Edit: I won't even bother anymore. Bottom line, there is now one flap setting that works in every situation.
Full flaps
- Thread starter Dazzler
- Start date
Edit: I won't even bother anymore. Bottom line, there is now one flap setting that works in every situation.
SpiraMirabilis
Possible Subversive
Edit: Bold word was changed, it was control, I meant stability
It may be speculation but this makes perfect sense from my teachings. We were taught in a high wing during a slip that the fuselage acts to assist directional stability for that exact reason and I watched the engineering class demonstrate it with a wind tunnel. So if you add flaps (more drag) to something that is already happening because of the drag it would fit perfectly, just my observation of course.
Would you agree it applies the same way in a skid though for improved directional stability though? The top wing in a skidding turn we know is moving fast, AOA is greater where the flap is, and total drag will be greater then it would be if we were doing the same maneuver w/o flaps. So the drag differential should be even greater IMO, but without doing the formulas who knows.
First, I agree the books wording is completely wrong and would leave any reader with many faulty concepts. That being said, there is some truth in what is said if you view the circumstances differently.
They feel gusts and when the wind hits the aircraft from the side the fuselage protects the downwind wing in a high wing aircraft. This could be compared to a small boat downstream from a large boat going across a river. The small boat would feel little to no current because of the large boat blocking it, you can see this in any boat going across a stream if you look at the water on the downstream side it is calmer then that on the upstream side.
If you assume wings level (which is likely what they are referring to since they discuss crabbing and slipping later), flying runway heading, and a 90 degree cross wind say 15G25. Now take the book comment and add fuselage too it and it would just about make sense. "In a crosswind, the “flapped” wing on the upwind side is more affected than the downwind wing" because the fuselage...
That would make this statement, "eliminated to a slight extent in the crabbed approach since the airplane is more nearly aligned with the wind" with the addition of fuselage to the above statement.
The point is the ideas in the AFH are not totally wrong, what is practically happening is, to some extent, true. But they completely screwed up their explanation of it and I believe their wording almost scares first time students away from using flaps in a crosswind.
That being said I landed our 152s in 30G38 90 degree X-wind full flaps and our 172 the same day with 40 degrees, both to full stall and both without incident. So for anyone saying full flaps in a X-wind just can't happen, I must argue the contrary as I have done it many times and in my 500 hours in the new england and NJ area (both very windy areas especially in fall) I may have 100 total landings with less than full flaps.
On a last note:
Flaps = stability and a slower stalling speed
IMO the problem is people not learning to full stall land. If you crab it and fly it to the flare, keeping it crabbed, while u bleed off the last of your speed and at the last second before full stall you stomp the rudder to align with the runway you will nail any crosswind under 40 knots that I have ever been in. There is no need for slip if you full stall the damn plane can't fly anymore so the wind won't "pick up your wing" which is where this idea of sleep came in anyway.
Can a tricycle gear a/c even be flipped over by a cross wind if landed nearly stalled in the fashion I described, does anyone have any real world experience seeing this?
tgrayson
New Member
The section wasn't discussing gusts.
Not really. When the aircraft is crabbed, the velocity vector is pointed into the wind just enough so that the component of velocity in the wind direction exactly cancels it out. The aircraft is not in any sideslip, since none is needed, and the fuselage does not shield either flap, because the relataive wind is straight off the nose.
I forgot to unsubscribe to this effing thread, and am still getting notifications for it. So I decided to go to your website and look at a few things. It's amazing how you can put a keyboard infront of someone and they become an instant expert on any subject. You keep quoting how great this cessna test pilot guy is, and you even have a paragraph on your website from him. So I decided to copy/paste some stuff here whit a question.
"The following paragraph is copied from the book "Cessna, Wings for the World" written by William D. Thompson, an Engineering Test Pilot and later Manager of Flight Test and Aerodynamics at the Cessna Aircraft Co.
With the advent of the large slotted flaps in the C-170, C-180, and C-172 we encountered a nose down pitch in forward slips with the wing flaps deflected. In some cases it was severe enough to lift the pilot against his seat belt if he was slow in checking the motion. For this reason a caution note was placed in most of the owner's manuals under "Landings" reading "Slips should be avoided with flap settings greater than 30° due to a downward pitch encountered under certain combinations of airspeed, side-slip angle, and center of gravity loadings". Since wing-low drift correction in cross-wind landings is normally performed with a minimum flap setting (for better rudder control) this limitation did not apply to that maneuver. The cause of the pitching motion is the transition of a strong wing downwash over the tail in straight flight to a lessened downwash angle over part of the horizontal tail caused by the influence of a relative "upwash increment" from the upturned aileron in slipping flight. Although not stated in the owner's manuals, we privately encouraged flight instructors to explore these effects at high altitude, and to pass on the information to their students.
