It took about a year from initial discussions with the ACO to a completed STC. Much of that was Covid related delays at the FAA.
The actual development of the STC was based on Factory data which is by far the easiest path to approved data for an STC. In this case almost all the parts used are factory parts from the later 180 hp aircraft.
The cost varies depending on which year and which model is being upgraded, in general the later the year/model involved the fewer parts are required. This STC gives the option of a factory Dynafocal motor mount which opens up more engine options.
7ECA aircraft will need a new motor mount and completely new exhaust, airbox and baffling. Also the fuel lines must be 3/8 inch to comply.
7GCBC and GCAA aircraft can reuse their motor mount and baffling with minor modifications and some of the exhaust and airbox parts.
The later two piece fiberglass cowls can be used with a minor inlet modification (7-1469-1 and -2). Earlier cowls (with two doors) would require more extensive modifications and unless an installer really likes sanding fiberglass we recommend either finding a later cowl or purchase the new 8GCBC style cowl which requires no modification.
We currently have prop pitches from 50" to 60" approved. Our demo 7GCBC is fitted with a 52" pitch and is towing a heavy Grob 103 two place glass glider in Georgia heat with no problem.
Our next revision to the STC will be prop options. We are looking at the new Sensinich ground adjustable, the MT electric constant speed and the Hartzell constant speed.
The upgrade adds about 18 pounds to the empty weight* and does not increase the gross weight or change any of the speeds. There is an associated 18# reduction in useful load and the CG moves forward approx 1/4". We have not noticed any change to the flight or landing characteristics.
For owners with existing wide deck O-320-A2B engines (serial numbers ending in A) those engines can be changed to an O-360-C4P for Conical installations. The dynafocal options are O-360-A4M, A3A, A4A, A4N. If the hydraulic constant speed props are added, then the A1A,A1D and others will be included.
Back to the original questions, Owners can figure 8-12K for the parts to convert a later model aircraft, (some new parts, some recycled) a bit more with a new cowl and all new parts.
The engine cost is the biggest variable. Currently about 28-32k is the range to rebuild a wide deck A2B into a C4P. Those costs seem to be going up daily as parts price increases hit.
Cheers, Kent
*calculated with change to lightweight starter and alternator with upgrade.
