round_peg Posted October 10, 2012 Report Share Posted October 10, 2012 Beaten to death and beyond, I know. But I don't think I've seen an answer to this question. After a year-plus of almost nothing but 15° flap landings, we had a relatively calm day so I thought I'd try a few at 30°. The wind was around 5-10 knots with light gusts, off the centerline to the right about 10-20°. The approach was fine, added the second notch of flaps on short final. Nose dropped along with the airspeed. Round out, flair, touchdown on the centerline holding in a bit of power. Immediately on rollout I noted a tendency for the airplane to want to drift towards the left. Wind conditions were calmer than is typical here; the only difference was the flap setting. The right main might have come off the pavement slightly, but I'm not sure. Any thoughts? Link to comment Share on other sites More sharing options...
Tad Olmsted Posted October 10, 2012 Report Share Posted October 10, 2012 What position were you holding your tongue :-) Link to comment Share on other sites More sharing options...
coppercity Posted October 10, 2012 Report Share Posted October 10, 2012 Even in light crosswinds you really have to continue to increase the aileron input into the wind on rollout especially when using higher flap settings. This will help reduce drift until the wheels have a firm grasp on the pavement. Link to comment Share on other sites More sharing options...
Tom Baker Posted October 10, 2012 Report Share Posted October 10, 2012 Even in light crosswinds you really have to continue to increase the aileron input into the wind on rollout especially when using higher flap settings. This will help reduce drift until the wheels have a firm grasp on the pavement. The problem with higher flap settings and crosswinds is when our flaps go down so does the aileron. When you put in a crosswind correction the aileron on the downwind wing creates more drag than the trailing aileron on the upwind wing. This makes the airplane want to turn the wrong dirrection. The higher the flap setting the bigger the differential. I had a model airplane once that had flaperons that was mixed to the elevator. When you gave up elevator the flaps went down to make loops tighter. It would do the most wonerful flat spins because with up elevator the flaps were down, and the crank in aileron one aileron was straight back from the wing while the other was down at about a 75° degree angle creating lots and lots of drag, but opposite the dirrection of aileron input. Add in rudder oposite the aileron and it would just spin like a top. Link to comment Share on other sites More sharing options...
round_peg Posted October 10, 2012 Author Report Share Posted October 10, 2012 The problem with higher flap settings and crosswinds is when our flaps go down so does the aileron. When you put in a crosswind correction the aileron on the downwind wing creates more drag than the trailing aileron on the upwind wing. This makes the airplane want to turn the wrong dirrection. The higher the flap setting the bigger the differential. So is the prescription still the same? What you are describing seems counterintuitive. Link to comment Share on other sites More sharing options...
Tom Baker Posted October 10, 2012 Report Share Posted October 10, 2012 So is the prescription still the same? What you are describing seems counterintuitive. Designing an airplane is a balancing act. The reason for the flaperons is to lower stall speed for short landings. The down side is the the effect of adverse yaw with aileron application with flaps deployed. This adverse yaw becomes greater the lower the flap setting. That increased drag on the wrong side of the airplane in a crosswind can be a real problem. That is the reason many say 0° or no more that 15° flaps for landing in a crosswind. Link to comment Share on other sites More sharing options...
josjonkers Posted October 11, 2012 Report Share Posted October 11, 2012 Beaten to death and beyond, I know. But I don't think I've seen an answer to this question. After a year-plus of almost nothing but 15° flap landings, we had a relatively calm day so I thought I'd try a few at 30°. The wind was around 5-10 knots with light gusts, off the centerline to the right about 10-20°. The approach was fine, added the second notch of flaps on short final. Nose dropped along with the airspeed. Round out, flair, touchdown on the centerline holding in a bit of power. Immediately on rollout I noted a tendency for the airplane to want to drift towards the left. Wind conditions were calmer than is typical here; the only difference was the flap setting. The right main might have come off the pavement slightly, but I'm not sure. Any thoughts? Why change your flap settings on short final when you should be established in a stable approach. I would do this much sooner to compensate and anticipate the effect of the change in flap setting so you re-establish your new glide path, attitude, powersetting and speed. Link to comment Share on other sites More sharing options...
round_peg Posted October 11, 2012 Author Report Share Posted October 11, 2012 Why change your flap settings on short final when you should be established in a stable approach. I would do this much sooner to compensate and anticipate the effect of the change in flap setting so you re-establish your new glide path, attitude, powersetting and speed. I was taught that the last notch of flaps should added on final, when the runway is assured. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted October 11, 2012 Report Share Posted October 11, 2012 I was taught that the last notch of flaps should added on final, when the runway is assured. If your "last notch" is 30 degrees and if you don't rely on the throttle then that last notch means a big nose down pitch change. This is not the case in all designs and I find that I like to get 30 degrees and the big pitch change early at TPA for a more stabilized approach. In my previous airplane that last notch had no effect on pitch so I waited till very short final. Link to comment Share on other sites More sharing options...
round_peg Posted October 12, 2012 Author Report Share Posted October 12, 2012 If your "last notch" is 30 degrees and if you don't rely on the throttle then that last notch means a big nose down pitch change. This is not the case in all designs and I find that I like to get 30 degrees and the big pitch change early at TPA for a more stabilized approach. In my previous airplane that last notch had no effect on pitch so I waited till very short final. This is true. Next time I try some 30° flap landings I will add that notch on base and see if it makes any difference. Not that I was having trouble making the pitch adjustments on final. Link to comment Share on other sites More sharing options...
