A-90-088
NTSB Safety Recommendation — Aviation
Recommendation text
THE NTSB RECOMMENDS THAT THE FEDERAL AVIATION ADMINISTRATION: DEVELOP, WITH THE ASSISTANCE OF GENERAL ELECTRIC AIRCRAFT ENGINES, AN ALTERNATE METHOD OF INSPECTING THE BORE AREA OF THE CF6-6 ENGINE FAN STAGE I ROTOR DISKS FOR THE PRESENCE OF SURFACE CRACKS; ISSUE AN AIRWORTHINESS DIRECTIVE TO REQUIRE THAT THESE DISKS BE INSPECTED WITH THIS METHOD ON AN EXPEDITED BASIS, THAT DISKS FOUND TO HAVE CRACKS BE REMOVED FROM SERVICE, AND THAT THE INSPECTION BE REPEATED AT A CYCLIC INTERVAL BASED UPON THE CRACK SIZE DETECTABLE BY THE INSPECTION METHOD, THE STRESS LEVEL IN THE APPLICABLE AREA OF THE DISK, AND THE CRACK PROPAGATION CHARACTERISTICS OF THE DISK MATERIAL. (URGENT) (Supersedes Safety Recommendation A-89-095)
In plain language (FlightFinder summary)
The Federal Aviation Administration, with help from General Electric Aircraft Engines, is asked to develop a new way to inspect the bore area of CF6-6 engine fan stage I rotor disks for surface cracks. It must then issue an airworthiness directive requiring expedited inspections using this method, removal of any cracked disks, and repeated inspections at intervals determined by the detectable crack size, stress levels, and crack propagation properties of the disk material.
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| Status | Closed--No Longer Applicable |
|---|---|
| Mode | Aviation |
| Closed | Mar 4, 1991 |
| 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).