Performance and Limitations Flashcards
What are the four dynamic forces that act on an airplane during all maneuvers
Lift - the upward acting force
Gravity - weight, the downward acting force
Thrust - the forward acting force
Drag - The backward acting force
What flight conditions will result in the sum of the opposing forces being equal
IN steady-state, straight-and-level, unaccelerated flight, the sum of the opposing forces is equal to zero. There can be no unbalanced forces in steady, straight flight (newton’s 3rd law). This is true whether flying level or when climbing or descending. It does not mean the four forces are equal. It means the opposing forces are equal to, and thereby cancel the effects of each other.
What is an airfoil? State some examples
An airfoil is a device which gets a useful reaction from air moving over its surface, namely LIFT. Wings, horizontal tail surface, vertical tail surfaces, and propellers are examples of airfoils
What is the angle of incidence
The angle of incidence is the angle formed by the longitudinal axis of the airplane and the chord of the wing. It is measured by the angle at which the wing is attached to the fuselage. The angle of incidence is fixed and cannot be changed by the pilot
What is relative wind
The relative wind is the direction of the airflow with respect to the wing. When a wing is moving forward and downward the relative wind moves backward and upward. The flight path and relative wind are always parallel but travel in opposite directions
What is the angle of attack
The angle of attack is the angle between the wing chord line and the direction of the relative wind; it can be changed by the pilot
What is Bernoulli’s Principle
The pressure of a fluid (liquid or gas) decreases at points where the speed of the fluid increases. In the case of airflow, high speed flow is associated with low pressure and low speed flow with high pressure. The airfoil of an aircraft is designed to increase the velocity of the airflow above its surface, thereby decreasing pressure above the airfoil. Simultaneously, the impact of the air on the lower surface of the airfoil increases the pressure below. This combination of pressure decrease above and increase below produces life
What are several factors which will affect both lift and drag
Wing area - lift and drag action on a wing are roughly proportional to the wing area. A pilot can change wing area by using certain types of flaps
Shape of the airfoil - As the upper curvature of an airfoil is increased (up to a certain point) the lift produced increases. Lowering an aileron or flap device can accomplish this. Also, ice or frost on a wing can disturb normal airflow, changing its camber, and disrupting its lifting capability
Angle of attack - As angle of attack increases, both lift and drag are increased, up to a certain point
Velocity of the air - An increase in velocity of air passing over the wing increases lift and drag
Air density - Lift and drag vary directly with the density of the air. As air density increases, lift and drag increase. As air density decreases, lift and drag decrease. Air density is affected by these factors: pressure, temperature, and humidity
What is torque effect
Torque effect involves Newton’s third law of physics - for every action, there is an equal and opposite reaction. Applied to the airplane, this means that as the internal engine parts and the propeller are revolving in one direction, an equal force is trying to rotate the airplane in the opposite direction. It is greatest when at low airspeeds with high power settings and a high angle of attack
What effect does torque reaction have on an airplane on the ground and in flight
In flight - Torque reaction is acting around the longitudinal axis, tending to make the airplane roll. To compensate, some of the older airplanes are rigged in a manner to create more lift on the wing that is being forced downward. The more modern airplane are designed with the engine offset to counteract this effect of torque.
