M14.3 - Starting and Ignition
0.0 / 5
- Created by: Bikboi
- Created on: 03-10-24 12:48
What 2 systems are required for a gas turbine engine to start?
Compressor and turbine to be rotated at speed where air flow is adequate and ignition
1 of 158
What part of the engine is rotated to start?
HPC
2 of 158
Why must the torque applied during starting be higher than necessary?
Overcome inertia and friction loads
3 of 158
Why does the starter continue after self sustained speed is achieved?
Prevent hot or hung false start
4 of 158
What is the preferred modern way of starting?
Electric or air starter
5 of 158
Why are cartridge starters used?
Quick and independent
6 of 158
What is used to supply power for cartridge starters?
Cordite charge
7 of 158
How power produced within a cartridge starter?
Overboard exhaust collector
8 of 158
What happens in a cartridge starter if pressure exceeds the maximum value?
Relief valve sends gas to turbine bypassing hot gas nozzles
9 of 158
Where are air starters usually used?
Commercial jet engines
10 of 158
How is power transmitted within an air starter?
Reduction gear and clutch
11 of 158
What is the minimum air pressure required to complete a start?
30 psi
12 of 158
How is air directed onto the rotor of an air starter?
Nozzle vanes
13 of 158
How is air supply to the starter removed when reaching the cutout speed?
Rotor switch actuator interrupts electrical signal to start valve
14 of 158
How is turbine overspeed rotor failure accommodated in air starters?
Turbine housing rotor containment ring sends fragments at low energy through the exhaust duct
15 of 158
The starter oil does not circulate through the engine?
True
16 of 158
How is oil added to the air starter?
Through a port that is closed by a vent plug that allows the sump to vent during flight
17 of 158
How is removal and installation of air starter facilitated?
Mounting adapter
18 of 158
What are the subassemblies contained within the PRSOV of the air starter?
Pressure regulating valve and regulating valve control
19 of 158
What does the servo piston actuated cam arrangement serve to the starter?
Small initial travel and high initial torque
20 of 158
What does the overrunning type of clutch facilitate for the air starter?
Positive engagement and minimises chatter
21 of 158
How is the inboard clutch gear disengaged as the engine speeds up?
Return spring
22 of 158
What are the 2 types of electric starter?
Direct cranking and starter-generator
23 of 158
What type of motor is usually used within electric starters?
DC
24 of 158
What is used to allow voltages to be progressively built up as the starter gains speed?
Relays and resistances
25 of 158
What else is supplied by the electric starter power supply?
Ignition power
26 of 158
When is the power for an electric starter removed?
When starter load is reduced or timecycle completes
27 of 158
Where are electric starters usually found?
APU or small turboshaft engines
28 of 158
How does a starter generator supply power?
Second series of winding allow it to switch into a generator after engine is self sustaining
29 of 158
What does the compensating and interpole (commutating) windings provide the starter-generator?
Sparkless commutating from no load to full load
30 of 158
Which windings are used when the starter generator is starting?
Series, Compensating and Interpole (Commutating)
31 of 158
Which windings are used when the starter generator is generating?
Shunt, Compensating and Interpole (Commutating)
32 of 158
What is the peak voltage and current required by a starter generator?
24V and 1500A
33 of 158
What are the 2 relays contained within the starter generator control block?
Motor relays and undercurrent relay
34 of 158
If the system is equipped with an undercurrent relay, what must be completed to complete the circuit?
Closing master switch
35 of 158
What is the motor relay of the starter-generator for?
Starter input controlled by undercurrent relay
36 of 158
What 3 relays close when the battery and start switch are both turned on?
Motor, Ignition and battery cutout
37 of 158
Why is the starter battery cutout relay closed during starting?
Starter would drain battery power
38 of 158
What scenario must occur in a starter generator before the start sequence completes?
Current draw less than 200A, undercurrent relay opens
39 of 158
If the starter generator fails to accelerate the engine to sufficient speed, how is it disengaged?
Stop switch
40 of 158
When is continuous ignition used?
Possibility of flame out and to relight the fuel
41 of 158
What conditions are continuous ignition usually used in?
Take off, landing and abnormal/emergency situation like hailstorm or volcanic cloud
42 of 158
How are ignition systems usually cooled?
Fan air flow
43 of 158
Why is a high intensity high heat spark required?
