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  • Dyfrig Gibbs

Slow Flight

Updated: May 22, 2020

I am missing flying.

Within the syllabus for a Pilots licence is the subject of slow flight. To be able to hang an aircraft in the air with minimal power is a skill not easily gained but essential, both in terms of safety and in developing a pilots handling. To be able to go slow is an art, in life as in the air.

During my PPL training it was, without doubt, the skill that took me longest to get to grips with. So much of learning to fly feels fast: you become accustomed to doing things accurately, safely and at a brisk pace. Flight - or more specifically lift - is a function of a surfaces inherent lifting ability, it’s size, the density of the air surrounding it and the speed of that air over it. On a given day, at a fixed altitude in our atmosphere, in an aircraft of fixed clean wing design (meaning a wing can‘t increase in size without increasing drag), a pilots only means of increasing the lift produced by that wing is to go faster through the air. So airspeed keeps us aloft and for that reason we, under normal circumstances, operate in a range where there is a safe and healthy margin between flying and falling. To pull a wing through the air you require thrust, to pull it through the air faster you require more thrust, which requires more engine power. What if your engine can’t give you any more power? Ok this is a reality of all power plants but what if your engine is somehow limited way below its normal limits, its damaged, restricted, some catastrophe has limited the normal amount of work it can do?

With flight it is not perfect or linear nor proportional to say more power equals more airspeed which equals more lifting ability. As we fly faster we create more drag which acts against thrust which limits our speed increase and lifting ability. But there is a point on this complex graph of the forces that oppose forward movement that sits, like a ball in a bowl, at the very bottom of the curve. It represents the velocity of minimum drag (Vmd) and thus the point at which you need least power to equal the force of gravity pulling you back to earth.

Pilots learn flight in light aircraft with one piston engine that normally relies on four cylinders and 8 spark plugs. Imagine we didn’t have all of those operating and were over rough terrain or suspected a low fuel situation and wanted to conserve it. Two possibilities off the top of my head that would warrant configuring the plane to hang in the air safely and continue its journey without succumbing to terra firma.

During training I found the pursuit of this balance a frustrating one: going slow but not slow enough, still too much power, take the power off, hold the altitude, too slow, sinking, need too much power to recover it. Like pouring from one cup to another trying to get them perfectly equal: back and forth I would pour. Back and forth I would fly, my instructor antsy next to me and my own tensions rising, which in turn betrayed any kind of deftness I may once of claimed. It is an art I’m learning.

Balance is and has always been high on my agenda: I preached for two and a half years to new BGS students about navigating flight training and maintaining a life balance so that when a goal is reached their world is still recognisable. The last three years for us as a family has been immeasurably and equally fun and stressful at the same time. It feels like we’ve balanced spinning plates brimmed with emotion and chaos in quantities we couldn’t of imagined possible and yet, as I write, my world are all sleeping peacefully close by (its just the world outside our door that’s unrecognisable). Striving for balance feels noble and worthy of effort.

In the A320 flying at Vmd (the speed at which the ratio of lift and drag is at its best) is much easier to achieve. We call it green dot speed, simply because there is a green dot that represents the current computation of vmd on our speedo. If you want to fly at that speed you just dial the speed down to sit on the green dot. We do it often in normal (and non normal) operations. It’s easier to do in an Airbus, but in many ways still has the same feeling, sense and quality.

After I gained my PPL and was hour building it became my favourite past time on a solitary summer afternoon in the air. If time was on my side or I was just flying with skill improvement as my goal, I would fly up to 2-3000 ft, slowly ease the throttle back to achieve around 1900 rpm, enjoy the quietening of the engine and hold my distance from the earth. Gently trimming the aircraft more and more nose up, increasing the angle of my wing in the wind and bending air further around it, pushing Bernoulli’s theory and the travel of the elevator to the absolute limit. Watching the rpm drop as the airspeed did too, eying the altimeter and vertical speed indicator and holding them still with a feather adjustment on the throttle. Like Cheech I would ride the air sitting low in my craft with it’s nose high in the air, hearing the low murmur of the lycoming engine outside and the tune low rider in my head, I would cruise the blue sky held aloft, as if by a thread, from the lush green below. The sense of hanging on thin air like a leaf that won’t fall so striking, so satisfying and so similar in feel to my early dreams of flight.

It is these moments in the air that I’m missing as we adjust to our slow way of life, locked down In Mallorca. Yes, we now live in Mallorca and I’m an A320 pilot. Clearly a lot of air has flowed over our wings since the last time I wrote. I‘ve missed it too and am loving having the time and capacity to think about writing and living a balanced life... could just do with adding a pinch of work.

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