Ignition And Electrical Flashcards
If the ignition switch is place in the OFF position but the aircraft engine continues to run, what is the probable cause of the problem?
The “P” lead is not grounded.
During an engine run-up magneto check, what is the range of RPM drop considered to be normal when the mag switch is placed in the LEFT or RIGHT position?
25-75 RPM
A reciprocating engine either fails to start, fails to idle properly, or has low power and runs unevenly. All of these conditions could be caused by what common defective ignition system part(s)?
Defective or improperly gapped spark plugs.
What can be done to verify if a turbine engine igniter is firing?
The igniter can be heard snapping while rotating the engine or the igniter can be removed from the engine and the spark can be observed while activating the start cycle.
What precautions need to be taken when removing an igniter plug from an engine?
The low voltage lead to the exciter box should be disconnected and wait one minute (minimum) before removing the ignition lead from the plug.
What is the purpose of checking the “P” lead for a proper ground?
A grounded “P” lead disables the ignition and the magneto will not fire. An ungrounded “P” lead results in the ignition being “hot” and movement of the propeller could cause the engine to start.
What are two types of spark plug fouling and what causes each?
Carbon fouling – fuel/air mixtures too rich to burn or extremely lean.
Oil fouling – oil past the rings and valve guides into the cylinder.
Lead fouling – when using leaded fuel, lead oxide forms during combustion when cylinder temperature is low.
Graphite fouling – excessive application of anti-seize compound on spark plug threads.
What are the components in the primary electrical circuit of a magneto?
The breaker contact points, a condenser, and an insulated coil.
What is “E” gap?
The rotational position of a permanent magnet a few degrees past the neutral position where the breaker points are opened.
How is the p-lead circuit related to the production of a spark in a magneto?
Current is induced in the p-lead circuit by a rotating magnet. This creates a magnetic field. When the breaker points open the p-lead circuit, the field collapses across the secondary coil windings. This produces a high-voltage current that is directed to the spark plug to jump the electrode gap.
What is the difference between a low-tension and a high-tension ignition system?
The low-tension ignition system creates a low-voltage that is distributed to a transformer coil near each spark plug where it is changed to high voltage to fire the plug. A high-tension ignition system uses a secondary coil inside the magneto to create the high voltage which is distributed to every spark plug.
What is the procedure for locating the correct electrical cable/wire size needed to fabricate a
replacement cable/wire?
Wire size considerations take into account allowable power loss, permissible voltage drop, and the current carrying capability of the conductor. Allowance must also be made for the influence of external heating on the wire. Replacement wire can be the same wire as the original wire. Wire can be measured with a wire gauge. It can also be found by consulting a table produced by the American Wire Gauge if the circuit load information is known. Additionally, wires often contain identification markings. Consulting the manufacturer’s data can reveal exactly which wire is required by deciphering the markings which are typically coded.
What are some installation practices for wires running close to exhaust stacks or heating ducts?
If possible, wires should be kept separate from high-temperature equipment. When wires must be run through hot areas, the wires must be insulated with high-temperature rated material such as asbestos, fiberglass or Teflon®. Running coaxial cables through hot area should be avoided. To guard against abrasion, asbestos wires should be in a conduit lined with a high temperature rubber liner or they can be individually enclosed in high temperature plastic tubes before being installed in the conduit.
What procedures must be adhered to when operating electrical system components?
The maximum load from the operation of electrical equipment should not exceed the rated limits of the wiring or protection devices. If loads can exceed the output limits of the alternator or generator, the load should be reduced so that an overload does not occur. If a battery is part of the electrical power system, it should be continuously charged in flight except for momentary intermittent heavy loads such as the operation of a landing gear motor or flaps, etc. Placards should be used to alert flight crews concerning operations that may cause an overload. The total continuous load should be held to 80% of the rated generator or alternator output when
assurance is needed that the battery power source is being charged in flight. When two generators are in use, a specified procedure for quick load-reduction should be employed if, for whatever reason, only one generator is functioning and the load must be reduced to that which the single generator can handle without overload.
