Ice is one of the most terrifying conditions a helicopter pilot can encounter.
“It’s a constant problem,” said Stan Rose, the Helicopter Association International’s (HAI) director of safety. “Usually you see it during the change of seasons and in a low-level VFR environment. With ice you have two problems that are specific to helicopters. You are changing the shape of the airfoil and therefore losing the efficiency of the rotor system. And helicopters are such lightweight machines that ice adds significant weight, a much higher ice weight to aircraft weight ratio than in a typical fixed-wing aircraft. It’s a nasty problem.”
Rose knows of what he speaks. Some years ago three-quarters of an inch of ice accumulated on a Bell LongRanger fuselage in a matter of seconds and he had to break through the side window to see out. Fortunately he was next to an airport. “I wouldn’t have made it another two miles,” he recalled.
Following recent crashes of EMS helicopters in Illinois and Iowa in December last year and this January, the FAA issued a revised Special Airworthiness Information Bulletin (SW-08-03R) covering recommendations for rotorcraft flying into snowy or icy conditions. The SAIB describes procedures to reduce the probability of an uncommanded in-flight engine shutdown due to snow and/or ice ingestion and reminds operators that most helicopters are neither equipped nor approved for flight-into-icing conditions. (See story on this page.)
While the NTSB will not issue its final accident reports for some time, available evidence currently suggests that ice contamination played a significant role in the December and January accidents.
On Dec. 10, 2012, at 8:16 p.m. local time, a 1992 BK117A3 operated by Air Methods for React crashed near Rochelle, Ill., en route to a patient pick-up after encountering IMC. The 65-year-old pilot and the two-person medical crew were killed. Shortly before the crash, the pilot reported that he was aborting the mission and returning to his hospital base in Rockford due to weather. Surface weather reported at Rochelle Municipal Airport, 10 miles from the accident site, at 8:15 p.m. was seven miles visibility, light snow, ceiling 3,300 feet overcast, temperature -1 deg C and dew point -2 deg C. A witness near the crash site reported that it was sleeting at the time of the accident.
Then, on this January 2, a 2009 Bell 407 flying for Mercy Air and operated by Med-Trans crashed while flying VFR near Mason City, Iowa, en route to a patient pick-up, killing the pilot and two flight paramedics aboard. Conditions at the time of the evening crash were reported as overcast with a temperature of 27 deg F. The 2,700-hour pilot-in-command joined the program in September, but had extensive experience flying helicopter tours in Alaska and the Grand Canyon and had recently flown for a HEMS operator in the St. Louis area. The helicopter was equipped with night-vision goggles and satellite tracking. The tight debris field was confined and a post-crash fire consumed the wreckage.
Satellite tracking of the eight-minute flight revealed that it was at an altitude of 2,648 msl less than one minute and one-quarter mile from the crash site. The debris path was 100 feet long. Witnesses near the crash site reported mist and ice. A pilot who had flown into Mason City 90 minutes before the crash reported encountering light rime ice. First responders to the crash site reported ice-slick roads and haze. A police car slid through an intersection. Weather at Mason City, seven miles east of the accident site, was reported four minutes before the crash as eight miles visibility, 1,700 feet broken, 3,300 feet overcast, temperature -3 degrees C and dew point -5 degrees C. However, 20 minutes after the accident ceilings were reported as 1,300 feet broken and 1,800 feet overcast.
Some newer and larger helicopters have rotor and/or engine-inlet icing protection. The optional full ice protection system (FIPS) on the AgustaWestland AW139 medium-twin includes ice detectors, an automatic activation system with manual backup, electrical power generators, engine intake protection grids and heated windshield and main and tail rotor blades. Sikorsky is equipping its S-92A heavy and S-76D medium helicopters with a rotor ice protection system (RIPS) that uses automatic electrothermal heating of the main and tail rotor blades.
However, a pilot flying an older or smaller helicopter without this technology and who encounters sudden or even gradual icing buildup has limited options. “We know, as helicopter pilots, it’s not something we can climb out of,” Rose said. “That’s a fixed-wing response and we don’t have that luxury. If you don’t have the mental picture before the incident happens or you think you can fly out of it, you have a problem. When it happens, it can be dramatic or sneaky gradual. But one way or the other, your performance is affected.”
Rose said the only safe option is to land immediately. “In my opinion, you put it down. I don’t think we do that enough.”