After 20 years, I have just noticed this
I’ve heard that the vertical stabiliser is often offset but I can’t see that on the TB20.
Starting with the 1964 S35 and the introduction of the IO520 into the Bonanza, the engine was canted 2.5 degrees to the right and 2 degrees down.
NCYankee wrote:
2.5 degrees to the right and 2 degrees down
Yep, same as my RC models 
The largest engine mounting offset I’m aware of is on the Ercoupe, 5 degrees right plus 3.5 degrees down. It’s a really easy plane to fly for this and many other reasons.
Just a few days ago I was explaining left turning tendency to my teenage son, and he informed me that this is why the engines are angled slightly to the right. I told him they weren’t, and that you have to use rudder to compensate. Clearly I need to be watching more YouTube/TikTok/whatever. 
How is this offset determined? Is it done at some cruise speed / power setting?
I haven’t thought this through properly, now or before, but it seems to me that you may not have to optimize the engine mounting angle for a given power (or speed?). Unlike the offset of the vertical stabilizer, both the turning moment you are correcting and one that corrects it are related to the engine power being produced.
It’s barely visible on the PA-28-161 I fly regularly, but it was super obvious on the Turbo Arrow (same basic cell) that was based here some years ago.
Peter wrote:
How is this offset determined?
Laterally you’re trying to compensate for the spiral slipstream, with the goal to use no aileron or rudder trim (causing additional drag) in cruise. So force and moment balances to ballpark it, then possibly flight tests to verify, nowadays probably all in simulations though.
The angle downwards is to match the plane’s attitude in level flight, so whatever your plane needs.
Peter wrote:
Is it done at some cruise speed / power setting?
It is very rarely printed explicitely in the POH, but I’d assume the recommended cruise setting.
Peter wrote:
Peter wrote:
After 20 years, I have just noticed this
That is bizarre. I was checking my plane carefully today, getting ready for a trip to Hvar on Saturday, and I noticed exactly the same thing and was quite concerned about it. Having just found this thread I am much happier. Thanks Peter!
Buckerfan wrote:
getting ready for a trip to Hvar on Saturday
Off topic: let us know the situation on LDSH – runway conditions, few pictures etc.
