vCUJOv Posted December 12, 2014 Share Posted December 12, 2014 Please look at the video. The second stall looks little messed up to me. https://www.youtube.com/watch?v=ZiVCmMyWPVU Link to comment Share on other sites More sharing options...
Anatoli-Kagari9 Posted December 12, 2014 Share Posted December 12, 2014 Hmmm, noticed you're starting faster on the 2nd test ( using rudder only ), so, that may be the reason for initially going up the way you go ? Flight Simulation is the Virtual Materialization of a Dream... Link to comment Share on other sites More sharing options...
vCUJOv Posted December 12, 2014 Author Share Posted December 12, 2014 Hmmm, noticed you're starting faster on the 2nd test ( using rudder only ), so, that may be the reason for initially going up the way you go ? It does not matter how fast I was when I started the climb. The stalling speed is the same. Point is, the more right rudder you add the more she wants to pitch up. Specially noticeable at low speeds. Try it. You don't even have to be climbing. Set her level at around 250 and slowly add little right rudder. Link to comment Share on other sites More sharing options...
red777 Posted December 12, 2014 Share Posted December 12, 2014 What was the trim setting ? Link to comment Share on other sites More sharing options...
vCUJOv Posted December 12, 2014 Author Share Posted December 12, 2014 (edited) Same for both, full down +1.5.. I shouldn't matter at stall speed. During the first attempt without right rudder my stick was fully aft and the and the nose dropped down as it should. Second attemp stick was neutral and only right rudder was added as she started to slow down. The more rudder I added the more she wanted to pitch up. Edited December 12, 2014 by vCUJOv Link to comment Share on other sites More sharing options...
Kwiatek Posted December 12, 2014 Share Posted December 12, 2014 Hmm gyroscopic precision should rather casue nose down moment with apply right rudder ( prop is clockwise in 109). Link to comment Share on other sites More sharing options...
Anatoli-Kagari9 Posted December 12, 2014 Share Posted December 12, 2014 (edited) Hmm gyroscopic precision should rather casue nose down moment with apply right rudder ( prop is clockwise in 109). Exactly, and that's why I excluded that hypotseis.... vCUJOv, of course the stall AoA is the same, not necessarily the speed, but what I meant was that you were able to pitch up initially more agressively due to the additional speed ... But there must be something wrong... I'll give it a try to tonight ... Edited December 12, 2014 by jcomm Flight Simulation is the Virtual Materialization of a Dream... Link to comment Share on other sites More sharing options...
Thumper1606688436 Posted December 12, 2014 Share Posted December 12, 2014 (edited) I noticed the wing slat were open. Not sure what effect open wing slats will have. I always thought the slats dropped open under gravity so not sure how they can be open in a pitch up situation. Edited December 12, 2014 by "Thumper" Link to comment Share on other sites More sharing options...
ED Team Yo-Yo Posted December 12, 2014 ED Team Share Posted December 12, 2014 (edited) P-factor as well : right pedal, nose up and additionally right. UPD I just managed to watch the video - your stalling technic looks wrong. As you pull the stick at high IAS you force the plane to climb. Instead of that you must pull the stick as much as it is required to maintain zero at VSI. The reason that the plane goes up better could in increased drag as the ball is not in the center. Or different starting speed of pulling. All I wrote above is for power-on and/or massive pedal input. Edited December 12, 2014 by Yo-Yo Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles. Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me Link to comment Share on other sites More sharing options...
Kwiatek Posted December 12, 2014 Share Posted December 12, 2014 So the question is what is more strong P-factor pitch up moment or gryscopic pitch down moment :P Link to comment Share on other sites More sharing options...
vCUJOv Posted December 12, 2014 Author Share Posted December 12, 2014 (edited) P-factor as well : right pedal, nose up and additionally right. UPD I just managed to watch the video - your stalling technic looks wrong. As you pull the stick at high IAS you force the plane to climb. Instead of that you must pull the stick as much as it is required to maintain zero at VSI. The reason that the plane goes up better could in increased drag as the ball is not in the center. Or different starting speed of pulling. All I wrote above is for power-on and/or massive pedal input. Does it really matter how fast I was climbing? As I climb the airspeed will drop to stall speed eventually and I should be forcing the nose up more and more as the airspeed decreases .I didn't use elevators to climb at all in the second attempt.. The rudder got me to vertical attitude. Should right rudder be forcing the nose up? Edited December 13, 2014 by vCUJOv Link to comment Share on other sites More sharing options...
vCUJOv Posted December 13, 2014 Author Share Posted December 13, 2014 Bear with me guys. Made another very short video that shows my concern better. Have a look Link to comment Share on other sites More sharing options...
Anatoli-Kagari9 Posted December 13, 2014 Share Posted December 13, 2014 (edited) Great Video! Thx for recording and sharing! My thoughts: 1) You have your axis repeated for rudder and pitch :-) ( heheh ) 2) Yo-Yo flipped the gyroscopic effects ( although at the slow pace you're applying rudder I wouldn't think those could be that noticeable... ) 3) The way the propwash is being computed, over the horizontal stab / elevator, when the aircraft transits from a sideslip into a coordinated state, and the fact that the propwash that was hiting the tail surfaces asymetrically starts to hit them more effciently might explain the pitching moment... Just imagine that due to be flying in a sideslip the propwash is not efficiently "washing" the stabilator and elevator, causing a less effective compensation of these surfaces to the pitch down moment due to lwing's lift... Then, as you use rudder to fly coordinated, the propwash starts hitting the tail surfaces more efficiently, and they start compensating more efficiently for that pitching moment due to AoA, thus pulling the nose up ( ??? ) Anyway, if that's the reason, I think something is strange there.... Could you please attach a track, starting from the initial state in your vídeo, so that I can replicate? Now I have a good reason to leave the cafeteria and rush home, switch PC on, then DCS... OMG, what a life!!! and Saturday morning is shopping time for wives..... Edited December 13, 2014 by jcomm Flight Simulation is the Virtual Materialization of a Dream... Link to comment Share on other sites More sharing options...
