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Ground School: Preflight Inspection

The success of a flight depends largely on thorough preparation. In the course of your training, a pattern of regular preflight actions should be developed to ensure that this is the case. This includes planning the flight, and checking the airplane. These preflight actions must be based on the checks found in the pilot’s operating handbook (POH), manufacturer’s information manual or the FAA-approved airplane flight manual (AFM) for your airplane. Today we’ll share an excerpt from The Pilot’s Manual: Flight School (PM-1C) regarding the preflight inspection of your airplane.

Preparing the Airplane
The information manual for your airplane will contain a list of items that must be checked during:

  • the preflight inspection (external and internal);
  • the preflight cockpit checks;
  • the engine power check; and
  • the before-takeoff check.

At first, these checks may seem long and complicated, but as you repeat them thoroughly prior to each flight, a pattern will soon form. It is vital that the checks are carried out thoroughly, systematically and strictly in accordance with the manufacturer’s recommended procedure. Use of written checklists, if performed correctly, will ensure that no vital item has been missed, but some pilots prefer to memorize checks. The comments that follow are only general comments that will apply to most airplanes.

The External Inspection
Always perform a thorough external inspection. This can begin as you walk up to the airplane and should include:

  • the position of the airplane being safe for start-up and taxi (note also the wind direction and the likely path to the takeoff point); and
  • the availability of fire extinguishers and emergency equipment in case of fire on start-up (a rare event, but it does happen).

Some of the vital items are:

  • all switches off (master switch for electronics, magneto switch for engine) as a protection against the engine inadvertently starting when the propeller is moved;
  • fuel check for quantity and quality (drain into a clear cup);
  • oil check; and
  • structural check.

A list of typical walkaround items is shown below. Each item must be inspected individually, but do not neglect a general overview of the airplane. Be vigilant for things such as buckling of the fuselage skin or popped rivets since these could indicate internal structural damage from a previous flight. Leaking oil, fuel forming puddles on the ground, or hydraulic fluid leaks from around the brake lines also deserve further investigation. With experience, you will develop a feel for what looks right and what does not. The walkaround inspection starts at the cockpit door and follows the pattern specified in the checklist provided by the aircraft manufacturer.

  • Parking brake on.
  • Magneto switches off.
  • Landing gear lever (if retractable) locked down.
  • Control locks removed.
  • Master switch on (to supply electrical power).
  • Fuel quantity gauges checked for sufficient fuel for the planned flight.
  • Fuel selector valves on.
  • Flaps checked for operation; leave them extended for external inspection.
  • Stall warning (if electrical) checked for proper operation.
  • Rotating beacon (and other lights) checked, then off.
  • Master switch off.
  • Primary flight controls checked for proper operation.
  • Required documents on board: MAROW plus airman certificate and medical certificate for the pilot. (Note: under some circumstances a medical certificate may not be required.)
  • Cabin door securely attached, and latches working correctly.
  • Windshield clean (use correct cloth and cleanser).


  • All surfaces, the wing tip, leading and trailing edge checked for no damage or contamination; remove any frost, snow, ice or insects (on upper leading edge especially, since contamination here can significantly reduce lift, even to the point where the airplane may not become airborne).
  • Wing tip position light checked for no damage.
  • Flaps firmly in position and actuating mechanism firmly connected and safety-wired.
  • Aileron locks removed, hinges checked, correct movement (one up, the other down) and linkages safety-wired, mass balance weight secure.
  • Pitot tube cover removed and no damage or obstructions to tube (otherwise airspeed indicator will not respond).
  • Fuel contents checked in tanks and matching fuel quantity gauge indications; fuel caps replaced firmly and with a good seal (to avoid fuel siphoning away in flight into the low-pressure area above the wing).
  • Fuel sample drained from wing tanks and from fuel strainer into a clear container. Check for correct color (blue for 100LL, green for 100-octane), correct fuel grade, correct smell (aviation gasoline and not jet fuel or kerosene), no water (being denser, water sinks to bottom), sediment, dirt or other contaminant (condensation may occur in the tanks overnight causing water to collect in the bottom of the tanks, or the fuel taken on board may be contaminated).
  • Fuel port, or fuel vent (which may be separate or incorporated into the fuel cap) clear (to allow pressure equalization inside and outside the tanks when fuel is used or altitude is changed, otherwise the fuel tanks could collapse or fuel supply to the engine could stop as fuel is used).
  • Stall warning checked (if possible).
  • Inspection plates in place.
  • Wing strut checked secure at both ends.


  • All surfaces, including underneath checked for skin damage, corrosion, buckling or other damage (corrosion appears as surface pitting and etching, often with a gray powdery deposit); advise a mechanic if you suspect any of these.
  • No fuel, oil or hydraulic fluid leaking onto the ground beneath the aircraft.
  • Inspection plates in place.
  • Static ports (also called static vents)—no obstructions (needed for correct operation of airspeed indicator, altimeter and vertical speed indicator).
  • Antennas checked for security and no loose wires.
  • Baggage lockers—check baggage, cargo and equipment secure, and baggage compartments locked.

