Sikorsky S-58T accident near Milwaukee, Wisconsin, April 11, 1989
On April 11, 1989 at about 3:31 pm local time, a Sikorsky S-58T (helicopter), registered N4247U, was substantially damaged in an accident near Milwaukee, Wisconsin. It was an other work-use flight under external-load helicopter rules (Part 133). 1 person was seriously injured. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
DISCONNECT OF THE TAILROTOR DRIVE SHAFT COUPLING.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- April 11, 1989 · about 3:31 pm local time
- Place
- Milwaukee, Wisconsin · map
- Type
- Accident
- Injuries
- 1 person was seriously injured.
- Weather
- visual conditions (good weather)
- Aircraft
- Sikorsky S-58T · all S-58Ts on the register
- Registration
- N4247U · registry record · serial 58-1537
- Damage
- Substantial damage
- Flight
- Other work-use flight · external-load helicopter rules (Part 133)
The NTSB's narrative final · quoted from the NTSB record
THE ACCIDENT HELICOPTER DESCENDED INTO SLOPING TERRAIN AND ROLLED OVER WHILE PERFORMING EXTERNAL LOAD OPERATIONS. THE HELICOPTER HAD JUST PICKED UP A LOAD AND WAS MOVING LATERALLY WHEN IT SUSTAINED A LOSS OF ANTI-TORQUE CONTROL AND THE FUSELAGE STARTED AN UNCOMMANDED AND UNCONTROLLED ROTATION TO THE RIGHT. THE PIC WAS ABLE TO JETTISON HIS EXTERNAL LOAD INTO A CLEAR AREA AND MOVE THE HELICOPTER AWAY FROM OBSTRUCTIONS BEFORE INITIATING AN OUT OF GROUND EFFECT HOVERING AUTOROTATION.
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: commercial pilot
- Ratings: instructor: helicopter; instrument: helicopter; rotorcraft: helicopter
- Flight time: 9,562 hours in all; 3,400 in this make and model; 99 in the last 90 days; 48 in the last 30 days; 8,275 as pilot in command; 2,887 on instruments
- Medical certificate: Class 2 (valid medical--no waivers/lim.)
- Seat: rgt
The aircraft
- Airframe total time: 4,326 hours
- Last inspection: continuous airworthiness programme, March 15, 1989; 17 hours since
- Maximum gross weight: 13,000 lb
- Seats: 3
- Landing gear: fixed
- Engine: P&W PT6T-6 (turboshaft); 0 hours total
The flight
- Departed from: MKE Milwaukee WI at 3:10 pm
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 210° at 10 knots, gusting 20
- Visibility: 7 statute miles
- Sky: overcast at 25,000 ft; not recorded
- Temperature: 43°F (6°C), dew point 18°F (-8°C)
- Altimeter: 30.00 inHg
- Observation at 3:52 pm from MKE, 3 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 |
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.
Other NTSB records under N4247U the same tail number, which may have belonged to a different aircraft at the time
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.