What’s the REAL rub between Pratt & Whitney and this FAA AD?

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 Story seems to think it’s $

 Airworthiness Directive shows differences in degree of action needed

FAA wants $13.6M fix to Pratt's turbofan engines


The FAA published in the October 12,2017 Federal Register (82 FR 47405) a Notice of Proposed Rule Making (NPRM) which ,under its 14 CFR Part 39 powers, to issue a  new airworthiness directive (AD) for


all Pratt & Whitney Division (PW) PW4052, PW4056, PW4060, PW4062, PW4062A, PW4152, PW4156A, PW4158, PW4460, and PW4462 turbofan engine models, including engines identified with suffixes -1C, -1E, -3, -3A, or -3B. This proposed AD was prompted by the discovery of multiple cracked 4th stage low-pressure turbine (LPT) air seals in the fleet.


That is not an unusual occurrence; there are as many as 60 such documents issued a month. That is not to say that an AD is a trivial matter; for, by definition, such an action is an indication that there is a safety matter which the FAA needs to be fixed.

Federal Register airworthiness directive


The HartfordBusiness.com headline and the article’s introductory sentence focus of a $13.6M figure which P&W must pay (to the FAA?). Clearly, the OMB requirement that any federal agency proposing to issue a rule or policy must provide an estimate of the contemplated action’s costs. The FAA, dutifully, did the math in this table:

While it is interesting that the FAA indicated that there was $0 labor cost and that the cost of a 4th stage low-pressure turbine (LPT) air seal is $13,800 per seal (one of many such incredibly expensive parts in the PW4000 series turbofan engines), the real HEADLINE is buried in the technical jargon of the AD.



Pratt & Whitney, eight months ago discovered and disclosed the phenomena of the cracking of this seal in two documents:


  • PW Alert Service Bulletin (SB) No. PW4ENG A72-830, Revision 1, dated May 2, 2017. This PW Alert SB provides instructions for replacement of the 4th stage LPT air seal.
  • P&W Cleaning Inspection Repair (CIR) Manual, P/N 51A357, Task 72-53-24, Repair-02.

As noted in the article, “Pratt Spokesman Matthew Bates said. ‘We have already begun replacing this part as the engine fleet comes in for regularly scheduled service and will continue to address the issue as part of the service schedule.’”


There’s the rub. Pratt & Whitney has on its own initiative ordered its customers to replace the seals at the next scheduled service. The FAA AD mandates that

At the next disassembly of the LPT module, remove 4th stage air seal, P/N 50N346, from service and replace with a part eligible for installation.

The significant questions raised by the AD are:

  • Why did the FAA feel compelled to issue an AD which almost mimic’s the Service Bulletin (issued last May)?
  • If the need for corrective action merited an AD, why did the FAA wait five months to propose this requirement?



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