Chp 3 Aircraft construction

The categories of aircraft for certification of airmen include:

1. Airplane
2. Rotorcraft
3. Glider
4. Lighter-than-air
5. Powered-lift
6. Powered parachute
7. Weight-shift control aircraft

An airplane is defined as an engine-driven, fixed-wing aircraft that is supported in flight by the dynamic reaction of air against its wings.

Advanced avionics aircraft refers to an aircraft that contains a global positioning system (GPS) navigation system with a moving map display, in conjunction with another system, such as an autopilot.

The FAA certifies aircraft, aircraft engines, and propellers.

The airworthiness standards for these airplanes are specified in 14 CFR part 23.

A Type Certificate (TC) is issued by the FAA when they are satisfied that a product complies with the applicable airworthiness standards.

Standard airworthiness certificates are white and issued for normal, utility, acrobatic, commuter, or transport category aircraft, while Special airworthiness certificates are pink and issued for primary, restricted, limited category aircraft, and light sport aircraft.

The four forces are thrust, lift, weight, and drag.

Thrust is the forward force produced by the powerplant/propeller that opposes or overcomes the force of drag.

Drag is a rearward, retarding force caused by disruption of airflow, opposing thrust and acting rearward parallel to the relative wind.

The four forces are:

1. Thrust - the forward force produced by the engine.
2. Lift - the upward force produced by the wings, acting perpendicular to the flight path.
3. Weight - the downward force due to gravity, acting through the center of gravity (CG).
4. Drag - the backward force opposing thrust, acting opposite to the direction of flight.

The center of gravity (CG) is crucial for aircraft stability.

• If the CG moves rearward towards the tail, the aircraft becomes more dynamically unstable.
• It is important to set the CG with the fuel tank empty in aircraft with front-mounted fuel tanks, as using fuel can shift the CG and lead to instability.

The major components of an airplane include:

1. Fuselage - the central body that houses the crew, passengers, and cargo.
2. Wings - the main lifting surfaces that support the airplane in flight.
3. Empennage - the tail assembly that provides stability and control.
4. Landing Gear - the structure that supports the aircraft on the ground.
5. Powerplant - the engine or engines that provide thrust.

The two most popular types of fuselage structures used in modern aircraft are:

1. Monocoque - a single shell structure.
2. Semimonocoque - a structure that combines a shell with internal frames for added strength.

If the CG is too far aft, there may not be enough elevator nose-down force at low stall airspeed for recovery, which can lead to control issues during flight.

When the CG is too far forward, there will not be enough elevator nose-up force to flare the airplane for landing, potentially resulting in a hard landing.

The main structural components of a truss-type fuselage include:

1. Longerons
2. Struts
3. Bulkhead
4. Stringers

Monoplanes have a single set of wings, while biplanes have two sets of wings. This distinction affects the aircraft's design and performance characteristics.

A semi-cantilever wing structure is characterized by having external braces or wing struts that transmit flight and landing loads through the struts to the main fuselage structure, typically attached approximately halfway out on the wing.

The principal structural parts of an airplane wing include:

1. Spars
2. Ribs
3. Stringers

These components are reinforced by trusses, I-beams, tubing, or other devices, including the skin.

Ailerons:

• Extend from the midpoint of each wing to the tip.
• Move in opposite directions to create aerodynamic forces that cause the airplane to roll.

Flaps:

• Extend from the fuselage to near the midpoint of each wing.
• Normally flush with the wing's surface during cruising flight.
• Move simultaneously downward when extended to increase the lifting force of the wing for takeoffs and landings.

The design of a wing is tailored to specific types of flying and can include variations such as:

• Traditional wings: Standard design for general flight operations.
• Weight-shift control aircraft wings: Highly swept design to reduce drag and allow for controlled flight through weight shifting.
• Flexing and shifting wings: Adaptations that change shape based on aerodynamic needs during flight.

The stabilator is a one-piece horizontal stabilizer that pivots from a central hinge point. It is controlled by the pilot using the control wheel. When the pilot pulls back on the control wheel, the stabilator pivots, causing the trailing edge to move up, which increases the aerodynamic tail load and raises the nose of the airplane.

Trim tabs are small, movable surfaces installed on the ailerons, rudder, and/or elevator. They reduce control pressures and help maintain the control surfaces in the desired position, making the aircraft easier to control during flight.

The main types of landing gear used in airplanes are:

1. Wheeled Landing Gear: Consists of three wheels - two main wheels and a third wheel either at the front (nosewheel) or rear (tailwheel).
2. Conventional Landing Gear: Also known as tailwheel airplanes, where the third wheel is at the rear.
3. Tricycle Gear: Where the third wheel is located on the nose.
4. Floats: Used for water operations.
5. Skis: Used for landing on snow.

