Thursday, September 09, 2010

The Blanik Dilemma

In June, there was a fatal accident in Austria involving a Blanik L13 glider which lost a wing. The investigation is not yet complete, but the manufacturer / type certificate holder, known as LET, issued a mandatory bulletin restricting aerobatics and requiring an inspection (for cracks) and requiring that the results and the glider's usage history be sent back to LET for evaluation. Later, the FAA issued several versions of the same bulletin, requiring a more stringent inspection. LET was to evaluate each glider's usage history and rule as to whether the glider could continue in service.

The latest FAA version has taken back the decision process from LET, but it essentially grounded every L13 until it passes an even more detailed US-based inspection. But the inspection has not yet been defined, so the entire fleet is in limbo until it is.

Our club owns two L13's (built in 1973) which we use for primary instruction. We performed the original inspections and found no cracks. We examined the aircraft logbooks and gathered the required information about number of flights, number of hours, ratio of solo vs. dual flights, ratio of aerotow vs. ground launches, number of aerobatic flights, damage and repair history etc. Since I'm the secretary my club and I retain the older logbooks, I took on the task of compiling the usage information. It was really interesting to look at the history of these gliders I have been flying: who owned them, what they accomplished in them, how many hours the pilots accumulated, the various minor and major damages, when they gliders changed hands (or wings!), how long they sat idle... each one has a story to tell. I think I'll write an article for our club newsletter with some of the more interesting facts about each one. I learned a bit about the Airworthiness Directive, repair, and documentation processes as well.

The glider community (at least the segment of it that does flight instruction) is in a spin at the moment. There are about 200 L13's in use in the U.S. I'm guessing that they are second only to the Schweizer 2-33 in popularity as a training glider, and I'm sure that some commercial operators use L13's for tourist rides as well. So a large part of the U.S. training fleet (in clubs and commercial ops) is grounded. Rumor has it that the larger commercial operators are working with the FAA and SSA to develop the new inspection and approval process. No one knows how long this will take, how much the new inspection procedure will cost, or who will do the evaluation.

Rumor has it that someone in Europe is looking at acquiring "new" never-used L13's that have been in storage in Russia, and selling them after appropriate refurbishing and updating; since the concern is fatigue and not age, theoretically these would be "safer".

So here's the dilemma: Does one failure justify permanently grounding an entire model of aircraft? Blaniks are not failing at in flight frequently. Was the accident aircraft an extreme case, i.e. used for extensive aerobatics? Was their hidden damage not caused by fatigue? We just don't know. Clubs like ours that rely on L13's have had to cancel training, and will lose members to other clubs/operations that fly other ships. On the other hand, if L13's are reaching the end of their useful life, we as operators need to be responsible and not fly them if they are dangerous. Usage records are not perfect - many operators did not record the type of launch, the number of occupants, the number of aerobatic flights, etc., they just recorded hours and flights. So any evaluation based on usage pattern will be quite subjective, and the evaluators will probably want to be very conservative. And developing a definitive inspection/testing procedure will be expensive.

For a more detailed history of these events, visit


Dafydd Llewellyn said...

You may be interested to know that an Australian STC (STC 96-1) was issued in 1979 by the Australian Dept of Transport, for a modification to increase the safe life for the L-13 from 3750/4000 hours to 11250/12000 hours. These lives apply only to aircraft whose aerobatic usage does not exceed 2% of TTIS. Negotiations are under way to make this modification available in Europe.

Motorcycle Parts said...

It is said that large traders who work for the FAA and the SSA to develop new inspection and approval process.

smith said...

Hi Roger - thought you might be interested in this. The other day at my Club I came across an old Blanik add from a gliding magazine. Whoever had found it had pulled it out of the magazine, so I took a photo of it.

You can download it here: