Ground School Class 4

Forces of Flight - Continued
Air is considered a fluid. Below speeds of Mach 0.3 it is considered an incompressible fluid. Static pressure plus dynamic pressure equals the total pressure which is expressed as:

P_s + P_d = P_t

P_d = 1/2(PV²)
where P = fluid density and V = fluid velocity

Newton's Laws of Motion (paraphrased)

1. An object at rest, tends to stay at rest. An object in motion tends to stay in motion.
2. Force equals mass times acceleration or F=MA
3. Any action results in an equal and opposite reaction.

Bernoulli's Principle (paraphrased)
For an incompressible fluid, an increase in velocity will result in a decrease in pressure.

Magnus Effect (paraphrased)
Creation of dynamic pressure around a spinning cylinder in a fluid. Very similar to the way a wing generates lift.

Coanda Effect (paraphrased)
Fuilds will follow a curved surface. This is what helps to create the boundary layer of air over the wing.

Lift


L = CL(1/2)pV²A
where:
CL = lift coefficient (calculated for each wing design)
p = air density
V = air velocity
A = wing area

Lift force occurs due to the creation of differential pressures above and below the wing. Lower pressure is created above and with the right configuration and speed, enough lifting force is generated to lift the weight of the aircraft.

Climb
The force vectors in a climb reduce the lift force and increase the induced drag. More thrust is needed to maintain a steady climb rate.

Wing Tip Vortices
All wings create wingtip vortices. The differential pressures that are created around the wing, collide at the wing tip and in doing so create a whirling of air that spirals down and away from the wing tips. This is a problem for planes that follow in the wake of other planes, especially during take-offs and landings.

High Lift Devices
High lift devices help create lift by changing the shape or the airflow over a wing. High lift devices are comprised of flaps and slats/slots. Slots are permanent holes thru the wing that allow high pressure air from underneath the wing to the top of the wing, helping to stabilize the boundry layer of air. Slats are slots with movable covers that are actuated under certain flight conditions.

Flaps are divided into four categories:

Plain - attached by a simple hinge, plain flaps change the curvature of the wing only.
Split - also attached by a simple hinge, split flaps drop from beneath the wing and increase drag as well as change the curvature of the wing.
Slotted - have a slot between the flap and the back of the wing.
Fowler - have a complex hinge that extends and lowers the flaps changing the curvature and increasing the area of the wing. Fowler flaps are what is outfitted on the C-150.

Ground Effect
Ground effect is caused by the wing vortices deflecting of of the ground and reducing the induced drag as a result. The effect generally occurs when the aircraft is within one/half wingspans length from the ground.

Stability
Positive Static - plane goes back to original flight path after you release controls.
Negative Static - plane does not go back to original flight path after you release controls.
Positive Dynamic - plane returns to flight path via a series of decreasing oscillations.
Negative Dynamic - diverges from original flight path via a series of increasing oscillations.

Three Axis of Flight
There are three axis of flight that each rotate around the center of gravity of the aircraft.

1. Pitch - lateral
2. Roll - longitudinal
3. Yaw - vertical

Center of Gravity

All aircraft have a center of gravity (CG) envelope. When the plane is loaded for flight, the center of gravity must fall within the envelope for the plane to fly safely. If your CG is too far forward:

1. aircraft nose will be heavy
2. needs a longer take-off roll
3. higher stall speed
4. more stable
5. may not be enough elevator to raise nose

If your CG is too far aft:

1. aircraft tail will be heavy
2. unstable in pitch
3. elevator is less effective

Lateral Stability

One way that aircraft maintain lateral stability is by mounting the wings in a dihedral configuration. This means the wings are mounted in a shallow V. This adds lift to the forward wing in a side-slip - correcting the side-slip automatically.

Stalls 

Stalls always occur when the critical angle of attack is exceeded, usually around 18 degrees. Usual recovery is to simply lower the nose.

1. Power On - usually during take-off
2. Power Off - usually during landing
3. Accelerated 
4. Cross-controlled
5. Secondary - too aggressive a stall recovery that results in a second stall

Next class: Spins and Flight Operations.

Ground School Class 3

Altimeter Gauge

Altimeter
Attached to the static air port, a sealed bladder inside the altimeter gauge inflates and deflates with changes in air pressure. The changes in size are transfered via a series of gears and levers to drive the gauge needle. A small dial and window allows for the setting of the current barometric pressure so the instrument reads the correct distance to the ground.

There are several types of altitude:

Indicated - altitude above sea level.
Pressure - 29.92 inches of mercury is the standard datum.
Density - pressure corrected for non-standard temp.
True (MSL) - Above Mean Sea Level.
Absolute (AGL) - Above Ground Level.

