Plane & Pilot
Tuesday, April 1, 2008

Airplanes, Cars—What’s the Difference?


What you need to know, on the road and in the air


airplanes vs carsWhat’s the difference between car (or motorcycle) engines and aircraft engines? It’s a perennial question with a series of stock answers, none of which is sufficient.
" />


Go, Speed Racer
High-performance driving parallels flying more than you might imagine
By Jeff Berlin

The head-up display in my peripheral vision is reading 127 mph. Wow, I’m really flying. Pilots hearing such a statement might think, “Head-up display? Must be a jet,” and in most cases, they would be right, but not this time. Actually, I’m not in an airplane at all. I’m at the two-day BMW M School performance driving course at the California Motor Speedway, and I’ve got the pedal to the metal in a $100,000 BMW M6, unleashing as many of the 500 horses of its growling V10 as I can. From where I sit, careening down a curvy asphalt ribbon, as I prepare to stand on the brake for all I’m worth to slow for turn one, I’m in a dichotomy of pure luxury and unbridled performance—think autobahn on Sunday afternoon meets Le Mans.

airplanesIndeed, the BMW M6 seems at odds with itself. It’s both civilized daily driver and snarling, Teutonic muscle car—a stealthy wölfe in schaf’s clothing. Not wringing a BMW M car to its limits, not smelling the hot tread of its grabby Continental tires after a few laps on the Speedway’s infield road course and not needing to take an extra lap at merely highway speeds to cool the brakes is like owning and flying an Extra 300L aerobatic plane (coincidentally, also German-made) and never doing a snap roll or hammerhead—definitely verboten on both accounts.

BMW defines performance driving (per-for-mance dri-ving; verb, transitive) as “The act of extracting the highest level of performance from an automobile by its driver under any circumstances,” and on these two days, not only did I learn a helluva lot about controlling a car at the razor-sharp edges of its envelope, but I also learned how similar performance driving and flying really are.

This similarity was readily apparent from before my classmates and I fired up our M6s, M5s and Z4 M Coupes. Once we all signed our lives away on lengthy waivers with lots of fine print and got fitted for our 1950s retro-style helmets to channel Ricky Bobby, we congregated in the Speedway’s driver meeting room for a presentation by Jim Millard, a BMW Performance Center instructor, about the dynamics of high-performance driving, which covered one of the most important issues to any active pilot—decision making. According to Millard, “One of the school’s main focuses is to reinforce good decision making behind the wheel while building confidence and maximizing fun. We want drivers to exercise good judgment while building their awareness of the driver/car relationship and while learning how to comprehend the car’s handling—what the car is telling you.”

Besides exercising proper judgment while careening at breakneck speed from a straight into a switchback, or using similar discretion as an aviator to ensure maximum flight safety, there’s another element at play that directly translates from flying to driving and back again—physics. The kinetic and dynamic forces that act upon a car, especially when taken closer to its limits, are very similar to those experienced by pilots in aircraft.

During his presentation, Millard mentioned that we’ll be exercising these cars in their three axes: vertical, longitudinal and in the transverse, or to pilots, yaw. (Wait, you mean that cars also have three axes? Who knew?) During practice, we’ll each be learning how to better feel the car and understand what it’s telling us. Then we’ll take those individual elements reinforced during drills and string them together on the road course.

Millard then described how a car’s center of gravity directly affects its performance on the track. Center of gravity relates directly to a car’s vertical axis as it accelerates and brakes. BMW M cars are balanced with 50/50 front/rear weight distribution for optimum handling. Using throttle inputs to smoothly manipulate this vertical axis allows the driver to maximize tire traction and transfer weight forward or aft, to the tires that need to do more work at any given moment.

In an aircraft, center of gravity is much more critical, and like a car during acceleration, a rearward center of gravity will facilitate a bit more speed since the horizontal stabilizer will need to create less negative lift.

The car’s longitudinal axis, what we pilots call roll, directly correlates to aviation a bit less, since cars and airplanes effect turns differently, with lateral turning forces affecting each differently.

In the transverse, however, there’s a direct correlation that can be demonstrated in a car by oversteering in a turn, which will cause what most call a fishtail. In an airplane, overshooting the turn from base to final and trying to rudder it around might be a good example of, perhaps, airplane oversteer.

But there are other, more intuitive lessons I also learned during my high-revving weekend at the speedway. One of the most notable is getting into the habit of driving as smoothly as possible. Millard mentioned that the best race car drivers are always the smoothest, and while I’ve no desire to become a race car driver (though I wouldn’t mind enrolling next in BMW’s Advanced M School), our passengers and equipment, car or plane, will all appreciate driving or flying as smoothly as possible. And like in auto racing, smoothness also pays dividends at the highest levels of sport aviation. According to air show star and three-time national aerobatic champion Patty Wagstaff, by smoothly finessing her 350 hp Extra 300S through her air show routine and by keeping the plane coordinated and, in her words, happy, she’ll wring more performance and dissipate less energy than if she were to be too aggressive with control inputs. And because she’s flying in front of millions each air show season, flying her show smoothly also makes it look good to the crowds. “Look at how smoothly Bob Hoover flew,” she mentioned. Indeed.

Another parity between high-performance driving and flying, which Millard and his instructors drilled into our skulls from the get go: Keep your eyes up. How many times have we heard from flight instructors to keep our eyes outside, especially as more and more pilots transition to potentially mesmerizing glass cockpits? Millard taught us this weekend not only to keep our eyes up, but also to look far down the track, to find our turn points as early as possible and to visualize our lines around the track. What a terrific habit to get into when flying, especially in the airport environment. When do I want to turn base or final? Where’s my other traffic? Where do I want to touch down? In the car, where you’re looking is where your hands will take the car. Looking far into a turn or far down the road, even when off the track and on surface roads or the highway, will pay off in increased safety and reaction times.

And speaking of reaction, at the beginning of the school I was a bit hesitant and tentative with control input and really getting on the brake. But after a couple days of track work, decelerating numerous times from 130 to 35 to make my turn and not run off onto the infield got me over any hesitation of applying whatever full control inputs might be necessary to guide the car through the course. The parity here: Many pilots also are loath to apply full control deflection in aircraft.

I had an inkling as I sat in the driver meeting room that first morning that flying and performance driving might bisect at one point or another, but never did I expect them to be as connected as they are. After my stint in BMW’s M School, not only did I become a better driver, but I also became a better pilot. For more, log on to www.bmwusa.com.







1 Comment

Add Comment