General topics on how do airplanes fly?

Radio communications in flight

Flying airplanes is statically considered safer than driving cars. This is due to many factors. Besides the technical checks and airworthiness certifications of an aircraft, and the pilot's training, radio communications plays a vital roll in making flying relatively safe.

Radio communications

Communications take place between the pilot in the aircraft and the air traffic control (ATC). There are 3 types of communications: verbal communications, transponder communications and navigational communications. This is applicable to small airplanes as well as to big jetliners.

ATC's responsibility is to control and organize controlled airspace to separate aircraft in flight and on the ground. There is a none controlled airspace as well, where no ATC is available, however pilots communicate with each other over the radio to periodically report their position.

Verbal communications happens between pilots and the ATC through a two-way radio device makred as COMM1 and COMM2 with standby STBY. Having 2 radios is for safety reasons in case one of them fails. If the the pilot had a radio failure, he has to follow a certain procedure to the appoarch the airfield and land. Moreover, he has to dial a certain code on the transponder. Radio failure code is universal at 7600.

The two-way radio in a Cessna 172 

Transponder communications (XPDR)

In controlled airspace, and prior to any flight, the ATC gives each aircraft a squawk code to dial on the transponder, This squawk code becomes the identifier of the aircraft.

There are preset codes that the pilot dials on the transponder for certain situations as follow:

• Hijacked: Squawk 7500
• Radio failure: Squawk 7600
• Emergency: Squawk 7700

Once these codes picked up by the ATC, they immediately identify the aircraft situation and deal with it accordingly.

Navigation communications

Navigation communication is most complex, and it is essential for aircraft and pilots to navigate their way from point to point, and to follow ATC instructions.

There are radio stations on the ground that keep on transmitting signals at preset frequencies. The NAV radio at the aircraft picks up the signal and provides the pilot with important information to orient and fly the aircraft.

Navigational equipment on the ground are: 

Very High Omni Directional Radio (VOR) which is usually equipped with a distance measuring device that provide the pilot with the distance in nautical miles DME to or from from the station. 

ADF Automatic Direction Finder, some are also equipped with DME.

ILS Instrument landing system, this system helps the aircraft to approach the runway through providing the pilot with information the aircraft's approach slope, and guidance to the runway center line. Also it provides the pilot with the distance from the TDZ, the touchdown zone. This is a very helpful instrument and pilots rely on it a lot in poor weather.

General topics on how do airplanes fly?

Primary Flight Instruments in a Cessna 172

In this post, we will go inside the airplane and see the primary flying instruments in the cockpit of a Cessna 172.

Since there are many instruments at the cockpit and to easily orient the pilot with them, engineers had layout the primary instruments in a T-shaped order. Please refer to the image below.

These primary flight instruments and their functions are as follow:

On the top left hand side: 

The Air Speed Indicator (ASI). This instrument is operated through the pitot (that we saw being uncovered pre-flight in the video right under the outboard wing)

The ASI is very helpful instrument at times of the flight, as it provides the pilot with the various speed to fly the aircraft.

• Let us start with the white band. There is the lower limit speed and the upper limit speed. The speed below the lower limit of the white band is the stall speed or Vs. The speeds at the white band is the operating speed when flap are extended or Vf
• The green band speed limits is the normal operating speeds of the airplane or Vo
• The yellow band speed limits is the maximum structural cruising speed or Vno
• The red dash is the never exceed speed or Vne

On the top center:

The Attitude Indicator (AI). It is a gyro instrument and it requires a suction devise to create vacuum within the AI instrument to operate properly.

The AI provide the pilot with the pitch up and pitch down attitude of the airplane, in addition to the bank of the airplane, either to the left or to the right.

While pitching up or down, there are lines that indicate the angle of the pitch in degrees, i.e. 10 degrees up or up to 30 degrees down.

While banking the airplane to turn left or right, the AI provides the pilot with the angle of banking. Any turn or bank exceeding 30 degrees is considered to be a steep turn, and it requires special skills to handle.

On the top right hand side:

The Altimeter. The altimeter works by measuring the differential of the pressure of the atmosphere. It need a static pressure devise that is attached on the fuselage of the airplane to operate properly.

The altimeter is require to indicate the altitude of the aircraft above the ground level. In order to give the right and proper indications or readings, it has to be adjusted to the pressure altitude of the airfield the airplane is operated and it is called the QFE. When above the flight levels the pressure altitude is adjusted to the standard pressure altitude which is called QNH or above mean sea level and usually is set at 29.92".

On the bottom center:

The Heading Indicator. This instrument is also a gyro instrument. 

