After the Accident: Twin Otter Crash In The Rockies From 40 Years Ago

After the Accident: Twin Otter Crash In The Rockies From 40 Years Ago

This month marks the 40th anniversary of the December 4, 1978, crash of Rocky Mountain Airways Flight 217 in snow-covered terrain at 10,530 feet MSL near a place called Buffalo Pass, about 8 nautical miles east-northeast of Steamboat Springs, Colorado. The de Havilland DHC-6-300 Twin Otter had 22 on board: the captain, first officer and 20 passengers, including an infant. All 22 survived the impact. One woman died in the wreckage about four hours later. The captain died of his injuries at a hospital some 70 hours after the accident.

The dynamics of how the plane hit, the snow covered terrain on which it went down, its structural integrity, the use of survival skills, and rescuers being able to locate and reach the remote crash site combined to create not what many view as a tragedy, but what’s been characterized by those directly affected as a miracle.

The long-ago event has been kept alive by many of those who survived or were swept up in the accident’s aftermath. Survivors and rescuers held a 40th reunion in Steamboat Springs late this past September. The event included a memorial observance, socializing and reliving their shared experiences. Their interest largely rests at the emotional level, quite different from the fact-gathering undertaken by the NTSB for its report issued on May 3, 1979, which is the official version of what happened and why.

Among those active at the local level in keeping alive the story of Flight 217 was one of the first to arrive at the crash site, TV news cameraman Tom Baer, who was with KBTV Channel 9 in Denver. At about 8:45 p.m. on December 4, Baer, who covered Western Colorado for the station, got a phone call alerting him that a Rocky Mountain Airways plane was missing somewhere near Steamboat Springs. Baer told me that it took him almost four hours of driving in a blizzard from his home in Glenwood Springs to reach the town of Walden, where search and rescue crews were already organizing. They went on to set up emergency medical treatment facilities in a campground about 16 miles outside of town. It wasn’t until about 7:45 on the morning of December 5 that the first Sno-Cat with emergency medical personnel, on which Baer had gotten a ride, reached the crash site a dozen miles into the wilderness.

“The miracle was just finding the plane,” Baer told me. “At one point, the rescuers stopped and turned off the engines on the Sno-Cats and snowmobiles and were able to hear people screaming,” he said. In the film he shot, one of the Twin Otter’s landing gears can be seen sticking up, while further back in the image the main cabin area is seen covered in snow while fresh snow continues to fall. On the soundtrack, rescuers can be heard warning each other to be careful of sharp objects as they help maneuver injured passengers out and onto waiting stretchers. “The white plane, on its back in the snow, would never have been sighted from the air,” Baer said.

According to the NTSB, the accident was due to severe icing and strong downdrafts associated with a mountain wave, which combined to exceed the aircraft’s capability to maintain flight. Contributing to the accident was the captain’s decision to fly into probable icing conditions that exceeded the conditions under which the company authorized flights to take place.

The twin-engine high-wing airplane was powered by Pratt & Whitney PT6A-27 engines, workhorses for turboprop aircraft. The airplane had logged 15,145 hours in service. The left engine had 6,137 hours since overhaul, while the right engine had 6,829. Post-accident examination failed to find anything wrong with the engines. The avionics were what you might expect for the time: two VOR receivers, an ADF receiver, a DME and two VHF transceivers. The DME had been removed for service, and both of the airplane’s radio magnetic indicators were placarded, “ADF needle on RMI sticks.”

The airplane was equipped for flight into known icing with pneumatic deice boots on the wing and horizontal stabilizer leading edges, electrically heated props, electrically heated windshields, electrically heated pitot tubes and deflector shields on the engine air intakes.

Investigators determined that the aircraft’s weight at the time of the accident was about 11,500 lbs., about 1,000 lbs. below gross, and the center of gravity was within limits.

The captain and first officer reported for duty at Denver’s Stapleton Airport (KDEN) at about 12:30 p.m. Mountain Standard Time on the day of the accident. They departed on Flight 212 to Steamboat Springs (KSBS) at about 2:22. The first officer performed some duties you’d expect to be handled by a flight attendant, such as doing the passenger safety briefings. Because of winds, especially downdrafts, they were unable to climb above the mountains west of Denver and had to return. The aircraft was refueled and the airplane and pilots subsequently flew out as Rocky Mountain Airways Flight 216 to KSBS.

