Operation Of Systems - B: System & Equipment Malfunctions Flashcards
What causes carburetor icing, and what are the first indications of its presence?
The vaporization of fuel, combined with the expansion of air as it passes through the carburetor, causes a sudden cooling of the mixture. The temperature of the air passing through the carburetor may drop as much as 60°F within a fraction of a second. Water vapor is squeezed out by this cooling, and if the temperature in the carburetor reaches 32°F or below, the moisture will be deposited as frost or ice inside the carburetor. For airplanes with a fixed-pitch propeller, the first indication of carburetor icing is loss of RPM. For airplanes with controllable-pitch (constant- speed) propellers, the first indication is usually a drop in manifold pressure.
What method is used to determine that carburetor ice has been eliminated?
When heat is first applied, there will be a drop in RPM in airplanes equipped with a fixed-pitch propeller; there will be a drop in manifold pressure in airplanes equipped with a controllable-pitch propeller. If ice is present there will be a rise in RPM or manifold pressure after the initial drop (often accompanied by intermittent engine roughness); and then, when the carburetor heat is turned “off,” the RPM or manifold pressure will rise to a setting greater than that before application of heat. The engine should run more smoothly after the ice has been removed.
What conditions are favorable for carburetor icing?
Carburetor ice is most likely to occur when temperatures are below 70°F (21°C) and the relative humidity is above 80 percent. However, due to the sudden cooling that takes place in the carburetor, icing can occur even with temperatures as high as 100°F (38°C) and humidity as low as 50 percent. This temperature drop can be as much as 60° to 70°F.
Define the terms anti-icing equipment and deicing equipment and state several examples of each.
Anti-icing equipment—prevents ice from forming on certain protected surfaces. Examples are heated pitot tubes and static ports, carburetor heat, heated fuel vents, propeller blades with electro-thermal boots, and heated windshields. It is normally actuated prior to flight into suspected icing conditions. Reference your AFM/POH.
Deicing equipment—removes ice that has already formed on protected surfaces. It is generally limited to pneumatic boots on the wing and tail leading edges.
Describe how an aircraft deicing system works.
Upon pilot actuation, boots attached to the wing leading edges inflate with air from a pneumatic pump(s) to break off accumulated ice. After a few seconds of inflation, they are deflated back to their normal position with vacuum assistance. The pilot monitors the buildup of ice and cycles the boots as directed in the AFM/POH.
If an airplane has anti-icing and/or deicing equipment installed, can it be flown into icing conditions?
Even though it may appear elaborate and complete, the presence of anti- icing and deicing equipment does not necessarily mean that an airplane is approved for flight in icing conditions. The AFM/POH, placards, and even the manufacturer should be consulted for specific determination of approvals and limitations.
What is detonation?
Detonation is an uncontrolled, explosive ignition of the fuel/air mixture within the cylinder’s combustion chamber.
What are some of the most common operational causes of detonation?
a. Using a lower fuel grade than that specified by the aircraft manufacturer.
b. Operating with extremely high manifold pressures in conjunction with low RPM.
c. Operating the engine at high power settings with an excessively lean mixture.
d. Extended ground operations or steep climbs where cylinder cooling is reduced.
What action should be taken if detonation is suspected?
a. Ensure that the proper grade of fuel is used.
b. Keep the cowl flaps (if available) in the full-open position while on the ground to provide the maximum airflow through the cowling.
c. Use an enriched fuel mixture, as well as a shallow climb angle, to increase cylinder cooling during takeoff and initial climb.
d. Avoid extended, high power, steep climbs.
e. Develop the habit of monitoring the engine instruments to verify proper operation according to procedures established by the manufacturer.
What is preignition?
Preignition occurs when the fuel/air mixture ignites prior to the engine’s normal ignition event resulting in reduced engine power and high operating temperatures.
What action should be taken if preignition is suspected?
a. Reduce power.
b. Reduce the climb rate for better cooling.
c. Enrich the fuel/air mixture.
d. Open cowl flaps if available.
During the before-takeoff runup, you switch the magnetos from the “BOTH” position to the “RIGHT” position and notice there is no RPM drop. What condition does this indicate?
The left P-lead is not grounding, or the engine has been running only on the right magneto because the left magneto has totally failed.
Interpret the following ammeter indications.
a. Ammeter indicates a right deflection (positive).
b. Ammeter indicates a left deflection (negative).
After starting—Power from the battery used for starting is being replenished by the alternator; or, if a full-scale charge is indicated for more than 1 minute, the starter is still engaged and a shutdown is indicated.
During flight—A faulty voltage regulator is causing the alternator to overcharge the battery. Reset the system and if the condition continues, terminate the flight as soon as possible.
After starting—It is normal during start. At other times this indicates the alternator is not functioning or an overload condition exists in the system. The battery is not receiving a charge.
During flight—The alternator is not functioning or an overload exists in the system. The battery is not receiving a charge. Possible causes: the master switch was accidentally shut off, or the alternator circuit breaker tripped.
What action should be taken if the ammeter indicates a continuous discharge while in flight?
a. The alternator should be turned off; pull the circuit breaker (the field circuit will continue to draw power from the battery).
b. All electrical equipment not essential to flight should be turned off (the battery is now the only source of electrical power).
c. The flight should be terminated and a landing made as soon as possible.
What action should be taken if the ammeter indicates a continuous charge while in flight (more than two needle widths)?
If a continuous excessive rate of charge were allowed for any extended period of time, the battery would overheat and evaporate the electrolyte at an excessive rate. A possible explosion of the battery could result. Also, electronic components in the electrical system would be adversely affected by higher than normal voltage. Protection is provided by an overvoltage sensor which will shut the alternator down if an excessive voltage is detected. If this should occur the following should be done:
a. The alternator should be turned off; pull the circuit breaker (the field circuit will continue to draw power from the battery).
b. All electrical equipment not essential to flight should be turned off (the battery is now the only source of electrical power).
c. The flight should be terminated and a landing made as soon as possible.
