Aircraft with airframe life limits, mandatory by AD aerobatic hours tracking and so on would make me a bit nervous. The Bulldog and Zlins both have that issue IFAIK when operated as certified aircraft.
I am very far from an expert on Zlins but I think it’d certainly be worth understanding the background and details of e.g. this link Somebody has kept that Zlin 142 really beautifully regardless.
@Silvaire it works both ways. The Zlin has a spar indicator and should document the TIS aerobatics in the tech logs. So complete logs is a pre requisite.
The Zlin I flew had many years of aerobatics left in it, and I believe the type is well supported in Czech Republic, so an airframe inspection would be possible.
The Bulldog has a Fatigue Index with DH providing an annual time limit remaining.
I quite like it that these airframes are monitored.
Can an older be Zlin 142 without “strengthened wings” be updated at reasonable cost to remove the prohibition on further aerobatic flight (applying to all unmodified aircraft) that’s mentioned in the service bulletin link I posted? Has this been done on many of the relatively low value LOM powered Z-142s? Is there any other mitigation or nuance that knowledgeable Czech posters might be able to explain? Oddly enough you never see a mention of the issue in any advertisement, but it might have something to do with their low market value
The saga of ‘over managed’ types from state sponsored (military or communist) design and ownership regimes can definitely remove most of the value from an aircraft during any given period of ownership, or catch the unwary buyer. So I think its something to guard against, unless its going into e.g. FAA experimental exhibition like a lot of Bulldogs. The problem there, even in areas where it is possible, is that it precludes commercial use as per the OP.
For commercial use the Citabria is the one that presents lowest ownership risk even if they fly like the ‘Super Aeronca’ that they are, heavy controls and lots of muscle needed. On the other hand the student would likely need the upset training to prepare for a future incident in a similarly flying plane. Anyway, you can buy an O-320 powered Citabria for 50K, sell it later for 50K and not have to get a PhD in fatigue life assessment to own it or fly it safely.
The 242 I used to fly logged around 45 minutes of Aeros on a typical old style 4 hour UPRT course. It had the nitrogen spar indicator, and an independent G recorder which was downloaded during inspections. It was used on an MPL course so required side by side seating, and it had enough aerobatic time remaining for another circa 350 courses. I believe it could be sent home to Czech and get an overhaul airframe extension, and at an economic rate.
The 242 uses a Lycoming with an inverted system and can perform snap rolls, inverted spins and tail slides – typical manoeuvres covered in signing off UPRT aerobatic instructors.
The A-UPRT has much less need for aerobatic time logged: only incipient spins (old school required stabilised auto rotation spin recovery), no nose low inverted, no nose high inverted, no inverted turns, it also is only a three hour course. Whether any aerobatic airframe time needs to be logged on an A-UPRT where the G meter doesn’t exceed 2.5 G, is worth getting an engineer input.
I will check with our engineers on time in service and the parameters of the G recorder, but on the 142 expect the main issue is the LOM engine.
Should clarify the 600 hour airframe check is aerobatic time in service?
preliminary feedback is that the Zlin is somewhat belt and braces:
1. Life limit on spars is quite generous and the Czech factory offers to re life, basically fitting new wings, our example was owned for ten years and was around half life (may be 242L specific but it is the same airframe as the 142)
2. The belt and braces aspect, is that you monitor the aerobatic time in service in the tech log, and every 100 hours you send the G recorder output to Zlin in Czech and they come back with a new release to service with a new time remaining input
3. In addition the nitrogen capsule in the spar provides a further indication if there is a spar problem through a red warning light.
We were very happy with the type and it was bought quickly and is now back in the Czech Republic.
In addition the nitrogen capsule in the spar provides a further indication if there is a spar problem through a red warning light.
How does that work?
The pressurized nitrogen idea was IIRC introduced by Zlin after Neil Williams’ incident many years ago, and is practical. I think the rest of the maintenance approach described may have been practical (if expensive) under communism with the planes and manufacturer owned by government, but is now misaligned with the level of practicality needed by a worldwide customer base.