Engine swap

[exftrplt]

On a Cessna 172 N with an O320 H2AD engine. If we change to an O320 D2J engine. Would you consider this to be a major alteration or a minor alteration?

[rwanttaja]

I'm certainly no expert, but from the Type Certificate Data Sheet, the H2AD is the approved engine for the 172N and the D2J is the approved engine for the 172P. Comparing the TCDS between the two, you see minor changes in RPM ranges and limitation airspeeds (such as the maneuvering speed). Offhand, I can see some issues due to these slight differences and you might want to count on this being considered a major alteration.

Then again, someone may have gone down this road before and greased the skids.

Ron Wanttaja

[FlyingRon]

I agree with (the other) Ron on this. Some TCs (like the Navion) provide for multiple engines being eligible on different serial numbers. Those you can change with a logbook entry.
In this case, it's a major alteration, and in the past you could have gotten it approved with a one off STC if you could find someone else's paperwork on it. That's rather hard to do in today's regulatory ass covering.
However, all is not lost. There are STCs (Penn Yan's DeltaHawk conversion for example) that allow that modification.