richstowell1, Author at Aviation Ideas and Discussion!

A Pilot’s View of Energy Management!

This blog was formatted from comments on last week's Energy Management blog (>35, pitch/power discussion). Rich Stowell checked in and his comments, reprinted here, are especially valuable for all pilots and educators. His FREE "Learn to Turn" course offers even more extensive guidance.

While a good start, the new “Energy Management” chapter in the 2021 FAA Airplane Flying Handbook devolves into the usual trap of a designer-oriented approach to training. As pointed out by Langewiesche in Stick and Rudder, “What is wrong with ‘Theory of Flight,’ from the pilot’s point of view, is not that it is theory. What’s wrong is that it is the theory of the wrong thing—it usually becomes a theory of building the airplane rather than of flying it.”

The first principle of flying light airplanes is “Pitch + Power = Performance.” This succinct statement points to energy management. But it is so much more than that. Substitute angle of attack (AOA) for Pitch; thus, “AOA + Power = Performance.” Airspeed (V) and G-load (G) are proxies for AOA. Hence, “V + G + P = Performance.”

This simple statement takes us to the two types of airplane performance we care about: Climb Performance and Maneuvering Performance. The V-P diagram illustrates climb performance. In this context, “climb” can be positive (climbing), zero (level), or negative (descending). We can talk about energy; which axis is controlled with throttle; which axis, with elevator; what happens on the back side, the front side, and way on the front side. We can include excess power (Pxs = Pav – Pre), which translates into rate of climb (ROC).

We can overlay and discuss critical V-speeds such as Vm, Vs, Vh, and Vne (vertical lines drawn on the diagram); Ve and Vy (horizontal lines); and Vx and Vbg/Vbr (tangent lines). We can discuss the effects on the performance of things such as airplane configuration, density altitude, and bank angle.

We can map out a go-around. Say, for example, we add go-around power while at 60 knots. Achieving max ROC is important in this example, which is a touch over 70 knots. Pushing the elevator control forward allows us to climb at a faster rate. This is counterintuitive (just like stall recovery) unless we understand the V-P relationship. Similarly, there are speeds on either side of Vy that, with go-around power applied, result in the same ROC albeit slower than max ROC. In one instance, we would have to push to speed up and thereby climb at a faster rate; in the other, pull to slow down and thereby also climb at a faster rate. Again counterintuitive, but normal in terms of the V-P relationship. We can correlate key speeds like Vy with their corresponding pitch attitudes, too, should we ever lose our airspeed indicator.

We can even map out and discuss a complete engine failure (P = 0), in which case the V-P diagram flips and becomes a Rate of Descent vs. Speed diagram (ROD-V). Correlate the glide attitude with your best glide speed here, too.

The V-G diagram, on the other hand, illustrates maneuvering performance within the confines of the airplane’s aerodynamic and structural limits. The same Vne line from V-P transfers to V-G. The same Vs line transfers as well, but the V-G diagram shows us all the stall speeds from zero G to the design limit G.

Whatever we say about the V-P diagram must be consistent with, and transferrable to, the V-G diagram and vice versa. Does anyone think we can substitute power settings along the V-axis on the V-G diagram, making it a P-G diagram?

When they happen to be discussed, V-P and V-G are presented as totally unrelated pictures. The reality is that three parameters tell us what the airplane is doing at any point in flight: V, G, & P.

Since V-P and V-G diagrams share the same speed axis, imagine connecting the two diagrams at right angles to each other along the V-axis. Imagine an airplane in flight in the space between the two diagrams. Projecting the airplane’s shadow onto the V-P diagram informs us about its climb performance at that moment. Likewise, projecting the airplane’s shadow onto the V-G diagram tells us how it is maneuvering at that moment. Alternatively, we might think of the V-G diagram as a toaster with an infinite number of thin slots to accept an infinite number of thin slices of V-P bread. The graphic shows this concept for level flight at 1G. This slice of the envelope is bounded by the 1G stall speed, Vne, and the available power.