Main Landing Gear

  • Tires checked for wear, cuts, condition of tread, proper inflation, and security of wheel and brake disk.
  • Wheel oleo strut checked for damage, proper inflation, and cleanliness.
  • Hydraulic lines to brakes checked for damage, leaks and attachment.
  • Gear attachment to the fuselage—check attachment, and be sure there is no damage to the fuselage (buckling of skin, popped rivets).

Nose Section

  • Fuselage checked for skin buckling or popped rivets.
  • Windshield clean.
  • Propeller checked for damage, especially nicks along its leading edge, cracks and security (and for leaks in the hub area if it is a constantspeed propeller).
  • Propeller spinner checked for damage, cracks and security.
  • Engine air intake and filter checked for damage and cleanliness (no bird nests or oily rags).
  • Nose wheel tire checked for wear, cuts, condition of tread, proper inflation, and security of nose wheel.
  • Nose wheel oleo strut checked for damage, proper inflation (four to six inches is typical), security of shimmy damper and other mechanisms.
  • Open engine inspection panel; check engine mounts, engine, and exhaust manifold for cracks and security (to ensure that no lethal carbon monoxide in the exhaust gases can enter the cockpit—exhaust leaks may be indicated by white stains near the cylinder head, the exhaust shroud or exhaust pipes).
  • Check battery, wiring and electrical cables for security (firmly attached at both ends).
  • Check the oil level; top up if necessary (know the correct type and grade of oil to order); ensure that the dipstick is replaced properly and the oil cap is firmly closed to avoid loss of oil in flight.
  • Close the inspection panel and check its security.

Other Side of Airplane
Repeat as appropriate.


  • Remove control locks if fitted.
  • All surfaces checked for skin damage (vertical stabilizer and rudder, horizontal stabilizer, elevator and trim tab); remove any contamination such as ice, frost or snow.
  • Control surface hinges checked for cracks, firmness of attachment, safety-wiring and correct movement.

Chocks and Tiedown Ropes
Chocks and tiedowns removed and stowed (after checking the parking brake is on).

Overall View
Stand back and check the overall appearance of the airplane. It cannot be emphasized too greatly just how important this preflight inspection by the pilot is. Even if you have no experience in mechanical things, you must train yourself to look at the airplane and notice things that do not seem right. Bring any items that you are unsure of to the attention of your flight instructor or a mechanic. At this stage, you are now ready to seat yourself in the airplane and begin the internal cockpit inspection.

The Cockpit Inspection
Always perform a thorough cockpit inspection. The cockpit inspection involves preparing the cockpit and your personal equipment for flight. It should include:

  • Parking brake set (on).
  • Required documents on board (MAROW items).
  • Flight equipment organized and arranged in an efficient manner so they are readily available in flight (flight bag, charts prefolded to show your route, computer, pencils, flashlight, and so on).
  • Fuel on.
  • Seat position and harness comfortable and secure, with the seat definitely locked in position and rudder pedals (if adjustable) adjusted and locked into position so that full movement is possible.
  • Ignition switch (magnetos) off (so that the engine is not live).
  • Master switch on (for electrical services such as fuel gauges).
  • Flight controls checked for full and free movement (elevator, ailerons, rudder and trim wheel or handle). Trim set to takeoff position.
  • Engine controls checked for full and free movement (throttle, mixture control and carburetor heat).
  • Scan the instruments systematically from one side of the panel to the other for serviceability and correct readings.
  • No circuit breakers should be popped nor fuses blown (for electrical services to operate).
  • Microphone and/or headsets plugged in (if you are to use the radio) and test intercom if used.
  • Safety equipment (fire extinguisher, first aid kit, supplemental oxygen if planning to fly high, flotation equipment for overwater flights) on board and securely stowed.
  • Loose articles stowed.
  • Checklists on board and available.
  • Read the preflight checklist, if appropriate.

Normal checklists are found in Section 4 of the typical pilot’s operating handbook, and emergency checklists are found in Section 3. Written checklists are used to confirm that appropriate procedures have been carried out, for example, the before-takeoff checklist or the engine fire checklist. In earlier days, when airplanes were simpler, checks were usually memorized. Nowadays, in more complex airplanes and in a much busier operating environment, many checks are performed with the use of standard written checklists for that airplane. Checklists are usually compiled in a concise and abbreviated form as item and condition (for example, fuel—on), where the item to be checked is listed, followed by a statement of its desired condition. Explanations for actions are usually not included in the concise checklist, but may generally be found in the pilot’s operating handbook if required.

Vital checklists are best committed to memory so that they may be done quickly and efficiently, followed by confirmation using the printed checklist if required. Emergency checklists, such as the engine fire checklist, often have some items that should be memorized, since they may have to be actioned immediately, before there is time to locate the appropriate checklist and read it. These items are often referred to as memory items or phase-one items, and are often distinguished on checklists by bold type or by being surrounded with a box. The method of using checklists may be one of:

  • carrying out the items as the checklist is read; or
  • carrying out the items in full, followed by confirmation using the checklist.

