Master Aero Exam TH73 2026

What does the Collective Pitch Lever Control?

the magnitude of the main rotor thrust

Define the Tip Path Plane (TPP)

plane inscribed by the tips of the rotor blade at a given instant and is often referred to as the rotor disk

Does Rotor Thrust act Perpendicular or Parallel to the TPP?

perpendicular

Moving the cyclic in a direction does what to rotor thrust?

moves the rotor thrust in the same direction

Define Mechanical Axis

extension of the centerline of the rotor mast

Define Control Axis

axis which extends perpendicular to the swashplates. Reflects the position of the control stick

Define Virtual Axis

axis perpendicular to the TPP. Total rotor thrust acts through the virtual axis

As altitude increases, static pressure ______

decreases

As altitude increases, air density ______

decreases

As altitude increases, temperature _____

decreases 2 degrees Celsius for every 1000' up to 36000 (standard lapse rate)

As humidity increases, air density _____

decreases, which increases density altitude

Compute Density Altitude with a given Relative Humidity using the 10% Rule temperature of 6 °C and 2400' PA RH60%

-results in a 2000' DA -Get DA using the charts provided (intersect OAT and PA) use 10% of RH and add it to the DA

for example, is RH is 60%, add 600' to DA -2600' -DA (corrected for RH) = DA (chart) + (100' x RH/10%)

What is Relative Wind?

actual wind the blade element sees

What are the 2 parts of Relative Wind

Linear Velocity and Induced Velocity (the sum of the two is called resultant vector)

On the Blade Element Diagram, Lift is always _____ to Relative Wind

perpendicular

Profile drag is always _____ to relative wind

parallel

Linear Velocity is parallel to what?

TPP

Linear velocity is the vector sum of _____ and _____

rotational velocity and translational velocity

Rotational Velocity is always _____ to the TPP

parallel

Does rotational velocity increase at the root or the tip of the blade?

tip

Induced Flow is perpendicular to _____

TPP

Define Induced Velocity

downward flow of air through the rotor disk

If there is no change in pitch or linear velocity BUT we have an increase in Induced Velocity, what happens to AOA

AOA decreases "induced velocity is the AOA killer"

Define Droop Snoop

symmetrical design with a slight camber in the first 25% of the chord

What does Droop Snoop provide?

minimizes torsional loads and vibrations

allows high rotational velocity and improved stall characteristics

Does a symmetric airfoil provide lift at zero AOA?

Nah dawg

Does a cambered airfoil produce lift at zero AOA?

yeah dawg

What is Pendulum effect and what how does it affect the aircraft's nose?

a pendulum-like moment about the CG

when transitioning from forward flight to a hover the nose pitches up

Is Pendulum Effect more pronounced with a fully articulating system or a semi-rigid rotor system?

semi-rigid

What does the Vertical Fin provide in forward flight?

stability and anti-torque

What does the Vertical Fin provide in a Hover and no-wind?

provides nothing to stability

In what situation would a Vert Fin provide a negative effect?

-when mounted directly opposed to the tail rotor it can block airflow to or from the tail rotor

-In a crosswind or tailwind, the vertical fin gives the helicopter negative stability with respect to yaw

What does a Vertical Fin do in sideward flight?

Weathercock stability

What does the horizontal stabilizer provide?

Gives the helicopter a more level attitude from a hover up to normal cruise speed (Designed with a negative camber)

produces lift vectored downward to provide a pitch-up moment

During Engine Failure in Cruise Flight which way will the nose yaw and why?

Left due to the absence of torque effect

Blowback causes the aircraft to do what?

causes the nose to pitch up with an increase in airspeed

initially occurs at the 3 o clock position, then due to phase lag, the highest upward flapping occurs at the 12

When is induced velocity highest?

in a hover

What type of drag increases with forward airspeed?

parasite drag

what type of drag decreases with forward speed?

induced drag

What type of drag remains relatively the same and slightly increases with forward speed?

profile drag

Where on the power curve is power required the highest?

Hovering and hight forward speed

What does Excess Power allow the pilot to do?

climb, accelerate, maneuver, and take on more weight

What is Max Endurance Airspeed?

achieves max flight time

lowest point on power curve

~60-70 KIAS

"bucket airspeed"

An increase in collective increases _____ and _____

torque and drag

Torque Effect

newtons law. a force applied to an object causes an equal force in opposite direction.

counter-clockwise rotor causes nose to yaw right requiring left pedal

Translating Tendency

to counteract torque effect (right yaw), we have a tail rotor (anti-torque). the thrust from the tail rotor causes a/c to drift right. requiring left cyclic

Loss of Tail Rotor Effectiveness (LTE)

caused by wind interaction with aircraft/tail rotor

may causes uncommanded right yaw

How far off the ground does ground effect persist?

1 rotor disc diameter

In Ground effect induced velocity _____ AOA _____ and Power Required _____

induced velocity decreases

AOA increases

Power Required Decreases

What airspeed does Effective Translational Lift (ETL) occur?