The interplay between pitch and power on performance should be clear, as should the primary use of elevator and throttle controls. Also note that pitch is assigned as AOA/speed control and power as altitude control during the most critical of flight operations:

The mountain, canyon, and backcountry flight environments (Mountain, Canyon, and Backcountry Flying, Amy L. Hoover & R.K. Williams; Mountain and Canyon Flying Training Manual, Lori MacNichol)
The technical logic of airplane performance (Performance of Light Aircraft, John T. Lowry)
AOPA articles (Fatal Instinct and Power and Pitch, Barry Schiff)
The flippers and the throttle (Stick and Rudder, Wolfgang Langewiesche)
Fundamentals of flying technique (FAA)
Fundamentals of stall recovery (FAA)
Go-around/Rejected Landing (FAA)

Likewise, airplane manufacturers assign pitch for AOA/speed control and power for altitude control during critical flight operations and emergencies in their airplanes. For example, see the amplified procedures in the Cessna 172P:

Short field landing
Landing without elevator control
Glassy water landing (floatplane version)
Engine failure
Emergency descent through clouds
Recovery from a spiral dive (in clouds)

Teaching Pitch and Power

Pitch. The elevator control moves fore and aft. The airplane’s response is seen as head-to-feet movement by the pilot. The primary effect is on angle of attack, which presents as changes in at least a couple of these: V, G, attitude, flight path. Possible secondary effects might include changes in rigging and engine effects, gyroscopic precession, angle of bank, and altitude.

Power. The throttle moves fore and aft. The primary effect is to move the airplane here-to-there (taxi from one location to another on the airport; fly from airport A to airport B; climb or descend from one altitude to another). Possible secondary effects might include changes in torque, p-factor, slipstream, and airspeed.

Do we inadvertently, negatively reinforce “use the secondary effect of pitch for altitude” as the norm, which by default makes all the above scenarios the exceptions? Or is “using the secondary effect of pitch for altitude” really the exception, especially since we must be in just the right slice of the envelope, close to the correct altitude profile already, and with speed that we either don’t need or don’t really care about to achieve the desired effect?

Does our approach to teaching the V-P relationship along with the trainee’s practical experience spent mostly in one part of the envelope contribute to the potentially dangerous pull response in other parts of the envelope? How do we push learning to the correlation level for the entire performance envelope?

Stripping away the apparent complexity in the FAA’s energy management chapter—especially with regard to the most critical energy state scenarios—returns us to the primary roles of pitch and power as illustrated on V-P and V-G diagrams. Hence my motto: “Pitch for the speed you need.”

The “SAFE Strategies” was just published with SAFE Board Candidates (please vote) and details on #OSH22. Our SAFE dinner is on campus at the EAA Partner Resource Center

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“Technedure” and Spin Recoveries

I am in Florida presenting SAFE CFI-PRO™ to a flight academy here. Please read (and comment on) this very interesting give and take on spin recovery and the general topic of “technedure” – when a personal technique becomes an accepted – and passed on – procedure. (and a bit about aircraft manuals)

First read Natalie Bingham Hoover, AOPA Pilot, March 2020

And here is a reply from SAFE Founding and lifetime member

Rich Stowell

Master Instructor Emeritus
34,700 spin entries/recoveries in 240 single-engine airplanes representing 44 types. AOPA Member since 1984

While the article by Instructor Hoover raises several interesting points, her use of the PARE acronym as an example of issues with so-called “technedures” highlights persistent misunderstandings among pilots about spin recovery.

The PARE acronym evolved as part of the Stall/Spin Awareness module taught in our Emergency Maneuver Training program. The acronym has been around for 30-odd years now, and its use in primary flight training has become widespread. The acronym and associated recovery checklist merely restate tried-and-true NASA Standard spin recovery actions—actions that were first identified 84 years ago by NACA (the forerunner to NASA). NASA confirmed the veracity of these actions between 1977 and 1989, during the most comprehensive research program ever undertaken regarding spins in light, single-engine airplanes.

