Plane & Pilot
Tuesday, July 29, 2014

20 Things You Never Knew About Your Airplane (Or Someone Else’s)


A few little known thoughts. Ever heard of the Cessna 620? Why T-tails? A Seneca Tri-Motor?



Questair Venture
11 Pretty much everyone has heard about the Ford Tri-Motor and the Junkers JU-87 Tri-Motor (in fact, there were nearly 200 tri-motor models produced prior to World War II), but did you know there was also a Piper Seneca Tri-Motor? When Piper was toying with the very first prototype of the Seneca in the 1960s, they tried mounting a pair of 180 hp engines on the wings of a standard Cherokee Six 300, but left the 300 hp Lycoming in place on the nose. Climb performance with 660 hp was spectacular, but no one could figure how to put enough fuel aboard to give the airplane more than a 400 nm range, so Piper killed the three-engine idea.

12 Okay, just to one-up a tri-motor, did you know that Cessna designed and built a prototype for a pressurized four-engine business aircraft in the mid-'50s? The Cessna 620 (310 times 2, get it?) mounted four-geared, 350 hp Continentals on the wings and was planned to be configured for up to 10 passengers. Cessna conceived the design in 1952 and made the first flight four years later, but the timing was wrong. Coincidentally, Cessna also was working on the USAF T-37 jet trainer at the same time, a guaranteed government contract, whereas the 620 had to be funded by Cessna alone. Jets were just coming into service with the airlines, and there was a glut of Martin 404s and Convair 240/340s coming onto the market at low used prices. These carried more passengers and cruised faster. The 620 was abruptly canceled in 1957.

13 What's the only American general aviation production retractable to fold up the wheels outboard, Me-109 style? Answer: the Beech Sierra. Introduced in 1970 as a step-up retractable version of the top Musketeer in Beechcraft's three musketeers, the A24R featured an unusual outward-folding landing gear that tucked away into the outer rather than the inner wing. This was (and remains) unusual in that many wings decrease their thickness past quarter span and are less likely to maintain enough room to store the wheels, whereas folding the gear inboard allows the tires and mechanism to hide in the thickest part of the airfoil. The Sierra was advertised as being a six-seater, but its numbers suggest it was more of a 4+2. You could buy the Sierra with up to three doors, including an aft compartment opening. The airplane flew behind a 200 hp Lycoming with a constant speed prop out front, so it qualified as a complex aircraft. It used Mooney-style rubber doughnuts for shock suspension and stored fuel in the leading edge of the wings. Beech produced the last Sierra C24R in 1983.


Cirrus Side Stick
14 Years ago, a talented engineer named Jim Griswold designed a slick little homebuilt called the Questair Venture. It was an unusual, semi-egg-shaped airplane and great fun to fly. Griswold's earlier credential was that he led the design team on the sensationally successful Piper Malibu. The Venture used side sticks for roll and pitch control, fitted with a breakout force that automatically returned the sticks to neutral if you maneuvered and then simply released pressure. A few years later, Dale and Alan Klapmeier hired Griswold to design the control system on the Cirrus SR20 and subsequent SR22, again employing the breakout force. The great joy of side sticks is that they free up the space directly in front of pilot and copilot, and make entry and egress notably easier. Similarly, if you happen to have the right body geometry, you might be able to fly with the flick of a wrist (though in the real world, that rarely works). The downside is that 90% of the world's population is right handed, and that means pilots must fly with the left hand. He/she could conceivably fly from the right seat with hands on the proper controls, but most instrumentation is left-biased, and that would make IFR operation more difficult. (The SIAI-Marchetti SF.260 military trainer features most flight instruments on the right seat specifically because most military pilots will fly with the right hand on the stick—side or joy—and the left hand on the throttle—the HOTAS principle.) Airbus industries has embraced side sticks wholeheartedly on its airliners. Boeing sticks to a control yoke.


Diamond Center Stick

Diamond Back Door

15 Conversely, all the Diamond air­planes use center sticks for inflight control. The DA-20 Eclipse, DA-40 Star and DA-42 Twin Star feature a plain, simple joystick to drive the airplane around the sky. That might seem something of a contradiction for an airplane constructed of smooth, nearly seamless carbon fiber and flying behind twin flat screens, but Diamond seems to feel that center sticks are the best, most controllable method of flying a general aviation airplane, and sales suggest many pilots agree. Additionally, the Diamonds feature something you won't find on any other modern four-seat machine—a back door. The DA-40 and DA-42 twin offer a left side aft door for access to the back seat.



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