If you execute a turn with excessive or insufficient rudder or aileron and exceed the critical angle of attack for your airspeed, you are risking an inadvertent spin unless you promptly initiate stall recovery.
There are several factors which can contribute to stall/spin accidents. Among these are:
· Load factor
· Snow, ice, or frost on the wings
· weight and balance (center of gravity)
· Aircraft configuration
· Turbulence
· Pilot inattention due to distraction
Experienced solely or in combination, these factors can have deadly consequences. To adequately prepare your students to meet PTS stall/spin awareness criteria, you must provide them with a thorough knowledge of these possible contributing factors and how they affect aerodynamics to cause a spin.
Parachutes are not required during spin training when working towards a certificate or rating.
Recognition of a stall leading to an unintentional spin may not be easy when a pilot's attention has been diverted to another task. However, the entry of an unintentional spin is quite dramatic and can take an inattentive pilot by surprise.
Students should be familiar with the operating characteristics and the standard operating procedures for spin recovery in the POH of the airplane they are flying. The FAA has outlined a basic spin recovery technique consisting of six steps that can be followed in the absence of a manufacturer's recommended procedure:
1. Close the throttle, to eliminate power and minimize loss of altitude.
2. Neutralize the ailerons and determine the direction of the spin.
3. Input full opposite rudder to stop the rotation.
4. As the rotation slows, smoothly move the elevator forward to approximately the neutral position.
5. Neutralize the rudder to avoid entering a spin in the opposite direction.
6. Gradually apply enough elevator pressure to return to level flight. Caution should be exercised when applying aft elevator pressure during the recovery to avoid a secondary stall.
Jason is a private pilot departing from a remote airport with a short runway with trees at both ends. He reviewed and calculated his take-off performance data before starting the engine. Distracted by thoughts of a short-field takeoff with an obstacle, he failed to reset the elevator trim during his pre-departure checklist.
Just after takeoff, the airplane pitches up dramatically. He is now in the danger zone, and must react immediately to the imminent elevator trim stall. Pushing the yoke forward, he sees nothing but trees. In some flight scenarios there is no margin for error and the consequence may be harsh. There is no substitute for proper training, knowledge and skill.
A. 23.4% Takeoff/Initial Climb
B. 3.3% Climb
C. 15.7% Cruise
D. 2.6% Descent
E. 13.0% Maneuvering
F. 9.7% Approach
G. 24.1% Landing
8.2% Phase of flight not specified
This illustration shows the percentage of stall/spin accidents, which occur in various phases of flight. The majority of accidents occur in only 4 percent of the total duration of flight time, when approaching or departing airports. The workload is greatest at these times, which increases the chance of error.
REVIEW: Spin Hazards Due To Stalls
Most stall/spin accidents occur in the traffic pattern. It is important to recognize that the remainder of these accidents are accounted for in maneuvering phases of flight, which include what we commonly know as "buzzing." In any case, a combination of low altitude and low airspeed is the culprit, which leads pilots into the danger zone.
During low altitude maneuvering, whether or not in the traffic pattern, there is little room for recovery from a full stall, let alone a spin. The lack of recovery altitude, however, is not the cause of these accidents. It is the lack of knowledge of the risks, lack of judgment to avoid the danger zone, and lack of skill to escape it.
"It is possible to fly without motors, but not without knowledge and skill." - Wilbur Wright
A stall/spin also is a distinct possibility if an attempt is made to return to the departure runway following a power failure shortly after takeoff. A curious perception of conditions grips the pilot in this circumstance. Apparently, before over-flying the end of the runway, the pilot does not consider turning back when a power failure occurs. The pilot correctly judges that he has to land on the remaining runway ahead, or on the terrain beyond. But after the runway end disappears beneath the nose, the imprudent pilot is deceived into thinking that having departed the airport boundary and with the entire runway surface behind, adequate altitude exists for safely reversing course and touching down. The steep turn used for such a maneuver can easily result in a crossed-control or accelerated stall.
If it is necessary to convince your students of its dangers, show them this maneuver at altitude. Show them that even with better-than-average pilot technique, the maneuver is costly in terms of altitude, distance, and controllability.
