NTSB says downdrafts probably killed adventurer Steve Fossett - dangers of clear air turbulence

July 9, 5:26 PMAirlines/Airport ExaminerJerome Chandler

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We now know what in all probability killed Steve Fossett, the 63 year-old adventurer whose small plane went missing September 3, 2007 in the rugged eastern stretches of California's majestic, sometimes malevolent Sierra Nevada Mountains.

The National Transportation Safety Board says Fossett’s Bellanca 8KCAB-180 inadvertently encountered “moderate turbulence and downdrafts of at least 400 feet per minute.” In its Probable Cause finding the Safety Board goes on to say, “The magnitude of the downdrafts likely exceeded the climb capability of the airplane.” At the altitude Fossett was flying, he could climb at only 300 feet per minute.

NTSB’s report says the Bellanca was on a northerly heading when it hit mountainous terrain at about 10,000 feet. Ground scars and heavily fragmented wreckage indicate the aircraft hit particularly hard, and “was traveling at a high rate of speed…right wing low, near level pitch attitude.” Fire consumed the wreckage, and the Bellanca’s emergency locator transmitter—or ELT--was destroyed.

That’s why it took so long to find the the airplane. Fossett’s disappearance launched one of the most intense searches in the annals of aviation. After a month of futile looking, the Civil Air Patrol suspended its search. A year later, a hiker found some of the adventurer’s personal effects, and the scorched remnants of the ill-fated Bellanca were discovered a half-mile away.

While clear air turbulence (turbulence not associated with thunderstorms) can wreak havoc on smaller private aircraft, under certain conditions it can also being down four-engine jets. That’s what happened March 5, 1966 near Gotemba, Japan. A BOAC (the predecessor of British Airways) Boeing 707 had just taken off from Tokyo Haneda Airport headed for Hong Kong. The day was exceptionally clear for Tokyo, and that should have been a warning. Winds of 60 to 70 knots were cascading over majestic Mount Fuji when the big Boeing—flying at 15,000 feet--was pummeled by ferocious downdrafts, downdrafts spawned by what’s called the “mountain wave” effect. Winds hit the flanks of mountains, crest the summit, and then tumble over the other side. Given winds of sufficient force, anything caught in the path of this kind of CAT (clear air turbulence) can be in serious trouble.

All on 124 souls on board BOAC Flight 911 perished that startlingly clear day. We get a glimpse of the terror the passengers must have felt as the craft came apart. One of them was shooting movie footage out the window when CAT hit.

Passengers traversing the Rocky Mountains when winds are high can often get a far tamer taste of clear air turbulence, this as winds from the west crest the rugged range, and ripple over the other side. You can feel the power of the penumbra of mountain wave effect even at cruise altitude, up at 35,000 feet. Such less than close encounters of a far kind engender an awe-inspiring, sobering respect for the unbridled power of Mother Nature.

Photos of Steve Fossett and BOAC Boeing 707 courtesy Wikipedia