FastEddieB Posted October 12, 2012 Report Share Posted October 12, 2012 I was taught that the last notch of flaps should added on final, when the runway is assured. I was taught the same thing, and it held me in good stead for 30+ years. When I trained to be a Cirrus Standardized Instructor, the manual called for full flaps on base, so I learned to teach them that way. And you know what? It works pretty well. Well enough that I now do the same in my Sky Arrow. Two points... 1) It works so well because it's one less thing to worry about and to possibly destabilize the final with a configuration change. 2) if you plan the pattern properly, there is no more danger of coming up short of the runway if the engine fails. Just keep the base a tad higher and even with full flaps gliding to the runway should never be in question. Link to comment Share on other sites More sharing options...
josjonkers Posted October 12, 2012 Report Share Posted October 12, 2012 I was taught the same thing, and it held me in good stead for 30+ years. When I trained to be a Cirrus Standardized Instructor, the manual called for full flaps on base, so I learned to teach them that way. And you know what? It works pretty well. Well enough that I now do the same in my Sky Arrow. Two points... 1) It works so well because it's one less thing to worry about and to possibly destabilize the final with a configuration change. 2) if you plan the pattern properly, there is no more danger of coming up short of the runway if the engine fails. Just keep the base a tad higher and even with full flaps gliding to the runway should never be in question. You are all missing the point. The reference was to SHORT final. Not "normal" final. I typically go to 30 after turn from base. Link to comment Share on other sites More sharing options...
round_peg Posted October 12, 2012 Author Report Share Posted October 12, 2012 You are all missing the point. The reference was to SHORT final. Not "normal" final. I typically go to 30 after turn from base. He didn't really miss the point. At my home base nobody really does a "long" final, unless they are from out of the area. We fly very tight patterns. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted October 12, 2012 Report Share Posted October 12, 2012 Back to the thread subject: directional control on roll out with full flaps. Mitch notices a tendency for the airplane to want to drift towards the left [light x-wind from the right]. I do not notice the tendency because I am actively pressuring the pedals sufficient to maintain the center line and this prevents any drifting before it starts. The alternative is to do nothing, eventually notice the drift and correct. A good point to "prevent tendencies" is abeam the numbers. At this point if you were to simultaneously close the throttle and deploy 15 degrees of flaps there are tendencies to change pitch, speed and yaw. You could wait for these tendencies do develop and then put the nose back where it was our you can with some control pressure keep the nose where it was. Link to comment Share on other sites More sharing options...
round_peg Posted October 12, 2012 Author Report Share Posted October 12, 2012 Happy to be back on topic, but just to be clear, the tendency I noticed was on rollout. The landing is right on the centerline, pointed down the runway, so all the inputs needed to compensate for the crosswind are already applied. The airplane seems to be squarely and firmly on the runway when the drift occurs. Feels like the upwind wing lifts just enough to take some weight off the right main. Obviously the solution is adding more correction, but this seems surprising given that I don't notice this with 15° of flaps, so the only difference is the flap setting. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted October 12, 2012 Report Share Posted October 12, 2012 Mitch, You are describing a left turning tendency that is dependent on full flaps and otherwise doesn't exist. This is very hard to explain, why don't you see if you can prove this. Take the landing out of the loop, taxi up to roll out speed and close the throttle. Do this with and without 30 degrees and see if you can replicate the tendency. You talk about a sense of the right wing / right gear getting light but you describe the plane as being "squarely and firmly on the runway". It takes a meaningful gust to get a wing up yet you described light winds, were there gusts? Link to comment Share on other sites More sharing options...
