Par 2-2 Page 6
d. Proper aeronautical decisionmaking skills to avoid stall events (e.g., effective analysis, awareness, resource management, mitigation strategies, and breaking the error chain through airmanship and sound judgment).
e. Proper recognition of an impending stall in varied conditions and configurations.
f. The effects of autoflight, flight envelope protection in normal and degraded modes, and unexpected disconnects of the autopilot or autothrottle/autothrust.
g. Proper recognition of when the flight condition has transitioned from the prevention phase and into the recovery phase.
h. Proper application of the stall recovery procedure.
2-3. TRAINING REQUIREMENTS (§§ 121.418, 121.419, 121.423, 121.424, and 121.427).
While basic aerodynamics and stall training are accomplished as part of a pilot’s private, commercial, and airline transport pilot (ATP) certifications, it is important to reinforce this basic training throughout a pilot’s career. Training providers should ensure that pilots are thoroughly familiar with the characteristics associated with the specific airplane. Training providers should also understand that some pilots may need to unlearn previous stall recovery procedures based on their prior experience. This AC describes the stall event training that a pilot should receive when employed by a part 121 air carrier. The essential concepts of stall training should be standalone training. Once the concepts are mastered, stall training may be incorporated into other training areas (e.g., CRM, adverse weather training, etc.). Air carriers must include stall event training for pilots during:
• Initial training,
• Transition training,
• Differences and related aircraft differences training (if differences exist),
• Upgrade training,
• Requalification training (if applicable), and
• Recurrent training.
2-4. INSTRUCTOR/EVALUATOR STANDARDIZATION (§§ 121.413 and 121.414).
Instructors and evaluators should receive training in the subject areas contained in this AC.
Knowledge of these subject areas ensures accurate stall event training and minimizes the risk of negative transfer of training.
a. Instructor/Evaluator Training. Instructor/evaluator training should focus on the practical application of these principles and the evaluation of a pilot’s understanding of the airplane’s operating characteristics. Instructors should:
• Demonstrate knowledge of all subject areas of this advisory circular;
• Demonstrate proficiency in all skill areas of this advisory circular; and
• Demonstrate proficiency in conducting maneuver-based and scenario-based stall prevention and recovery training.
Par 2-4 Page 7 (and 8)
b. Understanding of FFS Limitations. Instructors/evaluators must have a clear understanding of the FFS limitations that may influence the stall event training and checking including:
• Significant deviations from a particular FFS’s acceptable training envelope; and
• G loading awareness/accelerated stall—factors absent from the FFS’s cues that could be experienced in flight and the effect on the airplane behavior and recovery considerations.
2-5. RECOVERY PROCEDURES. This AC emphasizes using the same procedure for both stall prevention and stall recovery. Previous training and evaluation profiles that required a specific set of pilot-initiated, precise entry procedures have been replaced with realistic scenarios. Additionally, recovery profiles that emphasize zero or minimal altitude loss and the immediate advancement of maximum thrust have been eliminated. Recovery procedures now emphasize:
• Disconnecting the autopilot and autothrottle/autothrust systems,
• Reducing the airplane’s AOA immediately,
• Controlling roll after reducing the airplane AOA,
• Managing thrust appropriately, and
• Returning the airplane to the desired flightpath.
2-6. FLIGHT STANDARDIZATION BOARD (FSB) REPORTS. When developing stall prevention and recovery training, air carriers should consult the FSB report, if available, for the specific airplane type. The Training Areas of Special Emphasis, and any other recommendations pertaining to stall, should be reviewed.
Par 3-1 Page 9 CHAPTER 3. GROUND/ACADEMIC TRAINING
3-1. ACADEMIC KNOWLEDGE. Academic instruction establishes the foundation from which situational awareness, insight, knowledge, and skills are developed. Academic knowledge should proceed from the general to the specific. Including accident, incident, Aviation Safety Action Program (ASAP), flight operations quality assurance (FOQA), or Aviation Safety Reporting System (ASRS) data from stall-related events is a useful way of bringing theoretical knowledge into an operational perspective.
