Alaskan Landing Mishap Injured Nine

Editor's Note: This is one of the stranger Prelims we've come across lately. Below is the unedited text of the National Transportation Safety Board's initial findings regarding an April 9 landing accident in Unalaska, AK, involving a Grumman G-21A Goose and a truck...

NTSB Identification: ANC08FA050
Scheduled 14 CFR Part 135: Air Taxi & Commuter
Accident occurred Wednesday, April 09, 2008 in Unalaska, AK
Aircraft: Grumman G-21A, registration: N741
Injuries: 1 Serious, 8 Minor.

This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed.

On April 9, 2008, about 1630 Alaska daylight time, an amphibious Grumman G-21A airplane, N741, received substantial damage when it collided with a trailer van while on approach to Runway 30 at the Unalaska Airport, Unalaska, Alaska. The airplane was operated by Peninsula Airways, Inc., Anchorage, Alaska. The flight was being conducted under Title 14, CFR Part 135, as scheduled commuter Flight 325, when the accident occurred. Of the nine people on board, the airline transport pilot and seven passengers sustained minor injuries, and one passenger sustained serious injuries. Company flight following procedures were in effect. The flight originated at the Akutan Sea Plane Base, Akutan, Alaska, about 1615, and was en route to Unalaska.

Airplanes landing at the Unalaska Airport on Runway 30 pass low over Ballyhoo Road before reaching the approach threshold of the runway. Ballyhoo Road provides the only access between the city of Unalaska and the city dock facility, north of the Unalaska Airport. Trucks transporting large container vans between the trailer yard and the city dock facility routinely use the road. There are two remotely controlled gates with warning lights on each side of the runway threshold, designed to block vehicle traffic while airplanes are landing on Runway 30. Additionally, when the gate and warning light system is activated, the runway end identifier lights (REIL) are also activated. Prior to landing, pilots are instructed to activate the remotely controlled gate and warning light system.

Procedures for landing on Runway 30 are outlined in the Alaska Flight Information Supplement, which states, in part: "Stop light for vehicle traffic crossing Runway 30 threshold must be activated and deactivated for each aircraft operation over the threshold." Additionally, it states: " ...stop light for vehicle traffic crossing Runway 30 threshold, key 122.6 7 times for on, 3 times for stop light and REIL off."

During a telephone interview with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on April 10, the truck operator reported that he was transporting a 45-foot long trailer van from the Horizon Lines trailer yard to the city dock facility. He said that as he approached the part of the road where it crossed under the approach path of Runway 30, he saw that the warning lights were flashing, but the gates were not down, so he stopped the truck to wait for the warning lights to go out. After waiting for about 45 seconds, the driver looked to see if he could see any landing traffic, but he did not see any. He reported that with the red lights still flashing, he proceeded northbound, and into the threshold area. Shortly after entering the threshold area he heard a very loud bang, and the truck rocked to the left. He then saw the airplane collide with the runway on the left side of his truck.

The truck operator noted that he had worked in Unalaska for only 4 months, but during that time, the traffic gates at that intersection had never worked. He said that the flashing warning lights would routinely activate with no arriving traffic, and remain activated, which would block traffic for long periods of time.

During an interview with the NTSB IIC on April 11, the accident pilot said that as he started his initial approach to Runway 30, he activated the remotely controlled traffic warning devices as required. He said as he approached, he could see the REIL strobe lights, which are simultaneously activated when the gate and warning light system on the road is activated. Concurrently, he said he could see a large truck and trailer rig stopped at the intersection, adjacent to the southern traffic gate. During the approach, the pilot continued to intermittently watch the truck to be sure that it did not start moving. He configured the airplane for landing by lowering the airplane's landing gear and flaps, and completed his final prelanding checklist. The pilot said that as the airplane approached the runway threshold, he realized that the truck was now moving, and it was well within the threshold area. The pilot applied full engine power and pulled the nose up in an attempt to go-around, but as the airplane began to climb, the aft section of the airplane's belly and empennage struck the top of the trailer van.

The pilot said that immediately after the initial collision with the trailer, he had no elevator control, and the airplane descended uncontrollably, nose down. The airplane collided with the runway, and slid for several hundred feet.

During a telephone conversation with the NTSB IIC on April 10, a safety representative from the State of Alaska's Department of Transportation reported that the gates have been out of service for more than a year due to budgetary constraints, as well as pending equipment upgrades, which would include moving both gates to different sites along Ballyhoo Road.

FMI: www.ntsb.gov