Spin Stops Here

______________________________________________________________________________________________

You need THIS and THIS

(Package price available) and THIS

IN CELEBRATION OF OUR 20TH YEAR SPECIALIZING IN MOONEY AIRCRAFT; Get your BRAND NEW PRE-PUBLISHED BOOK AVAILABLE FOR YOU NOW! "THOSE MOONEY AIRPLANES" by Richard Zephro; studying the Mooney since 1974; 38 year private pilot/owner of Mooneyland and author of the articles within this website. FLYING IS NOT CHEAP! Within this book we will discuss not only how to save money while owning your own airplane, we will discuss ways to save big bucks on purchase, ownership, maintenance, appearance (lipstick), and upgrades. Further; we will discuss matters of safely operating your prized BIRD, why Mooney is the safest (by far) in its class, and aid in the pure FUN of owning your own airplane. BOOK INCLUDES 25 CHAPTERS OF INFORMATION FOR MOONEY ENTHUSIASTS, OWNERS, AND ASPIRING OWNERS OF MOONEY AIRCRAFT IN PARTICULAR, APPLICABLE TO ALL AIRCRAFT OWNERS IN GENERAL AND INCLUDES 100 HOUR/ANNUAL INSPECTION GUIDE AND ALL ABOUT MOONEY AIRCRAFT; HOW TO KEEP THEM SAFELY FLYING (ON THE CHEAP) DO IT YOURSELF STUFF, WHAT TO WATCH FOR, AND INCLUDES 124 FULL SIZE PAGES OF INFORMATION AND PHOTOS. (Includes some reprints and references from Mooneyland and tons of NEW information at your fingertips) 2 NEW CHAPTERS JUST ADDED: "HOW MUCH DOES IS COST TO OWN AN AIRPLANE" and "MEMOIRS OF A MOONEY BUYER".

GET YOUR PDF COPY IN ADVANCE OF PUBLICATION EMAILED DIRECTLY TO YOU FOR $39.95; A TEN DOLLAR SAVINGS PRIOR TO PUBLICATION. CLICK ON THE "BUY NOW" PAYPAL LINK BELOW, PURCHASE THE BOOK AND I WILL PERSONALLY EMAIL IT TO YOU IMMEDIATELY. (2MB) in size. (this is the first of a series of must have books to come by author; Richard Zephro and you will automatically receive any updates, revisions, & additions to this BOOK).

See our dedicated new website for Mooney information at: www.mooneybooks.com.

Enjoy & learn, learn, and LEARN! Richard "zef" Zephro

OR GO TO:

A spin is what can happen if an airplane stalls in an uncoordinated condition, meaning it’s yawing (NASA) left or right (the relative wind is not directly on the nose). If you have never spun an airplane, we suggest that you rent a spin capable airplane and instructor. Doing so will remove the SURPRISE FACTOR you sense when first time spinning. It's intense, DO IT! Removing the SURPRISE FACTOR will add precious seconds to inadvertent spin recovery....

While in California in the mid 1980's, a Mooney M20K/231 was borrowed by a friend from the owner of the plane. He was on a long final approach as directed by the Van Nuys (VNY) controller when all of a sudden a C-130 based at VNY declared and emergency (as proceedure) when one of the 4 engines quit. The pilot of the 231 was concerned as to the spacing of he and the C-130, so he apparently yawed the aircraft so that he could see behind him better; he got so engulfed with locating the distance of the C-130 that he allowed the Mooney to slow to dangerous levels of speed and to spite the obvious stall warning buzzer and buffet, he lost control of that borrowed Mooney as it stalled, went over the top and began a very short undeveloped spin to the ground landing in a jumbled twist of metal near Balboa and Sherman Way boulevards. The C-130 pilot had reported that he had felt "guilt" for the accident as losing one of 4 engines was not really an emergency, just military regs. Should he have felt that guilt? NO WAY JOSE! It is EVERY pilot's responsibility to maintain control over his aircraft and on this day, 2 people and an otherwise perfect Mooney 231 died needlessly! I saw the post accident wreckage and I could have lived without seeing that!

If you add incorrect control inputs, your spin can go FLAT which in most cases is unrecoverable and can even go inverted.

SPORT AEROBATICS May 1997 has some very interesting reports on spin accidents. Between 1984 to 1994 there were twelve upright spin and five inverted spin accidents. Of these, eleven were intentional entries, while six were unintentional. Since 1994 there have been many more spin accidents.

Near Eagle Point Oregon On 14 December 1996, a Bellanca 8KCAB Super Decathlon intentionally entered an inverted spin [to the right ???] by the application of left rudder at an altitude of 7200 feet. After three revolutions the flying instructor asked the student, who was a commercial pilot to assist with the rudder. The student noted that right rudder pedal was full forward and applied left rudder. This action prompted the following response from the instructor “not that rudder” where upon full right rudder was re applied. The student then took hold of the control stick, which was in the full forward position and moved it aft about four inches. He could not feel any control input from the instructor on the stick. Upon releasing the stick it returned to the full forward position. There was no power applied throughout the entry or recovery attempt. The instructor instructed the student to “bail out” which he did about 250 feet above the ground. At the point of impact the rudder was still fully deflected to the right. The aircraft impacted the ground in an inverted spin killing the instructor, who was still strapped in. There was no indication of any flight control or structural failure.

