Source: http://code7700.com/g450_cold_weather.htm
Timestamp: 2019-04-21 00:41:33+00:00

Document:
Cold weather operations involve more than just meeting the de-ice truck before takeoff and letting the engine and wing anti-ice do their jobs. Ignoring or skipping steps can be dangerous, as with Air Florida Flight 90. It can also be costly, as many pilots of older Gulfstreams found out the hard way.
There are certain rules and regulations you should be familiar with, especially the fact that you probably are not entitled to use published holdover times in lieu of a pre-takeoff contamination check.
Under 14 CFR 91 we do not have approved ground icing and anti-icing programs. Very few 14 CFR 135 operators are approved.
We are required to conduct a pre-takeoff contamination check at some point.
If the airplane was completely free of contamination during the preflight check, or following deicing/anti-icing, AND conditions have not been conducive to further accumulation, we are good to go.
If, however, conditions have been conducive to further accumulation, we must perform a a pre-takeoff contamination check within 5 minutes of takeoff.
See Cold Weather Operations for more.
The G450 Aircraft Operating Manual includes several key temperatures that must be noted prior to leaving the aircraft in a cold weather environment. Failing to follow cold weather procedures can be very expensive.
Ensure the cabin pressure outflow valve is closed.
Ensure wheel chocks are in place and the parking brake is released. If moisture has entered the brake assembly, releasing parking brake will forestall the possibility of brakes freezing in this position.
Ensure external protective covers and plugs are installed.
Ensure the main cabin door, baggage compartment door and all access doors are closed to prevent snow or rain from entering the airplane.
Figure: Water Tank Draining Determination Table, from G450 Aircraft Operating Manual, §07-01-20, Table 1.
[G450 Aircraft Operating Manual, §07-01-20, ¶20.A.(5)] The servicing of potable water and waste water tanks must be completed as soon as possible after flight and will depend on the ambient temperature and the cold-soak period. See [the table] to determine if it is necessary to drain water storage compartments.
Many Gulfstream pilots have returned to their airplanes to a water system that was completely frozen and, once warmed up, was leaking from nose to tail with burst water pipes. The repair costs are enormous. It seems like a terrible bother when the temperature is hovering around freezing and you are probably okay without taking these precautions. Take them, we have water system purge techniques that make it as painless as possible.
You may also need to download all freezables or at least relocate them to a cooler that will contain any spillage if a container does burst.
G450 Aircraft Operating Manual §07-01-20 §20.A.(7)] If the main airplane batteries will be exposed to temperature below -20°C (0°F), the batteries should be removed and stored in an area warmer than -20°C (0°F), but below 40°C (104°F).
The batteries are heavy, the aft equipment door is narrow and high off the ground. This is a two-person job and it isn’t easy! We've decided we would rather relocate the airplane if the temperature is this cold and hangar space isn't available.
G450 Aircraft Operating Manual §07-01-20 §20.A.(6)] If the life rafts are expected to be exposed to temperatures below -28°C (-20°F), it is recommended that they be removed from the airplane. At temperatures lower than -28°C (-20°F), the CO2 cartridge may discharge.
Remove enough snow and ice to gain entrance and operate the APU.
(1) Ensure all protective covers and plugs are removed.
(2) 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.
(3) While in the cockpit, ensure the parking brake (PARK/EMERG BRAKE) handle is in the released (off) position.
(4) Ensure the wing, including leading edges, all control surfaces, tab surfaces and balance panel cavities, wing trailing edge, flight control actuators, cable runs, and push rods are free of ice or snow. If ice or snow was removed, recheck control balance cavities for drainage as puddled water may refreeze in flight.
(5) Ensure the APU inlet is clear of impacted ice or snow.
(6) Ensure the engine inlets are clear of internal ice or snow. Verify the LP compressor rotates freely.
(7) Ensure accessible fuel tank vents are clear of all traces of ice or snow.
(8) Ensure pitot tubes and static ports are clear. Water rundown resulting from snow removal may refreeze immediately forward of static ports and cause an ice buildup which causes disturbed airflow over the static ports and erroneous static reading even though static ports themselves are clear.
