Sunday, 18 January 2026

Engine rebuild after EFATO

After landing I noticed a lot of oil coming out of the exhaust pipe which had coated the lower fuselage and tailplane.

Off with the top cowling and a removal of a spark plug from each cylinder with my friend turning over the prop it was obvious that there was no compression on Cylinder 1. Which is the front most SB cylinder.

Next step was to remove the head from Cylinder 1 which immediately revealed the cause of the problem. The piston was cracked in half!

I next used a borescope and after removing the sump was able to look at the rear of that piston to see if any big chunks had come off - luckily none were visible - just a hairline crack across the back of the piston - same as the front. Also the piston webs that are behind the gudgeon pin were still intact which had kept everything together.

So thankfully no further damage was done to the engine. That broken piston was all that was damaged.

Piston cracked in half on Cylinder 1.

These pistons were originals from new which was 2013. With approx 650 hours on them. They are made in the USA for Chrysler car engines and are of a cast type. 

Since 2022 UL Power do not sell an engine with these pistons. Having upgraded to a forged type. 

I had thought I should upgrade my pistons some years ago and this failure now gave the perfect excuse to do so. 

Rather than just upgrade one cylinder I decided to treat this as a top end overhaul and bought new forged pistons and barrels for all 4 cylinders.

Upon further investigation I found a little corrosion in Cylinder 4 bore and some wear in the other cylinders so I'm glad I made this decision as it has future proofed the engine somewhat.

As well as the pistons and barrels there were quite a few small items that were needed as well as some specialist Loctite products and tools. All in it cost me £3k in parts and tools as I did the whole job myself labour was not a factor.

While I had the top end apart I took the opportunity to clean up the heads and also found some pitting on all of the exhaust valves and some of the inlet valves - no doubt caused by my forced usage of AvGas 100LL at various stages, although I do try to minimise the use of it as best I can, usually running on UL91.

So I ground all the valves too.

Pitting on the exhaust valves - removed by grinding them using paste.


Valve seating face looking much nicer after grinding.

Sadly UL Power would not offer any kind of discount on the parts - despite them using me as a sales tool in their marketing for the last 9 years.

Also disappointing was the arrival of the 'new' pistons which were all damaged in some way or another - most likely cause was a poor job of packing them in the box and maybe rough handling by couriers.

Another set was sent and some of these had damage too. After a 3rd delivery I was finally able to start putting my engine back together.

'New' forged piston - damaged in transit

Slowly but surely I reassembled my engine - using a step by step guide kindly supplied by UL Power agent Metal Seagulls. Although I did find an error in the document - ring placement was switched! I was able to confirm the error before proceeding thankfully.

Some specialist tools are required but it is a fairly straight forward job really.

Engine going back together with new barrels and upgraded forged pistons

If you are thinking of upgrading yourself and want to borrow the specialist tools then let me know - I'm happy to share them so long as they are returned.

Piston half (cut across the gudgeon webs with a hacksaw) showing the fracture across the entire top portion.

No clear cause for the failure was established. Obviously the cast type is inferior to a forged type and I since the incident I have had several other UL Power users tell me they have had exactly the same failure.

The fact that UL don't sell an engine with these old cast pistons anymore tells you all you need to know really.

In the higher compression 'i' versions of UL engines I would not want to fly behind one with cast pistons.

When everything was back together I did a couple of ground runs to prove everything was ok and nothing was leaking.

After my inspector signed off the work I set about flying off the 5 hours of run in time.

To date (Jan 2026 - 8 months later) and with approx 56 hours on it the engine seems to be behaving as it should. 


EFATO

EFATO - Engine Failure After Take Off.


Every pilots worst nightmare.


It happened to me just after take off on 2nd May 2025.


Takeoff was totally normal and everything as it should be. Just cleared the boundary fence at about 200 ft with plenty of airspeed (90 knots, I never climb out slow) when there was a vibration and reduction of power. 


I immediately lowered the nose and changed fuel tanks with no improvement. 
I then looked back to judge my height and position to the runway and saw a big plume of blue smoke behind me. 


I turned around and found I actually had too much energy so did another S turn while getting the flaps down. Finally a big side slip to get back onto the reciprocal runway. Wind was 3-5 knots so not a big factor in my downwind landing.


I made a mayday call (my first) as there was an aircraft taxiing out to take off so I didn’t want him blocking the runway.  