What caused this accident to occur? Pilot error due to lack of experience in spin recovery was the probably cause. This can be broken down as follows. Pilot disorientation, in regard to the direction of yaw!, and or incorrect recovery technique! Throughout this discussion and to avoid confusing you, the physics of a spinning a/c will be treated as seen by an outside observer. They do not change regardless of the a/c attitude. ie. Spinning Upright or Spinning Inverted. It is only the pilots point of view that changes. Control inputs discussed will be from the pilots point of view. ie. right rudder means using your right foot etc. As the spin was initiated by applying left rudder at the point of stall, it must be assumed that the a/c was spinning inverted to the right, [as viewed by an outside observer]. Remember, the physical forces acting on a spinning aeroplane do not change direction, regardless of the a/c attitude. [ie. upright or inverted]. If the a/c was in fact spinning to the right, the application of full right rudder and letting go of the control stick should have being sufficient for the aircraft to recover. This statement is based on the “Muller-Beggs Emergency Spin Recovery Technique”. It may just be possible that the a/c was in fact spinning to the left, in which case the pilots being disorientated in regard to the direction of rotation, and continuing to apply right rudder, would be holding the a/c in the spin, thus causing the crash.

During recovery and to avoid any confusion in regard to the direction of yaw during upright or inverted spins, look out over the nose and pick a point. That point will move towards one wingtip or the other. Stand on the corresponding rudder. Another way of saying it is, to stand on the same rudder as the wing that is moving forward across the horizon. If you do not look out over the nose, but allow your head to move back during an inverted spin, you may perceive the yaw to be in the opposite direction, leading to the incorrect rudder being applied to affect a recovery. This error may occur if the a/c attitude is not flat, and as you are hanging upside down, it is very easy to look down at the ground behind the centre of rotation, thus seeing the yaw in the wrong direction.

Another possible cause, may have been lack of positive control inputs during the attempted recovery.

1.   Cut the throttle.
2.   Take your hand off the stick.
3.   Kick full opposite rudder until the spin stops.
4.     Neutralize rudder and pull out of dive.

However the proponents of this technique agree that it only works with some aircraft. On some other a/c it will not work. Question: Are you flying an a/c in which this method of recovery will not work? Was this recovery method a contributing factor in the Eagle Point accident?

Step One: Cut the throttle: This is quiet straight forward, and should not be an area of concern to us as long as we, “do close the throttle fully”.

Step Two: Take your hand off the stick: Also quiet easy to follow and works up to a point. In many a/c the point of non recovery may never be reached, even if the spin has gone flat and stable, and just releasing the stick is all that will be required to recover.

Remember however that Eric Muller stated that his emergency spin recovery method was suitable for most a/c. What about the rest? A small number of a/c will require, in addition to closing the throttle and applying full opposite rudder [step one and step three], a positive lowering of the nose to affect a recovery, from any spin. Two a/c that may fall into this category are the Chipmunk and the Zlin 526. A few years ago a Zlin crashed in Australia killing an A.A.C. member when it failed to recover from a spin.

The Chipmunk also has the reputation of being an a/c that should be treated with a great deal of respect, particularly in regard to spins. According to Gordon Lee, shortly after its' introduction the Chipmunk had the distinction of having the worst crash record of any a/c on the Australian registrar. It is suspected that pilots who had trained on the DH 82 got into spins and failed to recover, because unlike the Tiger Moth, the Chipmunk requires an exact and positive recovery technique. Most Chipmunk pilots are aware of the consequences of not making sure that the park brake is fully released, which can restrict the rudder travel, thus making recovery from a spin unlikely. Many pilots are also aware of the danger posed by foreign objects restricting control inputs and have heard the story of the bent penny.

Many more a/c, will require a positive lowering of the nose to recover, once spin is stable and flat or is accelerated [by adding power or using aileron etc.]. Some a/c that I have flown that fall into this category are Pitts S2A, Cessna 150 Aerobat, Cessna 152 Aerobat and the Bellanca 8KCAB Super Decathlon. Remember, no two a/c will recover in exactly the same manner. This may be due to different rigging, changes to the C of G position, and Mass Distribution etc.. An a/c that has been repainted a number of times over the old paint, will have an aft C of G due to the fact that the area to be repainted is larger behind the C of G and the weight of the extra paint applied.

The Mass Distribution, The Tail Damping Power Ratio [TDPR], and The Unshielded Rudder Volume Coefficient [URVC] are just some of the terms used by a/c designers to predict the Spin Recovery Design Requirements It is interesting to note that there are two sections to the resulting graph. “Recovery by rudder alone” and “Recovery by rudder and elevator”

The first aerobatic a/c that I owned was a Pitts S2A VH KJG. It was an a/c that required a positive lowering of the nose to recover from a flat inverted spin. Unfortunately VH KJG was destroyed in 1980 in WA when it recovered from an unintentional spin, too low to avoid hitting the ground, killing the pilot and passenger.

Step three: Kick full opposite rudder! This also needs to be closely examined.