Be sure to check back Thursday for more on preflight from our CFI as well as something interesting from SunState Aviation!

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Procedures and Airport Operations: Runway Incursions

Learn to reduce your risk of a runway incursion by following these simple FAA recommendations outlined in the Instrument Procedures Handbook (FAA-8083-16A).

On any given day, the NAS may handle almost 200,000 takeoffs and landings. Due to the complex nature of the airport environment and the intricacies of the network of people that make it operate efficiently, the FAA is constantly looking to maintain the high standard of safety that exists at airports today. Runway safety is one of its top priorities.

The FAA defines a runway incursion as:
“Any occurrence at an aerodrome involving the incorrect presence of an aircraft, vehicle, or person on the protected area of a surface designated for the landing and takeoff of aircraft.”

The four categories of runway incursions are listed below:
Category A—a serious incident in which a collision was narrowly avoided.
Category B—an incident in which separation decreases and there is a significant potential for collision that may result in a time critical corrective/evasive response to avoid a collision.
Category C—an incident characterized by ample time and/or distance to avoid a collision.
Category D—an incident that meets the definition of runway incursion, such as incorrect presence of a single vehicle/person/aircraft on the protected area of a surface designated for the landing and takeoff of aircraft but with no immediate safety consequences.

The below figure highlights several steps that reduce the chances of being involved in a runway incursion.

Fig 1-5


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Aerodynamics: Power

Today’s post is excerpted from the second edition of our textbook Aerodynamics for Aviators. This book features extensive illustrations and covers everything from the fundamentals of flight to high-speed flight, and includes an excellent compendium of formulae and equations used at all levels of aviation.

Aircraft aerodynamics involves the interaction of the four forces: lift, weight, thrust, and drag. The first basic issue to understand is the difference between propeller-driven aircraft power and jet engine thrust. Power is what a propeller-driven engine produces; thrust is what a jet engine produces. In a propeller-driven aircraft, the propeller—not the engine—is said to produce thrust. The thrust on a propeller-driven aircraft decreases with an increase in velocity; in a jet aircraft, thrust remains relatively constant with an increase in aircraft velocity.

(A) Thrust vs. velocity, jet engine; (B) Thrust vs. velocity, propeller-driven engine.

(A) Thrust vs. velocity, jet engine; (B) Thrust vs. velocity, propeller-driven engine.

Therefore, the power required curve versus the power available curve for a propeller driven aircraft and a jet aircraft will look different.

Power required versus power available (A) for a jet engine and (B) for a propeller-driven aircraft.

Power required versus power available (A) for a
jet engine and (B) for a propeller-driven aircraft.

Propeller Efficiency
Propeller efficiency is a measure of how much power is absorbed (transmitted) by the propeller and turned into thrust. In order to understand propeller efficiency, it’s helpful to start with a basic review of propeller principles. Propellers on aircraft consist of two or more blades and a hub. The blades are attached to the hub, and the hub is attached to the crankshaft on a piston-powered aircraft and to a gear reduction box on most turbo-prop aircraft. The propeller is simply a rotating wing that produces lift along the vertical axis. We call this lift force thrust.

Forces in flight.

Forces in flight.

Looking at a cross section of the propeller blade, we can see that it is similar to a cross section of an aircraft wing. The top portion of the blade is cambered like the top surface of a wing. The bottom portion is flat like the bottom surface of a wing.

Propeller cross section.

Propeller cross section.

The chord line is an imaginary line drawn from the leading edge of the propeller blade to the trailing edge of the propeller blade. Blade angle, measured in degrees, is the angle between the chord of the blade and the plane of rotation. The pitch of the propeller is usually designated in inches. A “78-52” propeller is 78 inches in length with an effective pitch of 52 inches. The effective pitch is the distance a propeller would move through the air in one revolution if there were no slippage. On a “78-52” propeller this distance would be 52 inches.

Propeller blade angle.

Propeller blade angle.

There are two types of propellers that can be installed on most general aviation aircraft: a fixed-pitch propeller or a controllable-pitch propeller. The fixed-pitch propeller is at the blade angle that will give it the best overall efficiency for the type of operation being conducted and for which the aircraft was designed. For most aircraft this would be a cruise setting. A controllable-pitch propeller allows the pilot to adjust the blade angle for the different phases of flight. On takeoff and climb out, a low pitch/high RPM setting is used. During cruise flight a high pitch/low RPM setting is generally used.

On the ground with the aircraft in a static condition, the propeller efficiency is very low because each blade is moving through the air at an angle of attack that produces a very low thrust to power ratio. This means that a lot of power is being used to sustain the engine and rotate the propeller while very little thrust is being produced. The propeller, unlike the wing, moves both rotationally and forward (dynamically). The angle at which the relative wind strikes the propeller blade is the AOA. This produces a higher dynamic pressure on the engine side, which in turn is called thrust. Thus thrust is the relationship of propeller AOA and blade angle.

Propeller blade angle with forward velocity.

Propeller blade angle with forward velocity.