The HI is used to indicate the heading of the aircraft in relevance to the magnetic north. This is used in flight to help the pilot find his way or to follow the air traffic control (ATC) instructions of the headings.

The Glass cockpit of modern jetliners

General topics on how do airplanes fly.

The Private Pilot License (PPL)

I will be posting many articles under this title, and today I have chosen the topic on: What you need to study and do to become a licensed Private Pilot and hold a PPL (Private Pilot License) for a single engine land aircraft with VFR rating (visual flying rules).

Requirements vary depending on the country you are being licensed in, but in general these are the prerequisites and the phases a pilot to be will pass through in ground lessons and practical flying lessons:

That is me, ready for a flight above Jeddah in KSA

Me (on the left) at the glass cockpit of a Cessan 172 G1000

Phase 1: Student pilot

First, you become a student pilot and these are the requirements to submit and register for a student pilot in a flying school or flying academy:

1) 18 years old +
2) Good command of the English language
3) Valid category 1 or 2 medical certificate
4) Money of course!

Being a student pilot you will be studying ground lessons on the following topics:

- Air-law
- Stroke engines
- Meteorology
- Aerodynamics
- Navigation
- Medical

While attending the ground lessons, your instructor will be taking you for dual instruction practical flying lessons, where you will start flying the aircraft on the left seat. Ground lessons could vary, but usually it will take around 25 hours.

In the practical flying lessons, you would need at least 45 hours of flying hours as follows: 17 hours dual instruction, 3 solo hours cross-country, 5 hours instrument time. In addition to 12 hours must be solo and 8 hours of the cross-country with triangular flight not less than 150 nautical miles including 2 full-stop landing.

Phase 2: Solo student pilot

This is a very important phase in every pilot's flying experience. Every pilot will remember the day when his instructor clears him for the solo. After flying at least 10 hours of dual instruction, the instructor will evaluate your student pilot's flying capabilities and if you are ready in terms of knowledge, practice and mentally, the instructor will ask the student pilot to do his first solo, i.e. flying the aircraft on his own for the first time, with at least one take-off and one landing.

Phase 3: A licensed private pilot with VFR rating

After successfully finishing the required flying hours and the ground lessons, the student pilot will sit for a written exam to answer 100 multiple choice question on all the subjects he studied. The passing grade is usually at 70%.

Later, the student pilot will have a check-ride by an examiner instructor. If the instructor is satisfied with the results of the check-ride, he will sign-off his approval for licensing the pilot. Usually, during the check-ride the instructor will ask the student to do basic maneuvers of take-off and landing in normal and short fields, flying the circuit of an airport, climbing and descending turns, in addition to steep turns, approaching the stall and recovery from a stall with many navigation questions and practices.

When you become a licensed private pilot, you are allowed to fly the plane solo and you may take passengers with you but without charging them for the flight.

What are the moving surfaces that help flying the airplane?

The moving parts or surfaces on the body of an aircraft, is the subject of this fifth post.

Today, we will discuss the moving parts/surfaces on an aircraft and how they are controlled. These surfaces main function is to steer and control the aircraft during flight. Most of the moving parts are on the wing, in addition to the horizontal stabilizer and the vertical stabilizer or the rudder.

Let us start with the wing moving surfaces:

Besides the main function of the wing which is generating lift to carry the weight of the aircraft, it is also the tank or reservoir for the fuel.

In a small plane, like a Cessna 152 or 172 there are 2 moving parts attached to the wing. These parts are called: the FLAPS and the AILERONS. Usually these parts are moved and controlled by wires and pulleys attached to the control wheel or control stick.

- The purpose of the FLAPS is to increase the area of the wing, and thus generating more lift at lower air-speeds.
- While the AILERONS function is to bank the aircraft left or right making it turn to the desired direction.

While in big jets like an Airbus A321 or Boeing 777, there are many moving parts attached to the wing like: The SLATS, the FLAPS, the AILERONS, and the AIR-BRAKES or the SPOILERS. These surfaces are moved and controlled by hydraulic controllers with an order from the pilot through actuators connected to the control wheel or the joystick.

- The SLATS function is similar to that of the FLAPS, from the leading edge of the wing.
- AIR-BRAKES are used in flight so the aircraft loses height quickly without increasing its speed. On ground are used once the aircraft touches down to transfer the weight of the aircraft from the wings to the gears or the tires.

