Commercial, Safety, Training

Ounce of Prevention

By By Mike Redmon | February 1, 2011

Controlled flight into terrain, (CFIT) is the number one cause of fatal helicopter accidents. The overwhelming majority of these CFIT accidents occur during inadvertent instrument meteorological conditions (IIMC). The U.S. military, FAA and various other agencies have all tried to eliminate or at least mitigate this hazard to helicopter crews but haven’t had rousing success. IIMC is a pilot-induced emergency that can be avoided. I’d like to share my thoughts on how to reduce these accidents.

With some caveats, the FAA has authorized the HEMS Weather Tool for EMS pilots to use. It is a good product but it is only as good as the information it has access to. Assume two airports 40 miles apart are reporting CAVU. The HEMS Weather Tool will predict CAVU for the low lying swamp that sits between the two airports. There just aren’t that many weather reporting stations in rural areas to make this product foolproof. We have all seen airports reporting 10 miles visibility and the approach end of the runway fogged in.

Weather radar also has shortcomings. The national radar summary is just a composite picture of what precipitation the single site radars are detecting. The radar sites can only pick up normal rain/wet snow to about 80 miles and intense rain/wet snow out to around 140 miles. That’s the first problem. A lack of precipitation being displayed might not mean anything in locations far from any weather radar site. Take a location such as Findlay, Ohio. The closest radar site is 90 miles away. Another shortcoming is that snow, especially cold dry snow, doesn’t pick up on radar very well. Add distance to the equation and the radar screen will be blank but there could be a lake effect snow storm at your location. Also, the radar tilts up a minimum of.5 degrees. The radar beam will not see anything below 6,000 feet AGL when it gets 120 miles away. Lake effect snow bands are many times below this altitude. Instead of relying solely on the NWS radar images, I like using the local TV station’s weather radar. They are very accurate and can tell you exactly where the precipitation is located in your local flying area.


I was burned a couple of times by WSI. Both times in the middle of the night. I checked the weather which looked exactly like it did earlier in the night. Both times it didn’t register that the weather information was hours old. Maybe I missed that fact since I just got awakened from my “safety nap.” At some point I realized the weather I was seeing wasn’t the same as what I had just read on the WSI. Upon returning to the base I’d see that the WSI computer was “locked up” and hadn’t received an update in hours. A simple check of the METAR time would have clued me in to the issue.

You can only accept flights that are above your company weather minimums. Once on a trip and the weather goes below company minimums, you have no option but to discontinue the flight. The decision is not yours to make anymore. Weather minimums in EMS have increased over the last few years. In some circumstances they can be too high, but following the rules and regulations is a sign of professionalism. The ability to judge the flight visibility is one key to avoiding IIMC. This can be difficult at night when flying over remote areas due to the lack of ground lights. This is one of the reasons I went IIMC. I didn’t see a snow band until I was in it. I learned if there was any chance of poor weather to fly where there are ground lights. Following highways is great because car lights help judge flight visibility. Maybe your company check airman isn’t from your part of the country and just comes into town for Part 135 check rides. Ensure you share with any new pilots the local weather patterns. Go one step forward and put the information in the base reading file. Don’t let the new pilot figure it out one dark night by himself.

CFIT isn’t solely a function of poor weather and IIMC. Plenty of helicopters have smacked towers and wires in broad daylight. Since I was lazy, I would fly at or above the minimum elevation figure on the sectional chart. I would only deviate from that number for weather or if I knew the location of obstructions without the use of the map. I never assumed I would see any of the towers in my flight path. Tower lights do burn out from time to time. When flying lower than the MEF, ensure you fly a known route. Do this even if it adds a few minutes to your trip. I liked following major roadways when in a new area and my helicopter didn’t have a moving map GPS. This helped me in pinpointing my exact location at all times.

I have a couple of suggestions for aviation managers, too. First, a moving map GPS with XM Satellite weather should be installed in all EMS helicopters. I would also add the terrain database. An even smaller investment is the ability to get weather on the pilot’s cell phone. Fly Safe!

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