Seagull Aircraft Sierra
 
Seagull-Sierra
 
The Seagull Sierra, designed in 1980 by Tom Peghiny, was Seagull's only double-surface glider. It was never offered for sale, as Seagull went defunct before the glider was HGMA certified. A few prototypes were flying in 1980; these were reported to have good performance but poor handling characteristics.