Structures and Design Part 3 1Aero Flashcards
Deployed from the wings to spoil the smooth airflow, reducing lift and increasing drag.
Spoilers
- used for roll control, an advantage of which is the elimination of adverse yaw.
Roll Spoiler
- allows the aircraft to descend without gaining speed
Speed Brake
- destroying lift, they transfer weight to the wheels, improving braking effectiveness. Usually, all spoilers are deployed
Ground Spoiler
are used to relieve the pilot of the need to maintain constant pressure on the flight controls,
Trim Systems
- Aerodynamically assist movement and position of the flight control surface to which they are attached.
Trim tab / Trim System
- Typically .15 to .20 area of the rudder and elevator
Trim tab / Trim System
goes the opposite direction of the desired control movement.
Trim Tabs
If Trim Wheel is Backward then Trim Tabs are
Down
If Trim Wheel is Forward then Trim Tabs are
Up
aerodynamically assist in moving control surface
* It is coupled to the control surface rod so that when the primary control surface is moved in any direction, the tab automatically moves in the opposite direction
Balance Tabs
- They look like trim tabs and are hinged in approximately the same places as trim tabs
Balance Tabs
- Works same as Balance tabs that aerodynamically assist in moving control surface
- Only difference is that they move on same direction as control surface
Anti-Servo Tab
- This tab is bent in one direction or the other while on the ground to apply a trim force to the rudder.
Anti-Servo Tab
- The correct displacement of this tab is determined by trial and error.
- Usually, small adjustments are necessary until the aircraft no longer skids left or right during normal cruising flight.
Anti-Servo Tab
Rather than using a movable tab on the trailing edge of the elevator, some aircraft have an adjustable stabilizer.
Trimmable Horizontal Stabilizer
Stabilizer
* With this arrangement, linkages pivot the horizontal stabilizer about its rear spar.
* This is accomplished by use of a jackscrew mounted on the leading edge of the stabilator
Trimmable Horizontal Stabilizer
- Angle of bank is too great for the rate of the turn
- Too much aileron, too little rudder
Slipping Turn
- rate of turn is too great for the bank angle
- Too much Rudder, too little Aileron
Skidding Turn
many aircraft use electrically heated systems to prevent ice from obscuring the vision of the flight crew
Windows
are typically made of the 3 plies with conductive coating in between.
Cockpit windows
The purpose of the (Blank) is to pull the airplane through the Air.
Propeller
It does this by means of the thrust obtained by the action of the rotating blades on the air
Propeller
normally consist of two or more blades and central hub by which are attached to a shaft driven by the Engine
Propeller
- the variation in airfoil shape and blade angle along the length of a propeller blade compensates for differences in rotational speed and allows for a more even distribution of thrust along the blade.
Blade Element Theory
- as a propeller blade rotates at a fixed rpm, each blade- segment moves through the air at a different velocity. V = 2πr x rpm
Blade Element Theory
V = 2πr x rpm
Blade Element Theory - Velocity
mounted on the front of an engine and pull an aircraft through the air.
Tractor propeller
mounted on the aft end of an aircraft and push an airplane through the air.
Pusher propeller
Seven inches (for each airplane with nose wheel landing gear)
Ground clearance
Nine inches (for each airplane with tail wheel landing gear) between each propeller and the ground with the landing gear statically deflected and in the level takeoff, or taxiing attitude, whichever is most critical.
Ground clearance.
there must be positive clearance between the (blank) and the ground when in the level takeoff attitude with the critical tire(s) completely deflated and the corresponding landing gear strut bottomed.
Propeller
at least 18 inches between each propeller and the water,
Water clearance
At least one inch radial clearance between the blade tips and the airplane structure, plus any additional radial clearance necessary to prevent harmful vibration;
Structural clearance
At least one-half inch longitudinal clearance between the propeller blades or cuffs and stationary parts of the airplane; and
Structural clearance
Positive clearance between other rotating parts of the propeller or spinner and stationary parts of the airplane.
Structural clearance
refers to the distance a spiral threaded object moves forward in one revolution. As a wood Screw moves forward when turned in wood, same with the propeller move forward when turn in the air
Pitch
- is theoretical distance a propeller would advance in one revolution.
- tan-1 pitch angle 2r
Geometric pitch
is the actual distance a propeller advances in one revolution in the air. The (Blank) is always shorter than geometric pitch due to the air is a fluid and always slip.
Effective pitch
has the blade pitch, or blade angle, built into the propeller. The blade angle cannot be changed after the propeller built
fixed pitch propeller
installed on a light aircraft has a diameter between 67 and 76 inches and a pitch between 53 and 68 inches
fixed pitch propeller
aircraft manufacturers are normally designed blade pitch in inches at 75% radius
fixed pitch propeller
Types of Propellers:
to provide the best all around performance under normal circumstances.
