Communication problems were at the heart of a March 2013 cargo plane crash near Dillingham that left two people who flew into a mountain dead, according to the National Transportation Safety Board.

In a report released Monday on the probable cause of the March 8, 2013 ACE Air Cargo crash in poor weather that killed pilot Jeff Day, 38, and first officer Neil Jensen, 21, the NTSB cites “the flight crew's failure to maintain terrain clearance, which resulted in controlled flight into terrain in instrument meteorological conditions.”

A variety of factors are listed as contributing to the Beech 1900C’s crash in the Muklung Hills, including “the flight crew's failure to correctly read back and interpret clearance altitudes issued by the air traffic controller,” as well as “the air traffic controller's issuance of an ambiguous clearance to the flight crew, which resulted in the airplane's premature descent.”

Day and Jensen, both Anchorage residents, took off from Ted Stevens Anchorage International Airport at about 5:45 a.m., stopping in King Salmon before continuing to Dillingham. They called the FAA’s Air Route Traffic Control Center in Anchorage at 7:57 a.m. to say they had reached the local airport’s holding pattern.

NTSB Cites Crew, Controller in Deadly 2013 Dillingham Crash

A Federal Aviation Administration area navigation, or RNAV, chart for landing in Dillingham under instrument flight rules indicates the minimum altitudes planes should maintain at various points of their approach. The chart shows that as Day and Jensen’s flight came in from the southeast toward ZEDAG, the point at which planes enter the holding pattern to land in Dillingham, it should have been at an altitude of at least 5,400 feet, with only a slight reduction in that minimum within the pattern after arriving.

“One of three peaks in the Muklung Hills with an elevation of 2,550 feet is located about 6 miles north-northwest of ZEDAG,” NTSB officials wrote. “The published minimum safe altitude while flying in the holding pattern is 4,300 feet (above mean sea level).”

An NTSB log of transmissions shortly after between the ARTCC and the ACE Air Cargo flight, with the call sign Ace Air 51 or AER51, lists the plane at an altitude below those approved minimums. The controller, calling the Dillingham Flight Services Station for an update on runway conditions, apparently doesn’t notice:

AER51: We'll stay with you. Cleared to ZEDAG transition for RNAV one nine approach into Dillingham. Maintain [ARTCC controller dialing the DLG FSS] two thousand (feet) until a published segment of the approach Ace Air fifty one.
ARTCC: Is Ace Air fifty one Beech nineteen hundred Dillingham one seven two zero RNAV one nine.
AER51: Anchorage Center Ace Air fifty one [we're] approaching ZEDAG we'd like to hold waiting for more information if possible.
ARTCC: Ace Air fifty one say again?
AER51: Ace Air fifty one requesting hold at ZEDAG for runway conditions.
ARTCC: Ace Air fifty one hold north of ZEDAG as published expect further clearance one eight zero zero upon your request.
AER51: Hold north of ZEDAG expect further clearance one eight zero zero.

Just after receiving a runway update from Dillingham, the controller relayed it to Day and Jensen at 8:09 a.m. -- but he never heard from them again. Heavy snow and wind kept searchers from reaching the crash site until the next day, when an Alaska Air National Guard chopper arrived and confirmed that both men were dead.

NTSB investigators found that the plane had crashed at an elevation of about 2,000 feet, leaving an uphill fan of debris over several hundred feet from its point of contact. The crash destroyed three cockpit computers in the Beech, precluding any attempt to determine whether terrain warnings from them had been suppressed; while ACE Air Cargo had been installing cockpit video and flight recorders fleetwide after two people died in a 2010 crash near Sand Point, the wrecked aircraft didn’t yet have them.

“The first structural piece was located about 400 feet from the initial impact point,” NTSB officials wrote. “Large sections of fuselage and expelled cargo were located about 525 feet from the initial impact point. The fuselage and cockpit were found separated into three large pieces.”

When NTSB investigators spoke with the controller in the crash, he told them he hadn’t been fully aware of Day and Jensen’s altitude during their final minutes of flight.

“During postaccident interviews, the controller who handled the flight stated that he did not expect the airplane to descend below 5,400 feet and that he did not notice when it did so,” NTSB officials wrote. “He stated that he did not notice the airplane's actual altitude when the pilot requested holding at ZEDAG. He stated that, when he cleared the pilot to hold at ZEDAG ‘as published,’ he expected the pilot to climb the airplane to 4,300 feet (above mean sea level) as shown in the profile view of the approach procedure.”

Recorded data at the center indicated that the system had attempted to warn the controller about the imminent crash.

“Air traffic control (ATC) recorded automation data showed that the airplane's trajectory generated aural and visual minimum safe altitude warnings (MSAW) on the controller's radar display, which included a 1-second aural alarm at 0809:16 and a flashing ‘MSAW’ indication in the airplane's data block that continued from 0809:16 until the end of the flight,” NTSB officials wrote. “The controller said that he was not consciously aware of any such warnings from his display. The controller did not issue any terrain conflict alerts or climb instructions to the flight crew.”

While the NTSB report quotes FAA regulations calling for important numbers like altitude restrictions to be read back in communications between pilots and controllers, it quotes more extensively from those governing a pilot’s autonomy in flight – including one which states that “The pilot-in-command of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft.”

“‘If ATC issues a clearance that would cause a pilot to deviate from a rule or regulation, or in the pilot's opinion, would place the aircraft in jeopardy, IT IS THE PILOT'S RESPONSIBILITY TO REQUEST AN AMENDED CLEARANCE,’” NTSB officials quoted. “‘Similarly, if a pilot prefers to follow a different course of action…THE PILOT IS EXPECTED TO INFORM ATC ACCORDINGLY [capitalization emphasis in original document].’”

Clint Johnson, the NTSB’s chief investigator in Alaska, says the report indicates shared responsibility for the crash both in the air and on the ground.

“There’s culpability on both sides,” Johnson said. “There are a lot of checks and balances and safety initiatives that are in play, but for whatever reason they were all ignored.”

Johnson says much about the crash that could be known never will be, due to the absence of voice or data recorders -- cheap technology that wasn’t required aboard the ACE flight.

“One of the most frustrating things is that we don’t know what was going on in that cockpit,” Johnson said.

Speaking with Channel 2 Monday afternoon, Johnson says that to his knowledge no criminal charges are pending against the controller in the crash.

"It's important to reiterate that this was an accident, first and foremost," Johnson said.

The NTSB report also found that Day and Jensen violated company regulations governing descent approaches.