Questions Study Unit 1 Subgroup 2
What load factor would be created if positive 15 feet per second gusts were encountered at 120 mph?
2.0 EXPLANATION: Begin at the bottom of Fig. 73 by locating 120 mph and then move up vertically to the positive 15-feet-per-second (+15 fps) diagonal white line. Next, move left horizontally to determine the load factor of 2.0.
If an airplane weighs 3,300 pounds, what approximate weight would the airplane structure be required to support during a 30° banked turn while maintaining altitude?
3,960 pounds. EXPLANATION: Look on the left side of the chart in Fig. 2 to see that, at a 30° bank angle, the load factor is 1.154. Thus, a 3,300-lb. airplane in a 30° bank would require its wings to support 3,808.2 lb. (3,300 lb. × 1.154). The closest answer choice to this value is 3,960 lb.
If an airplane weighs 2,300 pounds, what approximate weight would the airplane structure be required to support during a 60° banked turn while maintaining altitude?
4,600 pounds EXPLANATION: Note on Fig. 2 that, at a 60° bank angle, the load factor is 2. Thus, a 2,300-lb. airplane in a 60° bank would require its wings to support 4,600 lb. (2,300 lb. × 2).
If an airplane weighs 4,500 pounds, what approximate weight would the airplane structure be required to support during a 45° banked turn while maintaining altitude?
6,750 pounds. EXPLANATION: Look on the left side of the chart in Fig. 2 under 45° and note that the load factor curve is 1.414. Thus, a 4,500-lb. airplane in a 45° bank would require its wings to support 6,363 lb. (4,500 lb. × 1.414). The closest answer choice to this value is 6,750 lb.
Ground effect is most likely to result in which problem?
Becoming airborne before reaching recommended takeoff speed. EXPLANATION: Due to the reduction of induced drag in ground effect, the airplane may seem capable of becoming airborne well below the recommended takeoff speed. However, as the airplane rises out of ground effect (a height greater than the wingspan) with a deficiency of speed, the increase in induced drag may result in very marginal initial climb performance. In extreme cases, the airplane may become airborne initially, with a deficiency of airspeed, only to settle back on the runway when attempting to fly out of the ground effect area.
What is the effect of advancing the throttle in flight?
Both aircraft groundspeed and angle of attack will increase. EXPLANATION: When advancing the throttle, the airspeed will increase; therefore, groundspeed will also increase. The aircraft will climb due to an increase in downwash over the horizontal stabilizer as power is applied and the lift created by the airspeed increase.
What must a pilot be aware of as a result of ground effect?
Induced drag decreases; therefore, any excess speed at the point of flare may cause considerable floating. EXPLANATION: Ground effect reduces the upwash, downwash, and vortices caused by the wings, resulting in a decrease in induced drag. Thus, thrust required at low airspeeds will be reduced, and any excess speed at the point of flare may cause considerable floating.
In what flight condition are torque effects more pronounced in a single-engine airplane?
Low airspeed, high power, high angle of attack. EXPLANATION: The effect of torque increases in direct proportion to engine power and inversely to airspeed. Thus, at low airspeeds, high angles of attack, and high power settings, torque is the greatest.
What causes an airplane (except a T-tail) to pitch nosedown when power is reduced and controls are not adjusted?
The downwash on the elevators from the propeller slipstream is reduced and elevator effectiveness is reduced. EXPLANATION: The relative wind on the tail is the result of the airplane's movement through the air and the propeller slipstream. When that slipstream is reduced, the horizontal stabilizer (except a T-tail) will produce less negative lift and the nose will pitch down.
What force makes an airplane turn?
The horizontal component of lift. EXPLANATION: When the wings of an airplane are not level, the lift is not entirely vertical and tends to pull the airplane toward the direction of the lower wing. An airplane is turned when the pilot coordinates rudder, aileron, and elevator to bank in order to attain a horizontal component of lift.
What determines the longitudinal stability of an airplane?
The location of the CG with respect to the center of lift. EXPLANATION: The location of the center of gravity with respect to the center of lift determines, to a great extent, the longitudinal stability of the airplane. Positive stability is attained by having the center of lift behind the center of gravity. Then the tail provides negative lift, creating a downward tail force, which counteracts the nose's tendency to pitch down.
What is ground effect?
The result of the interference of the surface of the Earth with the airflow patterns about an airplane. EXPLANATION: Ground effect is due to the interference of the ground (or water) surface with the airflow patterns about the airplane in flight. As the wing encounters ground effect, there is a reduction in the upwash, downwash, and the wingtip vortices. The result is a reduction in induced drag. Thus, for a given angle of attack, the wing will produce more lift in ground effect than it does out of ground effect.
Which basic flight maneuver increases the load factor on an airplane as compared to straight-and-level flight?
