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Stack #2221433

APU Study Guide

QuestionAnswer
Explain the APU Exhaust Gas Temperature (EGT). The EGT system is a thermocouple thermometer that is not dependent upon the aircraft electrical system for operation.
Fuel supply for the APU is gravity fed from what tank? The No. 2 main tank surge box.
There are three indicator lights for the APU what do the three different colors mean? Red - DOOR OPEN ; Amber - START ; Green - ON SPEED
The APU oil tank holds how many quarts, but has a total capacity of how many quarts with the tank, lines, and oil cooler full of oil? 4 quarts / 6 quarts
The No. 2 main tank must have a minimum of __________ lbs of fuel for APU operation. 2,000
The ____________ ____________ motor provides the initial cranking to achieve combustion and assists the turbine until the APU reaches ____% RPM? Electric starting motor / 35% RPM
The APU EGT limits are what? 260-650 degrees C
Explain the APU Starter Duty Cycle. The starter duty cycle is the amount of time that the starter can be engaged without causing damage to the starter. 1 minute on 4 minutes off and does not change in cold weather.
When the APU door opens to _____ degree position, power is then supplied to the _________, the start light, and to the holding circuits. 15 degree / starter
At approximately 35% RPM, what occurs within the operating system? The 35% switch opens, de-energizing the starter and start light and the APU is now under its own power, and acceleration continues.
At 95% RPM, what occurs? Power is connected to the BLEED AIR VALVE switch and the ON SPEED switch. Once full speed is reached the governor assumes control and limits rotation to 100% RPM.
In case of governor failure, the overspeed switch prevents the turbine from exceeding ______ percent by opening the circuit to the fuel shutoff valve holding relay, thus securing fuel 110% RPM
At approximately 35% RPM, the START light will go out. If the light does not go out what should be done? If the light does not go out within 1 minute, move the APU CONTROL switch to STOP and wait 4 minutes before making another start attempt. The starter duty cycle is 1 min on 4 min off. Do not reengage the starter while the turbine is rotating.
What should be done if isolated DC power is interrupted while the APU is operating? If this occurs the control circuit will be opened, causing the unit to stop. Place the APU CONTROL switch to STOP and perform the APU starting procedures.
If the APU does not light off during ground start in extreme cold weather, what should be done? Preheat the APU with an external source of heat prior to second start attempt.
Ensure the APU is on speed and warmed up for a minimum of how long? 1 minute
The APU will shut down and the door will close after oil pressure drops to approximately what PSI and RPM? 20 PSI and 18% RPM
APU Fire Bold Face. 1. APU fire handle - Pulled (CP) 2. Fire Extinguisher - (Discharged as required) (CP) a. If condition persists, isolate the wing b. If condition persists, discharge the remaining wing 3. APU Generator - OFF (FE) 4. Evacuate
What is the warm-up / cool down minimum time to apply or remove a load? 1. 1 min warm up before applying a load 2. 1 min after removing a load to shut down 3. 4 min for startup in cold weather operations
Identify what will happen at 35% RPM APU limit. At 35% amber light goes out which shows the starter has disengaged. If performing a battery start you will need to untie the ground bus tie switch prior to actuation of the starter. Once the amber light goes out, you are clear to re-tie the bus.
Identify what will happen at 95% RPM APU limit. This is when the green light comes on and it illuminates when the APU reaches a stable speed.
What is the normal operating limits for APU? 95-105%
What is the max RPM for the APU and when it is reached what should be done? 106% and shut down
Identify what will happen at 110% RPM APU limit. The overspeed switch will automatically shut down the APU by taking fuel flow away.
Identify the Generator Frequency, Voltage, and Load Frequency: 380-420 Hertz Voltage: 110-125 Volts Load: AC: 0-1.05 DC: 0-1.03
When the APU handle is pulled, the APU is isolated as follows: 1. Fuel Shutoff Valve is closed 2. The bleed air valve is closed 3. The fire extinguisher system directional flow valve is positioned for routing the agent. 4. Extinguisher AGENT DISCHARGE switch is armed and APU door closes
When starting the APU with battery power leave the bus tie switch ___________ until the APU reaches _____ percent (start light out), then ______ the DC buss to arm the APU fire detection system. Untied / 35% / Tie
When operating the APU with less than 2,000 lbs of fuel in the No. 2 tank (minimum requirement), what should be done? Turn the fuel boost pump ON to maintain surge-box fuel level.
What should be done in the event of a Cargo Compartment Refrigerator Overheat Warning Light? 1. Cargo Compt air conditioning shut off switch - OFF (FE) 2. UNDERFLOOR HEATING switch - OFF (FE) 3. APU CONTROL switch - STOP (FE) 4. BLEED AIR DIVIDER VALVE - CLOSED (FE) 5. NO. 3 and NO. 4 ENG BLEED AIR switches - OFF (FE)
What should the battery voltage be when checking it? 25-30 VDC
Observe the bleed air manifold for minimum of how many PSI? 35 PSI
When moving the engine bleed air regulators to the override position this closes the bleed air valve, and the manifold pressure should drop in what time? 30 PSI to 15 PSI in no less than 20 seconds IAW 2-4 and 16 seconds for NATOPS
What should be done for a wing leading edge overheat? ANTI-ICING WING switch - OFF (FE) If the affected leading edge
Created by: Sam2121