October 2012

Experimenter is a magazine created by EAA for people who build airplanes. We will report on amateur-built aircraft as well as ultralights and other light aircraft.

Issue link: http://experimenter.epubxp.com/i/84816

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Page 36 of 47

defl ecting both rudders simultane- ously will produce an unexpected pitching moment, as well as typi- cally reducing aileron effective- ness because of the disturbed airfl ow over the outer wing panels. (iv) Canards require a dramatic wing sweep to locate the rudders far enough aft on the airframe to be effective. Their dramatic wing sweep causes a strong rolling ten- dency during any uncoordinated fl ight. (A strong yaw-roll coupling effect is a characteristic of all swept-wing airplanes.) Whenever a slidslip is produced by rudder usage (or a wind gust), the airplane will weathervane back into the relative wind as well as roll away from the sideslip. (i.e. a "Dutch Roll" tendency which is also char- acteristic of swept wing airplanes.) During slow fl ight, this rolling tendency may be more powerful than that which can be countered by the ailerons alone. (v) Canard's wheel brakes are typi- cally operated by applying force to the rudder pedal after the rud- der is fully defl ected. This design saves both weight and space, but it means that there is no braking without fully defl ecting the rudder. This works well for taxiing, but warrants consideration (and famil- iarity) for crosswind operations. d. Other confi gurations that may cause problems are as follows: (i) Hand lever operation of the wheel brakes can be found in some earlier Piper Cherokee aircraft that did not incorporate the toe-brake option. Hand brakes require the pilot to release either the stick or throttle control to operate the hand brake lever, and it's your arm strength that determines the braking effectiveness. If brakes are cable actuated (via a single brake lever), cable rigging becomes a critical issue in order to prevent asymmetric brake application. (ii) High-wing-mounted engine confi gurations (usually pushers) cause a reverse thrust-vector effect in which increasing power pitches the nose down (instead of up) and reducing power pitches the nose up (instead of down). Although pilots adapt to this effect, it complicates maneuvers such as a rejected landing go-around. Becoming thor- oughly familiarity with the airplane's pitch-power interface is essential to safe fl ight. (iii) Pilot interface with the control surfaces has a large infl uence on workload, handling qualities, and overall satisfaction with the aircraft. A short side-stick, which requires a lot of effort to move, will limit ma- neuverability, and this disadvantage will grow as the airplane's speed increases. Quickly fi nding the neu- tral stick position after an airplane upset can also be very diffi cult with side-stick controls. (iv) Pilots typically enjoy a tac- tile reference for their stick arm, usually resting their forearm on their thigh. Side-stick designs, without an arm rest, deprive the pilot of this reference and make fi ne adjustments diffi cult, leading to unwanted control inputs during turbulence. In designs with single side-stick between the seats, poor implementation can limit roll con- trol due to interference with the pilot's or passenger's leg. 4. Recommended Training is as follows: a. Ground training should allow the pilot to become thoroughly familiar with the location, force required, displacement, and operative sense requirement of all the cockpit controls. Know your airplane's systems, limits and recommended procedures before you begin fl ying. Practice simulated emergency proce- dures while on the ground. Consult the kit vender, type club members, and other owner/builders of your airplane model for additional information. b. Flight training recommendations are as follows: (i) Best training is accomplished in your specifi c airplane with a well-qualifi ed instructor who is experienced in the specifi c make and model. (ii) Second best training source is from the kit vendor, either in your airplane or in their demonstrator of the same model airplane. (iii) Third best training source is information from and fl ying with the previous owner, if you pur- chased your aircraft already built. (iv) All training should empha- size the unique aerodynamic behavior of your airplane's non-traditional confi gurations, as well as any pilot compensa- tion required to safely fl y the airplane. If any of your airplane's cockpit controls are different from what you are accustomed to, insure that you have become familiar with the advantages and disadvantages of the design. Be sure that you explore your plane's handling qualities under safe, supervised conditions. The thought for this month is "Not being known doesn't stop the truth from being true." - Richard Bach, American author. So, until next month, be sure to Think Right to FliRite. Hobart C. "Hobie" Tomlinson is the Director of Safety for Heritage Aviation, Inc., in South Burlington, Vermont. He is also a Flight Advisor for EAA Chapter 613. He received the 2012 Spirit of Flight award from the Society of Experimental Test Pilots.. He was also named the 2012 National CFI of the year by FAA. EAA EXPERIMENTER 37

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