Why aren't CJ's and Yak 52's more popular?

[skymstr02]

Also, as the CJ's are still "Experimental" category aircraft, I wouldn't worry about having an A&P work on it if you got one if you have any mechanical ability. Saves the cost and the problem of finding one that will work on it.

Where is this stated? Common misconception. Just because its registered in the experimental category, it still must be released for service by a certificated mechanic. You don't need an IA to perform an annual inspection, because it doesn't require an annual inspection. It receives a condition inspection. All of this is spelled on the the ops specs that were issued when the airworthiness certificate was issued. It even tells how the wording must be in the log books.

[Wheels up]

Just because its registered in the experimental category, it still must be released for service by a certificated mechanic.

I concur...
It is no different from Amateur Built Experimental, other than an amateur built has provisions for the manufacturer (the primary builder) to apply for a Repairman Certificate.
If operated under Pt 91 then 91.407 still applies and it refers to the persons qualified in 43.7.
The misconception usually stems from the applicability of Pt43 (43.1) where it is stated that Pt43 does not apply to Experimentals. This is true but IF Pt43 is ref'd from another applicable Pt of the FARs then that specific referenced regulation is applicable.

[CAPFlyer]

What I'm saying is that most of your work on a CJ can be done by yourself and not require an A&P to do all of it, which can be expensive because of the differences in how they're built and maintained.

Gary - I may be mistaken on this, but I'm pretty sure that the CJ-6As I've been around used Nitrogen just like the L-29 and L-39 for the pneumatic and had electric starters.

[retroaviation]

Gary - I may be mistaken on this, but I'm pretty sure that the CJ-6As I've been around used Nitrogen just like the L-29 and L-39 for the pneumatic and had electric starters.

Certainly possible, but the CJ's I flew and the Yak 52 that I have about 100 hours in, along with a low level aerobatic waiver in, all had pnuematic starters (the air going straight into the top of the cylinder, much like some fuel injection systems). And trust me, in those cases, nitrogen doesn't work well.

Gary

[DB2]

AFAIK, all Yaks and CJs have air (not nitrogen) systems...in fact the compressor will dump air "overboard" when replenishing the system. The engine start is accomplished by using air to move the pistons.

Some of the later "westernized" Yak-52W/TW aircraft have electric start (and hydraulic brakes). The obvious problem with air start is that, once you're out of air, you are stuck! Many Yak drivers carry around a small emergency air bottle.

The L-39s have an internal APU (the Sapphire) that provides air to start the engine. They have a nitrogen accumulator system to provide emergency hydraulic pressure.

[CAPFlyer]

The nitrogen in the L-29/39 provides for the sealing of the canopy and maintaining pressure on the normal hydraulic accumulator as well as the emergency backup for the hydraulics (blow down the gear, etc).

I was surprised at how much nitrogen one can use in a single flight. I think that the guys were usually refilling the nitrogen every 3-4 flights.

What I'm saying is that most of your work on a CJ can be done by yourself and not require an A&P to do all of it, which can be expensive because of the differences in how they're built and maintained.

Gary - I may be mistaken on this, but I'm pretty sure that the CJ-6As I've been around used Nitrogen just like the L-29 and L-39 for the pneumatic and had electric starters.

The CJ's are easy to work on (I was working on ours last night) and even the English maintenance manual is quite good - kind of a combination E&M manual and IPC. Some of the components you can see the lineage of - the ADF's as fitted by the Chinese are a direct copy of the American Bendix unit, for instance, and the four channel push-button VHF sure looks like a US made WWII era unit. They are a well made and well designed airplane, easy to fix and easy to fly (though a b-stard to taxi until you learn how - and I'm still working on that!) The only gripe I have with them is, as surplused by the PLAAF, they have absolutely terrible fabric with no silver dope, and workmanship that makes you think they had used a beaver instead of pinking shears to cut out the fabric! But underneath the lousy fabric the metal work is excellent and all the metal is anodized. The more I work on ours the more I like it, but, that said, even here in Canada where they operate under the Limited category, the aircraft still has to be released by a licenced engineer.

