Weather Hazards

When the subject of in-flight hazards comes up, non-pilots think of the kinds of things that one might see in a 1970s Hollywood blockbuster--- explosions and hijackings and volcanoes. The truth is far less dramatic and far more insidious. For small planes, anyway, the things that cause flights to come to harm are usually associated with acts of nature, things like thunderstorms and thick clouds. And almost always, it takes a pilot not paying attention, not giving nature proper respect or flying into weather they're not trained for, sometimes in planes not outfitted to fly in the condi- tions. That said, the most dangerous hazard to the safety of flight is the one packing the least punch, cloud cover. The most lethal hazards, such as microbursts and hail, are ones associated only rarely with accidents, perhaps because pilots can't help but be impressed with the power of the storms associated with these phenomena and, therefore, give them a wide berth.

Annual Lethality Of Weather-Related Accidents: 74%

Private Pilot Involved: 66%

IFR-Certified Pilot Onboard: 52%

Most Fatal: VFR into IMC

Percent Of Fatalities Attributed: 25

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Seconds It Takes IFR Pilots Become Oriented In IMC: Up to 60

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Average Seconds It Takes VFR Pilots To Lose Control: 178 Common Results: Graveyard spiral, structural failure, uncontrolled flight into terrain

Safest Action When Faced With Unexpected IMC: 180 turn

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Second-Deadliest Weather-Related Hazard: Icing

Most Commonly Encountered: Ahead of a warm front

Miles From Front's Surface Position Icing May Occur: 200

Hazards To Aircraft: Reduced performance, loss of lift, altered controllability

Cloud Types Associated: Cumuliform, Stratiform

Temperature Range Structural Ice Forms: -4Â°F to 32Â°F

Typical Cause: Freezing rain

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Weather Event Producing Most Hazards: Thunderstorms

Cloud Type Associated: Cumulonimbus (Cb)

Cb Characteristic: Flat, anvil-like top

What Creates The Shape: Wind shear near tropopause

Average Base Altitude Of Clouds: 700-10,000 ft

Top: 39,000-69,000 ft

Greatest Hazards: Extreme turbulence, hail, powerful up- and down-drafts, microbursts

Temperature Hail Formation Occurs: Up to 68Â°F Miles A Thunderstorm Can Launch Hail: 20 Safest Distance To Fly From Storm: >20 miles Distance Severe

Turbulence May Occur: 25 miles

Altitude Typically Encountered: 12,000-20,000 ft

Potential Altitude Displacement: 2,000-6,000 ft

Possible Impact To Aircraft: Structural damage

Miles Downbursts May Occur From Storm: Up to 15

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Average Cross Section: 2-5 miles

Wind Shear Component: 6 kts/sec over 16 seconds

Aircraft Able To Counter Such Speeds: None

Localized Downburst: Microburst

Cross Section: 0.5-2 miles

Horizontal Wind Speed Range: 45-90 kts Potential Vertical Speed: 6,000 ft/min