View Full Version : L-29 trainer jet questions

Beaver diver
24th May 2007, 19:37
I would love If anyone could enlighten my knowledge about this trainer jet and some general stuff about the frames, conservationetc...
This is some brief data on airplane:
It was standing out on the open in Estonia for 14 years, although everything still works, a/c has 4hrs SMOH since they 've been doing sporadical checks on her.
My question is:
1.How bad can a skin and frame get (corrosion),If the plane wasn't flying but just being static on the airport and Is that repearable?
4.2. Structure - Fatigue State

A manufacturer’s communication states that the airframe life is nominally 5000 hours provided that all airframe overhauls have been carried out.4 All such overhauls have been performed by factory agreed agencies for 194555 with the last one at 2010:10 hours in March 1984. An extension beyond 5000 hours is permissible on an on-condition basis. The maximum interval between overhauls is 1200 hours. This information is derived from the logbook front page for this aircraft, which is series 9.

The remaining airframe fatigue life at permit application is therefore:
5000 - 2715: 20 = 2284 hours: 40 minutes

Remaining airframe time before overhaul is therefore:
1200 - 705:10 = 494 hours: 50 minutes

I don't understand the part about the airframe overhaul? Can that be done and is it costly?
Also, the entire system on this plane is run by either electric system or Nitrogen, even brakes. Is that safer and more reliable than hydraulic system?
And finally, I saw some ex-Eastern european planes (ex-military) having to apply for Stage III approved thing?What is that exactly meaning?

Thanks for any input

25th May 2007, 18:43
Someone's made you an irresistible offer, eh... :)

The Aero L-29 Delfin is a Czechoslovak-designed and made advanced trainer (tandem ejection seating) used by all WarPac nations' airforces (except Poland which used an indigenous design, the Iskra) and some others. It was last manufactured over 35 years ago, being replaced by the entirely different L-39. It was reckoned to be a docile and pleasant jet trainer.

1. After 14 years in the reasonably wet and cold Estonian climate (that's mid-Norway and mid-Canada latitude!), I'd say even if the skin shows no serious damage (best examine around seams and fasteners on the underside -- after a jetwash or five!), the airframe has basically had it. If we aren't talking corrosion, we're talking likely structural deformation, infestation (including fuel system!) with mosses, funghi and other flora, bird and rodent damage to controls, electrics and fuel lines, perished rubber fuel tanks, congealed lubricants fit for asphalting your drive, fermented fuel, general whiffy decay and leaks galore.

Basically, then, it's held together by the paint. Except that the L-29 was almost never painted... :)

2. In view of 1 above, this is theoretical at best... You'll never get her flying!

The Aero factory, now in the Czech Republic, had a deal with Boeing or someone Western, and was marketing a warmed-up L-39 known as the L-59, plus a light ground attacker called the L-159. Not sure, but I have a feeling the whole thing sort-of imploded 4 or 5 years ago 'coz nobody bought the things despite some very gee-whizz Farnborough appearances...

I would think an L-29 factory overhaul in the Czech Rep. would cost an arm and a leg, if it can be done at all after 14 years as a museum candidate. Others in the former WarPac may do it for less (Romania, Bulgaria, Belarus, Ukraine, some ex-USSR nations), but the you-get-what-you-pay-for argument may apply. The type seems to have been withdrawn from use around the 2000 mark.

That "Stage III thing" wouldn't apply to an L-29. It's an airport noise measurement and is only relevant to airliners operating in Western Europe, North America, Japan, Australia and a small handful of other countries.

Pneumatics instead of hyd is fine. Grabby brakes! (Like other early jet trainers the L-29 has no nosewheel steering, so you lurch around by differential braking. Must be fun!) I think the Fokker F.27 and quite a few other small airliners have pneumatics. Dunno about the latest regional jets which appear ideal for them, too.

Might be worth a fiver as a museum exhibit, provided you have a washer woman to bring her up to hygiene standards...