Six people, five adults and a child, died when a single-engine Piper PA-46 crashed into woodland near Mirror Lake State Park in the Town of Dellona, Wisconsin, on the evening of Tuesday 13 October12. The aircraft was on a return trip from Kenosha to Menomonie1. According to preliminary information from the National Transportation Safety Board, the pilot had reported icing at 24,000 feet and asked to descend before communications and tracking data were lost13. The NTSB is leading the investigation and has not determined a cause134.

What is known about the flight

The Sauk County Dispatch Center received multiple reports of a downed aircraft near Park Lane in Dellona at approximately 9:31 pm local time1. Responders found the wreckage in a densely wooded area north of Park Lane and west of Herwig Road and searched for survivors; all six occupants were found dead at the scene13. No one on the ground was hurt and no buildings were damaged1. The site is about 10 miles west of Wisconsin Dells6.

The FAA identified the aircraft as a Piper PA-46, and AP described it as a six-seat, single-engine aeroplane132. AVweb, citing Flightradar24, identified it as the PA-46-350P Malibu Mirage registered N931TT10, and the FAA registry lists that registration as a PA-46-350P built in 20089. AVweb, citing flight-tracking information reported by local media, said it departed Kenosha at approximately 8:43 pm10. Sauk County Sheriff Chip Meister said it was not a commercial plane and that it remained unclear who owned it, Fox News reported7. The names of those on board have not been released1.

The open ADS-B data archived by adsb.lol for N931TT, the registration reported by AVweb, show a track from Kenosha that ends west of Wisconsin Dells shortly before 9:30 pm local time12.

What the NTSB has said so far

The NTSB said the aeroplane was flying at 24,000 feet when the pilot reported icing and requested to descend13; AP, reporting the same statement, said the pilot told a controller about icing on the wings5. "Air traffic control approved the descent, and the aircraft entered a right descending turn that increased in rate until communications and data tracking were lost," the agency said13. AP reported that rain was falling as a thunderstorm moved through the area2. The sheriff's office said investigators were working to learn the content of the transmissions with a nearby air traffic control tower and whether a weather event in the area played any role1. These are early facts, not findings, and they do not establish why the aircraft crashed.

How the investigation will proceed

NTSB investigators were expected at the site on Wednesday afternoon to document the scene and examine the aircraft, which will then be moved to a facility for further examination4. The agency said it will gather flight track data, air traffic control recordings, maintenance records and information on the pilot, and it asked anyone who witnessed the crash or has video of it to email witness@ntsb.gov4. It will not determine a cause during the on-scene investigation and will not identify the victims4. A preliminary report will be available within 30 days13, and a final report is expected in 12 to 24 months4.

That timetable matches the agency's general process, which runs from on-scene fact gathering through analysis and a probable cause determination to a final report and, where warranted, safety recommendations; the NTSB says it generally tries to complete an investigation within 12 to 24 months14. Under federal rules, these investigations are fact-finding proceedings with no adverse parties and are "not conducted for the purpose of determining the rights, liabilities, or blame of any person or entity"15.

Icing in context: what FAA guidance tells pilots

Whether ice played any part in this accident is for the NTSB to establish. As general background, the FAA's pilot guide to flight in icing conditions, Advisory Circular 91-74B, explains that ice significantly reduces an airfoil's maximum lift coefficient and that a wing stalls at a much lower angle of attack with ice than without16. "Even a thin layer of ice at the leading edge of a wing, especially if it is rough, can have a significant effect in increasing stall speed," the circular says16. The FAA makes the same point in its general material on in-flight icing: it can distort the flow of air over the wing, increase drag and adversely affect handling qualities, and an aeroplane may stall at much higher speeds and lower angles of attack than normal17.

This is general guidance for pilots, not a description of what happened over Wisconsin.

Frequently asked questions

What caused the Wisconsin PA-46 crash?

That is not known. The NTSB has released only preliminary information and will not determine a cause during the on-scene investigation4.

Who was on board?

Five adults and one child, all of whom died1. Their identities are being withheld1.

When will the NTSB publish its findings?

A preliminary report is due within 30 days, and a final report is expected in 12 to 24 months134.