Lake Brooks - King Salmon

The pilot and three passengers were departing a remote lake in a float equipped airplane. The pilot positioned the hydraulic actuated flaps to 20 degrees. After takeoff, about 150 ft above the water, the pilot positioned the flap lever to the 'UP' position in preparation of pumping the flaps up, but said he did not move the pump handle. Turbulence was present during the takeoff, and during a left turn, the pilot encountered a severe gust at the time he positioned the flap lever. The airplane stalled in a left turn that steepened to almost a 90 degree bank. The airplane descended and the left wing contacted the surface of the lake. The left wing was torn off the fuselage, and the floats were crushed upward. Both flaps are activated by a common torque tube connected to a double-acting flap actuating cylinder. At the accident scene, the right wing flap and right aileron were observed to be extended to an intermediate position. The weather conditions included 20 kts of wind, turbulence, and rain. The pilot expressed a concern that the flaps may have retracted without being pumped to the up position. An examination of the flap system and the ratchet valve assembly was conducted after the airplane was recovered and the wings were removed. Leakage of hydraulic fluid and air was observed through the ratchet valve. Additional testing of the ratchet valve at an overhaul facility did not reveal any leakage.

Flight / Schedule

Lake Brooks - King Salmon

Registration

N67207

MSN

305

Year of Manufacture

1952

Date

September 24, 1996 at 10:15 AM

Type

CRASH

Flight Type

Charter/Taxi (Non Scheduled Revenue Flight)

Flight Phase

Takeoff (climb)

Crash Site

Lake, Sea, Ocean, River

Crash Location

Lake Brooks Alaska

Region

North America • United States of America

Coordinates

58.5020°, -155.8981°

Crash Cause

Human factor

Narrative Report

On September 24, 1996 at 10:15 AM, Lake Brooks - King Salmon experienced a crash involving De Havilland DHC-2 Beaver, operated by Branch River Air Service, with the event recorded near Lake Brooks Alaska.

The flight was categorized as charter/taxi (non scheduled revenue flight) and the reported phase was takeoff (climb) at a lake, sea, ocean, river crash site.

4 people were known to be on board, 0 fatalities were recorded, 4 survivors were identified or estimated. This corresponds to an estimated fatality rate of 0.0%.

Crew on board: 1, crew fatalities: 0, passengers on board: 3, passenger fatalities: 0, other fatalities: 0.

The listed crash cause is human factor. The pilot and three passengers were departing a remote lake in a float equipped airplane. The pilot positioned the hydraulic actuated flaps to 20 degrees. After takeoff, about 150 ft above the water, the pilot positioned the flap lever to the 'UP' position in preparation of pumping the flaps up, but said he did not move the pump handle. Turbulence was present during the takeoff, and during a left turn, the pilot encountered a severe gust at the time he positioned the flap lever. The airplane stalled in a left turn that steepened to almost a 90 degree bank. The airplane descended and the left wing contacted the surface of the lake. The left wing was torn off the fuselage, and the floats were crushed upward. Both flaps are activated by a common torque tube connected to a double-acting flap actuating cylinder. At the accident scene, the right wing flap and right aileron were observed to be extended to an intermediate position. The weather conditions included 20 kts of wind, turbulence, and rain. The pilot expressed a concern that the flaps may have retracted without being pumped to the up position. An examination of the flap system and the ratchet valve assembly was conducted after the airplane was recovered and the wings were removed. Leakage of hydraulic fluid and air was observed through the ratchet valve. Additional testing of the ratchet valve at an overhaul facility did not reveal any leakage.

Aircraft reference details include registration N67207, MSN 305, year of manufacture 1952.

Geospatial coordinates for this crash are approximately 58.5020°, -155.8981°.

Fatalities

Total

0

Crew

0

Passengers

0

Other

0

Crash Summary

The pilot and three passengers were departing a remote lake in a float equipped airplane. The pilot positioned the hydraulic actuated flaps to 20 degrees. After takeoff, about 150 ft above the water, the pilot positioned the flap lever to the 'UP' position in preparation of pumping the flaps up, but said he did not move the pump handle. Turbulence was present during the takeoff, and during a left turn, the pilot encountered a severe gust at the time he positioned the flap lever. The airplane stalled in a left turn that steepened to almost a 90 degree bank. The airplane descended and the left wing contacted the surface of the lake. The left wing was torn off the fuselage, and the floats were crushed upward. Both flaps are activated by a common torque tube connected to a double-acting flap actuating cylinder. At the accident scene, the right wing flap and right aileron were observed to be extended to an intermediate position. The weather conditions included 20 kts of wind, turbulence, and rain. The pilot expressed a concern that the flaps may have retracted without being pumped to the up position. An examination of the flap system and the ratchet valve assembly was conducted after the airplane was recovered and the wings were removed. Leakage of hydraulic fluid and air was observed through the ratchet valve. Additional testing of the ratchet valve at an overhaul facility did not reveal any leakage.

Cause: Human factor

Occupants & Outcome

Crew On Board

1

Passengers On Board

3

Estimated Survivors

4

Fatality Rate

0.0%

Known people on board: 4

Operational Details

Schedule / Flight

Lake Brooks - King Salmon

Flight Type

Charter/Taxi (Non Scheduled Revenue Flight)

Flight Phase

Takeoff (climb)

Crash Site

Lake, Sea, Ocean, River

Region / Country

North America • United States of America

Aircraft Details

Registration

N67207

MSN

305

Year of Manufacture

1952