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Oral Exam Questions - B1900D


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Your oil pressure is fluctuating by 10 psi, is this acceptable?
Yes, as long as pressure is 90-135 psi
What are two failures that will cause the ENG ICE FAIL annunciator to illuminate?
Immediate illumination: loss of electrical power, delayed illumination: inoperative actuator.
What is Max Take-off torque?
3950 ft-lbs
What is MAX Take-off ITT?
800 C
What is the normal oil pressure range
90-135 psi
What is a compressor stall?
At low N1 RPM, axial flow compressor stages produce more compressed air than the centrifugal stage can use. A compressor bleed valve compensates for excess airflow at low rpm by bleeding axial stage to reduce backpressure.
What is Max ITT for cruise?
760 C
What is the Torque limit if the primary governor fails? Why?
3538 ft-lbs Shaft Horsepower limit of 1279 SHP
What is the Torque limit if the oil pressure is less than 90 psi? Why?
2000 ft-lbs
Oil pressure below 90 psi is undesirable and tolerated only for completion of flight
What is the likely cause of a hung start at 38%? At 44%?
Stuck P2.5 valve
14 secondary nozzles not introducing fuel to the engine.
What should you do if you encounter a hung start?
Move condition lever to Fuel Cutoff and set the Ignition and Engine Start Switch to OFF. Follow engine Clearing or Restart procedures.
During start you notice fuel flow, but no ITT, what's the likely problem?
The ignitors are not on
What causes the L or R Fuel PRES annunciator to illuminate?
Fuel pressure below 5 psi STANDBY PUMP ON (failed side) consult checklist
Any limitations with the Fuel PRESS LO annunciator on?
Operation is limited to 10 hours before overhaul or replacement of the high pressure engine-driven fuel pump.
Can you depart with the Fuel PRESS LO annunicator on?
No, consult maint.
After pulling the Left T-handle, the L FW VALVE annunciator illuminates and stays lit, what does that indicate?
Left FW Valve has not reached its selected position
When are you supposed to use Auto-Ignition?
Used when runway contaminated, precipitation, icing or turbulence expected.
What is MAX ITT for start?
1000 C for 5 seconds
If the primary gov fails in flight, with an RPM of 1450 selected, what will control prop RPM?
Fuel Topping Governor
If the primary gov fails in flight, with an RPM of 1700 selected, what will control prop RPM?
OVerspeed Governor
If the low pitch solenoid burns out, what will happen to the prop in flight? On the ground?
On landing, will stay at flight idle until the power levers are lifted over the idle stop
If the cable to the prop control breaks, what will happen to prop RPM?
It will go to 1700
If the manual feather fails to feather the prop in cruise, how else could you feather the prop?
Arm autofeather, power full forward. If torquemeter oil pressure on either engine drops below 350 ft-lbs, oil is dumped from done, feathering starts the blades toward feather and AFX of other engine is disarmed
If the L Fuel QTY Annunciator illuminates what does that indicate?
LEss than 324 lbs fuel in tank - land as soon as practicable
If the R COL TANK LO annunciator illuminates what does that indicate?
Less than 53 lbs. LAND!
Can you MEL the Engine Driven boost pump? Limitation?
Yes. 10 hours before overhaul of high pressure engine driven fuel pump
Which standby bost pump must be operative to transfer fuel from the Left tank to the Right Tank?
The left engine standby boost pump must be operative.
Illumination of the XFER VALVE FAIL annunciator indicates?
The annunciator is activated if the transfer valve fails to move to its assigned position within 2 seconds.
If the cable to the prop breaks, what will happen to prop RPM?
It will go to 1700 RPM
If you pull the Left Condition lever to cut off in flight the engine will shut down, what should happen to the prop?
If AFX is inop, the prop will maintain on speed RPM unless feathered manually.
If the Engine Driven Boost Pump and the Standby Pump both fail, what happens to the engine?
Cavitation of the High Pressure Boost Pump is possible?
If both the Engine Driven Boost pump and Standby Pump fail, can fuel still get into the collector tank?
Yes Through Motive Flow and gravity feed.
What is the fuel transfer rate from Aux Tank to MAin Tank?
1.3 gallons per minute or 500lbs/hour
What is the power source for the firewall shutoff valves?
Hot Battery Bus
What is the maximum fuel imbalance between wing tank systmes?
200 lbs
If the Aux Tank Fuel Pump is inop, is the fuel in the Aux tank usable?
What is the situation - Gear Handle Down, Red light illuminated, CB not popped, one gear down position light is NOT illuminated
Gear is likely safe, proceed with checklist, Drag Brace Switch is the likely cause
What is the situation - GEAR Handle down, Red Light Illuminated, CB IS popped, one gear light is NOT illuminated.
Gear likely NOT safe - proceed with checklist and manually extend gear.
What is the maximum fuel imbalance between wing tank systems?
200 lbs
What is the situation, Gear Handle Down, Red light NOT illuminated, CB NOT popped, gear down position light is NOT illuminated.