(9) Ensure landing gear and landing gear doors are unobstructed and free of impacted ice or snow.
(10) Ensure brakes, wheels and wheel wells are clear of snow, slush, or ice. Clean as necessary using a non-damaging mechanical means. Use hot air for frozen brakes. Avoid chemical deicer.
If the airplane is covered in ice, your best bet maybe to find a warm hangar to to de-ice the airplane before entering. Your efforts can be improved with careful brooming and other means of manually removing the snow. The APU inlet and surrounding areas must be free of snow or ice that could be ingested. The pressurization outflow valve must be free to open.
(1) Verify the air inlets and exits are clear of ice or snow.
(2) Ensure outflow and pressure relief valves are free of impacted ice or snow and are unobstructed.
(3) If APU is operating with APU AIR selected to ON, ensure the outflow valve and pressure relief valve are fully open.
(4) Verify the pressure relief valve static port is clear, as water rundown may refreeze.
Ensure the main airplane batteries are reinstalled and connected.
(1) Select the APU MASTER switch to ON. Selecting the APU MASTER ON powers the APU Electronic Control Unit (ECU). The ECU performs a power-up Built-In-Test (BIT) and signals the APU air inlet door to open. If all parameters are determined to be acceptable for APU start, the APU READY light is illuminated. It should be noted that APU starting is not inhibited with the absence of the READY light. Thus, if the flight crew deems that time is critical, the option of proceeding with APU start is still available due to the protection features provided. Even with the READY light not illuminated, automatic shutdown protection is provided for the APU in the Non-Essential (Ground) mode, and automatic start prevention is provided for the APU in the Essential (Flight) mode. If, in the interest of time, the flight crew elects to perform an APU start with the absence of the READY light, the APU air inlet door must be verified to be open prior to attempting start.
(2) If overnight temperatures were -15°C (+5°F) or colder, the APU EGT and RPM displays (cockpit overhead panel) may be unreadable.
(3) Depending on the ambient temperature and condition of the battery, it is possible that a slower-than-normal APU start may occur.
(4) 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.
Figure: APU Start Procedure, from Haskel Notes.
...the APU start must be made without using a DU for the APU fire test.
We used to teach checking underneath the guarded fire extinguisher switch to ensure the bottle wasn't discharged. More than a few pilots inadvertently discharged the bottle doing this, and for no good reason. The light will not illuminate with a discharged bottle so this check is unnecessary. If the bottle is discharged, you will get a CAS message once the DUs are powered. The pressurization FAULT light has nothing to do with the APU, it is a check of an AC ESS Bus Relay that can only be checked with both MAIN AC buses unpowered.
G450 Aircraft Operating Manual §07-01-20 §5.C.(5)] Airplane heating is accomplished using APU AIR and the air conditioning (L and R ECS) PACKS. Heating can be expedited by closing both main entry and baggage compartment doors.
Note that the procedure no longer requires pulling the SFC and STBY EBDI circuit breakers in this situation.
G450 Aircraft Operating Manual §07-01-20 ¶2.A.] Confirm purge/supply valve integrity by performing a water system purge and supply operational check in accordance with water system instructions. Instructions for purging of the water system are readily available on the inside of the water system cabinet cover.
There is a specific order to the steps needs to bring the potable water system back to life. To ensure water doesn’t freeze as it enters cold pipes, allow the system to warm up for 20 minutes prior to servicing the water tank. Turn on the water system and press and hold System Heat for three seconds to activate the system heaters.
G450 Aircraft Operating Manual §07-01-20 ¶2.B.] Ensure the water system line heaters are energized 20 minutes prior to resetting and servicing the water system after a system purge.
When servicing an empty system, it is important to remember to open all the faucets and wait for water to start flowing before turning on the Lav and Galley Water Heaters. This bleeds out trapped air in the Water Heater tanks and allows them to fill with water. If the tanks are heated without water in them, they may overheat and trip the internal thermostat, causing the units to fail.
More on this subject at G450 Water System Purge.
G450 Aircraft Operating Manual §07-01-20 §6.A(1)] The following procedures are required any time engine oil temperature is -10°C or colder.
