Date & Time:
Apr 5, 1982 at 1615 LT
Type of aircraft:
Piper PA-31-350 Navajo Chieftain
Operator:
Aircraft Service Center
Registration:
N123CB
Flight Phase:
Flight
Flight Type:
Executive/Corporate/Business
Survivors:
Yes
Site:
Plain, Valley
Schedule:
Austin - Tifton
MSN:
31-7752161
YOM:
1977
Country:
United States of America
Region:
North America
Crew on board:
1
Crew fatalities:
0
Pax on board:
4
Pax fatalities:
0
Other fatalities:
0
Total fatalities:
0
Captain / Total hours on type:
113
Aircraft flight hours:
1611
Circumstances:
As the pilot was descending from 7,000 to 5,000 feet, he heard a loud bang, followed by a temporary vibration and a violent swerve to the right. He looked out the right window and thought the right engine had fallen off since all he could see was the tops of the engine mounts. The aircraft was controllable only after reducing the left engine power to idle. During a wheels up/forced landing, the plane tore through a fence, slid across a paved road, went over an embankment and began burning after it came to rest. The pilot received a back injury and had difficulty egressing. An investigation revealed the propeller hub had failed from fatigue which resulted in blade separation and subsequent engine tearaway. The engine had remained attached to the airframe by cables. Metallurgical examination of the hub revealed that the fatigue originated at a threaded grease fitting. Gouging was visible on the inner wall. A set of incorrect counterweights were found on the propeller. The counterweight's function was to reduce vibration.
Probable cause:
Occurrence #1: airframe/component/system failure/malfunction
Phase of operation: descent - normal
Findings
1. (f) propeller system/accessories,counterweight - incorrect
2. (f) maintenance,major repair - improper - other maintenance personnel
3. (f) propeller system/accessories - vibration
4. (f) propeller system/accessories,hub - other
5. (f) maintenance - improper - other maintenance personnel
6. (c) propeller system/accessories,hub - fatigue
7. (c) propeller system/accessories,blade - separation
8. (c) engine assembly - separation
----------
Occurrence #2: forced landing
Phase of operation: landing - flare/touchdown
----------
Occurrence #3: in flight collision with terrain/water
Phase of operation: landing - flare/touchdown
Findings
9. Wheels up landing - intentional - pilot in command
----------
Occurrence #4: on ground/water collision with object
Phase of operation: landing - roll
Findings
10. (f) object - fence
----------
Occurrence #5: on ground/water encounter with terrain/water
Phase of operation: landing - roll
Findings
11. (f) terrain condition - rough/uneven
Phase of operation: descent - normal
Findings
1. (f) propeller system/accessories,counterweight - incorrect
2. (f) maintenance,major repair - improper - other maintenance personnel
3. (f) propeller system/accessories - vibration
4. (f) propeller system/accessories,hub - other
5. (f) maintenance - improper - other maintenance personnel
6. (c) propeller system/accessories,hub - fatigue
7. (c) propeller system/accessories,blade - separation
8. (c) engine assembly - separation
----------
Occurrence #2: forced landing
Phase of operation: landing - flare/touchdown
----------
Occurrence #3: in flight collision with terrain/water
Phase of operation: landing - flare/touchdown
Findings
9. Wheels up landing - intentional - pilot in command
----------
Occurrence #4: on ground/water collision with object
Phase of operation: landing - roll
Findings
10. (f) object - fence
----------
Occurrence #5: on ground/water encounter with terrain/water
Phase of operation: landing - roll
Findings
11. (f) terrain condition - rough/uneven
Final Report:
N123CB.pdf87.53 KB
