Oral Exam Guide Flashcards
What kind of helicopter can you fly with a Prvt Pilot rating?
Any helicopter up to 12,500 lbs, except the R-22 and R-44 unless SFAR 73 is followed.
Can you fly a twin powered turbine powered helicopter?
Yes
What types of charts are available for use in helicopter VFR navigation?
WAC- World Aeronautical Charts
Sectionals
Terminals
Helicopter Route Charts
How low can a helicopter pilot fly?
Helicopters may be operated a less than the minimum prescribed in paragraph (b) or (c) of this section if the operation is conducted without hazard to the persons or property on the surface. Shall also comply with any routes or altitudes specifically prescribed for helicopters by the FAA.
When flying into an airport environment, what rules apply to helicopters?
Each pilot of a helicopter must avoid the flow of fixed-wing aircraft.
What are the VFR weather minimums for Class G airspace below 1,200 feet AGL?
A helicopter may be operated clear of clouds if operated at a speed that allows the pilot adequate opportunity to see any air traffic or obstructions in time to avoid a collision.
What is required for a helicopter pilot to request a “Special VFR” at a controlled airport?
You need ATC clearance & to remain “clear of clouds”
What are the fuel requirements for helicopters under VFR flight rules?
No person may begin a flight in a rotorcraft under VFR conditions unless (considering wind and forecasted weather) there is enough fuel to fly to the first point intended landing and assuming normal cruising speed, to fly after that for at least 20 minutes.
What is the center of pressure?
An imaginary point on the chord line where the resultants of all aerodynamic forces are considered to be concentrated.
What do the blades do to compensate for asymmetrical lift?
Flap, feather, lead and lag.
What is the axis of rotation?
An imaginary line about which the rotor rotates.
What is the rotor tip path?
It’s the imaginary circular plane outlined by the rotor blade tips as they make a cycle of rotation.
What is the blade pitch angle?
Angle between the blade’s chord line and the reference plane containing the rotor hub.
What does the collective pitch do?
Changes each rotor blade an equal amount of pitch no matter where it is located in the plane of rotation.
What does the cyclic do?
Changes the pitch of each blade as a function of where it is in the plane of rotation.
What is Newton’s Third Law?
For every action there is an equal and opposite reaction.
Why does the helicopter drift in the same direction as the anti-torque rotor thrust?
Because of translating tendency.
What is translating tendency?
The tendency of the helicopter to drift in the same direction as the Anti-torque rotor…design features are incorporated in the helicopter counteract this tendency. One is tilting the rotor mast opposite the drift, another is a “bias” in the cyclic control mechanism.
What is pendular action?
When a helicopter oscillates either longitudinally or laterally in the same way as a pendulum. This can be exaggerated by over controlling.
What is coning?
The result of lift and centrifugal force that causes the blades assume a conical path instead of remaining in the plane perpendicular to the mast.
What is the Coriolis Effect?
When a rotor blades flaps upward, the center of mass of that blade moves closer to the axis of rotation and blade acceleration takes place in order to conserve angular momentum.
What is ground effect?
Ground effect usually occurs less than one rotor diameter above the surface. As the induced airflow through the rotor disc is reduced by the surface friction, the lift vector increases. This allows a lower rotor blade angle for the same amount of lift, which reduces induced drag.
What is blade flapping?
Blade flapping is the ability of the rotor blade to move up, or down, in a vertical direction. Lift acting upward and parallel to the mast, causes the blades to flap upwards. Blades may flap independently or in unison to help compensate for dissymmetry of lift.
What is dissymmetry of lift?
The relative wind encountered by the advancing blade is increased by the forward speed of the helicopter, while the relative wind speed on the retreating blade is reduced by the helicopters forward airspeed. Because of this difference in relative airspeed, the advancing blade side of the rotor disc produces more lift than the retreating blade side.
What is low RPM blade stall?
When the pilot allows the engine RPM to get too to effectively maintain the rotor RPMs which causes the blades to stall (by adding collective with low engine RPMs). This results in a likely fatal crash due to “Blow-back” or falling at an extreme rate.
