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Friday, May 25, 2012


New STC Compatibility Verification Services Offered

Terry Bowden, FAA Consultant DER  is collaborating with Certified Aeronautical Products and other FAA designees across multiple technical disciplines to offer a new service called STC Compatibility Verification.  The service is aimed at providing installers the means to address the compatibility verification with reliable and professional results.

In a recent letter to the FAA, the National Transportation Safety Board (NTSB) made recommendations aimed at improving safety of aircraft, which have multiple modifications.  The letter cites several actual crashes that were attributed to conflicting modifications made on aircraft via Supplemental Type Certificate (STC) installations.  One of those aircraft had 22 STC modifications since leaving the factory.

See the NTSB Letter Here.

The FAA has responded by issuing a SPECIAL AIRWORTHINESS INFORMATION BULLETIN # CE-12-37.  This document, titled "STC Modification Airworthiness Interrelationship Effects" focuses on Airspeed Limitations and Markings.

With the number and complexity of STC modifications ever increasing on individual aircraft, safety could be compromised by adding a modification that itself might be considered a safety improvement.  The check for STC compatibility for some airplanes has become quite difficult for installers to manage. Installers may lack the expertise for making the compatibility check.  Some situations may demand qualifications that only experienced Designated Engineering Representatives (DERs) or Designated Airworthiness Representatives (DAR's) can provide. 

What drives this?

STC installers are required to address the following standard statement under the STC "Limitations and Conditions".

This approval should not be extended to other aircraft of this model on which other previously approved modification[sic] are incorporated, unless it is determined by the installer that the interrelationship between this change and any other previously approved modifications will produce no [sic] adverse effect upon the airworthiness of that airplane.
STC installers have long been subject to this (or similar) STC limitations.  Are you one of the STC installers that have struggled with knowing how to make this determination?

Why not let qualified professionals handle this?

Contact Terry today
(254) 715-4773

What does the STC Compatibility Verification entail?
We run a background check on the aircraft through a study of FAA records or other information you provide regarding the aircraft's history of major repairs and alterations.  We compare the scope of previous changes vs. the proposed changes and review them against FAA airworthiness requirements.  We provide you, the installer, with a thorough assessment of the proposed STC to be installed and it's potential impact on or affects from previously installed modifications.  We will make recommendations as necessary to address incompatibilities that should be resolved to ensure safe implementation of the proposed STC.

How much does this cost?
Costs can vary depending on the number of prior mods and the complexities of the systems or airworthiness considerations involved.  We charge a flat fee of  $500.00 to address most circumstances.  This includes comparing up to 4 STCs and up to 8 hours of work.  If the job entails more time, we charge an hourly rate that can depend on the resources needed.  (This rate is generally around $100.00 per hour.) 

It is worth having the peace of mind that the job was done right!

Contact Terry today
(254) 715-4773

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