Aircraft Inspections

The aircraft owner is responsible for ensuring that the aircraft is properly maintained and the the maintenance records show that the proper maintenance has been done.

The pilot is responsible for ensuring that the aircraft is in a safe condition for flight at the time the aircraft is flown.

Most aircraft are required to have an annual inspection although some aircraft manufacturers have FAA approval to chase inspections as opposed to annual inspections.

Annual Inspections

Annual inspection must be performed every 12 calendar months and it expires on the last day of the month that is was inspected.

These annual inspections are documented in the aircraft’s maintenance records and include the airframe log book, engine log book, and propeller log book.

The annual inspection is verified by a maintenance release for the aircraft’s return to service and well as a sign off by a maintenance tech with an Inspection Authorization (IA) from the FAA.

100 Hour Inspections

For aircraft that are used for hire such as charter flights or flight instruction, there is an inspection that must be performed every 100 engine hours (tach time). This may be exceeded by 10 hours to get the aircraft to the inspection point but not to perform flight training although the next inspection will still be required 100 hours from the previous time it was due.

These inspections must be verified by a maintenance release for the aircraft’s return to service, a sign off by a maintenance technician with an Airframe and Powerplant (A & P) license ( the 100 hour inspection does not need to be signed off by a IA).


The transponder must ben tested and inspected within the previous 24 calendar months meaning it expires on the last day on the month, 24 months later. Must be tested and inspected by a certified avionics technician. The transponder must be tested and inspected in order to use it anywhere. If you turn it on, it must have been tested and inspected within the past 24 months regardless of the air space you are in. This must be documented in the aircraft’s maintenance records.

Altimeter and Pitot Static System

The Altimeter and Pitot-Static System must be tested and inspected within the last 24 calendar months and is generally done at the same tome as the transponder. This is required in order to fly in controlled airspace under IFR (instrument flight rules)


The ELT battery must be inspected within the last 12 calendar months and the ELT battery must be replaced or recharged when the transponder has been in used for more than 1 cumulative hour or 50% of the battery’s useful life has expired (usually about every 2 years)

Airworthiness Directives

In addition to the above inspection items, Airworthiness Directives (AD) are legally required to be completed. The Airworthiness Directive is a document from the FAA that adds an inspection or maintenance action not covered under the annual inspection or 100 hour inspections. These are usually issued due to a problem identified or discovered in the field. These are mandatory and may require a one time inspection or continuous/periodic inspection and must be added to the aircraft’s maintenance records to indicate compliance with the AD.



Required Equipment

Certain instruments and equipment must be installed and operating for flight. Airplanes such as the Cessna 172 Skyhawk or Cessna 162 Skycatcher are manufactured with instruments, displays or other equipment installed. Other approved instruments or equipment may be added later and an airplane may still be airworthy with some of the original items removed or non-operational. The Pilot in Command (PIC) has the responsibility to determine airworthiness based on the Manufacture’s equipment list or the minimum instruments and equipment required by FAR 91.205

The Manufacturer’s Equipment list which is located in the Weight and Balance section of the FAA-Approved Airplane Flight Manual (AFM) or contained in the Pilot’s Operating Handbook (POH) will indicate the items approved by the FAA-approved type certificate.

Minimum instrument and equipment required by FAR 91.205 will set for the the different flight conditions for day, night, Visual flight rules (VFR) and Instrument Flight Rules (IFR)

Required For Visual Day Flying

There are basic requirements for visual flying which include instruments for how high, how fast, and which direction including:

  • Altimeter
  • Airspeed Indicator
  • Magnetic Direction Indicator
    • a simple “wet” (“whiskey”) magnetic compass meets the requirement
    • most airplanes will have a gyroscopically stabilized heading indicator as either a stand along instrument or integrated into the electronic flight display

Instruments for indicating engine performance and operation:

  • Tachometer
  • Oil Pressure Gauge
  • Oil Temperature Gauge
  • Fuel Gauge(s)

Safety Equipment for the pilot and passengers:

