Friday, April 1, 2011
Beyond the POH
If you’re like those of us with a passion for defying gravity by bullying the air we breathe with fantastically mechanical contraptions, you probably look at every flying machine with a scrutinizing eye. You admire or dislike its lines and sometimes wonder why things were designed the way they were. Maybe during your preflight you’ve noticed an aerodynamic “widget” on the surface of your aircraft, or even noticed certain naughty or nice behavior in flight, and were curious as to its reason. Well chances are good that what you’ve noticed has already had the attention of engineers and test pilots, and might in fact even be the result of their best efforts to bring you a safer, better-performing aircraft to suit your needs.
Machines that fly are complex integrations of aerodynamic, propulsive, and electronic systems. When interfaced with humans—incredibly versatile systems unto themselves—they become tools capable of accomplishing an ever-widening variety of tasks. The design and flight testing of such a machine involves validating large amounts of mathematical data and theory from aeronautical, mechanical, structural, and electrical engineering disciplines, as well as understanding the tremendous abilities of the human crew, their finite limits, and even their psychology as it all relates to human workload. Achieving this results in a machine that displays an optimum balance of desired performance, stability, and control.
If you have in fact ever been interested in any of the above disciplines, but are preparing to turn the page before the equations start, you can relax. I happen to know that nothing clears a room faster than adding mathematical equations to a conversation (just ask my coworkers). Still, there remains an endless amount of fascinating and relative material to talk about. One of the key duties of a test pilot is to be a good liaison between those who design, those who fly, and even those who buy an aircraft. He or she must be able to speak a little of each language in order for any aircraft program to be born, to evolve, and become a success.
I’m hoping to use this valuable space to discuss some of the more technical elements of our beloved flying machines in a user-friendly, non-room-clearing-sort-of way, typically focusing on the relevance to the people who wiggle the stick of the end product. Many of us have put in countless hours developing the skill to fly these aircraft to the best of our ability and within the limitations defined in the Pilot’s Operating Handbook (POH). Sometimes the road to developing an aircraft’s abilities and attributes, and getting it to play nice with people, can be quite interesting, to say the least. As I’ve tried to grasp the engineering behind much of it over the years, I think about the amount of insight, intelligence, trial and error it took to develop the aircraft we fly today.
Starting with the invention of the flapping hinge to compensate for the dissymmetry of lift making early rotary wing flight possible, we have progressed to present day, where we’ve developed better aerodynamics along with modern flight control systems, giving us the ability to fly a precision approach to a point in space. Any helicopter pilot will tell you this is almost akin to developing a way to thread a needle with a runaway fire hose. Developments such as these are why I love flight test so much—it takes engineering theories out of the notebook, puts them to the test in the real world, examines how the human element affects things, and continually tries to improve upon integrating it all. This sets the stage for a lifetime of learning.
Using all the professional resources and personal experience that I can conjure up, along with the infinite wisdom and help of my elders in the flight test world, I’m hoping that in coming issues, we can all glean just a little more insight into what ultimately brings us the POH for the many flying machines we use to fuel our passion-turned-profession, and maybe, at the same time, glean a little more insight into ourselves.
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