Assuming a type of plane has a technical issue that must be fixed related to its flight behavior, could the plane be derated to add safety margin (instead of banning it).

What I have in mind is having longer runway requirements, lower airport T, higher air pressure, softer rate of climb, lower take off weight, etc.

Could this work technically? Legally?

This is inspired by the recent crashes of Boeing 737 MAX-8s, but the question is about types in general.

  • $\begingroup$ Questions about on-going investigations are usually closed here because of their speculative nature. To try to avoid that, I've edited your question not to be specific to the recent 737 crashes. However, if you don't like my edit, you can revert it: click the "edited however-long-ago" link and you can select your original version to revert to. $\endgroup$ – David Richerby Mar 12 '19 at 17:51
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    $\begingroup$ Also, if anybody thinks that my edited version of the question is too broad to answer, please consider reverting rather than voting to close. $\endgroup$ – David Richerby Mar 12 '19 at 17:51
  • $\begingroup$ @DavidRicherby I was about to edit it myself when I read the rule about "ongoing investigations" elsewhere; it's a good rule too. $\endgroup$ – user37905 Mar 12 '19 at 17:55
  • $\begingroup$ Bit broad, as it would depend on the specific issue involved. $\endgroup$ – jwenting Mar 13 '19 at 4:51

There are a few regulatory options (I'll discuss FAA terms but many other agencies are similar)

(2) Supplement. Information that supersedes or is in addition to the basic AFM resulting from the issuance of a supplemental type certificate (STC), or from approved changes to AFM limitations, procedures, or performance information without an STC.

  • Required Training: The FAA can require some kind of additional training for a specific airframe. This is effectively what they did with the Mitsubishi MU-2 even though no type cert was needed to fly the plane.

The answer is yes, if there is an operational procedural restriction limitation that effectively mitigates the risk, without adding its own risks, and is something that is operationally feasible, pending a design change.

Examples would be an AD that:

Imposes a speed, altitude, weight or temperature limitation.

Imposes additional reserve fuel requirements (this was done for CRJ200s that had a problem with the flaps getting stuck while extended following a missed approach).

Limits operation in icing conditions (although for most airline operations this effectively grounds you, because "legal" icing conditions exist in any cloud above the freezing level).

All sorts of other system restrictions.


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