by David Jack Kenny
The inherent limitations of light aircraft limit their usefulness for travel. Money cures a lot of this, of course. More power and approved de-icing can make climbing through the freezing layers a realistic strategy. Once you’ve worked up to turbine power and a pressurized cabin, holding a comfortable altitude over mountains is no longer much of an issue; add in on-board radar, and far fewer flights should need to be scrubbed for weather. But there will still be stuff you can’t climb over and don’t want to try to plow through. The airlines do everything in their power to keep their 200,000-pound jets out of thunderstorms. Why try your luck, even in a 12,000-pound turboprop?
Just before 11 a.m. on Oct. 26, 2009, a King Air B100 took off from Uvalde in south Texas, headed for Leesburg, Fla. Forty-five minutes later it broke up inflight, killing the four men on board. Radar track data showed that the aircraft entered an area of “very intense” to “extreme” precipitation echoes less than three minutes before contact was lost at 22,200 feet. The main wreckage was found in a 30-foot impact crater; only the foliage immediately overhead had been damaged, suggesting a near-vertical descent. Other parts of the airplane, including the outboard sections of both wings, were discovered almost a mile away.
There’s no doubt the pilot knew the weather was going to be difficult. He’d called flight service three times between 7:30 and 10 a.m. Early in the first call, he mentioned that, “We were going to leave about noon but we’re thinking about bumping it up with all of this weather moving into southwest Texas.” The briefer replied, “Well, you waited too long…. The front has moved into the area with the leading edge of thunderstorms and rain showers pushing across the area, and it’s just going to increase.” He went on to describe a series of convective sigmets for a line of thunderstorms 35 to 40 miles wide extending from western Arkansas past Corpus Christi. The cold front producing the storms was forecast to remain almost stationary throughout the day, and new storms were building behind the initial squall line.
The pilot’s next question revealed something of his frame of mind: “Is that line pretty solid, or can we pick our way through it?” The briefer replied, “No, it’s solid…. You’d have to get out ahead of it. That’s why I say you kinda missed your opportunity….” The King Air pilot, however, was not easily discouraged. He repeated that question, with slight variations, when he called back at 9 a.m. and again an hour later. The answer was just about the same both times, but on the second call he filed a flight plan for a route intended to take him through what appeared to be the narrowest part of the line. At 11:05 a.m., he checked in with Houston Center as he climbed from 10,200 feet to his assigned altitude of Flight Level 230 and told the controller, “If you don’t mind helping us, we’re looking at the radar--it might be better for us to go down toward Laredo … looks like a squall line.”
The controller answered, “Yes, there is a very significant squall line between you and your destination,” but then added, “Not sure how you’ll get through, but we’ll work on it somehow.” The pilot replied “All right. I sure appreciate the help.”
At 11:07 a.m., the pilot requested a turn south toward Laredo, which was approved. The King Air was cleared to climb to FL250 at the same time. Fifteen minutes later, its pilot contacted Houston with a request:
“We’re looking at a hole … going toward Corpus. Is it possible we can get about a one-five-zero-degree heading [to] try to work through that hole before it closes up?”
The controller cleared him to “fly heading of one two zero, when able proceed direct Corpus Christi, rest of route unchanged.” Radio transcripts show that the controller was working at least 23 other flights during this time, mostly airliners requesting weather deviations. Eighteen minutes passed before he asked the King Air to “verify you’re level at flight level two five zero.” The pilot replied, “No, sir, we had dropped down…. We had gotten into some pretty good turbulence. We’re at two four zero.” Less than two minutes after that, according to the NTSB report, “…an expletive and propeller noise were heard on the same frequency used by the pilot, and for the next 35 seconds there was sound similar to that made by a stuck microphone conflicting with other transmissions.” The airplane disappeared from radar less than 30 seconds later at a descent rate that peaked in excess of 40,000 feet per minute.
Beyond the raw fact of a King Air breaking up in flight, several aspects of this accident are unusual. The pilot’s logbooks were never recovered, but his most recent medical application--submitted some 21 months before the accident--listed only 550 hours of flight experience. His filed altitude of FL250 was close to the King Air’s service ceiling, but put him smack in the middle of the deck; pilot reports from airliners nearby put the tops at FL365. While he had on-board radar, it’s not clear that he had the operational experience needed to recognize its limitations and interpret it correctly.
Even more unusual was that the NTSB took the step of citing the controller for “failure to provide adverse weather avoidance assistance.” During the investigation, he insisted that he’d seen a gap in the precipitation in the same direction suggested by the pilot, but no such gap was apparent when the investigators replayed the tapes. Whatever he saw or thought he saw, the discrepancy illustrates the inescapable responsibility of being pilot-in-command … and serves as further proof that for most of us, thunderstorm avoidance should be a strategic rather than merely a tactical goal.