A relocation of a battery follows STC guidelines, but the battery is located 6 inches aft of the STC location and the aft center-of-gravity limit is exceeded by 0.1 inch. Concerning the installation, which statement is true?

A relocation of a battery follows STC guidelines, but the battery is located 6 inches aft of the STC location and the aft center-of-gravity limit is exceeded by 0.1 inch. Concerning the installation, which statement is true?

• A. The deviation to the supplemental type certificate is in itself a major alteration and will require additional approval.
• B. The installation could be approved for return-to-service if an IA inspects and approves the deviation.
• C. The 0.1 inch CG deviation is negligible by AC43.13-1A and may be approved as a minor alteration.
• D. The deviation invalidates the STC.

Answer: (A)

A change from the approved installation data becomes a major alteration when it affects weight and balance or other critical design assumptions. In this case, the STC specifies where the battery may be located and the aft CG limit. Moving the battery 6 inches aft and pushing the aft CG 0.1 inch beyond the STC data means the airplane is now configured outside the approved configuration. That kind of deviation alters the aircraft’s weight distribution and potentially its handling characteristics, which the STC did not authorize. Because of that, it requires formal FAA-approved action to modify the data—such as an STC amendment or an FAA field approval—before the aircraft can be returned to service. A field-approved IA endorsement cannot authorize this type of change, since it involves altering the design data. The 0.1 inch deviation is not automatically negligible under the STC data; the CG envelope defined by the STC governs whether the installation is acceptable. And while the STC isn’t automatically invalidated by a deviation, operating under an unapproved configuration would be improper until the required FAA approval is obtained.

A change from the approved installation data becomes a major alteration when it affects weight and balance or other critical design assumptions. In this case, the STC specifies where the battery may be located and the aft CG limit. Moving the battery 6 inches aft and pushing the aft CG 0.1 inch beyond the STC data means the airplane is now configured outside the approved configuration. That kind of deviation alters the aircraft’s weight distribution and potentially its handling characteristics, which the STC did not authorize. Because of that, it requires formal FAA-approved action to modify the data—such as an STC amendment or an FAA field approval—before the aircraft can be returned to service.

A field-approved IA endorsement cannot authorize this type of change, since it involves altering the design data. The 0.1 inch deviation is not automatically negligible under the STC data; the CG envelope defined by the STC governs whether the installation is acceptable. And while the STC isn’t automatically invalidated by a deviation, operating under an unapproved configuration would be improper until the required FAA approval is obtained.