Cold Weather Operations

Gulfstream GVII

Eddie sez:

Cold is in the eye of beholder. Me? Anything below 70°F. Your aircraft is more tolerant but the definition of when cold weather operations begins is still up for grabs. Based on what I've seen in the Cold Weather Operations section of the AOM, it looks like the magic number is 10C. At or below that temperature, there are things you need to do. The colder it is, the more you have to do.

Everything here is from the references shown below, with a few comments in an alternate color.

images

Photo: "Frozen Jack," from The Shining
Click photo for a larger image

Last revision:

20200205

A few temperatures to note

Except as noted, each of the following applies to both ASC 022 / EASA aircraft and non ASC 022 / EASA aircraft.

-65°C — Fire Extinguisher – Amerex, Halon: Minimum temperature storage limit is -65°C. [AOM, §03-01-130, ¶7.d.]

Below -40°C — airplane start-up is prohibited after extended exposure to ambient temperatures below -40°C. For temporary shut-downs at temperatures below -40°C, the airplane is to be considered cold soaked if the time with airplane power off exceeds 5 hours. [AOM, §03-01-10, ¶2.]

-40°C — Fire Extinguisher – Kidde Aerospace, Halon: Minimum temperature storage limit is -40°C. [AOM, §03-01-130, ¶7.c.]

At or below -30°C — If the engine oil temperature is at or below -30°C prior to start and it has been less than 8 hours since shutdown, engine heating is required. . . . Begin heating engine if oil temperature is less than -30°C until temperature is greater than -25°C. [AOM, §03-01-40] For ASC 022 / EASA airplanes: If engines are shut down with temperatures below -30°C, it is expected to take at least 4 hours for the engine main oil temperature to reach -30°C and will require external heating if restart is conducted within 8 hours of engine shutdown. [AOM, §03A-01-40]

-30°C — Life Rafts: Minimum temperature storage limit is -30°C [AOM, §03-01-130, ¶7.b.]

Less than -20°C — If the airplane has been exposed to a prolonged or overnight cold soak of temperature less than -20°C, the CPAM Fail CAS message may display and can be disregarded until warmer cockpit temperatures are reached with APU BLEED AIR ON. [AOM, §03-01-10, ¶7.]

Less than -20°C — If the airplane has been exposed to prolonged cold soak temperatures less than -20°C, the batteries should be warmed by external means to raise battery temperature prior to attempting APU start. [AOM, §03-01-30, ¶2.]

-20°C — Main airplane batteries: Minimum temperature storage is -20°C. The batteries should be removed and stored in an area warmer than -20°C. [AOM, §03-01-130, ¶7.a.]

This is easier said than done. The batteries are heavy and getting them in and out of the aft equipment bay is awkward. We long ago decided if the temperature is that cold and we can't find a hangar, we are going someplace else.

Down to -20°C — Gulfstream provides these recommended procedures to assist in initial systems operation after prolonged cold soak conditions in temperatures down to -20°C.[AOM, §03-01-10, ¶3.]

10°C — Minimum oil temperature for operations above idle is +10°C [AOM, §03-01-50, ¶2.]

9°C — Minimum engine fuel temperature for takeoff thrust is +9°C. With cold wing fuel temperatures, the engine fuel temperature is expected to drop with takeoff power set. Engine fuel temperature should stay above 0°C for the takeoff. [AOM, §03-01-50, ¶2. and §03-01-90]

images

Photo: Water tank draining determination table, AOM, §03-01-130, Table 1
Click photo for a larger image

images

Photo: Galley equipment heating table, AOM, §03-01-130, Table 2
Click photo for a larger image

Preparation

[AOM, §03-01-10]

4. It is recommended that the nose landing gear and main landing gear shock struts and tires be serviced prior to departure from the warm location in preparation for cold day operations. Refer to the AMM task 12-10-00 for more information.

5. Cockpit and cabin heating is accomplished using APU BLEED AIR. Heating can be expedited by closing the main entry, internal baggage and external baggage doors. With the main entry door open, the acoustic door can be closed to aid in warming.

