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  1. #1

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    Down elev -> ail mix?

    Hello Don!! How are you? Are you flying pattern in this period?

    Here the temperature is still not too low, so I can continue the trimming process of my new airplane...

    I was reading an interesting trimming tutorial by Chip, appeared on a old Ultimate manual. After the first basic trimming steps, he addressed the trimming needed to do good and straight loops. After trimming for inside loops, he said to switch to outside loops. When performing these, chip says that it can happen that the airplane will have some induced roll with down elevator applied, and the fact that it is normal, considering the prop effects ("the plane is not crooked"). The suggestion he provided was to set up another mix to straight that bad tendency: down elev -> ail.

    Since I never saw such a mix described by the top pilots, I ask to you: do you use it, or have noticed that bad tendency when performing outside loops?


    As usual many thanks for your great help.

  2. #2
    Don Szczur's Avatar
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    RE: Down elev -> ail mix?

    Hello! This is an open answer to all those pilots in the world to read and learn from this forum. This is a common issue. Very carefully do either humpy bump or half reverse cuban 8's. Notice that either from left to right or right to left to decide if its coming in or going out at the exit of the maneuver. If it comes in on the right and goes out on the left, there is need for adjustments. Be sure to fly with the wings level during the pull up and around the top, and make sure that the down line is straight and your wings are level. This will isolate the problem to the radius You can mix in just a little bit of aileron as a mutli-point mix at point 4 (1/4 throttle mix in, out at 1/8 stick of low throttle). You normally advance throttle during a radius. Now, do this mix after you do the incidence check, thrust check, and throttle to rudder mix. I can go into these in detail with you for these if you would like. Oh yes, and the wing CG check is helpful also. Put a little weight on the opposite wing first. I did this on my 40% Extra and it did help. Basically you want perfect pull out so that (in very calm air like it gets this time of year, approximately 30 minutes before sunset) the plane should fly parallell to the flight line after each pull out of a half referse cuban 8 or at the bottom of the humpty bump. This greatly reduces the pilot workload during unknown sequences, if you fly F3A finals Unknowns, or it will also help during known sequences- although most learn to adapt subconciously for known due to the hundreds of practiced sequences (learned response). If you spend three weekends trimming now, you will be paid off by months ahead of flying ability next year.

    Ciao!

    Don

  3. #3

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    RE: Down elev -> ail mix?

    GREAT DON!!!

    The whole thing is not cristal clear to me. First, why do you say that the mix should be active only from 1/8 to 1/4 of throttle (if I figured out correctly)? Furthermore, that thing seems a bit related with wing tip weight, since the symptoms are similar... So, first lateral CG (with inside pulls or inverted flight method?) and then we can check the down elev mix.

    I can't understand, from a physical point of view, whay the plane should roll with down elev and not with positive input??? Assuming correct wing tip, rutter trim...

    If you want go in deeper detail about throttle -> rudder method, it would be very interesting!!! I think after several tests I finally set up this issue, but it is extremely helpful to hear YOUR method!

  4. #4
    Don Szczur's Avatar
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    RE: Down elev -> ail mix?

    Also check to make sure an aileron is not warped. Next, tip weight is also a key item. Check these first. If they don't work, use radio mix to do whatever it takes to get the plane to fly hands-off and pulls and pushes are generally where you want them.


    For tip weight, I drelled a lifted up the aileron and drilled a hole then pushed in several screws, then re-covered the tip. Top hinged aileron makes this easier, but it can be done with any wing- on the bottom tip so you won't notice the slit in the covering/patch.

    It is very difficult to trim but easy once you learn- I just have someone stand next to me, take my hands off the stick, and ask them "what is the plane doing?". I always know the answer, but like to hear it from a second set of eyes for confirmation. Plane should fly straight up, straight down. LIke a plum bob. Ailerons must be carefully trimmed so its hands-off (elevator too) flying across the field left to right and right to left. You have to make sure its perfectly trimmed in level flight first before going to vertical upline and downline trim. Finally, as we discussed above the wing warp check, tip weight check and p-mix as a final resort.

    CHeers!

    Don

  5. #5
    Don Szczur's Avatar
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    RE: Down elev -> ail mix?

    Here is some experience with the FOCUS aircraft. Well, let me clarify about the spin entries... 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.
    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.


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