Q: I have been looking for a possible STC to install a primer system on a O-320-A2D. Would you know of one?
JERRY BARNHILL, Longville, La.
A: Jerry, after checking a few things out, I discovered that almost all of the O-320 series engines were delivered from Lycoming with a factory installed primer system. However, the O-320-A2D is the only O-320-A series that didn’t have the factory installed primer system.
Please keep in mind that I’m speaking specifically of the O-320-A series Wide Deck Cylinder Flange configuration engines, where the engine serial number suffix is -27A.
If I had to guess why this specific model did not include a factory supplied primer system, it would be the airframe manufacturer didn’t want to pay the cost for the system.
I’d also guess that this particular engine was utilized in a high-wing airframe application and the airframe manufacturer thought the head pressure from the fuel tank would eliminate the need for a primer system. The carburetor also was equipped with an accelerator pump, so a pump of the throttle prior to cranking would aid with the starting process. Of course, caution must be used when doing this because excessive pumping could lead to an engine fire.
If you are really convinced you need a primer, I’d look into installing one using FAA Form 337 rather than an STC, which may cost you money to obtain.
I’d suggest you discuss this with your local FAA GADO/FSDO. I see no reason why this wouldn’t be an easy field approval, keeping in mind that I can’t guess how the FAA may respond. You can show the FAA that primer systems are common on most O-320-A and E series Wide Deck Cylinder Flange configuration engines as listed in the Lycoming Parts Catalog PC-203-1.