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Aircraft Parts, aviation, FAA, FAA Design Approval, Manufacturing, PMA, Policy, Regulatory

Vibration Rule – Still In the Works?

We spoke today with several FAA policy-makers about the Engine Vibration rule change which had been published and then withdrawn in 2012.

This conversation was a follow-up to the FAA publication of a technical amendment that would have required full engine testing for vibration compliance.  The FAA representatives explained that they wanted to explore the reasons for MARPA’s concerns over the rule (the rule had been withdrawn based on MARPA’s objection).

They asked about our concerns with the rule.  They asked about whether a change to the preamble would have been enough to salvage the rule.  We answered that IF their intent was to apply the full engine test requirement to only TC applicants (as FAA employees had indicated in an August 27, 2012 phone conversation) and not to PMA/STC applicants then merely changing the preamble would be insufficient, because the problem lay in the (withdrawn) rule language itself.  We pointed out that the (withdrawn) rule language would have appeared to have required full engine vibration testing.  Component-level testing (which is currently permitted for PMA applicants) would have been available as a supplement to full engine testing (and not as an alternative, as currently permitted by AC 33-83-1).

We asked what the FAA’s goals were with respect to the rule, and explained that MARPA would be happy to work with the FAA to help them meet their safety goals in a way that does not undermine industry’s ability to obtain PMAs.  They responded “We are not sure where we’re going.”

They asked whether the existence of AC 33.83-1 had any impact on MARPA’s concerns and I reminded them that a common rule of regulatory construction is that a rule change that causes a rule to conflict with guidance invalidates the conflicting guidance.  So if the rule had not been withdrawn then we would have been unable to use AC 33.83-1 to the extent it permitted anything less than what the new rule required

They asked about the economic effect of their rule.  I explained that in a static model (of the sort used by federal economists) that it would have had a tremendous effect because it would have made engine PMAs much more expensive to obtain.  I noted that in a dynamic model, the likely real world effect could have been to stop engine PMA applications because it could become economically impractical for PMA applicants to perform full engine vibration testing in lieu of the methods made available by AC 33.83-1 (as opposed to using the reasonable methods currently permitted in the AC).  Neither of these models appear to produce economic results that are favorable for America.

Later in the conversation I reiterated that MARPA would be happy to assist the FAA in crafting language if they could just tell us what their goals are in the rule change exercise.  They explained that “We are not yet prepared to say what our goal is.“  They also explained that they felt the ex parte rules and standards precluded them from disclosing any information about their thoughts or purposes (the ex parte rules do permit the FAA to engage in pre-rulemaking ex parte contacts to obtain technical and economic information).

What does this mean for the PMA Community?  It means that the FAA appears to be working on another change to the vibration rule of 14 C.F.R. 33.83.  It means that they recognize that such changes are potentially controversial and thus they are collecting data to try to improve the next iteration of the rule.  But it also means that the Engine Directorate is as-yet unable to elucidate a cogent rationale for why they would like to change the vibration rule.  This is something we will be looking for in the coming months.


About Jason Dickstein

Mr. Dickstein is the President of the Washington Aviation Group, a Washington, DC-based aviation law firm. He represents several aviation trade associations, including the Aviation Suppliers Association, the Aircraft Electronics Association, the Aircraft Fleet Recycling Association and the Modification and Replacement Parts Association.


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