knowledge test

How to Convert Knots to MPH, and More Unit Magic
using conversion factors to change units and confirm results

The boring way to convert knots to mph is to multiply knots by 1.15.[1] But this skips over some awesome unit magic.

Specifically, we can use conversion factors to change between related units. Let’s look again at how to convert knots to mph.

Suppose you’re traveling at v\ \text{knots}=v\ \frac{\text{nautical miles}}{\text{hour}}. Then,

    \[ v\ \frac{\cancel{\text{nautical miles}}}{\text{hour}} * \frac{1.15\ \text{miles}}{1\ \cancel{\text{nautical miles}}} = v * 1.15\ \frac{\text{miles}}{\text{hour}}} = v * 1.15\ \text{mph} \]

Did You Just Cross Out the Units?

I did! This is called a conversion factor,[2] and is based on the principle that anything multiplied by 1 equals itself. It is an easy way to convert between units, and allows us to solve a variety of aviation problems.

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  1. This is actually more like 1.150779, but we’ll use the rounded version.
  2. More precisely, you may hear this called dimensional analysis or the factor-label method.

How to Convert Knots to MPH, and More Unit Magic
using conversion factors to change units and confirm results
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10 Important Figures on the Instrument Knowledge Test
info about figures that are likely to appear and may be easy points

It turns out there is only a handful of figures on the instrument knowledge test that:

  1. Are likely to be asked about, and
  2. Could be easy points on the test.

These are the 10 figures I believe are worth a closer study.

10 Important Figures on the Instrument Knowledge Test
info about figures that are likely to appear and may be easy points
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How to Pass the Instrument Written Test
an approach to preparing for and taking the knowledge test

Update: The r/flying community strongly recommended using Sheppard Air to prepare for the instrument written test. I can’t personally recommend the software, but wanted to pass on the tip to future readers.


I had only planned to write about the figures in the testing supplement[1], but two experiences on the instrument written test motivated a second post.

  1. I was much more stressed than I expected during the test. This testing strategy helped me avoid (several) silly mistakes.
  2. My approach seemed to work! I only missed two answers (97%) on the final test.

It’s useful to break preparing and testing into three stages.[2]

  1. Months Before ~ Learn the Material
  2. Weeks Before ~ Find and Fill Knowledge Gaps
  3. Night/Day Of ~ Make the Most of Test Day
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  1. You can find that post here.
  2. To keep focused, I used my system for personal task management. I added tasks for each publication chapter and each ground school lesson. Then as the test got closer, I added tasks for taking practice tests and filling knowledge gaps.

How to Pass the Instrument Written Test
an approach to preparing for and taking the knowledge test
Read More »