  • seat belt for each occupant
  • shoulder harness in front seat (if manufactured after 1978 although older airplane may have retrofit)
  • emergency locator transmitter (ELT)
  • anti-collision light system (red or white & required if manufactured after March 1996)
Required For Visual Night Flying
  • all instruments required for day flights
  • position lights
    • red – wingtip
    • green – right wingtip
    • white – tail
  • anti-collision light system (older airplanes not requiring it for day must have for night)
  • adequate electrical source for all installed electrical equipment and radio equipment
  • spare fuses if the electrical system uses fuses (Cessna 172 Skyhawk and 162 Skycatcher use circuit breakers instead of fuses)
Other Possible Requirements
  • landing gear position indicator (for retractable landing gear)
  • coolant temperature gauge (for liquid cooled engines)
  • manifold pressure gauge (constant speed propellers, blade pitch can be changed)
  • oxygen equipment (high altitude flying)
Determine the equipment on your airplane

the equipment list is located in the Weight & Balance section of the AFM which identifies four categories of flight equipment RSOA

  • “R” – Required equipment (must be installed and operable)
  • “S” – Standard equipment (normally installed but not required)
  • “O” – Optional equipment (is neither standard nor required)
  • “A” – Additional equipment (added after aircraft certification)

Another place to look for the list of required equipment for your specific operation is in the Limitations section of the FAA approved Airplane Flight Manual (AFM) or Pilot’s Operating Handbook (POH) for the (KOEL) Kinds of Operation Equipment List. This will tell you the specific instruments that need to be operating for your flight conditions such as day or night VFR (visual flight rules).

Inoperative Instruments and Equipment

In some cases the aircraft can still fly even if some of the equipment is not working properly. The FAA has defined rules for inoperative instruments and equipment in FAR 91.213.

The first step in determining if you can fly or not is to check to see if your aircraft has a Minimum Equipment List (MEL) which is a list of equipment that can be inoperative, yet legally able to fly provided the instructions in the MEL are followed. A MEL it obtained through the FAA. Most MELs are for large aircraft or a fleet of aircraft such as a secondary coffee maker in a Boing 757.

Most small general aviation aircraft do not have a MEL but the next step is to look at the Kinds of Operations Equipment List in the Limitations section of the AFM/POH.

You will need to determine if the inoperative flight equipment is listed as required for your flight. If it is required, you cannot fly until it is fixed. If it is not required, then proceed to the list of equipment in the regulations for the type of flight being conducted (FAR 91.205).

If the inoperative equipment is not listed in FAR 91.205, then it is not required for your flight but you must deactivate the equipment and placard/label the equipment a INOP (inoperative) before you fly.




Certificates and Documents

Required documentation for the aircraft prior to flight.

The owner or operator of an aircraft is required by the FAA to ensure that the aircraft is maintained in a safe condition which includes the completion of mandatory aircraft inspections.

The Pilot in Command is responsible for determining that the airplane is in safe condition for flight also know as “airworthy”.

An aircraft is considered “airworthy” if the following conditions are met:

  • airplane passes the preflight inspection which is performed before the flight
  • all of the required documents are on board (visual inspection)
  • the aircraft’s inspections are all up-to-date (verify in logbook)
  • all airworthiness directives (ADs) are complied with (compare logbook with list of current ADs

As the Pilot in Command (PIC), it is your responsibility to determine that the inspections have all been complete. Maintenance records will have the appropriate entries.

An easy way to remember which documents are required is to remember AROW which is:

  • Airworthiness Certificate
  • Registration Certificate
  • Operating Limitations
  • Weight and Balance information

Airworthiness Certificate

The Airworthiness Certificate is the aircraft’s “birth certificate and must be displayed in the aircraft so that it is visible to the passengers and or crew at the entrance to the cockpit or cabin whenever the aircraft is operated.

The date of issue is when the FAA first certifies the aircraft at the factory. Can be reissued if lost or destroyed.

The Airworthiness Certificate remains valid as long as the aircraft is operated and maintained according to the regulations and as long as it is registered in the U.S. There is no expiration date.

The registration number on the certificated begins with N for aircraft registered in the US and the N must match the number on the aircraft.

The Serial number is assigned by the manufacturer and is different from the registration number. The data plate on the exterior of the aircraft must match the Airworthiness Serial Number.

Registration Certificate

The Registration certificate is issued by the FAA and lists the owner’s name and address. It but be carried in the aircraft at all times and must match the N number on the Airworthiness Certificate. For US operations, a duplicate, pink copy of the Aircraft Registration Application may be used. Registration certificates are issued for 3 years and the expiration date is shown on the front.

