Confusion over what radio frequency pilots flying west of the Susitna River should be using still lingers, more than two years after four people died as a result of a midair collision in the area between planes on different signals.
The official Federal Aviation Administration chart for the flats in the western part of the Susitna valley calls for Common Traffic Advisory Frequency, or CTAF, 122.9 to be used over much of the area. The chart specifies the use of 122.9 around the Deshka River Recreation Area, a popular flight path during king salmon season, from May 15 to July 15.
Multiple private airports in the valley reaching as far west as Skwentna are assigned CTAF 122.8, according to the chart.
Page 402 of the Supplement Alaska handbook, required to be onboard during a flight in the area along with the chart, formerly read: "Airports south and west of the Parks Highway are assigned 122.8. Airports north and east of the Parks Highway are assigned 122.9."
Greg Holt, acting FAA regional administrator, said during a panel discussion at the Alaska Air Carriers Association convention Feb. 18 that the page was recently removed from the pamphlet, which is printed quarterly.
It's widely believed that the discrepancy about which is the correct radio signal could have led to the July 30, 2011, tragedy over Sister Lake near Trapper Creek in which a Cessna 206 taking off from the lake collided with a Cessna 180. The Cessna 180 crashed and caught fire, killing its four occupants. The pilot of the Cessna 206 radioed for help and was able to fly about 90 miles to Anchorage after the incident.
A May 2013 National Transportation Safety Board report on the incident found that the pilot of the 206 was on CTAF 122.8, while the 180 pilot was using CTAF 122.9. The report does not assign fault to either pilot. Both were headed to Amber Lake, less than a mile from the crash.
AACA board member and operator of Davidson Aviation Danny Davidson lives in Trapper Creek and has said the area for years was understood to be under CTAF 122.9.
Davidson said at the Feb. 18 meeting that the valley operators and lodge owners have agreed upon a solution. The unofficial agreement would make the east bank of the Susitna River the dividing line for the CTAFs from the far lower reaches of the river up to the area where it is closely paralleled by the Parks Highway near Montana. West of that line would be CTAF 122.9 territory all the way to the Alaska Range, and to the east CTAF 122.8 would be used.
"We're hopeful that there will be clearly defined boundaries by the start of the flying season" next spring, Air Carriers Executive Director Joy Journeay said.
A working group formed shortly after the 2011 collision of government and industry stakeholders that Davidson is part of has not reached agreement, however.
Holt said the fact that the radio concerns are still unresolved points to the complexity of the issue and the challenge of aligning all of the user groups.
"The FAA is in a very difficult position in that we really need a consensus from the public, the aviation industry about where those boundaries were and that's what we're looking for from the working group," Holt said.
The next Alaska Supplement handbook is published in April, he said -- a deadline of sorts to get the issue resolved before flight activity ramps up again, as Journeay said she hopes to do.
Holt said he worries that pulling the CTAF guidelines from the handbook could end up creating more confusion.
"I think that the lack of having anything out there is even worse," he said.
CTAFs were never originally meant to be used as "area frequencies" Holt noted further. Rather, they were intended for pilots to use near airports in higher traffic areas, he said.
Journeay said the AACA would call for a public meeting with a goal to resolve the matter within two weeks and submit the end recommendations to the FAA.
Mountain pass recommendations
Skip Nelson, owner of Anchorage-based ADS-B Technologies that develops air traffic management systems, chaired a working group formed by the FAA Safety Team to find a solution that would mitigate near mid-air collisions in mountain passes across the state.
In his presentation to the Air Carriers, Nelson likened mountain passes to other aerial "choke points" such as roads, beaches, rivers, and even GPS routes used as common flying corridors and visual waypoints that draw aircraft together.
He recommended the FAA limit the number of radio frequencies used in all mountain passes in the state to three, or preferably one, he said.
"The solution is not a bunch of frequencies. That demands confusion," Nelson said.
By standardizing communications pilots flying in unfamiliar passes would know the frequency for the pass, regardless of where they were, he said. Using popular, low power VHF radios would also limit the range of communication and minimize distant chatter, according to Nelson.
Further, if pilots would limit their activity on the radios, their location and bearing would be easier to decipher without confusion, Nelson emphasized.
"Reduce the number of frequencies, simplify the system and get better radio communication," to make mountain pass travel safer, he said.