Standard propeller
Types of Propellers:
a propeller with the lower blade angle provides the best performance for take-off and climb.
Climb propeller
Types of Propellers:
the low blade angle allows the engine to develop its maximum rpm at the slower airspeed associated with the climb out. However once the aircraft reaches its cruising altitude and begins to accelerate the, low blade angle becomes inefficient.
Climb propeller
Types of Propellers:
is designed to be efficient at cruising speed at high altitude flight, however because of the higher pitch, cruise propeller are very inefficient during take-off and climb out.
Cruise propeller
Types of Propellers:
operates as a fixed pitch propeller. The pitch or blade angle can be changed only when the propeller is not turning. This is done by loosening the clamping which hold the blades in place after the clamping mechanism which hold the blades in place.
Ground- adjustable propeller
Types of Propellers:
The pitch of the blades cannot be change in flight to meet variable flight requirements. Like the fixed-pitch propeller.
Ground- adjustable propeller
Types of Propellers:
is used on airplanes of low power, speed, range, or altitude.
Ground- adjustable propeller
Types of Propellers:
utilized either clamp rings or bolts to secure the hub valves and holds the blade tightly.
Ground- adjustable propeller
Types of Propellers:
* uses to balance between the aerodynamic twisting force to maintain a relatively constant speed for any given throttle setting
Automatic (Aeromatic ) propeller
Types of Propellers:
the forces were amplified by offsetting the blades from the hub with a pronounced lag angle to
* increase the effect of the centrifugal twisting force trying to move the blades into a low pitch, and by installing counter weights on the blade roots to help move the blades into the high pitch.
Automatic (Aeromatic ) propeller
Types of Propellers:
* other called variable pitch or controllable-pitch propeller
Constant-Speed propeller
Types of Propellers:
* the main advantage of (Blank) is that it converts a high percentage of the engines power into thrust over a wide range of rpm and airspeed combinations
Constant-Speed propeller
Types of Propellers:
* the primary reason why a (Blank) is more efficient than other propellers is because it allows the operator to select the most efficient engine rpm for the given conditions
Constant-Speed propeller
Effect of Propeller:
In airplanes with a single engine, the propeller rotates clockwise when viewed from the pilot’s seat. Torque can be understood most easily by remembering Newton’s third law of motion
Propeller torque effect
Effect of Propeller:
The clockwise action of a spinning propeller causes a torque reaction which tends to rotate the airplane counter-clockwise about its longitudinal axis.
Propeller torque effect
Effect of Propeller:
Generally, aircraft have design adjustments which compensate for torque while in cruising flight. For example, some aircraft have aileron trim tabs which correct for the effects of torque at various power settings.
Propeller torque effect
Effect of Propeller:
The turning propeller of an airplane also exhibits characteristics of a gyroscope – rigidity in space and precession. The characteristic that produces a left-turning tendencies is precession
Gyroscopic precession
Effect of Propeller:
is the resultant reaction of an object when force is applied. The reaction to a force applied to a gyro acts 90° in the direction of rotation
Gyroscopic precession
When a single-engine airplane is at high angle of attack, the descending blade of the propeller takes a greater “bite” of air than the ascending blade on the other side.
P-Factor / Asymmetrical Thrust
The greater bite is caused by higher angle of attack for the descending blade, compared to the ascending blade.
P-Factor / Asymmetrical Thrust
This creates the uneven, or asymmetrical thrust, which is known as (blank). (blank) makes an aircraft yaw about its vertical axis to the left.
P-Factor / Asymmetrical Thrust
- As the propeller rotates, it produces a backward flow of air, or slipstream, which wraps around the airplane.
Spiraling slipstream / Propwash
This (Blank) causes a change in the airflow around the vertical stabilizer.
Spiraling slipstream / Propwash
- Due to the direction of the propeller rotation, the resultant slipstream strikes the left side of the vertical fin and causes a yaw to the left.
Spiraling slipstream / Propwash
On propeller aircraft, there is a difference in the remaining yawing moments after failure of the left or the right (outboard) engine when all propellers rotate in the same direction due to the P-factor
Critical Engine
- Support the weight of the aircraft when it is on the ground
Landing Gear
- Absorb the impact loads during landing and taxi
Landing Gear
- Enable the aircraft to decelerate after landing and aborted take off
Landing Gear
- Enable the aircraft to move and maneuver on the ground
Landing Gear
Landing Gear Configuration:
▪ Employed by many sailplanes for its simplicity
Single Main
Landing Gear Configuration:
* Flat attitude take-off and landing; aircraft must have high lift at low AOA (high AR with large camber and/or flaps)
Bicycle
Landing Gear Configuration:
* Used by aircraft with narrow fuselage and wide wing span (e.g. B-47, U2)
Bicycle
Landing Gear Configuration:
▪ More propeller ground clearance
▪ Less drag and weight
Conventional / Trail Dragger
Landing Gear Configuration:
▪ Easier lift production due to attitude, hence initial AOA
▪ Inherently unstable (ground looping)
Conventional / Trail Dragger
Landing Gear Configuration:
▪ Limited ground visibility from cockpit
▪ Inconvenient floor attitude
Conventional / Trail Dragger
If the tail wheel is too close to the front wheels or the front wheels are close together in relation to span of the wing, the aircraft may
ground loop
a phenomenon in which the airplane may pivot on one wheel, meanwhile dragging a wing tip along the ground
ground loop
If brakes were immediately used upon level landing, the inertia of the airplane might be sufficient to
nose it over
It is necessary to put the (Blank) farther forward for landing gear employing brakes than one without.