Opposite to what? Yaw! Of course!. But, which way are we yawing?. “Eric Muller recommends the rudder with the most resistance”. Some other pilots recommend “the rudder closest to you”, which may require looking down at your feet. What if the other pilot or passenger is already applying rudder in the correct direction for recovery?. Many times during instructing I have experienced students who have done the wrong thing with the controls, and to extend my life expectancy I had to take over. The worst example that I know of happened to a friend of mine, who was giving instruction on forced landings in an Ultralight. Upon closing the throttle to simulate engine failure, his student panicked and pushed forward on the control stick locking his arms in that position until the point of impact. My friend Nev. who was in the rear seat recovered after a long stay in hospital. The point is, before you blindly follow step three, make sure that you are making the correct control input. Failure to do this may result in you inadvertently re-applying rudder into the spin. This also may have been a possible cause in the December fourteen accident.

Should you have no visual outside reference, the Turn Coordinator will always indicate the correct direction of yaw [from the pilots point of view] even if you are inverted, allowing the correct recovery rudder to be applied. If the needle is hard left, apply opposite “right” rudder. Remember, rudder must always be applied opposite to yaw. Do not pay any attention to the ball as this only indicates slip, not yaw, and may vary either way depending on the centre of rotation and type of spin that you are in. ie. incipient, un-stable, stable, flat, etc. One slight problem here, many aerobatic aircraft are not fitted with a turn and slip indicator.

During my early flying career I posed the question, to Bill Cooper, who had taught me to fly and do basic aerobatics in a Victa Airtourer. Bill how does one quickly determine the correct direction of yaw when in a spin?. His response was, that if confused, “apply rudder in one direction, and that if this did not work, to then try the other rudder”. Not to be out done I then asked, “what if we have just popped out of cloud and were in a spin at 1500 ft. AGL. and probably inverted?” - not much time to try rudder in one direction and if that did not work to then try the other rudder. His answer was to “look at the Turn coordinator”. All right Bill, we have just got the S2A going and it is not fitted with a turn coordinator. What are we going to use?. This had prompted me to work out the technique of looking out over the nose.

Every pilot should sit down and spend the time visualizing what you can expect to see and how to interpret these visual clues.

Question: what is the difference between a “Turn Coordinator” and a “Turn And Balance”,[“Turn And Bank” to some people]?

As you can see this is a very long and involved subject. Most Aerobatic pilots know that a stable spin can be flattened out by two main methods.

Power and aileron.
The application of power in an a/c with the propeller rotating clockwise [as seen from the pilots point of view] when yawing [spinning]to the left will cause the nose to rise. The smaller and lighter the a/c, and the larger the power output, the greater the tendency. will be for the a/c nose to rise. This is due to gyroscopic precision. Because we are causing the yaw to the left by applying left rudder, the rotating force is being felt as a force acting forward at three o’clock position of the propeller arc and then processing around the propeller arc ninety degrees in the direction of rotation, resulting in a force acting forward at the six o’clock position, thus forcing the nose of the a/c to rise. If the same a/c is rotating to the right the nose will be forced down by the application of power. In a/c that have the propeller rotating in the opposite direction ie. anti-clockwise the tendency will be for the nose to rise when yawing [spinning] to the right, and to lower the nose when yawing [spinning]to the left. Remember, During recovery from a spin make sure that the throttle is fully closed.

Out-Spin Aileron
Let me tell the story and why I have so much respect for spins, and why thorough spin training by properly qualified instructors is essential. After I had rebuilt VH KJG in 1978, there were no suitably experienced instructors to give me the necessary training that I required, so I obtained a copy of Neil Williams book “Aerobatics”. After reading the appropriate chapter on spinning I proceeded solo to the training area and 6500 ft. After placing the aircraft into a left spin, I applied outspin aileron and went flat as expected. So far, so good, I thought. At 5000 ft. I tried to recover. To my dismay, the spin got a lot, lot faster. I went through the recovery procedure once or twice more [I am not sure of the exact number of times].

Step One: ailerons neutral and close the throttle . Step Two: apply full opposite rudder. Step Three: stick forward. By this time I was giving some serious thought to the prospect of having to jump. I decided to give it one more try, and in doing so looked out and spotted the right aileron still deflected up very slightly, only about a 1/4 of an inch. This prompted me to push the stick over to the left {use inspin aileron] and guess what happened?

Subsequently I worked out that: I already knew the correct rudder application for recovery [due to the direction of rudder used for entry]. I was very hasty when lowering the nose [I had worked out that I was going to need forward stick to recover before leaving the ground] and probably shielded the rudder and “unloaded” during the recovery. This caused the rate of yaw to increase dramatically. I did not centralize the ailerons fully for the recovery phase. [although I had not thought about using in-spin aileron to assist during the recovery prior to going up, I was able to do so at the time].

The recovery altitude was approx. 2000 ft. on Q.N.H. and only about 1000 ft. Agl. I do not like my chances had I decided to jump. The use of in-spin aileron to assist during the recovery is recommended in the book Flight Unlimited by Eric Muller. This is a good technique in most a/c. Neil Williams recommends ailerons neutral in his book.

