Army Aviation Flashcards
What do all turbine helicopters have that only some Piston helicopters have?
Governor
Where is the horizontal reference datum located?
It varies with each manufacturer
The _______ position relative to the horizon determines the helicopter’s direction travel and attitude.
Cyclic
What entry speed should helicopters initially start with when training for rapid deceleration?
45 knots
What helicopter has has been the Army’s primary training system since 1993?
Bell TH-67
What occurs when the tail rotor becomes more aerodynamically efficient during the transition from hover to flight?
Translational thrust
What is the solidity ratio?
The ratio of the total rotor blade area to the total rotor disk area
What are the four controls used by a helicopter pilot during flight?
- Collective pitch
- Throttle
- Cyclic Pitch
- Anti-torque pedals
What does each gallon of reciprocating engine oil weigh?
7.5 lbs
What percent must the pilot increase rotor thrust / engine power by to maintain airspeed in a 2G/60* turn?
100%
At what altitude AGL should a high reconnaissance be flown?
300-500 ft AGL
What twin engine, tandem rotor helicopter became prominent in the Vietnam War and is still currently in use?
CH-47 Chinook
What changes the angle of incidence (AOA) differentially around rotor system?
Cyclic feathering
What describes the relationship between internal fluid pressure and fluid velocity?
Bernoulli’s Principle
What power setting should be used during terminations to a hover?
100% of Maximum
During the approach to a pinnacle, how fast should the rate of closure appear?
As fast as the pace of a brisk walk
What are the four types of drag?
- Profile
- Induced
- Parasite
- Total
What army helicopter is the lightest (has lowest empty weight)?
The OH-58A Kiowa has the lowest empty weight: 1583 lbs
When at a hover, what’s it called when a single main rotor helicopter tends to move in the direction of tail rotor?
Translating tendency
What changes a helicopter’s AOA?
Cyclic pitch
When is a forward CG not obvious?
When hovering at a strong headwind
What term has the same meaning as load factor?
Effective weight
On most helicopters, what does the torque do during left turns?
Increases
What does the torque do during right turns?
Decreases
During application of aft cyclic, what does the torque and rotor speed do?
Torque speed decreases
Rotor speed increases
During application of forward cyclic, what does the torque and rotor speed do?
Torque increases
Rotor speed decreases
What kind of approach flight path should be taken when climbing to a ridge line?
Parallel to the ridge line and into the wind.
What is the US Army’s primary light utility helicopter?
UH-72 Lakota
What law of physics is referred to as the Law of Conservation of Angular Momentum?
The Coriolis Effect
What does the Coriolis Effect state?
That the value of angular momentum of a rotating body doesn’t change unless an external force is applied.
What control mechanism is located to the left of the pilots seat?
Collective Pitch Control
What is one required action of the pilot while entering a climb maintaining airspeed?
Increase the collective and throttle
Also adjust the pedals as necessary to maintain a centered ball in the slip/skid indicator
Approximately how many degrees of an approach angle is considered a steep approach?
13-15 degrees
What US Army helicopter is an attack platform that features four hard points on stub wing pylons, and usually carries a combination of AGM-114 Hellfire missiles and Hydra 70 rocket pods?
AH-64 Apache
What factors can make it unsafe to to take off operating at max gross weight?
High altitude
High temperatures
High Humidity conditions
In a standard airplane traffic pattern, which of the five legs is known as the crosswind leg?
The second leg
What is the normal maximum slope for slope landings?
5 degrees
What is US Army helicopter has the highest maximum speed?
CH-47 Chinook
170 knots
In what speed range does the helicopter experience Effective translational lift ETL when transitioning to forward flight?
16-24 knots
What controls the direction in which the nose of the helicopter points.
Anti-torque pedals
How much does a gallon of JP-8 fuel weigh?
6.5 lbs
A hover taxi is used when operating how many feet AGL?
25 ft
During a steep approach, below how many feet AGL should the anti-torque pedals be adjusted to align the helicopter with the intended touchdown point?
100 ft
What is the primary function for the OH-58 Kiowa?
Armed reconnaissance in support of ground troops
The main forces acting on a helicopter are:
Lift
Weight
Thrust
Drag
What is the forward force produced by the power plant / propeller or rotor?
Thrust
What is the rearward, retarding force caused by the disruption of airflow you the wing, rotor, fuselage and other protruding objects?
Drag
What is the combined load of the aircraft itself, the crew, the fuel and the cargo or baggage?
Weight
What opposes the downward force of weight and is produced by the dynamic effect of the air acting on the airfoil?
Lift
What is Newton’s Third Law of Motion?
For every action there is an equal and opposite reaction
Above how many degrees of bank does the apparent increase of weight skyrocket?
30 degrees
How is profile drag developed?
