BEECH 90B near Chickasha, OK — 2011-04-11
- Date
- 2011-04-11
- Location
- Chickasha, OK, USA
- Airport
- CHK
- Aircraft
- BEECH 90B
- Registration
- N37OU
- Category
- Airplane
- Highest injury
- None
- Fatalities
- 0
Probable cause
The mechanic's improper installation of the aileron.
NTSB narrative
The certified flight instructor (CFI) reported that the airplane was on a downwind leg for landing when a pilot-rated passenger who was sitting in the cabin told him that the right aileron was partially separated from the airplane. The CFI took control of the airplane and landed it uneventfully. The post incident inspection of the airplane revealed that the two inboard aileron hinges were separated from the airframe. The screws (8 screws, 4 upper, 4 lower) which attached the aileron to the aileron hinge points were seated in the aileron skin, but did not screw into the corresponding nut plates on the aileron hinge points. The aileron was not damaged so a mechanic attached the aileron properly to the aileron hinge points and the airplane was returned to service. Maintenance records indicated that the airplane had undergone a phase inspection 10 days prior to the incident. During the phase inspection, the right aileron was removed to repair some light surface corrosion and was reinstalled on the airplane. The incident occurred 5.3 hours after the phase inspection was performed. Eight years prior to the accident, the aircraft manufacturer issued a communique which stated that their technical support department had received reports that during aileron installation, screws missed the nut plates on the aileron hinge points. It stated that this condition can go unnoticed.
Analysis
- Primary failure mode
- Mechanical failure
- First missed decision gate
- Proper installation of aileron hinges during maintenance could have prevented the failure.
NTSB coding
- Aircraft structural failure · Approach-VFR pattern downwind
Evidence available
- Photos
- 9 docket documents
Docket documents9
- Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1form
- Chief Flight Instructor Statementinterview
- Instructor Pilot Statementinterview
- Pilot Statementinterview
- Illustration of Aileronother
- King Air Aileron Installation Instructionsother
- King Air Communique 2003-03other
- Post Accident Maintenance Write-upother
- Photo Log (5) Photos Embeddedphotos