As detailed in my book, “The Light Airplane Pilot’s Guide to Stall/Spin Awareness,” use of PARE comes with clearly defined caveats. Among other requirements, the acronym and associated checklist must be:

Applied in the context of typical, light, single-engine airplanes (which make up three-quarters of the general aviation fleet);
Applied only in conjunction with tried-and-true NASA Standard spin recovery actions; and,
Used for educational purposes by ground and flight instructors as part of civilian stall/spin awareness training.

That some in general aviation would suggest that PARE could be applicable to military aircraft not only misrepresents the acronym, but also illustrates operational human errors and omissions that are being committed during flight training.

If procedure is the “what,” technique is the “how and when.” Thus the recommendation “power off” is procedure. Techniques include closing the throttle, pulling the mixture to idle cutoff, or turning the mags off. Each satisfies the procedure. With all things equal, the question becomes, “which technique is superior?” Further, as soon as recovery actions are embellished with words such as “before,” “simultaneously,” or “after,” or arranged in a numbered list, procedure has been infused with technique— the very definition of technedure. Published spin recovery information—including PARE—is technedure. So the question remains: Which spin recovery techniques are superior?

Instructor Hoover compares the manufacturer-supplied spin recovery technedures for the Piper Tomahawk and the Cessna 152. Both manufacturers adhere to “power off.” The technedure in the Tomahawk manual places this action as Step (d) with the wording, “close the throttle.” In contrast, Cessna technedures for the 152 range from listing the power action in:

Step 2 with “retard the throttle to idle position” in the airplane manual; but,
Step 1 with “verify ailerons are neutral and throttle is closed” on the cockpit placard; but,
Step (a) with “verify that ailerons are neutral and throttle is in idle position” in the pamphlet, “Spin Characteristics of Cessna Models 150, A150, 152, A152,172, R172 & 177.”

Some manufacturers don’t even mention power. Examples include the Robin R 2100, Grob G 115C, de Havilland DHC-2 Beaver, and Great Lakes 2T-1A-2. Are the manufacturers implying that power setting is irrelevant during spin recovery in those airplanes? Or are the manufacturers assuming that power is already off? Are you willing to gamble that spin recovery won’t be delayed or thwarted altogether because the power was left on? Power is known to aggravate spin behavior; thus, taking the power off and doing it earlier rather than later in the recovery process is a superior recovery technique, whether or not the manufacturer includes it in its published technedure.

A deep dive into certification spin testing also reveals the following:

The 1989 and 1993 versions of the “Flight Test Guide for Certification of Part 23 Airplanes” recommend the use of NASA Standard spin recovery, i.e., “Recoveries should consist of throttle reduced to idle, ailerons neutralized, full opposite rudder, followed by forward elevator control…unless the manufacturer determines the need for another procedure.”
- Ninety-four percent of spin test pilots believe the actions listed above are the most effective for spin recovery in typical, light, single-engine airplanes.
- The wording “unless the manufacturer determines the need for another procedure” was deleted in the 2003 revision of the “Flight Test Guide.” This wording does not appear in the 2011 revision, either.
Sixty-three percent of spin test pilots said it is not normal practice to try to find the optimum sequencing of spin recovery actions for a given airplane during spin testing for certification.
Fewer than half of spin test pilots believe that flight manuals adequately present spin recovery information.
Little to no guidance is provided regarding how spin recovery information should be presented to pilots. The typical Beechcraft spin recovery technedure, for example, is not listed chronologically even though a sequence of events is unmistakable: “Ailerons should be neutral and throttle closed at all times during recovery [emphasis mine]” appears after the pilot “execute[s] a smooth pullout” once rotation stops.