Turns. EXPLANATION: Turns increase the load factor because the lift from the wings is used to pull the airplane around a corner as well as to offset the force of gravity. The wings must carry the airplane's weight plus offset centrifugal force during the turn. For example, a 60° bank results in a load factor of 2; i.e., the wings must support twice the weight they do in level flight.
When does P-factor cause the airplane to yaw to the left?
When at high angles of attack. EXPLANATION: P-factor or asymmetric propeller loading occurs when an airplane is flown at a high angle of attack because the downward-moving blade on the right side of the propeller (as seen from the rear) has a higher angle of attack, which creates higher thrust than the upward-moving blade on the left. Thus, the airplane yaws around the vertical axis to the left.
Changes in the center of pressure of a wing affect the aircraft's
aerodynamic balance and controllability. EXPLANATION: Center of pressure (CP) is the imaginary but determinable point at which all of the upward lift forces on the wing are concentrated. In general, at high angles of attack the CP moves forward, while at low angles of attack the CP moves aft. The relationship of the CP to center of gravity (CG) affects both aerodynamic balance and controllability.
An airplane has been loaded in such a manner that the CG is located aft of the aft CG limit. One undesirable flight characteristic a pilot might experience with this airplane would be
difficulty in recovering from a stalled condition. EXPLANATION: The recovery from a stall in any airplane becomes progressively more difficult as its center of gravity moves backward. Generally, airplanes become less controllable, especially at slow flight speeds, as the center of gravity is moved backward.
Loading an airplane to the most aft CG will cause the airplane to be
less stable at all speeds. EXPLANATION: Airplanes become less stable at all speeds as the center of gravity is moved backward. The rearward center of gravity limit is determined largely by considerations of stability.
Floating caused by the phenomenon of ground effect will be most realized during an approach to land when at
less than the length of the wingspan above the surface. EXPLANATION: Ground effect is most usually recognized when the airplane is within one-half of the length of its wingspan above the surface. It may extend as high as a full wingspan length above the surface. Due to an alteration of the airflow about the wings, induced drag decreases, which reduces the thrust required at low airspeeds. Thus, any excess speed during the landing flare may result in considerable floating.
The airspeed indicated by points A and J is
normal stall speed. EXPLANATION: Points A and J are the normal stall speed (VS1). At this speed in the clean configuration, the airplane will stall. The normal stall speed is shown on the airspeed indicator at the low-speed end of the green arc.
The left turning tendency of an airplane caused by P-factor is the result of the
propeller blade descending on the right, producing more thrust than the ascending blade on the left. EXPLANATION: Asymmetric propeller loading (P-factor) occurs when the airplane is flown at a high angle of attack. The downward-moving blade on the right side of the propeller (as seen from the rear) has a higher angle of attack, which creates higher thrust than the upward-moving blade on the left. Thus, the airplane yaws around the vertical axis to the left.
An aircraft leaving ground effect during takeoff will
require an increase in angle of attack to maintain the same lift coefficient. EXPLANATION: During the takeoff phase of flight, ground effect produces some important relationships. The airplane leaving ground effect after takeoff encounters just the reverse of the airplane entering ground effect during landing; i.e., the airplane leaving ground effect will (1) require an increase in angle of attack to maintain the same lift coefficient, (2) experience an increase in induced drag and thrust required, (3) experience a decrease in stability and a nose-up change in moment, (4) produce a reduction in static source pressure and an increase in indicated airspeed.
An airplane said to be inherently stable will
require less effort to control. EXPLANATION: An inherently stable airplane will usually return to the original condition of flight (except when in a bank) if disturbed by a force such as air turbulence. Thus, an inherently stable airplane will require less effort to control than an inherently unstable one.
The amount of excess load that can be imposed on the wing of an airplane depends upon the
speed of the airplane. EXPLANATION: The amount of excess load that can be imposed on the wing depends upon how fast the airplane is flying. At low speeds, the maximum available lifting force of the wing is only slightly greater than the amount necessary to support the weight of the airplane. Thus, any excess load would simply cause the airplane to stall. At high speeds, the lifting capacity of the wing is so great (as a result of the greater flow of air over the wings) that a sudden movement of the elevator controls (strong gust of wind) may increase the load factor beyond safe limits. This is why maximum speeds are established by airplane manufacturers.
During an approach to a stall, an increased load factor will cause the aircraft to
stall at a higher airspeed. EXPLANATION: The greater the load (whether from gross weight or from centrifugal force), the more lift is required. Therefore, an aircraft will stall at higher airspeeds when the load and/or load factor is increased.
A positive load factor of 2 at 80 mph would cause the airplane to
stall. EXPLANATION: The Velocity vs. G-loads chart (Fig. 73) has indicated airspeed on the horizontal axis and load factor on the vertical axis. Locate the intersection of 2 on the vertical axis and 80 on the horizontal axis. Notice that operating where these coordinates intersect, which is the blue shaded area, would be indicative of a stalled condition.
