STC Limitations and Conditions
 

This is a question outside of the airline and transport world, but I am trying to get some guidance on a situation (before getting a lawyer involved) to move forward with a business I am starting.

I have an STC which applies to Cessna 172 models F,I,K,L,M,N,P,Q,R, and S variants. In the Limitations and conditions there is a line that states "This STC is applicable only to Cessna 172 models with 150 HP engines, or greater, and STOL wingtips."

After doing some research, I have come to find out that there are no "STOL wingtips" that exist for the late model 172's (R & S). Aside from getting field approval for the deviation on a 172R, how should I approach this wingtip requirement of the STC when it is impossible to install the "STOL" wingtips on the R & S models?

Definitely an Airworthiness related question, better suited for a current & qualified A&P /IA or FSDO Airworthiness Inspector with expertise in that area... Have you asked your mechanic? How about the local FSDO? I would not attempt to "interpret" the STC without seeking professional advice.

I have contacted the FSDO and was told I would have to gather substantiating data to start the field approval process for the deviation. However, that was before I discovered that there are no wingtips available for the late models (and even the M/N models unless you get a Sportsmans STOL kit).

You might need to seek the services of a DAR, not my area of expertise, sorry.

Your limitation line appears intended to state that the limitation applies:
A) to 172 models with greater than 150 hp
B) to 172 models with "STOL wingtips."

As not all 150 hp powered 172's employ stol wingtips, and your statement seems to imply that it's to aircraft with 150 hp or greater or that have STOL tips, then why not put the language to say as much.

Or do you only limit the use of your STC to those aircraft that have both an engine of 150 hp or greater and STOL tips?

It's okay to spell out exclusions, if known, or to be specific in the applicability or effectivity of the STC.

A DAR is always a good idea of you're seeking an approval. The cost of what's involved in an approval depends on what you're trying to accomplish.

Use caution seeking counsel at the FSDO level.

I should have been more clear - I am not the author of the STC, just an end user. But yes, what you are saying is what I'm trying to figure out: whether the wingtip requirement is an implied "and/or" or firmly "and".

You're not very clear at all, actually. Be specific and share what it is, and the details of the language.

Actual STC L&C text attached.

Again, not enough information is provided. What STC is this? For what?

It clearly reads "and". There's no way to read it as "and/or". So you've gotta have both >=150 HP and STOL wingtips. Your wiggle room may come in how STOL wingtips are defined.