As most flight instructors know the FAA recently changed the requirements for slow flight in the private pilot ACS. Slow flight must now be accomplished at a speed higher than MCA or Minimum Controllable Airspeed (a speed at which the stall horn is continuously activated). Why? The FAA feels that when pilots hear a stall horn, they should take immediate stall-recovery action. If slow flight is practiced at MCA, then the stall horn will be heard continuously without the pilot going through the motions of recovering from a stall. The FAA feels that this will desensitize pilots to the stall warning, thus making them less likely to recover from an actual stall should one occur in flight. The FAA, however (and with all due respect), is a little confused about the purpose of a stall warning horn.
The activation of a stall warning horn or light is not an indication of a stall. It’s an indication that the airplane’s wings are approaching their critical angle of attack—the angle of attack that, when reached, results in a stall. In fact, the airplane’s speed at the moment the stall warning activates is at least 5 knots above stall speed, if not more.
FAR Part 23 requires a stall horn/light to activate at a minimum of 5 knots above the airplane’s actual stall speed. In many instances, the warning can activate at a slightly higher speed above the airplane’s actual stall speed (it all depends on the manufacturer of the stall warning unit to say nothing about how normal wear affects the device). When the stall warning activates, the airplane is still flying. Yes, it’s flying on the back side of the power curve, but it’s still flying. You can still turn right, left, descend and even climb in most small airplanes. The controls are mushy, but they still work. Stall warning activation doesn’t imply that your airplane has stalled. Nevertheless, the FAA conflates and confuses the stall warning with an actual stall.
Now, don’t get me wrong here. If a pilot heard the stall horn and wasn’t expecting to hear it, then he’s clearly closer to the critical angle of attack than he thinks he is. In this instance, he should apply standard stall recovery procedures: reduce angle of attack and add power. This is why the stall horn/light is called a stall warning device and not a stall detection device. It warns a pilot of an impending stall should he or she continue to increase the angle of attack (a stall detection device would activate only when the critical angle of attack is reached, and what good would that be to a pilot?).
What if the pilot intends to fly at the airplane’s minimum controllable airspeed? In this instance, the pilot would expect to hear the stall warning. After all, he knows he will be operating very close to the critical angle of attack. Hearing the stall horn when he expects to hear it doesn’t in any way diminish the value of hearing a stall horn when he doesn’t expect to hear it. Expecting something and not expecting it are two distinct psychological states in which a stall warning device serves the pilot. After all, when my kitchen’s smoke alarm goes off when I’m cooking (as I often expect it to) that doesn’t mean I’m less likely to respond appropriately to a smoke alarm when I’m not cooking. Context is very important here. Hearing a stall warning when flying at MCA doesn’t diminish its value in alerting a pilot to an unexpected stall, should one be imminent. (If you want to know the primary reason a pilot might disregard the stall horn/light, then read my License to Learn column in the November 2016 issue of AOPA Pilot titled, When Pilots Stall and Don’t Recover.)
The meaning offered by the stall warning device depends on how a pilot is flying his or her airplane at any given time. To say that a pilot should always apply stall recovery procedures when the stall horn activates is to limit his ability to properly fly his machine. After all, it’s possible that you might hear a stall horn activate in a Cessna 172 (stalls at 50 knots IAS) when descending at minimum sink speed (57 knots IAS). You’ll also hear a stall horn if you want to make a turn (at MCA) in the shortest radius to extricate yourself from a boxed environment. The stall horn will also wail continuously when practicing falling leaf stalls—an essential maneuver for teaching the proper use of rudder in stall recovery. And if you want to learn how an airplane handles during the landing flare—and what student doesn’t?—you’ll need to practice flying slow at MCA.
So how will the FAA’s new slow flight policy affect the development of private pilots? Unfortunately, newly certified private pilots will have little or no experience operating the airplane on the back side of its power curve. Oh wait, you say. Flight instructors can still teach flight at MCA. Maybe so, but wouldn’t that directly contradict the FAA’s original rationale for increasing the speed at which slow flight is performed? Do you actually think that FAA inspectors giving CFI candidates their checkrides are going to look favorably on CFI applicants who slow-fly with the stall horn activated? I don’t think so. The fact is that slow flight at MCA will disappear from aviation’s cultural knowledge base in the same way that the knowledge to perform steep spirals disappeared from the aviation community many years ago when the FAA removed steep spirals from the PTS. The FAA put steep spirals back in the PTS 10 years (+/-) later. When they did, very few instructors knew how to perform, much less teach this maneuver.
This, however, isn’t the really big concern I have with the new slow flight change. The first of two serious issues with this new policy involves the speed at which the FAA recommends that students fly slow. In its recent Slow Flight SAFO, the FAA’s method of determining the allowable speed at which to slow fly will permit the maneuver to be performed at speeds up to 1.34 Vs. Yes, you read that correctly: 34% above stall speed. That’s higher than the approach speed recommended for today’s modern trainer (which is 1.3 Vs). The second serious issue with the new slow flight requirement is how it detracts from learning basic attitude flying skills. The new slow flight requirement forces students to focus on their airspeed indicator to prevent activating the stall horn. When slow flight was practiced at MCA, students primarily focused on managing their angle of attack and flying coordinated by looking outside the airplane. There was no reason to look at the airspeed indicator because the student’s ears were free to assess the proximity to the critical angle of attack. With the FAA’s new slow flight requirement, students are now compelled to spend more time with their eyes directed inside the cockpit focused on their airspeed indicator. Basic attitude flying skills will diminish as a result.
Keep in mind that the FAA and NTSB have pushed hard for the past several years to reduce loss of control accidents (LOC). These types of accidents imply that there was a deficiency in a pilot’s ability to control the airplane. These pilots didn’t suffer from a loss of “decision making ability” or loss of “risk managing ability.” They suffered from a loss of “control,” which involves the flight controls of an airplane. Every bit of evidence available today suggests that pilots primarily lose control of their airplanes because they fail to fly them properly, not because they fail to make a decision properly or manage a risk properly (yes, judgment and risk management play a part, no doubt. But the evidence suggests that these are not majority players in aviation accidents (read the HFACS 2005 studies for evidence of this assertion). So, how does a dumbing-down of basic airmanship skills as a result of the new slow flight requirement help reduce LOC accidents? It doesn’t. And that’s the sad part about the direction the FAA has taken with its new flight training philosophy.
Over the past 15 years, beginning with FITS (FAA Industry Training Standards), the FAA has moved toward an airline-type training philosophy for general aviation pilots. The process continues with the ACS’s new slow flight requirement. As the FAA sees it, if airline pilots are trained to apply stall recovery procedures upon activation of an airliner’s stick shaker, why shouldn’t general aviation pilots do the same the moment the stall horn is heard in the cockpit? If airline pilots don’t make power off approaches, why should general aviation pilots make them? (Power off approaches have almost disappeared from our current training milieu.) If airline pilots do line oriented flight training (LOFT), why shouldn’t private pilots do the same? LOFT is the reason the FAA now recommends that ab initio student pilots learn the basics of flying an airplane during short cross country trips, thus avoiding the practice area. No, I’m not making any of this up. It’s all documented (read my other blogs). What the FAA fails to consider is that general aviation pilots are not airline pilots. Big surprise, right? In fact, there’s nothing about flying bigger airplanes that pertain to flying smaller ones; but everything about flying smaller airplanes pertains to flying bigger ones. Ultimately, the FAA is either unwilling or unable to understand this concept. Once again, I am not anti FAA; I'm anti bad ideas.