6. The latching sequence of the MED may be assisted by pulling inboard on the upper airstair when commanded closed.

9. If the airplane will be cold soaked, it is recommended to refuel the airplane the day of departure.

Preflight Inspection

[AOM, §03-01-20]

  • Ensure the main landing gear wheels have chocks in place. Be aware that chocks may not hold on slippery surfaces unless the surface has been sanded.
  • PARKING BRAKE - Released.
  • Main door and baggage compartment door seals, hinges and tracks should be free of snow / ice. Ensure proper operation to prevent refreezing in flight.
  • Ensure air data probes, TAT probes, and static ports are clear. Water rundown resulting from snow removal may refreeze immediately forward of the static ports and cause ice buildup which causes disturbed airflow over the static ports and erroneous static reading even though static ports themselves are clear.
  • Remove snow / ice top-to-bottom. Avoid spraying heated fluids directly on cabin and cockpit windows. Ensure that edges of all emergency exit windows / doors are free of ice accumulation. Ensure that the radome area is clean. If using mechanical means, special care should be taken to avoid damage to antennas. Remove any fluid runoff from cockpit windows and radome prior to departure.
  • Clean the wing from wing tip to wing root. Ensure that leading edge is free of ice. The Flight Crew should conduct a hands-on inspection to verify leading edge, upper and lower wing surfaces are clean. Under-wing frost may form between the forward and aft wing spars following extended high-altitude flight and during ground operation. Under-wing frosting can occur at ambient temperatures well above freezing and may be the forerunner of clear ice formation on the upper wing. Frost in this area can be melted by refueling with warmer fuel. Gulfstream recommends removal of under-wing frost in excess of 1/8 inch (3.2 mm) thickness and all frost on the leading edges and upper surfaces.
  • Ensure accessible fuel tank vents are clear of all traces of ice or snow.
  • Tires, wheels, brakes, struts, side braces, wheel wells and uplocks should be free of snow / ice. Ensure landing gear doors are unobstructed and free of impacted ice or snow. Clean as necessary using a non-damaging mechanical means. Use hot air for frozen brakes.
  • Remove any ice or snow contamination from the leading edge of the stabilizer. Remove all accumulations from the upper surface of the stabilizer and elevator.
  • The leading edge of the vertical stabilizer, as well as the side panels and rudder, should be cleaned of any snow / ice accumulation.
  • DO NOT USE DE-ICING FLUID TO REMOVE SNOW / ICE FROM ENGINE / APU INLET(S). AFTER REMOVAL OF SNOW / ICE, START ENGINE(S) IMMEDIATELY TO PREVENT ANY RE-ICING CONDITION. SELECT COWL ANTI-ICE ON, AFTER ENGINE IS STARTED.
  • The inlet fan must be verified to be free to rotate. Snow / ice removal from the engine inlet should be accomplished using mechanical means. Any frozen deposits that may be bonded to inlet / intake surfaces or fan blades must be removed by hot air.
  • Ensure the APU inlet is clear of impacted ice or snow. Do not spray into APU inlet or ram air inlet.

Airplane Power-up

[AOM, §03-01-30]

  • If the airplane has been exposed to prolonged cold soak temperatures less than -20°C, the batteries should be warmed by external means to raise battery temperature prior to attempting APU start.
  • If TAT probes are found to be contaminated during preflight, select TAT Probe Heat On after APU Air is operating. TAT probe heaters will automatically shut off after one minute of operation. Cockpit TAT indicators will increase rapidly with probe heaters selected. TAT will return to ambient indications 2-3 minutes after heaters shut off.
  • Depending on the ambient temperature and condition of the batteries, it is possible that a slower-than-normal APU start may occur. 5. Operation of the APU is adversely affected by ice accumulations in the APU inlet and by ingestion of ice or foreign materials. Higher than normal EGT indications, with a reduction in duct pressure, are an indication of inlet area icing.
  • After APU start, allow the cockpit to reach normal operating temperature before continuing normal checks.
  • Cycle PARKING BRAKE approximately 10 times. Some hydraulic fluid leakage from the brake pistons may be observed and can be disregarded. Return PARKING BRAKE to the released position once complete.