Operating Limitations

The operating limitations are found in the FAA approved Airplane Flight Manual (AFM) for aircraft manufactured after 1979. The AFM for the Cessna 172 Skyhawk and the 162 Skycatcher are located in the Pilot’s Operating Handbook (POH). They can also be found in the owner’s manuals or similar documents for aircrafts manufactured before 1979.

Operating Limitations may also be found on placards in the cockpit for all airplanes as well as on markings on the instrument panel as detailed in the Pilot Operating Handbook.

Weight and Balance Information

The weight and balance information is used for determining that the aircraft is within the maximum gross weight and center of gravity position limitations.

In order to ensure that the aircraft is safely loaded, you need two types of information. First, you need to know the empty airplane’s weight and center of gravity location.

  • look at the Aircraft Wright Record for the aircraft (by serial number)
  • found on a sheet attached to the Pilot’s Operating Handbook
    • due of weighing or latest calculation
    • basic empty weight
    • location of the center of gravity

The Pilot’s Operating Handbook includes a list of all equipment installed in the aircraft. The empty weight and center of gravity must be adjusted anytime installed equipment id removed or any additional equipment is added.

You will also need to determine the total weight and the center of gravity factoring in the weight of the pilot, passengers, baggage and fuel. There is a form for helping to make this calculation in the Weight and Balance section of the Pilot’s Operating Handbook for your aircraft or the generic PIM (Pilot Information Manual) for this make and model. Be careful to use the actual empty weight for your particular aircraft and not the sample provided in the PIM.

Additional Equipment

Sometimes, specialized equipment requires that additional documents are kept with the aircraft such as the G1000 Cockpit Reference Guide which is required for all G1000 equipped Cessna 172 Skyhawks.

International Flight Requirements

For flights involving international borders, the aircraft must also have a Radio Station License, which would add an additional R in ARROW for easy memory. The effective Aircraft Registration Certificate is required as opposed to just tabuing the pink application.

FAA Ramp Checks

Since the FAA has the responsibility and authority to make sure that aircrafts using national airspace are airworthy, FAA Aviation Safety Inspectors may randomly request to see pilot and aircraft documentation. This check/inspection is referred to as a “ramp check”. If this happens. always remember to be polite and courteous just as you would any other government official, police officer, DMV representative, you get the point, be nice.


Slow Flight

The slower an aircraft flies, the greater the angle of attack is required and the slower an aircraft flies, the more induced drag increases.

The faster an aircraft flies, the more parasitic drag increases.

The total drag is the combination of induced drag and parasitic drag.

Induced Drag

The induced drag is created from the production of lift, decreases as airspeed increases and increases with higher angles of attack.

Parasitic Drag

Parasitic drag increases as airspeed increases. Parasitic drag is a combination of the following:

Form Drag is created as a result of the body of the aircraft going through the air and affected by the size and shape of the aircraft along with any object’s on its surfaces.

Interference Drag is created as a result of the vortices that form where two surfaces of the airplane join together at a sharp angle such as where the wings meet the fuselage.

Skin Friction Drag is created as a result of the friction between the air and the surface of the airplane.

Drag Curve

The bottom of the drag curve is the speed that has the least drag (requiring the least power & provides maximum endurance) as well as provides the best glide angle.

The area to the bottom left of the drag curve is know as the “region of reverse command” and also called the “back side of the power required curve”.

When operating in the “region of reverse command” range, it takes more and more power to fly slower and slower. This is reverse of normal which is why this area is called the “region of reverse command”.

Also, speed is unstable in this “region of reverse command”e  – if the aircraft gets a little slow, it will continue to get slower and slower. – if the aircraft gets a little fast, it will continue to get faster and faster.

Operating in the range above is considered to be in “Slow Flight”

Slow Flight

When in flow flight, less air flows over the control surfaces which make them less effective.

You can tell when you are in slow flight due to the feel of the controls at slow speeds and the sound of the air flowing over the aircraft.

Learning how to control the aircraft in these speeds prepares for landing.

When flying in slow flight, you can used a combination of Pitch and power to control the airplane while thinking that pitch controls airspeed – forward pressure to increase speed and back pressure on the control wheel to reduce speed.