The horizontal stabilizer moving surfaces:

The horizontal stabilizer shape is symmetrical, unlike the airfoil shape of a wing. Once the pilot pulls back or pushed forward on the control wheel or joystick the stabilizer moves up and down, thus making the aircraft nose up or down leading the aircraft to climb or decent. There is also another smaller surface attached to the horizontal stabilizer which is called the trimmer that helps in easing the pressure on the control wheel of the aircraft.

The vertical stabilizer moving surfaces:

The vertical stabilizer or the RUDDER is also symmetrical in shape. The RUDDER helps the aircraft to move around vertical axis and thus pointing the nose of the aircraft to the desired direction the pilot wants. These controlled maneuvers are essential during the take-off and the landing phases of the flight.

Video assignement

A video on how to do an aircraft pre-flight outside check.

In this video, we are going to see how safety comes first when flying an aircraft.

It all starts with the pre-flight outside check. In the video we will learn how we conduct the outside check, the pattern that we should move into as well as the items that we need to make sure that are working and best shape following a pre-flight outside checklist.

Please have a look and let me know if you have any question.

What is the purpose of an engine?

Types of aircraft engines and why we need it, at all times?

The engine in an aircraft, is like the heart in our body. The main purpose of the engine is to produce power through torque generated by the blades connected to it, to push the aircraft forward and into the air. 

Aircraft Engines are divided into two types: piston engine (4 stroke engine) and jet engine (continues flame engine). Both types of engines work on fuel. Piston engine use Avgas (aviation gasoline) grade 100 octane, while jet engines use jet fuel called Kerosene.

How piston engines generate thrust?

The piston engine. ( we will not discuss the jet engine)Many aircraft make use of propellers, which slice through air to create thrust. Within air mass, airplane propellers move in a motion that is similar to a corkscrew, what is called a helical motion.

The internal combustion process in the piston engine of aircraft generates power and develops force. In simpler words, the airplane engine provides the propeller with power; the propeller uses this power to create thrust.

To generate thrust, airplane propellers must rotate. Power delivered from the engine helps in achieving this rotation. The engine, a crankshaft, and the propeller, make up the whole thrust-generating assembly. 

Thrust is essential to move the airplane into the air at all times, so thrust opposes drag and moves the airplane forward into the air to generate lift from the wings.

How do wings carry / lift the weight of the airplane?

We are progressing. This post is about "How wings carry / lift the weight of the airplane".

The lift generated by the airplane wings is based on Bernoulli's Law. The law states that: Total pressure equals Static Pressure plus Dynamic Pressure. TP= SP + DP.

Therefore and since the Total Pressure is a constant, if Dynamic Pressure increases, Static Pressure Decreases. You remember this from school days: indirectly proportional.

The trick or as I call it, the cleverness of engineering, the designers have made the shape of the wing as an airfoil. Where, the upper surface of the wing is curved and thus making it longer and bigger than the lower surface of the wing.

The relative wind (the air the hits the airplane) when moving forward, hits the wing and splits into two streams.The upper stream and lower stream.

Since the upper surface of the wing is curved making it longer and bigger than the lower surface, the air has to travel faster to travel the same distance and at the same time Travelling faster and since the total pressure is a constant (as per Bernoulli's Principle), the dynamic pressure becomes greater and the static pressure becomes smaller.

Comparing it to the same air stream passing on the lower surface of the wing, the static pressure at the lower surface becomes bigger than the static pressure on the upper surface, thus lift is generated.

The greater the angle of attack (see the picture on the right in the above) the more the lift is generated. However, when the angle of attack reaches the critical angle, no more lift is generated and the airplane is stalled. That is due to the turbulent airflow over the upper surface of the wing.

What are the forces that act on an airplane?

In this third post, we will talk about the forces that act on an airplane.

There are four forces that act on an airplane.

Weight, which is a downward force, is due to the weight of the aircraft and the effect of gravity.
Lift, which is an upward force, is due to the airfoil dynamic shape of the wings.

Thrust, which is the forward pulling force, is generated by the power plant or the engine and the propellers attached to it.
Drag, which is the backward pushing force, is generated by the friction between the body of the airplane and the relative air or by the tires with the tarmac when the aircraft is on the ground.

The total weight of an airplane will include the weight of the body, the fuel, the cargo and the occupants.
The lift opposes the weight and once it becomes equal or greater than the weight,  the airplane will airborne and starts climbing into the air. The lift is generated by the wings design. Wings are curved in shape making it an airfoil.  This is called Bernoulli's principles. (will talk about it in more details in the next post).

The thrust generated by the engine, overcomes the drag and thus the airplane will start moving forward. The faster the airplane moves, the faster the air passes through. Therefore, the more power generated by the engine, the faster the airplane will roll or fly into the air.