From the frictional resistance of the rotor blades passing through the air.
How is induced drag generated?
By the airflow circulation around the rotor blade as it creates lift.
What is the main cause of drag at lower speeds?
Induced drag
What kind of drag is present any time the aircraft is moving though the air, increasing with airspeed?
Parasite drag
What is the total drag?
The sum of all three types of drag
Parasite
Induced
Profile
The low point on the total drag curve that shows airspeed at which drag is minimized is called what?
L/D Max
Lift to Drag ratio is greatest at this point
Any surface producing more lift than drag when passing through The air at a suitable angle is called what?
An Airfoil
The length of the rotor blade from the the center of rotation to tip of the blade is called
Blade span
A straight line intersecting leading and trailing edges of the airfoil is called
Chord line
The length of the chord line from the leading edge to trailing edge is called
Chord
It is the characteristic longitude like dimension of the airfoil section
A line drawn halfway in between the upper and lower surfaces of the airfoil is called
Mean camber line
What’s the front edge of an airfoil?
The Leading edge
What’s the name of the speed and direction of the airfoil passing through the air?
Flightpath velocity
What is defined as the airflow relative to an airfoil and is created by movement of an airfoil through the air?
Relative wind
The rearmost edge of an airfoil is
Trailing edge
The downward flow of air through the rotor disk is
Induced Flow
Relative wind modified by induced flow is
Resultant relative wind
The angle measured between the resultant relative wind and chord line is called
Angle of Attack (AOA)
The angle between the chord line of the blade and the rotor hub is called
Angle of Incidence (AOI)
Or
Blade Pitch Angle
The point along the chord line of an airfoil through which all aerodynamic forces are considered to act is called
Center of Pressure
The center point and attaching point on the last for the root of a blade is called
Hub
The farthest out board section of the rotor blade is called
Tip
The point that attaches to the hub which is also the inboard end of a blade is called
Root
The change in blade incidence from the root to the outer blade is called
Twist
What direction does relative wind move in relation to airfoil
In a parallel but opposite direction to movement of the airfoil
What do rotor blades produce as they turn about the mast
Rotational Relative Wind
The increased efficiency of the rotor system caused by interference of the airflow (this is due to the fact that the air pressure or density is increased, which acts to decrease the downward velocity of air) when near the ground is called
Ground Effect
Or aircraft is In Ground Effect [IGE]
As power applied changes what also changes
Torque created
Since he Fuselage of the helicopter, with a single main rotor, is suspended from a single point and has considerable Mass, it is free to oscillate like a pendulum. What’s this called?
Pendular action
As the lift on the blades is increases (In a takeoff for example) two major forces are acting at the same time - centrifugal force acting outward and lift acting upward… What does this cause in the blades?
Coning
What does the Coriolis effect state?
The value of angular momentum of a rotating body does not change unless an external force is applied
Four fundamentals of flight upon which all maneuvers based
Straight and Level Flight
Turns
Climbs
Descents
Normal helicopter landings usually require _____ power settings, with terminations to a hover requiring the _____ setting
High
Highest
A vertical takeoff to a hover involves flying the helicopter from the ground vertically to a skid height of _____ ft, while maintaining a constant heading
2-3
What controls heading, direction of turn, and rate of turn at hover?
Anti torque pedals
What controls hover height, rate of ascent and descent?
Collective
What controls heli position and direction of travel?
Cyclic
______ is the maneuver in which the helicopter is maintained in nearly motionless flight over a reference point at a constant altitude and on a constant heading
Hovering
A ______ _______ is a maneuver performed at hovering altitude in which the nose of the helicopter is rotated either left or right while maintaining position over a reference point on the surface
Hovering turn
__________is normally used to move a helicopter to a specific location, and it may begin from a stationary hover
Forward hovering flight
________ May be necessary to move the helicopter to a specific area when conditions make it impossible to use forward flight.
Sideward hovering flight
__________ May be necessary to move the helicopter to a specific area when the situation is such that forward or side ward hovering flight cannot be used.
Rearward hovering flight
________ refers to operations on or near the surface of taxiways or other prescribed routes
Taxiing
What are the three types of taxiing?