Should we continually question what we think we know? Absolutely! Do instructors need to do a better job of pointing out technique to their students, including providing some justification as to why they prefer a particular technique? Yes! And while it can be difficult to separate good information from bad, instructors need to remain vigilant against spreading inaccurate or incomplete information.

The most effective technedures for spin recovery in typical, light, single-engine airplanes have been known for a long time. Do some exceptions to the NASA Standard exist even among single-engine airplanes? Of course. But does that justify perpetuating the status quo, where manufacturers and instructors alike deliver critical spin information without regard to spin dynamics, consistency, or human factors?

SAFE CFI-PRO™ workshop is open to every aviation educator at every level (even if you are working on your CFI?) June10/11 at Sporty’s Pilot Shop.

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WANTED: Angle of Attack Managers

This is one in a series of posts by special guest authors about SAFE’s new CFI-PROficiency Initiative™ (aka SAFE CFI-PRO™). The goal of the initiative is to make good aviation educators great!

Aviators, airmen, aviatrices—a few of the other words used to describe pilots. Yet none of these words reflect what we really do. Ultimately, pilots are angle of attack managers. Let’s have another look at AOA.

As David St. George notes in “Invisible Angle of Attack,” AOA is the difference between where the airplane is pointing and where it is going. Wolfgang Langewiesche describes the importance of AOA thus:

“If you had only 2 hours in which to explain the airplane to a student pilot, [AOA] is what you would have to explain. It is almost literally all there is to flight. It explains all about the climb, the glide, and level flight; much about the turn; practically all about the ordinary stall, the power stall, the spin. It takes the puzzlement out of such maneuvers as the nose-high power approach; it is the story of the landing.”

AOA implies two things: wind and an object around which the wind is flowing. Most everyone has played with AOA before. Remember sticking your hand out of the car window when you were a kid? What happened when you tilted your hand into the oncoming wind? “It went up!” is the common response. Reflect more deeply on the experience, however, and you’ll notice that your hand actually moved upward and backward. If we want to get technical about it, we could call the “up” part Lift and the “back” part Drag.

We’ve all seen examples of unusual things being forced to fly, too. For example, tornado-strength winds can cause even the most reluctant Holstein to go airborne.

A high velocity jet of air precisely aimed at a Snap-on screwdriver can cause it to hover (courtesy of SAFE member Shane Vande Voort—please don’t try this at home!).

And though we might describe a wing as having a “top” and a “bottom,” Lift- and Drag-producing AOAs are possible on either side.

AOA is discussed primarily in the context of the airplane’s main wing. But at the correlation level of learning, we see the entire airplane as an assembly of wings all of which are subject to the principles of AOA. The propeller, for instance, is a rotating wing. Main and jury struts are often symmetrical wings streamlined to minimize drag. “Aileron” is French for “little wing.” And our primary flight controls are AOA controls. The elevator controls the AOA of the main wing (aka pitch control).

Ailerons control local AOAs (typically the outboard part of the wings, aka roll control).

Rudder controls the AOA of the fuselage (aka yaw control).

Our job as instructors is to teach our trainees how to manage these AOAs to achieve desired performance outcomes. Although AOA itself may be invisible, changes in AOA can be sensed and its trend interpreted. In the visual flight environment, this means coupling aeronautical knowledge with sight, sound, and feel to manage our controllable AOAs.

Before we climb into the airplane, for example, we know that the combination of a high power setting and a slow airspeed during the takeoff phase will yaw the airplane. But we want coordinated flight during this particular takeoff. That will require a certain amount of rudder to manage the AOA of the fuselage to cancel the yaw. What does yawed flight look like during takeoff? What does it sound like? What does it feel like? What does it look and feel like if we try to use aileron to correct for the yaw instead of rudder? All of these questions can be explored in the practice area without staring at the slip/skid ball. The lessons learned can be applied during subsequent takeoffs.

Whether it’s pitch, roll, or yaw, changes in AOA manifest as changes in one or more of the following: attitude, G-load, control pressure, control displacement, and often sound. In the case of elevator inputs, add airspeed to the list of cues.