Low temperatures found at high altitudes
44 of 158
What types of leads are typically found in ignition systems?
Intermediate and high tension leads
45 of 158
How is noisy voltage prevented in ignition systems?
Filter
46 of 158
What types of cam are found within ignition systems?
Multilobe (breaker points actuated by this) and single lobe
47 of 158
What is the maximum charge of the ignition capacitor?
4 Joules
48 of 158
How many joules per second equal 1 watt?
1
49 of 158
How is the capacitor within the ignition system charged?
Rapidly interrupted current over auto transformer
50 of 158
How does the spark rate of the igniter vary?
In proportion to the voltage of the DC power supplies as it changes motor RPM
51 of 158
How is the discharge time of the capacitor minimised?
High frequency triggering transformer and low reactance secondary windings
52 of 158
What is caused by having the discharge time of the ignition capacitor being as small as possible?
Maximum energy to blast carbon deposits and vaporise globules of fuel
53 of 158
What purpose does hermetically sealing the ignition exciter serve?
Shields leakage of high frequency voltage that interferes with radio and prevents flashover at altitude from pressure changes
54 of 158
How many storage capacitors are withing a discharge exciter unit?
2
55 of 158
How is electrode erosion minimised?
Short operation times
56 of 158
Why is the electrode gap of an igniter plug about to be larger than a conventional spark plug?
Lower operating pressures
57 of 158
What does an angular gap (long reach) igniter plug do?
Projects slights into combustion liner to produce effective spark
58 of 158
What does a constrained gap igniter plug do?
Operates at much cooler temperatures are spark arcs beyond face of chamber liner
59 of 158
How long after engine shutdown should you wait before touching ignition components?
20 minutes
60 of 158
How is the ignition system operationally tested?
Listening on engine start or removing and activating start cycle to see visible spark
61 of 158
Where should igniter plug coupling nuts be disconnected when carrying out maintenance?
Ignition exciter end first
62 of 158
What type of tools must be used when disconnecting igniter plug coupling nuts and other igniter components?
Insulated tools
63 of 158
How did old reciprocating engines used to be started?
Pulling the propeller
64 of 158
Why does pulling the propeller to start struggled in cold weather?
Oil temperatures near congealing point and magnetos offer weak starting spark at low speed
65 of 158
What is NOT used to compensating for cold weather starting problems of reciprocating engines?
Hand warmers
66 of 158
What are the 3 types of inertia starters?
Hand, electric and hand/electric
67 of 158
How is the starter engaged into crank shaft after flywheel has stored enough kinetic energy?
Cable or meshing solenoid
68 of 158
How is energy transferred from starter flywheel to engine?
Reduction gears and torque overload release clutch
69 of 158
What is the most widely used type of electric starter?
Direct cranking
70 of 158
What types of cables are used from starter to the battery on reciprocating engines?
Heavy duty due to high current flow (100-350A)
71 of 158
Within direct cranking electric starters, what is used to reduce weight and circuit voltage drop?
Solenoids and heavy wiring with remote control switch
72 of 158
What is the advantage of the 12 or 24V series wound motors in direct cranking electric starters?
High starting torque
73 of 158
What are the 2 segments of direct cranking for large reciprocating engines?
Motor and gear
74 of 158
How does the speed of direct cranking starters for large reciprocating engines vary with load?
Inversely
75 of 158
What is the travelling nut and jaw full travel?
5/16" in approximately 12° of rotation
76 of 158
How is damage to engine and starter prevented by the clutch pack?
Pack plate slips when engine torque exceeds clutch slipping torque
77 of 158
Where is the current from reciprocating engine starting taken?
Master bus
78 of 158
After energised for 1 minute, how long should the starter be left to cool?
1 minute
79 of 158
After a second or subsequent cranking period of 1 minute of a reciprocating engine, how long should the starter be left to cool?
5 minutes
80 of 158
Where does the knob/handle on the instrument panel connect for the starter on small aircraft?
Connects to starter via flexible control to engage motor to crankshaft
81 of 158
How is the starter solenoid activated on direct cranking starting small aircraft?
Push button or ignition key on instrument panel
82 of 158
How does the clutch spring transfer torque between starter and crank shaft?
Clutch spring tightens up around starter shaft gear and transfers to crank shaft gear
83 of 158
How can a starter be mounted to a propeller aircraft?