The direct flight distance from KDEN to KSBS is about 108 nautical miles, actual routing somewhat longer. But, because headwinds at the cruising altitude of 17,000 feet were about 100 knots, the flight took almost two hours.

The captain advised Denver Center of their arrival at the uncontrolled airport in Steamboat Springs at about 6:21 and reported that they encountered heavy icing, mostly rime ice, in the KSBS area between 15,000 feet and 10,000 or 11,000 feet. He subsequently reported to a company dispatcher that the flight was relatively smooth and that they had encountered the heavy icing. He suggested other flights could make it into KSBS without difficulty but suggested they stay above the clouds until over the area and then descend. He filed an IFR flight plan for the return flight to Denver, which would be Flight 217.

The first officer told investigators that while they were on the ground at KSBS, he and the captain removed about 3/4 inch of ice from the front parts of the airplane that did not have ice protection. They did not treat the airplane with deicing fluid.

The Mountain Airways station agent at KSBS said that light precipitation was falling while the airplane was on the ground, and it froze as soon as it came into contact with the ramp surface. The station agent said that the weather included an overcast ceiling at about 2,000 feet, visibility 6 miles and calm wind. The agent put 75 gallons of jet fuel into the airplane, refilled the oxygen tanks and helped board the passengers.

At 6:55:57, the captain of Flight 217 radioed Denver Center that they had departed KSBS and were climbing to the assigned altitude of 17,000 feet MSL. The first officer was flying.

The first officer, age 34, held an ATP certificate. His first-class medical was current with no limitations. At the time of the accident, he had 3,816 hours with 320 in DHC-6 airplanes.

The captain, age 29, also held an ATP certificate. His first-class medical also was current with no limitations. He had been a DHC-6 captain at Rocky Mountain for about three years. He had 7,340 hours with 3,904 in DHC-6 airplanes.

The first officer said that he flew the published departure procedure and, after climbing to cross the Steamboat Springs non-directional beacon (NDB) at 12,000 feet, intercepted airway V101 headed eastward. He said they picked up some light freezing precipitation during the climb, but eventually he could he could see the moon and stars until entering clouds at 12,500 feet over a mountain ridge in the Buffalo Pass area. He continued climbing until reaching 13,000 feet, at which point the airplane would not climb at a normal power setting and airspeed. The captain then took the controls but also could not get the airplane to climb. The minimum en route altitude was 16,000 feet. By now, well inside the clouds, the airplane was picking up severe icing. The captain continued handling the flying.

The first officer said the airplane’s deicing equipment was working as expected and ice was being shed from the protected areas. He said at times it was like “slush.”

At 7:14:41, the flight radioed Denver Center that “…we’re going to have to return to Steamboat.” The controller asked, “Rocky Mountain 217, what’s your position now?” The reply, “…we’re on the…340 radial of Kremmling (VOR), on the north side.” At 7:15:03, the Denver Center controller cleared the flight to return to KSBS. The response could not be understood, and the controller transmitted, “Rocky Mountain 217, proceed direct Steamboat at your discretion and let me know, what’s your altitude now?” The response was “13,000.” The Denver Center controller then said, “Rocky Mountain 217, roger, change to advisory frequency is approved, report your cancellation or ground time on this frequency or through dispatch.” No reply to that transmission was heard.

The controller then telephoned the airplane’s station agent at KSBS to alert him that the airplane was returning. The station agent said that about 5 minutes after that, the flight radioed him that it was returning due to heavy icing and warned that other flights should not try to fly into Steamboat Springs.

At 7:19:47, the controller radioed, “Rocky Mountain you still on frequency?” The response: “Yes, still here.” The replies from the flight to two additional transmissions were unintelligible.