Wheels
Landing Gear Configuration:
▪ Stable on the ground; can be landed with a large “crab angle” (nose not aligned with runway)
Tricycle
Landing Gear Configuration:
▪ Improved forward ground visibility
▪ Flat cabin floor for passenger and cargo loading
Tricycle
Landing Gear Configuration:
Many small, single engine light aircraft have (Blank) landing gear, as do a few light twins.
This means the gear is attached to the airframe and remains exposed to the slipstream as the aircraft is flown.
Fixed Landing Gear
Landing Gear Configuration:
stow in fuselage or wing compartments while in flight.
Once in these wheel wells, gear are out of the slipstream and do not cause parasite drag.
Retractable Landing Gear
Landing Gear Configuration:
Most (Blank) have a close fitting panel attached to them that fairs with the aircraft skin when the gear is fully retracted
Retractable Landing Gear
Landing Gear Configuration: These Notes are for what configurations?
1. There must be positive means to keep the landing gear extended
2. There must be an emergency means for extending the landing gear
3. There must be a position indicator
Retractable Landing Gear
Shock Absorbing and Non-Shock Absorbing Landing Gear:
do not actually absorb these shocks but rather accept the energy in some form of elastic medium and return it at a rate and time that the aircraft can accept.
Spring Steel and Composites
Shock Absorbing and Non-Shock Absorbing Landing Gear:
transmit all the loads of landing touchdown directly to the airframe’s structure. Some of the shock is absorbed by the elasticity of the tires.
Rigid Gear
Shock Absorbing and Non-Shock Absorbing Landing Gear:
Some aircraft use rubber doughnuts or as a bungee cord, which is a bundle of small strands of rubber encased in a loosely woven cloth tube to cushion the shock of landing. (Blank) accept both landing impact and taxi
shocks
Bungee Cord
Shock Absorbing and Non-Shock Absorbing Landing Gear:
The most widely used shock absorber for aircraft is the air-oil shock absorber.
Shock struts /Oleo struts
Shock Absorbing and Non-Shock Absorbing Landing Gear:
The cylinder of this strut is attached to the
aircraft structure, and a close fitting piston is free to move up and down inside the cylinder.
Shock struts /Oleo struts
Braking System:
In general, small, light aircraft and aircraft without hydraulic systems use independent braking systems. An independent brake system is not connected in any way to the aircraft hydraulic system.
Independent Master Cylinder
Braking System:
are used to develop the necessary hydraulic pressure to operate the brakes. This is similar to the brake system of an automobile.
Independent Master Cylinder
In most brake actuating systems, the pilot pushes on the tops of the rudder pedals to apply the brakes.
A (Blank) for each brake is mechanically connected to the corresponding rudder pedal (i.e., right main brake to the right rudder pedal, left main brake to the left rudder pedal).
Independent Master Cylinder
Braking System:
When the pedal is depressed, a piston inside a sealed fluid-filled chamber in the master cylinder forces hydraulic fluid through a line to the piston(s) in the brake assembly.
Independent Master Cylinder
Braking System:
The brake piston(s) push the brake linings against the brake rotor to create the friction that slows the wheel rotation. Pressure is increased throughout the entire brake systems and against the rotor as the pedal is pushed harder.
Independent Master Cylinder
Braking System:
In an independent braking system, the pressure applied to the brakes is only as great as the foot pressure applied to the top of the rudder pedal. Boosted brake actuating systems augment the force developed by the pilot with hydraulic system pressure when needed.
Boosted Brakes
Braking System:
The boost is only during heavy braking. It results in greater pressure applied to the brakes than the pilot alone can provide. Boosted brakes are used on medium and larger aircraft that do not require a full power brake actuating system.
Boosted Brakes
Braking System:
A (Blank) master cylinder for each brake is mechanically attached to the rudder pedals. However, the boosted brake master cylinder operates differently.
Boosted Brakes
Braking System:
Large and high performance aircraft are equipped with (Blank) to slow, stop, and hold the aircraft.