(1) Minimum oil temperature for starting -40°C.
(2) Ensure the parking brake (PARK/EMERG BRAKE) is engaged (on).
(3) Manually select the left and right generator switches (L GEN / R GEN) to OFF prior to engine start. This allows the IDG oil to warm with the IDG unloaded and prevents nuisance underspeed/underfrequency trips due to high oil viscosity. Select generators on as required once the engines have stabilized at idle.
NOTE: If the L GEN / R GEN switches are not manually selected OFF prior to start, and the L (R) Generator Fail and/or L (R) AC Power Fail CAS messages are observed as the engine achieves idle, select the affected GEN switch to OFF for fifteen (15) seconds, then back to ON.
[GAC-OMS-01 §1.] Section 1, Limitations, Altitude/Temperature Operating Envelope is amended to show the minimum temperature limits as -70° C (GIV/G300/G400/G350/G450) and -80° C (GV/G500/G550) at all altitudes, provided procedures in this supplement are complied with.
G450 Aircraft Operating Manual §07-01-20 §6.B] To ensure the engines are ready for start, run each engine through a crank cycle using Steps (1) through (4) that follow. Alternatively, Steps (1) through (4) may be performed in conjunction with Step 5C(1) of Starting Procedure.
Allow LP and HP rotation to achieve maximum levels.
If the start valve does not open or no rotation is achieved, discontinue the crank cycle.
If the start valve still does not open, the valve should be manually overridden. See Section 09-03-40, Manually Overriding Starter Air Valve.
If the start valve does not indicate open or air duct pressure drop is not observed, the start valve solenoid may be frozen. Ground heating may be necessary to warm the start valve. Start engine as soon as possible after thawing to prevent refreezing.
When do you need to do this? The book doesn't say so we asked Gulfstream and were told a crank cycle is needed if the aircraft had a prolonged cold soak between -30°C and -40°C. How do you know the airplane is cold soaked to this degree? We keep a refrigerator magnet in one of the cockpit cubby holes. If it reads -30°C, the airplane is cold soaked.
Note this is oil temperature. The OAT could be -10°C and the interior of the airplane could be that cold, and the oil temperature could be higher.
CAUTION: BE ALERT FOR POTENTIAL HOT START INDICATIONS.
NOTE: If the start is aborted, perform a crank cycle prior to attempting another start.
NOTE: Minimum oil temperature to accelerate engines for taxi power is -30ºC.
NOTE: During ground idle power operation at extremely cold ambient temperatures, continuous ignition may be automatically activated concurrent with increased engine bleed. Continuous ignition will be indicated on the engine instruments and increased bleed will result in an audible change in engine noise. Steady state engine operation and performance is not impacted. This condition is self clearing when the throttles are advanced from ground idle.
(1) Prior to selecting the Fuel Control (FUEL CONT) switch to ON, allow each engine to achieve maximum LP and HP rotation, and then stabilize for forty-five (45) seconds. Use an outside observer to visually confirm positive LP rotation.
NOTE: Engine start light-off following extended exposure to cold weather will be abrupt because the start fuel schedule increases initial fuel flow. The airplane will respond accordingly with a significant engine rumble of a short duration.
(2) If the Turbine Gas Temperature (TGT) exceeds start limits, FADEC will automatically abort the start. Before attempting further start attempts, a dry crank for a minimum of 30 seconds should be carried out followed by a start in accordance with normal procedures. Maximum TGT allowed prior to start is 200°C. A crank cycle can be used to reduce TGT prior to the next start attempt.
(3) After both engines are started, complete the After Starting Engines checklist. Minimum oil temperature to accelerate engines for taxi power is -30°C. It is recommended that all engine parameters achieve normal range values prior to flight.
De-ice procedures prior to engine start are particularly useful if icing conditions have ceased or are expected to be time consuming. Anti-icing can also be applied if convenient and taxi times are minimal.
If icing conditions persist, however, the pre-flight inspection check does not replace the need for a pretakeoff contamination check.
Taxi as soon as possible after engine start.
Avoid puddles and slush when possible.
Use brakes to build up BRAKE TEMPS to a minimum temperature of 100°C. This aids in dissipating any moisture in the brakes.
