Fuel Efficiency Metric NPRM – New Rule Could Affect PMAs and STCs

The FAA is proposing a new set of standards applicable to aircraft. While the proposed rule suggests that only the large airframe manufacturers would be affected, the plain language of the rule appears to impose obligations on a wide variety of manufacturers and repair stations. Companies developing PMAs and/or STCs should be concerned about the way that this rule may affect them.

The standards would be published in a new Part 38. Their purpose would be to establish fuel efficiency standards.

The rule applies to propeller-driven aircraft with maximum take-off mass above 8618 kg (which seems to exclude Part 23 aircraft and include Part 25 aircraft). It also applies to jet aircraft with maximum take-off mass above 5700 kg (roughly, but not exactly, the large aircraft threshold; so this could include some normal category jet aircraft).

The rule is mean to apply only to production and modification of newer types, and therefore would only apply to modifications affecting in-service aircraft that are currently in production. This means that an out-of-production aircraft like the 757 would not be affected by the new rule. For in-production aircraft, they would be affected by the new standards if two conditions were met:

• the aircraft was produced after 1/1/2023 and
• the modification changes the Fuel Efficiency Metric (FEM) value

For aircraft where the type certificate application was made after January 11, 2021, all of those aircraft would be subject to the new modification rules.

As a practical matter, this is likely to mean that future applicants for STCs and modification PMAs (intended for affected aircraft) will need to perform an additional analysis to show that the modification does not affected the fuel efficiency of the aircraft. This reflects a brand new set of standards and new engineering analyses that have not been required for STCs and PMAs in the past.

Also, for aircraft subject to the new rule, any modification that increases the aircraft’s maximum take-off mass would require the applicant to demonstrate compliance with the applicable fuel efficiency limit, regardless of whether there is a change in the airplane’s FEM value.

The proposed rule has a cost-benefit analysis that seems to assume that only airframe manufacturers are affected by the rule. So either the rule needs to be drafted more carefully to narrowly address the FAA’s intended scope, or the cost-benefit analysis needs to be changed to better match the apparent scope of the plain language of the rule.

MARPA members and other interested parties are invited to let MARPA know your thoughts. If there is sufficient interest in this rule among the members then MARPA will file comments before the August 15th deadline.

For more information, see the proposed rule.