Hover taxi
Air taxi
Surface taxi
A hover taxi is used when operating below _______ above ground level (AGL)
25 feet
During any hovering maneuver __________ should be maintained
Constant groundspeed, altitude, and heading
_________ Is preferred when movements require greater distances within an airport or heliport boundary
Air taxi
_________ Is used to minimize the effects of rotor downwash
Surface taxi
_________ Is an orderly transition to forward flight and is executed to increase altitude safely and expeditiously
A normal take off from A hover
Is used to move the helicopter from a position on the surface into effective translational lift in a normal climb using a minimum amount of power
A normal take off from the surface
This technique provides the most favorable visibility conditions and reduces the possibility of debris being ingested by the engine
If the take off is made during cross wind conditions the Helicoper is flown in a ______ during the early stages of the maneuver
Slip
If a take off is made during cross wind conditions after approximately _______ ft of altitude is gained, make a coordinated turn into the wind to maintain the desired ground track
50
______ is flight and which constant altitude and heading are maintained
Straight and level flight
A ______ is a maneuver used to change the heading of the helicopter
Turn
A _____ occurs when the helicopter slide sideways toward the center of the turn
Slip
If you hold improper antitorque pedal pressure, which keeps the nose from following the turn, the helicopter _______ sideways toward the center of the turn
Slips
A ______ occurs when the helicopter Slidez sideways away from the center of the turn
Skid
A ______ is caused by too much antitorque pedal pressure in the direction of the turn, or by two little in the direction opposite the turn in relation to the amount of power used
Skid
A ______ occurs when the rate of turn is too great for the amount of bank being used, and a _______ occurs when the rate of turn is too low for the amount of bank being used
Skid
Slip
A helicopter is
A type of rotorcraft
Helicopter turbine engines produce _____ thrust per pound then piston engines
More
Helicopters typically have between blank and blank main rotor blades
2, 6
Depending on the type of helicopter, main rotor system components can include
Stabilizer bar, upper and lower swashplate's, counterweights, pitch horns, Teeter or coning hinges, blade grips, pitch and scissor links, control rods
What is the function of the fly bar
To decrease crosswind thrust on the blades and enhance flight stability by keeping the bar stable as the rotor spends
Many helicopters have a horizontal stabilizer located where
On the tailboom
What is the purpose of the tail rotor
To produce an antitorque force acting perpendicular to the helicopters longitudinal axis
Wheels on blank types of helicopters are blank
Some, retractable
From a physics perspective, the blank force is deemed to act through a helicopters blank
Total weight, center of gravity
When a pilot banks a helicopter, causing it to turn, what happens to the machines weight
It increases
In the case of helicopters, lift is produced by blank moving through the air at a speed sufficient to create blank
Airfoils , a pressure differential
Thrust acts blank to the Aircrafts blank
Parallel, longitudinal axis
Vortices produced by spinning rotor blades create what
Induced drag
When plotted on a graph, L/D Max is the point where the helicopters
Total lift to Drag ratio is the greatest
I Helicopers potential energy is affected by
The Aircrafts height above the ground
Blank all affect the lift produced by spinning rotor blades
Airfoil coefficient of lift,
air density,
blade area
What happens when a helicopters main rotor blades spin rapidly
The upper and lower sides of each blade experience a difference in pressure
Newtons third law of motion applies to helicopters because
The spinning main rotor makes the aircraft try to spin in the opposite direction
When the pilot pushes the cyclic forward
The main rotor disc tilts forward
What unique characteristic do multi engine helicopters have
A throttle lever for each engine
When the pilot once the Helicopers knows to move weft or right he or she
Pushes on the corresponding antitorque pedal
For Helicopers with a main rotor disc that spins counterclockwise, the blank airflow speed happens when each blade reaches the blank position
Maximum, 3 o’clock
On the advancing rotor blade, lift blanks and the blade blanks
Increases,
moves upward
The angle between the blank of a rotor blade and its direction of motion relative to the blank is the angle of attack, which is blank angle
Chord line,
Air,
an aerodynamic
The angle of incidence is between the blank line of each blade and the rotor systems blank
Chord,
plane of rotation
When a helicopter engine blanks, a clutch mechanism called a blank does what
Fails,
freewheeling unit automatically disconnects the engine from the main rotor, allowing it to spin freely
During an auto rotation and forward flight, the rotor disc takes in blank air and the driven, driving, and stall regions of each blade move blank along its length or Span, but only on the blank side of the desk
Upward flowing, outboard, retreating
Where there is too much lift the main rotor blades will do what
Flap
Centrifugal force blank spinning helicopter main rotor blades blank
Pulls
Outward
If left uncorrected, greater lift produced by the advancing side of the rotor disk compared to the lift created by the disks retreating side could make the helicopter what
Uncontrollable
The driven region is blank the blade tips and normally what percent of the radius
Nearest, 30
The blank region is normally between a blades blank and blank regions
Driving, stall, driven
Because of gyroscopic precession, if a wind gust applies a downward force on the left side of the helicopters main rotor disk as it spins clockwise as viewed from above, the movement response occurs at the blank o’clock position
12
Maximum ground effect occurs during a hover up to a height equal to what percent of the main rotors diameter
100
What can a pilot due to worsen a helicopters pendular action
Over control the aircraft
The phenomenon of a helicopter sinking into its own downwash is called what
Settling with power
