SIFT Study Guide

Newton's First Law (Law of Inertia)

An object in motion (or at rest) will tend to stay in motion (or at rest) until it is acted upon by an outside force.

Interia

The tendency of an object to resist a change in velocity whether the object is in motion or motionless

kinetic friction

when the surface of one object slides along the surface of another object, static friction overcome. size of the friction force increases with an object's weight.

fluid friction

a friction force that opposes the motion of an object through a fluid (liquid or gas)

rolling friction

friction that occurs when an object rolls over a surface

static friction

a friction force that acts on objects that are not moving by an external force, always equal to the force applied to the object.

Newton's Second Law

F=ma

Force equals mass times acceleration

Newton's Third Law

For every action force there is an equal and opposite reaction force

Newton's Law of Universal Gravitation

a particle attracts every other particle in the universe with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.

Newton's Law of Universal Gravitation Equation

Bernoulli's Principle

as the velocity of a fluid increases, the pressure exerted by the fluid decreases (hydrodynamics)

weight

force of gravity pushing the aircraft down

lift

force required to raise the aircraft

thrust

force applied to move aircraft forward

drag

force that slows the aircraft down in prep for landing

Empty Weight Center of Gravity (EWCG)

predetermined calculation of an aircraft's weight and balance

Manufacturer's Empty Weight (MEW)

Total weight of the aircraft as it was built.

Operating Empty Weight (OEW)

MEW plus the weight of the crew, fluids, unusable fuel, and the equipment required for flight.

All-Up Weight (AUW) or Aircraft Gross Weight (AGW)

Total aircraft weight at any given moment during a flight

decreases as fuel and fluids are consumed during the operation

Maximum Landing Weight (MLW)

Aircraft's weight limit for landing

Maximum Zero Fuel Weight (MZFW)

Permissible weight of an aircraft with its contents and includes unusable fuel. excludes the weight of usable fuel on board

Maximum Takeoff Weight (MTOW)

aircraft's weight limit for takeoff

Maximum Ramp Weight (MRW)

The weight limit for an aircraft to taxi or be towed on the ground.

Flight Envelope

Encompasses the limits of speed, altitude, and angle of attack required by any aircraft to maintain a stable flight.

Angle of Attack (AOA)

The angle between the direction of airflow against the wing and the chord

Downwash

the downward movement of air behind a wing in flight

Ailerons

Located on the trailing edge of the wing to provide roll control

Flaps

Control surfaces attached to the trailing edge of the wing extending outward from the fuselage to the midpoint of each wing. can increase the lifting efficiency of the wing and decrease stall speed.

Spoilers

devices located on the wings that disrupt the airflow over the wing causing loss of lift, reduce airspeed, and aid in landing

Parasite Drag

low air pressure in tires, skin friction, or anything that increases turbulence on the aircraft

Profile Drag

produced mainly by the shape of the aircraft

Induced Drag

When at the back of the wing air flowing rapidly across the top meets air flowing more slowly underneath creating a vortex. increases when lift, airspeed, and AOA increase

Longitudinal Axis (roll)

runs lengthwise from the nose to the tail of the aircraft

Lateral Axis (Pitch)

Runs wingtip to wingtip

Vertical Axis (yaw)

Runs perpendicular to the wings at the center of the aircraft

trim

desired position of an aircraft

adjusting the ailerons...

controls the roll of the aircraft

adjusting the elevators...

controls the pitch of the aircraft

adjusting the rudder...

controls the yaw of the aircraft

atomospheric pressure

14.7 pounds per square inch (psi)

Humidity and low air density

reduce an aircraft's capability for power, thrust, and lift

pressure altimeter

automatically calibrated for 29.92 inches of mercury (Hg)

All aircraft perform more efficiently in ____ temps because air is denser than when the air is warm.

colder temps

Mast/Shaft

long cylindrical component that extends vertically from the main rotor transmission up to the main rotor hub. responsible for the rotational drive force that turns the main rotor hub.

components of the main rotor head

blade grips, rotor blades, the pitch horn (yoke), stabilizer bar and weight (flybar), and the teeter hinge (trunnion)

blade grips

connect rotor blades to the rotor system and allow the rotor blades to feather (change AOA)

rotor blade

A rotating wing on a helicopter that provides lift.