Power Brakes
Braking System:
(Blank) actuating systems use the aircraft hydraulic system as the source of power to apply the brakes.
The pilot presses on the top of the rudder pedal for braking as with the other actuating systems. The volume and pressure of hydraulic fluid required cannot be produced by a master cylinder.
Power Brakes
Braking System:
Instead, a power brake control valve or brake metering valve receives the brake pedal input either directly or through linkages.
Power Brakes
Braking System:
The valve meters hydraulic fluid to the corresponding brake assembly in direct relation to the pressure applied to the pedal.
Power Brakes
is the tendency for the airplane to return to its previous attitude once disturbed.
Stability
For an airplane, (Blank) means that if a gust of air or some other perturbation causes a change in its current state such as heading, it will experience a restoring force
Static Stability
The aircraft has tendency to return to its original attitude after being influenced by gust of air or some other perturbation
Positive Static Stability (Stable)
The aircraft has a tendency to maintain its current attitude after being influenced by gust of air or some other perturbation
Neutral Static Stability (Neutral)
The aircraft will continue to change attitude after being influenced by gust of air or some other perturbation
Negative Static Stability (Unstable)
is influenced by the position of the wing’s C.G. and C.P.. This stability affects the design of the horizontal stabilizers and elevator.
Longitudinal Stability
C.G. is in front of the C.P. If a gust affects the wing, the C.G. will torque down to its original attitude
Positive Longitudinal Static Stability (Stable)
The aircraft has a tendency to maintain its current attitude after being influenced by gust of air or some other perturbation
Neutral Longitudinal Static Stability (Neutral)
C.G. is at the back of the C.P. If a gust affects the wing, the C.G. torque the wing backwards and increase angle of attack.
Negative Longitudinal Static Stability (Unstable)
The following should be considered to take longitudinal stability in aircraft design:
* Distance of C.G to the
horizontal stabilizer
The following should be considered to take longitudinal stability in aircraft design:
* Size of the
* Size of the
horizontal stabilizer and Elevator
An airplane is said to possess (Blank) if after undergoing a disturbance that rolls it to some bank angle ø [Greek letter theta], it generates forces and moments that tend to reduce the bank angle and restore the equilibrium flight condition.
Lateral Stability
The following affects lateral stability in an aircraft:
* Wing placement
* High wing –
Laterally Stable
The following affects lateral stability in an aircraft:
* Wing placement
* Low wing –
Laterally destabilizing
The following affects lateral stability in an aircraft:
* D***
Dihedral
The following affects lateral stability in an aircraft:
* Wing
Sweep
The vertical stabilizer also provides resistance to Roll.
Lateral stability also affects
Directional stability
is the stability in the yaw axis, and gives rise to the vertical stabilizer.
Directional Stability
The desire for (Blank) is to have the airplane always line itself with the wind.
Directional Stability
So, if a gust temporarily perturbs the
direction the nose is pointed, the tail will have a nonzero angle of attack with the airflow. This causes a restoring force to
realign the tail with the direction of travel.
Directional Stability
- For single engine size is influenced by vertical height of forward fuselage and needed to counter propeller rotation effects and adverse yaw in a turn.
affects lateral stability
For multi-engine the size of the (Blank) is dictated by the torque caused by the loss of one engine. The (Blank) should compensate the torque caused by net thrust being off center.
Tail
deals with the tendency of the airplane when disturbed to return to its original flight attitude.
Static stability
deals with how the motion caused by a disturbance changes with time.
Dynamic stability
When the airplane pitched up, there was a restoring force (statically stable). The path oscillates through the original altitude and with the oscillations decreasing with time
Positive Dynamic Stability
The airplane is statically stable because there is a restoring force. But the amplitude of the oscillations in this case does not decrease with time
Neutral Dynamic Stability
Again the airplane is statically stable but the amplitude of the oscillations increases with time
Negative Dynamic Stability
is a trade between kinetic and potential energy, that is, speed and altitude. It occurs at a constant angle of attack so as the speed increases, so does the lift.
Phugoid motion
The extra lift causes the airplane to increase altitude. As it does, the airspeed falls off, decreasing lift, and thus eventually altitude.
Phugoid motion
is a result of positive lateral stability with a weak directional stability.
Dutch roll
Strong lateral stability begins to restore the aircraft to level flight. At the same time, somewhat weaker directional stability attempts to correct the sideslip by aligning the aircraft with the perceived relative wind.
Dutch roll
Since directional stability is weaker than lateral stability for the particular aircraft, the restoring yaw motion lags significantly behind the restoring roll motion.
Dutch roll
The aircraft passes through level flight as the yawing motion is continuing in the direction of the original roll. At that point, the sideslip is introduced in the opposite direction and the process is reversed.
Dutch roll
is a result of positive directional stability with a weak lateral stability.
Spiral Divergence