When stopped, perform several brake applications to 3000 psi. This exercises the brake stacks, discouraging ice buildup.
Avoid the temptation to set the parking brake for any length of time.
Nose wheel steering must be used with care or nose wheel skidding may occur on all types of 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. Excessive speed will present problems in making turns or stopping. Maintain increased separation between airplane when taxiing on ice or snow covered taxiways. Be aware that blasted ice or snow can cause damage at considerable distances.
Idle reverse thrust can be used during taxi to reduce brake usage on clean, paved taxiways and runways. Do not use idle reverse thrust during taxi on snow or slush covered taxiways. It is a natural tendency to use reverse thrust when braking action is poor. However, areas which have been cleaned with snow removal equipment usually have chunks of snow and ice remaining. These conditions are especially conducive to Foreign Object Damage (FOD). Exercise extreme caution.
If taxi route is through slush or standing water in low temperature, taxi with flaps up. Taxiing with flaps extended will subject the flaps and flap actuators to snow and slush accumulations from the main gear tires.
Takeoff is prohibited with frost, ice, snow, or slush adhering to the wings, control surfaces, engine inlets, or other critical surfaces.
The atmospheric conditions have been conducive to frost formation.
You did this during the preflight inspection. If the airplane was found free of any frost, ice, snow, or slush and the conditions are not conducive to further accumulation, you are good to go. Likewise, if you de-iced the airplane to a satisfactory state the conditions are not conducive to further accumulation, you are again good to go. But if the aircraft did not pass these tests or the conditions are conducive to further accumulation, you must deice. Why?
See Cold Weather Operations for the legal reasons.
Photo: Heated or Cold, from Haskel notes.
If following de-ice conditions conducive to further accumulation remain, anti-icing comes next . . .
Deice / Anti-Ice With Engines Running?
to personnel at inlet or exhaust areas.
Ensure L / R COWL ANTI ICE switches are selected OFF.
Ensure L ENG / R ENG / APU AIR switches are selected OFF.
Ensure the outflow valve is CLOSED.
We deice with our engines running routinely, making sure we fully brief the deice operator to avoid the engine intakes.
G450 Aircraft Operating Manual §07-01-10 §5] Any time the recommended holdover time is exceeded, a pre-takeoff inspection is required.
Of course that assumes you are allowed to use those holdover times in the first place. Can you? Under 14 CFR 91 you can until you can't; there is nothing in writing that says you can. So who can? That is covered by AC 120-60B Ground Icing and Anti-Icing Program. This advisory circular outlines the establishment of a ground deicing/anti-icing program under 14 CFR 121.629 and further covers 14 CFR 135 crews who have been trained under its provisions. These crews are allowed to use the holdover tables in lieu of a pretakeoff contamination check provided the people applying the deice/anti-ice have also been trained under 121.629. See Cold Weather Operations for more.
Once the preflight inspection is complete, the airplane is clean and adequately protected, the airplane should depart as soon as possible. This is especially important in conditions of precipitation or high relative humidity (small temperature / dew point spread).
Configure COWL / WING ANTI ICE as required.
G450 Aircraft Operating Manual §07-01-10 §7.A.(3)] COWL / WING ANTI ICE must be ON during all ground and flight operations when icing conditions exist or are anticipated. Vibration levels may rise and fall as spontaneous ice shedding occurs.
Just prior to takeoff, accelerate the engine to 85 percent LP RPM, pause for two (2) seconds to check normal engine operation, then select takeoff thrust.
At intervals of not more than 60 minutes, accelerate the engine to 85 percent LP RPM, pause for one (1) minute, then resume idle operations. Note: Any momentary increase in vibration noted during acceleration and deceleration may be disregarded. In certain heavy icing conditions, similar intermittent increases in vibration may occur, but should subside soon after icing has ceased.
DO NOT use reduced (FLEX) thrust.
Accomplish an engine run-up to as high thrust as possible and check for STABLE engine operation BEFORE brake release.
Takeoff and accelerate-stop distances and V1 speeds are based on smooth, dry, hard surface runways with no credit for reverse thrust. The stopping distance increases on slippery runways. The minimum allowable V1 speed should be used.