For slow flight, power controls altitude whereas increased power increases altitude and decreasing power reduces altitude.

Also for slow flight right rudder will need to be used due to slow speeds and higher power. Trim is used to relieve pressure.

Slow Flight = Low Airspeed -+ High Angle of Attack + High Power Setting -= Maintain Altitude


Learning Slow Flight will help to practice approaches and landing at lower airspeeds.

Slow flight helps build on the skills for straight and level flight, climbs, turns and descents.

To start slow flight,

  • perform the pre-maneuver checklist,
  • pick a visual reference point,
  • note the current heading and altitude then
  • reduce power to approximately 1500 RPM,
  • add a little back pressure on the control wheel to hold altitude
  • add in trim to help relieve control pressure
  • add power when slightly above your target airspeed of approx. 50-60 knots
  • increase the power to approximately 1700-21 RPM (as appropriate to maintain altitude)
  • use right rudder
  • ensure power setting and trim are set to hold altitude

When in slow flight, demonstrating the four fundamentals of flight will be shown by

  • Straight and Level
    • use pitch to control airspeed
    • Use power to control altitude
  • Turns
    • a 90 degree turn to the left using no more than 15 degrees of bank(note a landmark and initial heading & if needed, set bug)
    • a 90 degree turn to the right (adding power, more right rudder pressure and back pressure in turns)
  • Climbs
    • Note a heading reference
    • apply full power and right rudder
    • pitch to maintain around 55 knots
    • climb approximately 200 feet
    • reduce power to momentarily level off
  • Descents
    • reduce power to 1500 RPM or idle as desired
    • reduce right rudder pressure
    • pitch to maintain around 55 knots
    • descent approximately 200 feet
    • add power to the original setting required to maintain straight and level flight
    • increase right ridder pressure
    • momentarily level off

Once demonstrated, recover from the maneuver by

  • adding full power
  • increasing right ridder pressure
  • maintain altitude
  • gain airspeed
  • reduce the flap settings

Once at normal cruise speed

  • reduce power back to the normal cruise power setting
  • reduce right rudder pressure

Wow. that’s a lot of information.

Minimum Controllable Airspeed

The “minimum controllable airspeed” is the speed at which a stall will result if there is any additional increase in the angle of attack or reduction of power.

When performing slow flight, the stall warning horn may sound if you are flying at the slowest airspeed possible also known as the “minimum controllable air speed”. This stall warning will sound when at 5-10 knots above stall in all flight conditions.

Load Factor While Turning in Slow Flight

If practicing slow flight and add bank, the wings will have an increased load factor. In order to prevent a stall or loss of altitude, a small amount of power  and back pressure on the control wheel will need to be added to compensate. Sicne power will be added, right rudder pressure will need to increase.

When bank is increased in a level turn, the stall speed increases and the safety margin between stall speed and the actual speed is less when bank is increased.

Then turning in slow flight it is best to use shallow turns of around 15 degrees usually to avoid an accidental stall.

A good rule of thumb is to avoid more than 30 degrees of bank when within 1000 of the ground when in the traffic pattern.









Attitude and Airspeed

Determining the airspeed, vertical speed and altitude.

G1000 Electronic Flight Display

The airspeed indicator is shown on the left side in the form of a color-coded vertical tape.

White = flap operating range

Green = Normal Operating Range

Yellow – Caution Range

Red & White (Barber Pole @ the top of the tape) = Never Exceed Range

Red (bottom of the tape) = Low Speed awareness.

V Speeds List

  • VSO  – Stall wooed in landing gear (with full flaps & gear down if it is retractable)
  • VS1  – Stall speed in clean configuration (no flaps extended)
  • VR  – Rotation Speed (Transition from takeoff roll to takeoff climb)
  • VG  – Best Glide speed (most amount of lift with the least amount of drag)
  • VX  – Best Angle of Climb (most altitude for a given distance)
  • VY  – Best Rate of Climb (most altitude for a given time)
  • VFE  – Maximum Flaps Extended speed for full flaps ( exceeding this speed with the flaps extended could cause damage to the flaps or wing)
  • VNO  – Maximum structural cruising speed (do not exceed this speed except in smooth air and then only with caution)
  • VNE  – Never exceed speed (Exceeding this could compromise the structural integrity and the aircraft)

Analog Air Speed Indicator

The analog air speed indicator has colored arcs showing the ranges that are marked on the face ion the instrument.