Since an aircraft moves forward through the air, it is important that the pilot understands how forward velocity affects the AOA of the propeller. The figure above shows the propeller in a static condition on the ground. At this point the relative wind is opposing propeller rotation. As forward velocity increases, the relative wind moves closer to the chord line, decreasing the propeller AOA. This can easily be demonstrated in an aircraft with a fixed-pitch propeller by pitching up or down without changing power. When the aircraft is pitched down, RPM will increase as the relative wind moves closer to the chord line and the AOA is decreased. When the aircraft is pitched up, the RPM will decrease as the relative wind moves farther from the chord line and the AOA is increased.

Propeller efficiency is a ratio between thrust horsepower and brake horsepower. Brake horsepower (BHP) is the horsepower actually delivered to the output shaft. Brake horsepower is the actual usable horsepower. Thrust horsepower (THP) is the power that is imparted by the propeller to the air. Propeller efficiency is the relationship between brake horsepower and thrust horsepower. If the BHP of the engine is 200, the THP is less (20–40%). Some power is lost to turn the engine and propeller. Propeller efficiency usually varies between 50 and 80% on light general aviation aircraft.

The measure of efficiency is how much a propeller slips in the air. This is measured by the geometric pitch (theoretical) which shows a propeller with no slippage. Effective pitch is the distance that the propeller actually travels.

Propeller efficiency.

Propeller efficiency.

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Procedures and Airport Operations: Normal Landing

A good landing is most likely following a good approach, so aim to be well established in a stabilized approach with the airplane nicely trimmed by the time you reach short final, the last part of the approach. Short final for a training airplane may be thought of as the last 200 feet.

The landing starts with a flare commencing when the pilot’s eyes are about 15 feet above the runway. The pilot uses texture, height of peripheral objects, width of the runway and the perceived height of the horizon as cues to commence the flare and to judge the rate of rotation to achieve an almost level path over the runway. The landing is not complete until the end of the landing roll.

Once you reach the flaring height, forget the aim point because you will fly over and well past it before the wheels actually touch down. It has served its purpose and you should now look well ahead. Pick a point at the center of the far end of the runway. Transfer your visual attention to this point and slowly retard the throttle.

A normal landing is similar to the approach to the stall, with attitude being increased to keep the aircraft flying at the reducing airspeed. Touchdown will occur just prior to the moment of stall. Do not rush and try not to be tense. The aircraft will land when it is ready. This method of landing allows the lowest possible touchdown speed (significantly less than the approach speed), with the pilot still having full control.

The landing consists of four phases:

  • flare (or round-out);
  • hold-off;
  • touchdown; and
  • landing roll.

During the flare (round-out) the power is reduced and the nose is gradually raised to reduce the rate of descent. A small rate of sink is checked by a slight attitude change, a high rate of sink requiring a greater and quicker backward movement. A greater descent rate may require the pilot to add power momentarily to arrest the descent.

The hold-off should occur with the airplane close to the ground (with the wheels within a foot or so). The throttle is closed and the control column progressively brought back to keep the airplane flying a level path with the wheels just off the ground. If sinking, apply more back pressure; if moving away from the ground, relax the back pressure. The airspeed will be decreasing to a very low figure, but this is of no concern to you. You should be looking well ahead from the beginning of round-out until touchdown. Any sideways drift caused by a slight crosswind can be counteracted by lowering the upwind wing a few degrees and keeping straight with rudder.

On touchdown, the main wheels should make first contact with the ground (which will be the case following a correct hold-off ). The nose wheel will want to drop immediately but should be kept off the ground using the control column while the speed decreases. This may require a significant rearward pressure to allow it to touch gently.

Landing Roll
During the landing roll the airplane is kept straight down the centerline using rudder and the wings kept level with aileron. Look at the far end of the runway. The nose wheel is gently lowered to the ground before elevator control is lost. Brakes (if required) may be used once the nose wheel is on the ground. Remember that the landing is not complete until the end of the landing roll when the airplane is stationary or has exited the runway at taxiing speed.

For more on landing technique, and every maneuver required for certification, check out the brand new fifth edition of ThePilot’s Manual: Flight School (PM-1C).

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Regulations: First Solo Flight

You are able to fly solo when the instructor believes, with some confidence, that you can fly safely with a degree of consistency and you have mastered the presolo maneuvers defined in the regulations. Most important is evidence that you are taking control and responsibility for your own actions—that you are walking on your own two feet. Today’s post comes from the new fifth edition of The Pilot’s Manual: Flight School (PM-1C).

The instructor is looking to see you make corrections for inaccuracies without waiting to be told and without asking for instructions, responding to radio calls without question and saying what you intend to do rather than asking what is next. These are the signs of aviation maturity, of being in command. They are no different from other life skills, just applied at a higher altitude.

First solo is an unforgettable experience that you will remember and treasure all your life. When your instructor tells you to stop after turning off the runway, steps out of the airplane, secures the harness and then leaves you to your first solo flight, you are being paid a big compliment. Your instructor is confident that you can safely complete a solo traffic pattern. You have demonstrated sufficient awareness, skill and consistency to be trusted to take the aircraft up by yourself.