Caution should be used for takeoffs on slippery runways with high crosswinds or when slush or wet snow is present. During takeoff in slush, a slush and water bow wave forms in front of the landing gear wheels, growing in size with increasing speed. The acceleration rate during the low speed portion of the takeoff roll is about normal, but may deteriorate during the high speed portion. Slush and/or water can accumulate on the leading edge and then freeze during climb. WING ANTI ICE should be selected to ON for takeoff. In addition, it is possible to sustain damage on the lower fuselage and wing area from the slush thrown up from the wheels.
After setting rated takeoff Engine Pressure Ratio (EPR), verify LP RPM and other engine indications are normal by 60 knots - Engine display page indicating needles all at approximately “nine o’clock” position or higher.
If the decision is made to reject the takeoff and the runway is slick, deploy ground spoilers, use maximum reverse thrust and maximum anti-skid braking. Resist the temptation to release brakes during anti-skid braking even if the ride is very rough. For directional control, use the rudder primarily down to 50 knots. The anti-skid system will provide the minimum stopping distance for the existing condition of the runway.
If a loss of directional control develops, reduce reverse thrust to idle reverse. Use rudder pedal steering, if possible, for directional control. The nose steering wheel, rudder and differential braking may also be used as necessary for directional control.
Rotate to normal takeoff attitude at VR - NOT BEFORE.
Delay gear retraction if practical. This allows water, slush, and snow to be slung off as wheels spin down.
If possible, cycling the gear once or twice may further reduce accumulations and will reduce the possibility of gear door or brake freezing.
After climbing above 1,500 feet AGL, WING ANTI ICE will automatically be selected to ON if ice is detected. This will vent warm air into the wheel well area and assist in melting any ice on the wheels.
In-flight Anti-Icing . . .
[G450 Airplane Operating Manual §1-30-10] Icing conditions also exist when the SAT on the ground and for takeoff is +10°C (50°F) or below when operating on ramps, taxiways or runways where surface snow, ice, standing water, or slush may be ingested by the engines or freeze on engines, nacelles, or engine sensor probes.
Photo: G450 Winglet and navigation light from Eddie's cockpit.
We don't have a reliable spot forward of the windscreen to detect ice, such as a windshield wiper post or other protrusion. You can often spot a layer of ice on the winglet and a buildup on the navigation light, both of which are unheated.
[G450 Airplane Operating Manual §1-30-10] Icing conditions exist when the SAT on the ground and for takeoff, or SAT in-flight is +10°C (50°F) or below, and visible moisture in any form is present (such as clouds, fog with visibility of one mile or less, rain, snow, sleet and ice crystals).
[G450 Airplane Operating Manual §1-30-10] Operation of wing anti-icing is required if icing conditions are imminent, or immediately upon detection of ice formation on wings, winglets, or windshield edges.
G450 Aircraft Operating Manual §2A-30-20 ¶1.] Because extracting bleed air from the engine decreases engine thrust, automatic anti-icing is not available below fifteen hundred (1,500) feet where full engine capability is reserved for takeoff and landing. However, if automatic anti-icing had been selected at a higher altitude, it remains operational in descent below 1,500 feet, since engine thrust requirements are minimized in descents, and engine cowls and wing surfaces must be kept clear of ice in preparation for landing. Automatic anti-icing is also not available above thirty-five thousand (35,000) feet, since air temperatures and moisture content are extremely low and icing conditions unlikely. Engine bleed air can then be fully employed in meeting the demands of pressurization and cabin heating.
The system works on initial climb from 1,500' AGL to 35,000' and on descent from 35,000' to touchdown.
G450 Aircraft Operating Manual §07-01-10 §15.A.] Engine icing can occur without wing icing. A jet engine operating in an air mass with an ambient temperature below 8°C may experience engine icing. This is caused by the temperature drop associated with the reduction in pressure between that of the air mass and the pressure at the first stages of the compressor. As air is drawn into the engine, moisture condenses into droplets. These droplets, due to their inertia, cannot follow the air around the fan blades and guide vanes. Instead, they strike the metal parts and freeze. This can happen in clear air if the temperature is near or below freezing and the relative humidity is near saturation. The APU is also affected.
