project pattern
F
Redux
ollowing last month’s column chock full of expert advice and setup in- formation for YS engines, I extend “thanks” once more to Brian Clem- mons for conveying the wealth of knowledge from the “Bear”; Bryan Hebert. While the majority of Pattern pilots, myself included, are using a variety of electric powerplants, the YS is for all practical purposes the sole surviving internal combustion engine viable for Pattern.
As noted by Brian, electric powerplants have ushered in a new wave of powerplant wars, and pushed further development of YS engines. At the 2013 F3A World Champi- onships, eight of the ten pilots in the finals were flying electrics but it was Christophe Paysant LeRoux winning his 7th World Championship flying YS.
The November 2013 installment of Project Pattern included a brief bit of information on the first flights of Yuri. Additionally, I de- scribed “behavior” traits (primarily margins of pitch and yaw stability, and the balance between them) I find to be ideal for Pattern planes, and a couple aerodynamic laws/real- ities (spiral airflow, “1G” wing lift, and het- erogeneous airmass) that must be accounted for in the trimming process. As of this writ- ing, Yuri has logged close to 200 flights, and is in what I consider to be excellent trim con- dition. Before delving into the details of the trimming process for Yuri, I want to provide a little more context on trimming. “Trim condition” is a state or topic that has led to more than a few passionate dis- cussions among Pattern pilots. Most cer- tainly the ideal behavior traits are not con- gruent for all Pattern pilots (we all have our own preferences and biases); however, I can not fathom any Pattern pilot arguing
by dave lockhart with algirdas ungulaitis You can reach Dave Lockhart via e-mail at
davel322@comcast.net
PHOTOGRAPHY: DAVE LOCKHART
Very minor changes in fuselage side area can have a substantial effect on yaw behavior in crosswinds and during maneuvers that integrate looping and rolling elements. Shown here are the Pegasus PH II (top) and subsequent Pegasus PH X(bottom) from long time Japanese F3A Team member, Hajime Hatta.
against the ideal trim condition being one in in which: • The plane flies straight and level with no inputs, and maintains this trim state for any speed between a moderately slow pace and full throttle. • The plane will climb vertically with no inputs; after establishing the vertical climb.
• The airplane will dive vertically with no inputs; after establishing the vertical dive. • The airplane will maintain knife edge flight in a straight line with only rudder in- put. • Each control axis is absolutely pure with no coupling at any speed.
While any plane that meets the above cri- teria is certainly an accomplishment, meet- ing the above criteria alone is no guarantee that the plane is a good Pattern plane. The plane also has to be capable of completing virtually every aerobatic maneuver. “Virtu- ally” meaning every possible combination of loops, rolls, snaps, spins, and stall turns, but excluding “3D” maneuvers like torque rolls, harriers, tumbles, etc. The best 3D planes can certainly meet the above criteria in nor- mal maneuvering, but it is increasingly dif- ficult to meet the above criteria with in- creasingly extreme 3D maneuvers. Given that a plane meets the criteria and
Ron Lockhart (L) and Bob Noll (R) are clearly having a trimming discussion. At the very least, it is likely they are having a trimming discussion as it is a very common topic at Pattern events.
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can complete all the maneuvers, it is still not guaranteed that the plane is a good Pattern plane. For example, if the plane is very sen- sitive to the timing of control inputs or entry airspeed for snap rolls, it could be quite a challenge to consistently perform snap rolls. A plane with a broader “sweet spot(s)” for airspeed and control inputs would be easier to consistently snap roll, and therefore be a “better” Pattern plane. Obviously, how easi- ly a plane completes snap rolls is relative/ subjective, but the point is that given all oth- er things equal, the plane that has the broadest sweet spot(s) and is easier to fly is a better plane.
JANUARY 2014
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