You may feel a little apprehensive (or very confident), but remember that the instructor is trained to judge the right moment to send you solo. Your instructor has a better appreciation of your flying ability than anybody (including you—especially you).

Your instructor will have observed your progress and have assessed your consistency, safety and predictability. It is not the occasional brilliant landing that is looked for, but a series of consistently safe ones. Your instructor will choose the conditions and the traffic so that they are not more demanding than you are used to.

You know instinctively when you are ready to fly solo. In some cases, you may feel you are ready before time. Your instructor knows when the time is right. Trust in that.

Your instructor will also advise the control tower that this is a first solo and the controller will keep a watchful eye open for this new fledgling. The controller will anticipate wind changes and try not to change the active runway while you are flying your first solo traffic pattern.

Presolo Written Exam
Before going solo, you must have passed a written examination administered and graded by the flight instructor who endorses your logbook for solo flight. The written examination will include questions on the applicable Federal Aviation Regulations, and the flight characteristics and operational limits of your airplane. By answering the review questions of each exercise during your training, you will be well prepared for the questions on the flight characteristics and operational limits of your airplane.

These next review questions prepare you for the regulations questions. They direct you into your current copy of the regulations to indicate the level of knowledge you require prior to going solo. Since regulation numbering changes from time to time, the part has been identified—for example, Part 91 and Part 61—but not the individual section, which you can easily find using the table of contents page in your book of regulations.

Fly your first solo traffic pattern in the same manner as you flew the pattern before the instructor stepped out. The usual standards apply to the takeoff, pattern and landing. Follow exactly the same pattern and procedures. Maintain a good lookout, fly a neat pattern, establish a stabilized approach and carry out a normal landing. Be prepared for better performance of the airplane without the weight of your instructor on board. If at any stage you feel uncomfortable, go around. Many students comment on how much better the airplane flies without an instructor and how much quieter it is!

Be in control. Do not be blown with the wind. The tower will try to avoid any interruptions or runway changes while you are airborne but, if there is a need for you to hold overhead the field or to change runway, then take your time, think through the best plan of action, ask for instructions if you are in doubt and then complete a normal pattern and landing.

If an emergency occurs, such as engine failure (and this is an extremely unlikely event), carry out the appropriate emergency procedure that you have been taught. If your radio fails simply complete the pattern and land normally. Be aware of other traffic. You have been taught to go around and it may happen even on your first solo. Simply complete another pattern.

Your flight instructor, when sending you solo, not only considers you competent to fly a pattern with a normal takeoff and landing, but also considers you competent to handle an abnormal situation. One takeoff, one pattern and one landing are the rites of passage to the international community of pilots.

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Aerodynamics: High Speed Flight

Today’s post comes from the Pilot’s Handbook of Aeronautical Knowledge (FAA-H-8083-25B).

In subsonic aerodynamics, the theory of lift is based upon the forces generated on a body and a moving gas (air) in which it is immersed. At speeds of approximately 260 knots or less, air can be considered incompressible in that, at a fixed altitude, its density remains nearly constant while its pressure varies. Under this assumption, air acts the same as water and is classified as a fluid. Subsonic aerodynamic theory also assumes the effects of viscosity (the property of a fluid that tends to prevent motion of one part of the fluid with respect to another) are negligible and classifies air as an ideal fluid conforming to the principles of ideal-fluid aerodynamics such as continuity, Bernoulli’s principle, and circulation.

In reality, air is compressible and viscous. While the effects of these properties are negligible at low speeds, compressibility effects in particular become increasingly important as speed increases. Compressibility (and to a lesser extent viscosity) is of paramount importance at speeds approaching the speed of sound. In these speed ranges, compressibility causes a change in the density of the air around an aircraft.

During flight, a wing produces lift by accelerating the airflow over the upper surface. This accelerated air can, and does, reach sonic speeds even though the aircraft itself may be flying subsonic. At some extreme angles of attack (AOA), in some aircraft, the speed of the air over the top surface of the wing may be double the aircraft’s speed. It is therefore entirely possible to have both supersonic and subsonic airflow on an aircraft at the same time. When flow velocities reach sonic speeds at some location on an aircraft (such as the area of maximum camber on the wing), further acceleration results in the onset of compressibility effects, such as shock wave formation, drag increase, buffeting, stability, and control difficulties. Subsonic flow principles are invalid at all speeds above this point.

The speed of sound varies with temperature. Under standard temperature conditions of 15 °C, the speed of sound at sea level is 661 knots. At 40,000 feet, where the temperature is –55 °C, the speed of sound decreases to 574 knots. In high speed flight and/or high-altitude flight, the measurement of speed is expressed in terms of a “Mach number”—the ratio of the true airspeed of the aircraft to the speed of sound in the same atmospheric conditions. An aircraft traveling at the speed of sound is traveling at Mach 1.0. Aircraft speed regimes are defined approximately as follows:

  • Subsonic—Mach numbers below 0.75
  • Transonic—Mach numbers from 0.75 to 1.20
  • Supersonic—Mach numbers from 1.20 to 5.00
  • Hypersonic—Mach numbers above 5.00

While flights in the transonic and supersonic ranges are common occurrences for military aircraft, civilian jet aircraft normally operate in a cruise speed range of Mach 0.7 to Mach 0.90.

