Introduction to Aerospace – Historical Perspective

Dr. Doug Cairns

2-14

For the Next Few Slides

• Basic Physics of Flight• What’s happening during a flight• Rule of Thumb airplane design

2-15

Basic Forces

Lift

Weight

Drag

Thrust

Trim

2-16

What’s in Weight?Lift

Weight

Drag

Thrust

TrimPayload

Fuel

AirplaneOperating

EmptyWeight (OEW)

Reserves

Operating items

Systems

Propulsion

Landing Gear

Body

Wing & Tails

Food, Supplies

Navigate, control and support life

Generate force to move airplane

Support airplane on the ground

Enclose the payload

Provide lift

Paying Passengers and Cargo

2-17

Weight changes during the flight.

Payload

Fuel

ReservesOperating items

Systems

Propulsion

Landing Gear

Body

Wing & Tails

Food, Supplies

Navigate, control & support life

Generate force to move airplane

Support airplane on the ground

Enclose the payload

Provide lift

PayloadFuel

Operating empty weight

End of flight Start of Flight

Burn off fuel

2-18

Lift

Weight

Drag

Thrust

Trim

How do you make Lift?

Bernoulli:

“The faster the air flows over the surface, the lower the pressure air exerts on the surface.”

2-19

How to Change Lift• Since Lift is about the same as weight and

weight changes, then must be able to change lift.– Increase lift by

• increasing the tilt of the wing• increasing the speed of the airplane (actually

speed squared)• decreasing the altitude of the airplane above the

ground.

2-20

But there are Limits to Lift

Lift

Airfoil Tilt Angle

“Stall”The flow no longer can stay attached to the upper surface.

2-21

Ways around the Limits to Lift

Lift

Airfoil Tilt Angle

“Slats”

“Slats & Flaps”

2-22

Wings are made up of airfoils

AirfoilWing

2-23

Lift

Weight

Drag

Thrust

Trim

• A propeller produces thrust like a wing produces lift except:• The propeller is a wing rotated 90 degrees• The speed over the airfoil comes from

rotating the prop.

How to create Thrust

2-24

How does a jet engine produce thrust?

Propeller (“compressors”)

Propeller (“turbines”)

Fuel Burned(Generates high speed air) Thrust

A jet engine “sucks, squeezes, burns and blows.”

2-25

What is “Drag”? Lift

Weight

Drag

Thrust

Trim

Skin Friction

Excrescence

Induced

“Pressure”

Lift and Span

Aerodynamic details

Smoothness

Outside surface area

Due to the influence of an airfoil on those outboard of it

Due to the rapid growth of the boundary layer

Due to roughness, gaps & antennas

Due to the friction in the boundary layer next to the skin to the air flowing over the skin.

2-26

What & Why Trim?Lift

Weight

Drag

Thrust

Trim

• Trim comes from a wing like surface mounted on the back of the airplane

• To change the tilt of the airplane– increase down load - airplane nose goes up– decrease down load - airplane nose goes down

2-27

Airplane Controls

Flaps

Spoilers

AileronRudder

Elevators

Slats

Fin

Stabilizer (Tail)

2-28

Airplane Stability

Lift

Weight

A stable system A stable airplane

Move the ball away from the bottom and it returns to the bottomBecause ball’s center of gravity is above the bottom of the bucket

Move the nose of the airplane up and the airplane’s nose will come back down.Because airplane’s center of lift is aft of the center of weight

2-29

How does an airplane turn?It banks.

Lift

Weight

2-30

Why do airplanes have rudders?

To balance an inoperative engine and crosswinds.

2-31

Design Envelope

Takeoff and Landing Distances

Fatigue

Brake Capability

Engine out takeoff

Stall Margins Pressurization

Speed margins

System redundancy

Flutter

Situation Awareness

Structural Strength margins

The Plane that Taught America to Fly

Note: Dr. Cairns has around 100 hrs in this make and type, over 200 hours in similar type aircraft

We will have an opportunity to crawl around one of These!

The Greatest Fighter Aircraft Ever(according to the Military Channel)

The Funny Looking X29(forward swept wing for better maneuverability)