pitch horn/ yoke

extends perpendicular to the main rotor blades. connects directly to the blade grips and stabilizer bar and receives control inputs from the pilot and translate it into force moving the blade grips

stabilizer bar and weight/ flybar

help to maintain a constant plane of rotation for the rotor blades. connects to the swashplate via mechanical linkages that combine with the fly bar to dampen any over control by the pilot and weather extreme gusts

teeter hinge/ trunnion

connects the mast to the , main rotor hub. allows the rotor hub and blades to flap up and down depending on control input and aerodynamic forces. when one blade rises, the teeter hinge allows the opposite blade to fall in its plane of rotation

components of main rotor transmission

below the mast and the main rotor hub's components. consists of swashplate, scissors link, pitch links, tail boom.

Swashplate

mounted to the transmission and allows directional control. consists of an inner non rotating and an outer rotating that form concentric rings which rest on a type of bearing that allows it to tilt and move up and down. the mast runs through the center and as it turns, driving the main rotor system, a scissors link connected to the mast in turn drives the outer rotating one. the inner one lifts and tilts controlling the outer one, which changes the pitch of the blades

scissors link

connected to the mast in turn drives the outer rotating swashplate

Pitch Links / Push Pull Tubes

Connect to both the rotating swashplate and the stabilizer bar, or directly to the pitch horn. are the mechanical linkage that translates pilot input to control the blades' pitch.

tail boom

structural component of the helicopter that supports the tail rotor and in some cases the directional fins

In a ____, a ducted fan is used in place of a traditional tail rotor to cancel out torque effect or the counter-rotating force applied to the airframe as a main rotor system turns

NOTAR

Cowlings

Removable pieces of an aircraft's outer skin that protect important areas of the aircraft from aerodynamic and environmental forces

Skids

type of landing gear on a rotary wing aircraft that allows it to land safely without damaging the undercarriage. most often made of tubular steel and run parallel to the carriage.

Hovering flight

balance of the four aerodynamic forces-- weight, lift, thrust, and drag

rotary wing creates lift via rotational movement of its ____.

airfoils

Magnus effect

as the rotor blades turn, the slow moving high pressure air below the blades pushes up against the fast moving low pressure air above the blades

Induced Flow (Downwash)

column of air passing through the rotor blades

Translating tendency (drift)

tendency of a rotary wing to drift laterally due to tail rotor thrust.

The ______ is used to counteract torque and creates horizontal thrust necessary to counteract that rotational pull of the airframe, which results in the helicopter drifting laterally

tail rotor of an aircraft

Gyroscopic Precession

when a force is applied to a rotating rotor, the force will be felt 90 degrees later in the plane of rotation.

Transverse Flow Effect

when a helicopter begins to accelerate, the induced flow created by the lifting action of the rotor blades drops to nearly zero in the front half of the rotor system and increases in the rear half of the rotor system. This drop in induced flow causes the AOA in the front half of the rotor system to increase, causing the blades to flap up. In contrast, as the induced flow increases in the rear haf of the rotor system, the AOA decreases causing the blades to flap down. Due to gyroscopic precession, the flapping blades is not felt until 90 degrees later which causes the aircraft to roll laterally

to achieve Effective Translational Lift (ETL)...

efficiency of the main rotor system must be increased. As the forward half of the rotor system becomes more efficient, the blades flap up creating more lift and causing the nose to pitch up and, due to gyroscopic precession, roll laterally

Both ____ and ____ can be counted bu using the cyclic pitch control which can tip the aircraft's plane of rotation

transverse flow effect and translational lift

Dissymmetry of Lift

The unequal lift across the rotor disc that occurs in forward flight due to the difference in airflow over the advancing and retreating blades. As a rotary wing aircraft moves forward through the air, relative wind is created which is the motion of air across the airfoil. More lift created and inclined to roll left

Autorotation

rotor blades are driven by relative wind rather than the powerplant.

In engine failure, the pilot can adjust his or her flight controls to allow the induced flow of air through the rotor system to reverse the aircrafts direction. As gravity pulls the aircraft back to the ground, this induced flow can travel vertically through the rotor system and continue to drive the blades in their plane of rotation, allowing the pilot to maintain full control.