Let’s look at the physics involved in using out-spin aileron during a stall/spin. If an a/c is at the point of a wings level stall and the pilot perceives a roll to the left, and tries to oppose the roll by applying right aileron it is likely that the roll to the left will accelerate uncontrollably. This is due to the left aileron deflecting down as the stick is moved to the right, thus increasing the Angle of Attack well beyond the already near critical angle, thus increasing the drag and reducing lift. At the same time the right aileron is deflecting up thus maintaining lift and reducing drag. Auto-rotation or an uncontrolled roll followed by yaw to the left is the end result.

The use of out-spin aileron during a spin has a similar affect, thus increasing the drag on the into-spin wing and reducing the drag on the other wing [the forward moving wing], causing the rate of rotation to increase dramatically. This is why the ailerons should be neutralized during the recovery from a spin, and why all pilots are taught not to use any aileron during stall training to avoid an un-intentional spin.

While Eric Muller recommends the use of in-spin aileron as part of a normal spin recovery,. in some a/c it may have an adverse affect. The use of inspin aileron in a Cessna 150/152 Aerobat has the opposite affect to what you would expect. Inspin aileron causes the spin to go flat.

This is the result of the very effective Frieze Ailerons that are fitted to the Cessna wing creating a lot more drag on the aileron that is deflected up.[inside aileron with inspin aileron applied]

In the Cessna 150/152 outspin aileron will cause the spin to stop. The reverse airflow through the propeller will cause the motor to stop rotating, just to add a bit of extra excitement and to further raise your heart rate.

In the unlikely event that you find yourself spinning inverted in the Cessna it is likely that the use of out-spin aileron will have the normal affect of flattening the spin while in-spin aileron will help during the recovery. This is due to the frieze aileron being in-effective when spinning inverted, as the hinge point of the ailerons is on the top surface of the Cessna wing, a smooth surface is maintained when the wing is inverted regardless of aileron deflection, and A of A should come back into play. Due to a lack of an inverted oil system in the Cessna 150A/152A I have being unable to flight test the above theory inverted, although the use of in-spin aileron to flatten the upright spin has being tested over a number of years and a countless number of spins.

A word of warning to anyone contemplating flat spinning the Cessna 150A/152A. A positive hands on spin recovery will be required. Allow several rotations for the recovery to be effective. Also allow for an air restart as the motor will probably have stopped rotating. About 6000 feet plus minimum starting altitude.

Question. During inverted spinning, what constitutes “Out Spin Aileron”?
As previously stated the physics remain the same to an outside observer. To initiate an inverted spin to the left we can stall the a/c inverted and apply right rudder. This causes the left wing to move forward. As we are inverted the left wing is already on the right hand side as seen by an outside observer, thus the a/c enters a spin to the left. The pilot is still holding forward stick and right rudder with the a/c spinning to the left [rolling and yawing to the left]. To apply outspin aileron the pilot would attempt to roll the a/c to the right. That is, apply aileron in the same direction as the rudder being used to initiate the spin. Left aileron applied while holding the a/c in an inverted spin to the left with right rudder and forward stick would qualify as In Spin Aileron. If you are a bit confused, use the analogy that Neil Williams did of a pilot sitting on the belly of an inverted a/c and flying it with an extended control stick. Simply stated, if you are spinning inverted to the left, using right rudder, then right stick is out spin aileron. During recovery, stick in the same direction as the recovery rudder, is in-spin aileron. Can you see why it is so important to work out the correct rudder application.

Unloading is a term used to describe a method of reducing drag and increasing the rate of rotation during spins and snap rolls. All a pilot has to do is to unload is move the stick towards the neutral or central position rather than holding full forward or full back stick once a spin or snap roll is underway. As both of these manoeuvres require the angle of attack to remain over critical too much unloading will un-stall the a/c thus stopping the manoeuvre.

Situation awareness is critical when undertaking spin training.
The sky above is as useless as the runway behind.
The standard spin recovery is:
·        Close the throttle and ailerons neutral.
·        Identify the direction of yaw and apply full opposite rudder. Sufficient time must be allowed for the rudder to take affect.
·        Lower the nose. Progressively move the stick from aft, to full forward, when spinning upright, or from forward, to full aft, when spinning inverted. Do not rush lowering the nose, and expect a fully developed spin to take up to three or four rotations to stop spinning.
·        When the rotation stops, neutralize the controls, roll to wings level, and then ease out of the dive.
If the spin continues, go to your backup plan. ie. apply inspin aileron/outspin aileron as appropriate to your type of a/c.
Before embarking on your spin training lesson you should review your spin awareness checklist, including emergencies.

The following air exercises describe procedures that complement the Flight Instructor Guide and provide additional guidance in the training of stalls and incipient spins. To encourage the use of scenarios based on practical flight situations, some examples are provided but are not considered to be a comprehensive list. Refer to the matrix in Appendix 1 Stall Scenario Conditions, in this document, to help select the conditions for developing various scenarios. The intent of this matrix is to provide a variety of options. Instructors are not expected to teach every variation. Select a few that work well with the type of aircraft you fly.

Many aircraft manufacturers prohibit the use of flaps when practising intentional spins. If an inadvertent spin is entered during advanced stall practice, follow the manufacturers recommendations or, in the absence of these recommendations, retract the flaps at the first opportunity after initial recovery action has been taken.

