The ACS Focus Team has been asked many questions about the topic of slow flight. We have assembled a list of the questions with background and guidance on the issues for ASIs and DPEs. We have also included responses to a few other questions that DPE’s may have.
Maneuvering during slow flight is to be 5-10 knots above stall speed without activating the stall warning horn (I assume stall warning light, if appropriate). Stall warning horns are designed to provide an audible sound at 5-10 knots above stall speed. Is the goal to fly 5-10 knots faster than when the warning horn sounds, to avoid possibly hearing it? If 5-10 knots above actual stall speed, then is the warning horn chirping on and off acceptable?
AOO VII Task A
If the pilot recognizes the stall warning and promptly makes an appropriate correction or airspeed adjustment, a momentary activation of the stall warning horn does not constitute unsatisfactory performance on the maneuver. As with other standards, the problem would arise from continual deviation from the standard, lack of correction, and/or lack of acknowledgment. The goal is to ensure that the applicant does not perform the maneuver with the stall warning activated.
The certification standard in 23.207 states for airplane certification testing, the stall warning must “begin at a speed exceeding the stalling speed by a margin of not less than 5 knots and must continue until the stall occurs.” This is the primary reason the suggested range above stall speed has moved from “3-5 knots” to “5-10 knots without stall warning activation.” The certification standard for the stall warning does play a role in the airspeed selection for the maneuver, and stall warning activation will vary from one airplane to the next, so it is important for the applicant to select an airspeed where the stall warning should not activate except on a momentary basis (e.g., due to turbulence).
The PTS standard for maneuvering during slow flight was for the applicant to establish and maintain “an airspeed at which any further increase in angle of attack, increase in load factor, or reduction in power, would result in an immediate stall.”
The current version of the Airplane Flying Handbook says slow flight should be performed at “the slowest airspeed at which the airplane is capable of maintaining controlled flight without indications of a stall—usually 3 to 5 knots above stalling speed.” The guidance has always intended for there not to be a stall warning, and that is consistent with slow flight guidance published in AC 120-111. However, the 3-5 knot range given does not pair well with the part 23 requirement for a stall warning (§23.207). It is not practical to maneuver in that airspeed range and not have the stall warning, which is an indication of a stall. The standard in the PTS also implies being right above the critical AOA, which means the stall warning would be activated. This result does not align with the guidance, or with what the FAA advocates. Specifically, the FAA does not advocate intentional disregard for a stall warning while maneuvering.
The purpose of teaching slow flight is to ensure that the pilot understands how the airplane responds with less airflow over the flight control surfaces. Since airplanes are operated at low airspeeds and high angles of attack during the takeoff/departure and approach/landing phases of flight, it is essential for pilots to learn the airplane cues and how to operate the airplane in this state. Regardless of airplane type, a pilot does not need to be just below the critical AOA to experience the desired characteristics and achieve the slow flight objectives. These objectives can be accomplished without deliberately activating the stall warning through flight just below the critical AOA. We want to influence the behavior and practices the pilot will follow outside the training environment. Therefore, with the exception of performing a full stall maneuver, a pilot should always perform the stall recovery procedure when the stall warning is activated.
With respect to guidance, the change to AC 61-67 published just prior to the final decision on the AFH wording change, which drove the FAA’s decision to modify this ACS Task element. We are working on another change to ensure the AC will align with the AFH and the ACS and be consistent with AC 120-111.
To further explain these changes, we intend to publish a SAFO that is now in formal coordination.
Private Pilot – Airplane FAA-S-ACS-6
If an applicant fails to provide a passenger briefing, a pre-taxi briefing or a pre-take off briefing, should I be issuing a Notice of Disapproval?
Both the PTS and the ACS require the applicant to brief on certain Tasks. The ACS includes more specific briefing requirements in the Preflight Procedures Task (PA.II.B), and PA.II.B.K3 is consistent with the requirements of 14 CFR 91.107(a)(1). An evaluator need not issue a Notice of Disapproval if the applicant does not offer specifically-named “passenger,” “pre-taxi,” and “pre-takeoff” briefings, but an applicant’s failure to provide any kind of briefing to passengers in the Preflight Procedures AOO, especially with respect to the regulatory requirement to brief passengers on use of safety belts and harnesses, may warrant a Notice of Disapproval.
As applicants and their instructors begin to use the ACS exclusively in preparation for the practical test, we would expect to see more consistent and more specific performance with respect to briefings in the Preflight Procedures AOO.
Is there a measurement by which I should measure the quality of the briefing?
It would be impossible and impractical to create a “standard” for an acceptable briefing. Just as was in the case with the PTS, the FAA expects evaluators to use sound judgment in evaluating the applicant’s performance during the practical test.
If the applicant fails to accomplish a brake check after engine start, assuming the brakes have held the aircraft in position after the engine start, am I to issue a Notice of Disapproval? If the manufacturer did not list a brake check in the checklist prior to taxi (such as CE170), does the ACS override the manufacturer requirements?
AOO II Task D
If the manufacturer does not list brake check after engine start as a checklist item and, in the case of the scenario presented, the brakes have been held up to the point of taxi without fail, it would not be necessary or appropriate to issue a Notice of Disapproval. Holding the brakes during engine start could also be construed as “checking the brakes.” The intent of this Task element is not as absolute as the current phrasing implies, so we will consider modifying the wording to something like “perform a brake check” in the first ACS revision.
Instrument Rating – Airplane FAA-S-ACS-8
Should the instrument applicant provide a passenger briefing? IR.II.C.S5 might lead one to believe this should be a pre-taxi briefing. Should there be a pre-takeoff briefing? Should there be a risk analyses presented? These would be consistent with the Private Pilot ACS.
There is no intent to require a briefing, but the evaluator may want to ask how the pilot plans to taxi to the runway to better understand the pilot’s planning and thinking. We expect to revise the wording of this element in the first revision for greater clarity (e.g., “preplan aircraft movement to avoid runway incursions”).
If you have any further question about the ACS, please direct your question to the ACS focus group. If you have not already done so, please visit, and consider subscribing to, the Airman Testing page on the FAA website. If you have questions about the ACS that are not addressed in the ACS FAQs or other published material, please direct them to the ACS Focus Team at: [email protected].