It could. The issue would hinge on Practical Test Standards (PTS) Area of Operation I, Task F (performance and limitations). Element 4 asks for applicants to describe the effects of atmospheric conditions on airplane performance. Since the Pilot's Handbook of Aeronautical Knowledge on page 2-1 discusses the atmosphere as consisting of 78 percent nitrogen, 21 percent oxygen, and the remaining approximately 1 percent being trace gasses, a simple conversational statement could reveal to an examiner a weakness in basic aerodynamic knowledge.
Only the rarest designated pilot examiner (DPE) would pursue such a weakness based on a simple conversation, because too many Notices of Disapproval hurt a DPE's business. Still, any flight or ground instructor who strives to produce a well-rounded, knowledgeable pilot would certainly be interested in avoiding such chinks in the aeronautical knowledge armor in any case.
Often, when pilot candidates and their flight instructors discuss requirements set forth in the private pilot PTS, they mistakenly believe that there is little or no requirement that aerodynamics become a part of the potential testing. This is understandable when one does not find a task titled Aerodynamics. In fact, aerodynamics partially reside in Task F, Performance and Limitations. Element one calls for you to exhibit knowledge of the elements related to performance and limitations by explaining the use of charts, tables, and data to determine performance and the adverse effects of exceeding limitations.
Most flight instructors and students, reading Task F, quip that it only requires using charts, tables, and data. However, when element 1 touches element 4 in describing the effects of atmospheric conditions on the airplane's performance, there are potential openings to discuss aerodynamics at length.
An example might be a discussion of the standard altimeter setting of 29.92 inches of mercury. Air density has significant effects on airplane performance, as air that thins with altitude (or temperature) reduces power, thrust, and lift. Should your DPE ask why these three performance elements decrease with altitude, can you explain that engines take in less air at altitude, thus power diminishes? Do you understand that thrust and lift at high altitudes or temperatures wane because propellers and wings have fewer molecules of air to provide a dynamic reaction? Chapter 2 of the Pilot's Handbook of Aeronautical Knowledge walks you through these issues.
An atmospheric condition that certainly affects airplane performance is humidity. A pilot examiner who cares more for fulfilling his public duty than ensuring repeat business might ask why increased humidity decreases airplane performance. At a private pilot level, understanding that water vapor is lighter than air, so moist air is lighter than dry air, should be sufficient. The question probably will not appear. But it might.
American culture creates disadvantages for fledgling pilots because of lackadaisical use of terminology. Highly technical venues demand precise terminology for thought-pattern clarity. Examiners find examples easily. By the time of their checkrides a notable percentage of private pilot applicants still have difficulty relating to air as a fluid (as outlined on page 2-4 of the Pilot's Handbook of Aeronautical Knowledge) when discussing lift. Socially, fluid means liquid; this mindset disrupts learning about or explaining lift. Without a rounded knowledge, understanding the effects of Bernoulli's principles becomes improbable, thus inexplicable.
Without understanding this not-so-fine point, any aviator studying and ruminating on these texts can fall short when trying to understand basic aerodynamics. Your DPE might explore your understanding of basic aerodynamics by simply asking about the relationship between relative wind and angle of attack. Since this has a direct connection to stalls (Area of Operation VIII) and to charts, tables, and data, it is fair game.
Regarding "why"-style questions and stalls, pilot examiners might consider asking why an airplane can be stalled at any attitude or any airspeed. Referenced in the PTS, the Airplane Flying Handbook goes into good detail on page 4-6. Clearly, the importance of this to charts, tables, and data should be beyond question. Even clearer should be the validity of this question to safety. The tie-in to Area of Operation VIII, Tasks B and C, power-off and power-on stalls, becomes complete through element 1 of each. These demand knowledge of the elements related to each of these stalls, and since recognition is a key component of each, you should expect examiners to ask about the differences between aerodynamic power-off and power-on stall indications.
Since DPEs are authorized to combine elements of tasks that meet the objectives of more than one task, simple questions regarding basic aerodynamic forces also apply to Area of Operation IX: Basic Instrument Maneuvers. An airplane neither knows nor cares if a pilot is operating by instrument or visual reference, so long as that pilot makes proper use of the four forces of thrust, drag, weight, and lift. These are so elemental to flight that aviation's training industry assumes that all pilots understand them, thus we minimize training and testing regarding them. Chapter 3 in the Pilot's Handbook of Aeronautical Knowledge has it all there for you.
Any discussion of emergency approaches and landings, meeting Area of Operation X, Task A's intent, certainly lends itself to your knowledge of the concept of a best glide speed. A key to the FAA's intent of testing is always element 1, which consistently asks applicants to exhibit knowledge of the elements related to the task at hand. Drag is a primary concern during an emergency approach and landing, and aerodynamics texts take pains to differentiate the properties of induced drag from those of parasite drag. They do so for a reason. Arriving at the selected emergency landing field, pilots confront ground effect, which makes a statement in the Pilot's Handbook of Aeronautical Knowledge a tolling indictment of the aviation training industry, including us pilot examiners.
Page 3-7 notes that "This is the result of a phenomenon that is better known than understood even by some experienced pilots." This statement underscores that as an industry, we instructors and examiners have not provided the excellence that our students and passengers deserve. As you prepare for your checkride, so do you.
Dave Wilkerson is a designated pilot examiner, writer/photographer, and historian. He has been a certificated flight instructor since 1981 with approximately 2,000 hours of dual instruction, and is a single- and multiengine commercial-rated pilot.
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