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Southport, Manitoba, Canada
Steve Pomroy is a professional flight instructor and aviation writer. He has been teaching since 1995 and holds an Airline Transport Pilot License, Class 1 Instructor and Aerobatic Instructor Ratings, military QFI, and an undergraduate degree in Mechanical Engineering. He's written and published three flight training books through his company, SkyWriters Publishing, and has several other books under development. Steve currently teaches RCAF pilot candidates on their Primary Flight Training course.

Monday, January 14, 2013

Slots and Slats

In learning to teach, a set of principles that's useful is the Laws of Learning, originally developed by Edward Thorndike and then developed further by subsequent researchers. The laws of learning consist of eight1 laws that help us describe what makes people learn more effectively.

Primacy is one of these laws. Quoting from Wikipedia:
"Primacy, the state of being first, often creates a strong, almost unshakable, impression. Things learned first create a strong impression in the mind that is difficult to erase."
Bottom line: Teach it right the first time! This is a mantra that new flight instructors are drilled with. Unteaching/unlearning incorrectly-learned material is very difficult and inefficient.

What does all of this have to do with slots and slats? Well, I don't know what they are. Or, more correctly, I know what they are, but they are similar devices—one fixed in place and one extendable/retractable—and I don't know which is which. This is despite the facts that I've known of their existence and function for well over 20 years, and I've discussed my not-knowing with flight instructor candidates dozens of times—each time being reminded by my students of which is which, but it just doesn't stick.

Why not? PRIMACY! I was first exposed to the function and structure of slots and slats on an Air Cadet course in CFB Borden. The instructor was very knowledgeable and capable, but he had a very strong french accent. So when we got to the material about "slots and slats", he proceeded to teach us all about "sluts and sluts". At least that's what we teenagers heard through the accent...

A "slut" is a permanent opening in the leading edge of a wing that allows airflow to be redirected at high angle of attack, resulting in a higher maximum lift coefficient and lower stalling speed. A "slut", on the other hand, is an opening near the leading edge of the wing which closes at low angle of attack (high speed) but opens at high angle of attack (low speed), resulting in a higher maximum lift coefficient and lower stalling speed.

Do you see the confusion?

So, to you instructors out there, TEACH IT RIGHT THE FIRST TIME! And to you students, LEARN IT RIGHT THE FIRST TIME! In both cases, this is sometimes easier said than done, but it's well worth the effort.


1 – This number actually varies depending on what reference you look at. The FAA's Aviation Instructor's Handbook says there are six laws. Transport Canada's Flight Instructor Guide says there are seven, including Relationship, which I've never seen anywhere else (and which seems to be redundant, but that's another post).

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