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PA12 with PA18 tail rigging

P

Pete Lastrucci

Registered User
Johannesburg, South Africa
I have a PA12 with an O320 Lycoming.

It has the PA18 stab / elevators fitted as one of the mods for the bigger engine.
Is the standard (PA12) elevator deflection of +27 deg up and 32 down correct, or would the PA18 spec of 25up and 15down now apply?

Secondly what is the correct rigging procedure for the elevator position in relation to the front belcrank / joystick fore aft position. (ie aircraft level, stab and elevator 0 degrees, now the position of the stick?)

A bit of concrete advice here would really be appreciated as I cannot find this info anywhere!:oops:

Pete Lastrucci
South Africa
 
Last edited:
If the STC doesn't specify a change in control surface deflection then it would remain unchanged from the Type Certificate Data Sheet.

Rig so the rear stick doesn't hit the seat.
 
Thank you for the info Steve!
Another question (I am a little embarrassed by this:oops:) where are the elevator stops located on the PA12 to ensure the specified up and down deflection?

There is a flat tab welded on the forward side of the rudder post, but the lower part of the elevator horn barely comes in contact with it and at the stop, there is about 45degrees of Up.. waay too much deflection.

The PA18 stab / elevator are brand new certified parts from Univair.
 

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That is how it is on an 18. I am not sure but believe the 12 is the same. more is better in my opinion.
 
I have finally determined how the elevator up travel is limited and why I was getting way above spec travel.. this part (40981-00 lower link) was missing on my PA12 and it only had a simple link without the extended stop.

Problem is I cannot find this part on Univairs list, it only shows the one for the PA18 (part# U41271-002 pic below) which am sure will limit the up travel to 25 degrees as per PA18.

Have still not managed to find what the travels should be for the 18 elevator mod on the PA12.
Does anyone have this info off any of the STC's, this gen would be much appreciated!
 

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If the STC you bought does not call out any different control surface deflections it would remain what the TCDS calls out for the PA12.
 
Hi Pete,

The stops as indicated on your picture are correct. The elevator horn contacts the tube for down elevator and the link contacts the angle on the tailpost for the upper limit. The link called out in the PA-12 parts manual is 40981-00. It is not listed on the Univair site When first installed on the new tail, the elevator up limit was restricted by quite a bit. I need to shorten the link by about 1/2 " to achieve the limits specified in the TC. For a point of reference, the limit was not reached until the elevator horn touched the angle on the tailpost.

I have the STC SA5-33 for installation of the -18 tail surfaces on my -12. It does not specify elevator travel limits, so, as Steve says, go with the limits as specified on the type certificate for the -12. I'll get the measurement for the link a bit later. Its at the hangar.

Wayne
 
Much appreciated Wayne and Steve. I made up a lower elevator horn link/stop out of 4130 plate and assembled everything. I now have within tolerance (31deg down and 28 up as per std PA12) travels, the rear stick clears the back of the front seat in full fwd pos.

I am very happy to have this finally sorted.. thanks for the advice guys!8)
 
A picture of the link lifted from Northland or supercubproject:
attachment.php

​

​
Dimensions and part numbers


Part Number L A
41271 2 1/ 8 9/16
41271-2 2 1/ 2 15/16
41271-3 2 7/16 7/ 8
40981-00 2 5/ 8 1 1/16


For my -12 with the tail repair section from Univair, I will have to use the 41271 to get correct up elevator deflection


Wayne
 

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Wayne thank you very much for the detailed info it is really appreciated!

Am now coming close to completion and looking forward to flying my 12 after an 8 year restoration:)
Pete
 
Steve Pierce said:
If the STC doesn't specify a change in control surface deflection then it would remain unchanged from the Type Certificate Data Sheet.

Rig so the rear stick doesn't hit the seat.
Click to expand...

Steve, can you give a hint on how to prevent this? I’m rigging the tail and the degrees are accurate but the rear stick still hots the pilot seat back at full forward deflection. Thanks!
 
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