Four primary controls of rotary wing aircraft

cyclic control system, collective control, directional control, throttle control

Cyclic Control System

mounted on the flight deck floor and centered between the pilots legs, is utilized to adjust the aircrafts pitch and roll axes. cyclic controls allow the pilot to manipulate the lift vector up to 360 degrees around the aircraft, allowing it to hover in one location

collective control

located to the left of the pilots seat is used to simultaneously change the pitch of the rotor blades. When raised, the pitch angle of blades increases along with AOA creating more lift. Allows the pilot to perform a level climb. Is pulled up to go up and pushed down to go down

The yaw control of the aircraft is adjusted by the use of the ____ or _____ .

tail rotor pedals or directional controls

directional controls

tail rotor pedals change the pitch of the tail rotor blades, causing a larger or smaller horizontal lifting vector

Throttle Control

modern rotary wing aircraft have computers that manage the throttle once switched to a flight setting. Can be located anywhere but the majority are found on the collective control in the form of an attached twisting grip, very similar to a collar.

four fundamentals of flight

straight and level, turns, climbs, and descents

Straight and level flight

Main maneuver, Wing tips even with horizon, Constant heading and altitude is maintained. weight, lift, thrust, and drag in balance. does not require moving the controls when aircraft is not set to autopilot

turns

ailerons banked towards the direction of the turn. the degree of the bank angle determines how much input and adjustment a pilot must make to restore the airplane or helicopter to level flight. The lift force acts as the same angle as the angle of bank to tilt the aircraft away from the vertical

Steps to perform a turn

1. pilots first move the stick/cyclic to the left for left turns and right for right turns.

2. enough power of pitching up is also added to counteract the loss of lift.

3. the controls are neutralized to stop any increase in the bank angle and to maintain the desired bank angle

4. after the turn is accomplished, the ailerons are leveled to resume flight

typically ___ and ___ decrease in turns. The ____ are used to hold altitude and the ____ is used to increase speed.

altitude and airspeed. elevators and throttle

As airspeed and altitude decrease, a stall and loss of lift on the wings may result, the pilot must lower the ____ by one of several means to apply power

AOA

Shallow Turn

bank of less than 20 degrees

Medium Turn

bank roughly 20-45 degrees

Steep Turns

any bank greater than 45 degrees, must input opposite pressure on the controls to return the aircraft to level flight

Climb

when an aircraft flight path changes from a lower to a higher level of altitude. must increase lift to overcome aircraft's weight.

Normal Climb

cruise climb; performed within aircraft manufacturer's standards. aircraft increases airspeed but may not be operating at its optimum performance.

Best Rate of Climb

gaining the most altitude in a given amount of time using the most power available

Best angle of climb

gaining the most altitude over a given distance, used especially at airports

descent

when lift is decreased, induced drag is minimized and the aircraft has a tendency to gain airspeed and thrust. Engine power levels must be reduced to maintain airspeed and avoid an excess speed situation

Partial Power Descent

descent at 500 fpm

Descent at Minimum Safe Airspeed (MSA)

Nose-high controlled descent used to clear obstacles on short approach to a short runway. angle is steeper than during partial power descent

Emergency Descent

when aircraft rapidly loses altitude

glide

descent with little to no engine power, gravity naturally takes over

altimeter

instrument displaying the altitude of a helicopter, computes it by measuring the atmospheric pressure at the aircraft's current altitude and comparing this to a present value. (Air pressure decreases 1 inch of mercury for each 1,000 ft of altitude. three types (three pointer, counter drum, and encoding)

Three Pointer Altimeter

longest hand displays altitude in tens of thousands of feed. medium hand displays hundreds of feet. Box displays set ground atmospheric pressure

Counter Drum Altimeter

Digitally displays the altitude without needing manual figuring.

Also displays set ground atmospheric pressure

Encoding Altimeter

converts the altitude into a digital code, which is then relayed to ground control radar via a transponder

Indicated Altitude

Altitude read directly from the altimeter.

True Altitude

Actual height above mean sea level (MSL)