Gear light may be burned out, Proceed with checklist
Where does the alternate extension system gets its fluid?
The fluid is inside the reservoir in the main reservoir.
What indications would you expect if the hydraulic accumulator failed?
The hydraulic power pack would run more frequently.
Explain how the landing gear - gear up warning systems operates?
Flaps 17 and power retarded below approx 84-86% NI, horn will sound and handle illuminate if gear up. Beyond 17 flaps illumination and horn regardless of N1.
What does it mean when the HYD FLUID LOW annunciator is illuminated
Hydraulic Fluid is low. If gear fails to extend normally follow checklist.
After manual extension of gear red handle light is still on, what should you do?
Continue pumping until max resistance is felt and leave handle at the top of the stroke. Keep landing before and after landing.
A failure of which bus would render the landing gear motor inoperative?
Center Bus
A failure of which bus would render the landing gear indication system inoperative?
Triple Fed Bus
May you takeoff with the Yellow MAN STEER FAIL annunciator illuminated?
Where is the Hydraulic Power Pack located?
Left Inboard Wing
How do we check brake wear?
Wear pins should be visible
What is thermal runaway?
Thermal runaway is battery meltdown due to increasing temperature and decreasing resistance and increasing voltage.
What cockpit indications would lead us to suspect thermal runaway? What would you do?
Battery charge with voltmeter increasing or not decreasing.
What kind of battery do we have?
During cruise your L GEN TIE OPEN annunciator has illuminated, what equipment have you lost? What action do you take?
Nothing. Monitor L load meter, if less than 100% Bus Sense switch to RESET. If greater than 100%, turn off appropriate GEN and monitor opposite loadmeter not to exceed 100%
During cruise L AND R GEN TIE OPEN, L and R DC GEN, STALL HEAT, R ENVIR OFF, and R ENVIR FAIL lights illuminate, what has happened? Have you lost any equipment?
Dual Gen failure. Lost equipment, perform checklist.
In relation to the other buses, what should the voltage of the Triple Fed Bus be?
1 volt less - Diodes
During an electrical system check you find that the voltage of the TFB and other buses are the same. Is this normal?
NO - Diodes of the TFB have failed
How is AC power generated on the Beech 1900
By 2 AC Inverters
Where do the inverters get their power?
The #1 inverter is powered by the left generator bus and the left center bus. The #2 inverter is powered by the right generator bus and the right center bus.
What AC voltages do the inverters provide?
115 volt and 26 volt AC
What failure of what AC voltage triggers the L or R AC Bus Fail annunciators?
115 VAC
How is the failure of the 26-volt side of an inverter detected?
Instruments associated with it fail - Nav #1, RMI #2)
A Dual AC Bus failure has occurred, what is the correct response?
Use standy attitude indicator and Compass for attitude and heading control - Use checklist
What happens to the EFIS during a Dual Gen failure?
Depending on the strength of the battery, the captain's tube may stay illuminated for a short period of time. The FO's will blank out right away. Power can be restored by man-ties closed.
If neither generator will reset, will the landing gear work?
Extend gear manually
If neither generator will reset, will the flaps work?
No, Do not extend flaps if you elect to close the ties - to much of a drain.
If neither generator will reset will the prop deice work?
No, not without placing Gen Ties switch in Man Close and severly limiting battery duration.
What is the minimum voltage for a Battery Start? GPU start?
23 Volts, 20 Volts
If you have a dual BLEED air failure what flight instruments have you lost?
None, however the flight hour meter is inop
You are taxiing on a hot day, cold air is coming out of the eye ball vents and warm air is coming out of the floor vents, what steps could you take to further cool the cabin?
Open all the eyeball vents and allow time for bypass valve to close completely.
Does placing the TEMP control on full hot position warm up the cabin any faster than in the "normal" in-flight range.
What causes the CABIN DIFF Hi annunciator to come on? What action are you going to take?
Cabin diff exceeds 5.25 PSI, Bleed Air Valves to Envir. Off Oxygen as requried and descend as required.
What is the minimum oxygen quantity required for flight above 15,000ft?
1250 psi avg.
Which instruments use vacuum air pressure?
No flight instruments use vacuum pressure, however the Flight Hour Meter and vacuum gauge do use vacuum pressure.
Vfe Flaps 17
Vfe Flaps 35
Vmo sea level to 13,200
Vmo 13,200 to 25,000 ft
Emergency Descent Target Speed?
Maximum Range Glide
Turbulent Air Penetration
Holding Speed
Maximum Ramp Weight
Maximum Structural Take-Off Weight
Maximum Structural Landing Weight
Maximum Weight in Forward Cabin Baggage Compartment
250 pounds
What is the weight limitation of the closet hanger?
100 pounds
Aft Baggage Compartment - Forward Section
Aft Section - Aft Baggage Compartment

