COLD WEATHER OPERATIONS

1. COLD WEATHER OPERATIONS

2. COLD WEATHER OPERATIONS • UH-60 ENVIRONMENTAL CONSIDERATIONS • IN-FLIGHT ICING • CHECKLIST FOR COLD WEATHER OPERATIONS

3. UH-60 ENVIRONMENTAL CONSIDERATIONS • COLD WX OPERATION • COLD WX PREFLIGHT CHECK • ENGINE OPERATION • GROUND OPERATIONS/TAXIING

4. UH-60 ENVIRONMENTAL CONSIDERATIONS • COLD WX OPERATION: The basic helicopter with normal servicing can operate at temperatures down to -34C (-29F). • WARNING: Static electricity generated by the helicopter should be discharged before attempting a sling or rescue hoist pickup. In cold, dry climatic conditions static electricity buildups are large. Use a conductor between the helicopter and the ground to discharge the static charge. Delay lowering rescue hoist hook until helicopter is over the load, to lessen static charge buildup. • NOTE: During operation in cold weather, particularly when snow or moisture is present, the tail wheel locking indicating system may give erroneous cockpit indications

5. UH-60 ENVIRONMENTAL CONSIDERATIONS • COLD WX PREFLIGHT CHECK • CAUTION: Ice removal shall never be done by scraping or chipping. Remove ice by applying heat or deicing fluid. • In addition to normal preflight checks, check aircraft for ice or snow. If ice or snow is found, remove as much as possible by hand and thaw aircraft with heated air or deicing fluid before attempting start. Failure to do so may cause damage. • Check main rotor head and blades, tail rotor, flight controls and engine inlets and hand holds for ice and snow. Failure to remove snow and ice accumulations can result in serious aerodynamic, structural effects in flight and serious foreign object damage if ice is ingested into the engine. Check Engine PCLs for freedom of movement.

6. UH-60 ENVIRONMENTAL CONSIDERATIONS • COLD WX PREFLIGHT CHECK • On aircraft equipped with Extended Range Fuel System, check ESSS and 230/450-gallon fuel tank for ice or snow. Remove as much as possible by hand and then use heated air. Start APU and turn on pressure to both INBD and OUTBD fuel tanks. Wing-mounted pressure regulator may require heated air applied directly onto the exhaust vent protruding from the ESSS wing. After regulator valve is operating and fuel tanks are pressurized, leave system on. DO NOT TURN OFF PRESSURE SWITCHES OR PRESSURE REGULATORS MAY FREEZE.

7. UH-60 ENVIRONMENTAL CONSIDERATIONS • COLD WX PREFLIGHT CHECK • When parking the helicopter in temperatures below freezing, the gust lock may seize due to frozen moisture in rod assembly. Normal operations may be returned by warming the assembly. Main rotor tie downs may be used in lieu of the gust lock to meet parking requirements. • COLD WEATHER CONTROL EXERCISE IS REQUIRED WHEN OPERATING IN A TEMPERATURE RANGE OF -17C (1F) AND BELOW IN ACCORDANCE WITH TM 1-1520-237-10/CL.

8. UH-60 ENVIRONMENTAL CONSIDERATIONS • ENGINE OPERATION: Even though cold weather does not particularly effect the engine itself, it still causes the usual problems of ice in the fuel lines, control valves, and fuel sumps, which frequently prevent a successful cold wx start. It may be found that certain elements or accessories need preheating. • CAUTION: When starting an engine that has been exposed to low temperatures, watch for rise in TGT within 45 seconds. If no TGT rise is evident, manually prime the engine and attempt another start. If there is no overboard fuel flow during prime, inspect for ice in the sumps and filters. During cold wx operation, allow longer warm-up period to bring transmission oil temp up to desired operating range IAW Chapter 5 of the -10. When advancing PCLs , maintain xsmn pressure within normal operating range

9. UH-60 ENVIRONMENTAL CONSIDERATIONS • ENGINE OPERATION CONT’D: When it is necessary to prime the engines for a cold weather engine start, perform manual prime IAW the -10/CL. • ENGINE OIL SYSTEM CHARACTERISTICS: It is normal to observe high engine oil pressure during starts when the ambient temperature is 0 C(32 F) or below. Oil pressure should return to the normal range after operating 5 minutes. However, time required for warm up will depend on temperature of the engine and lubrication system before start. For engine starts in extreme cold weather (near -54 C (-65 F)), refer to the -10 for additional oil pressure characteristics.

