Smoke On Go

The science and art of decision-making in aviation

Piloting an aircraft effectively and efficiently involves two processes. The first is handling − the physical aspect of flying involving the manipulation of the controls. The second is the cognitive part of flying. To be a safe and reliable pilot, it’s essential to master both. In this article, I’m going to discuss how these processes affect decision-making in the air.

What influences our decisions?

The decision-making process in any context is complex. This is because the decisions we make are the result of many variables − some subtle and unconscious, others more easily defined. These can include, for example, your objective, how you interpret your current situation and how you believe things will evolve. On the other hand, other decisions are a consequence of subjective and intangible factors such as your background, what you’ve been exposed to, your values, etc.

All these variables come into play when a pilot must make a judgment call.  Sometimes they make a good one and sadly, sometimes they don’t. The complexity of the process often makes it very difficult to figure out why certain decisions were made by one pilot when another would have made completely different choices. Most pilots don’t set out to hurt themselves or others, but it happens because not all decisions made in the cockpit are clear cut, they often require fine judgment.

I think of decision-making in aviation as balancing two opposing worlds: art and science.

The difference between art and science in aviation

The science concerns discernable, objective facts − the irrefutable theory, while the art involves the intuitive subjective “feel” required to practically apply science in a real-life context. Both are important.

One can, for example, understand the theory of landing a plane without ever getting airborne. However, without practical experience, it’s going to be difficult to ever land a plane safely. Conversely, a pilot is able − through practical experience alone − to land without ever knowing the theory, but why ignore the theory, which obviously helps tremendously. Additionally, there are those times when one ought never to rely on intuitive ‘feel’ offactorssuch as fuel or weight and balance calculations.

Let me illustrate the difference between art and science in aviation with the example of a stock-standard take-off in a light aircraft. The science is relatively easy to understand. Take-off performance for any plane can be accurately calculated by taking into account factors such as weight, wing configuration, runway surface, climatic conditions, etc. Based on these variables, an accurate rotate speed can be calculated and safely applied. It’s irrefutable science!

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But what about an old bush pilot taildragger technique of applying full power against the brakes and then, by pure feel and cadence, literally hauling the aircraft off the runway after a very short run with the application of full (manual) flap in one smooth ‘rotate and extend’ motion. This results in the plane lifting off and climbing out at close to zero indicated airspeed.

No doubt there is science behind this ill-advised bush take-off technique, but it’s another example of where it’s simpler to demonstrate then to explain.

Please don’t try this. If you don’t have the ‘feel’ you are likely to stall and bust an undercarriage. Besides, if you are at a short field that requires this technique for take-off, then clearly you’ve already made a bunch of bad decisions so please stop before someone gets hurt.

My very strong advice is: if you don’t understand the science of something, don’t ever do it. But don’t rely purely on the science. You must also develop your intuition; you can’t simply be a robot when flying − not even in computerised airliners.

The value of rules of thumb

This is why I love rules of thumb in aviation, and rely on them extensively. Rules of thumb are often not 100% accurate, and could be refuted in a purely scientific theoretical context, but they are sufficiently accurate to practically guide pilots in real-life flight operations. For me they are an effective fusion of art and science.

Here are just a few rules of thumb that I’ve collected and used over the years. Some I figured out through my own experience, and I got others from books.  I picked up most of them from wiser and more experienced pilots. My personal list of rules of thumb list keeps growing.

Here are some useful rules of thumb for the takeoff and landing. Please note that these are for light GA aircraft, I cannot attest for their application for heavier aircraft.

Rules of thumb for takeoff

  • Rotation speed is equal to 1.15 stall speed.
  • Takeoff distance increases by 15% for every 1 000-foot increase in density altitude, or even more simply: a 1% increase in temperature above ISA will increase takeoff ground roll by 10%.
  • A headwind of 10% of takeoff speed reduces takeoff distance by 20%. A tailwind does the opposite.
  • A 10% change in weight will increase takeoff distance by 20%.
  • A soft field and long grass can increase takeoff distance by up to 50%.
  • If all the above is too much to comprehend or apply, then rely on this all-encompassing rule for takeoffs.
  • To safely continue a takeoff roll, one ought to reach 70% of required flying speed at the runway’s halfway mark. If you can’t achieve this then abort while you still have space to stop.

Here are a few rules of thumb for landing

  • A tailwind of 10% of your approach speed will increase landing distance by 20%. Similarly, a 10% change in approach airspeed will increase ground run by 20%.
  • Use the same indicated approach speed for high- or low-density airfields. There is no need to add knots to the approach of a hot and high airfield. Many people do and it is unnecessary and can be dangerous!
  • A narrow runway gives the impression of being too high on approach, and a wide runway does the opposite. Get used to relying on other height references on final.
  • Indicated stall speed x1.3 is a good over-the-fence speed.
  • Every knot faster than this x1.3 over the fence speed will cost you 100 feet before you can safely stop.
  • If all of the above is too complex to apply, then simply remember this for landings: If you won’t touch down in the first third of the runway, then go around.

Personal, unbreakable rules

In addition to my rules of thumb, I have a collection of personal rules that I have developed over the years. For example, if I ever do three silly things in short succession before flying, such as locking my headsets in the car, or rechecking something I’ve already checked during my pre-flight check. then I will seriously consider not flying that day. These missteps tell me I am clearly fatigued.

Science has shown that the first human faculty to be affected by fatigue is judgment, and the frightening thing is that the tired person may not realise this. Personal rules like mine can serve as your guide and protector. Please take the time to think about and formulate your own, and have the discipline to adhere to them no matter what.

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