Archives

Archive for

New FAA Guidance Could Affect Parts Related to Engines and APUs: Open for Comment

The FAA has published for public comment a draft advisory circular on “Uncontrollable High Engine Thrust/Power (UHT) Failure Conditions.”

The draft AC interprets 14 C.F.R. § 25.901(c) to require that the safety analysis include an analysis of UHT failures.  Under this new interpretation, when PMA parts potentially affect the powerplant or the APU, or if they affect the interface between airframe and engine/APU, it appears that the FAA may ask future applicants to meet 25.901(c).  Potentially, this could be applied to each aircraft on which the engine or APU is eligible for installation.

The regulation being interpreted currently reads as follows:

c) For each powerplant and auxiliary power unit installation, it must be established that no single failure or malfunction or probable combination of failures will jeopardize the safe operation of the airplane except that the failure of structural elements need not be considered if the probability of such failure is extremely remote.

This new interpretation appears to be a burden that was not anticipated at the time that the regulation was promulgated.  Subsection (c) was originally promulgated in 1970, and originally merely required that the 25.1309 analysis be performed (the preamble to the final rule clarified that this was sufficient). In 1970, the analysis was supposed to be an installation fault analysis.  The rule was changed in 1977 in order to “provide for a higher degree of airplane-engine compatibility.”  But the UHT issue appears to be unrelated to airplane-engine compatibility, so requiring this as an element of the 25.901(c) analysis seems like an expansion of what the regulation was designed to require.  Such an expansion of scope typically requires an amendment to the the regulation.

Moreover, it appears that the FAA has anticipated that the burden of this new analysis might be unreasonable, and therefore they have specifically invited design approval applicants to petition for exemption from this provision (the invitation exists within the body of the draft AC).

Do you see any impact to your PMAs (current or future)?  How does this affect your business?  Let us know so that MARPA’s comments on this policy can reflect your interests.

Comments on this draft AC are due to the FAA by September 4, 2017.  We would appreciate your comments to MARPA by August 28, so we can reflect them in our own comments.

New FAA Guidance on Propeller PMA Parts – Open for Comment

The FAA has published a draft policy statement on PMAs for critical propeller parts.  The draft policy statement is entitled “Parts Manufacturer Approval (PMA) for Propeller Critical Parts and Category 1 Propeller Parts.”  If this policy effects you, then we need to know your opinion before we file the MARPA comments on this draft policy!

The essence of the proposed policy appears to be:

  • Defines a set of parts subject to enhanced oversight that includes:
    1. Critical propeller parts identified by § 35.15 Safety analysis
    2. Parts identified as critical in FAA Order 8110.42D
    3. Category 1 parts defined in FAA Order 8120.23A [this could have the effect of applying critical parts requirements to parts that are not critical under the FAA regulations]
    4. Parts with airworthiness limitations
  • Defines certain parts as presumptively critical:
    • Certain blades, hubs, and counterweights
    • Certain primary load path blade retention parts, such as ferrules and blade clamps
    • Certain metallic blade erosion shields
    • Certain blades and counterweights
    • Certain blade pitch change pins
    • Certain pitch change links, yokes, and forks
    • Pitch change system parts:
      • Pressure cylinder, piston, actuator, seals, and springs
      • Beta feedback rods
      • Low and high pitch stops
      • Oil transfer tubes
    • All parts of the propeller control system:
      • Governors
      • Propeller control units
      • Propeller electronic controls
      • Propeller servo valves
  • Requires that an applicant seeking to PMA parts subject to enhanced oversight must coordinate the application with the certificate management ACO (for the type certificate) and the Engine and Propeller Directorate
  • Imposes on the PMA applicant a series of life management obligations for parts subject to the policy:
    1. The PMA applicant is responsible for determining if the part has been life assessed;
    2. A part specific certification plan is required for life assessed critical PMA propeller part(s);
    3. The part specific certification plan must include a fatigue life methodology that supports a continued airworthiness life management program (this appears to be something potentially more than the service management process required by the regulations).
    4. When managing propeller critical parts and category 1 propeller parts, the applicant must provide a program to monitor those parts and establish a life management program.

One concern is that a major propeller effect (as defined in 14 C.F.R. 35.15(g)(2)) is different from a hazardous propeller effect (as defined in 14 C.F.R. 35.15(g)(1)).  Only parts whose failures result in hazardous propeller effects are propeller critical parts under 14 C.F.R. 35.15(c).  And only propeller critical parts are required to meet the integrity establishment requirements of 14 C.F.R. 35.16.  But the policy document establishes additional classes of parts that will be subject to section 35.16.  Some parts with major propeller effects (as defined in 14 C.F.R. 35.15(g)(2)) could also be characterized as category 1 parts under FAA Order 8120.23A.  This policy memo appears to subject those parts to an inappropriate requirement by conflating them with propeller critical parts and requiring that they comply with the integrity establishment requirements of 14 C.F.R. 35.16.  This appears to be a potential de facto change to the regulations.

What do you think?  Do you have category one parts whose failure only reflects a major propeller effect and not a hazardous propeller effect?

Do you see any different impact?  Anything we’ve missed?  How does this affect your business?  Let us know so that MARPA’s comments on this policy can reflect your interests.

Comments on this draft are due to the FAA by August 31, 2017.  We would appreciate your comments to MARPA by August 24.