10. UH-60 ENVIRONMENTAL CONSIDERATIONS • ENGINE OIL SYSTEM CHARACTERISTICS: It is normal for the OIL FLTR BYPASS caution light to be on when starting an engine with oil temperatures below normal because of high oil viscosity and the accumulation of oil filter contaminants. When the engine oil temperature reaches about 38 C (100 F) during warm up, the light should go off.

11. UH-60 ENVIRONMENTAL CONSIDERATIONS • GROUND OPERATIONS / TAXIING • GROUND OPERATIONS: Following flight into icing conditions, when droop stop heaters are not installed or fail to operate properly, the droop stop hinges may become iced, resulting in the droop stops not returning to the static position during rotor coast down. When this occurs, the main rotor blades may droop to within 4 feet of the ground during shutdown. Caution must be taken during shutdown to ensure personnel remain clear of the helicopter.

12. UH-60 ENVIRONMENTAL CONSIDERATIONS • TAXIING: The helicopter should not be taxied until all engine temperatures and systems pressures are within normal range. All taxiing should be done at low speeds with wide-radius turns. If the tires are frozen to the surface, a slight yawing motion induced by light pedal application should break them free. Taxiing in soft snow requires higher than normal power.

13. IN-FLIGHT ICING • TYPES OF AIRCRAFT STRUCTURAL ICE • WEATHER AREAS CONDUCIVE TO ICING • EFFECTS OF ICING ON ROTARY WING AIRCRAFT • OPERATING IN ICING CONDITIONS

14. IN-FLIGHT ICING • TYPES OF AIRCRAFT STRUCTURAL ICE • CLEAR ICE (GLAZE): The most serious form of structural ice. It is found in cumuliform clouds, where the temperature is between 0 C and 10 C, or in areas of freezing rain associated with warm frontal systems. When clear ice forms on the leading edge of rotors, wings and antennae, it often take a blunt-nose shape, tapering toward the rear. • RIME ICE: Normally encountered in stratiform clouds, where temperature ranges from 0 C to -20 C, or in cumuliform clouds between -10 C to -20 C. It is white, milky, or opaque, and of a rougher consistency than glaze. Except for a limited region near the center of the leading edge of an airfoil, rime ice generally shows little or no tendency to adhere to the contour of an airfoil.

15. IN-FLIGHT ICING • TYPES OF AIRCRAFT STRUCTURAL ICE • FROST: Aviators tend to underestimate the flight hazards of frost formations. Frost increases drag and is particularly hazardous at low airspeeds, takeoffs and landings. If frost is left on the aircraft during takeoff, small ice crystals act as sublimation nuclei. Unless windshield anti-ice is used, frost on the windshield may cause restriction to or total loss of visibility.

16. IN-FLIGHT ICING • WEATHER AREAS CONDUCIVE TO ICING • FRONTAL INVERSIONS: When warm air is forced to rise over a colder air mass, a frontal inversion is present. Below the inversion, structural icing areas are common in winter. An aviator should escape an area of freezing precipitation by climbing to the warmer air above the frontal inversion. • CLOUDS: • Stratiform: Indicate stable air in which either minute water droplets and/or ice crystals are suspended. Generally associated with rime icing. • Cumuliform: Indicate unstable air in which strong vertical currents of air can support larger, supercooled liquid drops. Associated with the more hazardous, clear or glaze icing.

17. IN-FLIGHT ICING • WEATHER AREAS CONDUCTIVE TO ICING • MOUNTAINOUS TERRAIN: The lifting of conditionally unstable moist air over mountain ranges during the winter is one of the major ice-producing processes. The most severe icing will take place above the crests of the mountains and to the windward side of the ridges. Usually, the icing zone extends about 4,000 feet above the tops of mountains. The movement of a front across a mountain combines two weather areas in which serious icing may occur.

