Helicopters often crash.

Between January 2002 and January 2005, 55 EMS aircraft accidents resulting in 54 fatalities and 18 serious injuries occurred in the United States. This is an average of 2 casualties a month.

EMS helicopter operations have increased from 162,000 to in 1991 an estimated 300,000 in 2005.

Between 2000 and 2005 10% of all medical helicopters crashed.

Fatal Medical Helicopter Crashes - detailed interactive chart from the Washington Post.

EMS helicopter accident rate has also increased in recent years prompting the National Transportation Safety Board to conduct a review and make additional safety recommendations.

Circumstances of some of the accidents demonstrate that adverse weather conditions are often key factors in EMS helicopter accidents. There are often foggy conditions around San Francisco General Hospital.

Pressure to take off, complete a mission, weather, nighttime flight, spatial disorientation resulting from lack of visual cue, and pilot training and experience were all identified as risk factors by the National Transportation Safety Board [NTSB].

In the past 2 years there have been hospital helicopter crashes on or near helipads in many cities including Dallas, Fort Worth, Cleveland and Olympia Washington.

San Francisco General Hospital wants to place helipads atop hospital buildings - an inherently dangerous proposition in earthquake country.

SFGH is located in a densely populated neighborhood mainly comprised of wood frame buildings.

EMS helicopters require an optimal landing and takeoff glide path of 1000 ft. This would place obstacles in their path, not the least of which is Potrero Hill.

Some helicopters have provisions to dump fuel, in an emergency, causing a hazard to neighborhoods below.

San Francisco Police stopped using helicopters after fatal accidents.

Read more articles about fatal medical helicopters crashes across the country.