Aircraft Flight Instruments and Navigation Equipment

 

CFI Instrument Practical Test Standards, FAA-S-8081-9B, June 2001 II. Technical Subject Areas A. Aircraft Flight Instruments and Navigation Equipment 3. Anti-ice/deicing and weather detection equipment and their operating characteristics a. Airframe - structural icing 1) Accumulation of ice on exterior surface of aircraft 2) Requires a) Visible moisture (coulds, rain) b Freezing temperatures 3) Types a) Rime i) Small droplets that freeze immediately ii) Milky white, rough looking iii) Especially on leading edges of wings and struts b) Clear i) Relatively slow freezing of large droplets ii) Can spread over large surface, changing shape of airfoil ii) Clear, hard to see, most dangerous c) Mixed i) Mixture of clear and rime ii) Ice particles embedded in clear ice, very rough OAT (°C) range  Icing type -10 to 0 Clear -15 to -10 Mixed -20 to -15 Rime 4) Effects a) Control problems due to change in airfoil shape b) Changed stall angle of attack and increased stall speed c) Decreased lift d) Increased drag e) Blocked or limited control surfaces f) Increased weight g) Roll upset caused by airflow separation which induces self deflection of ailerons 5) Inadvertent icing encounter a) When operating in visible moisture, anticipate ice by monitoring OAT b) Proper use of anti-icing/deicing equipment is critical. Refer to POH/AFM c) Activate appropriate anti-icing/deicing when OAT is 5°C or less before entering visible moisture d) Use flashlight to check for ice on night flights e) Pilot actions once airframe ice ammumulation begins i) Move to altitude with significantly colder temperatures ii) Move to altitude where temperatures are above freezing iii) Fly to an area clear of visible moisture iv) Change heading and fly to area known to be free of ice (e.g., consider 180° turn) v) Consider immediate landing at nearest suitable airport 6) Anti-icing/deicing equipment a) Not designed for operation in icing conditions indefinitely b) Intended simply to allow pilot more time to get out of the icing conditions 7) Cessna TR-182 and airframe icing a) Flight into known icing conditions is prohibited "Known icing does not mean a near-certainty of icing conditions, only that icing conditions are being reported or forecast." - NTSB b) No standard airframe anti-ice/deice equipment c) Windshield defrost air is supplied to outlet on top left side of antiglare shield. Activate by rotating DEFROST knob. d) Inadvertent icing encounter in Cessna TR-182 i) Prop anti-ice ON ii) Pitot heat ON iii) Turn back or change altitude iv) Cabin heat full ON, windshield defrost ON v) Increase RPM to minimize prop ice vi) Beware carb ice. Apply carb heat only as required. Lean mixture if carb heat used continuously vii) Plan landing nearest suitable airport or "off airport" site viii) Beware: ¼ inch or more on leading edge significantly increases stall speed ix) Leave flaps retracted UP x) Open window, scrape ice if practical for landing visibility xi) Approach with forward slip if needed for visibility xii) Approach 85-95 KIAS xiii) Land in level attitude References: Instrument Flying Handbook, FAA-H-8083-15, 1999 The Instrument Flight Manual, Sixth Edition William K. Kershner, 2002 Aircraft Icing, AOPA Safety Advisory AC20-113 Pilot Precautions and Procedures to be Taken in Preventing Aircraft Reciprocating Engine Induction System and Fuel System Icing Problems AC91-51A Effect of Icing on Aircraft Control and Airplane Deice and Anti-Ice Systems AC91-74 Pilot Guide: Flight in Icing Conditions