Air Plains Services STC SA4428SW, which replaces the standard engine with a 180 h.p. Lycoming O-360 A4A or similar and STC SA2196CE which increases the gross weight to 2,550 lbs. have both received CAA approval in the Public Transport category, on an Airworthiness Approval Note issued in the name of F. and H. ( Aircraft ).

The modifications, which can be carried out on Continental or Lycoming engines 172's are most economically carries out on the 172M which shares the same crankcase as the O-360, thus avoiding the need for any changes to be made to the engine cowlings. 

Air Plains provide a very comprehensive kit, including new baffling, Scat hosing, lifed  hoses etc., whilst the kit also includes a factory new propeller as the bigger engine requires a 76x58" propeller to replace the original 75x53".

The cost of conversion varies according to the model of 172 being converted and the source of the engine being fitted but G-BZBF was converted for about £ 10,000 because we purchased a part life Lycoming O-360A3A and sold the half life engine and the prop that were originally fitted.