External Engine Heating

[AOM, §03-01-40]

  • If time since previous shutdown is less than 8 hours, the engine will rotor bow. If the engine oil temperature is at or below -30°C prior to start and it has been less than 8 hours since shutdown, engine heating is required.
  • LIMIT HEAT APPLIED TO 100°C MAXIMUM.
  • Heater cart shall not utilize an open flame for heating.
  • Prepare heat source and place the heater duct externally on the lower cowl door louver.
  • Begin heating engine if oil temperature is less than -30°C until temperature is greater than -25°C.
  • If required to shut down the APU, the order of heating operation is modified: First heat the left engine, remove the heat, start the left engine, shut down the APU, then heat the right engine.
  • After engine oil temperature reaches a stable temperature at idle, the engine may be shut down and restarted without reapplying external heat, if the engine oil temperature is not allowed to cool below -30°C.

Engine Starting

[AOM, §03-01-50]

  • During cold weather starts, oil pressure may temporarily exceed maximum pressure limits until oil temperature rises.
  • Minimum oil temperature for operations above idle is +10°C Minimum engine fuel temperature for takeoff thrust is +9°C. With cold wing fuel temperatures, the engine fuel temperature is expected to drop with takeoff power set. Engine fuel temperature should stay above 0°C for the takeoff.

Taxi

[AOM, §03-01-60]

  • Check flaps for normal operation. Leave flaps in retracted position for taxi to avoid ice buildup.
  • Avoid puddles and slush when possible.
  • Use brakes to control ground speed in taxi to allow the hydraulic fluid to warm and avoid ice/snow ingestion due to use of thrust reversers.
  • If you grew up on steel brakes you may have experienced a wheel fire or two because those things didn't like it hot. Carbon-carbon brakes, on the other hand, are most effective at just above 100°C. It is actually to your advantage to heat them up when you taxi out. Another surprising fact: after a landing, carbon-carbon brake wear is minimal. More about this: Carbon-carbon brakes.

  • Nose wheel steering must be used with care or nose wheel skidding may occur on snowy and icy surfaces. Turns must be entered with low taxi speeds and moderate rates of steering input. Turns can be performed with maximum nose wheel deflection; however, steering inputs must be applied smoothly and at a moderate rate to avoid skidding.
  • Adjust taxi speed to surface conditions. Brake effectivity is reduced on contaminated surfaces. Maintain increased separation between airplanes when taxiing on ice or snow covered taxiways. Be aware that blasted ice or snow can cause damage at considerable distances.
  • If taxi route is through slush or standing water in low temperature, taxi with flaps up to avoid slush and snow accumulation on flaps, flap actuators, and main gear tires.

De-icing and Anti-icing

Limitations

[GVII-G500 AFMS 2020-01, §01-30-50] Anti-Ice and De-Ice Fluids

01-30-50: Anti-ice and Deice Fluids

  1. Approved SAE Type Fluids:
    1. Type I Glycol-Based Fluids (AMS1424)
    2. Type I Non-Glycol-Based Fluids (AMS1424)
    3. Type II, III, and IV Glycol-Based Fluids (AMS1428)
  2. Use of the approved fluid types is prohibited at ambient temperatures below the Lowest Operational Use Temperature (LOUT) specified for the fluid. LOUT data is available in the Operating Manual (OM), Section 03-02-10: Holdover Times for Type I, II, III and IV Fluid Mixtures.
  3. The HOT means two different things, depending on whether you have an approved program or not:

    • With an approved program (Certain 14 CFR 135 and 121 Operators) — Crews may have designated representatives conduct a Post Deicing Check and need not conduct a subsequent pretakeoff contamination check if takeoff occurs within the HOT.
    • All other operators — Crews must perform the post deicing check and if conditions are conducive to additional contamination must conduct a pretakeoff contamination check within 5 minutes before beginning takeoff. The HOT is advisory only.

    More about this: Cold Weather Operations.

  4. Wing Anti-Ice shall be selected on prior to takeoff when operating with Type II, III, or IV fluids applied.
  5. The cumulative time with Wing Anti-Ice ON and Type II, III, or IV fluids applied shall not exceed 20 minutes prior to takeoff.