Departure Stalls

Using information from actual aviation accident reports can help lend realism to scenario development. For example,

“Location: 1,100 FT grass strip with 75 feet high pine trees at departure end of the runway. The departing C-150 was observed by witnesses to become airborne approximately 200 feet from the end of the strip and approximately 500 feet from a line of pine trees off the departure end of the strip. The a/c entered a steep climbing right turn then rolled to the left and descended in a steep nose down attitude until it collided with the ground. 2 fatal”

Using this example refer to the Stall Scenario Conditions Appendix 1. Starting at the left column of the matrix select

This one scenario can be modified by changing any of the 5 conditions in the matrix. Many other scenarios can be developed from the matrix by using aircraft accident reports and personal experience. Avoid using only one or two scenarios in your training. Students should be exposed to as wide a variety of situations as possible.

Arrival Stalls

Note: In some aircraft types a skidding descending turn stall will result in the inside wing stalling first and a sudden and aggressive incipient spin developing. Training aircraft that exhibit docile spin characteristics may not produce a convincing demonstration of this manoeuvre. Try different configurations with your aircraft to find the most effective demonstration.

Again, using information from actual aviation accident reports can help lend realism to scenario development. For example,

“Location: 1 mile east of the aerodrome. Weather conditions: VFR, winds NW at 15 KT, moderate turbulence. The Piper Cub J-3 overshot the extended centreline for runway 26 while turning final. Witnesses observed the a/c turning from the south to the west at a moderate bank angle. Prior to completion of the turn the a/c bank attitude increased rapidly and the nose dropped to a nearly vertical attitude. The wreckage impact was consistent with an a/c in a spin condition. 1 fatal”

This accident is consistent with an attempt to “cheat” when overshooting a turn to final by input of rudder to increase the rate of turn and opposite aileron to maintain a normal bank angle. If the aircraft is allowed to stall at this point, the inside wing will stall first and a spin will develop.

Using this example refer to the Stall Scenario Conditions Appendix 1. Starting at the left column of the matrix select

This one scenario can be modified by changing any of the 5 conditions in the matrix.

Engine Failure after Take-off (followed by an attempt to return to the runway)

This demonstration will show the student how much altitude the aeroplane loses when, following an engine failure after take-off, an attempt is made to return to the departure runway. In order to complete the manoeuvre, the aircraft must be turned to a reciprocal heading AND realigned with the runway. This requires much more than just 180 degrees of turn. For novice pilots, turning back is not an option. An evaluation of stall/spin accidents in Canada showed that the pilot is eight times more likely to be killed or seriously injured turning back than landing straight ahead. For expert pilots who know how much altitude is needed to complete the required manoeuvring, it can be an option but even experts should be looking for landing areas that require less manoeuvring and less risk. Perform this demonstration using either a medium or steep bank in the turn, giving emphasis to stall avoidance.

Note: It should be stressed that the successful return to the airport after an actual engine failure on take-off depends on a variety of factors including available landing surfaces, altitude AGL when failure occurs, weather, turbulence, aircraft type and pilot skill and stress level . Point out that the altitude loss incurred during the controlled demonstration will be significantly less than in a real life situation. It is recommended to conduct the demonstration from the cruise configuration to reduce wear on the engine.

Accelerated Stalls

At a safe altitude, set the aircraft up at 80% of the appropriate manoeuvring speed (Va) for the weight of the aircraft.

Here is an actual aviation accident report that can help you design a realistic scenario.

“The Cessna 210 with 3 persons onboard was observed to be flying at tree top level and manoeuvring in an abrupt manner. A video camera recovered from the wreckage recorded the final minutes of the flight. The pilot was manoeuvring to allow a passenger to video tape a moose when the stall warning horn activated and the aircraft stalled in a 45° left bank turn at an altitude of 50 feet AGL. 3 fatal”

Using this example refer to the Stall Scenario Conditions Appendix 1. Starting at the left column of the matrix select

This one scenario can be modified by changing any of the 5 conditions in the matrix.

Distractions

Improper airspeed management resulting in stalls is most likely to occur when the pilot is distracted by one or more other tasks, such as locating a checklist or attempting a restart after an engine failure; flying a traffic pattern on a windy day; reading a chart or making fuel and/or distance calculations; or attempting to retrieve items from the floor, back seat, or glove compartment.

Pilots at all skill levels should be aware of the increased risk of entering into an inadvertent stall, spin or spiral dive while performing tasks that are secondary to controlling the aircraft. Providing the student with normal tasks secondary to the control of the aircraft builds confidence and ability. A properly trimmed aeroplane is a key component of controlling the aircraft while handling distractions. The following list of deliberate distractions can challenge students and improve their skills.

2. Ask the student to decrease the cruise airspeed by 10 knots and repeat #1.

3. Have the student climb 200 feet and maintain altitude, then descend 200 feet and maintain altitude while performing a task in #1.

4. Have the student reverse course after a series of S-turns and create a distraction.

The following Learning Guide includes links to condensed versions of the Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25) and Airplane Flying Handbook (FAA-H-8083-3A).

