Little big things

Yeah, time flies (but so do we...)
Lots of work had been acomplished on the Aero project.
Biggies are that the canopy plexiglass is fitted to the frame, fuel tanks are now servicable after cleaning, pressure test and repainting.
There is a lot of paint stripping, fitting and priming going on on various metal parts and other stuff as well.

Fuel tanks and vent lines all ready to go.

Nicely primed! More or less metal parts from the center section, like fairings, D-boxes, flaps and some are from the windscreen also.

But here are two images just as a preview and I will try to put together a more concise post in the next ten days or so. Enjoy the summer!

Canopy frame

I actually managed to keep my promise to post more often. The following was done in the past week. We prepared the canopy frame. This involved restoring it, making some replacment parts and painting. It is going off to have the plexiglass fitted. Don't have enough courage to do that in our shop.
Here is the begining:

About three layers of paint had to go off first.

Same frame as above but with the plexiglass and metal fairing removed.

Here it is in primer. The original plating held up well so corrosion was not an issue. But we had to prime the inside for the new paint to adhere better.

And I always was a sucker for details:

Before and after shot:

The latch mechanism before.

and after.

I will come back soon hopefully with more nice images.

Have fun till then!

Bolts

Whoa. Time flies. Not our Aero, though.
Let me just say that in the first 50 days of the year, we reached our yearly plan for composite production. Enough said.
Somethings were still done on the Aero. This time I'd like to present the research work done on bolts. There were several bolts that were either damaged or corroded to such extent that they need to be replaced.
One thing that we constantly keep in mind regarding this aircraft is that it is heavy. H E A V Y.
Therefore all the primary structure must really be top notch and we have to be confident in it.
So we ran a tensile test on some samples of metal.

The image above shows three samples. One is a sample turned from an original bolt, the other is a material that I thought was suitable for new bolts, and the other is simply a 8.8 normal hardware bolt.
The result of the test was not so hot.

As you can see the normal hardware bolt peaked at 640 N/sq.mm as it should. The strongest bolt was the original one at 1000 N/sq.mm and the CrMo that was my best bet before the test reached a little over 800 N/sq.mm. Back to the drawing board, but this time it is much easier, since we know what we have to replace.
Another two samples are prepared. One again from the original bolt and another from the a different CrMo steel. So it is time for another test.

This kind of work is exacting and it does eat away at the time, but it has to be done. Imagine putting a normal hardware bolt replacing the high tensile old one and crossing your finger...
I won't promise to keep the blog more up to date, but I will certainly try to.
Have fun, enjoy the spring!

Windshield

Hey everybody,
First post this month - just in time actually. The reason is very simple. NO WORK had been done on the Aero. November and December were fully booked and no resources were left to work on this aircraft. A pricing policy change and some new help will get the project rolling a bit more rapidly in the first quarter of 2012.
Still, some stuff was outsourced - like the windshield.
The story goes that the bubble windshield was the first blown windshield produced locally. Was not all that great to start with. The unfortunate S5-MBB had a crystal clear windshield, but was not optically correct due to waviness in the plexiglass. When flying it, one had to constatlly weave around with the viewpoint to get the ''correct'' sight. The other problem was that our windscreen was full of microcrakcs as evident in this image. These are internal cracks that cannot be polished out, so the whole windscreen was unservicable.

Very, very big image, to show the cracks clearly

So this is the correct solution for the problem:

Looks nice, doesn't it? We will see how it is installed.

Thanks for stoping by. I wish all of you to stay healty in 2012! Happy new year.

A short introduction to Aero-3

Our workshop has a new roof. Now we have to tidy up a milion small details and this will take some time. So nothing new to report on the Aero, but I was thinking that this might be a good time to explain what exactly is an Utva Aero-3.

Utva Aero-3 in flight.

Utva Aero-3 is a primary trainer that was built in 1959 in Yugoslavia. As you might had noticed in the previous posts it is made of wood, but is powered by a Lycoming O-435 engine, which was pretty standard for that age.

This trainer was built primarily to serve in the Yugoslav Air Force Academy during the sixties, when the country was receiving a huge number of aircraft through the MDAP scheme. This needed a steady influx of novice pilots. Therefore the Academy devised a three year training programme. First years was basic training on the Aero-3, second year advanced flying on Soko 522 (picture is an older post), and third year operational training.

