An Alaska Success Story Using Emergency Locating Devices
Author: David Swartz, Senior Aviation Safety Engineer, Anchorage Aircraft Certification Office.
Like many days in Southeastern Alaska, the clouds were a little low on June 4, 2013, and they weren’t getting any higher. The cruise ship was in port. Flying conditions had been worse many times before, and everything had come out okay. Besides, VFR flying conditions were above minimums. So, at 3:31 PM on this particular day, a DeHavilland Beaver on floats took off from the seaplane base at Petersburg, AK, heading for the LeConte Glacier via a mountain pass and Horn Cliffs with a load of visitors from the cruise ship. The ceiling at takeoff was somewhere between 1,300 and 2,000 feet, and there was light rain falling restricting visibility through the windshield. At nearby Petersburg, the official visibility was reporting 2.5 miles, not counting seeing through a rain-spattered windshield.
As the pilot entered the pass toward Horn Cliffs, he added a bit of flaps and started to pull the nose up to climb at about 80 knots. As a result, the visibility over the nose was further reduced. So far, everything was perfectly normal; the pilot was probably chatting with his passengers when suddenly, through the rain-spattered windshield, trees appeared. The pilot banked left in a last-ditch attempt to avoid them, but the airplane stalled. The nose yawed right and headed for the tops of 200-foot tall mature trees. The airplane hit the treetops, breaking the first one off 80 feet above the ground. As the airplane fell, the left-wing was ripped off and snagged in the trees. The tail was smashed, and the float struts were collapsed as the airframe slammed into the steep mountainside.
As the airplane fell through the trees, it sacrificed itself so that its people might live. When the airplane came to rest, everyone on board was still alive, with the possible exception of the right front seat passenger, but some were badly hurt; three seriously. The passengers weren’t prepared to spend a night in the mountains exposed to the cold rain, and luckily, they wouldn’t have to.
After learning about what emergency location devices can do for you, the operator of this particular Beaver had installed two methods of locating a downed aircraft; a proprietary system called Spidertracks and a 406 mHz Emergency Locator Transmitter, or ELT. The airplane hit the trees at 3:31 PM that day. By 3:47, 16 minutes later, the Coast Guard was activated, and at about the same time, the people at the aircraft’s base were receiving the bad news from Spidertracks. The chief pilot grabbed an airplane and headed to the accident coordinates. Meanwhile, the Coast Guard launched their HH60 to the scene. The Coast Guard spotted a broken-off tree in the dense forest and hovered above to take a good. They couldn’t see the airplane from above, but the pilot was seen in a nearby clearing waving an orange bag. At 6:16 PM that day, a Coast Guard rescue swimmer was lowered through the trees to rescue 6 out of the 7 people aboard the aircraft, rushing the seriously injured passengers to the nearest medical facility in Petersburg. One person with pre-existing medical issues who was seated up front died. Possibly due to his seat being ripped loose, although that side of the airplane took the brunt of the impact. The rest of them survived, including two cruise ship passengers who were not dressed for a night out in the cold and had very serious injuries as a result of the accident.
The temperature reported at Petersburg that afternoon at the time of the accident was 54 degrees, with a dew point of 48. There was a broken layer reported at 1,300 feet and scattered clouds at 500. We will never know what would have happened if they hadn’t been rescued that evening, but the temperature dropped into the 30’s that night, the clouds continued to lower, and the rain continued. Hiking out to tidewater might have been a possibility, but it would have been about 2 miles through rugged terrain, not something the injured cruise ship passengers could most likely have done. Given the combined effects of shock, the injuries sustained, and hypothermia, at least two of the passengers might not have survived the night.
Without a fairly precise GPS fix, locating the downed aircraft in the trees would have been very difficult. Fortunately, the Spidertracks GPS track showed the aircraft’s flight path into the canyon. The 406 ELT showed a fairly precise fix on the location. Combined, this dramatically limited the search area.
In addition, both the 406 ELT and the Spidertracks system alerted people as soon as the accident occurred. If it had waited until the aircraft was expected to be back at base, the search would not have begun for at least two more hours. By that time, the weather would have further deteriorated, and night would have been close at hand. Combined with the larger search area and the terrain, the likelihood of them being found before nightfall is remote if the aircraft had not been equipped as it was.
The difficulty of locating a downed aircraft in a dense forest is hard for some people to appreciate if you haven’t been on the ground with that in mind. As you can see from the photo of the Coast Guard HH60 taken from near the accident site, you can only see down from overhead in a very limited angle. The aircraft was not visible from above. That means that if you are trying to cover a large search area, you have to fly relatively fast. The time window looking through the forest canopy when you can see the accident is very short. In addition, the grid for the search pattern has to be pretty tight.
As you can see in the picture from Google earth that shows the locations of the Spidertracks fix and the 406 mHz ELT fix, the search area was pretty limited. In addition, the ceiling at the time meant that the airplane was not likely above 2000 feet and had to be somewhere in the valley. Even with that information, a company pilot searched the area once before the Coast Guard arrived and did not see the airplane. He was flying a faster fixed-wing airplane, so it’s likely that his scan pattern just did not happen to fall on the broken-off tree that was the clue the Coast Guard used to locate the aircraft. Without the ability to hover, it is also possible that even if they had seen the broken off tree, they might not have been able to see the aircraft, as you can see in the picture from the site.
By all accounts, the pilot just made a mistake that day. He had nearly 5,000 hours and over 100 in the last 90 days. He was current, had a valid medical, and was flying within limits that day.
The aircraft was not equipped with a stall warning system. It may or may not have prevented the accident, but at least it would have had a shot at it. There are some people that object to them because they scare the passengers or if they aren’t adjusted correctly, they can come on too early. Wiring the horn to the pilot’s headset only is one way to solve the passenger concern, and we have ways of solving the false warning issues as well.
In the end, this accident was the result of human errors. While we always try to reduce the number of those that occur, humans still design airplanes, maintain them, and fly them. With the benefit of hindsight, we know mistakes will occur. In this case, it is quite likely that at least two people survived because they had a 406 ELT and a Spidertracks system in the airplane. An investment of a few thousand dollars paid off in two lives being saved, and that is priceless.