flange of carbon is added to the edge, projecting forward, giving a large area of contact with the inner front of the spinner.

The spinner was fitted and aligned using a laser level before all the holes were drilled. Then nut plates were fitted to the inside of the front and back plate flanges. 12 on the back plate and 4 on the front plate. I've gone for metric anchor nuts this time round and button head Allen screws with fibre washers underneath for security as I found the Tinnermans with the sprung plate to be unreliable over time.

Everything runs very smoothly now. However I will still do a dynamic balance to see what the vibration levels are and if they can be improved at all.

Regarding the old spinner - the conclusion was that it was a substandard part. 

It was not made by the factory but supplied to me by Hercules propellors using their own mold. They had not followed the same layup schedule as the factory spinner. They only put carbon on the back inch or so where the fasteners go for the backplate - the factory made spinners have carbon all the way up to and beyond the cut outs for the propellor. Therefore the old spinner was vulnerable to cracking in the prop cut out area. 

I believe this is what must have happened, a crack formed and then quickly propagated on the fateful flight, the spinner ripping open once the high pressure air got inside and popped it off, wrenching the fasteners as it went. We will never know for sure exactly what happened as the spinner was disintegrated but the above seems to be the most likely cause. Please check your spinner if you believe it was made by Hercules as they are not fit for purpose.

Original and new shapes compared.
Front plate for added security, micro on the edge was done to form fit to the inside of the spinner.

Side view of front and back plates

All done and looking good

I think this shape of spinner suits the Twister better

Button headed Allen screws with fibre washers underneath with a front plate. This is the same standard used on certified aerobatic aircraft