White arc = starts at VSO  and ends at  VFE

Green arc = starts at VS1 and ends at VNO

Yellow arc = starts at VNO and ends at VNE


On the digital G1000 electronic flight display, the altitude is shown on the right side in the form of a vertical tape. It is marked in 20 foot increments. The knob is adjusted by using the barometric pressure (BARO) knob to set the local altimeter setting in the barometric pressure window. The airport elevation is set by rotating the BARO knob until the airport elevation is set in the altitude window.

An analog altimeter is set by rotating the adjustment knob to the local altimeter setting in the barometric pressure window. This can also set the airport elevation by adjusting the hands of the instrument display to reflect the airport elevation.

To calculate the height above ground level AGL, subtract the elevation of the terrain from the altitude indicated on the flight display or analog instrument.

Reading the Altimiter

There are three hands on the altimeter of different sized. Small, medium and large. The smallest represents tens of thousands, the middle or medium represents thousands and the larges represents hundreds.

To read them, read the each of them together rhino add all of the readings. If a hand is between number, round it to the lowest just as you would a watch or clock.

Read tens of thousands first, then thousands then hundreds. Each tick of the hundreds (largest hand) represents 20 feet.

Vertical Speed Indicator

The “vertical speed indicator” (VSI) displays the aircraft’s rate of climb or descent.

On an electronic flight display such as there G1000, the VSI is shown to the right of the altimeter tape and uses a non-moving tape label at 1000 and 2000 feet per minute (FPM) with minor tick marks every 500 feet per minute (FPM)

On an analog instrument, there is a needle which is marked in 100 foot increments.





The “heading” is the direction the aircraft is headed in relative to magnetic north (not true north).  The compass aligns with the earth’s magnetic field.

Headings are expressed in “degrees” clockwise from magnetic north where a circle is 360 degrees.

North is 0 degrees, commonly referred to as 360 degrees.

East is 90 degrees.

South is 180 degrees

West is 270 degrees.

When expressing a heading, you will pronounce all three numbers adding in  a zero in front for any one or two digit numbers. For example: (005) zero zero 5 degrees or (010) zero one zero, or (215) two one five.

Non Electronic Flight Display

For aircraft non-electric flight displays, the display will usually have a heading indicator which is gyroscopically stabilized to avoid errors in the magnetic compass due to turning or accelerating/decelerating.

Matching the heading indicator to the compass

Start by reading the current heading in the compass under the lubber line while steady and not turning, accelerating or decelerating. Then set the heading indicator to that setting by pushing in the adjustment knob and rotating the compass card to the appropriate heading. Over time, the heading indicator will need to be adjusted to account for errors, so make adjustments about every 15 minutes.

Electronic Flight Display

The electronic flight display will show the current heading in relation to magnetic north. which is stabilized to avoid errors. The heading information comes from a remote magnetometer.

Electronic and Non Electronic flight displays are equipped with a “heading bug” which can be set to the desired setting by turning the HDG knob (or knob on the instrument cluster).

This can also be set to the runway heading before takeoff to ensure you ar eon the proper runway or to the direction the local winds are from during taxi as a reminder for aileron and elevator corrections needed to compensate for the wind during taxi.

Magnetic Compass should be checked every flight for proper fluid and level and is required to be inspected every 12 months as part of the annual inspection.


Comparing Outside View to Instruments

When flying an airplane, it is important to not only look at the instruments to get their readings, but to look outside as well. It is important to get in the habit of looking outside as much as possible.

By looking outside, you will be able to see the position of the aircraft in relation to the surrounding areas and horizon as well as to identify and avoid any traffic.

The flight display and/or instrument panel should be looked at only briefly as needed and to confirm what you see outside, not different than when driving an automobile.

Attitude – the position of the nose and wingtips in relation to the horizon.

The attitude of the aircraft can be determined by developing a sight picture which is basically, the outside view in relation to your airplane. This “sight picture” should be memorized when maintaining a level attitude.

Flight Display – The attitude indicator on the flight display will tell you the pitch of the aircraft in relation to the horizon (marked in 5 degree increments for mechanical and 2.5 degree increments for electronic indicators) as well as the bank in relation to the horizon (marked in 10 degree increments for the first 30 degrees of bank.

