20250811011519A

Accident · Substantial damage

FAA accident report · Dehavilland DHC-6-300 · San Clemente Is, CA · August 11, 2025

Date: August 11, 2025 · 11:30 local
Place: San Clemente Is, CA
Airport: San Clemente Island Nalf
Phase of flight: Landing: Approach
Operating rules: Air taxi and commuter (Part 135)
Operator: 3RAA
Damage: Substantial damage
Aircraft: N344CS
NTSB investigation: NTSBWPR25LA250
Reported as: Dehavilland DHC-6-300
Reported engine: Pratt & Whitney PT6A-34
People aboard: 18
Fatal injuries: 0
Other injuries: 0
Pilot’s certificate: Airline transport
Pilot’s flight hours: 5,125 total

N344CSRegistered now · Dehavilland DHC-6-300S/N 334 · Built 1971 Airframe modelDehavilland DHC-6-300 Engine modelPratt & Whitney PT6A-34 seriesTurbo-prop

From the FAA’s Accident/Incident Data System (AIDS), through its Aviation Safety Information Portal, as reported. The NTSB investigates accidents separately, and its record of an accident is the fuller one. The aircraft is matched to the registry by N-number and event date, checked against the reported make and model; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.

What happened

The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.

Both left and right propellers were installed after overhaul, the low pitch blade angles were adjusted and the beta rods jam nuts were safety wired in error. The wrongly installed safety wire induced excessive beta ring run-out on the left beta ring which caused the beta ring to break in flight. While landing on runway 24 at san Clemente Island naval auxiliary landing field (Nalf), approximately 10 to 20 feet above the runway, during the transition from approach to flare, the aircraft experienced a hard left yaw and a nose-down pitch due to the broken beta ring. The twin otter lost directional control during rollout and departed the runway. The airplane came to rest off the runway surface. The aircraft suffered substantial damage to the left wing, right main gear, and left propeller pitch mechanism. The accident happened 2.4 flight hours after the propellers were installed on the aircraft.

As the FAA filed it

BOTH LEFT AND RIGHT PROPELLERS WERE INSTALLED AFTER OVERHAUL, THE LOW PITCH BLADE ANGLES WERE ADJUSTED AND THE BETA RODS JAM NUTS WERE SAFETY WIRED IN ERROR. THE WRONGLY INSTALLED SAFETY WIRE INDUCED EXCESSIVE BETA RING RUN-OUT ON THE LEFT BETA RING WHICH CAUSED THE BETA RING TO BREAK IN FLIGHT. WHILE LANDING ON RUNWAY 24 AT SAN CLEMENTE ISLAND NAVAL AUXILIARY LANDING FIELD (NALF), APPROXIMATELY 10 TO 20 FEET ABOVE THE RUNWAY, DURING THE TRANSITION FROM APPROACH TO FLARE, THE AIRCRAFT EXPERIENCED A HARD LEFT YAW AND A NOSE-DOWN PITCH DUE TO THE BROKEN BETA RING. THE TWIN OTTER LOST DIRECTIONAL CONTROL DURING ROLLOUT AND DEPARTED THE RUNWAY. THE AIRPLANE CAME TO REST OFF THE RUNWAY SURFACE. THE AIRCRAFT SUFFERED SUBSTANTIAL DAMAGE TO THE LEFT WING, RIGHT MAIN GEAR, AND LEFT PROPELLER PITCH MECHANISM. THE ACCIDENT HAPPENED 2.4 FLIGHT HOURS AFTER THE PROPELLERS WERE INSTALLED ON THE AIRCRAFT.

NTSB investigation

The NTSB’s investigation of this event, with its probable cause and findings. Matched to this report by N-number and date.

NTSB WPR25LA250Accident · No injuriesClass 3 · LimitedPreliminary reportSan Celmente, CAOn August 11, 2025, at 1130 Pacific daylight time, a De Havilland DHC-6-300, N344CS, was substantially damaged when it was involved in an accident at San Clemente Island, California. The 2 pilots and 16 passengers were not injured. The airplane was operated…Aug 11, 2025 · Substantial damage