The -4 731 engine installed by aero was a one off that shares very few parts with the -4 you find on the business jets here.

Aero did I think 3 or 4 one had a catastrophic end (the engine) and I’m not sure what happened to the other two. One flys in a US based jet but again it’s a one off so there are no repair parts.

The -3 that you see code one and others using today makes
The same thrust as a AI25-TL, the performance improvement comes from removing weight from the tail (aft CG) then also removing counter weights in the nose. Light jets perform better.

The guys who made the various conversion kits for the 731s I don’t believe hold aerospace engineering degrees. Not saying they haven’t consulted with an engineering firm but I believe there is a reason you’re not seeing military contractors flying 731 powered jets. Not to mention the lack of inverted oil, and the -3 version that’s used in the business jets is not engineered for use in this environment. It feels a bit like car guys who make a bigger engine work on a car not designed for that engine with the -4 off a business jet.

Further there are some SBs on the 731s that Honeywell calls them un-airworthy if they don’t run every 30 days. Most of the engines you’re seeing on L-39s don’t come from perfectly airworthy airframes. Most are one engine timed out or the jet is being scrapped for whatever reason.

Personally I feel comfortable flying a factory designed engine that is not in short supply and can still be ordered today with a factory overhaul and warranty.

In fact they are planning on using them for drones.
https://www.overtdefense.com/2021/11/12 ... -for-mius/

No doubt the 731 is a great business jet engine, just unsure on how well engineered bolting it to a L39 really is.

More than once I have purchased an airplane (or most recently a boat) that is too much for me at that moment. But I find outstanding, highly experienced instructors/mentors and follow their guidance religiously. And I work with them until they say I’m ready for x,y,z operating limits. Enjoy the plane without them within those limits, and simultaneously continue to work with them for higher levels of performance.

That model works for me. Learning in general is one of my strengths. And with a good instructor onboard I’m not afraid to try new things. As an instructor myself, I understand that I must not try things so quickly that they can’t intervene and fix the situation if/when I eff-up.

My wife and I bought a big sailboat this year and we’re trying that model there, too. We both sailed previously. But the beast we bought is a new league of complexity and capability. So we have found some superb mentors/instructors. Work with them until they say we’re ready to coastal sailing without them. And take longer passages with them until we build the experience and demonstrate proficiency in the required skills to conduct oceanic passages.

Bring this back to the L-39, I think most pilots who can operate a pressurized single or twin OR who has other quality flight experience can learn to fly the L-39. Acro? Tail dragger? ‘Warbird? Turbine? The only reason I put that pressurized experience or “quality” flight time in there is to show a history of learning more complex aviation skills. That’s really the key. Can you learn new complex skills? Do you have a history of it? Do you like it? If so, the -39 is doable to most with 1,000 hours total time. My partner in the plane had 1200 hours when we bought it. But, 400 was tailwheel, plenty of acro (he had a Great Lakes and Marchetti 260), and he loves to learn new things. In any field.

Maybe it doesn’t work for others, but it does for me.

Z.

The contractor (Draken) flying the 159s use the F124 motor, which is a derivative of the 731. It’s been a long time since I’ve been out to Czech, but the 39NG program was getting the FJ44-4M. I can’t remember the debate about the the 731 vs FJ44.

https://www.anews.com.tr/world/2022/11/ ... -built/amp

I think the engine factory is destroyed

yeah. that is going to be a problem...

They are still operational, actually shipped a few units last month. Production is just spread out not all production units were impacted.

That said having a spare motor is a good idea.

Question for L-39 owners-

anyone using the oxygen system/masks for transit flights? I need a reference for connecting US O2 systems to the Russian regulators.

From my prior life, I have a Navy MBU12 O2 mask (dilutor demand), and would like to use it with the stock regulators.

any sources or reference material is appreciated.

When my hangar partner had a L-39 I helped him install an oxygen regulator and mask hookup from a T-28 solving that issue.

It’s a very simple modification. You remove one part from the front cockpit and modify the output lines to support the US style mask. I think it took all of an hour when we converted my jet.

It’s a very simple modification. You remove one part from the front cockpit and modify the output lines to support the US style mask. I think it took all of an hour when we converted my jet.

A little rime ice on the leading edges. Front seater gets spatial disorientation from the Russian-style attitude indicator and has to give up the controls. Fun stuff.

[youtube]https://youtu.be/93XmEcoIe-8[/youtube]

Welcome to YouTube, drama for views. IMC for all of 5 minutes really shows you how much different Russian attitude indicators are. Granted that was my first full IMC experience in the jet, I would never dream of flying IMC single pilot with that avionics configuration. The only reason the ice was a non issue was it was a known thin layer, again more drama in the editing then reality.

Mat, that Russian AI can't be any more confusing than the Sperry F-3!

The big difference on the Russian VS American AI that takes getting use to is the airplane moves for the bank angle, and the background moves for pitch. It’s a bit of getting use to on the eye.

It seems there's more than one type of "Russian" AI.

There's this one in a L-39 (top photo) that has a moving "airplane" for bank, but at least the sky is on top and the ground on the bottom. This one frankly seems fairly easy to adjust to compared to the other type as shown in a Nanchang CJ-6 (bottom photo).

The Nanchang AI appears to function in the same way as a Sperry F-3 (ground on top, sky on bottom) but at least (unlike the F-3) the sky is blue and the ground is brown.