De Havilland DHC-4A N702SC

Summary

On 30 January 1997 at about 03:10 local time, a De Havilland DHC-4A registered N702SC, operated by South Central Air, was involved in an accident near Sparrevohn, Alaska, United States. 2 people were on board and one died, one was seriously injured. The aircraft was destroyed. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

30 January 1997 at 03:10

Classification

Accident

Location

Sparrevohn, Alaska, United States

Nearest airport

Sparrevohn Lrrs (SVW)

Coordinates

63.4701, -162.1096

Aircraft

De Havilland DHC-4A

Registration

N702SC

Category

Airplane

Engines

2

Operator

South Central Air

Operating rule

Part 135: Air Taxi & Commuter

Purpose of flight

Unknown

Phase of flight

Not recorded

Route

St Marys → Kenai

Aircraft damage

Destroyed

Weather

VMC

Light

Night/Dark

NTSB number

ANC97FA024

1 person died.

loss of the right engine propeller control oil, which led to an overspeed of the right engine and propeller, and necessitated a shut-down of the right engine; and failure of the pilot to maintain adequate altitude/distance from terrain during visual approach for a precautionary landing at an alternate airport. Factors relating to the accident were: fluctuation of the left engine power, premature lowering of the airplane flaps, and an encounter with adverse weather conditions (including high winds, severe turbulence, and white-out conditions) during the approach.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

The CFR Part 135 cargo flight (flt) departed at night on an IFR flt with a load of mining equipment. Route of flt was over remote/mountainous terrain. About 2 hrs after takeoff, while cruising at 12,000' msl, the right engine (#2 eng) & propeller began to overspeed. The captain (capt) feathered the #2 eng & declared an emergency. He began to divert to an alternate destination, about 120 miles away in an area of lower terrain, but the aircraft (acft) would not maintain altitude (single eng service ceiling, as loaded, was about 8,700'). The capt increased power to the #1 eng, but it began to produce banging & coughing noises. The capt elected to perform an emergency landing at a nearby, remote, military airfield (A/F). The A/F was located in mountainous terrain & had a one-way, daylight only approach. The capt lowered the gear & flaps, & began a visual approach while attempting to keep the runway end identifier lights (REIL) in view. The acft encountered severe turbulence, & the capt applied full throttle to the #1 eng in an attempt to climb. The REIL disappeared from view, & the acft collided with snow covered terrain about 2 miles west of the A/F. Ground personnel at the A/F reported high winds & blowing snow with limited visibility. Postcrash exam of the #2 eng revealed a loss of the propeller control system hydraulic oil. Flt at 12,000' was conducted without crew oxygen. The crew had exceeded their maximum allowable duty day without adequate crew rest.

Quoted verbatim from the NTSB record.