Boeing 737-7H4 incident near Birmingham, Alabama, July 7, 1998
On July 7, 1998 at about 11:40 am local time, a Boeing 737-7H4, registered N701GS, suffered minor damage in an incident near Birmingham, Alabama. It was a flight of an unrecorded kind under scheduled airline rules (Part 121). No one was hurt; 96 people were on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The improper electronic control unit software logic that permitted the electronic control unit to lock on a failed hydromechanical resolver, which failed due to damage to a wire that was incurred during the manufacturing process, resulting in an uncommanded and sudden increase in fuel flow to the engine that damaged the turbine and caused the engine to lose power.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- July 7, 1998 · about 11:40 am local time
- Place
- Birmingham, Alabama · map
- Type
- Incident
- Injuries
- No one was hurt; 96 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Boeing 737-7H4 · all 737-7H4s on the register
- Registration
- N701GS · no longer on the register · serial 27836
- Damage
- Minor damage
- Flight
- Flight of an unrecorded kind · scheduled airline rules (Part 121)
The NTSB's narrative final · quoted from the NTSB record
The flight data recorder showed that as the flight descended through 2,875 feet pressure altitude on approach to land, the no. 2 engine fuel flow increased followed by the EGT. The engine N1 speed was at 25.6 percent and decreased to 12.8 percent. Engine cutoff was performed 74 seconds after fuel flow increase began. An uneventful landing was made. Examination showed a broken wire in the no. 2 engine electronic engine control, hydromechanical unit, fuel metering valve resolver Channel B. The broken wire was due to damage that was incurred during the manufacturing process and caused unstable Channel B sine out voltage when the resolver was heated above 160 degrees Fahrenheit. The fuel control computer software locked on Channel B, disabled Channel A, and due to the unstable sine out voltage, commanded the fuel metering valve to go to a full open position. The large increase in fuel flow with the engine at idle speed resulted in the engine core stalling and heat damage to the low pressure turbine.
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; single-engine land; instrument: airplane; rotorcraft: glider; rotorcraft: helicopter
- Flight time: 15,000 hours in all; 9,745 in this make and model; 233 in the last 90 days
- Medical certificate: Class 1 (valid medical--no waivers/lim.)
- Seat: left
The aircraft
- Airframe total time: 1,754 hours
- Last inspection: continuous airworthiness programme, July 7, 1998; 1 hours since
- Landing gear: retractable
- Engine: Cfm CFM56-7B (turbofan); 0 hours total
The flight
- Departed from: TPA Tampa FL at 10:49 am
- Destination: BHM
- Flight plan: IFR
- Runway 0
Weather at the time
- Light: daylight
- Visibility: 5 statute miles
- Sky: scat at 30,000 ft
- Temperature: 81°F (27°C), dew point 75°F (24°C)
- Altimeter: 30.00 inHg
- Observation at 11:52 am from BHM, 20 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 5 | |||
| Passengers | 91 |
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.