To assist in shedding ice and reduce vibration indications, should operational circumstances permit, one power lever at a time may be quickly retarded to idle, held there for five (5) seconds and then advanced to 85 percent LP RPM for approximately two (2) seconds. The power lever may then be returned to its original setting.
G450 Aircraft Operating Manual §07-01-10 §14.C.(3)(a)] Wing Stall is not an uncommon consequence of ice accretion. Ice from freezing drizzle can form sharp-edged roughness elements approximately 5 to 10 mm high over a large chordwise expanse of the wing lower surface (perhaps covering 30 to 50 percent), and the fuselage. This increases drag dramatically, thereby reducing speed. Proper airspeed control will minimize the potential for wing stall. Correcting for ice accumulation demands increased power, increased AOA, or both, to maintain altitude. If actual stall is encountered (identified by wing roll-off), lower the nose (decrease AOA), accept any altitude loss required to recover from the stall, then increase power after recovery and return to previously assigned altitude.
G450 Aircraft Operating Manual §07-01-10 §14.C.(3)(b)] Tailplane Stall in a Gulfstream airplane has not been experienced but can occur in icing conditions as the airplane is configured for landing. If tailplane stall does occur (identified by pitch down), retract flaps to the previous position and raise the nose to increase AOA, while slowing airspeed to minimum maneuvering speed for the current flap setting. After recovery, increase power and return to previously assigned altitude.
G450 Aircraft Operating Manual §07-01-10 §15.B.(2)] If any heating element malfunctions in the pilot’s, copilot’s or standby systems, immediate action should be taken, when practical, to exit icing conditions. Since the pitot tubes supply both pitot and static pressure, all pitot-static instruments - Air Data Modules (ADMs), Flight Data Recorders (FDRs), and the engines will be affected by pitot icing. Failure of pitot system probe heat will be evident to the crew by huge errors in airspeed and altimeter indications.
G450 Aircraft Operating Manual §07-01-10 §15.C.] If any [AOA] heater malfunctions, the stall barrier protection systems will be affected. Select the Stall Barrier (STALL BARR) system to OFF and maintain minimum maneuvering speeds or faster for the remainder of the flight.
If all three airspeed indicators are unreliable, or if you just don't know which is telling the truth, the AOA should indicate between 0.2 and 0.3 at cruise speeds, around 0.4 at approach speeds, and 0.5 when at VREF. While the pitch limit indicator comes on at 0.70 during the test, it could appear sooner depending on other factors.
See Angle of Attack for more on AOA.
If the AOA indication is suspect, you also have an excellent indicator of speed over the ground in your GPS. Just remember to consider the effects of wind and altitude.
Your deck angle is also an excellent surrogate for AOA. In the cruise mode, the pitch is normally around 3 to 5 degrees nose up. This angle holds true on approach properly configured with flaps. In the go around mode, 10 degrees nose up will keep you safe.
See Deck Angle for more about this technique.
It is recommended that landing gear be extended earlier than normal.
The temperature of the landing gear will equal that of the surrounding total air temperature within three to five minutes.
Select ANTI SKID to OFF, perform several brake applications to 3000 psi, then select ANTI SKID to ON for landing.
Ensure ground spoilers are armed (GND SPLR switch selected to ARMED).
Perform firm touchdown to reduce strength of ice bond on brakes.
At main gear contact with the runway, ground spoilers should deploy automatically. Manual speed brake deployment is a recommended backup procedure.
Lower nose wheel to the runway immediately as the ground spoilers and thrust reversers are being deployed.
Apply brakes smoothly and symmetrically with moderate-to-firm pressure until a safe stop is assured.
Allow the anti-skid system perform its function. Do not attempt to cycle brake pedal pressure if the anti-skid is "releasing." Maintain constant brake pedal pressure.
DO NOT use asymmetric reverse thrust on icy or slippery runways.
Be prepared for possible downwind drift on slippery runways with a crosswind when using reverse thrust.
DO NOT attempt to turn off the runway until attaining a safe, very slow, taxi speed.

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