For fun, test your understanding of AOA with the following thought experiments. Imagine you are at an airshow watching a competent aerobatic pilot fly a capable aerobatic airplane.

1. The airplane makes a knife-edge pass from your right to your left at precisely 90 degrees angle of bank.
a. Where is the nose of the airplane pointing relative to its flightpath, and how is the pilot making that happen?
b. What is the pilot doing with the elevator to make the airplane fly down the runway?
c. What is the AOA of the main wing?
d. What is the pilot feeling?

2. The airplane climbs along a perfect vertical line.
a. In order to remain on the upline before pivoting in a Hammerhead, what is the pilot doing with the elevator?
b. Ultimately, what is the AOA of the main wing during the upline?

Want to learn more ways to push learning to the correlation level? Attend SAFE’s inaugural CFI-PRO™ workshop in Frederick, MD on October 2–3, 2019!

Join SAFE to support our safety mission of generating aviation excellence in teaching and flying. Our amazing member benefits pay back your contribution (1/3 off your ForeFlight subscription)! Our FREE SAFE Toolkit App puts required pilot endorsements and experience requirements right on your smartphone and facilitate CFI+DPE teamwork. Our CFI insurance was developed specifically for CFI professionals (and is the best value in the business).

SAFE CFI-PRO™: Scenarios, Maneuvers, or Both?

This is one in a series of posts by special guest authors about SAFE's new CFI-PROficiency Initiative™ (aka SAFE CFI-PRO™). The goal of the initiative is to make good aviation educators great!

Rich Stowell authored many articles in the early 2000s on “The Problem with Flight Instruction” that helped precipitate the SAFE Pilot Training Reform Symposium in Atlanta. That SAFE initiative spawned the current FAA ACS. Now the focus is on raising the level of excellence among aviation educators with the new SAFE CFI-PRO Initiative.

Top instructors and examiners continually debate and lament the state of stick and rudder flying skills. The FAA flight training pendulum has swung from the traditional WWII maneuvers-based training (MBT) to the newer scenario-based training (SBT) standard. And though SBT is a vital part of risk management training and testing, inflight loss of control (LOC-I) continues to top the list of fatal accident categories. The number two occurrence category isn’t even close.

Should we resign ourselves to accepting LOC-I as inevitable? Or maybe the current focus on scenarios is as short-sighted as the focus on maneuvers once was? Perhaps aviation educators need to adopt a more balanced approach.

…what is chiefly needed is skill rather than machinery. – Wilbur Wright

Flight instructors teach in the psychomotor, cognitive, and affective domains. Maneuvers-based training falls in the psychomotor domain. It’s where pilots learn stick and rudder skills (aka manual flying skills). Scenario-based training overlaps the cognitive and affective domains. It’s where pilots learn aeronautical decision making skills.

Most anyone can learn specific patterns of movement. For instance, a person can follow steps laid out on the floor without ever looking in a mirror, getting a critique from a dance teacher, or listening to a beat. Does that make the person a dancer? Similarly, most anyone can learn how to apply a solution model to a scenario. A baseball fanatic with a grasp of analytics can choose statistically better options without having played the game. Is the fan a baseball player?

What does it take to train pilots capable of integrating body, mind, and emotion so the successful outcome of a flight is never in doubt? Memorizing a series of control movements without context, purpose, or rhythm won’t do that. As cognitive load increases, performance deteriorates and inputs become more spastic. Tackling complex scenarios without a solid foundation of stick and rudder skills won’t do it, either. Preoccupation with the mechanics of flying deflects mental focus from aeronautical decision making.