At 7:39:54, the flight radioed, “…want you to be aware that we’re having a little problem here maintaining altitude and proceeding direct Steamboat beacon (NDB).” “Roger, what’s your position now,” the controller asked. “We’re on Victor 101 crossing the 335 (radial) of Kremmling (VOR),” they responded. The controller said, “Rocky Mountain 217, okay sir, can I give you any assistance?” “Not now,” was the reply.

The first officer said the captain was able to hold the airplane at 11,600 feet with 10 degrees of flaps extended and maximum power. He told investigators that they occasionally encountered a prestall buffet at around 85 knots. He said that they were able to maintain altitude with the airspeed at 90 to 100 knots.

The captain commented that they were at minimum obstruction clearance altitude and they “had it made.” But, did they? The ice on unprotected areas of the windshield was about 1-1/2 to 2 inches thick. The Safety Board believed that the captain was probably unaware that there was mountain wave activity immediately east of Steamboat Springs, and severe downdrafts were associated with that activity.

At 7:44:34, there was a transmission that the controller thought may have come from Flight 217. He tried to raise them four times, but there was no response.

The first officer said that the airplane entered more severe icing and began to descend at 800 to 1,000 feet per minute. He saw the ground about 1-1/2 seconds before impact, pushed the propeller levers all the way forward while putting in full flaps, and told the captain to turn to the right. Then, there was a bright blue flash followed by the airplane hitting the ground.

The blue flash was the right wingtip striking a high voltage power transmission line. A 10-foot section of the wing was sheared off. The lights blinked, and some went out in places fed by the high-voltage power lines running through the Buffalo Pass area. That electrical problem subsequently provided a clue to aid searchers, who initially were misdirected as to the location of the downed aircraft. There was an ELT installed on the Twin Otter. In addition, the first officer carried a portable one in his fight bag. An ELT signal from the crash site was received by a number of aircraft, one of which was a U.S. Air Force Reserve C-130. The crew of the C-130 believed they had pinpointed the origin of the ELT signal, but they were wrong, initially directing searchers toward a spot about 12 miles east-northeast of where the plane actually was. On the ground, a Sno-Cat operator, using a portable ELT direction finder, eventually identified where the ELT signal was coming from.

There were strong winds, snow continued falling and the temperature was well below freezing. Once the armada of Sno-Cats and snowmobiles arrived at the crash site at about 7:45 a.m., it took almost four hours to evacuate the survivors from the crash site to hospitals in Steamboat Springs and Kremmling, Colorado.

A 20-year-old passenger who had received survival training was instrumental in turning the wrecked aircraft cabin into a makeshift shelter for what would be the survivors’ overnight ordeal. The cabin lights remained on for a long time, and he and another male passenger raided the baggage compartment for warm clothing, which they distributed to other passengers. They removed seats to create more interior space. Less seriously injured passengers tended to the more seriously injured ones.

The Safety Board said that the cabin remained fairly intact because the impact forces were relatively low due to the airplane’s ground speed being only about 40 knots as it struck the terrain. Aside from being cushioned by fallen snow, the airplane did not directly impact rigid objects such as large-diameter trees.

The Safety Board noted that the pilot and first officer’s seats were not equipped with shoulder harnesses and their injuries, which became fatal for the captain, might not have been so severe had harnesses been provided.

For the 50 or so first responders who rode Sno-Cats and snowmobiles in miserable conditions for hours in order to carry out their mission, and the 20 survivors, the memories of 217 were complex, including terror and loss, but also had to be understood in the context of survival of a crash the likes of which few at first believed anyone would have survived. As pilots, the story of Flight 217 still matters if we learn from what happened 40 years ago in the frigid, stormy Rocky Mountains. It matters if we resolve to steer clear of the dangers that no pilot, however skilled, can overcome when faced with the multiple risks associated with severe winter weather.


Peter Katz is editor and publisher of NTSB Reporter, an independent monthly update on aircraft accident investigations and other news concerning the National Transportation Safety Board. To subscribe, visit www.ntsbreporter.us or write to: NTSB Reporter, Subscription Dept., P.O. Box 831, White Plains, NY 10602-0831.

The post After the Accident: Twin Otter Crash In The Rockies From 40 Years Ago appeared first on Plane & Pilot Magazine.

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