The flight display also has a slip/skid indicator that shows if additional rudder pressure is required.

G-1000 Equipped Aircraft Turn Coordinator

If the aircraft is equipped with a G1000 flight display, there will be a visible triangle that indicates the bank of the aircraft under which will be a horizontal line. This horizontal line should be centered and if it shows to be on the left, then add left rudder. If the horizontal line shows on the right, add right rudder pressure.

Analog Turn Coordinator

On an analog turn coordinator, there will be a ball that should be centered if no rudder pressure is required. If the ball is to the right of center, add right rudder pressure and if the ball is to the left, add left rudder pressure.




Stability – Straight and Level flying

One characteristic of an aircraft is that it is stable about the lateral axis (runs wingtip to wingtip). This is known as “pitch stability” or “longitudinal stability”.

If the nose drops in flight due to turbulence of bumping the controls, the aircraft will be in a “nose-low” attitude (nose goes down). Because the nose is going down, the wings will have a lesser angle of attack (pointing down) which will increase airspeed.

As airspeed increases, more airflows over the horizontal stabilizer in which air pushes the tail downward. This downward force on the tail pushes the nose up resulting in the aircraft returning to climb.

Since the aircraft is climbing, the airspeed decreases and thus, less air is flowing over the horizontal stabilizer and the pattern is repeated until the aircraft returns to its original airspeed and altitude.

The first time the nose comes up in this pattern is called “Positive Static Stability

The repeated nose up over time during this pattern is called “Positive Dynamic Stability

In order to have dynamic stability, the aircraft must first have positive static stability in which the aircraft initially pitches up in the series of the pattern.

There are three different terms for “stability”

Positive Static Stability

Aircraft returns to its original position.

Neutral Static Stability

Aircraft stays where is is displaced to meaning that the aircraft stays & holds in the disturbed position.

Negative Static Stability

The aircraft continues in the direction that it is being displaced and continues in the direction of the disturbance.

The Cessna 172 Skyhawk is designed to be inherently stable in that the aircraft will return to its original position if disturbed. This is said to have positive and dynamic stability.

Longitudinal (Pitch) Stability

The Longitudinal or Pitch Stability is determined by both the center of gravity as well as the center of lift. In the Cessna 172 Skyhawk, the center of gravity is located in front of the center of lift which makes it stable. This helps keep the nose of the aircraft from pitching down and there is a slight downward force on the tail which helps to keep the airplane stable regardless of pitch and speed.

When the aircraft is disturbed in flight and begins to “dive”, it will pick up airspeed which increases the downward force on the tail. This downward force causes the tail to go down and the nose up, ultimately balancing out and returning the aircraft to its original speed.

The similar effect is true for the opposite. When the aircraft encounters a disturbance that causes the aircraft nose to pitch up, the force on the tail is decreased and the tail will go up, causing the nose to go down. This pattern is repeated over several oscillations until the aircraft returns to its original speed.

Testing the Level Flying Attitude

In order to test the airplane’s ability to return to a level flight, first make sure the aircraft is trimmed for level flight. Once trimmed, briefly pull back on the control wheel which will cause the nose to go up and begin a series of dampening oscillations. Ultimately the aircraft will return to level flight.


Airflow over the horizontal stabilizer and elevator creates an opposite lift and acts to push the tail downward in order to balance the lift produced by the wings. The more speed and airflow, the greater the downforce on tail so pushing the control stick forward at higher speeds will counteract this downforce and bring the nose down. Tail down =nose up.

Center of Gravity

The further forward the center of gravity is in comparison to the center of lift, the more stable the aircraft is

The further back (aft) the center of gravity is, the less stable the aircraft is.

If the aircraft is loaded so that the center of gravity is too far back (rearward) the aircraft will become negatively stable and when disturbed, the aircraft will not return to its original condition. Additionally, stall could become difficult or impossible. It is important to load according to the center of gravity.

The aerodynamic downward force on the tail means the nose pitches upon when the power is increased and pitches down when the poser is decreased.

The horizontal tail surface could be thought of as an upside down wing in that it creates a downward lift (tail downforce).