What is effective translational lift (ETL)?
The additional lift obtained when entering forward flight, due to the increased efficiency of the rotor system. As the helicopter accelerates, the helicopter moves out of its vortices and is in relatively undisturbed air. Airflow also becomes more horizontal which reduces induced flow and drag with a corresponding increase in angle of attack and lift.
What is transverse flow effect?
As the helicopter accelerates in forward flight, induced flow drops to near zero at the forward disc area and increases at the aft disc area. This increases the angle of attack at the the front disc area causing the rotor blade to flap, and reduces angle of attack at the aft disc area causing the rotor blade to flap down. The result is tendency for the helicopter to roll slightly to the right as it accelerates through approximately 20-kts or if the headwind is approximately 20-kts.
Explain gyroscopic precession?
The spinning main rotor of a helicopter acts like a gyroscope. As such, it has properties of gyroscopic action, one of which is procession. Procession happens when you apply a force to one side of a spinning disk-that force gets transferred 90 degrees ahead of where it was applied, in the same direction of rotation.
What is the “Arm” in regards to W&B?
The horizontal distance from the datum to any component of the helicopter or to any object located within the helicopter.
Define Basic Empty Weight.
It’s the starting point for weight computations, which is the weight of the standard helicopter plus optional equipment, unusable fuel, and full operating fluids (including engine oil)
Define Maximum Gross Weight?
This is the maximum weight of the helicopter. Most have both an internal MGW and an external MGW (which refers to internal and external loads).
What performance characteristics will be adversely affected when a helicopter is overloaded?
Longer take run. Reduced rate and angle of climb. Reduced service ceiling. Reduced cruising speed. Shortened cruising range. Decreased maneuverability. Longer landing run (higher landing speed) Excessive loads on the structure (especially landing skids)
If the helicopter is over weight when could structural deformation occur?
Excessive load factors
Strong wind gusts.
Turbulence.
What characteristics will be adversely affected when a helicopter is underloaded?
Primarily it could affect flight in autorotations as the lack of weight may cause the rotor RPMs to not reach a desirable RPM during the procedure. Forward ballast should be used to compensate for this during single pilot operations.
What effect does a forward CG have on the helicopter flight characteristics?
There may not be enough cyclic authority to allow the helicopter to flare for a landing and it will consequently require an excessive landing distance.
What effect does a rearward CG have on helicopter flight characteristics?
There may not be enough cyclic power to prevent the tail boom from striking the ground. If gusty winds should cause the helicopter to pitch up during high-speed flight, there might not be enough forward cyclic control to lower the nose.
What is a retreating blade stall?
To generate the same amount of lift across the rotor disc, the advancing blade flaps up while the retreating blade flaps down. This cause the angle of attack to decrease on the advancing blade (reducing lift) and increase on the retreating blade (increasing lift). As the forward airspeed increases, at some point the low blade speed on the retreating blade, together with it’s high angle of attack causes it too stall.
How does retreating blade stall affect the helicopter performance?
It’s the major limiting factor in top speed (Vne).
What conditions are conducive to retreating blade stall?
at high forward air-seeds, the following are all conducive to RBS: High Weight Low rotor RPM High Density Altitude Turbulence Steep, abrupt turns
What is the height/velocity diagram?
H/V diagram is published by the manufacturer of each helicopter model and it depicts the critical combinations of airspeed and altitude should an engine failure occur.
Why is an H/V diagram important?
Because is depicts the height/speed combinations in which you should operate the helicopter within to ensure a favorable outcome should an engine loss occur.
Why is there a lower shaded area of a H/V diagram?
Because you might be going too fast to safely recognize and autorotate should an engine failure occur.
What factors affect the performance of an aircraft during take-offs and landings?
Air Density (Density Altitude)
Surface Winds
Weight
Surface conditions (pavement, water, grass, snow etc.)
*WASS
How does air density affect the helicopter performance?
Efficiency of the rotor blades (as an airfoil)
Power output of the engine
Drag produced by increased AOA
Reduced amount of lift from rotor blades.
Reduced tail rotor efficiency.
