Arrow IV - S-TEC a/p STC restricted to later s/n airframes

[FourSeven]

Greetings fellow Piper owners,

I own an Arrow IV (NA) fitted with a Piper AutoControl IIIb. Sadly, this no longer works and my shop (who admittedly are not experts in antique analog autopilots) have advised that it's not worth spending money on.

Over the weekend, I thought I would spend a happy hour or so virtual-window shopping for a new autopilot. My initial thoughts turned to additional features I would like - notably alt-hold and approach modes. Having got myself excited, I started looking at practicalities like STCs.

S-TEC/Genesys seem to have the widest range of STCs and an autopilot I like the look of (55X) but when it comes to the Arrow IV, there is a gotcha. All of the S-TEC options for the Arrow IV come with the following caveat...

Eligible only on:

Piper Model PA-28RT-201, S/N 28R-7918070 and up and
Model PA-28RT-201T, S/N 28R-7931100 and up​

My serial number falls outside this range. I'm wondering what could be so different with the first 69 Arrow IVs that the STC is not applicable? Anyone here know? I have asked S-TEC for comment, but have yet to hear from them.

I am also interested in hearing about alternative autopilot suggestions that work well with the Arrow IV and (ideally) don't cost more than the aircraft.

Any advice gratefully received.

 

[EchoDelta]

 

[FourSeven]

 

[RNC]

 

[Dravnx]

 

[FourSeven]

 

[RNC]

 

[enough]

 

[TheDoc]

 

[sanjiv]