Warbird Information Exchange

Anybody with any YAK 12/PZL 101 experience? Thoughts on caring for the AI14P engine? Just found out about the aircraft and it looks like just what a growing L5 family needs.

_________________
REMEMBER THE SERGEANT PILOTS!

I will share what I learned about the PZL101/Yak-12 last year. I was going to buy one from Bill Austin aircraft sales last year but it crashed on delivery flight following engine failure.
It the Yak 12 was designed around 1945/46 and was in production until around 1969. It was flown by Russia, Poland, Romania and many other formerly communist countries. It's nato code name is Creek or moose depending on if its the yak-12 or PZL-101. There are lots of neat paint scheme possibilities. It possibly was used for Bed CHeck Charlie missions as a few were supplied to North Korea in the early 50's.
It has a 1750 pound payload with five seats and can get off an unimproved field in about 450 feet. It's range is in excess of 750 miles. It can be equipped with external drop tanks, one per wing. It has a cruise of 85 mph and max speed of 115 mph. It has a 50' wingspan, with a Clark Y airfoil, huge flaps, just like a Husky A-1, Taylorcraft L-2, BC-12D, and many other STOL aircraft.
Some models only have equipment for one pilot others are dual control. Some of these have fabric wings and others have fabric only.
THere are a couple of them flying with amphib floats and the airframe can accept up to the 400hp. version of the M-14P.
It has the pneumatic starter and brakes like the Yak-52 , and they are reliable. Most of the Yak-12's being imported have new fabric and plexiglass and you can get one for easily under $50,000. You can see one at www.billaustinaircraft-yacht.com
My guess is that it is probably a RUDDER aircraft and you have to lead with the rudder when making turns. Also, It looks (to me) like the Russians stole a Taylorcraft L-2, upsized it and put a big radial on it. YOu know the British company Auster filched a lot from the American designed L-2 when they designed the AOP. 3 STOL aircraft.
The engine is the same as the Wilga PZL 105 series and they are not that well liked by Wilga owners and that is the only minus I can see.
Best of Luck!

Seems like they have been coming in since the early 90's. I have talked to several importers and there is a good supply. What happened to the engine on yours? What kind of problems are they talking about on the engines? Have you heard of any engine changes to US made engines? It reminds me of a Beaver...

Thanks for the information!

_________________
REMEMBER THE SERGEANT PILOTS!

Hi,
I checked my reference book when I got home and have a few corrections. The prototype flew in late 1944, The Yak 11 is the "Moose" and the Yak 12 is the "Creek" . It has a wingspan of 41 feet.
The one that I had been talking to Bill Austin about crashed shortly after takeoff somewhere up east, maybe Connecticut. The pilot Robert Lankford set up a glide and picked a field. It failed to clear a stone wall and this resulted in substantial damage. It and two others were sold to a bush pilot in Canada. THis was a conversation I had with Mr. Lankford at a Fly-In last October. He said the prop was spinning freely and the (?) crankshaft spline(?) had sheared. Anyway there is probably a NTSB report out from last Sept. or August on the PZL 101. You may also want to look up the PZL Wilga 105.
I bought a piece of land last year, and my thought was that the Yak12 could be flown out of there with minimal site prep. You might be able to buy one for as little as $30k. A new 360hp. M-14P with all accessories and electric starter runs about $23,500. You can buy Wipline amphib floats or Montana amphibs for about $34,000. You could have a pretty neat five place warbird with good metal, new fabric, plexiglas, engine,prop and amphib floats, and paint for under$100,000. bucks airshow ready.
Paint schemes are wide open, including; Russian WWII, North Korean 1950's, North Vietnamese 1960, East European cold war, Cuban, CHinese, or paint it as a "replica" Beaver in Canadian, Australian, or U.S. markings, I was considering painting it as a Stinson L-1 Vigilant as they were built in Nashville, operated in the area and You aren't going to have a real one pull up next to you at an airshow!
Are you sold yet!

I'm sold already! 1700 useful load on 12 gallons an hour? Count me in any day. I do want to talk to the Wilga people about the AI14, about its serviceability/problems/etc. I can afford the 40-50K airplane, but I can't afford the airplane AND an engine change right off the bat...

_________________
REMEMBER THE SERGEANT PILOTS!

The engine handling is typical of any radial engine, with hydraulic lock being the main thing that can cause damage.

You can get intake drain kits, which help alleviate the problem on pre-flight pull throughs. The engine itself is robust and reliable.

There is a history of the Russian plugs failing, however. Again, this seems to come back to hydraulic locks - full or partial. It may seem that the cylinders have been cleared of oil following a lock-up, but the plugs can suffer damage and be weakened. They then sit there in the engine like a time bomb and can fail hours, weeks, months later.

I fly a Yak-52, and had a plug core blow just after Christmas. I was over water at the time and couldn't maintain height and ended up making a forced landing. We had a hydraulic lock which was cleared by an engineer a few months before. The accident report thought it possible the plug was damaged by it. Plugs have a life of 200 hours. This one had done 60 hours.

Recently another Yak based at the same field had a similar plug failure, but was high enough to make it back. He had suffered from hydraulic lock too a while back.

