737 B-Loss of Both Engine Driven Generators

 

B737NG

BRIEFINGS 

What you should see on the Electrical Panel •

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First indication of loss of both engine driven generators is a MASTER CAUTION illumination with multiple caution lights and instruments warnings flags on both panels. [including TRANSFER BUS OFF, SOURCE OFF and GEN OFF BUS] Caution! Don’t be confused with « loss of both engines ». To discriminate between the two situations, advance the thrust levers and check if engines respond. Check also if ENG FAIL is displayed on both EGT indicators.

STBY AC BUS and STBY DC BUS automatically switch to their back-up source upon loss of both engine driven generators. The STANDBY PWR OFF amber light should not be illuminated! If you see this light illuminated, the first check-list to be started [before the LOSS OF BOTH ENGINE DRIVEN GENERATORS] is the STANDBY POWER OFF NNC

STANDBY PWR OFF Light Illuminated (amber) (amber) – one or more of the following busses are unpowered: • AC standby bus • DC standby bus • Battery bus.

QRH

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What is the purpose of the STANDBY POWER Switch? AUTO (guarded position) In flight, or on the ground, and AC transfer t ransfer busses powered: powered: • AC standby bus is powered by AC transfer bus 1 • DC standby bus is powered by TR1, TR2 and TR3 In flight, or on the ground, loss of all AC power  • AC standby bus is powered by battery through static inverter  • DC standby bus is powered by battery • Battery bus is powered by battery. OFF (center position) • STANDBY PWR OFF light illuminates • AC standby bus, static inverter, and DC standby bus are not powered. BAT (unguarded position) • AC standby bus bus is powered by battery through static static inverter  • DC standby bus bus and battery bus bus are powered directly by battery. When placing the Standby Power Switch to BAT, the STANDBY PWR OFF amber light should extinguish.

CAUTION! If the STANDBY PWR OFF light is illuminated after a loss of both engine driven generators 1) Unpowered Unpowered AC Standby bus means, at least (non-exhaustive list): - ATC 1 [XPDFR] INOP - Right Igniters INOP [No [No more igniters!] - ADF No.1 INOP - GPS No.1 INOP [No [No more GPS!] - Fuel Quantity indicators INOP 2) Unpowered Unpowered DC Standby bus means, at least (non-exhaustive list): - VHF1 INOP [No [No more VHF!] - Engine No.1 thrust reverser INOP - NAV1 INOP [No more NAV capability!] - EFIS Control panel INOP - Stick shaker captain INOP 3) Unpowered Unpowered Battery bus means, at least (non-exhaustive list): - Engine 1 & 2 start lever Chan A+B INOP - Engine 1 & 2 Fire Protection INOP - Fuel Engine 1 & 2 HPSOV INOP - Landing Gear Air Ground relays + Alternate Extend solenoid INOP - Standby attitude indicator INOP - N1 & EGT INOP, etc, etc

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Example: B737-800 [Dual battery equipped]

BUS TRANSFER Switch - AUTO (guarded (guarded position) position) BTBs operate automatically to maintain power  to AC transfer busses from any operating generator or external power  [DC cross tie relay automatically provides normal or isolated operation as required]. - OFF Isolates AC transfer bus 1 from A C transfer bus 2 if one IDG is supplying power to both AC transfer busses [DC cross tie relay opens to isolate DC bus 1 from DC bus 2].

The breaker is behind the FO’s seat. The SPCU (Standby Power Control Unit) uses the battery & standby power switch position to control the distribution of AC & DC standby power. Heading – Enter through CDU FMC/CDU POS INIT page .......................... Select Enter the correct heading into the CDU scratch pad then press lineselect key 5R. Verify entered heading appears on line 5R. Select HDG on the IRS display selector and verify that the entered heading is displayed on the navigation displays.

Heading – Enter through ISDU IRS display selector ....................................... ........................................HDG .HDG Press the H key to initiate a heading entry. Key–in present magnetic heading. Press the ENT key (the cue lights extinguish). Observe proper heading displayed on the navigation displays.

Declare MAYDAY [Note: With only one generator available, declare PAN-PAN and land at the nearest  suitable airport].

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Takeoff, Approach and Landing on Standby Power  Boeing says that « the probability of a total and unrecoverable AC power failure is remote ». Because of system design, a NNC for accomplishing an approach & landing on standby power is not required. •

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Complete all applicable NNCs and approach preparations. Refer to Volume 2, Chapter 6 of your Boeing FCOM for a list of significant equipment powered by standby power.

The following list identifies the significant equipment that operates when the main battery and the auxiliary battery are the only source of electrical power (all generators INOP) on aircraft: SECTION

Airplane General

Air Systems

Anti-Ice Communications Electrical

Engines & APU

Fire Protection

OPERATIVE ITEMS • Standby compass light • White dome lights • Emergency instrument flood lights • Flight crew oxygen • Passenger oxygen • Standby forward airstair interior/exterior operation • A/C pack valves • BLEED TRIP OFF lights • Manual pressurization control • Atitude warning horn • PACK lights • Captain’s pitot probe heat

REMARKS - Automatic Passenger Passenger Oxygen Control & Release INOP (manual control is available) - AUTO & ALTN pressurization pressurization modes are INOP. Below 10,000 ft (or at lower if altitude) select MAN and open outflow valve to land unpressurized