The primary function of the powerplant, which includes both the engine and the propeller, is to provide power to turn the propeller. Additionally, it generates electrical power, provides a vacuum source for flight instruments, and in most single-engine airplanes, supplies heat for the pilot and passengers.

A propeller generates thrust through aerodynamic action by creating a pressure differential:

• A high-pressure area is formed at the back of the propeller's airfoil.
• A low-pressure area is produced at the face of the propeller.

This pressure differential develops thrust, pulling the airplane forward, similar to how lift is generated by a wing.

The amount of lift produced by the propeller is directly related to the angle of attack (AOA), which is the angle at which the relative wind meets the blade. The AOA continuously changes during flight depending on the direction of the aircraft, affecting lift generation.

The primary function of an aircraft's electrical system is to:

1. Generate electrical power
2. Regulate electrical power
3. Distribute electrical power throughout the aircraft

This system powers flight instruments, essential systems (like anti-icing), and passenger services (like cabin lighting).

In conventional airplanes, the primary flight controls consist of:

1. Elevators for pitch
2. Ailerons for roll
3. Rudder for yaw

These controls are operated by the pilot or an automatic pilot to govern the aircraft's attitude and flight path.

The truss structure in aircraft construction has the following characteristics:

• Lacks a streamlined shape
• Composed of lengths of tubing called longerons welded to form a framework
• Vertical and horizontal struts provide additional support
• Additional stringers and bulkheads shape the fuselage and support the covering

This structure is well-braced but requires additional struts to resist stress from various directions.

Monocoque construction differs from truss structure in that:

• It uses stressed skin to support almost all loads, similar to an aluminum beverage can.
• It is generally stronger and more streamlined compared to truss structures.
• Monocoque construction is less tolerant of damage compared to truss structures, which can distribute loads across multiple members.

Monocoque construction relies on the external skin to carry most of the stresses, eliminating the need for internal bracing, while semimonocoque construction uses a substructure (bulkheads and stringers) to reinforce the skin and carry some of the bending stresses.

Jack Northrop used two molded plywood half-shells glued together around wooden hoops or stringers, utilizing a semi-circular concrete mold and an inflated rubber balloon to press the plywood against the mold.

Composite materials offer extremely smooth skins and the ability to easily form complex curved or streamlined structures, making them advantageous for modern aircraft design.

The most common matrix used in aircraft composite materials is epoxy resin, preferred for its strength and good high-temperature properties compared to other options like polyester resin.

The use of composites began with soft fiberglass insulation in B-29 fuselages during World War II, evolved to high-performance sailplanes in the late 1950s, and by 2005, over 35 percent of new aircraft were constructed of composite materials.

The most common reinforcing fibers are fiberglass and carbon fiber.

Fiberglass:

• Advantages: Good tensile and compressive strength, good impact resistance, easy to work with, relatively inexpensive, readily available.
• Disadvantages: Somewhat heavy, difficult to make lighter than a well-designed aluminum structure.

Carbon Fiber:

• Advantages: Generally stronger in tensile and compressive strength, much higher bending stiffness, considerably lighter than fiberglass, can be significantly lighter than aluminum structures.
• Disadvantages: Poor impact resistance, fibers are brittle and tend to shatter under sharp impact, more expensive than fiberglass.

The advantages of composite materials include:

1. Lighter Weight: Composites can be lighter than metals, but this depends on the structure and type of composite used.
2. Reduced Drag: Smooth, compound curved structures reduce drag, enhancing performance, as seen in sailplanes and aircraft like Cirrus and Columbia.
3. Corrosion Resistance: Composites do not corrode, leading to lower long-term maintenance costs, especially in designs like the Boeing 787.
4. Performance in Flexing Environments: Composites do not suffer from metal fatigue, allowing for longer design lives in applications like helicopter rotor blades.

The disadvantages of composite materials include:

1. Lack of Visual Proof of Damage: Composites may not show visible signs of damage after impacts, making it difficult to assess structural integrity.
2. Hidden Damage: Low energy impacts can cause extensive delaminations that are not visible on the surface.
3. Repair Complexity: Damage from medium to high energy impacts may require extensive repairs, as the damage can be larger than what is visible.
4. Inspection Needs: Regular inspections by someone familiar with composites are necessary to identify underlying damage.

Medium and high energy impacts result in visible damage such as delaminations, crushing of the surface, or punctures. These types of damage are easy to detect with the naked eye.

The damaged area should be covered and protected from rain. A piece of 'speed tape' can be used over the puncture to protect it from water, but this is not a structural repair.

Many epoxy resin systems begin to weaken over 150 °F. To minimize heat damage, white paint is often used on composites, as it helps keep the temperature lower compared to darker colors.

Only mechanical methods such as gentle grit blasting or sanding are allowed for removing paint from composites. Chemical paint strippers are harmful and should not be used.