The psychomotor domain is the bridge to the other domains. We entice potential customers into aviation through the physical act of intro flights. Aviate, Navigate, Communicate is our most repeated mantra, with “fly the airplane” our default rule. The Aviation Instructor’s Handbook puts “Acquiring Skill Knowledge” several sections ahead of “Scenario-Based Training.” If word count is an indication, the skill section has nearly 40 percent more words than the scenario-based one. The handbook says skill acquisition is “the ability to instinctively perform certain maneuvers or tasks that require manual dexterity and precision [allowing] more time to concentrate on other essential duties such as navigation, communications with ATC facilities, and visual scanning for other aircraft.”

Developing competence in manual flying skills breeds confidence; injecting realistic scenarios counters overconfidence and develops better judgment. A path to follow to improve stick and rudder competency includes:

• Building from fundamental movements of the controls to skilled movements;
• Practicing manual skills often and with clear educational intention for growth; and,
• Striving to be able to do complex patterns of actions skillfully and automatically. [More here]

Could more technology be the answer to LOC-I? Is the purpose of technology to help well-trained pilots achieve peak performance with greater precision, or to conceal deficiencies in piloting skills?

Blue Threat author Tony Kern advises: “Error control will never be engineered out of existence with technology.” In fact, manual flying errors have increased because of overreliance on technology. This compelled the FAA to remind pilots to hand fly their aircraft more often in SAFO 13002 and SAFO 17007

Advisory Circulars 120-109A and 120-111 include templates for recovering from stalls and nose high and nose low attitudes. The first action listed in each case? Disengage the automation. The next steps in the procedures require (deeply ingrained) manual flying skills. And only greater proficiency and envelope expansion will give pilots fluid and immediate access to these often counterintuitive skills.

While the above ACs primarily target air carrier operations, they provide sound advice for general aviation pilots, too. When the time comes to prevent or recover from upsets that could lead to LOC-I, our lives, the lives of our trainees, and the lives of others will boil down to what the pilot does with the flight controls.

Stick and rudder skills will be relevant as long as flying involves pilots touching controls. Pilots interact with instructors throughout their flying careers; thus, improving the manual flying skills of instructors—and their ability to pass those skills on to others—is essential to reduce loss of control. This is why instructors are at the heart of the SAFE CFI-PRO Initiative.

Join SAFE to support our safety mission of generating aviation excellence in teaching and flying. Our amazing member benefits pay back your contribution (1/3 off your ForeFlight subscription)! Our FREE SAFE Toolkit App puts required pilot endorsements and experience requirements right on your smartphone and facilitate CFI+DPE teamwork. Our CFI insurance was developed specifically for CFI professionals (and is the best value in the business).

Rich Stowell Slow Flight Viewpoint!

MCFI (and SAFE Charter Member) Rich Stowell has 34,000 spins in 235 general aviation aircraft. His letter (among others) precipitated action toward modifying the current version of slow flight area of operation in the current ACS.

To: The Airman Certification Standards Working Group

Introduction

The following remarks pertain to requirements in the Private Pilot-Airplane Airman Certification Standards (ACS) regarding maneuvering during slow flight, specifically: PA.VII.A.S2 and PA.VII.A.S3.(1)

For some context, I have been a full time flight instructor since 1987. I am a nine-time Master Instructor, the 2014 National FAA Safety Team Representative of the Year, and the 2006 National Flight Instructor of the Year. I am a recognized subject matter expert on loss of control in general aviation with the following experience:

* 10,000 hours of total flight time

* 9,000 hours of flight instruction given

* 25,000 landings

* 34,000 spins in 235 general aviation aircraft

* 500 single-engine aircraft N-numbers in my logbook

* 380 aviation talks presented

* More than 75 aviation articles and three aviation textbooks published

At issue is wording in the ACS that requires applicants to demonstrate the following levels of skill while maneuvering during slow flight:

“Establish and maintain an airspeed, approximately 5-10 knots above the 1G stall speed, at which the airplane is capable of maintaining controlled flight without activating a stall warning.”