The speed of an aircraft in which airflow over any part of the aircraft or structure under consideration first reaches (but does not exceed) Mach 1.0 is termed “critical Mach number” or “Mach Crit.” Thus, critical Mach number is the boundary between subsonic and transonic flight and is largely dependent on the wing and airfoil design. Critical Mach number is an important point in transonic flight. When shock waves form on the aircraft, airflow separation followed by buffet and aircraft control difficulties can occur. Shock waves, buffet, and airflow separation take place above critical Mach number. A jet aircraft typically is most efficient when cruising at or near its critical Mach number. At speeds 5–10 percent above the critical Mach number, compressibility effects begin. Drag begins to rise sharply. Associated with the “drag rise” are buffet, trim, and stability changes and a decrease in control surface effectiveness. This is the point of “drag divergence.”


VMO/MMO is defined as the maximum operating limit speed. VMO is expressed in knots calibrated airspeed (KCAS), while MMO is expressed in Mach number. The VMO limit is usually associated with operations at lower altitudes and deals with structural loads and flutter. The MMO limit is associated with operations at higher altitudes and is usually more concerned with compressibility effects and flutter. At lower altitudes, structural loads and flutter are of concern; at higher altitudes, compressibility effects and flutter are of concern.

Adherence to these speeds prevents structural problems due to dynamic pressure or flutter, degradation in aircraft control response due to compressibility effects (e.g., Mach Tuck, aileron reversal, or buzz), and separated airflow due to shock waves resulting in loss of lift or vibration and buffet. Any of these phenomena could prevent the pilot from being able to adequately control the aircraft.

For example, an early civilian jet aircraft had a VMO limit of 306 KCAS up to approximately FL 310 (on a standard day). At this altitude (FL 310), an MMO of 0.82 was approximately equal to 306 KCAS. Above this altitude, an MMO of 0.82 always equaled a KCAS less than 306 KCAS and, thus, became the operating limit as you could not reach the VMO limit without first reaching the MMO limit. For example, at FL 380, an MMO of 0.82 is equal to 261 KCAS.

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Procedures and Airport Operations: The Go-Around

Today we’re excited to announce a new fifth edition of our foundational textbook The Pilot’s Manual: Flight School (PM-1C). Flight School breaks down all the tasks required for Private and Commercial certification. Each chapter outlines the objective, consideration, application, technique, and airmanship of a maneuver as well as a visual explanation of the task and all of its steps. Today, we’ll share the PM-1C’s chapter on the go-around.


Raise the flaps in stages.

Raise the flaps in stages.

To describe:

  • the circumstances under which a go-around may be safer than a continued landing; and
  • the technique to transition from a powered approach with flaps (and landing gear) extended to a positive climb with flaps (and landing gear) retracted.

Why Go Around?
It may be necessary to perform a go-around for various reasons:

  • the runway is occupied by an airplane, a vehicle or animals;
  • you are too close behind an airplane on final approach that will not have cleared the runway in time for you to land;
  • the conditions are too severe for your experience (turbulence, wind shear, heavy rain, excessive crosswind, etc.);
  • your approach is unstable (in terms of airspeed or flight path);
  • you are not aligned with the centerline or directional control is a problem;
  • the airspeed is far too high or too low;
  • you are too high at the runway threshold to touch down safely and stop comfortably within the confines of the runway;
  • you are not mentally or physically at ease; and
  • a mishandled landing (balloon or bounce).
Going around.

Going around.

Effect of Flaps
Full flap causes a significant increase in drag. This has advantages in the approach to land: it allows a steeper descent path, the approach speed can be lower and the pilot has a better forward view. Full flap has no advantages in a climb: in fact establishing a reasonable rate of climb may not be possible with full flap extended. For this reason, when attempting to enter a climb from a flapped descent, consideration should be given to raising the flap. It should be raised in stages to allow a gradual increase in airspeed as the climb is established.

Establish a Descent for a Practice Go-Around
Follow the usual descent procedures and lower an appropriate stage of flap. Initially, it may be desirable to practice the go-around maneuver with only an early stage of flap extended (or perhaps none at all), as would be the case early in the approach to land. A go-around with full flap requires more attention because of the airplane’s poorer climb performance and generally more pronounced pitching moment as the power is applied and flaps retracted.

Initiating a Go-Around
A successful go-around requires that a positive decision be made and positive action taken. A sign of a good pilot is a decision to go around when the situation demands it, the maneuver being executed in a firm, but smooth manner. The procedure to use is similar to that already practiced when entering a climb from a flapless descent: power, attitude, trim (PAT). The additional consideration is flap, which is raised when the descent is stopped and the climb (or level flight) is initiated.

