TYPES OF STABLIZERS SINGLE STABLIZER Conventional tail T-tail Cruciform tail MULTIPLE STABLIZER Twin tail Triple tail V-tail CONVENTIONAL TAIL A Conventional Tail is one with the stabilizer mounted directly on the fuselage and is the usual configuration of an aircraft.
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TYPES OF STABLIZERS
SINGLE STABLIZER
Conventional tail
T-tail
Cruciform tail
MULTIPLE STABLIZER
Twin tail
Triple tail
V-tail
CONVENTIONAL TAIL
A Conventional Tail is one with the stabilizer mounted directly on the fuselage and is the usual
configuration of an aircraft.
ADVANTAGES
Conventional tail has better stall recovery
Conventional tails have advantage in terms of “system redundancy”
Conventional tails can more easily equipped with hydraulic, wire or mechanical systems
It has no single point of failure
Simplest to construct and seem to be most popular.
DISADVANTAGE
The conventional tail has the "elevators" directly behind the wing so it experiences air
disturbance from the wings
Rear mounted engine is not possible in conventional tail
A conventional tail tends to drag the stabilizer through the grass on landing, hooking tips
and causing massive bending loads on the tail boom
T –TAIL
A T-tail is an aircraft tail stabilizer configuration in which the horizontal surfaces (tailplane and
elevators) are mounted to the top of the vertical stabilizer.
ADVANTAGE
T tail will give better rudder authority at very high AOA and stall so as to prevent a spin
T-tail allows high performance aerodynamics and excellent glide ratio
The empennage is not affected by wing slipstream.
At slow speeds, the elevator on a T-tail aircraft must be moved through a larger number
of degrees of travel to raise the nose a given amount than on a conventional-tail aircraft.
DISADVANTAGE
The aircraft will tend to be much more prone to a dangerous deep stall condition.
Unfavorable C.G position if empty.
The control runs to the elevators are more complex, and elevator surfaces are much more
difficult to casually inspect from the ground.
CRUCIFORM TAIL
The cruciform tail is an aircraft empennage configuration which, when viewed from the aircraft's
front or rear, looks much like a cross. The usual arrangement is to have the horizontal stabilizer
intersect the vertical tail somewhere near the middle, and above the top of the fuselage.
ADVANTAGE
The cruciform tail gives the benefit of clearing the aerodynamics of the tail away from
the wake of the engine.
Not requiring the same amount of strengthening of the vertical tail section in comparison
with a T-tail design.
V –TAIL
The V-Tail is where both the fin and stabilizer are replaced with two surfaces mounted in a V-
shape approximately 45 degrees from the horizontal. The control surfaces mounted on a V-Tail
control the aircraft in both pitch and yaw.
ADVANTAGE
The V-tail is lighter, has less wetted surface area.
Two tails would have a lower radar signature than four.
DISADVANTAGE
Using two larger control surfaces instead of four, might actually make the aircraft
heavier.
The bigger hydraulic pumps and cylinders needed to operate the larger surfaces would
add 800 to 900 pounds (360 to 410 kg) of weight to the design.
TYPES OF LANDING GEAR
Conventional Tricycle
CONVENTIONAL LANDING GEAR
Consists of two wheels forward of the aircraft's center of gravity and a third small wheel at the tail. This type of landing gear is most often seen in older general aviation airplanes. The two main wheels are fastened to the fuselage by struts. Without a wheel at the nose of the plane, it easily pitches over if brakes are applied too soon. Because the tailwheel is castered--free to move in any direction--the plane is very difficult to control when landing or taking off.
Two main wheels One tail dragger wheel
ADVANTAGE The ability to operate the aircraft over rough terrain. Due to its smaller size the tailwheel has less parasite drag than a nosewheel. Tailwheels are less expensive to buy and maintain than a nosewheel. If a tailwheel fails on landing, the damage to the aircraft will be minimal. Reduced landing gear weight
DISADVANTAGE Requires more skill in ground taxiing Suffer from poorer forward visibility on the ground. Conventional geared aircraft are much more susceptible to ground looping. Nose high attitude on the ground, propeller powered taildraggers are more adversely
affected. Aircraft lack sufficient rudder authority in some flight regimes.
