---------------------------------------------------------- KIS-List Digest Archive --- Total Messages Posted Wed 04/06/11: 6 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 02:28 AM - Re: Landing the KIS TR-1 (BlueSkyFlier) 2. 08:58 AM - Prince propellers and rain (Scott Stearns) 3. 03:49 PM - Re: Re: Landing the KIS TR-1 (Graham Brighton) 4. 04:49 PM - Re: Landing the KIS TR-1 (BlueSkyFlier) 5. 07:49 PM - Re: Re: Landing the KIS TR-1 (Mark Kettering) 6. 10:02 PM - Re: Re: Landing the KIS TR-1 (Larry David) ________________________________ Message 1 _____________________________________ Time: 02:28:37 AM PST US Subject: KIS-List: Re: Landing the KIS TR-1 From: "BlueSkyFlier" Of particular interest in the diagram which illustrates changes in lift coefficient in ground effect [attached to previous message above] is the tendency for lift to drop away when less than 20% of wingspan away from the ground if the CL > 2. With full flaps the TR-1 wing can apparently achieve CL > 2 if the angle of attack is steep enough. In fact, when holding off with full flaps at high angle of attack in close proximity to the ground it is likely that this unexpected drop-off effect could be encountered - not to mention the contribution of adverse tail plane effects. It therefore seems important to keep the angle of attack fairly conservative. This can be done by flying the main gear into touch with a fairly low angle of attack and comfortable speed (probably > 60 kts) . Once the gear is down the nose can be pulled up gently to generate maximum drag (the TR-1 will fortunately not easily lift off again without power). (The equation from which the lift coefficient chart attached above was created is attached below for interest. The TR-1 aspect ratio being less than 7 will tend to exacerbate the unwanted effects.) -- ** -- -------- _________________________________________ Read this topic online here: http://forums.matronics.com/viewtopic.php?p=336265#336265 Attachments: http://forums.matronics.com//files/ground_effect_lift_equation_211.jpg ________________________________ Message 2 _____________________________________ Time: 08:58:01 AM PST US From: Scott Stearns Subject: KIS-List: Prince propellers and rain Hello all, - I wrote to the Prince propeller guy about the effects of rain on his propel lers and here is his response.- My propeller is about 2 years old. - Scott Mr. Stearns, - As we have been taught in pilot training it is best, even with a metal prop eller, to reduce rpm to slow erosion of the propeller. The propeller will h ave paint wear in moderate or greater rain as with any propeller be it meta l or with leading edge protection. We offer a leading edge tape kit to redu ce this condition. Your propeller was our older epoxy based material and do es work well but continued use at high rpm in moderate or greater rain will shoe wear. Our new material, urethane, is much more durable. - www.princeaircraft.com Lonnie Prince CEO/President Prince Aircraft Company PO Box 2669 6774 Providence Street Whitehouse, Ohio 43571 Tel. (419)877-5557 Fax (419)877-5564 e-mail lonnie@princeaircraft.com ________________________________ Message 3 _____________________________________ Time: 03:49:33 PM PST US From: "Graham Brighton" Subject: Re: KIS-List: Re: Landing the KIS TR-1 Alfred , Thx for sharing ur amazing and comprehensive study of the Laminar Flow lift characteristics that CHANGE at landing as applied to our TR-1 .. My head like others is still er..'spinning' ...but ..ur preposition as i understand it ....which is backed up ur substantial research is ....that its the lift changes on our Laminar Wing at touch down that causes the nose to drop and be hard/impossible to hold up after mains touch down ... ( the wing lift/moment changes causes the Tail to loose authority to counter the drop) .. However with careful Speed and Flap selection the 'Nose Drop' effect can be minimized .. Great work ...Do i have this rite or .... !? Graham TR1 #80 .. ----- Original Message ----- From: "BlueSkyFlier" Sent: Wednesday, April 06, 2011 7:27 PM Subject: KIS-List: Re: Landing the KIS TR-1 > > > Of particular interest in the diagram which illustrates changes in lift > coefficient in ground effect [attached to previous message above] is the > tendency for lift to drop away when less than 20% of wingspan away from > the ground if the CL > 2. > > With full flaps the TR-1 wing can apparently achieve CL > 2 if the angle > of attack is steep enough. In fact, when holding off with full flaps at > high angle of attack in close proximity to the ground it is likely that > this unexpected drop-off effect could be encountered - not to mention the > contribution of adverse tail plane effects. > > It therefore seems important to keep the angle of attack fairly > conservative. This can be done by flying the main gear into touch with a > fairly low angle of attack and comfortable speed (probably > 60 kts) . > Once the gear is down the nose can be pulled up gently to generate maximum > drag (the TR-1 will fortunately not easily lift off again without power). > > (The equation from which the lift coefficient chart attached above was > created is attached below for interest. The TR-1 aspect ratio being less > than 7 will tend to exacerbate the unwanted effects.) > -- ** -- > > -------- > _________________________________________ > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=336265#336265 > > > Attachments: > > http://forums.matronics.com//files/ground_effect_lift_equation_211.jpg > > > ________________________________ Message 4 _____________________________________ Time: 04:49:45 PM PST US Subject: KIS-List: Re: Landing the KIS TR-1 From: "BlueSkyFlier" Hi Graham, Unfortunately it is never just one thing. Far too much going on at the same time to be that simple :o) The wing effects, flaps effects and changed airflow on the tail section all play their part. The upwash effects on tail plane could vary dramatically with speed, flap setting, angle of attack, and height above ground. Most people (myself included) were told in training that ground effect always increase lift. As the references illustrate that statement should be qualified with the provision that