Mounted to ring gear on propeller hub and drives gear into propeller hub to spin propeller
84 of 158
What are the 2 types of piston engine ignition systems?
Magneto (single or dual) or electronic FADEC
85 of 158
How does a single magneto differ from a dual magneto?
Single magneto has 1 magneto and wiring with another of the same system on the same engine, dual has 2 magnetos within housing
86 of 158
What are the 2 types of magneto system?
High or low tension
87 of 158
Why is magneto timing important?
Synchronised so that the spark (field collapsing) occurs at the right stroke (just before TDC)
88 of 158
How many separate circuits are found within a high tension magneto system?
Magnetic, primary and secondary
89 of 158
What is the full register position of the magnetic circuit?
Maximum number of magnetic lines of force
90 of 158
How much flux flows through the core at the neutral position?
None
91 of 158
When does the polarity of a magnetic circuit change?
90° from full register position
92 of 158
How is arcing prevented when the circuit is opened and also to hasten magnetic field collapse?
Capacitor
93 of 158
What is Lenz's law?
An induced current always flows so that its magnetism opposes the motion or the change that induced it.
94 of 158
What does the current in the primary circuit do?
Holds flux in core at a high value until magnet has time to rotate past neutral
95 of 158
What is the E gap position?
A point just beyond neutral that opens the breaker and reverses the field, producing high voltage electricity in secondary to generate spark
96 of 158
How many discharges occur when the plug sparks?
1 peak discharge and a series of small oscillations
97 of 158
What material is the contact point made from?
An alloy that prevents pitting and burning
98 of 158
What is the most common type of breaker point?
Pivotless (1 moving and 1 stationary)
99 of 158
What materials are the cam follower usually made from?
Micarta block or similar
100 of 158
How is librication and corrosion prevention of the cam achieved?
Felt oiler pad on metal spring leaf
101 of 158
How is quick and easy checking/adjustment of the breaker points achieved?
Step cut across the cam to show e-gap position
102 of 158
How is the strength of the voltage induced changed if all other factors remain constant?
Number of turns of the wire
103 of 158
What can voltages reach in the secondary electrical circuit of the magneto?
20,000V
104 of 158
What are the 2 parts of the distributor, and which are stationary/revolving?
Revolving is the rotor and the stationary is the block
105 of 158
How quickly does the distributor rotate?
1/2 speed of crankshaft
106 of 158
What does the distributor number represent regarding the magneto?
Magneto sparking order
107 of 158
What are the 2 ways to complete the primary circuit?
Closed breaker points to ground or closed ignition switch to ground
108 of 158
When the ignition switch is OFF, how do the magnetos function?
Magnetos are inoperative as permanent ground is available and voltage is too low to fire spark plug
109 of 158
What is the dual purpose of the ignition/starter switch?
Controls magnetos and starter solenoid
110 of 158
If a starting ******** is used (To emit pulsating DC), what does the ignition/start switch control?
******** and ****** points
111 of 158
What is sometimes available to spray fuel into intake port during starting cycle?
Push to prime
112 of 158
What does the elongated slot on the mounting flange at the rotating shaft of magneto allow?
Adjustment to aid in timing the magneto to the engine
113 of 158
What types of aircraft engines use base mounted magnetos?
Old or antique
114 of 158
How does a low tension magneto system differ from high tension?
Low voltage goes to transformer near the spark plug so very short high tension leads are needed
115 of 158
How is flashover eliminated in low tension magneto system?
Brush type distributors
116 of 158
Why are low tension magneto systems only used in limited situations in modern aircraft?
Excellent materials for high tension leads and added cost of a coil for each spark plug
117 of 158
Why were low tension magneto systems developed?
To help with voltage leaking out at high altitude and disrupting systems
118 of 158
What is the single moving part of a piston engine FADEC system?
Opening/closing of fuel injector
119 of 158
How does the low voltage harness transmit inputs to the ECU?
Via 50 pin connector
120 of 158
How many cylinders does each ECU control?
2
121 of 158
Why is EGT measured after each burn?
Verify fuel quantities are correct
122 of 158
What is used in case of both sensors of a redundant pair for the ECU failure?
Synthetic defaults
123 of 158
How can engine ignition timing be adjusted in a powerlink system?