Took 2 beers to finally get to sleep at midnight then woke up at 4am and ran it through in my mind again. Did I do the right thing? What would I have done differently? Answer is nothing. Had the wind been stronger and it happened 5 seconds earlier then I would have landed straight ahead in a field. 


I didn’t panic or mishandle the controls at all. Constantly flying on the edge with my Aeros no doubt helped here as I spin it pretty much every time I fly. 


Be safe and enjoy your Twister.


Oil all over my tailplane after the EFATO.



WIAC - World Intermediate Aerobatic Championships 2025 Hungary

Many lessons learned, while having much ‘fuun’.

I’d long thought of entering an international competition but until 2025 had not bitten the bullet. But as I saw the World Intermediate Championships were going to be held in Hungary in September I decided to go for it. Life is short - if you have any aspirations at all of entering such a competition then I’d advise to go for it, you won’t regret it for a minute.


First things first - I entered as a Kiwi but live in the UK. Why not enter as part of Team GB? Well long story short is that I tried to do exactly that but was ‘mucked around’ by the selection committee to the point that it was June before I was told they had decided they were not sending anyone for Intermediate. The other option I had was to enter as a Kiwi, something I’m glad I did and was proud to represent NZ on the World stage. 


The ‘paperwork’ was fairly straightforward, nothing too demanding there. The cost to enter (are you sitting down?) was €3,500 Euros with approx a further €2,500 in expenses (getting there and back and extra accommodation for practise week, transport, food etc). Giving a total all in of approx €6K. 


Getting there, flying across Europe, 4 countries in 2 days, 8hrs each way. Luckily there was a High pressure that developed over most of Europe so I had good weather the whole way out. Leg 1 was straight across the Nth Sea to Midden Zeeland for customs then onto Paderborn in Germany for an overnight stop with the always-welcoming Matthias. 


The next day I set off for Vienna where I had a fuel stop and lunch with a friend who lives there. Then it was just a quick hop of 1 hr down to the final destination in Hungary. Heviz Balaton airport. An ex-Soviet military MIG fighter base with it’s massive 2.5km long runway. Complete with crumbling hardened aircraft shelters and many old accommodation blocks now all deserted. It’s now an International airport but has very few movements so we mostly had the run of the place once the comp had started with only the occasional interruption for an airliner or air ambulance flight.


An option was to arrive 5 days before the comp started and take advantage of the opportunity to have practise flights in the official box. I think you’d be crazy not to take advantage of this no matter how much practise you’d done beforehand as there is nothing more helpful than to fly in the actual box and get your sight lines sorted. 


Having never flown in a fully marked out box before my first impression was “damn this box is small!“. 


10 minute slots were allocated on a first come first booked basis. This was all done online and you could only book 1 slot at a time. As soon as you’d flown that slot then you could book another one on the following day. 


4 practise flights were available in all, as one day was weathered out. I chose to fly for the 3 different Judging positions that were to be used, gaining valuable knowledge and sight pictures for each. I then used the last practise to fly my FreeKnown - something I always do before a comp - as I don’t want my brain to be ‘scrambled’ by an UnKnown practise with the possibility of transposing a figure from that Unknown into my FreeKnown.


During practise week, in between flights, there was time a plenty so I took the opportunity to visit the two main judging positions (the Southern position being inaccessible). I’m so glad I did this as it was extremely valuable to see what the Judges would see. The East position was very close - illegally close as it turns out - by 20 metres. It should be a minimum of 150 metres from Centrebox but it was 130 metres so I’d have to position slightly further away than normal. The opposite was the case with the West judge position which was at the outer limit of 250m and was also set on a downslope which changed the view as it made the aircraft in the box appear to be lower than they actually were.


With 18 different nations entered from both Inters and Advanced it was to be a truly international affair. 


What were my competitors flying? The next-worst performing aircraft to mine had 3 times the power and 4 times the roll rate. I was really going to be up against it. Not a single Pitts in sight - let alone a Cap 10 (my Twister has an even lower performance than the Cap 10). Perhaps there should be a limit on what can be entered for Inters? Or handicapping? It works for Gliders so why not for Powered Aerobatics? It has sadly become an ‘arms race’. 


The Romanians were out in force with 8 pilots entered. They are a professional team - state sponsored, arriving with a fleet of six Extra 330’s, mechanics, a coach and if that wasn’t enough the Warmup pilot for Inters was also a Romanian, which I found a little unsporting. So considering the machinery I was up against, on paper I should finish dead last. Let’s see if I could improve on that...