To initiate a go-around, move the carburetor heat to cold and smoothly apply full power (counting 1-2-3 fairly quickly is about the correct timing to achieve full power). Be prepared for a strong pitch-up and yawing tendency as the power is applied. Hold the nose in the desired climb attitude for the flap that is set, balance and then trim. The initial pressure and retrimming may be quite significant, especially with full flap.

Full flap creates a lot of drag and only marginal climb performance may be possible. In this case level flight might be necessary while the flap setting is initially reduced. If only partial flap is extended, a reasonable climb can be entered without delay.

The go-around.

The go-around.

As the airplane accelerates to an appropriate speed, raise the flap in stages and adjust the pitch attitude to achieve the desired speeds and climb performance. Trim as required.

Make a positive decision to go-around, then perform it decisively. Exert firm, positive and smooth control over the airplane. Firm pressure must be held on the control column and rudder pedals when the power is applied. Correct trimming will assist you greatly. Ensure that a safe airspeed is achieved before each stage of flap is raised. Once established comfortably in the climb-out, advise the air traffic service unit (and the other aircraft in the traffic pattern) by radio that you are going around.

It is usual, once established in the go-around, to move slightly to one side of the runway so that you have a view of airplanes that may be operating off the runway and beneath you. The dead side, away from the pattern direction, is preferred. However, stay on the centerline if there are parallel runways.

Following the go-around, delay turning onto crosswind leg until at least at the upwind end of the runway to avoid conflicting with other traffic in the pattern.

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Human Factors: Night Vision Adaptation

Flying at night? Several things can be done to help with the dark adaptation process and to keep a pilot’s eyes adapted to darkness. Some of the steps pilots and flight crews can take to protect their night vision are described in this excerpt from the Pilot’s Handbook of Aeronautical Knowledge (FAA-H-8083-25B).

If a night flight is scheduled, pilots and crew members should wear neutral density (N-15) sunglasses or equivalent filter lenses when exposed to bright sunlight. This precaution increases the rate of dark adaptation at night and improves night visual sensitivity.

Oxygen Supply
Unaided night vision depends on optimum function and sensitivity of the rods of the retina. Lack of oxygen to the rods (hypoxia) significantly reduces their sensitivity. Sharp clear vision (with the best being equal to 20–20 vision) requires significant oxygen especially at night. Without supplemental oxygen, an individual’s night vision declines measurably at pressure altitudes above 4,000 feet. As altitude increases, the available oxygen decreases, degrading night vision. Compounding the problem is fatigue, which minimizes physiological well being. Adding fatigue to high altitude exposure is a recipe for disaster. In fact, if flying at night at an altitude of 12,000 feet, the pilot may actually see elements of his or her normal vision missing or not in focus. Missing visual elements resemble the missing pixels in a digital image while unfocused vision is dim and washed out.

For the pilot suffering the effects of hypoxic hypoxia, a simple descent to a lower altitude may not be sufficient to reestablish vision. For example, a climb from 8,000 feet to 12,000 feet for 30 minutes does not mean a descent to 8,000 feet will rectify the problem. Visual acuity may not be regained for over an hour. Thus, it is important to remember, altitude and fatigue have a profound effect on a pilot’s ability to see.

High Intensity Lighting
If, during the flight, any high intensity lighting areas are encountered, attempt to turn the aircraft away and fly in the periphery of the lighted area. This will not expose the eyes to such a large amount of light all at once. If possible, plan your route to avoid direct over flight of built-up, brightly lit areas.

Flightdeck Lighting
Flightdeck lighting should be kept as low as possible so that the light does not monopolize night vision. After reaching the desired flight altitude, pilots should allow time to adjust to the flight conditions. This includes readjustment of instrument lights and orientation to outside references. During the adjustment period, night vision should continue to improve until optimum night adaptation is achieved. When it is necessary to read maps, charts, and checklists, use a dim white light flashlight and avoid shining it in your or any other crewmember’s eyes.

Airfield Precautions
Often time, pilots have no say in how airfield operations are handled, but listed below are some precautions that can be taken to make night flying safer and help protect night vision.

  • Airfield lighting should be reduced to the lowest usable intensity.
  • Maintenance personnel should practice light discipline with headlights and flashlights.
  • Position the aircraft at a part of the airfield where the least amount of lighting exists.
  • Select approach and departure routes that avoid highways and residential areas where illumination can impair night vision.
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Navigation: Basic Radio Principles

A radio wave is an electromagnetic (EM) wave with frequency characteristics that make it useful. The wave travels long distances through space (in or out of the atmosphere) without losing too much strength. An antenna is used to convert electric current into a radio wave so it can travel through space to the receiving antenna, which converts it back into an electric current for use by a receiver. Today, we’ll take a look at an excerpt from the Instrument Flying Handbook (FAA-H-8083-15B).

