The device described in this manual is an Auxiliary Power Unit (APU) SAFIR 5L, manufactured by PBS Velká Bíteš, specialists in rotary machines. This manual provides instructions for technicians and mechanics supporting the operation of the SAFIR 5L APU, covering all work to be performed until the complete overhaul. Adherence to these instructions is crucial for reliable operation and endurance of the APU, and non-observance during operation or troubleshooting may void the warranty and absolve the manufacturer of liability for damages.
Function Description
The SAFIR 5L is a turbo-reactive engine with automatic control, designed as a single-stage, radial output compressor. Its primary function is to provide auxiliary power, likely for aircraft, given the references to "airplane" and "pilot's compartment." The APU's operation involves a complex interplay of fuel, oil, air, and control systems to ensure reliable starting, running, and shutdown.
Important Technical Specifications
General:
- Identification type: SAFIR 5L
- Description: Turbo-reactive engine with automatic control and air intake from compressor, single stage, radial output.
- Compressor: Single stage, radial.
- Combustion chamber: Annular.
- Turbine: Two-stage, axial flow.
- Operating speed (100%): 51,900 rpm.
- Idling speed (89%): 46,400 rpm.
- APU weight (without exhaust pipe): 31 kg.
- Power supply: Accumulator 24 V, 25 Ah (charged to at least 75% of its nominal capacity).
- Number of actuations per 1 charge of the accumulator: At least 4.
- Operation voltage range: 23.5 – 28.5 V.
- Height for start of APU and engine and air intake for the airplane air conditioning: 26,500 ft (8,000 m).
- Ambient temperature range for reliable function of APU: -60 °C to +60 °C (with restrictions under article 3.2).
- Time of APU operation in maximum mode (100%): 120 min. max.
- Repeatability of APU actuation and engine: See article 3.1.
- Fuel consumption: 70 kg/hour max.
- Oil consumption: 150 cm³/hour max.
Fuel System:
- Flow rate: 130±5 l/hour.
- Max. pressure: 1.3±0.1 MPa.
- Working fuel temperature: -40 to +60 °C.
- Block of Filter and Servo (P/N 490740.01): Filter efficiency 12 µm, switches on when pressure loss in the filter element reaches 35±9 kPa, turns on when pressure loss in the filter element reaches 35±12 kPa.
- Electromagnetic valve (servo-operated valve): Opened when energized, max. current consumption 1.5 A, current consumption 0.3-0.50 mA, modulation 250 Hz, 500 mV.
- Non-return valve (thermoregulator): Opens when pressure exceeds 10 kPa (35 °C (89.6 °F)).
- Relief valve (servo-operated valve): Opens at pressure amounting to 20 kPa.
- Slide-valve: Adjustment at 100±10 kPa.
- Fuel pump (P/N 490720.01): Single stage, gear-type, 63 µm filter, delivered quantity 130±5 l/hour (depending on operation mode), pressure 1.3±0.1 MPa.
- Fuel-oil exchanger: Tubular.
- Fuel nozzle: Bypass (with fuel bypassing), 12 nozzles.
- Fuel ramp drainage valve: DV-1, 15±10 kPa.
- Combustion chamber drainage valve: DV-2, 36±8 kPa.
- Return fuel filter (LUN 7616-8): Filter efficiency 12 µm, bypass set to 30±5 kPa.
Oil System:
- Description: Autonomous, directly deaeration with open circulation.
- Flow rate: 60 l/hour.
- Oil pressure: 210 kPa max.
- Minimum oil pressure: 88±5 kPa.
- Operating oil temperature: -40 to +140 °C.
- Oil tank (P/N 490620.03): Total volume 2.1 l, "MAX" level mark volume 2.1 l, "MIN" level mark volume 0.8 l.
- Level indicator: Glass pipe.
- Relief valve: Opens at pressure amounting to 40±5-10 kPa.
- Filler neck with quick-closing valve and screen: Filter efficiency 200 µm.
- Fuel-oil exchanger: Tubular.
- Output filter: Filter efficiency 80 µm.
- Oil pump (LUN 6320-8): Single stage, gear-type, from APU gear, 1:7 drive.
- Oil filter (P/N 490131.01): Filter efficiency 35 µm, differential pressure indicator LUN 1491.22 (switches on when filter element losses reach 40±5 kPa, opens when pressure losses in the filter element reach 55±5 kPa).
- Pressure switch of oil filter (LUN 6731-8): Switches on when pressure decreases to 80±5 kPa.
- Electromagnetic valve (P/N 486611.01): Opens when energized, current consumption with voltage 27±1 VDC < 1.5 A.
- Electromagnetic fuel valve (LUN 2475-8): Opens when under voltage (alive) < 1.5A.
Air System:
- Characteristic: Output.
- Air parameters behind anti-stall bleed valve at 100% speed mode (for ISA, H=0m): ≥1920 kg.h⁻¹, ≥248 kPa.
- Air pressure: 190 °C (374 °F).
- Warning of the air in the compressor: -60 °C to +60 °C.
