ASN Wikibase Occurrence # 359061
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| Date: | Monday 1 May 1995 |
| Time: | 11:20 LT |
| Type: |  McDonnell Douglas DC-10-10 |
| Owner/operator: | United Airlines |
| Registration: | N1811U |
| MSN: | 46610/32 |
| Total airframe hrs: | 63749 hours |
| Engine model: | CFM CF6-6 |
| Fatalities: | Fatalities: 0 / Occupants: 192 |
| Aircraft damage: | Minor |
| Category: | Serious incident |
| Location: | Chicago, IL -
 United States of America
|
| Phase: | Take off |
| Nature: | Unknown |
| Departure airport: | , IL (KORD) |
| Washington, DC (KIAD) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The flightcrew reported that during the application of takeoff power, when the throttles were in approximately the vertical position, the numbers 1 and 3 engines were indicating approximately 70% N1. The number 2 engine was indicating about 48% N1 and not accelerating. They heard a 'crack' and aborted the takeoff. Examination of the engine revealed that the low pressure turbine (LPT) stage one disk had separated from the LPT rotor at the stage one to two flange joint. Seven intact toroid bolts and sets of associated hardware were recovered. No evidence of fatigue cracking or corrosion (pitting) was noted on any of the bolt pieces recovered from the engine. The shank of one of the toroid bolts exhibited significant damage. The lug arm, used for safetying the bolt, exhibited relatively minor damage. Examination of several of the lug arms revealed 'noticeable wear patterns' and 'crack arrest positions indicative of fatigue cracking.' Statements by UAL maintenance personnel indicate failures of the toroid bolt safeties are occasionally discovered when the engines are disassembled for major overhaul.
Probable Cause: failure of the safety wire and/or safety wire lug arm on one of the stage one to two disk flange bolts due to an inadequate safetying method.
Accident investigation:
 |
|
Sources:
NTSB CHI95IA142
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 15-Mar-2024 06:33 | ASN Update Bot | Added |
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