The allowable altimeter error for ILR flight is 75ft. Any greater error and the aircraft is no longer legal to fly.

The altimeter needs adjustment every so often (every 100 miles or so) to account for the changes in atmospheric pressure. This is especially important when traversing from high pressure to low pressure or from high to low temperature. As the pressure or temp drops the un-adjusted altimeter starts to show an increase in altitude, causing a correction that is descending rather than maintaining level flight.

There are a few ways to make the altimeter adjustments. The radio is the most common - as you pass near different airports, you can listen in to their ASOS or other automated weather broadcasts that will state the current barometric readings for the area.

Vertical Speed Indicator

Vertical Speed Indicator
Also connected to the static port, the VSI indicates the aircrafts rate of climb or descent in feet per minute. The trend is always accurate; if the needle shows accent, you're climbing, if ti shows descent, you're descending. However the rate indicated has some lag and takes a few seconds to settle down and provide and accurate reading.

Gyroscopic Instruments
These instruments use gyroscopes and the principle of rigidity in space, as the aircraft essentially rotates around the instruments. Gyros are either electric or vacuum powered.

Attitude Indicator

Attitude Indicator
The attitude indicator is also known as the eight ball. It show the pitch and roll of the aircraft in a single reading. The attitude indicator uses a vacuum powered gyroscope.

Directional Gyroscope

Directional Gyro
The directional gyro is just a stabilized compass. It needs to be adjusted via the magnetic compass every 15 minutes in order to remain accurate.

Turn Coordinator

Turn Coordinator
The turn coordinator uses the combination of an electric gyroscope and gravity to help the pilot make good coordinated turns using just the right amount of rudder.

"Whiskey Compass"

Magnetic Instruments
This means the regular compass or "whiskey" compass. It's just a ball floating in liquid, so the compass is hard to read in flight due to it's bouncing around all the time. The instrument has mass and is affected by acceleration, deceleration when traveling east or west and leads or lags turns when traveling north or south. The compass reads magnetic north and all navigation charts are based on true north. Our sectional charts provide the information to calculate a heading correction. An isogonic line follows the curve of the earths magnetic field. The difference between the isogonic line reading and true north is used to correct your navigation heading.

Forces of Flight
There are four forces of flight:

1. Lift
2. Thrust
3. Weight (Gravity)
4. Drag

When in level, non-accelerated flight, all four forces are in equilibrium.

Lift & Wings

Lift is generated by the wings. The wing elements are the leading edge, trailing edge, camber and the chord-line. The chord-line is an imaginary line drawn straight between the center of the leading edge and the center of the trailing edge. The angle of incidence is the angle that the wings are attached to the fuselage. The angle of attack is the angle between the chord-line and the relative wind. The wing will always stall at the same angle of attack, regardless of air speed.

Ground School Class 2

Fuel Systems

Fuel Systems
There are two types of fuel systems: gravity fed and pressurized. Gravity fed systems are utilized in high wing aircraft (like the C-150) and are just like they sound, gravity allows fuel to flow from the wing tanks down to the engine. In low wing aircraft, the engine is higher than the wings and a pressurized system that utilizes an engine driven pump pushes fuel up from the wing tanks. Pressurized systems also have electric fuel pumps so that fuel can be pumped with out the engine turning and can serve as booster pumps.

The fuel tanks are (usually) located in the wings. Fuel tanks are either a bladder inside the wing or what is called a wet wing, where the tank is an integral part of the wing itself. All planes must have at least one fuel quantity gauge. However, they are notoriously inaccurate and flight plans are based on fuel consumption rates which will be covered later on. A fuel selector valve allows the pilot to switch between tanks and keep the weight of fuel in the wings balanced while in flight. Each wing tank has a fuel strainer on the bottom that allows fuel to be drawn out and be inspected for water contamination. There is now only one grade of av-gas (100LL) that is tinted blue so you can distinguish it from jet fuel.

Oil System
Oil does four things in the engine. Provides lubrication and cooling as well as carries particulates away and removes them via the oil filter and finally provides a seal in the cylinder. Aircraft are required to have two gauges: oil temp and oil pressure.

Cooling System
Aircraft engines are air cooled. The cowling is designed to maximize the air flow over the cylinders. Some aircraft are equipped with cowl flaps, that are pilot controlled and can increase cooling during climbs, but can be closed to reduce drag during cruise speeds.

Props
There are two types of props - fixed and constant speed. A fixed prop is a single blade that comes in two types of configurations: climb and cruise. Climb props are efficient climbers, but not good for cruising. Cruise prop is just the opposite. Prop is chosen based on the most common use of the particular aircraft. A constant speed prop is also referred to as a variable pitch prop, as is pilot adjustable in flight. Fixed prop engines speeds are monitored via an tachometer. Constant speed prop engine speeds are regulated using a combination of a tachometer, a manifold pressure gauge and the chosen prop pitch.

