Aftermath: Too Much

There are limits, even in Alaska.

Aftermath Artwork

Aftermath Artwork

The Piper Super Cub is essentially a J-3 Cub airframe equipped with a few space-age refinements like flaps and an electrical system, and powered by a 150 hp Lycoming — in some cases a 160 or 180 — in place of the original's 40 hp Continental. Piper produced nearly 3,000 of them, many of which now live in Alaska. One of those came to grief in 2013 at the remote Tatitna Airport (8KA) in a way that incidentally sheds some light on how differently airplanes are used in Alaska than in the "Lower 48."

In a summer 2009 photograph on the site airport-data.com, the airplane appears showroom clean. A row of aftermarket vortex generators is visible on the upper surface of the wings, which have squared-off Dakota Cub tips. The tires are normal 600s, and skis are installed between them.

At the time of the accident, however, the airplane was configured somewhat differently. It had tundra tires, the oversize rubber doughnuts that allow airplanes to land on rock-strewn, rutted terrain. A rack of caribou antlers was lashed to the struts of the left wing and a rifle to the right. In addition to the 58-year-old pilot and his passenger, who between them weighed some 450 pounds, an estimated 500 pounds of butchered caribou meat was in the airplane. The tanks had been topped. National Transportation Safety Board investigators calculated the weight — "conservatively," they said — as some 640 pounds over the Super Cub's certificated gross of 1,750, with the CG some 5 inches behind

the aft limit.

The strip at Tatitna (it is also known as Rohn) is a public use airport, operated by the Bureau of Land Management, and is marked "Emerg Only" on the McGrath Sectional. At an elevation of 1,450 feet, 1,200 feet long and 12 feet wide, it is described in the AirNav.com airport listing as having a surface of turf and gravel "in poor condition" strewn with rocks up to 10 inches in diameter. It is surrounded by sparse but tall spruce trees. Located at the confluence of several river valleys and surrounded by mountains, it is subject to unpredictable wind shifts. Despite the unpromising description, however, it is practically luxurious by Alaskan bush standards, and is heavily used in late winter because it lies at a stop along the Iditarod dog sled race.

On the day of the accident, the pilot had made several trips ferrying his son and nephew to Tatitna from the back country, where they had killed two caribou. There he could load the airplane more heavily and would carry them, in two trips, to their home at Big Lake, about 110 nm to the southeast.

The pilot had originally intended to fly just the 500 pounds of meat to Big Lake on the first trip, but then decided to bring one of the men along to help him unload it. It was, according to the pilot's son, who remained behind, "a little windy," but the pilot elected to take off to the east, with the wind at his back. Normally a Super Cub would get off in a fraction of a 1,200-foot strip, and so the direction of the wind, as long as it were not too strong, would be unimportant. In this case, however, the airplane was very heavy, marginally stable if at all, and aerodynamically compromised by its external loads.

As the pilot's son watched from the west end of the strip, the little yellow airplane became airborne, barely cleared trees, banked to the left, rose and fell briefly, and then disappeared from sight beyond the far end of the strip. The engine sound ceased, and there was an explosion. Investigators found that the airplane had clipped a spruce tree at the 40-foot level and then descended steeply, coming to rest 70 feet from the foot of the tree. The wreckage was consumed by fire. The surviving passenger was unable to extricate the pilot.

The passenger told investigators that after they took off the pilot began to swear and said, "I should have taken off the other way." He could hear "panic" in the pilot's voice, and, realizing they were going to crash, he put his hands up to protect his face.

Under an old principle of English law, "dying declarations" — the utterances of people who are about to die — are presumed to be truthful. The pilot's statement that he should have taken off the other way may not qualify as a "dying declaration," but it suggests that sincere doubt about the direction of the takeoff may already have been present in his mind even as the airplane was accelerating.

It's possible that, had the wind swirled a little differently and a tree not grown where it did, the pilot and his passenger might have gotten away with no more than a bad scare. Maybe not. In any case, the crash/no crash dichotomy drains the complexities from a series of decisions that began as the airplane was being fueled and loaded.

The pilot had been flying in the Alaskan bush for many years and had probably seen all sorts of loadings, internal and external, in Super Cubs and comparable airplanes. In Alaska, published limitations mean little, and the FAA, trying to remain somewhere within earshot of the real world, has even created special approvals for external loads on airplanes never intended to carry them, although the infinite variety of those field improvisations hardly lends itself to regulation. The published baggage limit for the Super Cub is 50 pounds. Nevertheless, Super Cubs routinely carry a third person stuffed into the baggage space, and this pilot did not blink at putting 500 pounds of meat there. In the bush numbers mean nothing; experience is everything.

Guns are routinely strapped to wing struts and exact only a slight performance penalty, but the effect of the antlers is harder to estimate. The antlers of caribou — popularly known down south as reindeer — are second only to those of moose in size, and the previous owner of this set had been, according to his slayer, a large bull. Unlike those of deer and elk, but not to so great an extent as those of moose, the antlers of caribou include many broad, palmlike branchings whose aerodynamic characteristics have nowhere, I am pretty sure, been documented.

There were several options for reducing the weight and moving the CG forward. In any case two trips would be required. Why was it necessary to load as much as possible into the airplane for the first trip, leaving only a single passenger and some camping gear for the second? It seems as though the pilot could have taken the meat and no passenger; or some of the meat and one passenger; or both passengers and no meat, but the antlers; and so on. He could have made it back to Big Lake with half as much fuel as he had aboard and refueled there. If he was going to have a lighter load on the second trip, why not carry the gigantic airbrake of the antlers then?

What pressures the pilot may have felt, and to what extent his cool consideration of his options was mixed with impulsive decisions or a perceived need to hurry, we can't know. It seems, however, that the loading of the airplane — apart from being "improper," as the NTSB said, in a legal sense — was influenced by a sort of momentum, with one thing after another being added, as it were, as an afterthought.

Once the airplane had been loaded, it had only to get into the air. Taking off to the east required turning to avoid a 1,000-foot mountain a mile from the end of the strip. To the west, on the other hand, lay a broad, relatively treeless river bottom and gradually descending terrain: a better choice for an airplane that foreseeably might struggle to gain altitude. This was the last opportunity for the pilot to pick a more cautious alternative. He balanced all, brought all to mind — and didn't.

_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. _

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