AIRDESLEC MIDTERM - Reviewer

Centroid

Intersection of all hyperplanes that divide an object into two parts of equal moment

Centroid of triangle

Intersection of medians from each vertex to midpoint of opposite side

Centroid formula

(x₁+x₂+x₃)/3 , (y₁+y₂+y₃)/3

Centroid of circle

Center of the circle, also called the radius from the edges

Centroid of combined shape

Sum of individual centroids × areas divided by total area

Center of Gravity

Average location of the weight of an object

Aircraft rotation point

Center of Gravity

Weight distribution

Throughout the airplane

Importance of C.G. in design

Critical for tracking weight and balance

C.G. calculation

Sum of moments divided by total weight

Moment

Weight × location from origin

C.G. envelope

Graph showing how center of gravity varies with gross weight

Approved loading condition

Any weight and C.G. within the envelope

Center of Pressure

Point where aerodynamic pressure acts as a single force vector with no moment; Lift action point

C.G. limits

Specified longitudinally and/or laterally

Forward C.G.

Nose heavy, nose drops when controls are released

Forward C.G. limit

Based on landing characteristics

Forward C.G. risks

Excessive nosewheel loads, nose over, decreased performance, higher stall speeds, higher control forces

Forward C.G. effects

Stable feel, longer takeoff, increased drag, high stall speed due to high AoA

Aft C.G.

Tail heavy, nose rises when controls are released

Aft C.G. limit

Most rearward position for critical maneuvers

Aft C.G. risks

Decreased stability, harder stall/spin recovery, heavy tail needs nose down-force

Aft C.G. effects

Decreased drag, higher airspeed, lower AoA, decreased stability, lift/drag performance impact

Landing gear

Undercarriage of an aircraft used for taxiing, takeoff, and landing; Supports aircraft weight when in contact with land or water; Provides structural support, maneuverability, and absorbs landing loads

Landing gear types

Conventional, Tricycle, Tandem

Conventional gear

Main wheels ahead of center of gravity, small tail wheel

Tricycle gear

Main gear behind center of gravity, nose supported by nose gear

Tandem gear

Two wheel assemblies on centerline, one behind the other

Landing gear choice reasons

Comfortable cockpit access, better forward vision, eliminates ground loop, better braking, reduced takeoff distance, reduced tail damage

7 inches

Propeller ground clearance (nose wheel)

9 inches

Propeller ground clearance (tail wheel)

Wheel track

Distance between outer wheels of main gear

Wheel base

Distance between nose wheel center and line joining main gear centers

Shock absorber

Absorbs and dampens impact energy during landing or taxiing

Landing gear strut types

Rigid Struts, Spring Steel Struts, Bungee Cords, Shock Struts

Rigid struts

Wheels welded to airframe, transfers shock directly

Spring steel struts

Flexible steel/aluminum/composites, flex upward to absorb impact; Simple, lightweight, low maintenance

Bungee cords

Elastic cords on tailwheel/backcountry aircraft, gentle impact transfer

Shock struts

Use nitrogen and hydraulic fluid to absorb landing shock

Shock strut

Two telescoping cylinders, top attached to aircraft, bottom to gear

drag curve or drag polar

relationship between the drag on an aircraft and variables such as lift, coefficient of lift, angle-of-attack, or speed.

polar plot

Drag polar displayed as a graph

Level Flight

means flying at a constant altitude.

Clean Airplane

A configuration where all flight control surfaces set for minimum drag (flaps and gear retracted).

Dirty Airplane

A configuration where landing gear, flaps, and other devices are extended.

Creates drag, but flaps and devices increase lift at lower airspeeds.

Power Required at Minimum Drag

occurs at the speed where parasite drag and induced drag curves intersect.