NOTE: The FAA strongly recommends incorporation of applicable sections of the Airplane Upset Recovery Training Aid (AURTA) Revision 2 on stall aerodynamics and high altitude stalls into air carrier stall training programs.
The AURTA Revision 2 is available at: http://www.faa.gov/other_visit/ aviation_industry/airline_operators/training/media/AP_UpsetRecovery_Boo
k.pdf.
3-2. KNOWLEDGE AREAS. The following knowledge areas should be included in all airplane training curriculums:
a. Recovery Procedures. Proper recovery procedures should emphasize that a reduction of the AOA is required to initiate recovery of all stall events. Additional information to incorporate into recovery training includes:
(1) Recognition of impending stall indications and understanding of the need to initiate the stall recovery procedure at an impending stall.
(2) Recognition of full stall indication (see paragraph 1-7) with the realization that most swept-wing transport category aircraft exhibit full stall characteristics different from those typically experienced in General Aviation (GA) aircraft used during certification training.
(3) For airplanes equipped with a stick pusher, recommended recovery actions in response to stick pusher activation.
(4) Avoiding cyclical or oscillatory control inputs to prevent exceeding the structural limits of the airplane.
(5) Structural considerations, including explanation of limit load, ultimate load, and the dangers of combining accelerative and rolling moments (i.e., the rolling pull) during recovery.
(6) The necessity for smooth, deliberate, and positive control inputs to avoid unacceptable load factors and secondary stalls.
(7) AOA must be reduced prior to controlling roll.
(8) Effectiveness of control surfaces and the order in which the control surfaces lose and regain their effectiveness (e.g., spoilers, ailerons, etc.).
Par 3-2 Page 10
(9) If a terrain awareness warning system (TAWS) warning is encountered during recovery from a low altitude stall event, recovery from the stall warning should take precedence.
Once the airplane recovers from the stall event, then execute the TAWS escape maneuver.
b. Factors Leading to a Stall Event. An awareness of the factors that may lead to a stall event during automated and manual flight operations including:
• AOA versus pitch angle;
• Rate of onset including rate of airspeed decay (both low and high);
• Airplane configuration and condition including weight, center of gravity (CG), landing gear, flaps/slats, spoilers/speed brakes, etc.;
• Asymmetric loading including thrust asymmetries, wing loading due to roll or yaw transients or uncoordinated flight;
• G loading;
• Bank angle;
• Thrust and lift vectors;
• Thrust required versus thrust available;
• Wind shear;
• Altitude;
• Mach effects;
• Situational Awareness;
• Mode confusion, including unexpected/unannounced mode changes;
• Unexpected transition from automated to manual flight; and
• Contamination (ice), including the effect of icing on stall speed and stall warnings.
c. Airplane-Specific Systems Knowledge.
(1) Understanding of AOA indicators (if installed) or interpretation of other representations of AOA such as pitch-limit indicators or speed display symbology that can assist in stall prevention.
(2) Specific stall and low-speed buffet characteristics unique to the airplane type and any implications for the expected flight operations and airplane-specific stall recovery procedure
(e.g., underwing mounted engines, t-tail, propellers, etc.).
(3) For envelope protected airplanes, stall protection capabilities in normal and degraded modes.
(4) Thrust settings and its application.
(5) Autothrottle/autothrust protection.
(6) Awareness of autoflight mode indications.
(7) Incorrect use of (including input errors) flightpath automated systems.
Par 3-2 Page 11 (and 12)
(8) Operation and function of stall protection systems in normal, abnormal, and emergency situations, including the hazards of overriding or ignoring stall protection system indications. Awareness of the factors that may lead such systems to fail, as well as degraded modes, indications, or behaviors that may occur with system failures.
d. High Altitude Considerations.
