By Gene Trainor, FAA Rotorcraft Collective
As we enter the cold weather months, the FAA urges helicopter pilots and mechanics to prepare for icing conditions and other winter flying risks. Thankfully, equipment and operating procedures have evolved over the years to greatly reduce these risks. A key factor, as in any season, is pilot and mechanic vigilance.
One important document to familiarize yourself with is a Special Airworthiness Information Bulletin (SAIB) titled Recommendations for Rotorcraft During Icing/Snowy Conditions, which was published back on Nov. 26, 2013. The SAIB’s warning that most helicopters are not FAA-approved for flight into known icing (FIKI) conditions remains relevant today. Instead, most of these helicopters are FAA-approved for flight into inadvertent icing conditions. The SAIB mentions two accidents in 2013, one of them fatal, where ice or snow ingestion led to the loss of in-flight engine power.
The SAIB warns that ice and/or snow can accumulate in the airframe engine inlet area while the rotorcraft is on the ground or in the air, and that turboshaft-powered rotorcraft are particularly vulnerable. Snow and ice can build up in the engine intakes and plenums when the rotorcraft is on the ground and the engine or engines are not operating or are operating at low power for extended periods. When a pilot increases engine power during takeoff, the accumulated snow and/or ice can separate from the airframe inlet surface and get ingested into the engine, resulting in decreased power or engine failure.
The Rotorcraft Collective, an FAA-industry safety group, also produced a video online at youtu.be/ClAgalrHyig that outlines how pilots can prevent icing accidents.
Both the SAIB and the video recommend the following:
- Review the rotorcraft flight manual’s limitations and operations sections for flight guidance for icing or falling/blowing snow. Helicopters are often prohibited from operating in known icing conditions, or when snow is falling or blowing.
- Look out for icing at weep holes, especially blade tip caps; engine oil coolers; fuel vents; static ports; drive pulleys; pitot tubes; intake screens; and tundra boards or bear paws. Most icing occurs between 0 and -20 degrees Celsius (32 degrees to -4 degrees Fahrenheit). During freezing temperatures, pay particular attention for any sheet ice on the bottom and forward of the inlet. Ice can also form behind particle separators. Engine preheating may be required.
- Remove all accumulated snow or ice without chipping or scraping. Instead, use heated air or deicing fluid in accordance with the manufacturer’s procedures.
- Evaluate current and predicted weather briefings from Flight Service. Other resources for weather conditions include aviationweather.gov/hemst and aviationweather.gov/gfa/#ice.
- Park helicopters indoors or cover them. If the aircraft is parked outside, install inlet covers and exhaust inserts or covers. Make sure the REMOVE BEFORE FLIGHT streamers are visible.
- Prior to engine start, remove the inlet/exhaust inserts or covers and perform a complete inlet/exhaust inspection (using a flashlight). The inspection should include surfaces inside the inlet, the cowl area forward and around the inlet, and the area behind the particle separator or screen (if installed). Some aircraft may require fully opening the cowlings to gain access to inspect the inlet, assuring that a properly certificated person performs this task.
- If you keep the rotorcraft on the ground for an extended period (i.e., waiting for clear weather), shut down the engine or engines. Before takeoff, conduct a detailed preflight inspection and remove any snow/ice build-up. Perform the inspection even if the rotorcraft is fitted with some form of inlet protection, such as screens or baffles.
- Be aware that rotating icy rotor blades can sling ice at other aircraft and bystanders.
Winter weather is inevitable. Let’s help make sure winter weather accidents aren’t.