13-24 kts

When does translational tail rotor thrust occur?

when tail rotor becomes more aerodynamically efficient during the transition from hover to forward flight

-tail rotor will work progressively more as airspeed increases

-more anti-torque thrust

-vert fin will provide more anti-torque, leaving more power to the rotor

Dissymmetry of Lift

asymmetric lift from advancing and retreating halves of the rotor disc due to airflow across the entire rotor disc

advancing side sees higher lift than retreating side

main rotor blades flap to equalize lift across rotor blades

What is Phase Lag?

force/input occurs 90 degrees prior to the response

Geometric Imbalance generates _____ per revolution _____ vibration

1 per revolution lateral vibration

What is Transverse Flow Effect and what input is required?

Difference in linear velocity between fore and aft portions of the rotor disc. the aircraft will roll right requiring left cyclic

(T/F) Blowback occurs only in transition to forward flight

FALSE!

What is Geometric Blade Twist?

higher pitch angle at the root

spanwise balancing

What is retreating blade stall?

retreating blades exceed critical AOA and stalls

What will pilot feel during a retreating blade stall?

vibration, pitch up, and roll left

Recover from Vortex Ring State

Vuichard method

"1st step - increase collective"

left pedal, right cyclic

Where is the TAF in relation to the vertical axis for the Driving Region?

forward of the vertical axis

What are 3 phases of Autorotation?

entry

steady-state descent

landing

Primary Factors that affect ROD in an Auto

airspeed

angle of bank

ball control

DA

gross weight

rotor RPM

Will a higher DA increase or decrease ROD in an Auto?

increase

Will a higher gross weight increase or decrease the ROD in an Auto?

decrease!

What combinations does the HV diagram depict?

altitude and airspeed

What affects the knee on the HV diagram

low-inertia

high gross weights

DA

NOT PENDULAR!

How does increasing PA affect VNE?

decreases VNE

Compressibility increases _____ and _____ on the advancing blade

drag, torsional loads

As DA increases Power Available _____

decreases (also remember 4 H's)

An increase in weight causes a _____ in power required

increase

Indications of PREPA (there are 4)

1. uncommanded descent

2. NR decay

3. engine operating at max power limits

4. LTA and uncommanded right yaw

(3) Factors that increase the likelihood of a Dynamic Rollover

1. a rolling moment

2. pivot point other than the helicopter's CG

3. thrust greater than weight

Are wheels or skids more prone to ground resonance?

wheels

In forward flight, lift across the rotor disk is _____ , if not corrected via _____

asymmetrical, flapping

What does the lowest point on the power curve represent?

Max Endurance

Max Rate of Climb

Minimum Power Required Airspeed

Calculate Excess Power

Power Available minus Power Required

What are the effects of Transverse Flow Effect and what airspeed does is typically occur at?

rotor vibration

12-20 kts

Low, Medium, High Frequency Vibrations

low: main rotor track and balance issues

Medium: change in a/c's ability to absorb normal vibrations

High: anything that rotates at or faster than speed of the tail rotor

what is Loss of Tail Rotor Authority (LTA)

occurs when engine torque is greater than the anti-torque capability of the tail rotor

results in uncommanded right yaw

A rotor system consists of:

a mast, hub, and rotor blades

The major types of helicopter designs to counteract torque are:

tandem, coaxial, intermeshing, and tail rotor (conventional)

What are the three primary flight controls?

Cyclic, Collective, Anti-Torque pedals

What is the plane inscribed by the tips of rotor blades at any given instant?

The Tip Plane Path (TPP)

How can one describe Tip Plane Path (TPP)?

The Rotor Thrust acts perpendicular to the tip path plane.

What happens if the cyclic is pushed in any direction?

The rotor tip path tilts the same way the cyclic is pushed.

T/F: The collective changes the pitch angle of all the main rotor blades equally and collectively regardless of their position.

True

_______ describes both magnitude and direction often represented as arrows.

Vectors

Vectors may be added by

placing the tail of one vector on the head of the other and drawing the resultant vector from the tail of the first to the tip of the last.

Atmospheric static pressure decreases with an increase in altitude at a rate of approximately ________________________

1.0 in-Hg per 1000ft

Does atmospheric pressure increase or decrease as the air temperature decreases?

Increases

The standard adiabatic lapse rate is a decrease in air temperature at a rate of approximately ________________________

2°C (3.57°F) per 1000ft up through 36000ft MSL

T/F: As humidity increases, air density decreases.

True

Air density decreases with an increase in ________________

Density Altitude (DA)

To determine Pressure Altitude (PA) for use in calculations, a pilot needs only ________________ into the Altimeter and read the result.

29.92 in-Hg

When station pressure or ambient temperature decreases, an altimeter set at the previous condition will display the same indicated altitude (no change in the altimeter reading), but the true altitude of the aircraft will be

ower. The aircraft is flying lower than indicated. The only

way to minimize this error is to adjust the altimeter setting. The opposite occurs when the station

pressure or temperature rises.

T/F: When station pressure or temperature drops, an altimeter set at the previous condition will read lower than it should.

False

T/F: When station pressure or temperature drops, an altimeter set at the previous condition will read higher than it should.

True

Density Altitude (DA) is the PA corrected for ___________ and ___________ deviations from the standard atmosphere.

temperature ; humidity

What increases as temperature or humidity increase.

Density Altitude (DA)