The icon offers a comparison link to NASA’s various websites or one of the FAA texts; click on the desired side of the icon. Other single links identify their origin by the acronym in the parentheses. Click on the desired link to display the applicable page.

The following glossary will help you attain a better knowledge of the concepts of angle of attack.

Angle of attack : The angle between the chord line of the wing and the direction of the relative wind (or Instantaneous Flight Path).

The secret to understanding stalls is when you exceed the upper limits of this15-degree compensator; the airplane will no longer fly, and is likely to go out of control.

Center of Lift/Center of Pressure (CP) and Center of Gravity (CG) —Lift acts upward and perpendicular to the relative wind. A wing generates lift over its entire surface, but an imaginary point—called the center of lift or center of pressure—represents the single point where lift’s total upward force acts on the wing.

The CP’s location relative to the center of gravity (CG) plays an important role in any airplane’s longitudinal (nose up and down) stability . Because pilots determine the CG’s when they load the airplane with people and baggage fore and aft to simulate different CG locations and the different stability problems they can cause, including loss of control on takeoff or landing. In addition, moving the airplane fore and aft gives you a visual understanding of the importance of calculating the airplane’s proper weight and balance.

Chord —An imaginary straight line drawn from the leading edge to the trailing edge of an airfoil’s cross-section.

Elevator or Stabilator —The control surface pilots use to change the wing’s angle of attack.

Instantaneous Flight Path (IFP)—Indicates the actual flight path of the airplane (and the relative wind). We use the word "instantaneous" because of Mother Nature’s continually-changing disruptions (NASA).

Lift—The force (NASA) that directly opposes the weight of an airplane and holds the airplane in the air. Lift is generated by every part of the airplane, but the wings generate most of the lift. Lift is a mechanical aerodynamic force produced by the motion of the airplane through the air. Because lift is a force, it is a vector quantity, having both a magnitude and a direction associated with it. Lift acts through the center of pressure of the object and is directed perpendicular to the flow direction. Because lift is perpendicular to the flow directions relative wind display to behind the lift vector on AT3D to demonstrate lift’s magnitude and direction, which is one more way of displaying AOA movement. The relative wind’s direction can be interpreted on AT3D by the velocity (V) vector.

Recognition of Stalls (FAA)—Perceiving involves more than the reception from the five senses. Perceptions result when a person gives meaning to sensations. People base their actions on the way they believe things to be. An example is how a home team’s fan sees a foul play differently than a visiting team’s fan. Safe pilots know that "what you see out the windshield is not always what you get."

Pilot’s Perceived Attitude—Represents the pilot’s PERCEIVED flight path. The importance of understanding that what the pilot perceives is not always perfectly correlated to Angle of Attack. We attempt to bring attention to the action of “sink” or “mush”, particularly in events of rapid increases in drag, pulling out of a dive, and wind shear, on our two-dimensional instructional devices.

Relative Wind —Direction of the airflow produced when an object moves through the air. The relative wind for an airplane in flight flows in a direction parallel with, and opposite to, the direction of flight. Therefore, the actual flight path of the airplane determines the direction of the relative wind. Relative wind is easy to understand in a wind tunnel (NASA). It’s the air that is being pushed past the airplane at a controlled velocity, and the fact that it is a tunnel, at a constant direction. In an airplane in flight, it is the pilot who controls the velocity of the air past the airplane because the air is not being pushed past the airplane. It is the airplane that is plowing through the air. Therefore, the flight path determines the direction of airflow, regardless of its direction.

Stalls—and the spins that can ensue—terrify many student pilots (and a lot of experienced pilots, as well) because pilots often have difficulty understanding the aerodynamics (NASA) that cause them. The lessons that stick, however, are tangible and visible because the student sees a constant speed on their airspeed indicator during stall practice. However, stalls are caused by excessive AOA. The FAA readily supports this truth in two FAA training manuals, Pilots Handbook of Aeronautical Knowledge (FAA-H-8083-25 ) and the Airplane Flying Handbook (FAA-H-8083-3A).

In "Principles of Flight," the second chapter in the Pilots Handbook of Aeronautical Knowledge, the FAA emphasizes the importance of angle of attack, using the term more than 70 times. Repeatedly, it stresses that stalls happen when the wing reaches its critical angle of attack, not when pilots fly below some airspeed (NASA).

Angle of attack cannot exist without the relative wind, which is another invisible, intangible aspect of flight that often confuses pilots. In its new training manuals, the FAA offers a clearer explanation of this, writing that the "actual flight path of the airplane determines the direction of the relative wind." Like angle of attack, he relative wind—the airplane’s Instantaneous Flight Path—visible and real.

The FAA supplements describe the creation of lift in detail. To paraphrase: when air flows smoothly over a wing, it creates low air pressure on top of the wing (Bernoulli’s theory ), with a higher pressure underneath. Because everything in nature seeks equilibrium—and as one air pressure tries to reach the other—it carries the wing with it, creating lift. Tom Benson, of NASA’s Glenn Research Center offers this simple explanation of lift (NASA): "I prefer, when discussing lift with students, to just stop at the Newtonian 3rd law (NASA)—Lift is the re-action to the turning of the flow. No turning, no lift."

