---------------------------------------------------------- Europa-List Digest Archive --- Total Messages Posted Sun 05/23/10: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 12:54 AM - Navaid Servos.....no longer (Tony Renshaw) 2. 01:35 AM - Re: Effects of Flaps and Ailerons on Pitch Trim (JonSmith) 3. 03:32 AM - Engine Mount Strengthening Mod (Tony Renshaw) ________________________________ Message 1 _____________________________________ Time: 12:54:52 AM PST US Subject: Europa-List: Navaid Servos.....no longer From: Tony Renshaw Jerry from Trio advised me that Navaid Servos are no longer available, which is why they built there own. Reg Tony Renshaw Sydney Aussie ________________________________ Message 2 _____________________________________ Time: 01:35:34 AM PST US Subject: Europa-List: Re: Effects of Flaps and Ailerons on Pitch Trim From: "JonSmith" Hi Jos, I am very sorry but I have to disagree with nearly everything in your recent posting! Your points are relevant to a "conventional" fixed tailplane with separate elevators and trim tab, but not to the Europa tail which is a masterpiece of design! The thing is - your comments about "needing trim tab deflection" apply to a conventional elevator - which is in effect a trailing control surface or tab itself. This conventional elevator will always need to be "held" against a restoring force from the airflow and the trim tab deflection provides this "holding force", or trim as we call it. The Europa tail principle is different however. The job that the horizontal tail surface does is the same on ALL conventional fixed wing aircraft (Europa, C-150, Piper Cub, whatever) - it provides a small downforce to balance the nose down pitch effect generated by the wing. It will always be a downforce needed from the tail because the C of G is always forward of the Point or Centre of the Lifting force generated by the wing. It is only a small downforce needed from the tail because of the distance the tailplane is from the wing - you have a long spanner!! As the Europa has a symmetrical section tailplane then this downforce has to be generated by a slightly negative angle of attack of the Relative Airflow to the tailplane. (Look at the line drawings of the aircraft - the tailplane's incidence in the neutral position is slightly negative to the fuselage waterline/ reference line - the wing's incidence of course is 2.5 deg positive). The downforce can be varied by the pilot adjusting the angle of the tailplane with the stick (control) or by changes to the Relative Airflow by say a gust (the starting point of the aircraft's natural longitudinal stability). Now the clever bit regarding the Europa! The tailplane is "AERODYNAMICALLY BALANCED" which means that the tailplane can provide this "lift" force (downforce) BUT REGARDLESS OF THE PRODUCTION OF THIS DOWNFORCE AND THE AMOUNT OF IT THE TAILPLANE(OR ELEVATOR CONTROL) WILL NOT BE DEFLECTED AWAY FROM IT'S CURRENT POSITION EVEN WHEN THE GENERATED DOWNFORCE CHANGES BY CHANGING RELATIVE AIRFLOW. THE TAILPLANE WILL NOT BE DEFLECTED BY THE RELATIVE AIRFLOW, EVEN IF THIS AIRFLOW CHANGES IN DIRECTION OR SPEED RELATIVE TO THE TAILPLANE. This is due to this very clever aerodynamic balance. Basically any "rotating" force on the tailplane created by the airflows's angle of attack will be the same behind the pivot (torque tube) as that created in front of it. In other words the slight negative angle of attack causes the airflow to "push down" on the tailplane from above with an equal average force behind the torque tube as in front of it. This is true regardless of speed and the angle of the airflow and so the tailplane will never be deflected by just the airflow even if the airflow changes. This is very hard to visualise because of course the surface area of tailplane behind the torque tube is very much greater than in front of it - but THE SHAPE or cross section of the tailplane is also very different fore and aft of the torque tube and due to the beautiful design this AERODYNAMIC BALANCE IS THERE!! Now then - TRIM TABS!! The job of the tabs on the Europa is to hold the tailplane in the position that the pilot wants it to stay in! THE TAILPLANE WILL STAY IN IT'S CURRENT POSITION ONLY WHEN THE TRIM TABS ARE FLUSH WITH THE TAILPLANE SURFACE. IF THE TABS ARE NOT FLUSH THEN THEY WILL BE CREATING A ROTATING FORCE ON THE TAILPLANE THAT WILL WANT TO MOVE IT FROM IT'S CURRENT POSITION TO ACHIEVE THE TABS-FLUSH STATE AGAIN. If the tailplane moves out of the chosen trimmed position - maybe the pilot inadvertantly moves the stick - then because of the clever linkage design, the tabs move from their flush position in the same direction. (Tailplane trailing edge moves up - tabs move up). The tabs thus provide an aerodynamic "restoring force" to put the tailplane back where it was - in other words it's original