In last month's Wx Watch (" Wx Watch: Icing Rules of Thumb," January Pilot) we discussed the issue of airframe icing. After all, in most pilots' minds, ice is the winter weather nemesis. The tactics for dealing with ice were mentioned in the abstract. Now it's time to look at two winter weather accidents that illustrate the specific ways in which many pilots run afoul of adverse winter weather.
Mooney M20K; Applegate, Oregon
This first case involves an instrument-rated pilot with 881 total flight hours and 479 hours in the Mooney M20K. At 8:45 a.m. on February 10, 1994, the pilot received an outlook briefing from the Hawthorne, California, Flight Service Station (FSS) for his proposed flight from the Los Angeles area to a stop at the Red Bluff, California, airport then on to Medford, Oregon — his final destination. m At 12:25 p.m. the pilot called this FSS again. This time he asked for, and received, an abbreviated weather briefing for his route. The briefing included winds aloft and terminal forecasts. The pilot declined an offer to hear information regarding airmets. If he had bothered to listen, he no doubt would have learned of icing conditions associated with a winter low and its cold front — both of which had just made landfall in northern California. m The National Transportation Safety Board (NTSB) accident report's next mention of the flight picks up the pilot in the Stockton (California) Approach Control airspace at 3:20 p.m. Approach control advised the pilot of a weather cell and issued vectors for the pilot to maneuver around it.
The pilot might have thought that the weather was improving, because 16 minutes later, when handed off to Sacramento Approach, he amended his next destination to Redding, California — some 30 miles north of Red Bluff. Then he was approved to leave the frequency so that he could contact flight watch. Flight watch gave the pilot news of a convective sigmet currently in effect for the Medford area, plus other weather information for the rest of the route.
At 4:22 p.m. the pilot changed his intermediate destination again — back to Red Bluff. After an uneventful landing in VFR conditions, the pilot went into the Red Bluff FSS and requested the Medford weather once more. An FSS specialist asked if he wanted a standard briefing, and the pilot said, "No, thank you." Then he was told of current reports of tornado and thunderstorm activity along the way to Medford, as well as flight advisories warning of icing, turbulence, mountain obscurement, and instrument meteorological conditions. The pilot said that he was aware of the weather conditions and would be talking to ATC while en route.
At about 5 p.m., he took off from Red Bluff in VFR conditions, bound for Medford. Once at altitude, he asked Oakland Flight Watch for cloud-top information for the area over the Siskiyou Mountains of northern California, but he was told that there was no top information. Then the specialist told the pilot of an airmet in effect for the northern third of California and the southern third of Oregon for light, occasional moderate rime and mixed icing in clouds and precipitation from 7,000 to 19,000 feet, with isolated areas of severe mixed icing. He was told that these conditions were expected to continue through the following day.
It must have been just a few minutes later that the pilot realized the first hints of potential trouble. We can reasonably assume that he was becoming concerned about the cloud tops around him, because he reported his altitude as 9,500 feet at 5:11 p.m., when he was north of Red Bluff. By then, he was in radar contact and receiving VFR radar advisories.
Then, after learning from controllers that the tops over Ft. Jones, California (62 miles northwest of Redding, and in the Klamath Mountains), were reported as being at 22,000 feet, he advised that he was climbing to 16,500 feet.
More concern was evidenced by the Mooney pilot's telling a controller at 5:17 p.m. that he would be diverting to a coastal route toward Crescent City, California, "with the possibility of spending the night," the NTSB report says.
But then came another change of mind. After being handed off to the Seattle Air Route Traffic Control Center, the pilot said that he was VFR at 12,500 feet and was heading for Eugene, Oregon.
Yet another change came at 5:48 p.m., when the Mooney pilot told Seattle Center that he was "?going to try to make it into Medford." He asked for vectors to Medford and said that when he got closer to the weather he'd ask for an IFR clearance.
Three minutes later, Center cleared the Mooney direct to the Rogue Valley VOR and told the pilot to maintain 12,000 feet.
If there were any suspicions that the Mooney may have been both in clouds and in icing conditions up to this point, they were erased by the pilot's transmission at 6:07 p.m. "We're picking up a little ice here," the pilot said. The NTSB report noted that the controller confirmed that it was rime ice.
From here on out, things went from bad to worse very quickly. One minute later, the pilot said that he was losing power. The pilot was informed first that the minimum en route altitude (MEA) for the Mooney's location was 10,000 feet, descending to 9,000 feet in one minute's flying time; and, second, that an airport ranch was at the pilot's nine to 10 o'clock position and 12 miles.
The pilot responded by saying that he was descending at 1,000 fpm and showing no power. Then he made a right turn.
At 6:11 p.m. the controller described the local geography to the pilot, told him to look for a lake, and instructed him to continue the right turn to go direct to the Rogue Valley VOR and lower terrain. The pilot said that he couldn't see anything, and at 6:12 p.m. said, "Yeah, we're stalled out now and going down." When asked if he was in instrument weather conditions, the pilot responded, "Affirmative."
He asked for vectors to Medford, but by 6:13 p.m. radar contact with the Mooney was lost. At 6:14 p.m., the pilot said that he was at 5,800 feet and had terrain in sight. He asked for help in clearing the terrain, but his controller told him that he had flown into a valley. At the time, Medford's surface weather was 2,200 feet scattered, 3,100 feet scattered, measured 5,500 feet broken, with a visibility of 15 miles, light winds, and cumulonimbus clouds in all quadrants.