Lightning strike protection involves spreading the energy from a lightning strike over a large surface area to lower the amps per square inch to a harmless level. The outer skin of the aircraft serves as the path of least resistance for the electrical energy.

Modern composites using epoxy resin are generally not affected by fuel, oil, or hydraulic fluid spills, provided the spill does not attack the paint. However, inexpensive polyester resin structures may have issues with auto gas containing ethanol.

The two most common types of metal meshes used are aluminum and copper mesh. Aluminum is typically used on fiberglass, while copper is used on carbon fiber.

Fiberglass is preferred for internal radio antennas because it is transparent to radio frequencies, whereas carbon fiber is not.

The three categories of instrumentation in aircraft are:

1. Performance Instruments
2. Control Instruments
3. Navigation Instruments

The primary flight display (PFD) serves to present essential flight information to the pilot, replacing conventional instruments and helping to de-clutter the instrument panel.

Electronic flight displays (EFDs) have improved aircraft instrumentation by replacing individual instruments with multiple liquid crystal display (LCD) screens, which increases safety and reduces clutter through the use of solid state instruments with lower failure rates.

Control instruments display immediate attitude and power changes, allowing for precise adjustments. They do not indicate aircraft speed or altitude; these variables must be referenced from performance instruments.

Navigation instruments indicate the aircraft's position relative to navigation facilities or fixes, including course indicators, range indicators, glideslope indicators, and bearing pointers. They also provide pilotage information for maneuvering the aircraft along a predetermined path.

GPS is a satellite-based navigation system that requires a receiver to lock onto signals from at least three satellites to calculate a two-dimensional position (latitude and longitude). With four or more satellites, it can determine a three-dimensional position (latitude, longitude, and altitude). It operates in all weather conditions, anywhere in the world, 24/7.

The airspeed indicator displays the aircraft's current speed, typically shown in knots. It is circular with a needle pointing to the current speed, and the scale ranges from 0 to 250 knots. The colors change as airspeed increases, with green, yellow, and red ranges indicating different speed categories.

The attitude indicator shows the aircraft's orientation relative to the horizon, featuring a blue sky above a brown ground line. A white aircraft symbol in the center indicates the bank and pitch angle of the aircraft.

The altimeter indicator displays the aircraft's altitude, typically in feet. It features multiple needles indicating different scales and has a digital readout near the bottom, showing the current altitude, which is approximately 29,924 feet in this case.

The turn coordinator indicates the rate of turn of the aircraft using a miniature aircraft symbol that banks left or right. It also features a ball that indicates slip or skid, with the needle pointing to the left in this instance.

The heading indicator shows the aircraft's current heading using a compass rose. A yellow heading bug can be set to a desired heading, which is indicated at 270 degrees in this case.

The vertical speed indicator shows the rate of altitude change, indicating whether the aircraft is climbing or descending. In this case, it shows a descent rate of 0 feet per minute, indicating level flight.

The slip/skid indicator reveals the aircraft's lateral balance during flight. In this case, it shows that the aircraft is slightly skidding, with the ball located slightly to the right of the center line.

The airspeed tape indicator displays the current airspeed in a vertically oriented format, showing a range of airspeeds. In this case, it indicates a current airspeed of approximately 100 knots.

The vertical speed and tape indicator displays the current vertical speed of the aircraft, which is close to 0 feet per minute in this case. It features a red line indicating negative vertical speed.

The heading bug is used to set a desired heading for the aircraft, allowing pilots to maintain or navigate towards a specific course. It can be adjusted to indicate the target heading, such as 270 degrees.

The course arrow points to the selected course or radial, helping pilots navigate along a specific flight path or direction.

The airspeed indicator measures the speed of the aircraft relative to the surrounding air, typically displayed in knots.

The attitude indicator shows the aircraft's orientation relative to the horizon, helping pilots maintain level flight and understand their pitch and roll angles.

The altimeter measures the aircraft's altitude above sea level, allowing pilots to maintain a safe flying height and avoid terrain.

The turn coordinator indicates the rate of turn and helps pilots maintain a standard rate of turn during flight.

The manifold pressure gauge measures the pressure of the air-fuel mixture entering the engine, indicating engine power and performance.

The engine RPM indicator displays the engine's revolutions per minute, which is crucial for monitoring engine performance and ensuring it operates within safe limits.

The direction indicator shows the aircraft's heading, helping pilots navigate and maintain their intended flight path.

The aircraft is heading 020°, but the course is to the left, indicating a potential need to adjust the flight path to align with the intended course.

When the glideslope needle points down, it indicates 'fly down' to intercept the glideslope, meaning the aircraft is above the desired glide path and needs to descend.

When the glideslope needle points up, it indicates 'fly up' to intercept the glideslope, meaning the aircraft is below the desired glide path and needs to ascend.