[G500-MOL-20-0003] As specified in AFM Section 01-30-20, Wing Anti-Ice must be selected ON for a minimum of 4 minutes prior to takeoff. The 20-minute cumulative time, identified in item 4 above, is intended to prevent coagulation of the anti-ice fluid on the leading edge while providing some operational flexibility prior to takeoff. Operators maintain the ability to turn Wing Anti-Ice off, in the event of a departure delay, to stop the cumulative 20-minute timer. When the Wing Anti-Ice is selected back ON, the minimum time specified in AFM Section 01-30-20 must again be observed. Detailed guidance on operations with Type II, III and IV fluids is provided in OM Sections 03-01-70 and 3A-01-70.

Procedures

[AOM, §03-01-20, ¶1.n.] If electing to de-ice prior to engine start: APU - OFF, TROV - CLOSED.

[AOM, §03-01-70] General

  • Type II, III, and IV anti-ice fluids are high viscosity fluids. During the takeoff roll, the fluids are designed to shear off the wing during the takeoff roll, however a limited amount of fluid can accumulate along the leading edge of the wings during takeoff roll and then flow over the top of the wing as the aircraft rotates. This characteristic is called a secondary wave and can momentarily degrade the aerodynamics of the wings. Wing Anti-Ice (WAI) heats the wing leading edges and applied anti-ice fluids preventing this secondary wave behavior. Because of this secondary wave behavior, if Type II, III or IV fluid is applied to the wings, WAI must be on prior to takeoff.
  • WAI may not be on for more than an accumulated total of 20 minutes. If WAI is on for more than 20 minutes, the fluid begins to coagulate on the hot leading edges and contaminates the wings in the same manner as snow and ice. If WAI is turned on in anticipation of takeoff and the takeoff is subsequently delayed, turn WAI off until takeoff is again expected within a few minutes. The time when WAI is off does not count toward the 20-minute time limit.
  • If the 20-minute cumulative limit is exceeded, the fluid must be washed off the leading edges, then reapplied if necessary, before takeoff. Additional applications of de-ice or anti-ice fluid are not effective to clean the wing leading edges.

[AOM, §03-01-70] De-icing and Anti-icing Procedures

  1. Throttles (Left and Right) . . . Idle
  2. APU . . . Off
  3. APU Door . . . Verify Closed
  4. CAI / WAI . . . Off
  5. BLEED AIR (L ENG / R ENG / APU) . . . Off
  6. PACKS (Left and Right) . . . Off
  7. TROV . . . Verify Closed
  8. De-Icing and Anti-Icing . . . Commence
    • De-ice the wings and horizontal tail with an approved de-ice fluid. Instruct ground crew to avoid engine inlets, windows, probes, and antennas.
    • Apply anti-icing immediately after the aircraft is de-iced, if desired. This involves applying a mixture of SAE or ISO Type I /Type II / Type III / Type IV and water to critical surfaces of the aircraft in a one or two step process. This step may increase holdover time(s) between anti-icing and estimated departure time.
    • Perform preflight de-icing inspection checklist immediately following de-icing or during anti-icing.
    • A TAT split without aspiration could also result due to the bleeds being off at the time of de-icing.
  9. Hands-on inspection of: wing leading edges, wing upper and lower surfaces, wing trailing edges.
  10. Visual Inspection of: Vertical and Horizontal Stabilizers, Flaps, Spoilers, Ailerons, Elevator and Rudder, Engine Inlet, All Emergency Exits, All Cockpit Windows, Antennas, Fuselage, ADS probes, TAT probes, Ice probes and Static Ports, Fuel Tank Vents, Cooling, APU Air Intakes, Inlets and Exhausts, and Landing Gear.
  11. Once the preflight inspection is complete, the aircraft is clean and adequately protected, the aircraft should depart as soon as possible. This is especially important in conditions of precipitation or high relative humidity (small temperature/dew point spread).
  12. WHENEVER THE RECOMMENDED HOLDOVER TIME IS EXCEEDED, A PRE-TAKEOFF FINAL INSPECTION IS REQUIRED. IF IN DOUBT, REPEAT THE DE-ICING PROCEDURE PRIOR TO TAKEOFF.

