Type certificate E-256
Held today by Textron Lycoming Avco Corporation, earlier by Avco Corporation, Lycoming Division. It covers 4 models; about 2 aircraft on the U.S. register are built to it. Last revised April 22, 1959 (revision 6). 3 FAA orders name its designs, and 9 approved modifications build on it.
Models under this certificate 4
GSO-580-C, GSO-580, GSO-580-B, GSO-580-D
Engine series
The data sheet on the FAA's site: the approved engines and propellers, weights, speeds and limits for each model.
FAA orders on these designs 3 · newest first
2012-03-272012-03-07 · Carburetor · engine
2004-06-252004-10-14 · Crankshaft gear · engine
1969-01-1666-06-03 · Connecting Rod Assemblies · engine
Approved modifications 9 · companies holding the most
Source: FAA type certificate data sheets (Dynamic Regulatory System); register counts from the FAA register of October 5, 2026. Connections as data: /graph/certificate/E-256.json.