These two explanations may seem to be in disagreement (NASA) with each other because of the two differing theories. However, they may be closer than one thinks. The key to understanding creation of lift is that it is a mechanical force. To be a mechanical force, there must be interaction and contact of a solid body (airplane or wing) with a fluid (air). "Contact" is the key word, as it is the creation point. Similarly, the effects of lift are also present; like the pressure variation around the object, velocity variation around the object, downwash, and shed vorticity. We can assume that the FAA teaches the Bernoulli approach (pressure variation) because it is calculable at slower speeds, observable, and easier to understand. This confusion is why we refer to the creation of lift as "magic"—because it cannot be observed. One can only see its effects.

We can use the laws of fluid physics to substantiate lift (NASA), wherein a change in velocity in one direction can cause a change in velocity in a perpendicular direction. This doesn’t occur in solid mechanics. The component of the net force perpendicular (or normal) to the flow direction is lift; the component of the net force along the flow direction is drag (NASA). Again, the "perpendicular direction" to the relative wind is the creation of lift. The wing, along with other parts of the airplane, is simply an efficient means to the "turning of the flow". What’s important for our discussion here is that changing the wing’s angle of attack changes the amount of lift a wing produces—up to the wing’s critical AOA. When the wing reaches its critical angle of attack, the air can no longer flow over the wing’s surface smoothly, and the wing stalls—abruptly decreasing lift. Understanding this critical angle of attack is essential for safe flight. At the critical angle of attack (Red), the wing will not fly again until the pilot reduces its AOA below that stated 15 degrees. Reducing the AOA allows the air to once again flow smoothly over the wing, thus generating lift. Note: "air to once again flow smoothly over the wing" will be replaced with "boundary layer (NASA) formation and separation" in advanced studies. The phrase may change, but the outcome of stall will remain the same.

Focusing on the effect of lift and not its creation can lead to many incorrect theories.

One of THIS ARTICLE'S primary purposes is to help teach stall awareness. It achieves this by completing the mind’s picture of stalls and teaching pilots how to recognize a stall and how to take prompt, corrective action. As suggested, the correct action is to reduce the angle of attack so the air can again flow smoothly over the wing. Applying full power aids in stall recovery. However, like within a glider, the stall is actually corrected by reducing the AOA.

Remember that AOA is the angle between the wing’s chord line and the relative wind (flight path), not the chord line and the horizon or ground. An airplane can exceed its critical AOA—it can stall—in any attitude, even when its nose is pointed straight at the ground. Regardless the airplane’s attitude, the corrective action is still the same—reduce the AOA.

Three major reasons why we need to add the "Pilot’s Perceived Attitude" to our "Training Archives".

Pilot’s Perceived Attitude—represents the pilot’s PERCEIVED flight path. A frequently inaccurate mind’s picture of what is really happening to the airplane. The FAA warns that only through proper training and experience can this phenomenon be exposed. "Kinesthesia (FAA), or the sensing of changes in direction, or speed of motion, is probably the most important and the best indicator to the trained and experience pilot. If this sensitivity is properly developed, it will warn of a decrease in speed or the beginning of a settling or mushing of the airplane." The Pilot’s Perceived Attitude to educate that there are at least three crucial times when the pilot’s perceived flight path may be significantly dissimilar than the actual flight path, due to sinking or mushing:

1. According to NASA’s Tom Benson: "With real airfoils, the angle of attack dependence gets real complex, because it affects both the amount of lift and the amount of drag. So, lift could be going up because of increased angle of attack, but the speed could be decreasing because of increased drag. So exactly what angle of attack does to aircraft performance depends on some other variables, including the speed when the maneuver is initiated, and the power setting of the engine. At altitude, at high speed, increasing angle of attack increases lift and the aircraft moves up. At low speed, (like during landing) increasing angle of attack decreases speed (NASA), and the aircraft drops (more). I understand that this "reversal" causes a lot of problems for new pilots. At low speeds, you use the throttle to go up and down, and angle of attack to go faster and slower; exactly the opposite of high speed flight."

2. Accelerated Flight during rapid ascent (pull-up) (FAA). Accelerated flight has more to do with abrupt changes in angle of attack than it does airspeed. The laws of physics (NASA) say that a mass traveling in a straight line will continue to move in a straight line—until some force causes the mass to assume a curved path. An airplane is a mass, and hauling back on the yoke is a force causing it to assume a curved path (up). Before the up force can curve the path, it must overcome the airplane’s straight-and-level inertia (NASA). This overcoming of inertia is called centrifugal force, which is a pushing towards the outside of the curve. When an airplane is flying a curved positive flight path, the wings must support the airplane’s weight—plus—the load imposed by centrifugal force.

Hauling back on the yoke is a positive flight path because it creates a positive load on the airplane; centrifugal force is acting in the same direction as the force of weight. Pushing the yoke forward creates a negative load because centrifugal force acts in a direction opposite to that of the force of weight.

Pilots might expect a positive rate of climb when they abruptly haul back on the yoke, but the airplane may not respond this way. Typically, the perceived flight path is more inclined than the actual flight path because the aircraft’s momentum (NASA) is causing a lag between the pilot changing the attitude, and the actual resultant change in altitude. Many of the "buzzing" accidents have occurred because the pilot did not perceive the proper flight path.

