FAA AD Watch: PC-24 Flight-Director Software and 757 PTU Wiring
Two November proposals, not final rules. The FAA would require PC-24 Primus APEX software and a revised AFM, and would correct 757 power-transfer-unit wiring errors left by AD 2024-25-09.
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Updated November 10, 2026
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News. Two FAA airworthiness proposals published on 3 and 4 November 2026 are open for comment. Neither is a final directive. Shops do not have a new compliance date from these documents. The final rule published the same week on Diamond DA 40 passenger doors is a separate action, covered in AD 2026-22-06.
PC-24: proposed software, comments by 21 December
The FAA proposes to supersede AD 2025-20-02 for Pilatus PC-24 airplanes. The NPRM is Docket No. FAA-2026-13798, Project Identifier MCAI-2026-00797-A, document 2026-22496, 91 FR 69506, published 4 November 2026. Comments are due 21 December 2026.
AD 2025-20-02, Amendment 39-23155 (90 FR 53208, 25 November 2025), already requires a temporary revision in the abnormal procedures of the airplane flight manual. The FAA issued that AD as an interim action after EASA AD 2024-0240, dated 10 December 2024. The unsafe condition is an inaccurate flight-director calculation on approach. The FAA says heading splits can put errors into the flight-director calculation and produce a lateral offset from the desired approach course. If not addressed, the agency says that could increase pilot workload and reduce safety margins. The subject code is JASC 3400, Navigation System.
Since that AD, EASA has issued EASA AD 2026-0149, dated 28 July 2026. The FAA's proposal would incorporate that EASA AD, with the exceptions written into the NPRM. Pilatus has developed Primus APEX DFZ Build 6.0 software and issued instructions to install it. Pilatus AFM-TR 02371-081 is the operational revision that applies after that software is installed. The proposed AD would keep the earlier abnormal-procedures revision, AFM-TR 02371-075, and add the software installation plus insertion of AFM-TR 02371-081 into the normal procedures.
Applicability would be PC-24 airplanes certificated in any category, as identified in EASA AD 2026-0149. Where that EASA AD refers to its own effective date, the FAA final rule would use the effective date of the FAA AD, which this proposal does not set. Where EASA refers to 24 December 2024, the effective date of EASA AD 2024-0240, the FAA proposal substitutes 30 December 2025, the effective date of AD 2025-20-02. A pilot who holds at least a private pilot certificate could revise the flight manual, because that step is a manual change, and would have to log it. The proposal would not require the report to Pilatus that the EASA material mentions. It would not adopt the EASA "Remarks" section.
The FAA estimates 150 airplanes of U.S. registry if the AD is adopted as proposed. Revising the flight manual is one work-hour at $85, or $85 per airplane and $12,750 for those U.S. airplanes, with no parts. Installing Build 6.0 and incorporating AFM-TR 02371-081 is four work-hours, $340, plus $1,000 in parts: $1,340 per airplane and $201,000 for the U.S. fleet. The FAA says some of that cost may be covered under warranty.
Until a final rule is published, AD 2025-20-02 remains the mandate. Build 6.0 is not an FAA requirement on the basis of this NPRM.
757 PTU: proposed wiring correction, comments by 18 December
The FAA proposes to supersede AD 2024-25-09 for certain Boeing 757 airplanes. The NPRM is Docket No. FAA-2026-11821, Project Identifier AD-2026-00567-T, document 2026-22383, 91 FR 69227, published 3 November 2026. Comments are due 18 December 2026.
AD 2024-25-09, Amendment 39-22911 (90 FR 1850, 10 January 2025), requires new relays and changes to wire bundles leading to the power-transfer-unit control valve. It was prompted by reports that the valve failed to open when commanded. The FAA says that failure, together with loss of the left engine or the engine-driven pump during takeoff, may keep the landing gear from retracting in time. The result the agency describes is extra drag, a reduced climb gradient, and an inability to clear obstacles, which can mean loss of continued safe flight and landing. The subject code is ATA 29, Hydraulic power.
The new proposal exists because the required bulletin was wrong. An operator reported errors in Boeing Alert Requirements Bulletin 757-29A0071 RB, dated 16 November 2023, that stopped the work on airplanes identified as Group 3. Boeing then found further errors affecting every group in that bulletin, including errors that would allow actions that could introduce new hazards. The FAA says it judged those new hazards to be relatively low risk in a quantitative assessment, and still a safety concern, because they could affect whether the power-transfer unit operates. The unit is a backup. The original unsafe condition also remains, the FAA says, because the work AD 2024-25-09 requires cannot be accomplished as intended on certain airplanes.
On 6 April 2026 the FAA issued Special Airworthiness Information Bulletin 2026-09, advising owners of the errors and recommending action before a superseding AD. That bulletin is advisory. Boeing has since issued Alert Requirements Bulletin 757-29A0071 RB, Revision 1, dated 28 May 2026. FAA letter 523-26-00077, dated 29 April 2026, identifies deviations already approved as an alternative method of compliance to AD 2024-25-09. The NPRM says doing the original bulletin together with the applicable alternative method in that letter produces a configuration consistent with Revision 1.
The proposed AD would apply to 757-200, 757-200PF, 757-200CB and 757-300 series airplanes identified in Revision 1. Depending on configuration, Revision 1 specifies new relays and a new connector in the P33 panel, new connectors and wire-bundle changes, general visual inspections of wire bundle W2514 routing and of a seal ring at the right body-fairing feed-through, an operational test, and on-condition corrections. Where Revision 1 dates compliance from its own revision date, the final rule would use the effective date of the new AD. That date is not in this proposal.
The FAA estimates 467 airplanes of U.S. registry. The combined relay, connector, wire-bundle and operational-test action is up to 45 work-hours at $85, or $3,825, plus $4,730 in parts: up to $8,555 per airplane and up to $3,995,185 for those U.S. airplanes. On-condition costs are separate. Re-routing wire bundle W2514 is estimated at $85 in labour and no parts. A seal ring is $85 in labour plus $10 in parts. The FAA says it has no definitive data on the cost of correcting a failed operational test.
Credit would be available, if the final rule is adopted as written, for work done before the new effective date using the 16 November 2023 bulletin plus the applicable alternative method identified in the 29 April 2026 letter. The proposal would also allow any open position on the P33 panel or on disconnect bracket AD0880 or AD0881 where the original figures specify certain positions. Alternative methods already approved for AD 2024-25-09 would be approved for the corresponding provisions of Revision 1. AD 2024-25-09 itself remains in force until a final rule supersedes it.
What is not in either document
Neither NPRM sets an effective date. The comment deadlines, 21 December for the PC-24 and 18 December for the 757, are not compliance dates. A terminating action, a parts kit beyond the cost tables, and any decision to adopt or change the proposals are outside these two texts.
