NTSB · Safety Recommendation
Safety Recommendation A-99-023
Recommendation
TO THE FEDERAL AVIATION ADMINISTRATION: Amend 14 Code of Federal Regulations Section 25.671(c)(3) to require that transport-category airplanes be shown to be capable of continued safe flight and landing after jamming of a flight control at any deflection possible, up to and including its full deflection, unless such a jam is shown to be extremely improbable. (Supersedes Safety Recommendation A-96-107, A-96-109, A-96-112, and A-96-113)
Safety Issue and Context
On 9/8/94, about 1903:23 eastern daylight time, USAir (now US Airways) flight 427, a Boeing 737-3B7 (737-300), N513AU, crashed while maneuvering to land at Pittsburgh Int'l. Airport, Pittsburgh, PA. Flight 427 was operating under the provisions of 14 code of federal regulations (CFR) part 121 as a scheduled domestic passenger flight from Chicago-O'Hare Int'l. Airport, Chicago, Il, to Pittsburgh. The flight departed about 1810, with 2 pilots, 3 flight attendants, and 127 passengers on board. The airplane entered an uncontrolled descent and impacted terrain near Aliquippa, PA. All 132 people on board were killed, and the airplane was destroyed by impact forces and fire.
Visual meteorological conditions prevailed for the flight, which operated on an instrument flight rules flight plan.
Response History
December 2, 2025 · NTSB Correspondence · FAA
We note that, on August 27, 2024, the FAA published its final rule, “System Safety Assessments,” which amends Title 14 CFR 25.1309(b)(1)(ii) to prohibit a proposed design from allowing any single failure that could result in a catastrophic failure condition (that is, a fail-safe design requirement). The final rule also revised the requirements for safety assessments of flight control systems installations to make them consistent with the requirements for other systems regarding prohibiting catastrophic single failures. We believe the final rule is consistent with the notice of proposed rulemaking and satisfies the intent of Safety Recommendations A-99-22 and -23.
Consequently, the Board has voted to classify these recommendations CLOSED—ACCEPTABLE ACTION.
January 10, 2025 · Recipient Response · FAA
-From Michael G. Whitaker, Administrator: The FAA published the System Safety Assessments (SSA) Final Rule in the Federal Register on August 27, 2024 (89 FR 68706). This rule addresses the risk from latent failures, including control systems jams and the risk of wear-related failures, by modifying § 25.671, General, and § 25.1309, Equipment, Systems, and Installations. Additionally, the FAA has issued three new Advisory Circulars (ACs) and amended two existing ACs to provide guidance material for acceptable means, but not the only means, of showing compliance with the regulations in this final rule. These ACs are available in the public docket for this rulemaking:
• AC 25.671–1, Control Systems – General. • AC 25.901–1, Safety Assessment of Powerplant Installations. • AC 25.933–1, Unwanted In-Flight Thrust Reversal of Turbojet Thrust Reversers. • AC 25.629–1C, Aeroelastic Stability Substantiation of Transport Category Airplanes. • AC 25.1309–1B, System Design and Analysis.