Helicopter Flight in Winter Conditions

Guidance around flying a helicopter in winter conditions

Windscreen Misting

Although a risk at any time of year, embarkation of crew and passengers with rain soaked clothes is more likely to lead to condensation on windscreen and windows in the winter. Lifting off before this has cleared can be very dangerous and has been the cause of a number of accidents, at least one being fatal.

White-Out

White-out will cause the loss of all external visual reference and can occur at any time during flight. It can occur during take-off or landing when re-circulating loose snow obscures external cues, or it can happen at other times when the snow covered ground and the sky merge to obscure the horizon. To prevent these situations occurring, the pilot should ensure that he always has clearly visible cues that will not be obscured by snow. When en route, this may mean a change of route and will require careful choice of landing site. Time spent in the hover during take-off over loose snow should be kept to a minimum.

Flight in Snow or Icing Conditions

Clearance for a helicopter to fly in icing conditions is based on a type specific certification. The number of helicopter types approved to fly in icing conditions is very small although an additional number of other types have been given a ‘limited’ icing approval. These types are almost all exclusively used in the offshore oil and gas industry where the over-water aspect of the operation provides an escape from icing conditions. Helicopter operations in the onshore environment are almost exclusively based on the precept of avoidance of flight in icing conditions.

Precautions should be taken to avoid encountering icing, a number of which are as follows:

  • Obtain a thorough meteorological briefing, especially when temperatures are expected to be near to or below freezing.

  • If icing is suspected from either visual or other signs (e.g. vibration, abnormally high power requirements or engine temperatures) action should be taken to vacate the suspected conditions by transitioning to a warmer area.
     
  • Flight in freezing rain is prohibited.

Flight in falling snow or sleet may be approved but only as specified in the Flight Manual Limitations Section. Such Limitations may require a particular helicopter configuration such as the installation of engine intake snow protection devices. If the helicopter is not in the relevant configuration, flight in the specified condition is not permitted. There may be circumstances when the helicopter has been exposed to falling sleet or snow after start-up but before take-off. In this situation, the engine intake and surrounding surfaces may need to be checked for build-ups. Once again, the helicopter manufacturer should provide guidance on such requirements.

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FOP.Admin@caa.co.uk