A-89-095
NTSB Safety Recommendation — Aviation
Recommendation text
TO THE FEDERAL AVIATION ADMINISTRATION: Conduct a directed safety investigation (DSI) of the general electric cf6-6 turbine engine to establish a cyclic threshold at which the fan forward shaft and the fan disks should be separated and inspected for defects in the components. The DSI should include a review and analysis of: (a) the certification, testing, and stress analysis data that were used to establish the life limits of the fan disks and fan shaft components and the recommended inspection frequencies for these components; (b) the manufacturing processes associated with the production of the fan assembly and fan forward shaft; (c) metallurgical analysis of the front flange of the fan forward shaft in which cracks were recently discovered; (d) the maintenance practices involved in the assembly and disassembly of the fan disks and the fan forward shaft for the potential to damage the components during these processes; (e) nondestructive inspection of spare fan disks and fan forward shafts beginning with those components with the highest number of cycles in service; and (f) nondestructive inspections of fan disks on installed engines that may be performed by an approved inspection procedure. (Superseded by A-90-088) (Urgent)
In plain language (FlightFinder summary)
The Federal Aviation Administration is asked to conduct a directed safety investigation (DSI) of the General Electric CF6-6 turbine engine. The goal is to establish a cyclic threshold for separating and inspecting the fan forward shaft and fan disks for defects. The investigation must review certification and stress analysis data, manufacturing processes, metallurgical analysis of cracks found in a fan forward shaft flange, maintenance practices, and nondestructive inspections of spare and installed components.
This plain-language summary is written by FlightFinder to explain the recommendation above. It is not the official wording — the verbatim NTSB text is quoted above.
Details
| Status | Closed - Superseded |
|---|---|
| Mode | Aviation |
| Closed | Jun 18, 1990 |
| NTSB number | DCA89MA063 |
| Addressees | FAA |
External links
NTSB safety recommendations are advisory; addressees are not legally required to adopt them. Source: NTSB CAROL (public domain).