1. What would decrease the stability of an air mass?
   A) Warming from below.
   B) Cooling from below.
   C) Decrease in water vapor.
2. One weather phenomenon which will always occur when flying across a front is a change in the
   A) wind direction.
   B) type of precipitation.
   C) stability of the air mass.
3. What is an advantage of a constant-speed propeller?
   A) Permits the pilot to select and maintain a desired cruising speed.
   B) Permits the pilot to select the blade angle for the most efficient performance.
   C) Provides a smoother operation with stable RPM and eliminates vibrations.
4. The uncontrolled firing of the fuel/air charge in advance of normal spark ignition is known as
   A) combustion.
   B) pre-ignition.
   C) detonation.
5. 5. If a certificated pilot changes his or her permanent mailing address and fails to notify the FAA Airmen Certification Branch of the new address, the pilot is entitled to exercise the privileges of the pilot certificate for a period of only
   A) 30 days after the date of the move.
   B) 60 days after the date of the move.
   C) 90 days after the date of the move.
6. 6. Who is responsible for determining if an aircraft is in condition for safe flight?
   A) A certificated aircraft mechanic.
   B) The pilot in command.
   C) The owner or operator.

Answers:

1. The correct answer is A. Instability is most often found in warm, moist air near the surface. Like a hot air balloon, warm air tends to rise through the cooler air above it. This upward movement air tends to vary in location and strength and can be felt in the form of thermals or bumpy air. Answer B is incorrect because cool air tends to descend. If the cool air is near the surface, the air is more stable. Answer C is incorrect because less water in the air makes it more stable.
2. The correct answer is A. Wind always changes across a front. This is because of the way air circulates around the pressure systems within the air masses that meet to make the front. Answers B and C are incorrect because neither precipitation, nor stability, are always present when crossing a front. The factors most noticeable when crossing a front are changes in temperature, dew point, wind, and pressure.
3. The correct answer is B. A constant speed propeller has movable blades that allow a pilot to select the most efficient performance for a particular operation. High RPM and low blade angle are preferred for takeoff operations because it provides the most horsepower and maximum thrust. Low RPM and high blade angle are preferred for cruise operations because it allows for reduced fuel consumption and engine wear. Answer A is incorrect because a constant RPM is selected, not a constant airspeed. Answer C is incorrect because a constant speed propeller may not be smoother or operate with less vibration than a fixed pitch propeller.
4. The correct answer is B. Pre-ignition means that the fuel/air mixture combusts before it should in normal engine operation (when the spark plug fires). Pre-ignition usually occurs due to a hot spot in the engine cylinder that ignites the fuel/air mixture prematurely, and can result in severe engine damage. Answer A is incorrect because combustion is the term for correct or normal firing of the fuel/air mixture. Answer C is incorrect because detonation is an uncontrolled, explosive ignition of the fuel/air mixture.
5. The correct answer is A. According to FAR 61.60, a pilot has 30 days to notify the FAA Airman Certification Branch after moving to a new permanent address. If they do not, they are not allowed to exercise the privileges of their pilot, flight instructor, or ground instructor certificate until they have notified the FAA in writing. Answers B and C are incorrect because the regulation specifies a limit of 30 days.
6. The correct answer is B. According to FAR 91.7(b), the pilot in command is held responsible for determining that an aircraft is airworthy prior to flight. The PIC is also responsible for discontinuing the flight if a mechanical, electrical, or structural condition occurs that makes the aircraft unairworthy. Answers A and C are incorrect because the regulation specifies that the PIC is responsible. While it is certainly good advice to consult someone more knowledgeable if unsure about something found during the preflight inspection, the PIC is ultimately responsible for the decision.