On Thursday, January 28, 2016 at 7:56:01 PM UTC-8, K m wrote:
Group,
My club is looking to convert a Twin Astir brake system to a Hydraulic Disk from a Mechanical Drum. Our serial number does not fall within the serial number range of the Kit that is offered by Lindner. We have the Lindner kit and will be going with a 337. My question is does anyone know of a 337 on an Astir brake mod?


We did a conversion on a Twin Astir at Cal City, ~1996. It was a side folding gear.... I think. The glider had earlier been owned by Bob Harris, and he used it for wave learning before taking the single Grob to the record climb. The Astir was operated by Douglas Soaring Club, when it had the conversion. We used a Cleveland wheel and disc. With a standard (4 or 6-ply) main wheel and heavy payload, anything other than a greaser landing resulted in too much sidewall flexion, which broke out the disc, and amazingly didn't grab on the calipers and create havoc.
The solution was to use a ten-ply sidewall tire, for very little flexion and higher psi in the tire. This then made for kangaroo results, if you plopped on with any vertical energy. The glider was sold to an operator in SE Colorado, and he was warned very directly about it's landing handling.

N173SS was then totalled within about six months time, by a commercial pilot who failed to latch the canopy, ballooned, released and crashed adjacent to the runway, NTSB Identification: DEN99LA028.

I don't know if you can get the FAA file on N173SS for a glider that is deregistered. We had a local DAR create the data for the 337 that was issued. I just thought you should know some of the drawbacks we experienced in the process. The drum brake was always a poor decelerator, but the disc offered a whole different potential for problems (nose overs and belly rubs, PIOs, wrong fluid installation, etc.).
No difference in payload other than the reduction by the added gear weight. Every pound counts in the older multi-repaired airframes. Good luck with yours and hope this info helps.

Cindy B