How Radio Waves Propagate
All matter has a varying degree of conductivity or resistance to radio waves. The Earth itself acts as the greatest resistor to radio waves. Radiated energy that travels near the ground induces a voltage in the ground that subtracts energy from the wave, decreasing the strength of the wave as the distance from the antenna becomes greater. Trees, buildings, and mineral deposits affect the strength to varying degrees. Radiated energy in the upper atmosphere is likewise affected as the energy of radiation is absorbed by molecules of air, water, and dust. The characteristics of radio wave propagation vary according to the signal frequency and the design, use, and limitations of the equipment.
Ground Wave
A ground wave travels across the surface of the Earth. You can best imagine a ground wave’s path as being in a tunnel or alley bounded by the surface of the Earth and by the ionosphere, which keeps the ground wave from going out into space. Generally, the lower the frequency, the farther the signal travels.

Ground waves are usable for navigation purposes because they travel reliably and predictably along the same route day after day and are not influenced by too many outside factors. The ground wave frequency range is generally from the lowest frequencies in the radio range (perhaps as low as 100 Hz) up to approximately 1,000 kHz (1 MHz). Although there is a ground wave component to frequencies above this, up to 30 MHz, the ground wave at these higher frequencies loses strength over very short distances.

Sky Wave
The sky wave, at frequencies of 1 to 30 MHz, is good for long distances because these frequencies are refracted or “bent” by the ionosphere, causing the signal to be sent back to Earth from high in the sky and received great distances away. Used by high frequency (HF) radios in aircraft, messages can be sent across oceans using only 50 to 100 watts of power. Frequencies that produce a sky wave are not used for navigation because the pathway of the signal from transmitter to receiver is highly variable. The wave is “bounced” off of the ionosphere, which is always changing due to the varying amount of the sun’s radiation reaching it (night/day and seasonal variations, sunspot activity, etc.). The sky wave is, therefore, unreliable for navigation purposes.

For aeronautical communication purposes, the sky wave (HF) is about 80 to 90 percent reliable. HF is being gradually replaced by more reliable satellite communication.

Space Wave
When able to pass through the ionosphere, radio waves of 15 MHz and above (all the way up to many GHz), are considered space waves. Most navigation systems operate with signals propagating as space waves. Frequencies above 100 MHz have nearly no ground or sky wave components. They are space waves, but (except for global positioning system (GPS)) the navigation signal is used before it reaches the ionosphere so the effect of the ionosphere, which can cause some propagation errors, is minimal. GPS errors caused by passage through the ionosphere are significant and are corrected for by the GPS receiver system.

Space waves have another characteristic of concern to users.Space waves reflect off hard objects and may be blocked if the object is between the transmitter and the receiver. Site and terrain error, as well as propeller/rotor modulation error in very high omnidirectional range (VOR) systems, is caused by this bounce. Instrument landing system (ILS) course distortion is also the result of this phenomenon, which led to the need for establishment of ILS critical areas.

Generally, space waves are “line of sight” receivable, but those of lower frequencies “bend” somewhat over the horizon. The VOR signal at 108 to 118 MHz is a lower frequency than distance measuring equipment (DME) at 962 to 1213 MHz. Therefore, when an aircraft is flown “over the horizon” from a VOR/DME station, the DME is normally the first to stop functioning.

Disturbances to Radio Wave Reception
Static distorts the radio wave and interferes with normal reception of communications and navigation signals. Lowfrequency airborne equipment, such as automatic direction finder (ADF) and LORAN (LOng RAnge Navigation), are particularly subject to static disturbance. Using very high frequency (VHF) and ultra-high frequency (UHF) frequencies avoids many of the discharge noise effects. Static noise heard on navigation or communication radio frequencies may be a warning of interference with navigation instrument displays. Some of the problems caused by precipitation static (P-static) are:

  • Complete loss of VHF communications.
  • Erroneous magnetic compass readings.
  • Aircraft flying with one wing low while using the autopilot.
  • High-pitched squeal on audio.
  • Motorboat sound on audio.
  • Loss of all avionics.
  • Inoperative very-low frequency (VLF) navigation system.
  • Erratic instrument readouts.
  • Weak transmissions and poor radio reception.
  • St. Elmo’s Fire.
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Regulations: Supplemental Oxygen

We’re talking regulations this week. Take a look at what we’ve covered so far. Today, we’ll go over the rules regarding supplemental oxygen under 14 CFR Part 91 with an excerpt from The Pilot’s Manual: Ground School (PM-2C), which has a useful chart to clarify the regulation.

Crew oxygen requirements for operations under Part 91 Regulations:

  • crew members are not required to use oxygen up to a cabin pressure altitude of 12,500 feet MSL;
  • at cabin pressure altitudes above 12,500 feet up to and including 14,000 feet, the required minimum flight crew may fly without supplemental oxygen for up to 30 minutes. Supplemental oxygen must be provided and used for at least the time in excess of 30 minutes at these cabin pressure altitudes; and
  • at cabin pressure altitudes above 14,000 feet, the required minimum flight crew must be provided with and use supplemental oxygen during the entire time at those cabin altitudes.

For passenger oxygen requirements, at cabin pressure altitudes above 15,000 feet, each occupant (flight crew and passengers) must be provided with supplemental oxygen.

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