Pre-takeoff Final Inspection

[AOM, §03-01-80]

  • A pre-takeoff final inspection should be conducted within 5 minutes of takeoff. IF THERE IS ANY DOUBT AS TO THE CONDITION OF THE AIRPLANE, THE PILOT IN COMMAND MUST CONDUCT A HANDS-ON INSPECTION OR HAVE THE AIRPLANE DEICED AGAIN PRIOR TO TAKEOFF.
  • If the inspection is conducted from inside the airplane, indication of loss of effectiveness of de-icing / anti-icing fluid, or contamination of airplane surfaces, may be evidenced by the following items: Progressive surface freezing or snow accumulation, random snow accumulation or dulling of surface reflectiveness (loss of gloss) caused by the gradual deterioration of the de-icing/anti-icing fluid to slush.

Lineup / Takeoff

[AOM, §03-01-90]

  • Minimum engine fuel temperature for takeoff thrust is +9°C. With cold wing fuel temperatures, the engine fuel temperature is expected to drop with takeoff power set. Engine fuel temperature should stay above 0°C for the takeoff.
  • FLEX takeoff is not approved for contaminated runways.
  • Verify TAT Indications (DU2 and DU3) are within ±4°C of OAT (from an offboard source i.e. ATIS, Tower, METAR).
  • Verify stable engine operation before brake release.
  • During takeoff in slush, the acceleration rate during the low speed portion of the takeoff roll is normal, but may deteriorate during the high speed portion. Slush and/or water can accumulate on the leading edge and then freeze during climb.

Landing

[AOM, §03-01-110]

  • After extending landing gear, perform three full PARKING BRAKE cycles.
  • Perform firm touchdown to reduce strength of ice bond on brakes.
  • Lower nose wheel to the runway immediately for increased directional control on contaminated runways.
  • Apply brakes smoothly and symmetrically with moderate-to-firm pressure until a safe stop is assured. Do not attempt to cycle brake pedal pressure if the anti-skid is operating.
  • Be prepared for possible downwind drift on slippery runways with a crosswind present.

Securing Aircraft

[AOM, §03-01-130]

  • Verify the TROV is closed.
  • Ensure wheel chocks are in place.
  • PARKING BRAKE Confirm released
  • Internal & External Protective Covers and Plugs Install
  • If necessary, replenish engine oil as soon as possible after engine shutdown. Following extended exposure to cold weather, the engine oil and hydraulic fluid remote replenishing systems will not be operable.
  • This runs contrary to the AFM §02-06-30 note that tells use the TSC or FQI indications are valid 10 - 30 minutes after engine shutdown. It looks like a judgment call.

  • The de-servicing of potable water and waste water tanks must be completed as soon as possible after flight, or before APU shutdown, and will depend on the ambient temperature and the cold-soak period.
  • If draining is accomplished, ensure that there are no residual fluids before the fill / drain caps are installed. If this is not done, the fluids will freeze immediately behind the fill / drain caps and cause delays during the next servicing. When the airplane is at temperatures below 0°C, the drain valves may be left open to permit residual fluids to escape after the system has been drained.
  • Ensure all galley equipment items which contain water, such as coffee makers and water boilers / heaters, are drained.
  • Operate the water taps several times to ensure that the supply lines are empty.
  • Ensure all toilets are drained to protect from freezing.
  • If the airplane will be stored in extreme cold temperatures, the following equipment must be removed from the aircraft and stored in a warm location if the minimum temperature storage limit is exceeded:
    • Main airplane batteries: Minimum temperature storage is -20°C. The batteries should be removed and stored in an area warmer than -20°C.
    • Life Rafts: Minimum temperature storage limit is -30°C
    • Fire Extinguisher – Kidde Aerospace, Halon: Minimum temperature storage limit is -40°C.
    • Fire Extinguisher – Amerex, Halon: Minimum temperature storage limit is -65°C.
    images

    Photo: Water tank draining determination table, AOM, §03-01-130, Table 1
    Click photo for a larger image

    images

    Photo: Galley equipment heating table, AOM, §03-01-130, Table 2
    Click photo for a larger image


See Also:

Gulfstream GVII-G500 Aircraft Operating Manual, Revision 5, January 31, 2020

Gulfstream GVII-G500 Airplane Flight Manual Supplement No. GVII-G500-2020-01, Anti-Ice and De-Ice Fluids, Basic Issue, January 31, 2020

Gulfstream GVII-G500 Maintenance and Operations Letter G500-MOL-20-0003, Ice and Rain Protection (ATA 30) - Approved Anti-ice and Deice Fluid Update, January 31, 2019