Maintenance matters, fuel leaks and TPS (again)

I'm pleased to say that yesterday G-FUUN passed it's annual inspection again, so it's good for another year.

Unfortunately I've also had another series of fuel leaks.

I had originally thought they were only coming from the Ali end plates - specifically the central bolt through the fuel sender that tightens the plate (via an ali tube with a thread inside the tank) but as it turns out that was not the only cause.

I've since replaced the ali end plates with new ones and ditched the fuel senders altogether as I now have solid state fuel sender probes. The rubber seal on the Falcon gauges was changing over time and caused some leaks.

The other thing I've done to improve the end plate sealing is making up some thick rubber washers which have a slightly undersized hole drilled in them. Screwing that onto the thread and then putting a large metal washer in front on the outside helps to seal things better than just relying on Proseal. I also made up a smaller washer for the inside which is squeezed between the plate and ali securing tube.

No leaks from the plates anymore!

However recently I got another fuel leak, very small, just weeping out, but very annoying as it took me some time to find out where it was coming from.

To start with I thought it was further up the tank and fixed that supposed hole from the inside with flock - see pic below.

But that was not the cause.

I then bought a UV dye kit which consists of a UV dye and a UV torch. You mix the dye in with about 10 litres of fuel then pour that into the tank. Wait a while then in the dark shine the UV torch and you are supposed to see only the fuel and find out where the leak is from.

Well this did not really help and I ended up leaving it feeling quite frustrated as it still was not clear where the leak was coming from.

When I came back to the job the dye had actually helped as it is orange and visible in the daylight too so does point to where the fuel has been.

A tell tale orange mark from the underside of the wing near the drain finally pointed me in the right direction. It was the ali plate that is bonded into the tank and lower wing skin that was the problem. So I used runny flock to fill in the cavity around the drain and overflow/breather fitting on the inside. Being runny this found it's way into every nook and cranny of this area and sealed up the leak good.

No more leaks again (for a while anyway - fingers crossed).

I will do another blog post about the fuel senders when that is finally sorted as it too has been a bit of a saga and is hopefully soon to be resolved. The manufacturer has admitted to a faulty set of modules for these and the replacements are finally here but stuck in Customs at the moment. 

Finally the Throttle Position Sensor - it has started to fail on me again. Happening when I took of from a bumpy hard runway the other week at Great Massingham.

I checked when I got home and found that it has failed at almost exactly the same number of hours as the previous one - 123 hours approx.

Ironically the next week UL Power released a Service Bulletin which said they are no longer fitting this type of sensor to any new engines in the future. Which to me says they admit there is a problem! 

They are converting to a Hall Type sensor - which does not have the sensing parts touching so therefore is much more robust to the vibrations of an aircraft engine installation.

They are offering the Hall Type sensor as a mod to us older engine users but at a price! Around £600 which is a bit cheeky considering the Hall Sensor is a £25 part. True a new inlet block is needed and an ECU remap and additional wire but £600 is a bit rich.

G-FUUN with it's clothes off for it's annual inspection. It passed again 'without comment'.

 

New fuel sensor probes - more about those in another blog post.

Fuel tank end plates - now without the Falcon senders and with rubber sealing washers.

Rubber washers I made up to help with the sealing of the fuel tank end plates. These are working well.

Port wing off to fix this fuel leak.

I thought it was coming from this 'hole' part the way up the tank.

Which I fixed with flock but it turned out was not the cause of the leak.

This area around the drain and overflow/breather connections was the cause of the leak and has been fixed with runny flock allowed to run into the area. 

Aeros sequence card holder

Once I moved up to the Sport grade the number of figures even in a known sequence becomes too much to remember 'by heart' let alone an Unknown sequence, so I decided to make a sequence card holder.

I started off with a flat plate of carbon I had left over from another project and just made up an S shaped bracket out of raw carbon which I then bonded onto the back of the flat plate.

It utilises just one attachment point which is already on the aircraft, the top panel fixture screw.

I thought it may wobble about too much with vibration but once flying it is absolutely steady. 

The sequence card is held in place by 4 small bulldog clips - I also use two small pieces of duct tape in the centres but this is not really necessary.

A 'mark two' version of this would have a hinge on the bracket so you could raise up the holder to see the EFIS but for now I am happy to forgo seeing the EFIS for these short flights.

