Return-Path: Received: from newsierra.bnis.net ([208.145.132.210]) by truman.olsusa.com (Post.Office MTA v3.5.1 release 219 ID# 0-52269U2500L250S0V35) with ESMTP id com for ; Sun, 18 Jul 1999 09:52:40 -0400 Received: from gnaf (unverified [208.145.132.115]) by newsierra.bnis.net (Rockliffe SMTPRA 2.1.6) with SMTP id ; Sun, 18 Jul 1999 06:48:55 -0700 Message-ID: <001b01bed125$7e24f920$0200a8c0@gnaf> From: "Paul A. Nafziger" To: "Tom Giddings" , References: <37889236.35116F0A@akos.net> <001201becbcf$92570d80$0200a8c0@gnaf> <37892561.65CC72AD@akos.net> Subject: High Stick Forces with Flap Extension Date: Sun, 18 Jul 1999 06:57:36 -0700 X-Mailing-List: lancair.list@olsusa.com Mime-Version: 1.0 <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> << Lancair Builders' Mail List >> <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> >> Well, we invited an experienced aeronautical engineer from NASA Dryden to help us tuft the wings, fuselage, and empanage, which he did. I then flew photo chase on Jim while he cycled the flaps. The airspeeds and altitudes closely agreed between the two airplanes. The C182 I was flying wasn't a calibrated pacer, but it was probably close enough for what we were looking for. The instruments agreed within 50 feet and 2 mph between speeds of 85 to 140 at 7500 msl. He flew past at his cruise speed (I couldn't keep up with my 182). The elevator was nicely faired and the trim tab was neutral. When he deployed the flaps, the tufts remained rock solid except for the flap trailing tufts at flap settings beyond 25 percent. Those tufts pointed inward at that point. At about 50 percent flaps, most of the flap tufts were flopping around. Of course, none of that is unexpected. The nose up pitching moment caused by the flow separation over the flaps at high settings is more than overpowered by the nose down pitching moment caused by the profile drag of the flap. The elevator deflection was about 10 degrees trailing edge up, with the trim tab fully extended trailing edge down. At 50 percent flaps, he estimated about 15 lbs. aft stick force was required. In a nutshell, we found absolutely nothing to explain the high stick forces. I now think the airplane has extremely high elevator hinge moments and the "leverage" the pilot has to move it is small. Stay tuned..... Naf N7PN >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> LML homepage: http://www.olsusa.com/Users/Mkaye/maillist.html