trimmed position with the tabs flush again! The trim switch/ control on the Europa merely resets or adjusts the tailplane position where the tabs are flush with the surface. The required tailplane position simply depends on how much downforce you want it to make which depends entirely on what you are doing with the aircraft! So, the functions of the tabs are: 1/ To hold the tailplane in the chosen position (tabs flush when achieved) and provide a restoring force to the tailplane if it is moved away from it's chosen trimmed position - this is known as "feel" that is provided to the pilot through the stick - the further you move the stick away from the chosen trimmed position (without re-trimming) the greater the tab deflection and thus the greater this restoring force will "feel". If there were no tabs then the tailplane would just stay wherever the pilot put it, regardless of speed/ airflow etc - but there would be no "feel" to the elevator at all (zero feel). 2/ To be pilot-adjustable so that you can reset the trimmed (tabs flush) tailplane position as required during flight. Note that none of this theory specific to the Europa tailplane control is connected to the aircraft's longitudinal stability theory - that is a different subject and has no relevance specifically to balanced tailplanes or otherwise. Longitudinal stability theory is the same on all conventional fixed wing aircraft regardless of tailplane design. Variances: A perfectly constructed and balanced tailplane will always have it's tabs flush with the tailplane in steady correctly trimmed flight, regardless of speed and attitude. Variation in build MAY affect this perfect state. If the aerodynamic balance of the tailplane is not quite perfect (not quite the perfect tailplane profile section) then the balance of forces (created fore and aft of the torque tube) might not be quite perfectly equal with the trim tabs flush and so a slight tab deflection in the appropriate direction will be permanently needed in steady trimmed flight to balance the forces up again. Not a problem, just very slightly less efficient due to the slight increase in drag caused by the permanently deflected tabs. Also if the counterweight (mass balance weight) in the fuselage is not perfectly correct then this too will create an unwanted rotating force on the tailplane that would require an (unwanted and continuous) tab deflection to counter/ balance out this unwanted force. Also, if the pilot flies "out of trim" for some reason then a tab deflection will be required in the appropriate direction to oppose the pilot's push or pull force on the tailplane. This one can easily be corrected though!!! The only real way to tell if your tailplane system is absolutely perfect in balance (aerodynamically as well as in weight) is to trim the aircraft perfectly in steady flight (any steady speed) and get a mate to come up behind you and take a close up photo of your tabs. In a perfect set up they will be flush with the tailplane!!!! Cheers, Jon -------- G-TERN Classic Mono Read this topic online here: http://forums.matronics.com/viewtopic.php?p=298563#298563 ________________________________ Message 3 _____________________________________ Time: 03:32:46 AM PST US Subject: Europa-List: Engine Mount Strengthening Mod From: Tony Renshaw Gidday, I have just reamed out the undercarriage frame tubes that support the welded engine mounts attachments. I'm not convinced this is a good mod, at all. If the premise is to stop flexing of the attachment frame top tubes, I see the load now being focused on an area of circumferential stress, created by the end of the reamed tube and the closely proximated vertical bolt that holds the frame into the tunnel. The metal tubular inserts apply all the load on their ends, which is where this transition of internal diameters occurs, right up agains the bolt attachment. I am lucky as I have not yet installed the bolts. If I had, I would be very concerned. I personally reckon for anyone who hasn't done this mod to extend the inserts the entire length, and then drill through both tube and insert for attachment. This will obviously mean reaming out the entire length too, which can be easily done by welding an extension on the reamer. So, in anticipation of "doing it my way", I am interested in advice on what type of metal the insert would be please, for ordering purposes. For those wanting to consider this option, the longer inserts require 2 x 200 mm long x 16.5 mm dia x 2 mm wall thickness. In anticipation. Reg Tony Renshaw ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message europa-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Europa-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/europa-list Browse Digests http://www.matronics.com/digest/europa-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.