“Accomplish coordinated straight-and-level flight, turns, climbs, and descents with landing gear and flap configurations specified by the evaluator without activating a stall warning.”(2)

ACS Wording Versus Airworthiness Standards

Given FAA airworthiness standards concerning stall warning systems, the simultaneous requirements of “5–10 knots above the 1G stall speed” and “without activating a stall warning” are incompatible. Airworthiness standards in effect in 1993, for example, required the following:

“stall warning must begin at a speed exceeding the stalling speed by a margin of not less than 5 knots, but not more than the greater of 10 knots or 15 percent of the stalling speed…”(3)

Airworthiness standards since 1996, on the other hand, have required stall warning activation to begin “at a speed exceeding the stalling speed by a margin of not less than 5 knots…”(4) This standard does not specify an upper speed limit for activation of stall warning systems. As a result, while stall warning could be activated—indeed, should be activated per airworthiness standards—no less than 5 knots before the reference stall speed, it could activate with a significantly greater margin to the stall speed.

The ACS requirement to fly without activating stall warning clearly conflicts with the simultaneous requirement to establish and maintain an airspeed 5–10 knots above the reference stall speed. Moreover, design parameters that determine when artificial stall warning activates are beyond the control of the applicant—so much so that an applicant may be forced to transition out of slow flight to prevent stall warning from activating, defeating the purpose of this task altogether.

FAA Justification

The incompatibility between the ACS wording and airworthiness standards notwithstanding, the FAA has offered the following justifications:

“The guidance has always intended for there not [emphasis added] to be a stall warning—and that is consistent with slow flight guidance published in AC 120-111.”(5)

“Advocating maneuvering the airplane just below the critical angle of attack with the stall warning activated is neither desirable nor intended.”(6)

These assertions are demonstrably false. For at least several decades now, FAA guidance has been unambiguous about its intent to have stall warning activated while maneuvering during slow flight. For example, in the FAA’s General Aviation Pilot Stall Awareness Training Study conducted in 1975–76 (the FAA Study):

“the student slowed the aircraft to the speed at which the visual or aural stall warning indicator was continually activated [emphasis added]…. Turns were also made at 30° angle of bank with the stall warning indicator continually activated [emphasis added].”(7)

The objective during the FAA Study was for student-participants “to maintain desired heading and altitude at an airspeed and angle of attack which activated the stall warning device [emphasis added], but which did not cause the aircraft to stall.”(8) Two noteworthy results from this study:

“The most effective additional training was slow flight with realistic distractions, which exposed the subjects to situations where they are likely to experience inadvertent stalls.”(9)

“The extra stall and slow flight training was effective in preventing unintentional spins [emphasis added]”(10)

Training in slow flight with stall warning activated coupled with realistic distractions was effective in preventing unintentional spins. Read that again: Slow flight with stall warning activated coupled with realistic distractions was effective in preventing unintentional spins.

The results of this landmark study have driven FAA stall/spin training policy ever since, starting with the introduction of realistic distractions in 1980, followed by the shift from “stall avoidance training” to “stall and spin awareness training” in 1991.(11,12)

Derived from the FAA study, the series of Advisory Circulars (ACs) entitled, Stall and Spin Awareness Training has offered “guidance to flight instructors who provide that training.”(13) The following wording appears in AC 61-67B published in May 1991 through AC 61-67C (Change 2) published in January 2016. All of these ACs recommend the following in Chapter 2, “Stall Avoidance Practice at Slow Airspeeds”:

“(1) Assign a heading and an altitude. Have the student reduce power and slow to an airspeed just above the stall speed…”

“(2) Have the student maintain heading and altitude with the stall warning device activated [emphasis added].”(14,15)

FAA guidance for at least a quarter century has been crystal clear, and for good reason: Training in slow flight with stall warning activated, coupled with realistic distractions, is effective in preventing unintentional spins. “Maneuvering an airplane just below the critical angle of attack with the stall warning activated” not only has been intended, but also is desirable if preventing unintentional spins remains a safety priority with FAA.

