De Havilland DHC-2 N1433Z

Summary

On 9 September 1998 at about 18:45 local time, a De Havilland DHC-2 registered N1433Z, operated by Rust's Flying Service, Inc., was involved in an accident near Port Alsworth, Alaska, United States. 5 people were on board and 5 died. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

9 September 1998 at 18:45

Classification

Accident

Location

Port Alsworth, Alaska, United States

Coordinates

60.2009, -154.2804

Aircraft

De Havilland DHC-2

Registration

N1433Z

Category

Airplane

Engines

1

Operator

Rust's Flying Service, Inc.

Operating rule

Part 135: Air Taxi & Commuter

Purpose of flight

Unknown

Phase of flight

Not recorded

Route

Anchorage → Hoholitna River

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

ANC98FA145

5 people died.

The pilot's failure to maintain adequate airspeed which resulted in an inadvertent stall. Factors associated with this accident were the pilot's unfamiliarity with the geographic area, the low clouds, his becoming disoriented, and the blind canyon into which he flew. An additional factor was the intentionally disabled stall warning system.

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

Read the full NTSB narrative

The float equipped airplane was attempting to cross a mountain pass, following two other company airplanes. The first two pilots, and passengers, described five to seven miles visibility, 700 feet ceilings, clouds hanging on the mountainsides, and misty rain. The route of flight required several turns in the pass. The pilot had not flown through the pass in marginal Visual Flight Rules (VFR) weather before this flight. After the first two airplanes went through the pass, they lost radio contact with the accident pilot, and did not see or hear from him again. The wreckage was later located at the head of an intersecting canyon, two miles before the correct pass. The airplane had been modified with a Short Take Off and Landing (STOL) kit. Canadian certification flight tests had determined that this modification eliminated aerodynamic warning of impending stalls, and therefore required an audible stall warning. Company pilots indicated it was common for the stall warning system to activate at an airspeed 10-15 miles per hour above the actual stall. At the time of the accident, the airplane did not have the ventral fin installed, and a takeoff flaps setting was selected. The audible stall warning circuit breaker was found in the pulled (disabled) position.

Quoted verbatim from the NTSB record.