Reminds Operators That Most Helos Not Approved For FIKI Operations

The FAA has posted a Special Airworthiness Information Bulletin (SAIB) for the owners and operators of turboshaft-powered rotorcraft concerning the possibility of inflight engine loss of power due to the ingestion of ice and/or snow. Accumulation of ice and/or snow can occur in the area of the airframe engine inlet while the rotorcraft is on the ground or in the air. The SAIB describes procedures to reduce the probability of an engine in-flight shutdown due to ice and/or snow ingestion, and is intended to remind owners and operators that most helicopters are not approved or equipped for flight into icing conditions.

The FAA says it has determined that ingested ice and snow accumulation in the airframe engine inlet can cause the engine to lose power. This has resulted in accidents and fatalities. Snow and ice can build up in the engine intakes and plenums when the rotorcraft is on the ground with the engine(s) not operating or are operating at a low power setting 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 be ingested into the engine, resulting in decreased power or complete engine failure. Some of the early turboshaft engines with axial inlets are particularly susceptible to loss of power due to ice and snow ingestion. Some inlet designs do not allow for easy detection of accumulated ice and/or snow, and may require detailed inlet inspections to determine if any accumulation has occurred.

Some rotorcraft require a snow protection kit for the airframe engine inlet to successfully operate in falling and blowing snow. Operation in snow without the kit can be especially risky when hovering in snow and then transitioning to takeoff when weather conditions clear. Snow may accumulate on or in the engine inlet area during hover, and then be dislodged and ingested into the inlet during takeoff. Pilots should not believe they have escaped the danger following successful hover in snow with an unprotected inlet.

The flight crew should follow the published Rotorcraft Flight Manual (RFM) procedures for inadvertent ice and snow encounters. If procedures do not exist, the FAA recommends landing the aircraft as soon as possible after any hover or flight in snow or icing conditions, shutting down the engines, and thoroughly inspecting the engine inlet for ice and snow accumulation prior to takeoff. Pilots should be alert for visual cues of ice accumulation on mirrors, wipers, and antennas. Pilots should also be mindful of possible increased vibrations or power requirements.

The degraded performance of the helicopter may be due to increased weight and possible degraded rotor performance due to accreting ice.

Most rotorcraft are not approved for flight in known icing (FIKI) conditions. For rotorcraft not approved for FIKI conditions, a pilot can expect icing any time when operating in visible moisture such as fog, rain, or clouds, when the temperature is below 5°C [41°F]. Pilots should be aware that icing is possible in these ambient conditions and should be prepared to leave the area of visible moisture or change to a warmer altitude as soon as possible. (NOTE: This “warmer” altitude may not always be a lower altitude.)

The FAA says it highly recommends and strongly urges the following:

• Review the Limitations and Operations sections of the RFM for guidance for flight in falling/blowing snow and/or icing. Many aircraft are prohibited from operating in known icing and/or falling and blowing snow,
• Perform basic airmanship and preflight by evaluating current and predicted weather briefings from the area Flight Service Station or other resources for weather conditions.
• When the aircraft is on the ground without the engines operating, install inlet and exhaust inserts or covers. Make sure the REMOVE BEFORE FLIGHT streamers are clearly visibly.
• 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. Remove all accumulated snow or ice.

The FAA says that ice or snow should not be removed by chipping or scraping, and says heated air or deicing fluid should be used as appropriate, in accordance with the manufacturer’s procedures. In freezing temperatures, pay particular attention to sheet ice on the bottom and forward of the inlet. This ice can also form behind particle separators. Engine preheating may be required.

If it is necessary to keep the rotorcraft on the ground for an extended period (i.e., waiting for clear weather), you should shutdown the engine(s). Prior to takeoff, you should accomplish a detailed preflight inspection, removing any snow/ice build-up. You should perform the inspection even if the rotorcraft is fitted with some form of inlet protection, such as screens or baffles.

FMI: www.faa.gov, www.tc.gc.ca/civilaviation/publications/tp185/4-07/winter-operations.htm#heli-ops