The European Aviation Safety Agency (EASA) published 23/03/2011 a
Notice of Proposed Amendment to update the Certification Specifications for large aeroplanes and turbine engines for flights in icing conditions: “Large Aeroplane Certification Specifications in Supercooled Large Drop, Mixed phase, and Ice Crystal Icing Conditions”; which addresses, amongst other aspects, -
Due to the way Pitot or Pitot-static tubes are usually mounted, they are prone to collecting ice crystals. Encountering high concentrations of ice crystals may lead to blocked Pitot or Pitot-static tubes because the energy necessary to melt the ice crystals can exceed the tube heating system capability, or the water formed by the melting process is not completely evacuated and it can re-freeze downstream inside the tube. Pitot or Pitot-static tube blockage can lead to errors in measuring airspeed.
Regards,
HN39