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Ice and Rain System Abnormals

Gulfstream G450 Abnormals


 

Cowl Anti-Ice Duct Pressure High

The big question here is what is meant by "if feasible?" If you can depart icing conditions, sure, do that. But what if you can't?

The pressure in the cowl anti-ice duct should be influenced more by its on-side engine, just due to proximity, but it can get air from the cross-side engine too. Let's say you have the high duct pressure indications on the left engine and can't exit icing conditions. I would pull the left engine to idle, knowing from experience the engine will not produce over 33 psi of bleed pressure at idle. Now the pressure in the common duct manifold is the only source of pressure and if it is below 33 psi and the high duct pressure message remains, chances are the pressure transducer is not working correctly. Obviously you still attempt to leave icing conditions, but look at that CAS message a little more suspiciously.

CAS:

Cowl Anti-Ice Hi, L-R

Synoptics:

[G450 AOM, §2A-30-30 ¶2.A.] The anti-iced portion of the engine cowl is represented by a colored band at the front of the graphic depicting each engine. The band is shown in white when the engine is not running. If the engine is running and cowl anti-ice is selected on and the bleed air pressure to the cowl is between 1.6 and 33.0 psi, the band is shown in green. If bleed air pressure is less than 1.6 or greater than 33.0 psi the band is shown in amber. If the pressure transducer data is invalid, the band is displayed in a dim white.

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QRH:

[G450 QRH, §MB-22]

  1. Select L-R COWL ANTI-ICE switches to OFF, if feasible.
  2. Depart icing conditions.
  3. Avoid icing conditions for remainder of flight.

Analysis:

[G450 AOM, §2A-30-30 ¶1.] Although the pressure transducer is capable of monitoring a pressure range from 0 - 75 psi, the normal pressure within the duct with the cowl anti-ice operating is between 0 - 33 psi. The MWS monitors the MAU furnished data and will issue an amber caution CAS message if either left or right duct pressure exceeds 33 psi.

Cowl Anti-Ice Valve Failed

Knowing how the valve works can help here:

  • If the valve is stuck open and you want to close it, you need electrical power to tell the valve to close and bleed pressure to move it. You need to ensure the circuit breaker is closed so it gets the "close signal."
  • If the valve is stuck closed and you want to open it, you need to remove power to the valve and pressure to open it. Assuming the switch is at fault, you can pull the circuit breaker and that should do it. Increasing bleed pressure by increasing engine thrust may help. If this doesn't work, you need to depart icing conditions.

CAS:

Cowl Anti-Ice Valve Fail Open, L-R

Cowl Anti-Ice Valve Fail Closed, L-R

Synoptics:

[G450 AOM, §2A-30-30 ¶1.A.] Two contacts within the valve provide position sensing data to the Modular Avionics Units (MAUs). The left engine valve position is reported to MAU #1, the right engine valve to MAU #2. The position contacts confirm that the valve is either open or closed, and the respective MAU compares actual valve position to the commanded position by monitoring the selector switch position on the ANTI-ICE panel on the cockpit overhead, and the position commands from the corresponding ice detector if the selector switch is in the AUTO position. The MAUs communicate valve position to the Monitor and Warning System that in turn formats Crew Alerting System (CAS) messages for display apprising the crew of cowl anti-ice performance.

While you don't have an indication of the cowl anti-ice valve's position on the synoptics, the blue Cowl Anti-Ice On, L-R CAS message indicates the valve switch believes it is open. Checking the cowl anti-ice pressure on the ECS synoptics can confirm this.

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Analysis:

With no electrical power is spring-loaded open. So if you need the valve open and the switch isn't helping you, pulling the appropriate circuit breaker should give you cowl anti-ice.

QRH: Cowl Valve Failed Closed, L-R

[G450 QRH, §MB-23]

    If in flight, depart icing conditions.

    If on ground, check CBs:

  1. L COWL ANTI-ICE: LEER, D-3
  2. R COWL ANTI-ICE: REER, D-14
  3. If anti-ice protection is required, pull affected CB. If system not regained, depart icing conditions.

QRH: Cowl Valve Failed Open, L-R

[G450 QRH, §MB-23]

    If on ground, check CBs:

  1. L COWL ANTI-ICE: LEER, D-3
  2. R COWL ANTI-ICE: REER, D-14
  3. Verify bleed air available with engine running.

    If in flight, continue and write up for maintenance action.

Ice Detect Failed

If your automatic ice detector fails, you become the ice detector.

CAS:

Ice Detect Fail, L-R

Symptoms:

The CAS may be your only indication.

Analysis:

The AFM permits you to operate with the following limitations:

[G450 AFM, §1-30-20] 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 AFM, §1-30-30] Use of cowl anti-icing is required for taxi and takeoff when Static Air Temperature (SAT) is +10°C (50°F) or below and visible moisture, precipitation, or wet runway are present. When taxiing or holding on the ground at low power in temperatures less than +1°C, engine operation of 85% LP for two (2) seconds is recommended just prior to takeoff. At intervals of not more than 60 minutes, under these temperature and moisture conditions, accelerate the engines to 85% LP, pause for 1 minute, then resume operations.

