Rockwell International 690B accident near Hiles, Wisconsin, September 28, 2021
On September 28, 2021 at about 2:00 pm local time, a 1978 Rockwell International 690B, registered N690LS, was destroyed in an accident during enroute (cruise) near Hiles, Wisconsin. It was an aerial observation flight under general aviation rules (Part 91). 3 people were killed. The weather was visual conditions (good weather).
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The NTSB's probable cause their words, unchanged
The pilot’s failure to maintain adequate airspeed, which caused the airplane to exceed its critical angle of attack and enter an inadvertent stall and spin.
Source: NTSB aviation accident database, copy made October 4, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- September 28, 2021 · about 2:00 pm local time
- Place
- Hiles, Wisconsin · map
- Type
- Accident
- Injuries
- 3 people were killed.
- Weather
- visual conditions (good weather)
- Aircraft
- Rockwell International 690B, built 1978 · all 690Bs on the register
- Registration
- N690LS · no longer on the register · serial 11475
- Damage
- Destroyed
- Flight
- Aerial observation flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The company pilot and two employees had departed on an aerial imagery survey flight of forest vegetation. The airplane began to level off at an altitude of about 16,100 ft mean sea level (msl) and accelerated to a maximum recorded groundspeed of 209 knots. Less than 2 minutes later, the groundspeed decreased to about 93 knots, and the airplane descended about 500 ft while on a steady heading. The airplane subsequently entered a rapid descent and a right turn, and “mayday, mayday, mayday” and “we’re in a spin” transmissions were broadcast to air traffic control (ATC). A witness, who was located near the accident site, noticed the airplane nose down at high rate of speed and then saw the airplane spinning rapidly about its longitudinal axis. The airplane wreckage was located in remote wetlands and wooded terrain. Postaccident examination revealed that the airplane impacted the ground in a nose low vertical attitude and at high speed. All major components of the airplane were located at the accident site. Examination of the airframe, engines, and propellers revealed no preimpact mechanical malfunctions or failures that would have precluded normal operation. According to the aircraft performance study for this accident, when the airplane pitched down, the normal load factor decreased rapidly from about 1.6 to less than 1 G. A rapid decrease in normal load factor is consistent with a stall when the wing exceeds its critical angle of attack. At that point, the air flow becomes separated at the wing, and the wing can no longer generate the necessary lift. If the airplane is in uncoordinated flight at the stall, a spin can result. Thus, the pilot likely did not maintain adequate airspeed, causing the airplane to exceed its critical angle of attack and enter a stall and spin. An important but unknown factor before and during the initial stall was the behavior of the pilot regarding his flight control inputs, including his possible attempt to recover. The airplane’s Pilot Operating Handbook states that spins are not authorized and does not include a procedure for inadvertent spin recovery.
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
- Loss of control in flight during enroute (cruise) defining event
The NTSB's findings
- Personnel issues › Task performance › Use of equip/info › Aircraft control › Pilot
- Not determined › Not determined › (general) › (general) › Unknown/Not determined
- Aircraft › Aircraft oper/perf/capability › Performance/control parameters › Airspeed › Not attained/maintained
- Aircraft › Aircraft oper/perf/capability › Performance/control parameters › Angle of attack › Capability exceeded
Pilot
- Certificate: flight instructor, commercial pilot
- Ratings: multi-engine land; single-engine land; instructor: airplane single-engine; instructor: instrument airplane; instrument: airplane
- Flight time: 1,019 hours in all; 300 in this make and model
- Last flight review: February 5, 2021
- Medical certificate: Class 1 (without waivers/limitations)
- Seat: left
- Injury: fatal
The aircraft
- Airframe total time: 7,854 hours
- Last inspection: approved inspection programme, September 24, 2021
- Maximum gross weight: 10,375 lb
- Seats: 3
- Landing gear: retractable
- Engine 1: Air Research TPE331-10T-51 (turboprop); 10,876 hours total
- Engine 2: Air Research TPE331-10T-51 (turboprop); 10,247 hours total
- Operator: Surdex CORP
The flight
- Departed from: RHI Rhinelander WI at 1:50 pm
- A second pilot was aboard
Weather at the time
- Light: daylight
- Wind: from 160° at 4 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 50°F (10°C), dew point 50°F (10°C)
- Altimeter: 30.05 inHg
- Observation at 9:15 am from KEGV, 11 miles away
Weather report (METAR): KEGV 281415Z AUTO 16004KT 10SM CLR 10/10 A3005 RMK AO2 T01010101
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 | |||
| 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.
About this page
Everything above comes from the NTSB's public accident database: the narrative, probable cause and findings are the NTSB's own words, and the coded tables behind its report (pilot, aircraft, flight, weather, injuries, sequence of events) are written out in plain English. Pilots' ages, home towns and medical details are left out on purpose. The documents and photographs are the NTSB's docket, the folder of records gathered during the investigation, shown as the NTSB released them (the NTSB redacts some personal details first) and listed under the NTSB's own titles. This site's own text never names pilots, passengers or anyone else involved. A preliminary report describes what is known soon after the event and can change; the final report, with the probable cause, usually follows one to two years later and this page is refreshed when it does. Case number CEN21FA459.