- Date
- June 20, 2021, 12:10 local (19:10 UTC)
- Place
- Twisp, WA
- Injuries
- 1 uninjured
- Damage
- Substantial damage
- Phase of flight
- Landing
- Aircraft
- N6917ZPiper PA-25-235
- Defining event
- Landing: Flight control sys malf/fail
- Weather
- Visual (VMC) · Day
- Status
- Completed
- Report
- Approved by Office Director
- Investigation class
- Class 4 - Basic report with no Prelim publish
- NTSB office
- Western Pacific Region
- Parties
- FAA
- FAA report
- 20210620007919A
- Case key
- 103319
From the NTSB’s public API. By law, NTSB reports can’t be used as evidence in lawsuits over the accident.
On this page
Probable cause
An in-flight separation of the control stick from the torque tube assembly, which resulted in a loss of directional control during the landing roll and subsequent on-ground collision.
Findings · 3
NTSB’s coded findings. Those marked are part of the probable cause; the rest are factors or other findings. Under each, the cases with the same finding.
Sequence of events
The events NTSB coded, in order, by phase of flight. The defining event is the one that best describes the accident. Under each, the cases with the same event anywhere in their sequence.
Analysis
The pilot in the tailwheel-equipped airplane reported that, during the sixth flight of a glider tow operation, the control stick felt as though it had “some play” with regard to the ailerons. The control stick moved about four inches laterally before a corresponding movement of the ailerons could be observed. He landed the airplane, performed a flight control check and noticed a “little slack” between the control stick inputs and subsequent aileron movement. He determined that the control stick felt secure and took off on his seventh tow flight. During the climb out, the response to his control stick inputs diminished. The airplane encountered turbulence and the control stick separated from the torque tube assembly. He maintained control of the airplane by using trim, rudder control and throttle variations. The airplane subsequently landed on the grass surface to the right of the runway. During a firm landing, the airplane veered right, and the right wing collided with a berm. The airplane sustained substantial damage to the leading-edge of the right wing. A subsequent examination of the airplane’s flight controls, revealed that the bolt which secured the control stick to the torque tube assembly had backed out. The castellated nut and cotter pin which secured the bolt were not located.
Aircraft
- Registration
- N6917Z
- Reported as
- Piper PA-25-235
- Category
- Airplane
- Serial number
- 25-2660
- Built
- 1964
- Airframe hours
- 7,278.8
- Engine
- Lycoming O-540-B2C5, 235 horsepower, reciprocating
- Damage
- Substantial damage
- Flight
- Glider tow · Part 91
- Operator
- Evergreen Soaring Inc
- Registered owner
- Evergreen Soaring Inc
- Airworthiness certificate
- Standard, Normal
- Last inspection
- Annual · March 11, 2021
- Destination
- Same as departure
- Airport
- 2S0 · Twisp Muni, runway 10/28, 2,701 × 60 ft, grass/turf
- Equipment
- None
Matched to the registry by N-number and the event date; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.
Flight crew
As NTSB recorded them. NTSB leaves out names.
- Role
- Pilot
- Age
- 79
- Injuries
- Minor
- Certificate
- Airline transport
- Airplane ratings
- Single-engine land, Multi-engine land
- Instrument ratings
- Airplane
- Medical
- With waivers/limitations
- Last flight review
- May 19, 2021
- Seat
- Single
- Flight hours
- 15,077 total · 516.9 in this make and model · 34.5 in the last 90 days · 27 in the last 30 days · 2.3 in the last 24 hours
Weather
- Conditions
- Visual (VMC) · Day
- Wind
- 20° at 10 knots, gusting 18
- Visibility
- 10 statute miles
- Lowest ceiling
- None
- Temperature
- 81 °F, dew point 46 °F
- Altimeter
- 30.08 inHg
- Observed at
- KOMK, 24 nm away
- METAR
- METAR KOMK 201853Z AUTO 02010G18KT 10SM CLR 27/08 A3008 RMK AO2 SLP177 T02720083=
Docket · 3
The files NTSB released with the investigation on November 12, 2021, on NTSB’s docket system: statements, records, photos and specialists’ reports. 4.3 MB in all.
FAA reports on this event · 1
The FAA’s own accident and incident reports, matched to the aircraft by N-number and date.