General - Physics for Aviation

A wing with a very high aspect ratio (in comparison with a low aspect ratio wing) will have

• Increased drag at high angles of attack.

• A low stall speed.

• Poor control qualities at low airspeeds.

The speed of sound in the atmosphere

• Varies according to the frequency of the sound.

• Changes with a change in temperature.

• Changes with a change in pressure.

Which of the following statements is correct?

• When the cyclic pitch control lever is raised, the blade angle of all the rotor blades increases uniformly and they create the lift that allows the helicopter to take off vertically.

• When the collective pitch control lever is raised, the blade angle of all the rotor blades increases uniformly and they create lift that allows the helicopter to take off vertically.

• When the collective pitch control lever is raised, the blade angle of the aft rotor blades decreases uniformly and they create the lift that allows the helicopter to take off vertically.

The temperature to which humid air must be cooled at constant pressure to become saturated is called

• Dewpoint.

• Absolute humidity.

• Relative humidity.

Which of the following is NOT considered a method of heat transfer?

• Convection

• Conduction

• Diffusion

Answer explanation

Heat can be transferred from a body having a high level of heat energy to a body having a lower level of heat energy by three methods: conduction (actual physical contact), convection (transfer through vertical currents), and radiation (transfer by electromagnetic waves). Diffusion is not a method of heat transfer.

The purpose of aircraft wind dihedral is to

• Increase lateral stability.

• Increase longitudinal stability.

• Increase lift coefficient of the wing.

Answer explanation

Dihedral or the upward slant of the wing from the fuselage is used to increase the lateral stability. Lateral stability is roll stability and is stability about the longitudinal axis.

Which atmospheric conditions will cause the true landing speed of an aircraft to be the greatest?

• Low temperature with low humidity.

• High temperature with high humidity.

• High temperature with high humidity.

Answer explanation

The true landing speed of an aircraft is determined by the density of the air. The amount of aerodynamic lift produced by the wing of an airplane or the rotor of a helicopter is determined by several things. Among these are the shape of the airfoil, the speed of the airfoil through the air, and the density of the air. The denser the air, the lower the speed that will produce the same amount of lift. Density of the air depends upon both its temperature and its humidity. The hotter the air, the less dense. The more water vapor in the air (the higher its humidity), the less dense the air. An airplane will have to fly the fastest to produce the required lift under conditions of high temperature and high humidity.

Which will weigh the least?

• 98 parts of dry air and 2 parts of water vapor.

• 35 parts of dry air and 65 parts of water vapor.

• 50 parts of dry air and 50 parts of water vapor.

An airplane wing is designed to produce lift resulting from

• Positive air pressure below and above the wing's surface along with a downward deflection of the air.

• Positive air pressure below the wing's surface and negative air pressure above the wing's surface along with the downward deflection of air.

• Negative air pressure below the wing's surface and positive air pressure above the wing's surface along with the downward deflection of air.

An engine that weighs 350 pounds is removed from an aircraft by means of a mobile hoist. The engine is raised 3 feet above its attachment mount, and the entire assembly is then moved forward 12 feet. A constant force of 70 pounds is required to move the loaded hoist. What is the total work input required to move the hoist?

• 840 foot-pounds

• 1,890 foot-pounds

• 1,050 foot-pounds

Answer explanation

More information is given with this problem than needed; therefore, it can cause confusion. The only work asked for is the amound needed to move the hoist. The hoist is moved for a distance of 12 feet and a constant force of 70 pounds is needed to move it. The work done to move the hoist is 12 x 70 = 840 foot-pounds.