Cessna 170 de Havilland Canada DHC-2 Beaver Denny Kitfox Grumman Ag Cat Maule M-5 Piper J-3 Cub Vans RV-4
TRICYCLE LANDING GEAR
The landing gear on small aircraft consists of three wheels: two main wheels (one located on each side of the fuselage) and a third wheel positioned either at the front or rear of the airplane. Landing gear employing a rear-mounted wheel is called conventional landing gear. Airplanes with conventional landing gear are often referred to as tailwheel airplanes. When the third wheel is located on the nose, it is called a nosewheel, and the design is referred to as a tricycle gear. A steerable nosewheel or tailwheel permits the airplane to be controlled throughout all operations while on the ground.
Has nose wheel, which may be steerable. Main gear, on either side.
ADVANTAGE
Keeps aircraft level during take-off and landing. Its ease of ground handling. It allows more forceful application of the brakes during landings at high speeds without
causing the aircraft to nose over. It permits better forward visibility for the pilot during takeoff, landing, and taxiing. It tends to prevent ground looping (swerving) by providing more directional stability
during ground operation since the aircraft’s center of gravity (CG) is forward of the main wheels. The forward CG keeps the airplane moving forward in a straight line rather than ground looping.
DISADVANTAGE Greater summary mass of struts due to the bigger height of the nose strut hence bending moment which is
forced onto it by additional load from forces of inertia. Smaller permeability. The nose strut is reloaded because of inertia forces action and its
foot-pressure on ground is increased also during running. Considerably larger volumes in a fuselage indispensable for retracting the nose strut. It is
especially difficult when engine is positioned inside of a fuselage nose part. Longitudinal instability during movement of aircraft along an aerodrome with an elevated
front support during take-off run. Danger of emergency or even catastrophes during damage or breaking of front support. Possibility of appearance of self-energizing oscillations has freely orienting wheels of a
front support. Such oscillations are called ³shimmy.´The means for elimination of this phenomenon will
result in complicating and in weight increase of a structure
Cushions landing impact Heavily stressed area Main Landing Gear consists of the main weight-bearing structure Auxiliary landing gear includes tail wheels, skids, nose wheels, etc.
NON-ABSORBING LANDING GEAR
Includes Rigid landing gear, Shock-cord landing gear, Spring landing gear Rigid: helicopters, sailplanes. No flexing other than the structure. Shock cord system: uses “Bungee” cords Spring type uses spring steel (some Cessna’s)
SHOCK-ABSORBING LANDING GEAR
Dissipates landing energies by forcing fluid through a restriction This fluid generates heat, dissipated into the atmosphere Two types: Spring Oleo, and Air-Oil Oleo Spring Oleo is history by now Air Oleos are all very similar: a needle valve restricts fluid flow Air in the oleo holds the weight of the a/c on the ground Air Oleos present in both retractable and fixed gears
FIXED GEAR
Non retractable, usually bolted on to the structure Often uses fairings or wheel pants Cessna 152 Advantages:
Lighter weight Less complex Least costly
RETRACTABLE GEAR
Designed to eliminate drag (the greatest advantage) Can be either fully or partially retractable Direction of retraction depends on airframe model Methods of retraction: hydraulic, electric, mechanical, pneumatic Critical area of aircraft maintenance for safety reasons
HULLS AND FLOATS
Can be single float, or multiple Definition may include floating hulls (ex. “Lake” aircraft) Floating hulls may only require wing tip floats Skis used for snow and ice (wood, metal, composites) Skis may use shock cord to assist angle of ski attack Skis are mounted on the same strut as tires
HELICOPTER LANDING GEAR
Basic skid gear is common for small & mediums Wheel gear is used on sikorsky aircraft Retractable or cushioning gear may impart ground resonance Skid tubes are replaceable, and repairable Bending and deforming limits are established, and occasionally liberal Skid protectors are available, as are “bear paws” snow shoes Ground handling wheels are bolt-on towing additions
AIRCRAFT CONTROL SURFACES
Pilots control an aircraft by moving control surfaces.
AILERONS
The ailerons are on either side of the wings; these are controlled by the pilot rotating the yoke left and right.
Movement of the ailerons changes the shape of the wing, creating more curvature on one side (creating more lift) and drag on the opposite wing.