Weight Limitations?
630 pounds
Special Airports
National, Harrisburg, Binghamton, Wilkes-Barre, Burlington, Elmira, Saranac Lake, Charleston, Roanoke, Rutland
Who is the prop manufacturer?
What changes the propeller blade angle?
Oil pressure in the prop dome.
How many prop governors are there on the PT6A-67D engine?
3. Primary gov, hydraulic overspeed gov and the fuel topping governor.
What is the purpose of the primary governor?
Controls the propeller through its normal operating range.
What is the purpose of the hydraulic overspeed governor?
Prevents the prop from exceeding 1802 RPM in the event of a primary governor failure.
What is the purpose of the fuel topping governor?
Prevents power turbine overspeed by reducing fuel to the FCU, if the propellor exceeds 106% of selected prop RPM ( 96% in reverse condition)
How does the primary governor work?
Pilot valve speeder spring tension is controlled by the prop levers to counteract a flyweight in order to maintain an on-speed condition within the normal operating range of 1395-1700 RPM. It also allows for the manual feathering of the propellor.
You shut down the left engine to load another bag, how long must you wait before restarting the engine?
3 minute cool down from when the starter was turned off
What are the normal starter limits for an aborted start, clearing and restart?
20 seconds on, 30 seconds off

20 seconds on, 60 sec. off

20 secs on, 5 minutes off
Is an emergency evacuation (for a fire) required, if you are 100% sure the fire is extinguished and the situation no longer poses an immediate threat?
Not necessarily required. PIC has emergency authority
Will the Fire Extinguishing system operate without pulling the T handle?
No, the fire T handle must be pulled to arm the fire extinguisher push button circuitry.
What should happen to the Red T handle light after the fire has been extinguished.
Should go out after fire detect amplifier detects temperatures within limits.
Will the Fire Extinguishing system operate with the battery switch gang-bar off?
Yes, the fire extinguisher control switches are powered from the hot battery bus.
Will the Fire detection system operate with the loop broken?
In the event of a single break, the system remains operational, however the resistance at which the fire is sensed will change.
You are scheduled to fly 4 hours today and 3.5 hours tomorrow, due to ATC you fly 6.5. Can you still fly 3.5 hours with 8 hours rest?
You are scheduled to fly 7.5 hours but you have to divert, you exceed 8 hours, is this legal?
Yes but you MUST have compensatory rest.
Describe rest requirements for any 24 hour period.
Scheduled Flight <8 <9 9+
Rest 9 10 11
Reduced 8 8 9
Comp. 10 11 12
You are scheduled to fly 4 days in a row followed by 3 days of Ground School without 24 hours off, is this legal?
How many hours may you legally be scheduled to fly in a 7 day period?
34 hours
May we exceed a MRB day?
Can we carry dead-heading crew members on a ferry flight?
When aircraft characteristics have not been appreciably altered or flight operations are not affected substantially, company personnel may, with approval of dispatch, DO and PIC be carried on board.
Are we allowed to ferry an aircraft if something is inop that is not in the MEL?
Is a dispatch release required for a ferry flight?
Yes, and filed under a CommutAir call sign
Can we MEL the left Gen?
What type of ice is associated with freezing rain?
The mins for ILS 1 in ALB is 1/2 mile, tower visibility is reported as 1/4 mile, surface vis is 3/4 mile, may you execute this approach?
No Tower visibility is controlling in this situation.
The minimums for the ILS 4 in ROC is 1800 RVR, the tower is reporting the RVR is 1400 variable 2000, may you execute this approach?
No The variable portion is advisory only - not controlling.
The F/O has less than 100 hours, what are the restrictions?
Cannot take-off or land under the following:

Special Airports
Vis less than 3/4 mile
RVR less than 4000
Runway less than bare and dry
Braking action less than good
15 knot crosswing
Windshear reported
PIC discretion
When may we use the call sign, Life-Flight or Life-Guard?
If passengers remain on the aircraft on a through flight, who must stay with them? What is the PAX are non-revenue?
For both situations, a qualified crew member only - not Ramp personnel
Can a seeing eye dog occupy the forward cabin closet?
What is max landing weight?
What is Max Zero Fuel Weight?
You have 213 lbs of airfreight - what do you put on the LM1?
Look on the back of the RIC book
What is Max Allowable Take-Off Weight and how is it determined?
Lesser of:
MATOW for runway intended
MATOW considering enroute performance limits
MATOW considering landing limitations
MATOW considering landing distance limits
What weather do you need at your destination before you can depart?
Approriate weather reports and forecasts to indicate WX will be at or above landings minimums at ETA
When is a full power takeoff required?
First flight of day - cannot reduce
Runway contaminated - can reduce
Performance reasons - can reduce
Do you need a dispatch release to reposition an aircraft under FAR Part 91?
You are diverting to your alternate, is an amended release required?
Do you need an amended release if you are on the ground for more than one hour?
Yes, on a multiple leg release an amended release is required. (Block in to Wheels Up)
Do you need an amended release if your destination weather goes below minimums enroute?
Do you need an amended release to go to a different destination?
Diversion to a designated weather alternate does not require an amended release.

Diversion to any other airport does require an amended release unless PIC declares an emergency.
On a VFR release may we depart IFR and cancel in the air?
List the 4 company requirements when doing a low RVR take-off.
No Intersection departures
No tailwind
Torque set prior to brake release
Designate takeoff alternate
What is the lowest take-off min we may use if we don't have CL or RCLM's?
RVV 1/4 SM or TDZ RVR 1600
TDZ RVR is controlling
Mid RVR may be substituted with one of the following
Operative HIRL
Operative CL
Adequate Vis Ref.
With all the RVR's, what if the the RCLM's are obscured by snow?
TDZ RVR 1200 and Rollout RVR 1000 with CL and 2 operating reporting systems.
(mid RVR may be substituted for either)
(Tower vis may also be substituted with inop TDZ if prevailing vis is favorable)
What is the lowest take-off minimum we may use?
600, 600, 6000