Regarding the reference to AC 120-111, slow flight is described therein as “flight just above the stall speed.”(16) This specialized flight training element is intended to expose pilots to “how to maneuver the airplane…without stalling.”(17) The status of the stall warning system during slow flight is not mentioned in this AC. However, the AC does list “manually controlled slow flight” under the heading “Extended Envelope Training.”(18) Revising the long-understood meaning of slow flight as a condition “with the stall warning system activated” now to one “without activation” is incongruous with, and a move away from, the whole concept of “Extended Envelope Training” mandated by CFR §121.423.

In reality, the treatment of slow flight in AC 120-111 is consistent with recommendations made by the International Civil Aviation Organization (ICAO). ICAO describes this specialized training element as follows:

“Slow flight exposes the trainee to flight right above the stall speed of the aeroplane and to manoeuvring [sic] the aeroplane at this speed without stalling. The purpose is to reinforce the basic stall characteristics learned in academics and allow the pilot to obtain handling experience and motion sensations when operating the aeroplane at slow speeds during the entire approach-to-stall regime in various aeroplane attitudes, configurations and bank angles.”(19)

The “approach-to-stall regime” referenced by ICAO is defined as “Flight conditions bordered by stall warning and aerodynamic stall.”(20) Activation of the stall warning system during slow flight is an obvious and integral part of ICAO’s Upset Prevention and Recovery Training (UPRT) framework—the very same framework that informed AC 120-111.(21)

The assertion that no activation of stall warning is somehow “consistent with guidance on slow flight published in AC 120-111” is unsubstantiated at best, disingenuous at worst.

Further Rationalization

The August 2016 issue of DPE Tips offers further justification for the ACS wording: “The FAA does not advocate disregarding a stall warning while maneuvering an airplane.”(22)

It does not follow that having a student learn to maneuver in slow flight with stall warning activated advocates “intentional disregard” for stall warning. I am not aware of any studies that show a correlation between exposure to stall warning and increased inoculation to it. Recall the FAA Study found that training in slow flight with stall warning activated coupled with realistic distractions was effective in preventing unintentional spins.

Consistent with longstanding FAA guidance on stall and spin awareness training, pilots should be taught to integrate sight, sound, and feel while maneuvering in slow flight. They should also be taught to acknowledge stall warning and understand its ramifications. The ability to fly the airplane precisely while stall warning is activated can be a confidence building exercise as well as a way to incorporate angle of attack (AOA) and G-load awareness in real time. While many permutations are possible, following is an example of dialogue that might occur between an instructor (CFI) and student (STU) while practicing slow flight with stall warning activated:

CFI: Do you hear the stall warning?

STU: Yes.

CFI: From now on, I want you at least to verbally acknowledge it every time you hear it.

CFI: We are hearing stall warning in this particular configuration, but when else might we hear it?

STU: At any speed, in any attitude, at any power setting.

CFI: Is mechanical stall warning 100 percent reliable?

STU: No.

CFI: What other indications of reduced margin to the stall might we expect?

STU: Reduced control effectiveness and more pronounced engine effects.

CFI: What conditions could cause you to miss hearing the stall warning?

STU: High workload in the traffic pattern, distractions, stress, lack of proficiency.

CFI: I dropped my pencil, please pick it up for me.

STU: Not now, I’m busy aviating!

CFI: What does stall warning mean?

STU: We are operating at high angle of attack, close to the critical angle.

CFI: With regard to your control inputs, what else does stall warning mean?

STU: Do not pull the elevator control any farther aft.

CFI: Are we in a stall?

STU: No, it’s just stall warning.

CFI: What will happen if you apply additional back elevator pressure now?

STU: We’ll stall the airplane.

CFI: What could happen if we encountered a vertical gust right now?

STU: We could stall the airplane.

CFI: What will happen if we increase the G-load by trying to execute a steep turn now?

STU: We’ll probably stall the airplane.

CFI: What should you do if we encounter the stall?