Engine ignition timing cannot be adjusted in a powerlink system as it is established by the ECU.
124 of 158
During starting, what magnetos are connected to auxiliary ignition units?
Left
125 of 158
Where is the auxiliary electrode located within a booster coil?
Trails main electrode to ****** spark during starting
126 of 158
What does the impulse coupling do?
Gives the left magneto a brief acceleration to produce intense spark
127 of 158
What are the 2 functions of an impulse coupling?
Rotating magneto fast enough for intense spark and retarding timing of the spark during start cycle
128 of 158
How does the impulse coupling disengage?
Centrifugal forces push the flyweights away so it no long engages with the stop pin
129 of 158
How can you tell if an engine has impulse couplings fitted?
Sharp clicking noise at start speed past TDC
130 of 158
How are high tension ****** breaker vibrators contained?
Metal case
131 of 158
What does the high tension ****** breaker ******** do?
Changes DC from battery to pulsating DC for primary coil of magneto
132 of 158
What is produced across spark plug gap by high tension ****** breaker ********?
Shower of sparks produced via rapid successions of separate voltages induced
133 of 158
What does the high tension ****** breaker ******** eliminate the need for in light aircraft?
Impulse coupling
134 of 158
When the starter switch of the high tension ****** breaker ******** is ON, what is true regarding the magnetos?
Right magneto is off
135 of 158
At 2100 rpm, how many sparks are produced per second?
17
136 of 158
What is the temperature and voltage over the electrodes of a piston engine spark plug?
3000°F and 20,000V
137 of 158
What are the 3 main parts of piston engine spark plugs?
Electrode, insulator and outer shell
138 of 158
Why are insulators made from aluminum oxide ceramics?
Excellent dielectric strength, high strength and thermal conductivity
139 of 158
What is the main differences in electrode material?
Cost and length of service
140 of 158
What is true regarding iridium and platinum?
Very high melting points and considered precious metals but a long service life with increased performance when compared to massive electrode plugs
141 of 158
What is the heat range of a piston engine spark plug?
Measure of ability to transfer heat of combustion to cylinder head
142 of 158
What is a pre-ignition condition?
Glowing red spark plugs that ignite fuel too early
143 of 158
What are hot spark plugs?
Long insulator nose to create long heat transfer path
144 of 158
What are cold spark plugs?
Short insulator to provide rapid transfer of heat
145 of 158
What is not considered when selecting different types of spark plugs?
Aircraft displacement
146 of 158
What type of plug is likely to be used for a higher compression ratio engine?
Colder
147 of 158
What is the spark plug reach?
Length of threaded portion that is inserted in spark plug bushing
148 of 158
What can occur if the spark plug reach is too long?
Plug may contact the piston/valves and damage can occur
149 of 158
What can occur if the spark plug reach is too short?
Threads can extend into cylinder and get carbon deposits which are hard to remove
150 of 158
Is it acceptable to be airborne with the knowledge that only 1 magneto system is serviceable?
No
151 of 158
When is the magneto drop test required?
On every before takeoff checklist
152 of 158
What is a magneto drop test?
When the engine is run up and ensure each magneto disconnects when grounded.
153 of 158
What must be checked regarding the RPM during a magneto drop test?
RPM drop between magnetos must be in limits
154 of 158
What is the voltage of the piston engine HT system?
Over 10,000 volts and can exceed 25,000 volts
155 of 158
What must be ensured before working on piston engine HT system?
Ensure fuel and ignition switch is set to off.
156 of 158
What is an additional HT system safety consideration sometimes required in regards to the spark plugs?
One of the spark plugs must be removed from each cylinder to prevent compression
157 of 158
What is an additional HT system safety consideration that is sometimes required in regards to the magnetos?
Distributor cap may need to be isolated
158 of 158
Other cards in this set
Card 2
Front
What part of the engine is rotated to start?
Back
HPC
Card 3
Front
Why must the torque applied during starting be higher than necessary?
Back

Card 4
Front
Why does the starter continue after self sustained speed is achieved?
Back

Card 5
Front
What is the preferred modern way of starting?
Back

Similar Other resources:
0.0 / 5
0.0 / 5
0.0 / 5
0.0 / 5
0.0 / 5
0.0 / 5
0.0 / 5
Comments
No comments have yet been made