On short final, the aircraft caught a strong downdraft and slammed into the runway, seriously damaging the airframe. Fortunately, neither the pilot nor his two passengers suffered injuries. The pilot may not have realized how fortunate he really was.
Where Trouble Brews
Even when they're widely scattered, thunderstorms are a force to be reckoned with. Starting life as a puffy cumulonimbus, the moist, unstable air of a developing thunderstorm rises rapidly, cooling to the dewpoint and beyond. As the storm develops, it carries precipitation above the freezing level, where it forms ice particles.
Friction between ice particles creates static electricity, and the storm becomes polarized as the charged particles separate. Hail can form as the particles fall, collect more moisture, and then reenter the updraft. As the thunderstorm enters the mature stage, precipitation falling through the rising column of air eventually reverses the flow to form a downdraft. The cold air gushes from the bottom of the storm, forming a gust front miles ahead of the approaching monster.
During the thunderstorm's life cycle it cooks up a maelstrom of virtually every form of hazardous weather. Updrafts, downdrafts, and icing can exceed the performance capabilities of any aircraft. Wind shear can tear wings from fuselage. Damaging hail can be thrown 20 miles or more ahead of an advancing thunderstorm, with severe turbulence extending equally as far. Lightning strokes lash out with up to 30 million volts and 100,000 amps - enough energy to light up a small city, let alone fry an aircraft's electrical system or ignite a fuel system. The pilot who is unfortunate enough to get caught up in the torrent usually has more at stake than just a hard landing and bent airframe.
The pilot of a Cessna T210 and his passengers found that out. Conditions were VFR in Albuquerque, New Mexico (ABQ), for their May afternoon pleasure flight, but trouble was brewing all around. The ABQ Low Level Wind Shear Alert System (LLWAS) issued numerous wind shear alerts in all quadrants, virga prevailed in all directions indicating the potential for microbursts, and the westerly wind was 17 gusting to 37 knots under a 6,000-foot broken ceiling. Cumulonimbus clouds were reported northwest, and thunderstorms were boiling up to the northeast and south.
The pilot attempted to land at Coronado Airport (4AC), some six miles north of ABQ. During its landing flare, the aircraft hit some nasty wind shear and the pilot shoved the throttle forward for a go-around. The airplane pitched, rolled, then slammed nose-first into the ground in a right bank. There were no survivors.
Night Lighting
Thunderstorms can be even more insidious at night than during daylight. Except for the lightning flashes slicing through the blackness or casting an eerie glow inside the mass of gray, thunderstorms and the hazards they represent are virtually invisible at night. Without weather radar or a lightning detector, pilots have no idea where thunderstorms may be lurking - or how fast they're moving. A single flash may cause the pilot to lose his night vision and be left to fly virtually blind. The battle against fatigue only makes matters worse for pilots fighting to guide their aircraft through the storm-pocked night.
And so it was that the odds were stacked against another pilot. The weather was rapidly deteriorating in the night sky over Binghamton, New York (BGM). Building thunderstorms gushed heavy rain, with bone-shaking turbulence and wind shear. Nearly blinded by the lightning, the lone pilot of a corporate twin-engine Cessna T303 struggled to stay at the instrument approach's MDA (minimum descent altitude) as his instruments slam-danced erratically in front of his eyes. Suddenly the aircraft dipped down, clipping trees along the approach path. The pilot shoved the throttles forward for a go-around and, miraculously, maneuvered for a safe landing.
First (and Final) Lesson
Good visibility with high scattered and broken clouds can lead pilots to believe that all is well, but there's much more to the brewing severe weather picture. Gusty winds and turbulence are a sure sign of demanding conditions. Combining high temperatures, high altitude, and low horsepower adds a high-density-altitude element. If a high temperature/dewpoint spread and virga are present - prime conditions for the development of microbursts, the danger increases. It's difficult to understand why a pilot would consider flying on such a day, but, unfortunately, this one did.
Over Denver, Colorado, the clouds were 12,000 scattered, 14,000 broken, with 70 miles visibility. It was a hot July evening, and at 7 p.m., the temperature was still a stifling 97?F. The density altitude at Jeffco Airport (BJC) hovered near the 10,000-foot mark, with winds blowing out of the northwest at 14 knots, gusting to 33. Thunderstorms rumbled through the area, and virga was reported in all quadrants.
The pilot had never flown a Cessna 150, and the ink on his instructor certificate was still wet. Still, the hot July evening must have seemed right for giving his first dual flight lesson. The 150 departed BJC and clawed skyward. Not long after it took off, witnesses saw the aircraft apparently making an approach to a large, empty parking lot. The pilot aborted the approach, and the aircraft skimmed over the crest of a hill where it slammed into the ground, the victim of a microburst. There were no survivors.
Deciding to Wait
At times, we all feel the pressure to fly. Business trips, family trips, get-home-itis, or an important flight lesson can skew our judgment. But the weather doesn't care about our decisions or our priorities. Especially when thunderstorms and microbursts are a potential part of the weather picture, the decision to wait is often the only safe course of action.
Thunderstorm and Microburst Avoidance Tips
Always get a thorough weather briefing before flying, even for a local flight. Pay particular attention to AIRMETs and SIGMETs, and think about rescheduling your trip if thunderstorms are in the forecast.
While en route, get updated weather from Flight Watch (122.0 MHz), HIWAS (Hazardous In-flight Weather Advisory Service, available through those VORs marked on sectional charts with a darkened square in the lower right corner of the frequency box), and automated systems such as AWOS, ASOS and ATIS (frequencies are listed with airport information on sectional charts.) Also listen to ATC for reports from other aircraft and warnings of hazardous weather and wind shear.
Virga, which is rain that evaporates before reaching the ground, can be a signpost of severe weather. When the temperature is above 80?F and the temperature-dewpoint spread exceeds 50 degrees, falling precipitation coupled with evaporative cooling can trigger a microburst.
The external appearance of a thunderstorm does not necessarily correlate to its severity, and all thunderstorms represent a serious threat to flight safety. When flying, remain at least 10 to 20 miles from any thunderstorm.
Lightning strikes can occur in the clear air surrounding thunderstorms. Strikes are most likely to occur at altitudes where the temperature is between 5?C and minus 5?C (41 to 23?F).
When thunderstorms and related weather is brewing, don't be fooled into thinking that safety lies in the traffic pattern. Rapid wind changes, turbulence, and wind shear can be most dangerous for an aircraft operating close to the ground. If possible, be on the ground well before weather conditions deteriorate, or divert to another airport.
If you must land in gusty, turbulent conditions, carry extra airspeed on final approach (generally half the gust factor) and think about using less than full flaps for landing.
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