I am looking at a 421 that has an older DER approved repair to the engine mount beam. It appears there was wear from working rivets some on beam top so a DER approved a 2024 .063 strap about 13" long with a second layer near the middle. Existing rivet spacing. The strap is on top of the beam at the elbow area where the beam ramps up just behind the engine.

There is an 8110-3 and 337 on file in the OK city data search for this.

I have always thought but maybe wrong the turbocharged twin Cessnas had no repairs allowed to the mount beams. Has anyone else seen this type of repair?

There is a service bulletin about engine beam and canted bulkhead corrosion on non-421 twin Cessnas. There was no repair procedure in the SB that I recall. If any corrosion pits were too deep the beam had to be replaced. We replaced a beam on each side and both canted bulkheads on each side of a 414.

that's the reason for a DER approved repair. A good DER can engineer a satisfactory repair that restores the integrity of the beam without replacing it.

If no repairs were allowed, it would have to be stated somewhere that is FAA approved, such as an AD, TCDS, Limitations, etc.

I found a shop in Texas doing the same repair on multiple airplanes. Will see next week if it's the same DER approval data but at least it's not a one off repair.

Charlie, call Air Impressions at Waco with your question. They probably maintain more Cessna 340s, 414s, and 421s than any other shop in the US.

Chris C.