[G450 AFM, §1-30-30] Use of cowl anti-icing system is required in flight as indicated in Figure 1-5, Temperature Range for Cowl Anti-Icing, when visible moisture or precipitation is present or when signs of icing are observed. Ice accretion may be observed on wings or windshield edges.

[G450 AFM, §1-30-30] Increase in engine vibration levels may develop in icing. The fan should normally shed the ice and vibration will return to normal. To assist in shedding ice, if high vibration occurs and operational circumstances permit, one engine at a time may be quickly retarded to idle, held there for 5 seconds and then accelerated to 85% LP for 2 seconds, the power lever may then be returned to its original position.

[G450 AFM, §1-30-30] Automatic anti-ice is inhibited above 35,000 ft. If anti-ice protection above 35,000 ft is required, it must be manually selected.

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QRH:

[G450 QRH, §MB-37] Check CBs

  • L ICE DET: LEER, F-3
  • L ICE CTRL: LEER, E-3
  • R ICE DET: REER, F-14
  • R ICE CTRL: REER, E-14

If not in icing conditions, select L / R COWL and WING ANTI ICE to OFF. If icing conditions are expected, select L / R COWL and WING ANTI ICE to ON. Do not use AUTO settings.

If on the ground, dispatch with reference to MEL.

MEL:

[G450 MMEL, §Pg 30-3] Item 7. Ice Detection Systems

Repair Category: C

Number Installed: 2

Number Required for Dispatch: 0

Remarks and Exceptions: (O) May be inoperative provided airplane is operated in accordance with alternate AFM procedures.

Windshield Failed

These CAS messages are purely reports from the Window Heat Control Units which measure the resistance from each heating sensor. They can indicate the heating unit is bad or the sensor is failed. A cracked window or windshield could cause either to fail. So if you get one of these CAS messages, you should inspect the glass..

We used to get these a lot and the first question that will confront you when you see it for the first time is this: do I have an outer pane (good) or inner pane (bad) cracked? You might be able to see the paralax of an outer pane crack by looking at the inner pane at an angle. If you suspect an inner pane, run a credit card at a 90° angle into the crack. If you can feel the crack through the card, you have an inner pane crack. While I've lost more than my share of outer panes, I've never heard on an inner pane going on a Gulfstream.

CAS:

Front Windshield Fail, L-R

Side Windshield Fail, L-R

Symptoms:

You may or may not get the indicated CAS messages, and you may or may not notice a crack in a window. On the other hand, a windshield crack can sound like a gun fired at short range.

Analysis:

[G450 QRH, §MB 33] Indicated front windshield heat controller has failed or both temperature sensors in windshield have failed.

[G450 QRH, §MB-46] Indicated side windshield heat controller has failed or both temperature sensors in windshield have failed.

[G450 AMM, §56-11-00 ¶2.A.(3)] The front windshield outer glass ply is not a structural component but an abrasion coating. A cracked windshield outer glass ply, being made of tempered glass, may shatter into numerous pieces, expected to be 4 - 6 square inches in area, but may vary in size. The pieces are expected to remain in place and provide residual vision adequate to continue the flight. Bird impact and hail impact protection are expected to be retained, but anti-ice may not be functional. Should windshield heat be lost, flight into known icing conditions should be avoided.

QRH:

[G450 AFM, §3-24-10]

    If windshield heat failure is detected:
  1. Affected WINDSHIELD HEAT ... OFF, THEN ON
  2. If windshield heat cannot be regained:
  3. Affected WINDSHIELD HEAT ... OFF
  4. NOTE: Flight may be continued, but flight into icing conditions should be avoided.

    If windshield heat failure involves a front window:
  5. Affected Windshield Heat CB ... PULL
    L FRONT WSHLD: POP, B-2
    R FRONT WSHLD: CPOP, B-2
  6. NOTE: If needed (after the affected circuit breaker has been pulled), heat can be restored to the remaining side window by selecting the affected windshield heat switch back to ON.

    If a crack is detected in outer heating ply or protective ply of the windshield:
  7. Affected Windshield Heat CB ... PULL
    Front Windshield:
    L FRONT WSHLD: POP, B-2
    R FRONT WSHLD: CPOP, B-2
    Side Windshield:
    L SIDE WSHLD: CPOP, A-1
    R SIDE WSHLD: POP, A-1
  8. NOTE: Flight may be continued, but flight into icing conditions should be avoided.

    If a crack in either main structural windshield ply is detected:

    WARNING: IF CRACKING IS TO THE INNER GLASS PLY, IT IS RECOMMENDED THAT THE PILOT ADJACENT TO THE CRACK AREA WEAR EYE PROTECTION SUCH AS SMOKE GOGGLES.

  9. AUTO / SEMI ... SEMI
  10. Cabin Differential Pressure (DFRN PRESS) ... REDUCE TO 7.5 PSI
  11. Descent Altitude ... DESCEND BELOW 35,000 FEET
  12. Airplane Altitude ... ESTABLISH
  13. ALTITUDE TO CONTROL DFRN PRESS TO 7.5 PSI OR LESS

  14. Cabin Altitude (CABIN ALT) ... ADJUST TO 7,900 FEET
  15. Airspeed / Mach ... MAINTAIN CURRENT OR SLOWER SPEED

Wing Anti-Ice Fail

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Photo: ECS/Pressurization Synoptics, from Eddie's aircraft.

