ANC98FA145

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.

History of flight

On September 9, 1998, about 1045 Alaska daylight time, a Dehavilland DHC-2, float equipped airplane, N1433Z, sustained substantial damage when it impacted mountainous terrain about 3,600 feet msl near Telequana Pass, Alaska. The pass is about 48 miles north-northwest of Port Alsworth, Alaska. The commercial pilot and the four passengers sustained fatal injuries. The flight was operated by Rust's Flying Service, Inc., of Anchorage, Alaska. The flight was conducted under 14 CFR Part 135 as an on-demand air taxi transporting hunters from the Lake Hood seaplane base in Anchorage, to a hunting lodge on the Hoholitna River, about 190 miles west of Anchorage. Visual meteorological conditions prevailed at the time of the accident, and a company VFR flight plan was in effect.

The accident airplane was the third of three company airplanes crossing the mountain pass, spaced between three and five miles apart. The pilots described the cloud ceilings as 4,500 feet msl at the 3,300 feet msl pass, with five miles visibility.

The pilots of the first two airplanes told the NTSB investigator-in-charge (IIC) that they were in radio contact with the pilot of the accident airplane as they crossed through the pass, and then lost radio contact as they descended below the steep terrain. Both lead pilots indicated they believed it was due to terrain, and that when they continued to the west and still were not able to make contact with the airplane, they assumed the pilot had turned around because he saw something he did not like, and was attempting another route.

The first two pilots arrived at their destination and noted that the accident airplane had not arrived. They waited about one hour, then continued along their scheduled routes. They told the NTSB IIC that they were concerned when the accident pilot did not arrive, and asked the lodge owner to notify the company if the airplane had not arrived within one hour of their departure. The air taxi company owner told the NTSB IIC that they never received a call from the lodge telling them the airplane had not arrived.

At 1235, the Alaskan Air Command Rescue Coordination Center (RCC) began a search after search and rescue satellites received an Emergency Locator Transmitter (ELT) signal on 121.5 MHz. At 1400, the National Park Service dispatched an airplane from Port Alsworth to search for the ELT at the request of RCC. At 1500 the search airplane heard a signal on 121.5 MHz coming from the canyon where the wreckage was discovered. Due to low ceilings and visibility, the airplane pilot requested a helicopter be used to search the canyon. At 1825, the wreckage was located by the crew of an Alaska Air National Guard helicopter.

Personnel information

The pilot held a commercial pilot certificate for single engine land and sea airplanes, and multiengine land airplanes. He held an instrument rating, and a flight instructor rating for single engine airplanes. His most recent second class medical certificate was issued on May 26, 1998, and contained no restrictions. He was an airframe and powerplant mechanic.

The pilot was first hired by the company as a mechanic, on March 3, 1998. He had been employed as a pilot since May 1, 1998. This was his first season with this company as a pilot, and his third season flying in Alaska. It was his first season flying in the Alaska Mountain Range area. The Director of Operations and Chief Pilot told the NTSB IIC it was his fourth time through Telequana Pass. They said the previous trips were in better weather conditions than the day of the accident.

The pilot was qualified in the Cessna 206 on May 22, 1998, and the DeHavilland DHC-2 on July 17, 1998. The pilot's initial hire flight training and 14 CFR 135.293 competency checks were performed in the Cessna 206. His transition training to the DHC-2 consisted of ground training and a flight examination to meet the requirements for CFR 135.293. Stall maneuvers in the DHC-2 were recorded on the pilot's 135.293 check flight record on July 17, 1998.

According to the pilot's personal logbook, and company flight records, at the time of the accident he had accumulated about 1,820 hours of flight time. The pilot had accrued 151 hours of experience in the DeHavilland DHC-2. In the previous 90, and 30 days, he had flown 338 and 118 hours, respectively. Of these, 133 and 59 hours were in the DHC-2. The day prior to the accident he flew five hours, all in the DHC-2.

The day of the accident was a scheduled work day for the pilot. The accident flight was the pilot's first flight of the day.

Aircraft information

General

The airplane was a Dehavilland DHC-2 Mark I "Beaver," manufactured by the DeHavilland Aircraft Company of Canada. It was registered to Rust Properties, LLC, of Anchorage, Alaska. The airplane was operated by Rust's Flying Service, Inc., of Anchorage. The airplane was powered by a single Pratt & Whitney R-985 radial engine, rated to produce 450 shaft horsepower. The airplane had accumulated 12,948 total hours in operation at the time of the accident.

The airplane was configured with seating for the pilot and four passengers.

The airplane's maximum allowable takeoff weight was 5,370 pounds. It had STC number SA4025NM incorporated, which provided a gross weight increase from 5,100 pounds. The horizontal stabilizers were modified with Kenmore "finlets" on the stabilizer tips. The airplane did not have a lower surface ventral fin installed underneath the empennage.

It was equipped with EDO 4930 nonamphibious floats. The airplane had always been operated on floats while owned by the company. The airplane was modified with an AOG Air Support Baron / STOL (Short Take Off and Landing) kit on May 5, 1994. This modification was approved under U.S. Supplemental Type Certificate (STC) number SA-1070NE, and Canadian Supplemental Type Approval (STA) number SA92-45.

This STOL modification consisted of a full span contoured leading wing edge, drooped wing tips, upper wing surface stall fences, and trailing edge flap gap seals. Additionally, an electrically powered, aural stall warning horn was installed as a mandatory component in the modification kit.

The airplane was maintained on a 100 hour inspection cycle. The most recent inspection was an annual inspection completed on August 19, 1998, 64 hours prior to the accident. A review of maintenance records revealed no repetitive maintenance problems. Other pilots who had recently flown the airplane did not recall any discrepancies.

Weight and Balance

The pilot fueled his own airplane. It is unknown how much fuel he placed in the airplane. The pilots of the other two airplanes in the flight said they departed Lake Hood with full fuel in the forward and center tanks, eight gallons in the aft tank, and full tip tanks. They told the NTSB IIC that they expected the accident pilot to use a similar fuel load.

498 pounds of cargo was removed from the airplane (443 pounds at the accident site, and an additional 55 pounds after airplane recovery). An estimated additional 40 pounds of perishable goods was left at the wreckage site. The total cargo accounted for was 538 pounds (443 + 55 + 40 pounds).

According to their driver's licenses, the passengers and pilot weighed a combined total of 890 pounds.

Using these weights, the estimated weight at the time of the accident was as follows:

Empty weight of airplane - 3,386 pounds Pilot and Passengers - 890 pounds Cargo (baggage) -- 538 pounds Zero Fuel Weight - 4,814 pounds Estimated fuel at takeoff - 556 pounds (93 gallons to reach maximum allowable take off weight) Total weight at takeoff - 5,370 pounds

Estimated fuel consumption (1 hour 15 minutes) - 150 pounds (25 gallons) Total weight at accident - 5,222 pounds

The estimated airplane center of gravity (CG) at the accident site was 104.17 inches aft of datum, with a forward and aft limit of 101.25 and 106.1 inch