Aero 1

Question 1

Standard Lapse Rate

Answer 1

2°C per 1000 feet.

Question 2

Static Pressure

Answer 2

Result of the weight of the column of air supported above that elevation. (S=p/p0)

Question 3

Density

Answer 3

Mass of air per unit volume

Sigma = p/p0

Question 4

What affects density?

Answer 4

Pressure and Temperature

Question 5

Humidity Corrections

Answer 5

10% Rule: For every 10% of relative humidity add 100 feet to your density altitude.

40% Rule Same as 10% rule, but subtract 40% RH to apply. (don’t go negative)

Question 6

Name three varying components of the atmosphere

Answer 6

*Pressure
*Density
*Temperature

Question 7

What components of the atmosphere are constant

Answer 7

*78% N2
*21%O2
*1% Other

Question 8

Ideal Gas Law

Answer 8

P = pRT

Question 9

Continuity Principle

Answer 9

A1V1 = A2V2

As area is decreased, velocity will increase

Question 10

Bernoulli Equation

Answer 10

PTotal = Ps + ½ p V

T = PE + KE

Question 11

Stagnation Point

Answer 11

Point on an airfoil when velocity of an air particle reaches zero

Front of leading edge and end of tip (vortices come together)

Question 12

Airspeed Conversion

Answer 12

Indicated –> Calibrated –> Equivalent –> True

Indicated –> Calibrated via NATOPS
Calibrated –> Equivalent via compression correction (N/A)
Calibrated –> True via Rule of thumb (add 2% for every 1000’ PA)

Question 13

Error Sources for Airspeed

Answer 13

*Calibrated A/S - Position/Location; Installation; Downwash

*Equivalent A/S - Compressibility

*True A/S - DA/Air density

Question 14

Lift

Answer 14

Lift is the force perpendicular to the Relative Wind

Question 15

Drag

Answer 15

Drag is the force parallel to the Relative Wind.

Question 16

Generation of Lift

Answer 16

Lift results from a change in STATIC PRESSURE relative to the airfoil

Lower pressure on top leads to higher velocity, higher static pressure on the bottom causes force to lift airfoil

Question 17

3 types of Drag

Answer 17

*Induced - air swirling over the airfoil
*Parasitic - air curling around itself on back of airfoil
*Profile - other things on aircraft (stores, gear, etc)

Question 18

Chordline

Answer 18

Imaginary line moving through the middle of the airfoil

Question 19

Camber

Answer 19

Measure of the chord from the chordline to top of airfoil

Question 20

AOA

Answer 20

Angle between chordline and realitve wind

Question 21

Blade Pitch

Answer 21

Angle between chordline and horizon

Question 22

Induced Velocity

Answer 22

Vertical component of relative wind

Question 23

Rotational velocity

Answer 23

Horizontal component of relative wind

Question 24

Induced drag

Answer 24

Force pushing Lift vector away from perpendicular to the horizon; equal to induced velocity

Question 25

Profile drag

Answer 25

Parallel to horizon

Question 26

Total Aero Forces

Answer 26

Summation of Lift Vector and Profile Drag

Question 27

Relationship of Induced Velocity to AOA and Lift

Answer 27

Inversely related IV increases... AOA decreases, Lift decreases, IV decreases, AOA increases, Lift increases

Question 28

Types of Airfoils

Answer 28

Symmetry - no lift at 0 AOA Non-symmetric - some lift at 0 AOA (cambered); creates a pitching moment

Question 29

Factors that affect Lift and Drag

Question 30

Degrees of freedom for a helicopter blade

Answer 30

*Feathering - physically changing the pitch of the blade (either via design or control inputs) *Flapping - as velocity increases at the blade tip, lift is increased causing blade to flap up *Lead-Lag - allows blade to move horizontally within plane as a flapping blade wants to spin faster due to centrifugal force

Question 31

Blowback

Answer 31

Blowback is the separation of the Virtual Axis (Tip Path Plane) from the Control Axis (Swashplate). (Shaft axis is aligned with rotor shaft) As airspeed is increased, the lead blade wants to flap up, causing the blade to blow back even though the controls are still pushing forward. The Virtual Axis blows back and requires more forward cyclic to overcome.

Question 32

How to obtain more ideal lift distribution over the rotor blades

Answer 32

*Geometric Twist - Change angle of twist (Rotor blade is twisted to maximize performance in all flight regimes) *Aerodynamic Twist -1. Change Shape of Airfoil - Blade root is thicker than blade tip 2. Taper *Dynamic Twist -1. Swept tip blades - Change angles of incidence -2. Alters dynamic stall characteristics -3. Higher AVERAGE lift around rotor disk

Question 33

Precession

Answer 33

Maximum displacement occurs 90 degrees after force introduction Fastest speed at 3 o'clock position flaps up at 12 o'clock position

Question 34

Rotor Head types

Answer 34

*Teetering - Has feathering and teetering hinge for flapping (no lead-lag) *Articulated - has hinges for all 3 axis of travel *Bearingless - no hinges; requires more flexible materials

Question 35

LTA vs LTE

Answer 35

* Loss of TR Authority (LTA) - Power Issue -Pr > Pa -TR thrust required > TR thrust available * Loss of TR Effectiveness (LTE) - Wind Issue

Question 36

Aerodynamics of LTA

Answer 36

POWER = TORQUE X RPM Tail Rotor Thrust balances Main Rotor Torque, so as RPM decreases, -TR must produce more thrust -(must increase tail rotor pitch).

Question 37

Aircraft reaction to loss of TR thrust

Answer 37

Loss of TR Anti-Torque *Fuselage Rotates toward Advancing Blade Side * Right Rotation – (CCW U.S. Helo’s) * Accelerated rotation response * Pilot Response - Lower Collective to reduce Torque on MR * Less Anti-Torque requirement since less Q on MR

Question 38

Aircraft reaction to loss of engine power

Answer 38

* Initial tendency is to yaw LEFT (CCW rotor) -This is an instantaneous response *The sudden removal of power cancels the need for anti-torque -Therefore, the left pedal applied must be removed

Question 39

TR Design types

Answer 39

*Pusher - A few Percentages (1-5%) More efficient than puller * Puller - Design accepts the reduced efficiency (Canted provides 2.5% of total lift) * Fenestron (within tail pylon) - Even more efficient (minimizes tip loss)