If one RVR has failed, Takeoff authorized with remaining 2 RVR values of 600 or greater.
Describe in detail the wx requirements for FAR 121 VFR.
Departure and Arrival airport = 3000/5
Enroute = Current and Forecast vis of 5 SM or greater AND ceiling to cruise below reported or forecast ceiling between 6000-18,000 MSL or 3000 AGL whichever is higher
Where will the Take-off alternate be written down?
Dispatch release in the remarks section
Can PLB be used as an alternate based on ILS mins?
No - See chart, approach plate 11-1
After leaving gate, ops calls you back for an extra pax, do you need an amended release?
Yes, for any flight interruption.
While enroute to destination the forecast for destination goes below mins, is an amended release needed?
No amended release needed.
Need required visibility before reaching the FAF
While enroute to destination your alternate goes below mins, what happens?
Dispatcher is required to issue an amended release
When is a second alternate required?
Both destination AND 1st alternate ETA forecast wx is Marginal

(Marginal = celiing within 100 ft OR vis is within 1/2)

3585 Exemption
Describe how the 3585 exemption works?
Relief from conditional remarks (at destination and/or alternate)
Main body at or above required mins
2 alternates
Forecast wx for one of the 2 alternates is at or above mins in BOTH main body and remarks
WX update enroute
"Released under 3585" stated on release
What weather do we need to consider when determining if an alternate is usable?
When selecting an alternate airport, how are alternate minimums determined?
Method 1
One or more navigation aids
Add 400 & 1 to ANY approach minimum

Method 2
2 or more nav aids to straight-in approaches to DIFFERENT AND SUITABLE runways
Add 200 to higher ceiling
Add 1/2 vis to higher vis

NEVER lower than 400 & 1
When is a take-off alternate required?
When departure airport weather is below PIC landing mins.

Must be within 1 hour on 1 engine in still air (150 miles for us)
When are you required to list an alternate for a destination airport?