(1) Buffet boundary and margins in flight planning and operational flying.
(2) Lower margins for stall onset and recovery (i.e., coffin corner) and possible buffet cueing differences on the high-speed versus the low-speed margin.
(3) Principles of high altitude aerodynamics, performance capabilities, and limitations;
including high altitude operations and flight techniques (i.e., the need to avoid secondary stall by extended nose-down recovery, compared to lower altitudes).
(4) Differences in airplane performance (e.g., thrust available) during high versus low altitude operations, the effects of those differences on stall recovery, and the anticipated altitude loss during a recovery.
e. Airplane Certification Differences. Differences between transport category airplane certification and GA airplane certification regarding use of flight controls at high AOA.
For example, if the roll control system is compromised and the ailerons are unable to produce the required roll recovery, the rudder may be used with care during stall prevention and recovery. To maintain structural integrity, it is important to guard against control reversals—avoid rapid fullscale reversal of control deflections.
f. Example Events. Although significant emphasis should be placed on preventing stall events, it is important for pilots to understand that, although rare, stall events continue to occur.
Studying the causes and contributing factors of stall events give pilots more knowledge to help prevent or if necessary, recover from a stall event. A review of stall-related accidents, incidents, ASAP, FOQA, and ASRS data for the specific airplane type or class should be included in ground training.
Par 4-1 Page 13 CHAPTER 4. STALL PREVENTION TRAINING AND CHECKING
4-1. GENERAL. This chapter provides specific information for training and checking stall prevention (formerly approach-to-stall), which is required by 14 CFR part 121 appendices E and F. Prevention training provides pilots with the skills to recognize conditions that increase the likelihood of a stall event if not effectively managed. Prevention training must include the operator’s standard operating procedures (SOP) and CRM for proper avoidance techniques and threat mitigation strategies.
4-2. SIMULATOR TRAINING (§ 121.424). Training providers are encouraged to use the highest level FFS available when developing their stall prevention and recovery training curriculums. The primary emphasis is to provide the pilot with the most realistic environment possible during impending stall training and checking. Simulator training can either be maneuver-based or scenario-based; checking should be maneuver-based. Both methods are discussed in detail below.
a. Low Speed Alert. During maneuver-based stall prevention training and checking, pilots should apply the stall recovery at stall warning (see paragraph 1-7), not at a low speed alert or low energy alert (e.g., “airspeed low, airspeed low,” “speed, speed, speed,” or a flashing airspeed warning cue). Initiating the stall recovery at a low airspeed alert in maneuver-based stall prevention training or checking does not satisfy the objective of training or checking the stall recovery procedures. During scenario-based stall prevention training, pilots should return the aircraft to a desired aircraft state if any low airspeed or low energy alert is encountered.
NOTE: Instructors and check pilots must be familiar with the limitations of a particular FSTD and ensure that all pilots undergoing training and checking are aware of these limitations to mitigate negative transfer of training.
b. Maneuver-Based Training. This training focuses on the mastery of an individual task or tasks. Maneuver-based training applies to both prevention and recovery training. It should emphasize the development of the required perception and motor skills to satisfactorily accomplish stall prevention and recovery. Limited emphasis should be placed on decisionmaking skills during maneuver-based training.
(1) Configurations. Maneuver-based training should include impending stalls in the following configurations required by part 121 appendix E and § 121.424:
• Takeoff or maneuvering,
• Clean, and
• Landing.
(2) Conditions. Impending stalls in the above three configurations should be trained using the following conditions, as appropriate:
Par 4-2 Page 14
(a) Level flight and turns using a bank angle of 15 to 30 degrees;
(b) Manual and automated (autopilot and/or autothrottle/autothrust, if installed) flight;
NOTE: It may be difficult to use autothrottle/autothrust during maneuver-based training, since the autothrottle/autothrust is usually disconnected and thrust reduced to idle. However, it is important to teach disconnecting the autopilot and autothrottle/autothrust during stall prevention training and, if the integration of the autoflight systems permit it, to develop scenarios with the autothrottle/autothrust engaged.
