L3 - Tail and Tail Sizing

Question 1

What are the pros of a conventional tail?

Answer 1

+ Roots attached directly to fuselage

+ High VT effectiveness due to interference increasing effective aspect ratio

Question 2

What are the pros and cons of a T tail?

Answer 2

+ HT away from engine exhaust
+ Rudder unblanketed at post stall AOA
- Increased weight
- Deep stall

Question 3

How can you prevent deep stall?

Answer 3

Elevator down spring

Dorsal Fins

Question 4

What are the pros and cons of a Cruciform tail?

Answer 4

+ less weight than T-tail
+ Out of engine wake
- Heavier than convetional tail
- Higher interference drag

Question 5

What are the pros and cons of a V tail?

Answer 5

+ Combines functions
+ Less surfaces (less interference drag)
- Interaction of rudder and elevator control forces
- Increased load

Question 6

What are the pros and cons of a Y tail?

Answer 6

+ Improved directional stability over V tail

- Challenge when rotating on takeoff

Question 7

What are the pros and cons of a H tail?

Answer 7

+ Reduced height
+ Redundancy (hence on A10 warthog)
- Increased weight

Question 8

What does a dorsal fin do?

Answer 8

Reduces rudder lock and increases Yaw moment.

Question 9

What does a ventral fin do?

Answer 9

Improves stall characteristics and reduces dutch roll.

Question 10

What is dutch roll?

Answer 10

An osciallatory motion that looks like tail wagging. Is the result of strong lateral stability and weak directional stability.