123 Rule (time, ceiling, vis)
Takeoff Alternate
Supplemental = operations outside of our defined route structure

Cabin Door or Cargo Door Annunciator
Which bus may fail without an annunciation? How do you check it?
TFB fault Check with overhead meter
Why do we use the fuel in the aux tank first?
Because a loss of electrical power or failure of the transfer pump will prevent the use of the aux tank fuel.
Name our special airports.
Washington National, Harrisburg, Binghamton, Wilkes-Barre, Burlington, Elmira, Saranac, Charleston WV, Roanoke, Rutland
What are the requirements for landing at a special airport?
Within the past 12 months the PIC or SIC has made a takeoff and landing while serving as a crewmemeber. OR PIC has qualified using pictorial means for that airport
Is there a grace month associated with the 12 month requirement for special airports?
If your qualification for a particular special airport has expired under what circumstances may you land if the pictorial review is unavailable?
Weather is 3 miles OR 1000 feet above lowest MOCA, MEA or Initial approach alitude for the instrument approach.
Can we carry HAZMAT?
What items of HAZMAT may we carry?
Small items:
self-defense spray - 4 fluid oz
May we carry small arms ammunition?
In checked baggage only.
How does the hydraulic overspeed governor (HOG)work?
The HOG speeder spring tension is set to oppose the flyweight at a speed of 1802 RPM. If the propeller speed increases above 1802 oil is released from the prop dome, which causes the prop blade to move to a coarser pitch preventing further overspeed.
How does the fuel topping governor work?
The gov compares N1 speed to power lever setting and adjusts the fuel flow to the FCU. Fuel may be reduced to min flow.
What is the low pitch stop?
A mechanically monitored, hydraulic stop.
What is the blade angle for Feather?
79 degrees
What is the blade angle for cruise?
What is the blade angle for Flight Idle?
What is the blade angle for Ground Idle?
What is the blade angle for Ground Fine?
What is the blade angle for Reverse?
How does BETA and reverse work?
Power levers change the position of the low pitch stop
What happens when you move the power levers?
The speeder spring on the N1 governor in the FCU is reset, which causes the FCU to increase, or decrease the fuel flow.
What happens when you move the prop levers?
Pilot indirectly controls the pilot valve by resetting the speeder spring withing the range of 1395-1700 RPM.
What happens when you move the prop levers rearward?
The pilot valve moves up, allowing oil to be removed from the dome, moving the blade angle to a coarser pitch.
What are the limits of the fuel topping governor?
In the ALPHA and BETA range, the fuel topping gov is set to 106% of the primary gov. In reverse range, the gov is reset to 96% of the primary gov.
Why is the fuel topping gov reset to 96% of the primary gov, in reverse?
To maintain an underspeed condition, which ensures that the prop will remain on the low-pitch stop.
What will happen if the primary gov control linkage were to fail?
An external spring on top of the gov will move the gov to a set speed of 1700 RPM
How does the Autofeather system work?
With AFX in ARM, when power levers are advanced above 90% N1, with torques above 1000ft-lbs, the power lever quadrant microswitches close. This illuminates the L/R AFX annunciator lights
What happens if the torque drops below 1000 ft-lbs and AFX is armed? And continues to fall below 350 ft-lbs?
The opposite engine AFX system is deactived. Below 350ft-lbs the associated AFX dump valve is powered to ground. IT will open and release oil from dome and will feather prop.
What happens when the AFX system is in TEST position?