round_peg Posted October 12, 2012 Author Report Share Posted October 12, 2012 Mitch, You are describing a left turning tendency that is dependent on full flaps and otherwise doesn't exist. This is very hard to explain, why don't you see if you can prove this. Take the landing out of the loop, taxi up to roll out speed and close the throttle. Do this with and without 30 degrees and see if you can replicate the tendency. You talk about a sense of the right wing / right gear getting light but you describe the plane as being "squarely and firmly on the runway". It takes a meaningful gust to get a wing up yet you described light winds, were there gusts? Light gusts, as I believe I described the conditions in the opening post, and I think this was the cause. My sense is the extra flaps magnified the impact of the crosswind gusting more than I would have expected, but I am hoping to become more certain of this. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted October 12, 2012 Report Share Posted October 12, 2012 We are talking about 1 particular day and since everyday is different that may not be enough to establish that the turning tendency on rollout was due to the flap setting, in fact it is very hard to see how the two are related. Using my experience I have an explanation that might be correct. Flying out of Mammoth I get to experience a lot of turbulent winds due to venturi effect at the nearby mountain passes and the mountainous terrain that these accelerated winds contact en-route to the runway environment. The 5-10k @ 10-20 degrees would have very little effect on me unless... The California and Nevada deserts present desert conditions with their own landing issues and Mammoth and Santa Paula are both included here. One of these conditions to consider, is "light and variable". If the area is wide open enough with loose dirt to blow around you will likely see dust devils on these types of days. Convective activity near the ground . On final approach you might switch to a downwind landing and back again. If the wind gets behind your wing on rollout you might get light, fast and turned. Just a guess. Remember if the wind is from the right, the turning tendency should be to the right not left. Link to comment Share on other sites More sharing options...
round_peg Posted October 12, 2012 Author Report Share Posted October 12, 2012 Remember if the wind is from the right, the turning tendency should be to the right not left. Not sure I follow you there. That quartering crosswind from the right pushes you off the centerline to the left. We're in a coastal valley about 15 miles from the ocean, so our winds tend to be a bit gusty, but from strongly prevailing directions. On the onshore flow days 20° right crosswind is typical. When the winds blow offshore, that's an entirely different story. We face a bouncy downwind due to the proximity of a mountain and burbles on final due the proximity of hangers. Frankly not a lot of use for more than 15° flaps here in a CT, but I do feel an urge to master it. But yeah, you're right, one day is one day; it was also the first time in about a year that I'd worked up the nerve to try 30° flap landings. Most days it's too windy to even want to. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted October 12, 2012 Report Share Posted October 12, 2012 30 degrees works well in Camarillo, maybe that would be the spot to try it? Weathervane effect is what turns you right in a right crosswind. The pivot point is a main gear and the crosswind wind will escape aft of the gear as your CT has little fuselage to present to the wind. But the vertical stabilizer and rudder will get pushed to the left and with the long moment arm your nose easily goes right and everything else will follow without some left pedal. Your CT is like an arrow the tail feathers stabilize its flight and if there is wind shear the nose will point into the wind. This is one of those things that I don't want to think about with my brain but instead just use my eyes and feet to keep the picture right. The amount of rudder I need diminishes as I descend due to gradient and on the rollout the amount of left pedal I need reduces again as my nose wheel settles and the feel changes as I transfer steering from rudder to nose wheel. With all those changes I want to not overthink it. Perhaps your expectation of a left turning tendency created one? Link to comment Share on other sites More sharing options...
coppercity Posted October 12, 2012 Report Share Posted October 12, 2012 From my teaching experience in the CT, it still sounds to me like your either letting out the aileron input after touchdown, which is the most common, or your not adding more aileron as you reduce speed after touchdown. With crosswind landings the aileron input needs to increase as speed decreases to the point where you end up with full aileron into the wind by the time your down to taxi speed. Link to comment Share on other sites More sharing options...
round_peg Posted October 13, 2012 Author Report Share Posted October 13, 2012 From my teaching experience in the CT, it still sounds to me like your either letting out the aileron input after touchdown, which is the most common, or your not adding more aileron as you reduce speed after touchdown. With crosswind landings the aileron input needs to increase as speed decreases to the point where you end up with full aileron into the wind by the time your down to taxi speed. My thinking is along these lines. Add in a bit of gustiness and some wandering off the centerline seems like the likely result. Yet I wasn't experiencing this with less flaps. Link to comment Share on other sites More sharing options...
coppercity Posted October 13, 2012 Report Share Posted October 13, 2012 My thinking is along these lines. Add in a bit of gustiness and some wandering off the centerline seems like the likely result. Yet I wasn't experiencing this with less flaps. It takes significantly more aileron input with more flaps in the CT, first because your landing slower and due to the aileron droop with flaps. Next time you go out and play in those conditions just try more aileron if you feel it trying to drift. Don't try to outguess it, just fly what you see and feel and don't stop flying until you have it tied down. Link to comment Share on other sites More sharing options...
josjonkers Posted October 13, 2012 Report Share Posted October 13, 2012 He didn't really miss the point. At my home base nobody really does a "long" final, unless they are from out of the area. We fly very tight patterns. So all your finals are short finals? That doesn't make sense. I am talking about setting flaps and keep them unchanged on FINAL. I never mentioned long final. Link to comment Share on other sites More sharing options...
round_peg Posted October 13, 2012 Author Report Share Posted October 13, 2012 So all your finals are short finals? That doesn't make sense. I am talking about setting flaps and keep them unchanged on FINAL. I never mentioned long final. If the power is pulled to idle downwind abeam the numbers with a +600 AGL pattern, then yes, finals are about as short as they come. The last notch of flaps has to be added a few seconds after turning base or you aren't doing it. Link to comment Share on other sites More sharing options...
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