BeechTalk - BT

Username Protected · **Posted:** 11 Sep 2017, 09:45

I am wondering if the position of the back of the prop spinner is 1/4" lower than the cowling makes a difference in performance? I seem to recall that I heard somewhere that the spinner height should be closer (even with) the height of the hump in the cowling. I believe that can be adjusted by adding a washer to the front mount. Anyone else experienced a similar issue? Thanks :scratch:

Username Protected · **Posted:** 11 Sep 2017, 09:50

Maybe under thrust load it lines up?

Username Protected · **Posted:** 11 Sep 2017, 10:28

Jim Are you not a member of Cessna Twin Flyers ?

If not I highly recommend joining .

This would be a good question for the Tech Guru, Tony Saxton, THE PREEMINENT Twin Cessna Expert.

Username Protected · **Posted:** 11 Sep 2017, 13:05

Thanks Michael, I am a member but rarely use it. Obviously not the same with BT. I'll see if Tony has an opinion.
:cheers:

Username Protected · **Posted:** 11 Sep 2017, 13:39

I know on Bonanzas if it is like that it indicates worn engine mounts.

Username Protected · **Posted:** 11 Sep 2017, 22:46

Username Protected wrote:

Thanks Michael, I am a member but rarely use it. Obviously not the same with BT. I'll see if Tony has an opinion.
:cheers:

Tony rarely posts on the forum, but you can email him directly via TCF.

Username Protected · **Posted:** 11 Sep 2017, 23:05

It's nice if the top of the prop spinner matches the top of the cowling but not necessary.

You can add washers or new motor mounts to shim the engines up. The performance gain will be negligible and hard to detect.

On the 421C the engines can pull down as much as a 1/2" at full power.
Next annual I am replacing everything firewall forward with Factory New engines and accessories. At that time I will shim the new engines so they are slightly above the cowling.

I would not spend the money to shim the engines up any other time unless they are really sagging.
Jerry

Cessna 421 question