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Accidents · NTSB WPR15FA215 · Final report

Piper PA 22-160 accident near Twin Sisters Mtn, Washington, July 11, 2015

On July 11, 2015 at about 2:45 pm local time, a 1959 Piper PA 22-160, registered N9712D, was destroyed in an accident during enroute (cruise) near Twin Sisters Mtn, Washington. It was a personal flight under general aviation rules (Part 91). 2 people were killed. The weather was visual conditions (good weather).

The NTSB's probable cause their words, unchanged

The noninstrument-rated pilot's continued visual flight into instrument meteorological conditions, which resulted in controlled flight into mountainous terrain.

Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.

What the record shows

Date
July 11, 2015 · about 2:45 pm local time
Place
Twin Sisters Mtn, Washington · map
Type
Accident
Injuries
2 people were killed.
Weather
visual conditions (good weather)
Aircraft
Piper PA 22-160, built 1959 · all PA 22-160s on the register
Registration
N9712D · no longer on the register · serial 22-6624
Damage
Destroyed
Flight
Personal flight · general aviation rules (Part 91)

The NTSB's narrative final · quoted from the NTSB record

The noninstrument-rated private pilot was making a cross-country flight over mountainous terrain. Radar data showed the airplane flying in a northwesterly direction and climbing to an altitude of about 10,500 ft mean sea level (msl). About 38 minutes into the flight, the airplane's altitude started to decrease as it continued in a northwesterly direction, and, 6 minutes later, its altitude was 7,500 ft msl. The last radar return occurred 1 minute later at an altitude of 6,000 ft msl. The wreckage was located at the 6,000-ft level of a mountain ridgeline in the vicinity of the final radar return. Photographs of the wreckage revealed that the damage to the airplane was consistent with controlled flight into the terrain. The wreckage was not recovered from the accident site, and no follow-up examination was accomplished. Weather radar imagery indicated that rain showers moved into the area from the south-southeast as the airplane approached the accident site. These showers extended from about 19,000 ft msl down to ground level. Although no direct weather observations of the accident location were available, the airplane's descent as it approached the site is consistent with an attempt by the pilot to maintain visual meteorological conditions while operating amidst rain and clouds that likely obscured the terrain.

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

  1. VFR encounter with IMC during enroute (cruise)
  2. Controlled flight into terrain or object (CFIT) during enroute (cruise) defining event

The NTSB's findings

  • cause Personnel issues › Action/decision › Info processing/decision › Decision making/judgment › Pilot
  • cause Environmental issues › Physical environment › Terrain › Mountainous/hilly terrain › Contributed to outcome
  • cause Environmental issues › Conditions/weather/phenomena › Ceiling/visibility/precip › Below VFR minima › Effect on personnel

Pilot

  • Certificate: private
  • Ratings: single-engine land
  • Flight time: 440 hours in all
  • Medical certificate: Class 3 (with waivers/limitations)
  • Seat: left
  • Injury: fatal

Passenger

  • Seat: rgt
  • Injury: fatal

The aircraft

  • Airframe total time: 2,400 hours
  • Last inspection: annual inspection, June 16, 2015
  • Maximum gross weight: 2,000 lb
  • Seats: 4
  • Landing gear: fixed
  • Engine: Lycoming O-320 SERIES (piston); 0 hours total

The flight

  • Departed from: K6S9 Stehekin WA at 2:00 pm
  • Destination: KORS Eastsound WA
  • Flight plan: none

Weather at the time

  • Light: daylight
  • Wind: from 135° at 5 knots
  • Visibility: 10 statute miles
  • Sky: broken clouds at 3,800 ft
  • Temperature: 63°F (17°C), dew point 57°F (14°C)
  • Altimeter: 29.87 inHg
  • Observation at 2:53 pm from KBLI, 23 miles away

Injuries

FatalSeriousMinorNone
Flight crew1
Passengers1

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.