The power quadrant microswitches are overridden.
When a propeller has autofeathered, what annunciator light changes occur?
The L/R AUTO FEATHER and AFX annunciators extinguish and the AFX DISABLE annunciator illuminates.
Is the propeller synchrophase a master-slave system?
No The slower prop is matched to the faster prop
Within how many RPM must the two propellers be for the prop synchrophaser to operate?
25 RPM
What is the path of the fuel from the collector tank to the engine?
Collector Tank, Manifold, Manual Shutoff Valve, Fuel Filter, Firewall shutoff valve, low pressure boost pump (45 psi), fuel-oil heat exchanger, high pressure boost pump (850 psi), fuel flow transmitter, to the nozzles
What is the total quantity of usable fuel?
1621, 621, 4484
What happens if the engine driven low pressure pump fails?
The L/R FUEL PRES LO annunciator illuminates. The high pressure pump suction feeds the engine to keep it running
What does the primary jet pump do?
By use of motive flow, it takes fuel from the collector tank and directs it towards the engine.
How is the collector tank filled?
From the main tank by gravity feed and two jet transfer pumps
What powers the firewall shutoff valves?
The hot battery bus or the opposite generator bus
How does the purge tank operate?
The tank pressurizes with P3 air when the engine is operating. During shutdown, pressure is released to push the remaining fuel into the manifold.
What happens when the fuel transfer switch is turned ON?
The standby pump (11 psi) is energized, the transfer valve opens, and the white FUEL TRANSFER annunciator illuminates.
What is the source of power for the standby pump?
Center Bus
What happens if the low pressure pump and the standby pump are inoperative?
Fuel will be suction fed to the engine by the high pressure pump
What are the limitations for suction feeding?
10 hours of operation before the high pressure pump needs to be overhauled or replaced
With the AUX pump switch in AUTO, what conditions must be met for fuel to transfer?
Fuel in the AUX tank and motive flow (engine running)
What happens if the L/R NO AUX XFR annunciator illuminates, but fuel is in the AUX tank?
Fuel is not transferring from the AUX tank to the collector tank.
What should the pilot do if the above situation is encountered?
Place associated AUX pump switch in the ON position. if the L/R/ NO AUX XFR annunciator remains illuminated, flight time may be limited do to loss of fuel availablity. Monitor the other AUX tank quantity to remain within balance limits.
What is the maximum fuel imbalance?
200 lbs
What turns OFF the auxiliary tank fuel pump?
Pump overheat (thermal cutout switch)
Loss of Motive Flow (10 psi switch)
AUX tank empty (float switch)
No Transfer (5 psi switch)
or pump switch to OFF position
How is fuel transferred into the auxiliary tank?
Thermal expansion only
Does the AUX tank gravity feed into the collector tank?
What is indicated if the FUEL TRANSFER annunciator is illuminated and the XFR VALVE FAIL annunciator is illuminated and stays ON after the fuel transfer switch is placed to the OFF position?
The transfer valve is fully open
When will the L/R FUEL QTY annunciator illuminate?
When the fuel sensor in the associated tank indicates less than 324 lbs of fuel remaining.
What is indicated if the XFR VALVE FAIL annunciator light remains illuminated, but the FUEL TRANSFER annunciator extinguishes, when the fuel transfer switch is placed in the OFF position?
The transfer valve is partially open
When does the visual fuel quantity indicator show RED?
When the fuel quantity is less than 1150 lbs on the outboard viewport, or less than 745 lbs on the inboard viewport