Most Aero-3 trainers wore trainer yellow paint scheme, but these two are camuflaged.

Now as I've written in a lot of previous posts, the aircraft is just a vehicle for people to communicate. Now, let us talk more about the people that flew Aeros.
This picture is from the personal archive of Mirko Anžel of Trbovlje. It was taken in 1965 during his training in the academy. Since he was the number one of his class, he opted for fast jets and therefore flew 10 hours of TV-2 (version of Lockheed T-33) and then solo on the F-86 Sabre.

Mirko Anžel before flying the TV-2.

Mirko always recals that this was amazing. His generation had almost no time on Soko 522, since they had a fleet problem of cracked propellors at that time. Therefore they flew about 120 hours on the Aero-3, a few hours on the Soko 522, 10 hours on the TV-2 and then soloed the Sabre.

Mirko Anžel, left. Notice that the Sabre is one formerly used by the 204.lap aerobatic team.

This image shows him in front on the F-86, with his instructor in the center. Mirko then went on to MiG-21s and graduated from EPNER at Istres, France as a full course graduate. Even now, he recalls that his greatest profesional achievment is the Sabre solo. Everything that came later, like the MiG-21, Mirage III or the Caravelle, was not that much of a jump then it was from the Aero-3 to the cockpit of the Sabre. Mirko is a constant source of knowledge and advice. If we were not restoring the Aero, we would not had met him.

Vojko Gantar in front of Lockheed TV-2, right.

The image above shows a very young Vojko Gantar from Idrija. Vojko was one of the top Yugoslavian Air Force fighter pilots. At age 23 he was assistant squadron CO on Sabre D fighters and then spent 22 years flying the supersonic MiG-21. He went through the same process Aero-3-Soko 522-TV-2-Sabre during his academy years. His last years before the breakup of Yugoslavia was in command of the MiG-21 training squadron at Pula, now Croatia. Again Vojko is one of the very best teachers and menthors you can imagine.
Perfectionist by nature, open minded and extremly willing to help out, I think he might be one of the most valuable forgoten pilots that we have right now.

So again, the aircraft does not matter. Sure, it is a nice aircraft that can teach tailwheel, basic aerobatics and actually has some post-stall flying characteristics (which is totally untrue for aircraft built under JAR/FAR-23, which just do not stall...), and with a supported Lycoming engine to boot, but it is the people that matter. What matters is that Vojko totally secluded from flying, worked as a mountain sheppard, but now he is back again lecturing on hand flown IFR and supersonic flying.

This is why we restore aircraft.

Till next time. Have fun, go beyond your ego, seek advice, talk to people, respect your elders.

Fairings fitted

This week we spent some time fitting the fairings to the center section. The fuselage had original holes, but the center section needed new ones drilled and nutplates installed. This is the end result.

The fairings are actually the whole D-box (leading edge), walking surface and wing-to-fuselage fairing.

Up close.

And the other side, but looking from the rear.

This is probably the last post for a while, since we have a bit of a backlog on orders and in between we are changing the roof of the workshop. Which is a bit stressfull in november with a shop full of vintage aircraft and engines.
Next up is dry ice blasting of the fairings and some other metal parts and fabric covering of the center secion. Have fun!

New trim

I forgot that we also built a new elevator trim surface. It started out as usual - the original part looked worn, but acceptable.

Original trim surface after paint stipping.

So at this time, I made a template for locating the holes for the trim control cables. This template was then used after the new fabric was installed to mark out and cut the position, where the cables penetrate the fabric.

But then I blasted the part and the aluminum surface literary came apart as evident below.

Notice the small holes bored open by the blasting media? I didn't even bother to continue blasting, since this part is gone.

Therefore a template was made, new alluminum cover was hammered over and much to our surprise the trimer even had a wooden core. Janez fabricated a new one.

New (bottom two) versus old. Notice how the original core shrinked in one direction due to moisture.

Not being that skilled in working with aluminum those curved, wedge edges were not that easy to get right.

Then everything was fitted to the elevator to verify aligment. Notice how the elevator is already covered.

Then some rivets and we are done! Notice the fixed trim tab for the rudder above.

If you like this aluminium thingy and would need an inspiration, please check out the story of Arnold Ebneter and his E-1. This link should get you started.