(c) Visual and instrument flight conditions;
(d) High altitudes near the airplane’s maximum altitude and low altitudes within 500 feet above ground level (AGL); and
(e) Various weights and CG locations within airplane limitations.
(3) Emphasis Items. The following items should be emphasized during maneuver-based training:
(a) Recovery Procedures.
1. Reducing AOA is the proper way to recover from a stall event. Pilots must accept that reducing the airplane’s AOA will normally result in altitude loss. The amount of altitude loss will be affected by the airplane’s operational environment (e.g., entry altitude, airplane weight, density altitude, bank angle, airplane configuration, etc.). At high altitudes, stall recovery will likely require losing several thousand feet.
2. Declare an emergency if necessary. Do not delay recovery due to degrading airspeed or a stall event to obtain air traffic control (ATC) clearance to a lower altitude.
3. Understanding that early recognition and return of the airplane to a controlled and safe state are the most important factors in surviving stall events. Only after recovering to a safe maneuvering speed and AOA should the pilot focus on establishing an assigned heading, altitude, and airspeed.
4. An abrupt pitch-up or trim change can occur when the autopilot unexpectedly disconnects during a stall event. This dramatic pitch-up or trim change typically adds an unexpected physical challenge to the pilot when trying to reduce AOA. In some airplanes, this may be aggravated by an additional pitch up when the pilot increases thrust during stall recovery.
5. Secondary stall warnings are indicative of a pilot prioritizing minimum loss of altitude over proper stall recovery or flight control inputs that are too aggressive. In some airplanes, depending on AOA representations, it may be difficult to determine the point where the pitch can begin to be increased and a momentary secondary stall warning may be
Par 4-2 Page 15 encountered. A secondary stall warning is acceptable as long as AOA is promptly reduced and the airplane’s limitations are not exceeded.
6. Air carriers should develop stall prevention evaluation strategies that are a direct reflection to the aircraft type. Between different aircraft types and variations of an aircraft type there is a broad range of available airspeed/AOA/energy information to the pilot. Therefore, an evaluation of a stall prevention with an attitude direction indicator (ADI) that has sufficient information to determine the flight envelope (pitch limit indicators, speed tape with low speed awareness, airspeed trend needles) should be more stringent. Obviously with this expectation, the assumption is made that the air carrier's stall training prepares the pilot to interpret this information in low energy states. Conversely, a stall prevention evaluation of a pilot that has limited flight envelope information could allow momentary reactivations of the stall warning after the pilot has reduced the AOA to cease the stall warning and is attempting to return the aircraft to safe flight.
(b) Factors Leading to a Stall Event.
1. How changes to factors such as weight, G loading, CG, bank angle, altitude, and icing affect the handling characteristics and stall speeds of the airplane.
2. Inappropriate use or inadequate monitoring of autoflight modes can be a contributing factor to a stall event. For example, climbing in vertical speed can lead to a stall event when pilots do not notice the airspeed reducing as the altitude increases; whereas, climbing in modes such as indicated airspeed or flight level change can protect against unnoticed deceleration in a climb.
(c) Airplane-Specific Knowledge.
1. Impending stall characteristics for the specific airplane, including buffeting of a severity that may make it difficult to read the instruments.
2. Review of AOA indicators (if installed) or interpretation of other representations of AOA such as pitch-limit indicators or speed display symbology that can assist in stall prevention.
3. Noises associated with stick shakers, autopilot, and autothrottle/autothrust disconnect alarms can cause confusion in the cockpit.
4. The effects of malfunctioning or deferred equipment on stall protection and stick pusher systems.
(d) Altitude Effects.
