On the Back of the Drag Curve

Posted on May 31, 2013

On the Back of the Drag Curve

Up in the mountains. Colorado. Summer. High and hot.

I was doing my Con-Air Air Taxi thing. Cessna Turbo 210. Retractable, fast, three bladed constant speed prop. Serious tool. Sheriff’s Office. Picking up two prisoners. Along with the Corrections Officer flying along, that made four of us returning to the narrow air strip. I had landed there that morning, when it was cooler, and noted the altitude (6,000 feet plus) and the probable density altitude that would pertain a few hours later.
I was hoping to get out promptly, before the full heat of the day.
In the event, it was not to be. By the time we had stood waiting, in the crowded prison central hall, for hours, with prisoners being marched every which way, and by the time our prisoner pick up had been processed, stamped, signed in, signed out, looked at, examined… it was past midday.
And hot… I had some three thousand five hundred plus fixed wing flight hours, plus plenty of high altitude experience, to immediately recognize the Ugly in what I was facing. I pulled out the Flight Manual, and ran some serious numbers. My density altitude was about eleven thousand feet. I had enough runway, with my cautiously reduced fuel load. Plus I had about eight to ten knots blowing straight down the rough surface. The only windsock I could see was located close to one end. It seemed to occasionally go limp, and then fill up again. Strange. I ran the take off numbers allowing for zero headwind. Then I factored in the rough surface. It still came out as feasible, albeit with less margin for error than I was used to. A little voice in my mind was expressing unhappiness. I know that voice. I don’t like him. He makes me nervous. I re-ran the numbers again, while the three waiting passengers stared at me dully. It was scorching, uncomfortable, and we had no shade. They wanted to get going. Anything was better than just standing there. The two prisoners, with their heavy chains and leg irons, looked miserable. It can’t be much fun being herded around like dumb cattle. Do this. Do that. Sit here. Shut up. Yes, Sir. No, Sir.

I remember running the numbers multiple times. It should have told me something. I obviously wasn’t over happy. Some nagging doubt was prodding at my mind.
Francis… are you sure you know what you’re doing?
We taxied out. I made sure to go all the way to the end. I was going to use more runway than I normally did. I didn’t want to waste an inch. In the distance, I could see the windsock, inflated again with a precious eight to ten knots of breeze. Straight down the runway. Good. I wound up the RPM with brakes set. Only when she was hollering at full take-off horsepower, did I start the actual take off roll.
Faster we went. Faster. Nose wheel coming up. Main wheels feel light. Good. Feels… good.
To abort a take-off at the penultimate moment, a pilot may only have a split second window. A Decision Time that comes… and is gone. Forever. I remember we were committed, over the end of the runway, trying to claw our way into the air. And I knew… it wasn’t good. At the same moment as I seemed to start a slight sink, at the same moment that I realized I wasn’t climbing, at the same moment I was unhappy about my air speed, at the same moment as my mouth went dry, I saw…
Out of the corner of my eye…
The windsock. Fully inflated. Pointing. Like an accusing finger. Coldly. In the exact direction of my lumbering take-off. Oh, hell…
Tail-wind. One-eighty degree Wind Reversal.
And all of a sudden, the penny dropped. We were in a narrow valley, and the air strip was located not far below the pass. The col, if you like. It happens. That was why the windsock appeared to go limp, and then inflate again. The wind direction was unstable. And now…
At the worst possible moment, it had flipped on me. Now I had a totally unexpected tail wind. With take-off flaps selected, gear down, and going way, way slower than I would have liked. And I HAD to climb. I was just horribly way too close to the back of the drag curve. That region of airspeed, where drag is such, that acceleration and climb is almost impossible. Unless you reduce drag, by reducing your angle of attack. But you can’t reduce your angle of attack. Not when you are barely shushing ten to fifteen feet above large boulders. The same ones you thought you would be clearing by a hundred and fifty feet.
Now I knew I was in trouble. Big trouble. At the back of my mind, I saw us crashing. The attempted turn. The stall/spin. The impact. The violent explosion. The flaming wreckage. The accident inquiry. The full attribution of blame to the Pilot in Command. Taking off at a weight in excess of what was prudent…
It was a tense, fearful, cockpit. I said nothing. I was flying to the absolute best of my limited abilities. It’s kind of a desperate balancing act. A very delicate balancing act. Keeping the machine in the air. Not turning. Trying to accelerate. Listening to the intermittent, plaintive wail coming from the stall warning horn. It would come on… Go off…. Come back on again. Teeth clenched, concentrating furiously, forcing myself to fly, fly, like I had never flown before.

Slowly, slowly, we accelerated. It wasn’t until a full minute had gone by, that I remembered to breath. Climbing up into the sky never felt better, like a sweet wine after a forty day water only fast.
Of all the events in my flying I look back on, where I was simply way too close to the Edge, this is one such.
I learned from it. I was to become a better, more cautious pilot.

Up in the mountains. Colorado. Summer. High and hot.
And the day I tasted fear.

Raw. Fear.

Francis Meyrick

Last edited by Francis Meyrick on May 31, 2013, 1:48 pm

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