1. Aeronautical Engineering for Pilots
( )
Or: how I became a fan of
Isaac Newton
Or: Applied physics for fun and profit

2. F= M*A F= _M_ * Velocity Force equals mass times acceleration second
Newton’s laws of motion are the basis for most of classical aerodynamics, especially the 2nd law
F= M*A
Force equals mass times acceleration
With a little algebra we can rearrange the 2nd law to read:
F= _M_ * Velocity
second

3. Mr. Newton presiding in Trinity Chapel Cambridge, England

4. Throwing Tyranny overboard: Boston Tea Party reenactment
Let’s use Mr. Newton’s laws to analyze the Boston Tea Party
Samuel Adams looks like he’s throwing a tea chest at about 10 MPH. Tea’s light but the chest is mahogany so maybe pounds???
Sammy imparts a horizontal velocity of 10 mph on tea chest in 1 second
Throwing Tyranny overboard: Boston Tea Party reenactment

5. Story Problem # 1 Release Start Dist. Time = 1 sec Time = 0
Velocity = 14.7 FPS Velocity = 0

6. Sammy pushes on boat with the same force as on the tea chest, 14.7 pounds.
(Newton’s third law)

8. Force (Thrust)= 115 # per sec / 32.17 * 976 FPS = 3488 #
Hainan Island
China, 2008
So now let’s apply the same 2nd law to this Learjet Model 36 ER engine but
use air molecules in place of tea chests.
The Garrett TFE 731 “swallows” 115 lb. / second of air molecules at full thrust.
Exhaust velocity at the engine exit has to be higher than the airplane’s top speed
MMO= Kt FPS Exhaust Velocity ~976 FPS
Force (Thrust)= 115 # per sec / * 976 FPS = 3488 #

10. A couple of guys that knew a lot about AIR!
"I am convinced that human flight  is both possible and practical." Wilbur Wright, 1899

11. The Lady that helped them become famous

12. What will humans think of these photos in the year 2519?

13. Airfoil Theory
Wright kite
at Kitty Hawk

14. Equal molecule travel time
Here’s something like the Wright’s airfoils
Distances are equal, top & bottom????

15. Cessna 172:
Gross weight – 2300 Pounds
Span – 36 feet
V best glide ~ Vy – 80 MPH, 69 Kts.
Best L/D α – 4 degrees

16. Cessna 36’ foot span wing flying in streamtube
4 degrees
36 Feet

17. Downwash
Weight Lift α
Relative
Wind

18. α Newton’s 2nd: Force= M /sec * Velocity Drag due to lift
Flight path angle + α
Weight Lift α
Relative
Wind
Downwash
Horizontal

19. At L/D max Parasite drag and induced drag are about equal (windmilling prop)
Total drag = 2 * Induced drag = 2 * 324 pounds = 648 pounds
Required HP = Drag * velocity = 648 lb. * 117 Fps / 550 = 138 Horsepower
Available HP = Engine HP * Propeller efficiency = 160 HP * 85% = 136 HP

20. Aircraft Structures
1952 Northrop F-89 Scorpion Wing Failure

21. FAR’s structural certification standards – Small aircraft
§ Limit and ultimate loads.
The applicant must determine—
(a) The limit loads, which are equal to the structural design loads unless otherwise specified elsewhere in this part; and
(b) The ultimate loads, which are equal to the limit loads multiplied by a 1.5 factor of safety unless otherwise specified elsewhere in this part.
§ Structural strength.
The structure must support:
(a) Limit loads without—
(1) Interference with the safe operation of the airplane; and
(2) Detrimental permanent deformation.
(b) Ultimate loads. (can come back bent)

22. What are moments and what are they used for?
Calculate moments about this point F1 F2
40 Lb. 3’ 6’ 6’
Girl moment = 40 lb. * 6’ = 240 foot – pounds
To balance (moments equal):
F1 = 240 foot – pounds / 6’ = 40 pounds
F2= 240 foot – pounds / 3’ = 80 pounds

23. 4.5’ 2’ 6’
7.5’ F1

24. What is a spar cap and why’s it important?

27. Material Stress Analysis
Wing spar outboard of strut attach, Length = 9.5’
Lift at ½ span from strut attach
Moment
Tip Strut Attach
8 in.

28. 8”=.66’ Compression Tension Moment = 3,339 ft. – lb. Spar Immovable
object

29. Approximate 2024 Aluminum Stress Strain curve
Proportional limit
.002 in. / in.

30. Thank you,
Terry Spath