The pilot and sole occupant of the helicopter that crashed at Birchwood Airport last week was practicing maneuvers with an external load on a long-line at the time of the accident, according to a preliminary report from the National Transportation Safety Board.
The NTSB released its preliminary report Sunday on the crash that killed pilot Tom Moore of Anchorage and injured aircraft mechanic Paul Mallory of Chugiak. Mallory, who was nearby and rushed to the crash site in an unsuccessful effort to extract Moore from the wreckage, was severely burned.
The Robinson R44 II helicopter N392GP was operated by Global Positioning Systems under section 133 of the Federal Aviation Regulations, which governs operation of external loads for rotorcraft. In the NTSB report, a company representative said Moore, a company owner, was conducting an external load practice flight with a 150-foot-long line attached to a fluid-filled 55-gallon barrel in preparation for an upcoming project. Reported weather conditions at the airport at the time of the accident were 10 miles' visibility, clear skies and wind at 3 knots, thus, weather did not appear to be a factor.
A pilot on short final for runway 20 when the accident occurred told investigators that he heard the helicopter pilot providing regular position reports as he maneuvered the helicopter.
The pilot "saw the helicopter maneuver from a hover over the end of runway 20 with the barrel suspended on the long-line to the area east of the runway on the ramp near where the accident occurred," according to the report.
According to other witnesses, this was an area where Moore typically set down the barrel and landed.
The airplane pilot reported that the nose of the helicopter pitched up and then "rolled to the left, descended, and impacted the ground." There were also reports from other witnesses of "two loud 'bang' sounds a few seconds apart." When these witnesses looked for the source of the noise, they saw the helicopter on the ground in flames.
The fuselage came to rest on its left side on a gravel road near the paved airport ramp. Most of the helicopter's cockpit and cabin structure were burned. The tail boom and tail rotor were on the ground aft of the burned fuselage. The main rotor mast assembly with the main rotor hub attached was several feet away from the fuselage and engine. One main rotor blade was separated outboard of the hub near the blade root, and the other main rotor blade was attached in its entirety and damaged. The length of a ground scar near the fuselage was consistent with the length of a main rotor blade. The barrel was found on its side in grass near the airport ramp.
The R44 has a history of post-impact fires and was recently the focus of an NTSB recommendation on the issue. In January the board issued a letter urging the Federal Aviation Administration to require the retrofit of existing fuel tanks for the rotorcraft. This recommendation was based on five years of investigation by both the NTSB and the Australia Transport Safety Board. In 2013 that country's Civil Aviation Safety Authority issued an airworthiness directive mandating R44 operators retrofit their helicopters with bladder-type fuel tanks by April 30, 2013.
Robinson Helicopter Company, the R44 manufacturer, issued a service bulletin in December 2010 advising owners, operators, and maintenance personnel of R44 helicopters with older fuel tanks to retrofit them to the bladder-type tanks which are present in new models. The suggested date for the retrofits was by December 31, 2014. The company later issued a revision to this service bulletin, advising April 30, 2013, as a date for retrofitting fuel tanks, which CASA adopted in its airworthiness directive.
According to the January NTSB safety recommendation, "some owners have been waiting until their helicopters are ready for the next 2,200-hour overhaul to accomplish the retrofit to minimize downtime and costs, and other owners cited additional financial reasons and no formal requirement as explanations for not accomplishing the retrofit."
The FAA issued a Special Airworthiness Information Bulletin in late 2012 urging R44 owners and operators to take note of the April 30, 2013, date from Robinson Helicopter and the availability of the bladder-type tanks. No airworthiness directive or other form of mandatory compliance has been issued by the agency -- something the NTSB would like changed.
When the Australian authority pursued issuance of its airworthiness directive in 2013, the FAA advised CASA that "after analysis of the data, the R44 fuel system crashworthiness does not appear inconsistent with that of other similar helicopters and (the FAA) will be taking no corrective action."
The investigation into the Birchwood accident is active, and the preliminary report did not specify whether N392GP was equipped with the older fuel tanks. A probable cause report will likely be issued by the NTSB in early 2015.
Reach Colleen Mondor at email@example.com.
By COLLEEN MONDOR