WPR21LA238

NTSB accident investigation · Piper PA-25-235 · Twisp, WA · June 20, 2021

Accident · No injuriesClass 4 · LimitedFinal report
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.

Performance/control parameters: directional controlAircraft › Aircraft oper/perf/capability · Not attained/maintainedPiper PA-25-235: 3 casesAll aircraft: 3,958 casesProbable cause
Misc hardware: fastenersAircraft › Fluids/misc hardware · Not specifiedPiper PA-25-235: 1 caseAll aircraft: 58 casesProbable cause

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.