ASN Wikibase Occurrence # 186634
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| Date: | Thursday 21 April 2016 |
| Time: | 14:45 |
| Type: |  Mooney M20K 231 |
| Owner/operator: | Private |
| Registration: | N97119 |
| MSN: | 25-0503 |
| Year of manufacture: | 1981 |
| Total airframe hrs: | 1926 hours |
| Engine model: | Continental TSIO-360-LB |
| Fatalities: | Fatalities: 1 / Occupants: 3 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Woodland State Airport (W27), Woodland, WA -
 United States of America
|
| Phase: | Take off |
| Nature: | Private |
| Departure airport: | Woodland, WA (W27) |
| Renton Airport, WA (RNT/KRNT) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The pilot and two passengers boarded the airplane for a personal cross-country flight. After a normal engine run-up, the pilot began the takeoff roll on the 1,953-ft-long runway. According to the pilot, the airplane lifted off after a ground roll of about 1,250 ft, climbed to about 35 ft above ground level, but then stopped accelerating. The pilot then lowered the nose and discovered that the airplane was just above the ground and seconds from impacting a berm. However, video of the takeoff showed that the airplane became airborne after a ground roll of about 1,933-ft, about 20 ft from the end of the runway. Further, according to the witness who took the video, the airplane attained a maximum altitude of only about 4 ft before it touched down in the grass beyond the runway end. The airplane impacted the airport's perimeter fence located about 375 ft from the end of the runway and then collided with the 9-ft-tall berm.
A sound spectrum analysis of the video's audio channel showed that the propeller rpm was about 2,430 during takeoff, which was about 270 rpm below the expected maximum rpm of 2,700. Examination of the propeller governor showed that the unit was set to a maximum rpm of about 2,600, which was about 100 rpm below the manufacturer's specified setting. In addition, during engine test cell runs with a fixed-pitch club propeller, the maximum engine rpm was increased 100 rpm, from 2,640 to 2,740, by retiming the magnetos from an improper setting to the manufacturer's specified setting. Regardless, the propeller governor would have inhibited the engine from reaching rated power, thus it is likely that the propeller governor resulted in a takeoff rpm below maximum rpm.
The pilot reported that before departure, he calculated that the airplane's gross weight was about 2,864 pounds (lbs) and the takeoff ground roll would be about 1,250 ft. Postaccident calculations revealed that the airplane's gross weight was about 2,978 lbs, which exceeded the airplane's maximum gross weight by 78 lbs. The airplane's zero-wind ground roll at its maximum gross weight of 2,900 lbs was about 1,350 ft, and may have been longer due to the higher gross weight. Although the pilot's calculations indicated a safe takeoff was possible, the airplane did not perform as expected, likely due to the engine not achieving maximum rpm and the pilot's exceedance of the airplane's maximum gross weight. The pilot should have been sensitive to the short runway length and closely monitored the airplane's performance. If the pilot had recognized promptly that the airplane was not performing as expected, given the distance from the runway end to the fence and the berm that the airplane impacted, adequate distance would likely have been available to safely abort the takeoff. Additionally, if the pilot had designated a go/no-go runway liftoff point, this would have helped him detect the performance deficiency. However, the pilot did not recognize that the airplane was not performing as expected until the airplane was near the runway end and the impact with the berm could not be avoided.
Probable Cause: The pilot's delay in recognizing that the airplane was not performing as expected and aborting the takeoff, which resulted in collision with a berm beyond the end of the runway. Contributing to the accident were the pilot's exceedance of the airplane's gross weight and the underperformance of the engine due to governor setting and magneto timing deficiencies. Contributing to the severity of the rear passenger's injuries was his decision to forego use of his shoulder harness and/or the absence of head rests.
Accident investigation:
 |
|
Sources:
NTSB
https://www.youtube.com/watch?v=NvjuglBoWO0
Location
Images:
Photo: NTSB
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 22-Apr-2016 01:41 | Geno | Added |
| 22-Apr-2016 01:47 | Geno | Updated [Phase, Source] |
| 22-Apr-2016 15:55 | Geno | Updated [Source, Narrative] |
| 15-May-2016 07:16 | Anon. | Updated [Phase, Nature] |
| 21-Dec-2016 19:30 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 22-Feb-2019 20:19 | ASN Update Bot | Updated [Operator, Departure airport, Destination airport, Source, Narrative, Accident report, ] |
| 22-Feb-2019 20:22 | harro | Updated [Destination airport, Narrative, Photo] |
| 22-Feb-2019 20:27 | harro | Updated [Narrative] |
| 17-Oct-2022 20:09 | RobertMB | Updated [Destination airport, Source] |
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