In true Kiwi underdog fashion I would have to channel my inner Burt Munro (The Worlds Fastest Indian). As it turns out earlier in the season I also made an ‘Offering to the god of speed’ when I suffered an EFATO. The culprit was a Piston which had cracked clean in half. This put me out of the air for a good portion of the season missing a comp and training as a result while I rebuilt the engine. 


With 70 pilots entered and a potential 4 sequences for each that would mean 280 flights in 6 days. 2 of which were half days and 2 of which we lost to bad weather. By my calculations we would not all get to fly 4 sequences - so would there be a cut? As it turns out the organiser decided that rather than a cut we should all fly 3 sequences. 


The comp started on Saturday 13th with the 38 Advanced pilots of the concurrently run WAAC going first. It was going to be a long wait till Monday afternoon before I’d get to fly. In the meantime the organiser had started the process of figure selection for our first UnKnown. This now meant my brain was getting scrambled with new figures and sequence designs while it should only be thinking about my FreeKnown. Something I had not experienced before. In the bigger teams this is not an issue as all of this stress and work is taken up by the coach, leaving the pilots to rest and focus on their next flight.


As an independent you have to attend every briefing and do everything for yourself so this automatically puts you at a disadvantage to the bigger more well equipped teams.


Finally it was time to fly my first competition flight, the FreeKnown. So how did it go? Well it was hot, 28 degrees which is a real performance sapper (especially noticeable in an underpowered aircraft) we also had a significant off judge wind, so my positioning wasn’t the best. I felt I’d flown it as well as I could and managed to score 70%, not bad.


Tuesday was more Advanced flying and Wednesday we lost to bad weather. So my second flight, the first UnKnown, took place on Thursday. As I was mid pack in the flying order for the first flight I was moved around and was now at the very front of the flying order being “Pilot 3” for this flight. At the briefing I was given a surprise when it was announced that they would be using the Southern Judging position (for the first time) as they felt the wind would swing round to the West as the day went on. Well for us first up it was very much a Southery wind so very off judge for us early runners. 


Although the rules say a minimum of 30 mins must pass before the first flight after the briefing, it still felt very rushed having to redo all the sight lines in my head as well as prep the plane and get ready. I’d planned on the Judges being to the East as they were every other morning - especially with the wind being mostly from the South as it was that day. The flight itself felt like a disaster while I was flying it as I ran out of energy - got too low. Aerobatics is Type 2 fun - you hate yourself at the time but afterwards on reflection can feel not so bad about it :) I was dreading the scores but again I managed to score 70% so felt ok about it afterwards. Note to self - start higher!


Finally it came to the last day of the comp and my last flight, the second UnKnown. 


If there is one thing I could take away and improve from this whole experience it is that of sequence design - how important it is to have that skill set. I know I don’t have it and so my design for the final UnKnown made for very poor positioning. With my lowest score of just 65.7%. This hurt my overall average and led to me finishing the comp in 23rd place, from 32 entered. Still, I wasn’t last and I’d beaten 9 others in vastly superior machinery.


The main thing was I hadn’t got any Hard Zeros and I’d learnt so much along the way which is all you can expect from your first international.


As I said at the beginning if you have any aspirations of competing in an International then I highly recommend the experience. 


Videos of my 3 flights on these links:


Known: https://youtu.be/QuDbalcquuQ?si=DxO5x1FzbbCwUe1r     


1st UnKnown: https://youtu.be/s9znnoFprtM?si=2PciptLH3b8ffybs


2nd UnKnown: https://youtu.be/1lntnAxTQt0?si=cY6pPO-lZdvmMbPZ


Following the Rhine river eastbound after just entering German airspace.


A good view of the Box. Damn it’s small!


The ‘venue’ Heviz Balaton airport and Lake Balaton (Europes largest lake).


The opening ceremony. Each country had a local in traditional dress as their flag bearer.


A thoughtful touch in our hotel were these pilot ‘profiles’.


My Twister and some of my competition. The weather was like this for most of the time with only the odd day rained out.


Sequence design begins. I was lucky to be able to add a figure in as priority is given to the bigger teams first.



Beauty and the Beast. I had to fly against that Sukhoi!


Team tents with flags up


Welcome to the candy shop. 2 hangars like this packed full of aerobatic throughbreds (and my Twister).


Departing out of Vienna with the Danube River below

Enjoying some Pflaumenkuchen (plum cake) in Paderborn with Matthias and Ingo on my way home