Beech 90B incident near Chickasha, Oklahoma, April 11, 2011
On April 11, 2011 at about 3:15 pm local time, a Beech 90B, registered N37OU, suffered minor damage in an incident during approach (VFR pattern downwind) near Chickasha, Oklahoma (Chickasha Municipal Airport). It was an instructional flight under general aviation rules (Part 91). No one was hurt; 4 people were on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The mechanic's improper installation of the aileron.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- April 11, 2011 · about 3:15 pm local time
- Place
- Chickasha, Oklahoma · Chickasha Municipal Airport · map
- Type
- Incident
- Injuries
- No one was hurt; 4 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Beech 90B
- Registration
- N37OU · no longer on the register · serial LJ-1428
- Damage
- Minor damage
- Flight
- Instructional flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
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.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
What happened, in order
- Aircraft structural failure during approach (VFR pattern downwind) defining event
The NTSB's findings
- cause Aircraft › Aircraft structures › Wing structure › Ailerons › Incorrect service/maintenance
- cause Aircraft › Aircraft structures › Wing structure › Attach fittings (on wing) › Incorrect service/maintenance
- cause Personnel issues › Action/decision › Action › Incorrect action performance › Maintenance personnel
- Aircraft › Aircraft structures › Wing structure › Ailerons › Related maintenance info
Pilot
- Certificate: commercial pilot
- Ratings: multi-engine land; single-engine land; instrument: airplane
- Flight time: 209 hours in all; 1 in this make and model; 1 in the last 90 days; 1 in the last 30 days; 163 as pilot in command
- Last flight review: December 8, 2010
- Medical certificate: Class 3 (with waivers/limitations)
- Seat: left
- Injury: no injuries
Flight instructor
- Certificate: airline transport pilot, flight instructor
- Ratings: multi-engine land; single-engine land; instructor: airplane multi-engine; instructor: airplane single-engine; instrument: airplane
- Flight time: 4,152 hours in all; 679 in this make and model; 32 in the last 90 days; 22 in the last 30 days; 4,083 as pilot in command; 3,598 on instruments
- Last flight review: February 17, 2010
- Medical certificate: Class 1 (without waivers/limitations)
- Seat: rgt
- Injury: no injuries
The aircraft
- Airframe total time: 2,789 hours
- Last inspection: approved inspection programme, April 1, 2011; 5 hours since
- Maximum gross weight: 10,100 lb
- Seats: 8
- Landing gear: retractable
- Engine: P&Wc PT-6A-21 (turboprop); 0 hours total
- Operator: University Of Oklahoma, Dept Of Aviation
The flight
- Departed from: OUN Norman OK at 2:15 pm
- Destination: OUN Norman OK
- Flight plan: none
- Runway 35, 5,101 ft by 100 ft
- A second pilot was aboard
Weather at the time
- Light: daylight
- Wind: from 340° at 19 knots, gusting 29
- Visibility: 10 statute miles
- Temperature: 72°F (22°C), dew point 45°F (7°C)
- Altimeter: 30.06 inHg
- Observation at 3:00 pm from CHK
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 2 | |||
| Passengers | 2 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.