The crossed-control stall might also occur when a turn to final is overshot. The danger zone is entered when rudder is used to yaw the airplane toward the runway, and opposite aileron is applied to prevent the resulting over-banking tendency. It is the same mishandling of the controls as in the attempt to return to the runway following a power failure. Note that in both cases, remaining clear of the danger zone is a matter of judgment and pilot skill.
Students should understand the importance and purpose of stall maneuvers, and experience them before beginning traffic pattern work. The motivation to understand them is the need to recognize the approaching stall and recover to normal flight before a stall occurs, thus precluding the spin. A brief discussion of accident statistics may be a good way to convince the student of the relevance of this training.
A spin is defined by three distinct phases: the incipient phase, the fully developed phase and the recovery.
REVIEW: Spin AerodynamicsCause and Phases of a Spin· Stalled Condition - A spin starts from an uncoordinated stall. · Incipient Phase - Beginning or onset of the spin. The incipient spin can be initiated from almost any flight attitude during slow flight. · Fully Developed Phase - Autorotation marked by high rate of descent at a very slow airspeed. · Recovery - Requires specific control input as described in AC61-67B.
Your students may already possess some knowledge, and many misconceptions, about spins. Some of your more advanced students may have performed spins. However, you will still need to review spin aerodynamics with all of your students. When applying for an initial flight instructor certificate, your CFI students need to accomplish spin training in accordance with section 61.183.
"The reason birds can fly and we can't is simply that they have perfect faith, for to have faith is to have wings." - Sir James Matthew Barrie
Your students need to understand that during an uncoordinated stall, the resulting roll and slip of the airplane creates a yawing moment, caused by the weathervane effect. This yawing moment in conjunction with the uncoordinated condition, causes the stall of one wing before another, which results in a roll. The ensuing roll will occur in the direction of the rudder, and is the precursor to the incipient phase of a spin. The combination of rolling, slipping, and yawing produces the autorotation characteristic of the spin.
1. The yawing motion is due to the application of the left rudder and high induced drag on the left wing.
2. The slip is due to crossed controls (left rudder, right aileron up.)
3. The roll is due to a higher angle of attack on the left wing, causing it to stall before the right wing.
4. The roll is due to differential lift. Since the right wing is not completely stalled, it produces some lift.
5. Autorotation is due to differential lift. Since the left wing is completely stalled, it induces more drag and creates little lift.
INCIPIENT SPIN
· Lasts about 4 to 6 seconds in light aircraft.
· Approximately 2 turns.
FULLY DEVELOPED SPIN
· Airspeed, vertical speed, and rate of rotation are stabilized.
· Small training aircraft lose approximately 500 feet per 3 second turn.
RECOVERY
· Wings regain lift.
· Training aircraft usually recover in about 1/4 to 1/2 of a turn after anti-spin inputs are applied.
A spin induced by an uncoordinated stall is defined by three distinct phases: the incipient phase, the fully developed phase and recovery. In the incipient phase of a spin, the motions about the vertical and longitudinal axes are developing and changing. During the fully developed phase, the airspeed and motions are stabilized, producing a consistent cycle of rotation, and the flight path is nearly vertical.
When you introduce spins to your CFI students, keep in mind that your objective is broader than simply teaching your students spin safety. You should have your CFI students teach stall/spin awareness first, then demonstrate spin entries, spins, and spin recoveries. Caution should be exercised with regard to spin training. You should review aircraft categories and the applicability of spin certification.
One source of confusion stems from the fact that 14 CFR part 23 permits airplanes to be type-certified in more than one category. As always, it is imperative that you and your students review the appropriate AFM or POH prior to conducting spin training in a particular airplane.
Aviation is changing rapidly and as an aviation instructor you must continue to develop your knowledge and skills in order to teach successfully in this dynamic environment. Your philosophy of teaching can remain unchanged throughout your career but in order to meet the needs of your students, the methods you use to deliver your lessons must be fluid and evolve to create a learning environment in which your students can flourish.
Safety of flight is a primary responsibility; when in the practice area you and your students must be vigilant for other aircraft. Making clearing turn reduces the risk of encountering conflicting traffic.
Your students will learn from what you say as well as from what you do, so being meticulous about flight safety will teach them to do the same.
