Aftermath: First There Is a Mountain

Situational awareness is increasingly being transferred from pilots' brains to their microchips.

Aftermath

Aftermath

The 77-year-old, 8,000 hour pilot-owner of a Cessna 182, accompanied by his wife, flew from Anchorage to Juneau, Alaska, on a July afternoon. The couple was in the process of moving to Hoonah, about 31 nm west-southwest of Juneau; the ostensible purpose of this trip was to position the 182 there before the start of winter. The pilot’s wife intended to return to Anchorage, but the 505 nm IFR trip took longer than expected, and her Alaska Airlines flight was taxiing out when they arrived. She rebooked for the following morning, and the couple then flew over to Hoonah for the night.

Her flight back to Anchorage was to depart at 7:28 a.m. At 6:43 a.m., the local controller at Juneau received a call from the pilot, reporting 10 miles southwest for landing. The controller told him to report four miles out. A moment later, a faint ELT signal was picked up in the tower and also at the Juneau Flight Service Station.

Delayed by worsening weather, searchers located the wreckage of the 182 the next day in mountainous terrain a few miles south of the Juneau International Airport (PAJN). The airplane had struck the descending side of a ridge on Douglas Island, coming to rest on a rock ledge at the 3,100-foot level. The impact was sufficiently violent that the engine, propeller and nosewheel broke away from the airframe and tumbled 900 feet down into the valley below.

Juneau lies amid a jumble of islands, inlets, channels, fjords and peaks. The climate tends toward cloudy and wet; Ketchikan, a little farther south, enjoys between 12 and 13 feet of rain a year. On the day of the accident, however, the weather was not bad: Hoonah was reporting 10 miles visibility under a 3,500-foot overcast with calm winds; Juneau was five miles, 2,800 broken and 3,600 overcast. The mountains south of Juneau were misty and obscured.

Douglas Island lies directly south of Juneau. The peaks in its center rise to 3,350 feet. A straight line from Hoonah to the Juneau airport just misses the northern shore of Douglas Island but crosses a 1,200-foot ridge on the Mansfield Peninsula, halfway between Hoonah and Juneau.

The pilot carried two handheld Garmin GPS units, a 195 and a 495. Neither was badly damaged in the crash, and accident investigators were able to download position and altitude logs of the fatal trip from both.

The ground track was not perfectly straight, but it was straight enough to suggest an airplane being hand-flown along a GPS course. Curiously, the course was not that from Hoonah to the Juneau airport; instead, it pointed toward Juneau Harbor Seaplane Base (5Z1), six miles southeast of the airport. One of the GPS units contained a previously stored program for a flight from Hoonah to the seaplane base; it seemed probable the pilot somehow selected it by mistake.

Six miles is a small difference, but when the total distance to be flown is only 31 miles, the angular error is 13 degrees, and in the mountainous terrain surrounding Juneau it had the effect of putting obstacles in the pilot’s way that ought not to have been there. The first was a 3,300-foot peak on the Mansfield Peninsula. The previous evening that ridge had been several miles to his left as he flew from Juneau to Hoonah; now, strangely, it was right in his way, and he had to swerve, and climb 600 feet, to avoid it.

Nine miles farther along, he should have had Juneau in sight; his groundspeed was 125 knots and he had been airborne for 15 minutes. He had already called to report that he was 10 miles southwest — a figure that actually reflected the GPS-reported distance from the seaplane base. But now he encountered another oddity: a second ridge where there should have been none at all.

He may have been flying in mist just below the overcast or between layers. The illumination was fair; the Alaskan summer sun had been up for two hours. He was level at 2,800 feet but then started to climb. Judging from the altitudes in the GPS log, which were recorded 10 times per minute, he must have been surprised by the steepness of the ridge because, after several seconds of climbing gradually at 89 knots groundspeed, the 182 suddenly shot upward from 3,166 feet to 3,583 feet at 2,000 fpm, while its groundspeed dropped from 101 to 34 knots.

It cleared the ridge but crashed a short distance past it. Perhaps it stalled; five seconds after the 34-knot point, one more entry was made in the GPS log, with a groundspeed of 41 knots.

As the National Transportation Safety Board explained it:

Given the lack of mechanical deficiencies with the airplane, the absence of any distress communications, and the pilot’s self-induced pressure to get his wife to the airport to avoid missing her flight, it is likely the pilot flew into instrument meteorological conditions while tracking his portable GPS receiver to the wrong destination and subsequently collided with mountainous terrain.

This accident encourages reflection on the nature of mistakes. Everyone makes them; perhaps some people are more aware of their mistakes than others. There have been accidents caused by careless data entry, improper altimeter setting, radio frequencies off by one digit. If it can be done wrong, someone will. Of course, far more mistakes are made that don’t lead to accidents; the vast majority are inconsequential, and so we regard them, and our propensity for them, with indulgence.

Our pilot flew from Juneau to Hoonah just the previous evening and must have made the trip many times before, so he knew the general lay of the land. Why was it necessary at all to use GPS to go 30 miles in a straight line among a host of unambiguous landmarks? But he did; perhaps it seemed convenient, or he wanted an extra layer of assurance, or it was simply for fun.

One defense against navigational mistakes goes by the name of situational awareness. Unfortunately, you can be highly aware of your situation, completely tuned in to the task of flying and yet be operating in some mistaken conception about what that situation actually is. Our pilot probably believed he had everything under control; after all, he had not one but two GPS units, and they agreed with one another.

Something built into our brains inclines us to ignore evidence that conflicts with expectation. In this case, the pilot, having selected, as he believed, the Hoonah-to-Juneau route on his GPS, had a strong, and reasonable, expectation that as long as they showed him to be on that track, he must be in the right place.

Now, cruising at 3,000 feet, he encountered a mountain. He climbed and made a sudden deviation to the left to avoid it. Where had that mountain been when he made the same trip, in the opposite direction, last evening?

Perhaps he said to himself that he must have been slightly north of the straight-line course then, and so this peak had been a few miles off to his left. A glance at the GPS screens would reassure him: There was the course line; there was the mountain. From this point to Juneau, it should all be open water.

Then a second mountain loomed. This was more of a problem. The first mountain could be explained as a slight track error. This one should not exist at all. Things began happening rapidly — too rapidly to allow the pilot to analyze them. The ground was coming up in front of him. It was already too late.

Today, situational awareness is increasingly transferred from a pilot’s brain to his microchips. There is no straightforward protection, other than double- and triple-checking every action against the type of clerical errors we may make in our interactions with digital devices. Two GPS units provide no redundancy if both confirm you in the same mistake. What is needed — and remains available, at least when the terrain is visible and while we still have the VOR network at our disposal — is independent confirmation that we are where we think we are. Visual navigation ought to be a constant cycle of expectation and confirmation: Charts and terrain should come together like two sides of a zipper.

You remember — it’s what we called “pilotage.”

This article is based on the NTSB’s report of the accident and is intended to bring the issues raised to our readers’ attention. It is not intended to judge or to reach any definitive conclusions about the ability or capacity of any person, living or dead, or any aircraft or accessory.