The two bottom cylinders 5 & 6 are most at risk. It seems that despite the cowling, exhaust gas gets ingested into the carburettor air intake immediately below and between the cylinders, which temporarily cuts the engine, which then picks up again and cuts in a self perpetuating cycle. It's not a full failure which is why it's easy to make some wrong decisions about how to deal with it.

The problem is that plug failures are not covered in the emergency checklists, so unless you know about what to expect, what is going on around you is very perplexing. I made the mistake of thinking it was fuel starvation or a carb problem (which it was but for a different reason) and used the primer. Thinking about it afterwards, you can use left or right mag to identify which plug has failed and then kill the cylinder by stopping the other plug from firing. It will fly OK on eight.

If a plug fails on Number 3 cylinder it will cook the CHT sensor, sending it into the red, again perplexing as the coolig gills at the front may have jammed shut as another potential cause.

Plug cores blowing out can also set fire to the ignition harness and fill the cockpit with smoke. I was lucky that this did not happen in my case. You get a bit of warning of this as apparently there is a rubbery sort of smell for a while before all hell breaks loose.

Western plugs can be substituted for the Russian ones. But I have no knowledge of what this involves or whether it cures the problem. My advice would be, if you have a hydraulic lock, change the bottom plugs. Of course, if its a partial lock, you may not even know it has happened.

I've seen the Yak-12 do some amazing short field stuff. Interesting aeroplane. Hope this doesn't put you off.

TJJ

I have a Nanchang CJ6 with the same engine license built in China. I have had very few problems with the engine and it is one of the smoothest radials I have flown. There are a few problems like cylinder base studs loosning up but otherwise very few maintanace problems. I think most problems with these engines come from not operating the engine correctly. A lot of the importers have not had any radial experience and really have no idea how to run them properly and it gets passed on to the buyer.

Hydraulic lock? Is this from not walking the prop before starting? And the plug failure- is it the plug or the plug insert failing? There are lots of little passages on spark plugs that could be "injection-lubed" with an oil lock, and the insert will take some of the force, but are we talking about a complete cure by doing a thorough hand prop before flying for prevention, or something else?

I find the "hangar lore" to be more pervasive, common, and accepted than the cool voice of trained, practicing, recent experience. I was told how bad the O435 was on the L5 before I bought it. I don't have enough experience to deny all of it, but a retired Lycoming engineer, who helped develop the O235/O290/ O435 series says it is all rubbish.

_________________
REMEMBER THE SERGEANT PILOTS!

Starting the engine cold without pulling through is just asking for trouble. In the winter when the cold makes the oil thicker you need to be more careful.

Part of the pre-flight is to pull the engine through unless the CHT is above 80 degrees C. You then check to see if any oil is dripping out of the exhaust and/or intake drain (if it is fitted), then maybe pull through some more until the oil stops dripping. We keep a couple of tin cans over the exhaust to stop oil getting on the parking pad. It's easy to check to see how much is in there. It does seem to vary.

Part of the shut-down procedure is to run the engine up at 65%-70% power for 30 seconds to purge any oil back up into the header tank. Obviously oil does migrate back down through the engine over time. Hence the pull through.

Pulling through isn't a complete cure. It will tell you if you have a full lock - then you stop and get some help - and it will help to minimise the risk of partial locks (especially if intake drains are fitted), but the damage could already have been done in that spilt second of pulling and meeting resistance.

Re: plug failure. In my case the core blew out completely with the plug casing left still screwed into the cylinder head. I have seen another example where the side of the plug casing burnt through.

I think there is a great deal of truth about a lack of in-depth knowledge of operational procedures or people blindly following a checklist without understanding the underlying reasons for actions. In the USSR, they would have had engineers to pull though and warm up the aircraft, and they probably would have checked the plugs if there was a sign of a lock.

I'm not an engineer, I just fly the aircraft. I've tried to accumulate as much information as I can about its operation, but there is still an awful lot I don't know. But that's what flying is all about - you never stop learning. It's just that sometimes learning can be expensive!

TJJ

A truly unique and cool aircraft! The people at VICTORIA AIR MAINTENANCE have one in their hangar they have been working on. Looks like a fun plane. http://www.vicair.net/
A friend of mine in Vancouver (Bill Jesse:author, photog, good guy, met at Breckenridge TX. annual airshows) turned me on to them. Yes, I miss Breckenridge! You need to look through the many aircraft of this type at Airliners.com.... Pretty cool planes. I'd almost trade my Citabria for one.... Heck, it's got a stick!

On the other subject of the plugs, My frind here in OK. has a Wilga 35 that it happened to on a glider Ferry flight. As it happened, everything was fine. the glider cut loose and was able to come back to point of origin and so did the Wilga. Like was mentioned, the smell and the sound change was most apparent with the miss-firing engine. The ole Wilga just chugged back to the field and landing was uneventfull though I think he was ready for a beer....or two! He has her down right now for annual and a few jugs. REALLY NEAT AIRPLANE! Esp as a camera platform with the R/H door off!

_________________
Civis Aerius Sum

I am a citizen of the Air