vCUJOv Posted December 13, 2014 Author Share Posted December 13, 2014 Great Video! Thx for recording and sharing! My thoughts: 1) You have your axis repeated for rudder and pitch :-) ( heheh ) 2) Yo-Yo flipped the gyroscopic effects ( although at the slow pace you're applying rudder I wouldn't think those could be that noticeable... ) 3) The way the propwash is being computed, over the horizontal stab / elevator, when the aircraft transits from a sideslip into a coordinated state, and the fact that the propwash that was hiting the tail surfaces asymetrically starts to hit them more effciently might explain the pitching moment... Just imagine that due to be flying in a sideslip the propwash is not efficiently "washing" the stabilator and elevator, causing a less effective compensation of these surfaces to the pitch down moment due to lwing's lift... Then, as you use rudder to fly coordinated, the propwash starts hitting the tail surfaces more efficiently, and they start compensating more efficiently for that pitching moment due to AoA, thus pulling the nose up ( ??? ) Anyway, if that's the reason, I think something is strange there.... Could you please attach a track, starting from the initial state in your vídeo, so that I can replicate? Now I have a good reason to leave the cafeteria and rush home, switch PC on, then DCS... OMG, what a life!!! and Saturday morning is shopping time for wives..... Hey jcomm and thanx for the reply. Yeah. First thing I did, I checked If I didn't have double assignments on those axis. Hehe. I only have one wife to shop for and that's hard so I can imagine what Holiday shopping must be like for you. I do my gift runs at the last min so I have plenty of time to prepare myself mentally for the mall run. Anyways here is the track. Hope you can replicate. Have fun109 Right Rudder Pitch up.trk Link to comment Share on other sites More sharing options...
ED Team Yo-Yo Posted December 13, 2014 ED Team Share Posted December 13, 2014 I disagree: the propwash seems to be not so much to be taken in account. P-factor even at prop idling and braking can cause pitch-down effect, so I could suggest that in the second case we can see the pure reaction of the plane and in the first case - the reaction with the P-factor pitching down. Anyway, these two experiments must be conducted AT THE SAME conditions, i.e. from the same initial speed, the same pitch control input, etc. THe only way to have them really controlled is to perform classical 1g level stall. Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles. Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me Link to comment Share on other sites More sharing options...
airdoc Posted December 13, 2014 Share Posted December 13, 2014 (edited) I downloaded the track you posted and took control. Indeed what you show in the video can be replicated. Applying slight right rudder at 400kmh in order to keep the ball centered while in level flight, causes an upwards pitching moment, which is reversed slowly once rudder is released. EDIT : this seems to happen even with more right rudder, forcing into a right slip with crossed left aileron to keep the wings level. I tested it with the VSI initially at 0, and after right rudder the VSI increases as the aircraft pitches up. The opposite happens with left rudder. Fuel is at 100%. Edited December 13, 2014 by airdoc The three best things in life are a good landing, a good orgasm, and a good bowel movement. The night carrier landing is one of the few opportunities in life to experience all three at the same time. Link to comment Share on other sites More sharing options...
Anatoli-Kagari9 Posted December 13, 2014 Share Posted December 13, 2014 I'm also begining to think it is related to the CoG being displaced due to the full fuel tank ( ? ) Flight Simulation is the Virtual Materialization of a Dream... Link to comment Share on other sites More sharing options...
ED Team Yo-Yo Posted December 13, 2014 ED Team Share Posted December 13, 2014 I downloaded the track you posted and took control. Indeed what you show in the video can be replicated. Applying slight right rudder at 400kmh in order to keep the ball centered while in level flight, causes an upwards pitching moment, which is reversed slowly once rudder is released. EDIT : this seems to happen even with more right rudder, forcing into a right slip with crossed left aileron to keep the wings level. I tested it with the VSI initially at 0, and after right rudder the VSI increases as the aircraft pitches up. The opposite happens with left rudder. Fuel is at 100%. The direction of the pitching corresponds to the moment of the tilted prop. Noze up - the moment to left. Noze right - the moment down. Regarding the plane CoG being extremely close to neutral stability any sneeze can change the balance. Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles. Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me Link to comment Share on other sites More sharing options...
Anatoli-Kagari9 Posted December 15, 2014 Share Posted December 15, 2014 (edited) The direction of the pitching corresponds to the moment of the tilted prop. Noze up - the moment to left. Noze right - the moment down. Regarding the plane CoG being extremely close to neutral stability any sneeze can change the balance. Yo-Yo, I think I finally understood your reasoning, and it makes sense, and if indeed teh equilibrium is so sensible, it explains the pitch up when slowly aplying right rudder!!! When we're flying level, but the ball is displaced to the right, asking for right foot, it means we're sidesliping so, looking at the prop disk it's as if we were flying pitched up, but with our plane rotated 90º CW, so, the upper sector of the prop is actually at a higher AoA to the relative wind than the lower sector, and ths pushing the aircraft nose down. Since we trimmed, or are using the stick, to fly level, the moment we coordinate and add some right rudder, the equilibrium goes away because now both the upper and the lower sectors will be at the same AoA, so, the nose pitches up, until we trim again for this new state :-) Edited December 15, 2014 by jcomm Flight Simulation is the Virtual Materialization of a Dream... Link to comment Share on other sites More sharing options...
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