On the ground - during the takeoff roll, an additional turning moment around the vertical axis is induced by torque reaction. As the left side of the airplane is being forced down by torque reaction, more weight is being placed on the left main landing great. This results in more ground friction, or drag, on the left tire than on the right, causing a further turning moment
What are the four factors that contribute to torque effect
Torque reaction of the engine and propeller. For every action there is an equal and opposite reaction. The rotation of the propeller to the right, tends to roll or bank the airplane to the left
Gyroscopic effect of the propeller. Gyroscopic precession applies here: the resultant action or deflection of a spinning object when a force is applied to the outer rim of its rotational mass. If the axis of a propeller is tilted, the resulting force will be exerted 90 degrees ahead in the direction of rotation and in the same direction as the applied force. It is most noticeable on takeoff in taildraggers when the tail is raised
Corkscrewing effect of the propeller slipstream. High-speed rotation of an airplane propeller results in a corkscrewing rotation to the slipstream as it moves rearward. At high propeller speed and low forward speed, as in a takeoff, the slipstream strikes the vertical tail surface on the left side pushing the tail to the right and yawing the airplane to the left
Asymmetrical loading of the propeller (P-factor). When an airplane is flying with a high angle of attack, the bite of the downward moving propeller blade is greater than the bite of the upward moving blade. This is due to the downward moving blade meeting the oncoming relative wind at a greater angle of attack than the upward moving blade. Consequently there is greater thrust on the downward moving blade on the right side, and this forces the airplane to yaw to the left
What is centrifugal force
Centrifugal force is the equal and opposite reaction of the airplane to the change in direction, and it acts equal and opposite to the horizontal component of lift
What is load factor
Load factor is the ratio of the total load supported by the airplane’s wing to the actual weight of the airplane and its contents. In other words, it is the actual load supported by the wings divided by the total weight of the airplane. It can also be expressed as the ratio of a given load to the pull of gravity. That is to refer to a load factor of three as 3Gs. In this case the weight of the airplane is equal to 1G and if a load of three times the actual weight of the airplane were imposed upon the wing due to curved flight, the load factor would be equal to 3Gs
For what two reasons is load factor important to pilots
because of the obviously dangerous overload that it is possible for a pilot to impose on the aircraft structure
Because an increase load factor increases the stalling speed and makes stalls possible at seemingly safe flight speeds
What situations may result in load factors reaching the maximum or being exceeded
Level Turns - The load factor increases at a terrific rate after a bank has reached 45 or 50 degrees. The load factor in a 60 degree bank turn is 2G. The load factor in an 80 degree bank turn is 5.7G. The wing must produce lift equal to these load factors if altitude is to be maintained
Turbulence - Severe vertical gusts cause a sudden increase in angle of attack, resulting in large load which are resisted by the inertial of the airplane
Speed - The amount of excess load that can be imposed upon the wing depends on how fast the airplane is flying. At speeds below maneuvering speed, the airplane will stall before the load factor can become excessive. At speeds above maneuvering speed, the limit load factor for which an airplane is stressed can be exceeded by abrupt or excessive application of the controls or by strong turbulence
What are the different operational categories for aircraft and within which category does your aircraft fall
Normal - +3.8 to -1.52*
Utility - +4.4 to -1.76
Aerobatic - +6 to -3
What effect does an increase in load factor have on stalling speed
As load factor increases, stalling speed increases. Any airplane can be stalled at any airspeed within the limits of its structure and the strength of the pilot. At a given airspeed the load factor increases as angle of attack increases, and the wing stalls because the angel of attack has been increased to a certain angle. Therefore, there is a direct relationship between the load factor imposed upon the wing and its stalling characteristics. A rule for determining the speed at which a wing will stall is that the stalling speed increases in proportion to the square root of the load factor
Define the term maneuvering speed
Maneuvering speed is the maximum speed at which the limit load can be imposed (either by gusts or full deflection of the control surfaces) without causing structural damage. It is the speed below which you can, in smooth air, move a single flight control one time to its full deflection for one axis of airplane rotation only (pitch, roll or yaw) without risking of damage to the airplane. Speeds up to, but not exceeding the maneuvering speed allow an aircraft to stall prior to experiencing an increase in load factor that would exceed the limit load of the aircraft.
Discuss the effect on maneuvering speed of an increase or decrease in weight
Maneuvering speed increase with an increase in weight and decreases with a decrease in weight. An aircraft operating at a reduced weight is more vulnerable to rapid accelerations encountered during flight through turbulence or gusts. Design limit load factors could be exceeded if a reduction in maneuvering speed is not accomplished. An aircraft operating at or near gross weight in turbulent air is much less likely to exceed design limit load factors and may be operated at the published maneuvering speed for gross weight if necessary
Define LOC-I and describe several situations that might increase the risk of an LOC-I accident occurring
