5 Steps to Trimming a Pattern Plane

[Charlie Rock]

  ----- Original Message ----- 
  From: Don Szczur 
  To: discussion at nsrca.org 
  Sent: Friday, December 03, 2004 10:22 PM
  Subject: Re: 5 Steps to Trimming a Pattern Plane


  Well, let me clarify about the spin entries...  I think things got mixed up in the discussions and I digressed.  I had aileron mix in with down elevator mix.  I thought about it some more.

  Now, before I changed wing incidence, I mixed in some right aileron with low throttle.  This kept the wings (and plane) tracking straight in a spin entry (particularly inverted spin entries, since at the time it was tough putting in left rudder when approaching the spin entry).  Even my 1995 Typhoon needed this, although I did not do any incidence change at that time, I just did the idle to aileron mix.  I think I remember doing a mix condition on my Dr. Jekyll so that with the gear up, and on high rate, the mix would go in (elevator).  That way the elevator trim would not change on landing approach from what I was used to.  I remember now that I also used to put in 1/8 inch left rudder trim activated with high rate switch for the spin entry.  This would keep it from "breaking" to the right... but again, I digress...The issue with the idle-to-aileron mix- I found that the wings would (very slowly, like 5 degrees to the right) drift at/during the bottom of a pull out.  Example would be at the bottom of a square loop, as the plane pulls out of a vertical down line to horizontal, (going fast) the plane would roll slightly right as its going fast...

  So I discovered in 2003 the one application that I have effectively used negative wing incidence, but only on the left wing.  Specifically speaking, all of my planes that I've flown in the last 5 years required about 1/8 inch negative incidence in the left wing, sometimes more..  This included two generation of ARF's, one professionally built plane, and another one (plus my TOC plane).  

  So the left wing neg incidence requires right aileron trim for straight and level cruise speed flight, and as the plane slows down that right aileron trim takes over, resulting in a nice straight, stable spin entry (either inverted or upright).

  Here is a story.  During the first couple of flights on my pro built FOCUS 1 1/2, I was ready to throw it in the trash because with the throttle to aileron mix it would be comical to watch.  I'd be in stright flight at full throttle and then I'd quickly cut the throttle to idle. The plane would do a slow roll to about 45 degrees right.  If I reduced the aileron mix so that down lines were fine, then it would not be enough throttle to aileron mix for a good spin entry.  Needless to say I just started aggressively cranking in the adjusters on the left wing and after the left wing smashed into the top of the left landing gear strut (making a nice 1/16 inch indent in the bottom of the wing) the plane flew like magic.  I screamed with joy.  It flew to win the NATS.

  OK, buy me an ice cream cone at the next NATS for that tip.

  Don
    ----- Original Message ----- 
    From: Rcmaster199 at aol.com 
    To: discussion at nsrca.org 
    Sent: Sunday, November 28, 2004 11:01 PM
    Subject: Re: 5 Steps to Trimming a Pattern Plane


    If I read both your commentaries correctly, the elevator mix when at idle, to help eliminate the up pitch of the down line, should also help the inverted spin entries. Particularly on a nose heavy plane (or one with considerable pos incidence), it seems to me that down elv mix at idle should help both conditions. What did i miss?

    MattK


    In a message dated 11/28/2004 9:34:36 PM Eastern Standard Time, dszczur at maranatha.net writes:
      Lance, thanks very much for the comments.  Bottom line is do what ever it takes to make the plane fly the way you want it to.  Mechanical, or electronic, or both. The vertical stab helps to stabilize in neg spin entry, and because I fly nose heavy, I don't feel the extra down mix in a spin entry.  Now, realize I don't have very much mix in... so that is less of an overall factor.

      Don
        ----- Original Message ----- 
        From: Lance Van Nostrand 
        To: discussion at nsrca.org 
        Sent: Friday, November 26, 2004 1:14 AM
        Subject: Re: 5 Steps to Trimming a Pattern Plane


        Don,
        Clearly this works for you, but I am still unconvinced.  Wouldn't more pos incidence in the wing, to assist spin entries, only work for upright spins?  FAI has inverted spins, and this should work in the opposite direction.  Same goes for the Throttle/Elv mix. When you reduce throttle to enter the spin, the elv mix that was put in for downlines might affect your spin approach.  And when the spin entry is inverted you'll have to really get on the down elv to maintain level approach.  I guess it can work, but it seems like its introducing factors that make the pilot begin to fly against the mix.
        --Lance

          ----- Original Message ----- 
          From: Don Szczur 
          To: discussion at nsrca.org 
          Sent: Monday, November 22, 2004 10:29 PM
          Subject: Re: 5 Steps to Trimming a Pattern Plane


          Lance, incidence may take care of pitch or roll, but not always.  In fact, I found that changing wing (panel) incidence has the most dramatic impact on slow flight, such as entries to a spin.  CG and wing balance also play some part in this mix. The electronic mixing takes care of what incidence changes, (wing warping, etc.) will not address in a down line, or, if you choose to just electronically dial out the tendency.

          Cheers!

          Don
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