- Venturi tube: Ø 33 mm, APU protection (part of the anti-stall bleed valve, restricting the air quantity from the compressor and protect turbine overheating).
- Anti-surge valve (P/N 490330.03): Closing initiation at the Venturi tube over-pressure of 55±5 kPa, opening initiation at the Venturi tube over-pressure of 70±5 kPa.
- Visor in the output throat of the anti-stall bleed valve: Ø 27 mm.
Control and Regulation System:
- Speed transmitter (LUN 1326.03-8): Electronic, produces input signal for electronic control, electromagnetic type, 1 V on 2145 Hz ± 5%, on the APU gearbox, 36 holes, 11,668 rpm/Hz conversion ratio.
- Temperature Transmitter (LUN 1371.01-8): Produces input signal for electronic control, Thermocouple CHROMEL-ALUMEL, 3 transmitters.
- Control box (LUN 3594.04): Controls APU speed, electric accessories, and APU closing. Digital type with preset modes: full operating speed 100% (51,900 rpm), idling speed 89% (46,400 rpm), maximum speed 109% (56,660 rpm), sub-speed 79% (41,200 rpm).
- APU protections:
- Closing during actuation if exhaust gas temperature does not reach 150 °C (302 °F) within 13 sec.
- Closing of APU during actuation if sub-speed (70%) is not reached within 35 sec.
- High temperature of exhaust gases signalized when temperature reaches 850±15 °C (1562±59 °F).
- If set exhaust gas temperature is exceeded, control box decreases turbine speed until set temperature is reached (800±15 °C (1472±59 °F)).
- Signaling on control panel (not causing APU closing): Rotation speed 89%, rotation speed 100%, high gas temperature, clogging of oil filter, clogging of fuel filter.
Actuating System:
- Ignition exciter (P/N 81550.01): High-energy type, 28 V nominal voltage, 2.5-3 kV output voltage, 1 output.
- Ignition plug (P/N 85500.11): 1 plug.
- Interconnecting conductor (length 1100mm): P/N 490510.01.
- Electric-starter (P/N 490110.01): 1.25 kW output on 4600 rpm, 26 V maximum terminal voltage, 28,000 rpm maximum speed, 1:1.96 change-over ratio, centrifugal clutch, 10±0.5 Nm slip moment.
Permissible Overload with APU Switched Off:
- Maximum operational multiples in the APU gravity center and limiting values of angles and angular speeds for the three axes of airplane are:
- Linear overload: nx = ±5 g, ny = +11 ÷ -4 g, nz = ±3 g.
- Angular acceleration: εy = 4.5 rad/sec², εx = 25 rad/sec², εz = 15 rad/sec².
- APU is resistant to the effect of negative linear overload lasting for 15 sec with 30 sec. pauses.
Fluids in Use:
- Fuel: See article 1.1.
- Oil: See article 1.1.
- It is prohibited to mix oils!
APU Actuation in Flight:
- Scope of airplane instrument speed for reliable APU actuation: 214 ÷ 321 KIAS (400 – 600 km/hour).
- Common maximum flight speed for successful APU start: Max. 26,500 ft (8,000 m).
Other Limits:
- Fuel pressure on input of the APU Fuel System: 80 – 186 kPa.
- Fuel pressure on output from the APU Fuel System at the idle of APU: 10-25 kPa.
- Max. fuel viscosity: 12 mm²/sec.
- Pressure of gasses behind the turbine (in the spout): Max. 5 kPa.
- Negative air pressure in the APU suction area: Max. 1.5 kPa.
- Min. total input opening surface for the air flow into the APU installation: Min. 300 cm².
- Maximal permitted time of signaling light of high exhaust gas temperature in the mode of APU start and engine: 5 s.
- Inside diameter of air pipes: Min 48 mm.
- Possibility of using different operational liquids must be agreed with original producer of APU.
- Maximal exhaust gas temperature: 850 °C.
- Nominal net voltage: 28 VDC.
- Precondition of successful APU start: Supply conductors of electric starter have the adequate diameter and resistance (depending on the length), which must be chosen so that during start the voltage on the battery terminals could not decrease under 14 VDC.
- Total resistance of both lines between battery and electric starter must be in range: 23±2 mΩ.
- Voltage on the electric starter terminals must not at the time the APU start and during his run owing to the overall resistance of power cables and the internal resistance of the battery less than: 26 VDC.
- Minimum duration deceleration – time to stop the rotor APU from APU shutdown from idle speed must be at least: 45 sec.
- After installing the APU 5SL unit on the aircraft and after grounding conductors connecting, must be the resistance between grounding screw on the mounting flange of the control box and the grounding screw on APU turbine casing flange: Max. 0.5 Ω.
- After the shutdown of APU from idle or 100% speed and immediately after stopping the rotor must go rotate by the rotor freely!
Usage Features
The manual outlines detailed procedures for pre-start preparation, APU actuation, engine actuation, cold turn, and shutdown.
- Pre-Start Preparation: Involves checking oil level, fuel system circuit breakers, fuel pump, and other related works.