The ailerons are used in conjunction with the rudder to create a co-ordinated turn. Similar to a car on a race track with angled bends on the track, banking into the turn is much more comfortable than simply turning when at speed.
The aircraft 'rolls' when the ailerons are moved.
RUDDER
The rudder is a control surface on the tail.
The pilot controls the rudder by pressing on rudder pedals.
Pressing the left pedal causes the rudder to rotate to the left causing the tail to move right, in turn moving the nose of the airplane ot the left. Pressing the right rudder pedal does the opposite.
Rudder movement causes the aircraft nose to move left or right.
The aircraft 'yaws' when the rudder is moved.
ELEVATOR
The elevator is on the tail of the aircraft, moving the elevator causes the nose of the aircraft to go up or down, allowing the aircraft to climb or descent.
The pilot moves the elevator by pulling or pushing on the yoke.
Pulling on the yoke moves the elevator up causing the tail to go down, and the nose of the airplane to pitch up.
Pushing forward on the yoke pitches the aircraft down.
The aircraft 'pitches' when the elevator is moved.
LOCATION OF AIRCRAFT ENGINE
Engines may be placed in the wings, on the wings, above the wings, or suspended on pylons below the wings. They may be mounted on the aft fuselage, on top of the fuselage, or on the sides of the fuselage. Wherever the nacelles are placed, the detailed spacing with respect to wing, tail, fuselage, or other nacelles is crucial.
WING-MOUNTED ENGINES
Engines buried in the wing root have minimum parasite drag and probably minimum weight.
Their inboard location minimizes the yawing moment due to asymmetric thrust after engine failure.
However, they pose a threat to the basic wing structure in the event of a blade or turbine disk failure, make
It very difficult to maximize inlet efficiency, and make accessibility for maintenance more difficult.
If a larger diameter engine is desired in a later version of the airplane, the entire wing may have to be redesigned. Such installations also eliminate the flap in the region of the engine exhaust, thereby reducing CLmax.
AFT FUSELAGE ENGINE PLACEMENT
When aircraft become smaller, it is difficult to place engines under a wing and still maintain adequate wing nacelle and nacelle-ground clearances. This is one reason for the aft-engine arrangements. Other advantages are:
Greater CLmax due to elimination of wing-pylon and exhaust-flap interference, i.e., no flap cut-outs
Less drag, particularly in the critical take-off climb phase, due to eliminating wing-pylon interference.
Less asymmetric yaw after engine failure with engines close to the fuselage. Lower fuselage height permitting shorter landing gear and airstair lengths.
DISADVANTAGES The center of gravity of the empty airplane is moved aft - well behind the center of
gravity of the payload. Thus a greater center of gravity range is required. This leads to more difficult balance problems and generally a larger tail.
The wing weight advantage of wing mounted engines is lost. The wheels kick up water on wet runways and special deflectors on the gear may be
needed to avoid water ingestion into the engines. At very high angles of attack, the nacelle wake blankets the T-tail, necessary with aft-
fuselage mounted engines, and may cause a locked-in deep stall. This requires a large tail span that puts part of the horizontal tail well outboard of the nacelles.
Vibration and noise isolation for fuselage mounted engines is a difficult problem.
Aft fuselage mounted engines reduce the rolling moment of inertia. This can be a disadvantage if there is significant rolling moment created by asymmetric stalling. The result can be an excessive roll rate at the stall.
De Havilland Comet
De Havilland started about this design at the introduction of its DH Comet in 1949 which earned the name as the world’s first commercial jet airliner to reach production.
The success however was short-lived as the design was plagued by structural problems which ultimately changed the way airliners were constructed following a series of tragic crashes of the type.
This engine configuration was reflected on other British aircraft designs such as the Vickers-Armstrongs Valiant, the Handley Page Victor and the Avro Vulcan Bomber (V Bomber Force)
ENGINE PYLONS UNDER WING
Aircraft Classification Base on Purpose
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general,
the atmosphere of a planet. It counters the force of gravity by using either static lift or by using
the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines. Aircraft are
produced in several different types optimized for various uses; military aircraft, which includes
not just combat types but many types of supporting aircraft, and civil aircraft, which include all
non-military types, experimental and model. The two major categories of classification are