Date & Time: Jan 13, 1987 at 1354 LT
Type of aircraft:
NAMC YS-11
Operator:
Registration:
N906TC
Flight Phase:
Flight
Flight Type:
Training
Survivors:
Yes
Schedule:
Indianapolis - West Lafayette
MSN:
2154
YOM:
1970
Crew on board:
3
Crew fatalities:
0
Pax on board:
0
Pax fatalities:
0
Other fatalities:
0
Total fatalities:
0
Captain / Total flying hours:
3913
Captain / Total hours on type:
1381
Circumstances:
The flight crew failed to adhere to appropriate procedures and directives when they failed to select the hp cock levers to the hswl (lock out) position while performing an approach to landing stall during a training/test flight. When stall recovery was initiated, both propellers 'hung up' when the high (cruise pitch) stops of each propeller failed to withdraw. As the power levers were advanced, turbine gas temperatures (tgt's) exceeded limitations; the left propeller auto-feathered, the right propeller was later feathered by the captain. Restart procedures were attempted without success, and a forced landing in a plowed cornfield ensued. Examination of the engines revealed that the turbines had been 'subjected to severe (and destructive) thermal degradation during operation' as a result of the propellers being constrained during low speed operations. Testing of the relays revealed that the high stop withdrawal relay for the right propeller functioned intermittently. All three crew members escaped uninjured.
Probable cause:
Occurrence #1: airframe/component/system failure/malfunction
Phase of operation: maneuvering
Findings
1. (c) procedures/directives - not followed - pilot in command
2. (f) inattentive - pilot in command
3. (c) powerplant controls - improper use of - pilot in command
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Occurrence #2: loss of engine power (total) - mech failure/malf
Phase of operation: descent - emergency
Findings
4. Turbine assembly - overtemperature
5. Emergency procedure - attempted - pilot in command
6. Propeller system/accessories, feathering system - engaged
7. Propeller feathering - performed - pilot in command
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Occurrence #3: forced landing
Phase of operation: descent - emergency
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Occurrence #4: gear not extended
Phase of operation: landing - flare/touchdown
Findings
8. Terrain condition - open field
9. (c) wheels up landing - intentional - pilot in command
10. Terrain condition - rough/uneven
Final Report:
N906TC.pdf89.22 KB