LOC-I is defined as a significant deviation of an aircraft from the intended flight path and it often results from an airplane upset. Maneuvering is the most common phase of flight for LOC-I accident to occur; however, LOC-I accidents occur in all phases of flight. Situations that increase the risk of this include uncoordinated flight, equipment malfunctions, pilot complacency, distraction, turbulence, and poor risk management, such as attempting to fly in IMC when the pilot is not qualified or proficient in it
What causes an airplane to stall
The direct cause of every stall is an excessive angle of attack. Each airplane has a particular angle of attack where the airflow separate from the upper surface of the wing and the stall occurs. This critical angle of attack varies from 16 to 20 degrees depending on the airplane’s design, but each airplane has only one specific angle of attack where the stall occurs, regardless of airspeed, weight, load factor, or density altitude
What is a spin
A spin in a small airplane or glider is a controlled or uncontrolled maneuver in which the airplane or glider descends in a helical path while flying at an angle of attack greater than the critical angel of attack. Spins result from aggravated stalls in either a slip or skid. If a stall does not occur, a spin cannot occur
What causes as spin
The primary cause of an inadvertent spin is exceeding the critical angel of attack while applying excessive or insufficient rudder and to a lesser extent aileron
When are spins most likely to occur
A stall/spin situation can occur in any phase of flight but is most likely to occur in the following situations
Engine failure on takeoff during clime out - pilot tries to stretch glide to landing area by increasing back pressure or makes an uncoordinated turn back to departure runway at a relatively low airspeed
Crossed-control turn from base to final - pilot overshoots final and makes uncoordinated turn at a low airspeed
Engine failure on approach to landing - pilot tries to stretch glide to runway by increasing back pressure
Go-around with full nose up trim - pilot applies power with full flaps and nose-up trim combine with uncoordinated use of rudder
Go-around with improper flap retraction - pilot applies power and retracts flaps rapidly resulting in a rapid sink rate followed by an instinctive increase in back pressure
What procedure should be used to recover from an inadvertent spin
Close the throttle
Neutralize the ailerons
Apply full opposite rudder
Briskly move the elevator control forward to neutral position
Neutralize the rudder when the spin stops
Gradually apply enough aft elevator pressure to return to level flight
What causes adverse yaw
When turning an airplane to the left for example, the downward deflected aileron on the right produces more lift on the right wing. Since the downward deflected right aileron produces more lift, it also produces more drag, while the opposite left aileron has less lift and less drag. This added drag attempt to pull or veer the airplane’s nose in the direction of the raised wing; that is; it tries to turn the airplane in the direction opposite to that desired. This undesired veering is referred to as adverse yaw
What is ground effect
Ground effect is a condition of improved performance the airplane experiences when it is operating near the ground. A change occurs in the 3D flow pattern around the airplane. because the airflow around the wing is restricted by the ground surface. This reduces the wing’s upwash, downwash, and wingtip vortices. In order for ground effect to be of a significant magnitude, the wing must be quite close to the ground
What major problems can be caused by ground effect
During landing at a height of approximately one-tenth of a wing span above the surface, drag may be 40 percent less than when the airplane is operating out of ground effect. Therefore, an excess speed during landing phase may result in a significant float distance. In such cases, if care is not exercised by the pilot, he/she may run out of runway and options at the same time
During takeoff due to the reduces drag in ground effect, the aircraft may seem capable of takeoff well below the recommended speed. However, as the airplane rises out of ground effect with a deficiency of speed, the greater induces drag may result in very marginal climb performance, or the inability of the airplane to fly at all. In extreme conditions, such as high temperature, high gross weight, and high-density altitude, the airplane may become airborne initially with a deficiency of speed and then settle back to the runway
Define the following: Empty weight, gross weight, useful load, arm, moment, center of gravity, datum
Empty weight - The weight of the airframe, engines, all permanently installed equipment, and unusable fuel. Depending on the FARs under which the aircraft was certificated, either the undrainable oil or full reservoir of oil is included
Gross weight - The maximum allowable weight of both the airplane and its contents
Useful load - the weight of the pilot, copilot, passengers, baggage, usable fuel and drainable oil
Arm - The horizontal distance in inches from the reference datum line to the center of gravity of the item
CG - The point about which an aircraft would balance if it were possible to suspend it at that point. Expressed in inches from datum
Datum - An imaginary vertical plane or line from which all measurement of are are taken. Established by the manufacturer
What basis equation is used in all weight and balance problems to find the CG location of an airplane and/or its components
Weight X Arm = Moment
Weight = Moment / Arm
Arm (CG) = (Total) Moment / (Total) Weight
What performance characteristics will be adversely affected when an aircraft has been overloaded
Higher takeoff speed Longer take off roll Reduced rate and angle of climb Lower maximum altitude Shorter range Reduced cruising speed Reduced maneuverability Higher stalling speed Higher landing speed Longer landing roll Excessive weight on the nosewheel
What effect does a forward center of gravity have on an aircraft’s flight characteristics
higher stall speed - stalling angle of attack is reached at a higher speed due to increased win loading
more stable - center CG is farther forward from the center of pressure which increases longitudinal stability
Greater back elevator pressure required - longer takeoff roll; higher approach speeds and problems with landing flare
