On 4/26/2011 4:13 PM, Walt Connelly wrote:
I have seen a number of glider advertised and most tell you the total
time. Unlike a powered airplane which has a tach or a Hobbs meter,
gliders seldom have any built in way to determine the actually time on
the air frame. While people might try to inflate their personal flying
time, I would not be surprised if many of these gliders are low balling
their actual air frame time which I presume has a lifetime limit in one
way or another. Is there any reasonably foolproof/accurate way to
determine the true time on an airframe? I cant think of one.

Walt

A couple of thoughts...

- My understanding of 'German glass' (the glider world 'certification
pioneers') is that early (Glasflugel & Schleicher & probably others)
pre-carbon-ed airframes were LBA-overseen-tested to 18,000 hours, then
(originally) certified to 1/6 of that, or the 'magic' 3,000 hours you'll
sooner or later encounter in the glider world. As airframes/types reached
3,000 hours, additional certification depended upon them passing detailed
inspections with the results forwarded/blessed by the LBA in 3,000 hour
increments. I believe some airframes have now been certified up to 12,000
hours (Twin Grobs? LS-4's?). It'd be great if knowledgeable Europeans will see
fit to chime in here...

- 'Pure glass' gliders are necessarily 'overstrong' (i.e. designed to
stiffness, rather than strength criteria [the latter being typical of aluminum
and wood gliders and airplanes]), in order to demonstrate 'usefully high'
flutter-free useable airspeeds.

- I'm unaware of any evidence of fatigue-related aging issues in any
first-generation glass ships' composites. (The metal bits are a different
story, of course...)

Based on the above, my conclusion is potential owners of 1st-generation glass
gliders have little to fret about in ship-life terms, at least of the plastic
bits, regardless of whether one is purchasing from an apparent 'squirrel' or
from Diogenes' sought-after human.

Regards,
Bob W.