18. IN-FLIGHT ICING • EFFECTS OF ICING ON ROTARY WING AIRCRAFT • ROTOR SYSTEMS: Ice formation on main and tail rotor systems may produce critical vibrations and loss of efficiency. Increased torque is indicative of ice buildup on the main rotor blades. Decreased autorotational capability and low rotor speeds may result. • AIR INTAKE AND AIR INLET SCREENS: Ice accumulation on the engine and transmission air intake screens is more rapid than on the rotor systems, which may result in inadequate cooling of these systems. Some indicators of air inlet icing is a loss of power, increase in TGT, accompanied by compressor surges and/or stalls.

19. IN-FLIGHT ICING • EFFECTS OF ICING ON ROTARY WING AIRCRAFT • AIRFRAME: While ice deposited on the air frame is unlikely to present any problem from weight growth, problems arise from ice buildup on external struts, pipes, and other projections of small sections which have a high catchment rate. In these cases, the ice tends to build in a form which will eventually shed, presenting a possible FOD hazard. • ANTENNAS: Building and shedding of ice on antennas can cause sever oscillations and also may affect communications. Accumulation and shedding of ice on the FM whip antenna can cause large amplitude oscillations, causing the antenna to strike the tail rotor.

20. IN-FLIGHT ICING • OPERATING IN ICING CONDITIONS • CAUTION: Activation of anti-ice systems after entry into potential icing conditions creates the possibility of engine FOD caused by ice shedding. The ice detector has been designed primarily as a sensor to indicate the requirement for activation of the blade deice system. • All anti-ice systems must be turned on prior to entering visible moisture at ambient temperatures of 4 C (39 F) or less. • If icing conditions are encountered, turn on all anti-icing equipment immediately. If torque required increases 20% above that required for level flight at the airspeed being maintained prior to entering icing, exit the icing environment or land as soon as possible. A 20 % torque increase indicates that normal autorotational rotor rpm may not be possible.

21. IN-FLIGHT ICING • OPERATING IN ICING CONDITIONS • When the helicopter is equipped with an operating blade deice, and icing conditions are encountered, a recurring torque increase up to 14% per engine may be experienced during normal operation of the blade deice system due to ice buildup. The crew should closely monitor engine instruments to prevent exceeding limits and/or rotor droop. Significant power losses and increased fuel consumption will occur with the activation of the engine inlet anti-icing systems. The main rotor hub and blades collect ice before initiation of a deice cycle. Moderate vibration levels of short duration can be expected in controls and airframe during normal deice cycles. Asymmetric shedding of ice may cause severe vibrations when blade deice is inoperative, but these normally subside after 30-60 seconds.

22. CHECKLIST FOR COLD WEATHER OPERATIONS • Check weather carefully; ask the aviator who just came through • Check notice to airmen (NOTAM) • Remove all frost and snow before takeoff • Check controls for restrictions of movement • Hover or taxi slowly. Use brakes with caution. • After runup in fog or rain, check for ice in rotor wash areas • Wear sunglasses if glare is bad • Rotary-wing aircraft should maintain a high hover to reduce blow up onto the aircraft

23. CHECKLIST FOR COLD WEATHER OPERATIONS • Be wary of possible white-out conditions when landing to snow covered areas. • Use pitot heater when flying in rain, snow, clouds, or known icing zones. • When flying in freezing rain conditions, climb into the clouds where the temperatures will be above freezing (unless the temperature at a lower altitude is known to be high enough to prevent ice). • Report all in-flight weather hazards. • If icing cannot be avoided, choose the altitude of least icing. (Glaze ice is common in cumulus clouds; rime ice is common in stratiform clouds)

24. CHECKLIST FOR COLD WEATHER OPERATIONS • Avoid making steep turns if the aircraft is heavily coated with ice • Before takeoff, insure that anti-icing and deicing equipment is in operating condition.