Formation FUUN

The other weekend I flew up to Great Massingham, which is a former RAF Base from WWII, to meet up with my mate James in his RV-6.

Some history here: https://en.wikipedia.org/wiki/RAF_Great_Massingham

After a pub lunch at the brilliant Dabbling Duck we flew back in formation, trying out some formation loops which didn't work all that well. More practise required!

The Twister is too slippery in any kind of dive and soon runs away from the RV6.

Video of our formation fuun here: https://www.youtube.com/watch?v=6iIE5GhvlwM

Approaching Great Massingham village, airfield is to the top right.

Autumn is here.

James arrives in his RV-6 that he built 10 years ago.

Still from the video above.

Phone camera pic from James.

Eye Candy

I've been collating other people's photos of G-FUUN and these are some of the best I've found. Enjoy.

Taxiing in at Oshkosh after 'displaying'.

Taking off to fly one of two sequences in the contest in April.

Departing Sywell at the LAA Rally.

Taxiing to the 21 hold at Old Warden.

Landing at Peterborough Conington after flying a Sport class aerobatic sequence at the Nationals.

Warming up before departing Sywell at this years LAA Rally. The paint job looks it's best in the bright sunshine.

Still from a video taken at Oshkosh last year. Phillip Steinbach gets airborne in his Gamebird GB1 while us homebuilts wait our turn to display on the disused central taxiway.

Watching Sean D. Tucker display while we are made to hold on the taxiway after displaying at Oshkosh last year. Best seat in the house!

Departing Old Warden in January of this year to practise some aeros.

Twister inspired SSDR

From France comes the EXIA.

You can't help but look at it and see a resemblance to the Twister.

Although this is a very light weight machine, designed to take advantage of the Deregulated categories in Europe. This is, 120kg empty weight in Germany and 300kg MAUW in the UK.

Aerobatics FUUN

After winning the Club grade earlier this year I decided to make the move up to Sports grade. Although that didn't mean I had practised anything since April before entering this latest comp.

I hadn't even looked at the Known sequence until 2 weeks before this comp but still decided to enter anyway and treat it as a learning/training exercise.

So an intense 2 weeks of practise followed with me trying to fly every day (British weather permitting). First off learning the manoeuvres that were new to me and then trying to put everything together in the sequence and practise it with different weather/wind conditions. After that I focussed on practising UnKnown sequences - something I'd never done before.

At the comp I had the misfortune to pick 2nd out of the hat for the flying order so I wasn't able to learn anything each time from watching the other competitors before me.

The first sequence was a low overall score for me, I got massively off heading on the first figure and then hard zeroed the second and third figures as a result of that. Despite flying the rest of the sequence quite well it was impossible to recover from those early errors. A small mistake costs you dearly in Aerobatics.

Staying with my earlier theme, in the two UnKnown sequences, I managed to hard zero the highest scoring figures again! This hurt my score a lot but I still managed to finish in 6th (from 13) and 7th respectively so that made me feel not so bad at all. I had expected to be in the bottom 5 for the whole comp and to have two flights finishing in the middle of the pack was better than I expected.

Where the Twister is most lacking is in the Immelman where it loses lots of energy so the roll off the top always looks a bit 'soft'. I have tried to enter this figure faster and pull harder at the beginning and that seemed to help but an Extra 200 it is not.

I had a lot of fun and learnt a lot from the two days. I'll have a more serious attempt next year.

Sequence cards, videos and results of each sequence flown are below.

Known Sequence

https://www.youtube.com/watch?v=4ZgsVaPcC_4

1st UnKnown Sequence

https://www.youtube.com/watch?v=-Jtp32QjazY

2nd UnKnown Sequence

https://www.youtube.com/watch?v=puzjvkQy1q4

Overall Results

Twister with D-Motor

The owners of OE-CSI (formally G-CDKJ) Bert and Wilfried, have sent me some pics of their D-Motor install so far.

When it is up and flying it will be interesting to hear of the performance figures and if there are any issues. I did consider the D-Motor when building mine but it does not offer inverted oil so I did not go with it.

Wilfried also contacted me to let me know that they had the same issue as me with elevator play, on the Port side only. This was at 200 hours.