Aerial Survey Turned Deadly: N690LS's Stall and Spin Near Hiles, Wisconsin

A Rockwell 690B Turbo Commander conducting a routine forest-survey mission for the Wisconsin Department of Natural Resources stalled and spun into the woods of the Chequamegon-Nicolet National Forest, killing everyone aboard.

A Survey Flight at Altitude

N690LS departed Rhinelander-Oneida County Airport at about 8:50 a.m. on September 28, 2021, carrying the pilot and two company employees. The mission was to capture aerial imagery of forest vegetation for the state's Department of Natural Resources — the kind of low-workload, methodical flying that survey work usually is. About eight minutes after departure, the aircraft leveled off near 16,100 feet, its groundspeed peaking around 209 knots as it settled into the survey run.

Airspeed Bled Away in Level Flight

Over the next two minutes, without any recorded maneuvering that would explain it, the aircraft's groundspeed fell from roughly 209 knots to about 93 knots while it remained in level flight. That is a description of an airplane running out of the energy it needs to keep flying — airspeed decaying toward stall while the pilot, for reasons the wreckage alone couldn't explain, did not add power or lower the nose to arrest it.

"We're in a Spin"

As the aircraft's margin above stall speed disappeared, air traffic control recorded the crew transmitting "mayday, mayday, mayday," followed by "we're in a spin." A Turbo Commander departing controlled flight at 15,000-plus feet gives a crew altitude to work with, but recovering a large twin from a fully developed spin requires prompt, correct control inputs — and the transmissions suggest the crew recognized the spin but the aircraft did not recover.

Impact in the National Forest

N690LS came down in wooded terrain near Hiles, Wisconsin, inside the Chequamegon-Nicolet National Forest. The wreckage was located around 11 a.m. near the Franklin Lake Campground. All three occupants — the pilot and two survey personnel — were killed.

What the Investigation Found

The NTSB's final report attributed the accident to the pilot's failure to maintain adequate airspeed, which allowed the aircraft to exceed its critical angle of attack and enter an inadvertent stall and spin. The board's finding does not identify a mechanical cause: this was airspeed management during level survey flight, not a system failure. The specific reason the crew allowed the speed to decay unnoticed for nearly two minutes at altitude — workload, distraction with survey equipment, or something else — is not established in the public record.

This reconstruction was researched from official investigation records where they exist, the original air traffic control recording, and contemporary reporting. The aircraft movement, timeline and written account were assembled independently by Flight Follower. Where an investigation is open or no probable cause has been published, the account says so rather than offering one.

Timeline

Sources and investigation material

• https://www.ntsb.gov/investigations/AccidentReports/Reports/AIR2302.pdf

Accident Facts

Sources

• NTSB docket CEN21FA459 (probable cause quoted verbatim)
• Wausau Pilot & Review, "Plane crashes near Three Lakes in Northern Wis., 3 on board"
• Kathryn's Report, "Rockwell 690B Turbo Commander, N690LS" (Sep 28, 2021)