# Aerodynamics Set 2 – Examination

On what instance does negative pressure coefficient occurs?
a. When dynamic pressure is twice the pressure difference
b. When the freestream velocity is higher than local velocity
c. When local velocity is higher than freestream velocity

Answer: c. When local velocity is higher than freestream velocity

1. Translational thrust occurs when…
a. the main rotor becomes less aerodynamically efficient during the transition from hover to forward flight.
b. the tail rotor becomes more aerodynamically efficient during the transition from hover to forward flight.

Answer: b. the tail rotor becomes more aerodynamically efficient during the transition from hover to forward flight.

What is translational lift in helicopters?
Answer: Lift from HOVER TO FLIGHT
Translational lift: The additional lift produced by a helicopter rotor as the helicopter changes from hovering to forward flight. The lift produced by a helicopter rotor decreases as the helicopter rises vertically out of ground effect.

1. In small airplanes, normal recovery from spins may become difficult if the
a. CG is too far rearward, and rotation is around the CG
b. CG is too far rearward, and rotation is around the longitudinal axis
c. A stall is entered before the spin developed
d. Spin is entered before the stall is fully developed

Answer: a. CG is too far rearward, and rotation is around the CG

At “Normal Recovery” – (last portion ng spin) AC is naka nose down to recover.

1. In Prandtl-Glauert transformation, what happens to the shock waves that occur at supersonic speeds?
a. They become weaker
b. They become stronger
c. They become weaker
d. They vanish

The Prandtl-Glauert transformation can be used to study supersonic flow at subsonic speeds by transforming the flow to a subsonic flow. The Prandtl-Glauert transformation is a mathematical technique used to simplify the equations of compressible flow. One of the effects of the transformation is to make shock waves disappear.

1. The greatest stress on a rotating propeller occurs
a. at about 75% of the length
b. at the root
c. at the tip
d. at about 75% of the length

1. Which part of the airplane provides the greatest positive contribution to the static longitudinal stability?
a. Horizontal stabilizer
b. The engine
c. The fuselage
d. The engine

The most desirable type of stability for an aircraft to possess is
a. Neutral static stability
b. Neutral dynamic stability
c. Positive static stability
d. Positive dynamic stability

• RAYMER
1. _ are most commonly found on high-speed military combat aircraft where they are used to enhance maneuverability and to eliminate the Mach tuck caused by shock wave formation behind the elevator hinge line of a conventional tail.
a. v-tail design
b. stabilator
c. canard

1. Hazardous vortex turbulence that might be encountered behind large aircraft is created only when the aircraft is __
a. Operating at high airspeed
b. Using high power settings
c. Producing lift

What determines the longitudinal stability of an airplane?
a. The location of the CG with respect to the center of lift.
b. The location of the CG with respect to the center of pressure.

Answer: a. The location of the CG with respect to the center of lift.

CG to CL

Experiments done with this type of boundary layer control produced very high lift coefficients.
a. both a and b
b. boundary layer blowing
c. boundary layer suction
d. jet flap

This stabilizer design tends to produce trim problems associated with the transition from low-speed flight into hover, where the main rotor wake may suddenly move forward over the empennage location and so produce a nose down pitching moment on the aircraft.
a. Forward mounted
b. Aft mounted
c. Conventional Tail
d. T-tail Design

From “AFT” to forward air

Helicopter sideward flight can be a very unstable condition due to
a. the induced drag combined with the lack of horizontal stabilizer for that direction of flight.
b. the induced drag combined with the lack of vertical stabilizer for that direction of flight.
c. the parasitic drag of the fuselage combined with the lack of vertical stabilizer for that direction of flight.
d. the parasitic drag of the fuselage combined with the lack of horizontal stabilizer for that direction of flight.

Answer: d. Di for “side of fuselage”

1. Why is it necessary to increase back elevator pressure to maintain altitude during a turn? To compensate for the
a. Rudder deflection and slight aileron throughout the turn
b. Loss of horizontal component of lift and the increase in centrifugal force
c. Increase in vertical component of lift and loss in horizontal component of lift
d. Loss of vertical component of lift

Answer: d. Loss of V lift

At what altitude does the pressure in the Standard Atmosphere reach 50% of its sea level value?
a. 18,000 feet
b. 5,000 feet
c. 10,000 feet
d. 20,000 feet

36 000 ft troposphere max ÷ 2 = 18 000 ft

Which of the following is a glider?
a. Zeppelin
b. F/A – 18
c. DG 1001
d. Zenith S-5

Answer: F/A – 18 (Foam glider toy)

It is a short winglike control surface projecting from the fuselage of an aircraft.
a. V-TAIL DESIGN
b. STABILATOR
c. T-TAIL DESIGN
d. CANARD

Stabilator is tail pa rin

Incorporating _ eliminates the need for a drying mechanism.
a. liner walls
b. driers
c. single liners
d. return circuits

Answer: d. return circuits (like wind tunnel)

An aircraft is flying at a constant power setting and constant indicated altitude. If the outside air temperature (OAT) increases, true airspeed will
a. Increase and the true altitude will increase
b. Decrease and the true altitude will increase
c. Increase and the true altitude will decrease
d. Remain the same and the true altitude will decrease

Answer: a. Increase and the true altitude will increase

Kasi need mag climb ng AC. When the outside air temperature (OAT) increases, the density of the air decreases.