Tuesday, 21 November 2017
KEY FLYING LESSONS: PART 4 - WIND
Acknowledgements: AIR FACTS (Richard Collins)
(Ed. Note: Richard offers the benefit of long experience, edited for brevity)
Some things that had to be learned the hard way
You can’t say “been there, done that” until you have actually been there and done that. Then you should be able to add “and learned that”.
In the beginning, there are many unknowns up ahead. We might have theoretical knowledge, or have had a crack at it in a simulator, but when the chips are down only the real thing matters. How well was the challenge met and what lessons were learned?
Most lessons to be learned relate to WEATHER. There are other challenges, but fortunately relatively rare. Engines may quit, systems fail and avionics sizzle or fade, but weather challenges a pilot on far more flights than those other misadventures.
Unfortunately, some pilots rate themselves on weather by thinking, “I made it, so I must have done okay.” Then they give it no further thought. Those who wish to keep on “making it” delve more deeply into it. So, let’s look at some logbook lessons that helped greatly in subsequent encounters with the elements.
There are guidelines to use on wind and most flight schools prescribe wind limits, especially for student solo. I have always read these when they were available, and the way some were written implied that, if you had an instructor along, there was no limitation on wind. There is!
Surface wind forecasts seldom call for gusts of over 35 knots in anything other than a storm situation. The wind that we deal with before and after the passage of a typical front is usually forecast at a maximum of 35 knots and that is not above the practical wind limit of most light airplanes so long as the pilot is proficient at dealing with wind. So, the pilot is usually the limiting factor in high winds, not the airplane.
Most airplane handbooks give a maximum demonstrated cross-wind, which is not a definitive limitation. The real crosswind limitation is based on both the airplane and the proficiency level of the pilot.
· The airplane reaches its limit when there is not enough control authority to manage the cross-wind
· The pilot reaches his limit when he realizes that he isn’t sure of what he is doing!
Landing at Olathe, Kansas, one windy day, the gusts were over 40. The taxiing was a challenge, but still within my personal limit as a pilot; although a couple of times I deemed it wise to let the airplane turn into the wind and wait for a lull.
I encountered what I thought was close to a limit one day in Tulsa, to the east of a strong low and front. Reported gusts were to 48 knots. There was strong wind shear on final, but although taxiing was again a challenge, it was not a problem in terms of my personal limit as a pilot.
We can find wind shear when changing altitude and encountering a different wind at a different level, but it can also occur where the wind is shifting, as in a frontal zone, or flowing into and out of a thunderstorm. Basically, if you have an increasing headwind or decreasing tailwind, the airplane will perform better until it adjusts to the new wind. A decreasing headwind or increasing tailwind will do the opposite. To prepare for it, a pilot needs to note the existing wind before starting down on approach and compare that with the surface wind. The amount and type of wind shear should then become obvious. In my experience, with shear of 20 knots or less, the wind usually starts to adjust at about 500 feet AGL and finishes at about 200 feet.
Wind makes turbulence, and putting a limit on this is related to comfort. If anybody, pilot or passenger, is truly uncomfortable in anything more than light to moderate turbulence, a light airplane can become an unpleasant place to be.
Asheville, NC, is in very rough terrain. I flew there many times and could slip in and out with no problems from downdrafts because I knew from experience where the bumps are and followed a route that minimized them. One day I came upon a dilemma. Given the strength of the gusts in a developing storm system, and the wind direction, and the pouring rain, I simply could not formulate a good arrival plan. In over 50 years that was the only time I diverted because of wind. However, I am aware my experience of Asheville wouldn’t be valid at any other mountainous airport. You have to learn about each the hard way.
The wind lesson? Pick your battles carefully and keep a white flag handy.