• Flight interphone system • Service interphone system • Passenger address system • VHF No. 1 • STANDBY POWER OFF light • Upper display unit (N1, N2, fuel flow, EGT, fuel quantity, oil pressure, oil temperature, oil quantity) • Thrust reversers • Starter valves • Right igniters • APU operation (start attempts not recommended above 25,000 feet) • APU and engine fire extinguisher bottles • APU and engine fire detection system • Cargo fire extinguisher bottle

Flight Controls

• TE and LE Flaps

Flight Instruments

• Captain’s outboard display unit with PFD • Captain’s inboard display unit with ND • Clocks • Left EFIS control panel • Standby instruments (RMI, stdby airspeed/altimeter, stdby attitude indicator, stdby magnetic compass

- All TE and LE Flaps indications are INOP. TE & LE Flaps are available but without asymmetry protection (based on the pointers of the Flap indicator which is itself INOP): extend flaps step by step and monitor control wheel for any roll. - Electrical trim is INOP - Takeoff: Keep T/O flap setting + maneuvering speed: flap position indicator is INOP and flap retraction schedule is not available

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[Continuing]

SECTION

Flight Management Navigation

Fuel

Hydraulic Power  Landing Gear 

Warnings

OPERATIVE ITEMS [EI-DPF through EI-DPV] • left FMC [EI-CSA through EI-DPE] • FMC --------------------------------------------------------------------------------------------------------------------------------------• Left CDU • Heading/track indications • VHF NAV No. 1 • ILS No. 1 • Left IRS • Left GPS • Marker beacon • ADF No. 1 • DME No. 1 • Crossfeed valve • Engine fuel shutoff valves • Spar fuel shutoff valve • FUEL VALVE CLOSED lights • Fuel quantity indicators • Engine hydraulic shutoff valves • Standby rudder shutoff valves • Inboard antiskid system • ANTISKID INOP light • Parking brake • Air/ground system • Landing gear indicator lights • Stall warning system • Aural warnings • Master caution light Recall

REMARKS

- All fuel pumps are INOP: INOP: possible thrust deterioration or engine flameout at high altitude! - Fuel contained in Center tank is no longer available. (check possible overweight landing)

- Outboard Antiskid INOP [verify QRH Performance Inflight Advisory Information for landing distance!] - Autobrakes INOP

Basic Equipment Operating – Captain Instrument Panel [ aircraft] The standby power system utilizes the battery as a source of power to supply the below depicted flight instruments. All of the Captain’s instruments that are powered by standby power are integrally lighted on standby power 

Left Hand Seat (LHS) pilot is always PF

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After takeoff, climb to MSA and stay below 10,000 ASL because aircraft is unpressurized!

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Be careful: No altitude alert for level level off!

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Check MCP: in certain circumstances circumstances Reversion to Standby Standby power may cause the Barometric Barometric setting to revert to Standard. Altitude window could have switched to 50.000ft, MCP speed window to 110kt. Reset as necessary!

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Ask for vectors if available.

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Consider CAT I landing only to land back.

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If both primary attitude displays are INOP (see QRH), the IRS drifts like a conventional gyro: you need to update a heading entry every 15 minutes and before commencing the approach. Before entering the magnetic compass reading, correct the value for deviation thru t he compass deviation card. Always take your time for this process! PNF should have a good crosscheck with the PF before entering and executing any value into the ISDU or the CDU. Any wrong value entered by mistake could result in a space disorientation! disorientation! Should your remaining FMC be INOP, remember that you will have to set reference airspeed bugs for approach via the SPD REF knob [see Boeing Supplementary Procedures / Flight Instruments, displays]: Speed reference selector (outer) ....................................................WT [Default weight of 32,000 kgs / 70,000 lbs is displayed].

Speed reference selector (inner) .................. Set current gross weight [Flaps up maneuver speed bug is displayed].

Speed reference selector selector (outer) ................. ...............................VREF [Default speed of 80 knots is displayed].

Speed reference selector selector (inner) ...............................Set ....................... ........Set VREF speed The green VREF bug and white VREF +20 bug are shown when a speed greater  than 80 knots is set. Note: If V1 or VR i s selected in flight, INVALID ENTRY is displayed.

To set the spare bug, if desired: Speed reference selector selector (outer) ................. ....................... Spare bug [Default speed of 60 knots is displayed].

Speed reference selector (inner) ................................................... Set [Set speed as desired].

Speed reference selector (outer) ...................................................SET [Digital readout is removed].

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Fly the approach on speed. Because outboard anti-skid is not available, and with the higher approach speed, any excess speed is undesirable. undesirable. Bear in mind that auto speedbrake is INOP upon landing: extend speedbrake manually.

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Never abort your takeoff above 80 kt in case of loss of both engine driven generators because: - Antiskid is INOP - RTO mode is INOP Speedbrakes automatic extension is INOP - Speedbrakes Do not retract flaps after take off if possible (no severe icing conditions): flap position indicator is INOP and flap retraction schedule is not available In cruise, do not stay above 25,000 ft if the actual MORA permits it. Again, remember that APU start attempts are not recommended above 25,000 feet. Because of the loss of the engine fuel pumps, thrust deterioration or engine flameout is also a critical factor. Avoid Multiple start attempts attempts which would deplete the battery and and would reduce standby standby power  capacity: battery endurance would be definitely affected Avoid LNAV & VNAV selection before complete FMC pages check!

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