There is no nitrogen - it's entirely regular, old compressed air (complete with water drains) and the air compressor runs off the accesory drive of the engine. If you run out of air you can hand swing it fairly easily but it takes two - one guy to swing it and one guy to hold down the starter button to energize the booster coil. The first time we did it (I left the air on overnight) it took us about half an hour to fire it up and we had a good sized crowd assembled by the time we were done. The second time she lit off on the second swing.

Neat airplane. Nice to fly, easy to work on, and an interesting look behind the bamboo curtain. By the way, anybody have a Chinese grease gun they want to sell?

[John Cotter]

The nitrogen in the L-29/39 provides for the sealing of the canopy and maintaining pressure on the normal hydraulic accumulator as well as the emergency backup for the hydraulics (blow down the gear, etc).

I was surprised at how much nitrogen one can use in a single flight. I think that the guys were usually refilling the nitrogen every 3-4 flights.

The L39 does not use nitrogen to "blow" down the gear. It is from a hydraulic accumulator.

[CAPFlyer]

Sorry John, I used of a common term for the emergency system no matter what it actually does.

Personally, I've always heard many backup gear extension systems being called "blow down" since it usually involves some sort of system that is "one shot" and more often than not does so in a more spectacular fashion than the normal system. For example, the "blow down" system on the Convair 240/340/440 is a gravity system, but when the gear comes down without the hydraulic fluid being regulated, it's quite fast and very violent (typically causes the plane to walk a few inches on the jacks).

[John Cotter]

Sorry John, I used of a common term for the emergency system no matter what it actually does.

Personally, I've always heard many backup gear extension systems being called "blow down" since it usually involves some sort of system that is "one shot" and more often than not does so in a more spectacular fashion than the normal system. For example, the "blow down" system on the Convair 240/340/440 is a gravity system, but when the gear comes down without the hydraulic fluid being regulated, it's quite fast and very violent (typically causes the plane to walk a few inches on the jacks).

I didn't mean to come off glib. And I understand where you are coming from on the emergency gear extension systems. The L-39 uses an accumulator that can extend the gear, the flaps (full only) and the ram air turbine (backup generator).

[Matt Gunsch]

a CJ does not use nitrogen in it's air system. Have you ever tried lighting a match in a nitrogen enviroment ? does not work too well, the same goes for starting a CJ, the nitrogen is filling the cylinders, and there is now a nitrogen/fuel mixture in the cyclinders, one kind of defeats the other.

I have used a scuba bottle as a APU on a Yak 52 I took care of.

[Roger Cain]

As the subject runs away, very popular here in the U.S., here are a couple pages I posted from past FAST meets in CA

http://www.sfahistory.org/allredstar.htm

http://www.sfahistory.org/allredstar3.htm

http://www.sfahistory.org/allredstar4.htm

Please excuse my poor scanning capabilities at that time of that stuff they called film.

[John Dupre]

a CJ does not use nitrogen in it's air system. Have you ever tried lighting a match in a nitrogen enviroment ? does not work too well, the same goes for starting a CJ, the nitrogen is filling the cylinders, and there is now a nitrogen/fuel mixture in the cyclinders, one kind of defeats the other.

I have used a scuba bottle as a APU on a Yak 52 I took care of.

Nitrogen is an inert gas. It has no explosive or incendiary properties. It is commonly used in oleo struts with hydraulic fluid. Maybe you are thinking of Hydrogen?

[Matt Gunsch]

a CJ does not use nitrogen in it's air system. Have you ever tried lighting a match in a nitrogen enviroment ? does not work too well, the same goes for starting a CJ, the nitrogen is filling the cylinders, and there is now a nitrogen/fuel mixture in the cyclinders, one kind of defeats the other.

I have used a scuba bottle as a APU on a Yak 52 I took care of.

Nitrogen is an inert gas. It has no explosive or incendiary properties. It is commonly used in oleo struts with hydraulic fluid. Maybe you are thinking of Hydrogen?

IF you read what I posted, it is obvious that nitrogen is a inert gas, since I said one defeats the other. I have had owners recharge their air system with nitrogen and then wonder why the plane would not start.

I have been working on and around CJs and Yaks since 92.

On the need for a A&P to work on one, as a owner, you are still limited to what a owner can do by part 43, appendix A. Also, since it is experimental exhibition does not mean you can modify without doing the paperwork. If you install a new prop that is of a different type than what the aircraft was certified with, you are now back in testing, and must fly thru your test time.