ARRANGEMENT OF THE ARRANGEMENT OF THE EMPENNAGEEMPENNAGE

Requirements:Requirements:

A. Slipstream / Jetstream EffectsA. Slipstream / Jetstream EffectsA1. The empennage must never be in the jet efflux of the engines A1. The empennage must never be in the jet efflux of the engines

(must be outside cone w. 6 deg. semi-apex angle).(must be outside cone w. 6 deg. semi-apex angle).

Solutions:Solutions:

A1.1 A1.1 Divert the centerline of the jet.Divert the centerline of the jet.

A1.2 A1.2 Horizontal stabilizer dihedral.Horizontal stabilizer dihedral.

A2. The empennage must not be close to a jet efflux because the A2. The empennage must not be close to a jet efflux because the jet pumping effect will affect the direction of the airflow and jet pumping effect will affect the direction of the airflow and diminish the stabilizing effect of the tail.diminish the stabilizing effect of the tail.

A3. The empennage must be as far away as possible from A3. The empennage must be as far away as possible from sources of noise to avoid acoustic fatigue. sources of noise to avoid acoustic fatigue.

ARRANGEMENT OF THE ARRANGEMENT OF THE EMPENNAGEEMPENNAGE

Requirements:Requirements:

B. Stability & ControlB. Stability & ControlA1. The fin and the rudder must provide the counteracting YM in A1. The fin and the rudder must provide the counteracting YM in

case of engine failure.case of engine failure.

A2. The empennage must allow for a safe recovery from stall A2. The empennage must allow for a safe recovery from stall and spin (especially avoid deep stall).and spin (especially avoid deep stall).

ARRANGEMENT OF THE ARRANGEMENT OF THE EMPENNAGEEMPENNAGE

1. Fuselage or Fin-Mounted Stabilizer1. Fuselage or Fin-Mounted Stabilizer

ProsProsStructural simplicity & stiffness.Structural simplicity & stiffness.Having one surface at the tip of the other Having one surface at the tip of the other

increases the ARincreases the AReffeff by about 50% (winglets). by about 50% (winglets).

As a result, the horizontal stabilizer can As a result, the horizontal stabilizer can increase the slope of the fin by about 15%.increase the slope of the fin by about 15%.

ConsConsT-tails may suffer from flutter and deep stall T-tails may suffer from flutter and deep stall

problems.problems.

Cessna 550Cessna 550

BAE-146BAE-146

ARRANGEMENT OF THE ARRANGEMENT OF THE EMPENNAGEEMPENNAGE

2. Twin Vertical Tail2. Twin Vertical TailProsPros Increased effectiveness of the horizontal stabilizer (winglets)Increased effectiveness of the horizontal stabilizer (winglets) If the fin turns out to be too large, rudder deflection will cause If the fin turns out to be too large, rudder deflection will cause

a RM as a result of the large vertical distance of its ac from a RM as a result of the large vertical distance of its ac from the longitudinal axis of the ac. A twin vertical will minimize the longitudinal axis of the ac. A twin vertical will minimize this effect (this effect (F-14,F-14, F-15, F-18F-15, F-18).).

If twin tail booms are used, the twin vertical is the only If twin tail booms are used, the twin vertical is the only solution available (solution available (Cessna SkymasterCessna Skymaster).).

Decreases combat vulnerability (Decreases combat vulnerability (A-10A-10).).

Fairchild Republic T-46AFairchild Republic T-46A

F-14F-14

F-15F-15

F-18 HornetF-18 Hornet

Cessna SkymasterCessna Skymaster

A-10 WarthogA-10 Warthog

ARRANGEMENT OF THE ARRANGEMENT OF THE EMPENNAGEEMPENNAGE

3. Butterfly Tail3. Butterfly TailProsPros Avoids damage to the tail when landing on overgrown Avoids damage to the tail when landing on overgrown

terrain (terrain (sailplanessailplanes).). Keeps tail surfaces clear of the engine efflux.Keeps tail surfaces clear of the engine efflux. Looks cool (Looks cool (V-tail BonanzaV-tail Bonanza)!)!

ConsCons Moving surfaces serve as both rudders (differential Moving surfaces serve as both rudders (differential

deflection) and elevators (simultaneous deflection); deflection) and elevators (simultaneous deflection); complicated control system design.complicated control system design.

Thermik-Excel Vetron Thermik-Excel Vetron SailplaneSailplane

Beechcraft V-Tail BonanzaBeechcraft V-Tail Bonanza