If you have one side working and the other failed, you can treat it as shown in G450 Wing Temperature Low to fool the system into ramping up the bleed temperature and getting both wings warm. More about this system: G450 Wing Anti-Ice System.

Symptoms

You could have any or all of the following:

  • Wing Anti-Ice Fail, L-R CAS,
  • The ECS/Pressurization page may show the indicated wing is unheated,
  • Icing indications on one wing

Analysis:

[G450 Aircraft Operating Manual, §2A-30-40, ¶3.B.] The Wing Anti-Ice Fail, L-R CAS message monitors the wing anti-ice control valve and the bleed air controller.

[G450 Aircraft Operating Manual, §2A-30-40, ¶2.A.] A crossover duct is installed between the two supply ducts to allow a single engine to supply heated air to both wings if necessary. One way check valves upstream of the crossover duct prevent the flow of bleed air back to the inoperative engine or anti-ice control valve. When only one engine bleed air source is available for wing anti-ice, the BAC of the remaining engine increases the temperature within the bleed air manifold to 500°F by decreasing the flow of fan stage air through the pre-cooler.

If you are relying on the crossover duct, you can increase the temperature of the air sent to the wing anti-ice system by shutting an ECS pack off.

Procedure

[G450 Airplane Flight Manual, §03-25-00, page 03-147]

  • Select affected Bleed Air Switch to ON. Select bleed air on side with the associated failure.
  • Select affected ECS Pack to OFF. Select pack OFF on side with the associated failure.
  • The temperature of the bleed air duct should go from 400°F to 500*F and affected side should rise to above 100°F which will extinguish the Wing Temperature Low CAS message.

  • If both wings are not heated, depart icing conditions

Wing Hot

The problem is either the affected side's wing anti-ice valve is stuck full open or the controller on that side is failing to modulate it. Either way, turning the affected wing anti-ice selector to off will close the affected valve, bump up the bleed temperature to 500°F, and heat the wing through the cross over valve. That should fix it.

CAS

Wing Hot, L-R

Analysis

The CAS message illuminates when sensors detect air at the wing tips greater than 180°F, this may be your only indication. More information at: G450 Ice and Rain System

QRH Procedure

[G450 QRH, §MB-51]

  1. Select affected WING ANTI-ICE selector knob to OFF.
  2. Select the ECS/Pressure synoptic page and compare wing temperatures to ensure that remaining side system is providing anti-ice protection.
  3. If both wings are not heated, or if both L and R Wing Hot messages are displayed simultaneously, select both WING ANTI ICE selector knobs to OFF and depart icing conditions.

Wing Temperature Low

This was a common problem in the GIII and GIV but starting with the GV, the bleed air system uses two sources of bleed air from each engine. The G450 uses the 7th and 12th stages, the problem has become a rare one. The Wing Temperature Low message is inhibited for two minutes after selecting WING ANTI ICE ON, so that would be the time to expect it. What can be done?

Recall that the bleed air system uses 500°F bleed air cooled to 400°F after the precooler, unless wing anti-ice is in use. With wing anti-ice on, the air from the engines is allowed to reach 570°F but the precooler output remains at 400°F unless single engine or operating with one wing anti-ice valve failed closed, then it bumps up to 500°F. We can make use of that knowledge.

Scenario: Right Wing Temperature Low (both engines operating)

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By turning the right wing anti-ice switch to OFF, we can fool the bleed air controller into raising the bleed duct to 500°F and hope for better right wing temperatures through the cross-over duct:

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The book doesn't offer this procedure but it works and doesn't violate any limitations.

CAS

Wing Temperature Low, L-R

QRH

[G450 QRH, §MB-52]

  1. Increase thrust if flight conditions permit.
  2. If message not extinguished:
    1. Monitor wings for icing.
    2. Depart icing conditions as soon as possible.

Analysis

The wing anti-ice system uses 400°F bleed air to warm the wing leading edges to 130°F (target) and will warn you if the wings get too warm (180°F) or not warm enough (100°F). The QRH isn't very helpful.

References

* FSI G450 PTM, FlightSafety International Gulfstream G450 Pilot Training Manual, Volume 2, Aircraft Systems, October 2008

* FSI G450 MTM, FlightSafety International Gulfstream G450 Maintenance Training Manual, August 2008

Gulfstream GV, GV-SP, GV-SP (G550), GV-SP (G500), GIV-X, GIV-X (G450), GIV-X (G350) Master Minimum Equipment List, Revision 07, February 4, 2010.

Gulfstream G450 Aircraft Operating Manual, Revision 35, April 30, 2013.

Gulfstream G450 Airplane Flight Manual, Revision 36, December 5, 2013

Gulfstream G450 Maintenance Manual, Revision 18, Dec 12, 2013

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—Eddie

Revision: 20150722
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