1. Differences between high and low altitude stalls, pitch rate sensitivity of flight controls (due to lack of aerodynamic damping), and amount of altitude loss required for recovery.
Par 4-2 Page 16
2. Thrust available for recovery, and lack of airflow through engines at high AOA (reinforces reduction of AOA must precede any increase of thrust).
c. Scenario-Based Training (SBT). The goal of SBT is to develop decisionmaking skills relating to stall prevention and recovery during Line-Oriented Flight Training (LOFT). Emphasis should be placed on preventing conditions that may lead to a stall event. SBT would normally be used after a pilot demonstrates proficiency in maneuver-based training and during advanced stages of training, such as upgrade training and recurrent training.
(1) Scenarios. When possible, scenarios should include accident, incident, ASAP, FOQA, and/or ASRS data to provide realistic opportunities to see how threat situations may develop and how they should be managed during line operations. Sample SBT lesson plans are provided in Appendix 3.
(2) Briefing. Pilots should not normally be briefed that they are receiving SBT. The concept is line-oriented flying, which allows the pilots to recognize and manage the expected or unexpected stall threats as they develop during normal operations. However, situations may arise where pilots exhibit excellent stall prevention skills and initiate a recovery prior to the complete unfolding of a scenario. That is the desired objective. In those instances, the instructor has the discretion whether to repeat the scenario and then showing and discussing how the many cues typically cascade as the event progresses. Such explanations can reinforce a pilot’s knowledge and allow sharpening of awareness and prevention skills.
4-3. USING SURPRISE IN TRAINING. Surprise has been a factor in stall incidents and accidents. Although it may be difficult to create surprise in the training environment, if achieved, surprise events may provide a powerful lesson for the crew. The goal of using surprise in training is to provide the crew with a surprise experience to reinforce timely application of the effective recovery technique under potentially confusing circumstances. Considerable care should be used in surprise training to avoid a negative learning experience. Surprise should not be used during checking. Stall prevention training should incorporate event conditions and variables typical of an unintentional stall that are likely to result in surprise due to the unexpected stall development, presentation, and behavior.
4-4. CHECKING PARAMETERS. The check pilot is responsible for establishing the flight conditions associated with the impending stall configuration being checked. The pilot may fly the entry profile but is not being checked on the entry, except for recognition of the deteriorating flight situation. The satisfactory completion of the event is based on the pilot’s timely and proper recognition of the impending stall and then proper application of the stall recovery procedure.
4-5. CHECKING CRITERIA. Checking of prevention, recognition, and recovery from an impending stall should be evaluated on the timely and proper response to the impending stall including effective use of available energy; the criteria should not focus on altitude loss. The check pilot should consider the variables present at the time of the impending stall and their effect on the recovery. Checking criteria are:
Par 4-5 Page 17 (and 18)
• Prompt recognition of impending stall,
• Correct application of the stall recovery procedure, and
• Recovering without exceeding the airplane’s limitations.
NOTE: Training providers should adjust their impending stall checking criteria as appropriate and train their check pilots in these changes. The primary goal of checking should be to evaluate a pilot’s immediate recognition and response to an impending stall and their timely, correct accomplishment of the stall recovery procedure.
4-6. REALISTIC SETTINGS FOR CHECKING. In the FFS, the stall prevention checking module should be maneuver-based with an entry altitude consistent with normal operating environments. The entry parameters, including Weight and Balance (W&B), should be within airplane limitations to ensure adequate performance for recovery from an impending stall.
During checking, the pilot should be checked on recovering from the impending stall.
4-7. DEBRIEFING. Debriefing pilots on their performance in both training and checking is essential. Providing pilots with specific feedback on the recovery procedures including whether recovery control inputs were excessive, insufficient, or had cyclic control reversals will assist pilots in improving their recovery procedures and will also address the implications of G loading differences in simulation. If the recovery exceeds the limitations of the FSTD, instructors must make the pilot aware to avoid negative transfer of training.