After finishing my day of instructing at a flight school owned by a large regional airline in Farmington, New Mexico, I volunteered for a flight to the Beech factory at Salina, Kansas, to pick up parts at for a grounded airliner. We were to leave well after dark and, according to my weather briefing, the flight would include instrument conditions for much of the route. One of my close friends, also just finishing a day of instructing, volunteered to come along.
As I preflighted one of our Beech Barons, I reflected on how lucky we were to be flying for a school that gives multiengine training in known-ice-certified, radar-equipped Barons that are less than five years old.
As we neared the Kansas border on the way over, we checked with flight service for a weather update. Flight service asked whether we had the new airmet for moderate icing in the Salina area. We didn't, since nothing had been issued before our departure. Fortunately, we overheard a few corporate pilots report only a trace of icing during their approach to Salina. Because we were only about five minutes behind the last aircraft, we accepted the ILS for Salina's Runway 35. As we descended smoothly down the glideslope, we did indeed pick up light icing and cycled the deice boots near decision height, mostly for entertainment rather than for a significant accumulation of ice. The fatigue from a long day of instructing and the late night trip at high altitude was beginning to show as we forgot to turn on the pilot-controlled lighting until only 100 feet above decision height. Probably because of the fatigue we took this in good humor instead of as the warning that it should have signaled.
After retrieving our cargo in Salina, we climbed easily through the tops of the clouds and picked up only light ice. We requested and received a heading direct for Santa Fe, New Mexico, because we favored the lower minimum en route altitudes (MEAs) that this route provided. We figured that at the higher altitude the reduced power of our normally aspirated engines might hamper our ability to cope with any significant amount of ice that could accumulate if we entered the clouds.
As we neared Santa Fe, the controller offered us a vector toward Farmington. Thinking that we could remain above the clouds at 14,000 feet, we accepted the vector rather than diverting south to remain at lower MEAs. As we crossed the mountains between Santa Fe and Taos, we noticed the tops of the clouds slowly getting closer to our altitude and requested 15,000 to stay above them.
The tops of the clouds continued to rise, however, and eventually we found ourselves flying through the top of a very cold stratus layer. The ice began to accumulate almost immediately. It did not take long before the added drag slowed us to the minimum icing speed of 130 knots, which is supposed to keep the angle of attack low enough that ice does not form on the bottom of the wing behind the boots. We requested to return to 13,000 feet to get more power out of our twin Continentals, but Albuquerque Center advised that the minimum altitude was now 15,000 feet and would remain so for another 30 miles. The speed continued to decrease, forcing us into a slow descent to maintain 130 knots indicated. The ice was now nearly one-half-inch thick and we actuated the boots. The outboard sections of both wings beyond the landing lights did not shed the accumulated ice, even after we cycled the boots a second time.
We were able to hold altitude about 500 feet below our assigned altitude until the ice began to accumulate again and we were forced to drift down to maintain sufficient speed. We continued this process of cycling the boots, leveling off for a short time and then drifting down as the ice formed again. We were at only 13,500 feet (well into the 2,000 feet of terrain separation provided in mountainous areas) when the controller was finally able to assign us 13,000 feet.
The ice continued to form, and there were now grotesque horn-shaped formations projecting six to eight inches in front of the spinners and the engine air intakes, and three to four inches on the outboard wing sections. The ever-increasing drag continued to pull us down until we were drifting below our assigned altitude of 13,000 feet. The tension in the aircraft was punctuated by the staccato sound of ice being flung off the props and slamming into the fuselage. After another five minutes, which seemed to stretch to eternity, we were cleared to 11,000 feet, where we finally were able to stop our drifting descent. The ice was not forming nearly as fast as it had been, and with the added power at the lower altitude, we maintained 11,000 until terrain allowed us to descend below the freezing level.
Shaken, and extremely glad to be safely on the ground again, we agreed that we had learned some important lessons through a graduate course in the school of hard knocks. Never had we encountered icing that we could report as more than moderate; and although we had an extremely capable aircraft certified for flight in known icing conditions, it did not automatically mean that the airplane could handle all weather conditions. A wiser course of action may have been to continue on the airways, which would have afforded us lower MEAs and more altitude choices. That flexibility may have allowed us to descend safely — or perhaps avoid the icing conditions in the first place.
Steve Keller, AOPA 1098126, of Boise, Idaho, is a first officer for Horizon Air and flies a Fokker F28.
"Never Again" is presented to enhance safety by providing a forum for pilots to learn from the experiences of others. Manuscripts should be typewritten, double-spaced, and sent to: Editor, AOPA Pilot, 421 Aviation Way, Frederick, Maryland 21701.
Related Articles
