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Nov
07
2013
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Posted 10 years 173 days ago ago by Admin
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Helicopter Emergency Medical Services And Weather Related Accidents
by Bryan Butler
Many organizations are looking at ways to help make the Helicopter Emergency Medical Services (HEMS) safer. The FAA is working with FAR Part 135 Operators along with Organization such as HAI, CAAMS and AAMT to bring in voluntary solutions. One simple solution to help alleviate many of the night HEMS Controlled Flight Into Terrain (CFIT) accidents is by changing the night VFR visibility minimums for FAR Part 135 HEMS Operations. But what should they be changed to? To help determine that answer let us first look at the root cause of many of our fatal HEMS accidents since January 2000.
To find all of the HEMS accidents on the NTSB web site http://ntsb.gov/ntsb/query.asp takes more than a simple search. Although many of the HEMS accidents were conducted under FAR Part 135, others were conducted under FAR Part 91. So to find as many accidents as possible required a search by aircraft type and operator. My search resulted in finding 152 HEMS accidents since January 2000, of which 44 were fatal. That equates to a 29% accident fatality rate in the HEMS industry, a rate that is just too high.
Of the 47 fatal accidents weather was a contributing factor in the accident in 22 of the accidents (or 47%). Reading the NTSB reports it is easy to see that there is a direct correlation between unaided night flights and weather, but is there a prominent factor? Yes, 73% or in 16 of the 22 weather related fatal accidents the temperature and dew point were within 6° Fahrenheit, and the winds were less that 10 knots for the area where the flight was conducted. When those factors are present there is a high likelihood of fog forming. Add in night unaided operations over a sparsely populated area and it's unlikely that the fog will be seen by the HEMS crews before it's a problem.
To help address the weather related accident issue, the FAA has implemented changes to A021, by requiring slight increases to the FAR Part 135 weather planning minimums, and new documentation of our route planning. Most HEMS pilots have been doing this type of detailed flight planning for years just not documenting it. But is it enough?
Many of the night HEMS accidents happened with weather considered "legal" when the crew took off, but to understand what is legal we first need a short class on legal weather. Reported visibility is straight forward; it is what it is. But a ceiling is defined in the Aeronautical Information Manual (AIM) as "the heights above the earth's surface of the lowest layer of clouds or obscuring phenomena that is reported as "broken", "overcast," or "obscuration," and not classified as "thin" or "partial." http://www.faa.gov/air_traffic/publications/atpubs/PCG/C.HTM Any cloud layer reported as few or scattered is not considered a ceiling.
Reviewing one of the many HEMS night unaided weather related accidents, the weather report at the time of the accident was winds 290º at 5 knots, 5 miles visibility, few clouds at 500 feet, overcast at 5500 feet, temperature +21, dew point + 20. This was "legal" weather for the flight, with the few clouds at 500 feet not even factoring into the weather equation since few clouds do not constitute a ceiling, but still they crashed with legal weather. So can we change the weather minimums to something reasonable that could help reduce the weather related fatal crashes in the HEMS community?
To help reduce the weather related fatal HEMS crashes I propose changing the current FAR Part 135 in route weather requirements by adding: Night cross-country operations without Night Vision Imaging Systems require visibility of not less than 5 miles with no cloud or obscuring phenomena layers below 2000 feet.
This simple and straight forward 2000/5 is an easy solution that could help protect our unaided HEMS crews, and this more restrictive weather minimum would only be a real factor when there is a high probability of fog. Since 16 of the 22 fatal HEMS accidents or 73% of those fatal incidents weather was a contributing factor, and there was a high probability of fog or low clouds in the area.
The amount of HEMS accidents our industry has seen can not continue. Many times when looking for ways to prevent accidents we find complex and time consuming solutions. But if we bring all interested parties to the table, and look at the root cause of most accidents we can normally find a simple solution to rectify the problem. So Pilots', Operators', Professional Organizations', the FAA and the NTSB need to come together to find solution before more HEMS professional are lost.