Center of Gravity Limits

The center of gravity (CG) location determines the general stability of the aircraft and certain limitations are set by the manufacturer. These are the forward limit and the rear (aft) limit for the center of gravity.

The center of gravity (CG) limits can be found in the POH (Pilot’s Operating Handbook) Weight and Balance (Section 6)

The center of gravity changes when any weight distribution within the aircraft changes including fuel weights, passenger weights and baggage/cargo loading.

Forward Center of Gravity

If more weight is in the front of the aircraft the center of gravity will more more forward an more tail downforce will be required to balance the aircraft and with more tail downforce, the aircraft will become more stable.

The further forward the Center of Gravity, the more the aircraft becomes “nose heavy” which requires more back pressure on the control wheel to raise the nose. If the Center of Gravity is ahead of the forward limit set be the manufacturer, the aircraft may become difficult to maneuver and have a hard time taking off, if not impossible.

Rear (aft) Center of Gravity

If the center of gravity is moved to the rear but loading more weight in the back, the less tail downforce is required to balance the aircraft which could cause the aircraft to become less stable.

The further back the rear CG is, the more the airplane becomes “tail heavy” which required more forward control to lower the nose to maintain level flight.

If the center of gravity exceed the aft limits, the plan may become stable and lowering the nose could cause it to continue lowering, while raising the nose could cause the nose to continue raising. Additionally, stall recovery could become difficult and there may be an inability to push the nose forward to recover from a stall.

Airspeed and Downward Tail Force

If flying at straight and level and only power is added, the aircraft nose will pitch up because the prop pushes more air back over the surface of the tail which creates a greater tail downforce.

The opposite is true when it comes to decreasing the power. Less air movement over the tail results in the nose pitching down. This effect is less noticeable in t-tail aircraft with the horizontal stabilizer at the top of the tail since the air flow from the prop wash is below the tail surface.

Controlling the Tail Downforce

The tail downforce can be controlled using the elevator (by pulling or pushing the control wheel)  in which you match the amount for force that is required for speed, power setting and the flap position. Additionally, the elevator trim can be set to achieve the appropriate tail downforce in which it is not necessary to hold the control wheel in position.

Trim settings may need to be adjusted and re-trimmed whenever there is a change to speed, power or flap position.



Using the Trim and Flaps

Q. What are flaps and what is the trim tab? A. They are secondary flight controls.

The primary flight controls are Ailerons, elevator and rudder. Trim Tab and Flaps are secondary flight controls.

Trim Tabs

A trim tab is a small control surface that is hinged at the trailing edge of a primary flight control that when deflected into the wind, uses airflow to apply a force on a primary flight control in the opposite direction. It also serves to neutralize or reduce the pressure required on the primary flight control.

Changes in Airspeed and Power changes the pressure needed on flight controls.

Trimming off the control forces relieves the pilot from maintaining continuous pressure on the control wheel which reduces pilot fatigue as well as sloppy control.

Trim tabs can be fixed in which they are set at the factory and not moveable or they can be electronically or manually moved from the cockpit.

When you move the trim tab, it moves the opposite direction of the desired control surface movement.

If you want to maintain your desired pitch attitude and keep the nose from dropping, you need to hold back the elevator control pressure by using the nose-up trim to relieve the back pressure in which you move the trim control in the “Nose Up” direction. This moves the trim tab down which puts an up force on the elevator which puts a down force on the tail and moves the nose up.

If the nose tends to rise above the desired altitude when the forward elevator control pressure is relaxed, use the nose up trim to relieve the forward pressure which moves the trim tab up. This puts down force on the elevator which moves the tail up and the nose down.

Before takeoff, trim tabs should be set to the takeoff position.

Wing Flaps

Wing flaps are attached to the trailing edge (rear edge) of the wings between the fuselage and the ailerons. These flaps change the shape of the wing to increase lift, increase drag, and decrease stall speed.

Using flaps allows you to takeoff and land at slower speeds and in shorter distance as well as to descend at a steeper rate and angle of descent without an increase in airspeed. In the air, the flaps help you to get down and to slow down.

How Flaps Work

Flaps change the shape of the wing by changing the curvature of the wing or changing the camber of the wing as well as increasing the surface area of the wing.

Since the shape and size of the wing changes with the flaps, so does the speed at which the wing stalls.