- APU Actuation: Initiated by switching on the power supply and pressing the "START BUTTON," leading to the APU accelerating to 100% speed within 23-35 seconds.
- Engine Actuation: The APU's starting cycle for the main engines begins immediately after reaching the APU operating rotation speed (100%) by opening the air valve of the starter turbine.
- APU Cold Turn: Performed without ignition for dewaxing, activation, or preservation. The method involves a 13-second operation without ignition.
- APU Shutdown: Standard shutdown involves switching off the "DELAY / STOP" switch, which decreases rotational speed to idle for two minutes to cool the turbine, then disconnects power and shuts down the APU. Emergency shutdown is initiated by the "EMERGENCY STOP" switch for immediate APU shutdown.
- Monitoring and Signaling Equipment: The APU control panel in the cockpit displays signals for APU operation (89% and 100% speed), high gas temperature, and clogging of oil/fuel filters.
Maintenance Features
The manual provides extensive instructions for maintenance, including periodic checks, inspections, and preservation.
List of Changes and Corrections:
- The manual includes a list of changes, such as updates to control box parameters based on APU requirements.
Periodic Checks:
- After 50-100 hours of APU operation: Involves checking the oil tank, oil pump, oil filter, ignition plug, and interconnecting conductor.
- After 100-200 hours of APU operation: Includes checking the APU, block of filter and servo, return fuel filter, and oil tank.
- After 150-300 hours of APU operation: Involves checking the ignition plug and electromagnetic valve.
- After 300 hours of APU actuations or 50-100 hours of APU operation: Includes checking the APU, block of filter and servo, return fuel filter, oil tank, ignition plug, and interconnecting conductor.
- After 650 hours of APU actuations or 100-200 hours of APU operation: Same as above, but for the next interval.
- After 1000 hours of APU actuations or 150-300 hours of APU operation: Same as above, but for the next interval.
Specific Maintenance Tasks:
- Inspection of the Oil Filter (4.8.6): Involves removing, cleaning (with petrol and compressed air, or ultrasonic washer), lubricating packing rings, and reassembling. Warning against soiling during handling.
- Cleaning of the Oil Tank and Renewal of Filling (4.8.7): Procedure for removing soil from the oil loop, including dismounting plugs, draining oil, cleaning screens, inspecting for magnetic foreign matter, rinsing with aviation petroleum, and refilling with clean oil.
- Ignition System Inspection (4.8.8):
- Ignition Plug: Checking for wear and tear (cracks, mechanical damage, points wear > Y=2mm, Z=8mm), replacing if unsatisfactory. No cleaning of the insulator surface is allowed. Replacement is required after 1000 starts or 150 hours of operation.
- Interconnecting Conductor: Checking for mechanical damage, wire strand disconnection, insulation damage, and rubber packing ring condition. Electrical continuity check with an ohmmeter.
- Ignition exciter: No maintenance required.
- Flushing of the Oil Pump Relief Valve (4.8.9): Detailed procedure for dismounting, cleaning, and reassembling the relief valve, ensuring proper oil pressure delivery.
- Check of the Electromagnetic Valve 486611.01 (4.8.10): Includes insulation resistance check, switching voltage check, and leak-tightness check.
- Check of the Speed Transmitter Slot (4.8.11): Involves removing, cleaning, checking dimensions, and reassembling with new packing rings if necessary.
- Check of the Overrunning Clutch, Brushes and Commutator of the Electric Starter (4.8.12): Disconnecting conductors, dismounting, checking components for wear, cleaning, and reassembling.
Dewaxing and Preservation:
- On Delivery from the Manufacturer (5.1): Unpacking, verifying identity, washing external surfaces, flushing fuel system, installing APU, and performing activation work.
- After 3 Months Preservation (5.2): Draining preservative liquid, flushing fuel system (2 APU starts without ignition), and cleaning filter elements.
- Preservation Valid for 30 Days (5.4): Running APU in Idling Mode for 2 minutes at least once a month.
- Internal Preservation Valid for 3 Months (5.5): Supplying preservative oil under pressure to the fuel system, filling oil tank, and performing a cold start (13 sec without ignition).
- Preservation Valid for 1 Year (5.6): Dismounting APU, internal preservation, coating corrosion-prone parts, packing with dehumidifier, and storing in a dry room. Fuel-oil system devices remain filled with operating oil.
- Preservation and Packing for Shipping (5.7): Performing preservation and packing similar to internal preservation, ensuring devices are not damaged during transfer. Draining oil from the oil tank before packing.
Troubleshooting (Chapter 6):
- Provides algorithms for diagnosing and resolving common APU malfunctions, such as failure to start, running for short durations, failure to accelerate, high exhaust gas temperature, excessive oiling, and rotor overspeeding. These algorithms involve checking error messages from the Control Box (EC) via PC interface, inspecting electrical feeding, checking components like the speed transmitter, ignition system, fuel pump, and various valves.
Overall, the SAFIR 5L APU is a sophisticated rotary machine with comprehensive operational and maintenance requirements, detailed in this manual to ensure its safe and reliable performance.
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