What are the limitations regarding the use of Avgas?
150 hours max of operation before engine overhaul, standby pumps must be operational and ON for takeoff and landing, and altitude not greateer than 180 MSL
What is indicated when the COL TANK LOW annunciator light is illuminated?
The fuel sensor in the associated collector tank indicates less than 53 lbs of fuel remaining.
What 2 fuel system components are lost with a dual generator failure?
The auxiliary fuel transfer pumps and the fuel vent heaters
What supplies DC electrical power to the aircraft?
DC Power is supplied by a 24 volt, 34 amp hour NICAD battery and two 28 volt, 300 amp starter/generators
What is normal system voltage?
27.5-29 volts DC
What is indicated by a BATT TIE OPEN annunciator illuminating?
The HED has opened the battery tie relay, isolating the battery from the center bus
What is the indication of a of a short on the left generator bus?
L GEN TIE OPEN and L DC GEN annunciators illuminate. The HED has sensed an excessive current flow and opens the left generator tie relay. The GCU opens the generator line contactor.
What happens when you get a short on the triple fed bus?
The voltage indicator reads zero volts in the TPL BUS position. All three 60 amp current limiters have blown
What closes the generator ties?
External power available and EXT PWR switch ON, generator on line, or MAN TIES CLOSED
What does the GCU do?
Provides votage regulation, line contactor control, overvoltage and overexcitation protection, paralleling and load sharing, reverse current protection, and cross start current limiting.
What supplies AC power to the aircraft?
By two inverters
What types of AC power are produced?
26 volt, 400 hz for engine instruments and some avionics; 115 volt, 400 hz for most avionics.
How are the inverters powered?
#1 off L Generator Bus, or the center if L GEN is unpowered
#2 is powered off R GEN, or Center if unpowered
What can be done if an inverter fails?
All of the items powered by the failed inverter can be transferred to the operating inverter by placing the failed inverters switch to the TRANSFER position
Why is the battery switch turned ON before the external power switch?
To prevent electrical spikes to the avionics
What does the white circle around certain switches indicate?
They are powered by either the center bus or the triple fed bus.
What is the rated output of the generators?
28.0 to 28.5 volts DC and 300 amps
What are the indications of a severe short on the center bus?
BATT TIE OPEN, L GEN TIE, and R GEN TIE annunciators illuminate and zero volts on the center bus
What electrical system protection is provided during the start cycle?
All HED's are desensitized to prevent the battery tie and generator tie relays from opening.
Regulated to 28.0-28.5 volts
Gen voltage within .5 volts of aircraft voltage. GCU closes line contactor connecting gen to gen bus; both gen ties are closed connecting the gen busses to the center bus; provides power to the battery charger and all aircraft systems
Generator will be disconnected if its output exceeds 32 volts
Load balance within 10% when total load is above 25%
If a generator is unable to produce 28.0-28.5 volts, it will draw power from the aircraft electrical system. The GCU will open the line contactor, isolating that generator
During cross start, the GCU controls the generator output to 400 amps
What does the external power high voltage sensor do?
It prevents the external power relay from closing when the voltage exceeds 32 +/-.5 volts
What are the battery voltage limits for starting?
23 volts for battery start
20 volts for an external power start
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