3. Wind shear (FAA) is another invisible mystery of flight often misunderstood by all pilots. For example, a new captain on a Citation jet had just rotated for takeoff; the aircraft climbed about 100 feet, and then settled back to the ground. Fortunately, this happened in a simulator! The instructor asked the new captain if he knew what had happened. With anger in his voice, and thinking the instructor had incorrectly programmed the simulator, the captain said, "You tell me!" The instructor had programmed the simulator correctly for the New Orleans takeoff W/S (NTSB)—and this caught the new captain off guard.

Because wind shear represents a change in the direction of the relative wind, it disrupts the airflow moving past the wing. Wind shear moves in a different direction and velocity from the prevalent wind. Portions of air in which the airplane is flying can shift up, down, forward, or backwards. This shift may lead to a high rate of sink; all the while the attitude indicator appears to be normal. Wind shear is most often associated with thunderstorms, but it can occur in almost any weather. Even in days with little wind, hills, buildings, and trees can cause wind shear. These obstacles are commonplace at general aviation airports.

Wind shear can be horizontal or vertical, and each affects airplanes differently. Vertical shear changes the AOA because it suddenly moves the airplane up or down. Caution: Vertical shear can cause structural damage to an airplane, or even worse: a break-up of the aircraft. Horizontal shear immediately changes the airplane’s speed, which pilots can see on the airspeed indicator. If the horizontal shear gust reduces the airplane’s speed by 20 percent, the airplane will sink, trading altitude for airspeed to maintain the AOA it was trimmed (NASA) for. Too often, pilots don’t recognize horizontal shear until it’s too late. Usually, a gain and then a loss of airspeed is the first clue, and pilots may attribute this to "turbulence." A sink rate is the next clue. A microburst, or severe thunderstorm, starts as vertical wind shear and becomes horizontal after it hits the ground. It then curls up and around, going through its vertical and horizontal phases again.

Such a microburst brought Delta Flight 191 (NTSB) to grief at Dallas/Fort Worth International Airport on August 2, 1985. Crash investigators discovered that airport instruments recorded that the headwind Delta 191 was flying into rapidly increased 26 knots. Then, just as suddenly, it became a 46-knot tailwind. The NTSB claims the aircraft encountered approximately 73 knots of wind shear.

The jet was only 800 feet above the ground when it encountered the wind shear, giving the pilots little room to maneuver (NTSB reports that full power was applied). The airplane began to lose airspeed and altitude at the same time. The unfortunate flight ended 38 seconds later—in a crash short of the runway.

Charlie Tennstedt, a former Test Pilot and Fight Instructor made these following thought-provoking remarks regarding wind shear. "To reinforce the intent of learning about angle of attack, it is imperative that pilots DO NOT use the airspeed and vertical speed indicators during a wind shear escape maneuver. The static pressure in these microburst events drops rapidly as the air flows rapidly outward (thanks to Mr. Bernoulli’s principle) and forces pilots to DISREGARD speed and rate of climb indications. This is the reason for training pilots to rotate to the stall warning onset [with full power] and hold that attitude until the aircraft is clearly climbing away from the ground (radar altitude is increasing) or 400 feet AGL if not RA equipped." Please consult your aircraft manufacture’s recommended wind shear recovery procedures, as each airplane reacts differently in wind shear.

A spin is what can happen if an airplane stalls in an uncoordinated condition, meaning it’s yawing (NASA) left or right (the relative wind is not directly on the nose). Just twist the model back and forth to simulate yawing as you maneuver the model’s AOA from green to red.

This twist lets you visualize that one wing is going forward while the other wing is going backward. Because the backward-moving wing is going slower and has a greater AOA, it stalls first, causing the airplane to slip in its direction. As this happens, the relative wind strikes the fuselage and vertical fin and tries to weathervane the airplane, or point its nose into the relative wind.

Trying to pick up (level) the low wing with aileron and raise the nose with elevator are a natural reaction. But in this case, what seems "natural" is incorrect and dangerous. The "natural" reaction makes the situation worse and often leads to a spin.

FAA supplements offer more detailed information, and your airplane’s operating handbook or flight manual will give its recommended spin recovery procedures. In the absence of a manufacturer-recommended procedure, the FAA recommends this spin recovery procedure (FAA):

Caution: to some people, applying " positive and brisk " forward stick could mean pushing the stick all the way to the panel. This, with rare exceptions, is incorrect. Any movement more than required would curve the flight path and may aggravate the stall.

Remember that spins consume a lot of altitude, and so do their recoveries. And remember that most stall-spin accidents occur in the traffic pattern, when making the turn from base to the final approach leg, when the airplane is close to the ground. Pilots may know how to recover from a spin, but in this situation they don’t have the altitude to use it. The only solution is to make sure all control inputs are coordinated, and that the AOA is in the green.

Flying is one of the most joyous activities we humans can pursue, and increasing our ability to fly safely adds to this enjoyment. Safety is based on knowledge, —increase pilot knowledge of the invisible magic (not magic anymore) that makes flight possible, and to increase it simply and clearly. Remember, From Red to Green is the Dream. And it’s the key to flying safely.