Electrical System Diagram

Electrical System
Aircraft systems use either a generator (in older planes) or an alternator. An alternator system creates an A/C that is then converted to D/C to power the avionics and other systems. Aircraft use either 14V or 28V systems and are monitored via a load meter or an ammeter. The electrical system is controlled by a master switch that is a two part rocker switch, with one side for the battery and one side for the alternator. The system is protected by either fuses or circuit breakers. All the electrical components are usually tied together via two bus bars, a primary bus and an avionics bus.

Flight Instruments
The discussion on flight instruments starts with a primer on atmospheric pressure. A standard day refers to sea level elevation and 15 C (59 F) which is 29.92 inches of barometric pressure. There is a loss of 1 inch of pressure for every 1,000 ft change in elevation. Atmospheric pressure is measured via two instrument ports: the pitot tube and the static port. The pitot tube is just what is sounds like , a small tube that points forward and the amount of air pressure that passes thru the tube changes with the speed of the aircraft. The static port is a small port that is located perpendicular to the forward direction and and measures the static atmospheric pressure. The airspeed indicator (ASI) measures the difference between the pitot tube pressure and the static port pressure. Two other gauges are attached to the static port: the altimeter and the vertical speed indicator. The airspeed indicator has gauge markings for several V speeds.

ASI

V_s = stall speed indicated by the bottom of the green arc.
V_so = stall speed in the landing configuration (flaps extended and gear down) indicated by the bottom of the white arc.
V_fe = flap extension speed, or the maximum speed that you safely extend flaps
V_no = normal operating range indicated by the top of the green arc.
V_ne = never to exceed speed indicated by the red line.

The difference between the Vno and the Vne is the caution range indicated by the yellow arc.

There are several other V speeds that are not indicated on the ASI because they vary with the weight of the aircraft or other parameters that are listed in the POH.

V_a = maneuvering airspeed.
V_x = best climb angle
V_y = best rate of climb
V_glide = best glide speed
V_lo = landing gear operating speed
V_le = landing gear extended speed

There are four different types of airspeed:

IAS = indicated airspeed
CAS = calibrated airspeed
TAS = true airspeed
GS = ground speed.

We'll be covering this more when we get to flight planning.

Ground School Class 1

The class is pretty small with only 4 students, so we should be able to get into topics in some detail. Topics included an overview of pilot training, pilot certification, medical certificates, aircraft certification and the various additional training and endorsements needed to fly different types aircraft such as multi-engine, high performance, complex and sea planes. We also did a brief overview of human factors (causes of human error) and physiology.

The Major Components

Then we jumped into the topic of aircraft components - with a brief overview of fuselage, monocoque and semi-monocoque construction, wings, control surfaces, landing gear, brakes and the power plant. Wrapping up this section was a discussion of the required paperwork that all planes need to have in them at all times.

Due to our small class size, we got thru that section pretty quickly and jumped ahead to the next section that got into more detail regarding the power plant. Basics of reciprocating engines, carburetors (and the dreaded carburetor ice). We very briefly discussed super chargers and turbo chargers and we started to cover the ignition system.

Magneto System

Ignition System
The ignition system in small aircraft doesn't require an electrical system. The system is driven by two separate magnetos that each power one of two sets of spark plugs. This provides a critical redundancy that will allow the engine to get operating even when one magneto fails. Pretty handy, huh? This also means that you want to make sure both magnetos are off if you're moving the propeller. It can suddenly fire the engine and...well you get the idea. The system is controlled by an ignition switch that can be switched from left, right and both magnetos. This allows the pilot to isolate each side of the system and is done so during the start-up procedure.

Next class we'll continue power plant systems and flight instruments.

Ground School

Private Pilot Training Kit

Ground school starts on Monday. I dropped by the flight center to pick up my class materials and pay off the balance for the class. The school credited me for the log book that I purchased earlier, but otherwise shown to the right is everything in the kit I received:

• Private Pilot Manual
• Private Pilot Maneuvers Manual
• Private Pilot FAA Practical Test Guide
• Private Pilot Airmen Knowledge Guide
• Pre-Solo Written Exam
• Student Slide-Graphic Computer (E6B)
• PN-1 Navigation Plotter
• Pilot Logbook (credited for one I purchased for my first flight).
• 2011 FAR/AIM Manual
• Map Holder
• Flight Bag

School consists of 16, two and a half hour classes held Monday and Wednesday nights for the next 8 weeks. Total cost for classes and materials $538.49 (includes $50 deposit and $13.49 for Log Book purchased earlier). Now I just need to read the first two chapters of the Pilot Manual before Monday's class.