# NTSB SEA02LA059: Potts KitFox, N139SP, Shoup, ID, March 25, 2002 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: March 25, 2002, 09:00 local (16:00 UTC) - Place: Shoup, ID - Coordinates: 45.389678, -114.420181 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=45.3897&lon=-114.4202&mi=10 - Phase of flight: [Takeoff](https://openairdocs.org/ntsb-phases/300) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report September 9, 2002 - Report: Approved by Office Director - Parties: Boise FSDO - NTSB case key (mKey): 54400 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA02LA059 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/54400/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=54400 - Page: https://openairdocs.org/ntsb/SEA02LA059 ## Probable cause The pilot’s failure to maintain a speed above stall speed, and the resulting inadvertent stall/mush. Factors include the pilot's failure to abort the takeoff when he realized the aircraft's performance was not as expected, his decision to attempt a takeoff after experiencing an unacceptable rpm drop on each magneto during the engine run-up check, and the failure of the magnetos to maintain an acceptable engine rpm when operated individually. ## Analysis The pilot attempted a takeoff in an experimental aircraft who's engine/propeller combination had not produced the expected rpm since the pilot/builder changed the engine but did not change the propeller. Prior to the attempted takeoff, the pilot experienced a 250 rpm drop on each magneto during the engine run-up check. During the takeoff roll, the pilot realized that the aircraft was not performing as desired, and momentarily thought about aborting, but instead continued. After liftoff, the pilot was unable to get the aircraft to climb, and as he was making a turn over a river situated off the departure end of the runway, the aircraft stall/mushed, and one wing drug in the water. Immediately after the wing contacted the water, the aircraft cartwheeled along the river's surface, coming to rest upright in about 30 inches of water. ## Factual narrative On March 25, 2002, approximately 0900 mountain standard time, an experimental Potts KitFox, N139SP, impacted the waters of the Salmon River during a takeoff attempt from a private airstrip near Shoup, Idaho. The commercial pilot, who was the sole occupant, was not injured, but the aircraft, which was owned and operated by the pilot, sustained substantial damage. The Title 14, CFR Part 91 personal pleasure flight, which was being operated in visual meteorological conditions, was departing for Challis, Idaho, at the time of the accident. No flight plan had been filed. According to the pilot, who was departing his 1,000 foot private strip, about the time the aircraft got half way down the runway, he realized the engine was not producing as much power as he expected. He momentarily thought about aborting the takeoff, but instead elected to continue. Although he was able to get the airplane in the air, he was unable to get it to climb. After crossing the departure end of the runway, and only being able to keep the aircraft a few feet off the ground, he attempted to make a shallow turn in order to fly down the Salmon River. During the turn, he was unable to maintain sufficient airspeed, and the aircraft began to stall/mush. As it started to drop, one wing made contact with the river. Immediately after the wing drug in the water, the aircraft cartwheeled along the river's surface, and it came to rest upright in about 30 inches of water. According to the pilot, when he changed the experimental aircraft's powerplant to a new Franklin engine from a Rotax engine, he did not change the propeller. Although he had shortened the blades of the propeller approximately one inch, and sent the carburetor to the factory for inspection and service, he was never able to get the engine to run at the expected 2,800 rpm. Although the engine would not reach the expected rpm, the pilot reported that it seemed to run smooth and steady. Just prior to the subject takeoff, the pilot did a magneto check at 1,800 rpm, and as he selected each magneto individually, the engine slowed by 250 rpm. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - In flight collision with terrain/water, takeoff - airspeed(vs) - not maintained, pilot in command (cause) - stall/mush - inadvertent, pilot in command (cause) - aborted takeoff - not performed, pilot in command (contributing factor) - planning/decision - improper, pilot in command (contributing factor) - ignition system,magneto - undetermined (contributing factor) ## Aircraft - Registration: [N139SP](https://openairdocs.org/deregistered/N139SP-2012-10-23), registration cancelled 2012-10-23, S/N S9501-0089, built 1998 (OpenAirDocs) - Reported make and model: Potts KitFox - Registry model: [Potts Stanley S-5 TD OUTBACK](https://openairdocs.org/model/potts-stanley-s-5-td-outback) (registry code 056066U) (OpenAirDocs) - Registry engine: [Franklin 4A235 series](https://openairdocs.org/engine/franklin-4a235-series) (registry code 27011, reciprocating) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: 59501-0089 - Airframe hours: 28 - Engines: Franklin PZLF-4A235831 116 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Registered owner: Stanley V. Potts - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Condition, March 1, 2002, 3 hours before - Departed: Shoup, ID - Destination: U15, Challis, ID - Airport: Colson Creek, runway 25, 1,000 × 60 ft, dirt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 67; injuries: none; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 3, valid medical--no waivers/lim.; last flight review July 1, 2000; seat: left; flight hours: 1,969 total, 28 in this make and model, 3 in the last 90 days, 3 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 20 statute miles - Lowest ceiling: none - Temperature: 39 °F ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 20020325005319A](https://openairdocs.org/incident/20020325005319A), Mar 25, 2002: Amtr S5TDOUTBACK, Shoup, ID, No damage. (-23) On March 25, 2002 at approximately 1000 MST a kit fox experimental aircraft was substantially damaged on takeoff from a private strip in Shoup, Idaho.… ## Docket (1 files) The files NTSB released with the investigation on August 15, 2002, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=54400. 3.1 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 3.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40394858&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.