At 6:17 p.m., the pilot said that he was "at 2,000 feet now in trouble here," an apparent reference to his altitude above the ground, because a few moments later he said he was at 4,700 feet. The last transmission from the pilot came shortly thereafter, when he said, "[unintelligible] I've got terrain."
The Mooney crashed at the 1,700-foot-msl level of a rock wall alongside a road that runs along the north side of Applegate Lake. The pilot was killed in the crash, and the NTSB established that the probable cause of the accident was poor in-flight planning and decision making, along with icing conditions. Contributing factors were listed as flight into known adverse weather, a dark night, and mountainous terrain.
Beechcraft V35B Bonanza; Lake Tahoe, California
At 9:19 a.m. on the morning of December 7, 1996, the 1,450-hour instrument-rated pilot called the Oakland, California, Automated Flight Service Station to obtain a weather briefing and file an IFR flight plan. The trip was to originate at Marin Ranch Airport in San Rafael, California, and proceed via the Skaggs Island and Squaw Valley VORs to Truckee, California.
The briefing included Airmet Sierra, which forecast the mountains east of Sacramento to have moderate turbulence below 18,000 feet, a freezing level at 9,300 feet, and moderate rime icing.
The pilot took off at 10:30 a.m., and at 11:09 a.m. the Oakland Air Route Traffic Control Center asked that the pilot climb and maintain a cruising altitude of 13,000 feet. The pilot responded with a request for the VOR-A approach to the South Lake Tahoe Airport — about 30 miles south of Truckee — and a request to descend to 11,000 feet. Apparently something made the pilot want to change both his destination and his altitude. Given the sequence of events that would follow, it's reasonable to assume that airframe icing was becoming a factor at this stage of the flight, if not earlier.
Center then asked the pilot to hold at the Squaw Valley VOR at 13,000 feet and to expect an approach clearance. Four minutes later, the pilot said that he was picking up light rime ice. The controller cleared the Bonanza to descend to 12,000 feet, but the pilot "advised?that he was unable to reach 12,000 and requested 11,000 feet," according to the NTSB report. Subsequently, the Bonanza pilot was cleared to 11,000 feet and told to take up a heading of 250 degrees.
Evidently eager to begin the VOR approach, the pilot at 11:18 a.m. asked Center for a 180-degree turn and to start the approach. A minute later, the pilot said, "I need a 180 immediately." After 16 seconds the controller approved these requests, and four seconds after that the pilot said that he was "out of the clouds now, but we're, ah, got a lot of ice."
The controller acknowledged and asked if the pilot wanted to start the approach. Seven seconds later, the pilot reported, "We're declaring an emergency and I'm going down." Six seconds later, the pilot acknowledged a heading issued him by the controller. That was the last recorded communication from the pilot.
At 11:23 a.m., another pilot in the area reported hearing an emergency locator transmitter for a short time.
The Bonanza crashed in the snow-covered mountainous terrain of the Tahoe National Forest. A post-crash investigation revealed that the engine was developing power at the time of impact and that the vacuum pump vanes that power the airplane's attitude and heading indicators were intact, along with the vane block. A post-crash fire destroyed the pump's spline coupling. The pilot — the sole person aboard — was killed on impact.
The NTSB ruled that the crash was caused by the pilot's intentional flight into adverse weather and his improper in-flight planning and decision making.
Analysis, lessons, and advice
The first lesson to draw from these accidents is an obvious one: Obtain a thorough preflight weather briefing. The Mooney pilot made a point of not listening to the icing airmet. The evidence suggests that he felt that learning about the weather once en route would be good enough. The Bonanza pilot appears to have been more conscientious in this regard. He not only received a briefing, he filed a full flight plan as part of the process. In any event, both pilots had information adequate to prepare themselves for the weather to come.
The second lesson is more of an admonition: Act on any icing information. Learning about ice is one thing. This means nothing if your plans don't reflect its impact. Neither pilot seems to have anticipated the chance of encountering ice.
Now let's look back to the survival guidelines mentioned last month. How did the pilots fare?
Not too well. We talked about the importance of assessing your airplane's ability to handle ice. Neither airplane was certified for flight into known icing conditions, neither had the kind of power reserves needed to climb above any ice-bearing cloud tops. The Mooney pilot seems to have tried to outclimb the tops rising around him — unsuccessfully. An ice-clogged engine induction air system may have stopped the engine. The Bonanza pilot simply barged on ahead, collecting ice as he went.
What about the rule having to do with staying in the clear? The Mooney pilot seems to have attempted to stay on top of clouds, but he eventually flew into them. The Bonanza pilot knew before takeoff that he'd be flying in clouds for most of his trip.
The rule about warm air below? The surface temperatures at Medford and South Tahoe at the times of the accidents were 40 and 43 degrees Fahrenheit, respectively. So there was a layer of warm air at the surface, but it wasn't thick enough to give either pilot any help during their descents.
What about having above-freezing temperatures at the MEA? There's no way that either flight could comply with that rule of thumb. Winter in the mountains at 10,000-plus feet? That's a guarantee of subfreezing temperatures aloft.
Did either pilot have an escape plan? It doesn't seem so. Both simply kept on flying as though nothing was wrong. Until, that is, it became all too obvious that they were in deep trouble. They didn't advise ATC of their predicaments until the very end and didn't take any evasive action at the first sign of ice. These were great examples of "get-there-itis" — a compulsion to continue a flight no matter what. The pilots may have been emboldened by previously successful flights in icing conditions.
Now a final question: What would you have done if you were in these pilots' shoes?
E-mail the author at [email protected].
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