the angle of attack needs to be small enough. With low wing aircraft in particular, the proximity of the trailing edge of the flaps to the ground can work in one's favour if the lift coefficient is small enough, but could just as well have exactly the opposite effect if one is not careful with angle of attack. The bottom line is that unless these adverse factors are avoided, any or all of them can contribute to the craft and/or nose gear coming down faster than one would want or expect. Each pilot will naturally develop their own way of dealing with these effects, but understanding of the various parameters at play can only be beneficial. Regards, Alfred -------- _________________________________________ Read this topic online here: http://forums.matronics.com/viewtopic.php?p=336321#336321 ________________________________ Message 5 _____________________________________ Time: 07:49:26 PM PST US From: Mark Kettering Subject: Re: KIS-List: Re: Landing the KIS TR-1 I may be wrong but it seems to me that this is looking for a complex reason for a very simply issue. As designed the main gear is too far aft. I think most if not all of the problem is once the mains touch down they impart a huge nose down moment due to their placement too far aft of the CG. I do not think anyone has had a real issue holding the nose up when flying even in low ground effect. I think the issue is only after the mains contact. I also very much suspect the diagram and equation. I would really like to see the theory, math and experimental data behind it. To me it looks like a suspect empirical equation that seem to be way too popular in some aircraft design textbooks and in many papers. Not that empirical equations are not useful. They are! But you really need to be careful when applying them especially at one end or the other as in this case. But even if the equation is correct I very much doubt the KIS achieves much more than 1.8 Cl even in the flapped area so this should still not be an issue. Again, I could be wrong. And I am sorry if I am stepping on any toes but just wanted to express a counterpoint. Mark -----Original Message----- >From: BlueSkyFlier >Sent: Apr 6, 2011 5:27 AM >To: kis-list@matronics.com >Subject: KIS-List: Re: Landing the KIS TR-1 > > >Of particular interest in the diagram which illustrates changes in lift coefficient in ground effect [attached to previous message above] is the tendency for lift to drop away when less than 20% of wingspan away from the ground if the CL > 2. > >With full flaps the TR-1 wing can apparently achieve CL > 2 if the angle of attack is steep enough. In fact, when holding off with full flaps at high angle of attack in close proximity to the ground it is likely that this unexpected drop-off effect could be encountered - not to mention the contribution of adverse tail plane effects. > >It therefore seems important to keep the angle of attack fairly conservative. This can be done by flying the main gear into touch with a fairly low angle of attack and comfortable speed (probably > 60 kts) . Once the gear is down the nose can be pulled up gently to generate maximum drag (the TR-1 will fortunately not easily lift off again without power). > >(The equation from which the lift coefficient chart attached above was created is attached below for interest. The TR-1 aspect ratio being less than 7 will tend to exacerbate the unwanted effects.) >-- ** -- > >-------- >_________________________________________ > > >Read this topic online here: > >http://forums.matronics.com/viewtopic.php?p=336265#336265 > > >Attachments: > >http://forums.matronics.com//files/ground_effect_lift_equation_211.jpg > > ________________________________ Message 6 _____________________________________ Time: 10:02:34 PM PST US From: Larry David Subject: Re: KIS-List: Re: Landing the KIS TR-1 Several years ago, Julian Bone did a rather complete study of the airflow effect of the KIS wing fairing. It appears from a book by Stinton, page171, that if the wing fairing needs about an 8 inch radius instead of the ~3 in radius it has. With the ~8 inch radius, the airflow over the tail will not be turbulent and the nose will not drop unexpectedly. Julian modified his plane accordingly and it solved the problem. I found the Stinton book very interesting. (I think the title was "The design of an Airplane." I loaned my copy to another builder so have to trust my memory on the title so I may not be right.). Hope this sheds some more light on the issue. Larry On 4/6/2011 4:48 PM, BlueSkyFlier wrote: > --> KIS-List message posted by: "BlueSkyFlier" > > Hi Graham, > > Unfortunately it is never just one thing. Far too much going on at the same time to be that simple :o) > > The wing effects, flaps effects and changed airflow on the tail section all play their part. The upwash effects on tail plane could vary dramatically with speed, flap setting, angle of attack, and height above ground. > > Most people (myself included) were told in training that ground effect always increase lift. As the references illustrate that statement should be qualified with the provision that the angle of attack needs to be small enough. > > With low wing aircraft in particular, the proximity of the trailing edge of the flaps to the ground can work in one's favour if the lift coefficient is small enough, but could just as well have exactly the opposite effect if one is not careful with angle of attack. > > The bottom line is that unless these adverse factors are avoided, any or all of them can contribute to the craft and/or nose gear coming down faster than one would want or expect. Each pilot will naturally develop their own way of dealing with these effects, but understanding of the various parameters at play can only be beneficial. > > Regards, > Alfred > > -------- > _________________________________________ > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=336321#336321 > > ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message kis-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/KIS-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/kis-list Browse Digests http://www.matronics.com/digest/kis-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.