Mcdonnell Douglas DC-9-51 incident near Chicago, Illinois, October 14, 1999
On October 14, 1999 at about 6:55 pm local time, a Mcdonnell Douglas DC-9-51, registered N766NC, was involved in an incident near Chicago, Illinois (Chicago Midway Airport). It was a flight of an unrecorded kind under scheduled airline rules (Part 121). No one was hurt; 105 people were on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The landing gear's wheel separation due to the improper installation of the wheel by company maintenance personnel using incomplete maintenance steps, and the maintenance steps not listed in the manufacturer's manual. Factors were the airport perimeter wall and the vehicles.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- October 14, 1999 · about 6:55 pm local time
- Place
- Chicago, Illinois · Chicago Midway Airport · map
- Type
- Incident
- Injuries
- No one was hurt; 105 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Mcdonnell Douglas DC-9-51 · all DC-9-51s on the register
- Registration
- N766NC · no longer on the register · serial 47739
- Damage
- Not recorded
- Flight
- Flight of an unrecorded kind · scheduled airline rules (Part 121)
The NTSB's narrative final · quoted from the NTSB record
A DC-9-51 sustained a left outboard main (#1 main) wheel and tire assembly separation on takeoff. That wheel impacted and dislodged the airport's perimeter wall and impacted a vehicle on a nearby road. The wall panels impacted another vehicle. No injuries were reported. The flight landed without incident at its intended destination. That tire assembly was found pressurized and its hubcap was found intact. Its axle nut was found intact under the hubcap. The interior portion of the #1 axle was examined and its internal threads were found intact. The anti-skid transducer adapter was found loosened inside the axle's threads and backed out 4 1/2 turns. A gap was designed to exist between the adapter and the nut. The axle nut was found to contact the adapter when the adapter was backed out to the position as found. The tire was changed on October 1, 1999. The mechanics installed the wheel in accordance with manual 32-40-1. That manual was reviewed and its steps did not caution mechanics to check for the proper depth of the adapter. DC-9-20 through 40 series airplane's anti-skid transducer assemblies were initially secured in position through safety wire. Service Bulletin (SB) 32-111 was issued to incorporate a set screw method in lieu of safety wiring the anti-skid transducer in place. This airplane's SB 32-111 modification was incorporated prior to its delivery to the airline. Subsequent to the incident, the manufacturer issued temporary service bulletins to the affected airplane's 32-40-01 maintenance manuals, cautioning mechanics to check the depth dimension of the transducer adapter with reference to the applicable technical data.
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
Pilot
- Certificate: airline transport pilot, flight engineer
- Ratings: multi-engine land; instrument: airplane
- Flight time: 6,573 hours in all; 3,259 in this make and model; 207 in the last 90 days
- Medical certificate: Class 1 (valid medical--w/ waivers/lim.)
- Seat: left
The aircraft
- Airframe total time: 56,338 hours
- Last inspection: continuous airworthiness programme, December 24, 1998; 1,891 hours since
- Maximum gross weight: 110,000 lb
- Seats: 132
- Landing gear: retractable
- Engine: P&W JT8D17H (turbojet); 0 hours total
The flight
- Departed from: MDW at 6:55 pm
- Destination: DTW Detroit MI
- Flight plan: IFR
- Runway 22L, 6,446 ft by 150 ft
- A second pilot was aboard
Weather at the time
- Light: daylight
- Wind: from 180° at 8 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 57°F (14°C), dew point 36°F (2°C)
- Altimeter: 30.00 inHg
- Observation at 6:53 pm from MDW
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 7 | |||
| Passengers | 98 |
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.