Hi Maik, > yes, but it is still the double value than the bo. But the incidence > data I have for the bo is measured at 0.7r and therefore much smaller. [...] > I am not sure if that matches the data. With 8° twist and -1.4° pitch at > minimum you will get -9.4° at the tip and something about -7° mean >(weightened with r^2). In autorotation you will get much overspeed. >The >data I have for the bo is measured at 0.7r. The effect is, that a pitch >of 0 degree gives approx. in the same lift as a blade without twist.
I think you are mixing incidence angle (angle of attack) with pitch angle here. [1] is appendix A of my MSc thesis (about helicopter flight dynamics modelling & simulation) in which the mathematical model of the main rotor is derived/explained. Figure A.2 contains a sideview of an airfoil along the span of a rotor blade, which should explain the difference between the two. The main contribution to the vertical component at a blade section (U_p in [1]) comes from the induced inflow. If the induced inflow is not calculated accurately (or not at all), the pitch angles at the blade sections will be much smaller than in reality, since inflow reduces the angles of attack. How is inflow calculated in Yasim? I only can find some reference to 'downwash', but I don't see any familiar equations overthere. > One important point for the simulation: most rotors have a delta3 effect > (this means: reducing the pitch with increased flapping angle). Do you > know this parameter for the ch53e (or for other helicopter?) At our faculty, we normally set delta_3 equal to -45 degrees for the bo105 (i.e. positive blade flapping reduces the blade pitch angle, so stabilizing). Pitch-flap coupling for the AS 330 Puma is zero. I am not sure about other helicopters. Greetings, Wim [1] http://users.pandora.be/tuinbels/afstuderen/appA.pdf On 12/19/06, Maik Justus <[EMAIL PROTECTED]> wrote: > Hi Wim > > wim van hoydonck schrieb am 18.12.2006 23:23: > > Hi Maik, > > > > > > Once our library opens again next year (they are moving to a new > > building), I'll cross check that data with Janes (I work at the > > faculty of aerospace engineering in Delft). > > > > > very good, thank you! > >> Very surprising for me are the > >> cyclic/ collective data with approx 20+18=38 degree maximum incidence of > >> the main rotor. > >> > > > > That's the maximum pitch angle at the root of the blade which is not > > the same as the angle of attack of a blade (element) along the span of > > the blade (inflow induced by the rotor itself reduces the angle of > > attack). > yes, but it is still the double value than the bo. But the incidence > data I have for the bo is measured at 0.7r and therefore much smaller. > > >> Unfortunately I do not have any information about the > >> airfoil (SC1095). > >> > > > > This ([1]) NASA report contains some data about wind tunnel test done > > with that airfoil. > > > > > Perfect. With this data I can calculate the data for the .xml file. > >> One important point: the main rotor and the tail rotor > >> are twisted. Do you know, where the incidence is measured? > >> > > > > Pitch angle (theta) is normally measured from the root of the blade, > > as can be seen in [2], page 322. > I am not sure if that matches the data. With 8° twist and -1.4° pitch at > minimum you will get -9.4° at the tip and something about -7° mean > (weightened with r^2). In autorotation you will get much overspeed. The > data I have for the bo is measured at 0.7r. The effect is, that a pitch > of 0 degree gives approx. in the same lift as a blade without twist. > > Flight path angle (phi) is calculated > > >from the tangential and normal velocity components at a blade element > > and the angle of attack (alpha) is the difference between (or sum of) > > these two (depending on the choice of positive axes). > > > > > >> Do you have such data for other helicopters in your book (bo105 (but > >> here the actual data should be correct), ec135, ec145, ch47d, s76c, > >> little nellie)? > >> > > > > I have access to the majority of editions of Janes All The Worlds > > Aircraft between 1976 and 2006, so yes :) (although I'm not sure > > about little nellie ...) > > > > > One important point for the simulation: most rotors have a delta3 effect > (this means: reducing the pitch with increased flapping angle). Do you > know this parameter for the ch53e (or for other helicopter?) > > > Greetings, > > > > Wim > > > > > > [1] http://halfdome.arc.nasa.gov/publications/files/NASA-TP-2003-212265.pdf > > [2] > > http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19960054374_1996092848.pdf > > > > > > > Thank you, > Maik > > ------------------------------------------------------------------------- > Take Surveys. Earn Cash. Influence the Future of IT > Join SourceForge.net's Techsay panel and you'll get the chance to share your > opinions on IT & business topics through brief surveys - and earn cash > http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV > _______________________________________________ > Flightgear-devel mailing list > Flightgear-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/flightgear-devel > -- Avoid hangovers - stay drunk! ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