For a Cessna 172SP Skyhawk, the stalls speed without flaps is 48 knots and with full flaps, the stall speed is 40 knots indicated air speed.

Using Flaps During Takeoff

Many aircraft manufacturers recommend using flaps for takeoff and the Cessna 172SP Skyhawk models call for 0 to 10 degrees of flaps for takeoff. Takeoff roll is reduced and the total distance to clear an obstacle is reduced by 10% by using 10 degrees of flaps.

If using flaps during takeoff, it is important to remember to maintain the flap setting until the airplane is a safe distance from the ground and you are maintaining a position rate of climb.

Reducing the flaps setting, you may feel the aircraft “sink” a little which can be offset by adding additional back pressure.

The climb checklist at 1000 feet5 will help you remember to raise the flaps back to 0 degrees. Forgetting to raise the flaps will slow your climb due to the excess drag and you may risk structural damage to the aircraft if you fly faster than the recommended speed for extended flaps.

Using Flaps to Land

In most normal situations, you will want to use full flaps when landing, however, during gusty or turbulent conditions, you will; want to land with a reduced flap setting to increase the ability to control the aircraft.

If you cannot land or reject the landing and want to go around to try again, you will need to :

  • apply full power
  • pitch to reach a climb attitude.
  • raise the flaps to a partial setting
    • 20 degrees in the Cessna 172 Skyhawk.
    • (If you raise the flaps up to the full position without accelerating, you will be in greater risk of coming closer to a stall spee and it will allow the aircraft to sink down which delays you’re climb.)
  • accelerate to a safe climb airspeed
    • around 60 knots in the Cessna 172 Skyhawk
  • retract the flaps to 10 degrees until all obstacles are cleared
  • return the flaps to 0 degrees once you have reached a safe altitude



Effect of the Ground

Ground effect occurs when you are close to the surface which changes the airflow around the wing. When flying close to the surface, the airplane flies better because of less drag, more life and cannot fly at slower speed.

The three dimensional airflow pattern around the aircraft is altered by the ground during takeoff and landing. This restricts the vertical component of airflow around the wing which alters the wing’s upwash, downwash & wingtip vortices.

The cause of “ground effect” can be attributed to the differences in air pressure. When a aircraft is producing lift, high pressure below the wing tends to flow outward around the wing tips towards the low pressure on the top of the wing which reduces lift.

Some of this air does not make it to the top of the wing in time which creates a horizontal whirlpool of air in the wake of the aircraft. This whirlpool of air in the wake is called a vortex.

It is these horizontal whirlpools of air streaming from the wingtips that are called “wingtip vortices” or “wake turbulence”.

When an aircraft is low over a surface such as the ground or runway, the wingtip vortices are reduced because they are physically blocked by the ground from reaching the top of the wing. As a result, lift is increased and drag is decreased.

This greater lift and reduction of drag allows the aircraft to fly at lower speeds with less power.

Takeoff and Ground Effect

Ground effect can cause an aircraft to lift off at an airspeed that is not fast enough for flying OUT of ground effect. You will be out of ground effect once you climb more than one wingspan above the runway.

As lift decreases and drag increases, more thrust and a higher angle of attack is necessary which increases the stall speed.

Ground affect has the potential to make the aircraft lift prematurely which may result in settling back down to the runway and increases the distance needs to clear any obstacles on or at the end of the runway.

In order to best avoid premature liftoff, it is best to wait until you have reached the recommended speed for takeoff before allowing the aircraft to lift off.

Landing and Ground Effect

When landing, lift is increased and drag is decreased within one wingspan from the ground which causes the aircraft to have a tendency to float.

Excess speeds on landing approach can result in a greater “floating” distance so you will want to reduce the power as the airplane descends into ground effect to avoid overshooting the desired touchdown point on the landing strip or runway.

Floating on Landing

If you experience floating on landing, you have to take a few precautions and/or possibly take another course of action. Be sure to keep the aircraft on centerline and use the aircrafts lateral movement using the aircraft’s ailerons and rudder to prevent drifting from centerline.

Do not attempt to force a touchdown at a faster than normal airspeed as this could cause damage to the aircraft, especially if landing on the nose gear first.

If there isn’t enough runway to touchdown at normal speed and to stop without braking, you will have to make a go around pass and try again.