This phenomenon was elusive and sometimes hard to duplicate, but it was thought that a pilot should be aware of its existence and know how to counter-act it if it occurs close to the ground. When the larger dorsal fin was adopted in the 1972 C-172L, this side-slip pitch phenomenon was eliminated, but the cautionary placard was retained. In the higher-powered C-172P and C-R172 the placard was applicable to a mild pitch "pumping" motion resulting from flap outboard-end vortex impingement on the horizontal tail at some combinations of side-slip angle, power, and airspeed. "
This is comming directly from a Cessna Engineering Test Pilot and later Manager of Flight Test and Aerodynamics. If he is wrong, then we are all in trouble!
Another copy/paste
Anti-Flap response: In strong winds, gusty winds, or even moderate crosswinds, flaps will "catch" the wind and make the airplane more difficult to control. Response The truth is that an aircraft already has a device that "catches" the wind: the wing itself. The flap only increases the camber of the existing wing, reducing the stall speed and increasing drag to some degree. Neither of these things increases the vulnerability of the aircraft to wind gusts
I have to disagree.For starters, slow airspeed = sloppy controls. This is why we teach slowflight. 2nd... When learning multiengine aerodynamics, IIRC, the flaps have a stabalizing effect during SE ops, because they will help directional stability. They make the airplane want to fly striaght ahead, and have a "keel" or "parachute" affect. There is a reason why when certifying a multi engine airplane that one of the Vmc test stipulations has a "flaps up gear up" requirement. What I am getting at is it helps in "weather vaning" the airplane. I understand that I have brought up a whole different set of circumstances, but remove the multi engine wording from the above statements, fact is that the flaps sitll provide the same weathervaneing affect on ANY AIRPLANE. Your argument for "carrying a trickle of power" holds no merrit. What are you going to do when the engine has quit, and you have no "trickle of power" to carry? Furthermore, you will be able to retain more control authority with more airspeed and not have to carry power. Again, you argue to "touch down at the slowest possible speed." You are 100% right, touch down at a stall . If you have a 15kt headwind, and you land at 45 kts, with flaps at zero, you have a 30 kt forward speed when the airplane touched down. When you have 0 head wind, and use full flaps and touch down at 30 kts, your are still touching down at 30 kts.
One last note. I think you are takeing the FAA books out of context. The are written in a somewhat abstract way. But they are not incorrect. Manytimes, it takes reading the paragraph, thinking about it, then reading it again to comprehend what they are trying to explain. The way I read them, many of their key points sound much like yours. Yours just go into more detail than the average person comprehends.
This phenomenon was elusive and sometimes hard to duplicate, but it was thought that a pilot should be aware of its existence and know how to counter-act it if it occurs close to the ground. When the larger dorsal fin was adopted in the 1972 C-172L, this side-slip pitch phenomenon was eliminated, but the cautionary placard was retained. In the higher-powered C-172P and C-R172 the placard was applicable to a mild pitch "pumping" motion resulting from flap outboard-end vortex impingement on the horizontal tail at some combinations of side-slip angle, power, and airspeed. "
This is comming directly from a Cessna Engineering Test Pilot and later Manager of Flight Test and Aerodynamics. If he is wrong, then we are all in trouble!
Another copy/paste
Anti-Flap response: In strong winds, gusty winds, or even moderate crosswinds, flaps will "catch" the wind and make the airplane more difficult to control. Response The truth is that an aircraft already has a device that "catches" the wind: the wing itself. The flap only increases the camber of the existing wing, reducing the stall speed and increasing drag to some degree. Neither of these things increases the vulnerability of the aircraft to wind gusts
I have to disagree.For starters, slow airspeed = sloppy controls. This is why we teach slowflight. 2nd... When learning multiengine aerodynamics, IIRC, the flaps have a stabalizing effect during SE ops, because they will help directional stability. They make the airplane want to fly striaght ahead, and have a "keel" or "parachute" affect. There is a reason why when certifying a multi engine airplane that one of the Vmc test stipulations has a "flaps up gear up" requirement. What I am getting at is it helps in "weather vaning" the airplane. I understand that I have brought up a whole different set of circumstances, but remove the multi engine wording from the above statements, fact is that the flaps sitll provide the same weathervaneing affect on ANY AIRPLANE. Your argument for "carrying a trickle of power" holds no merrit. What are you going to do when the engine has quit, and you have no "trickle of power" to carry? Furthermore, you will be able to retain more control authority with more airspeed and not have to carry power. Again, you argue to "touch down at the slowest possible speed." You are 100% right, touch down at a stall . If you have a 15kt headwind, and you land at 45 kts, with flaps at zero, you have a 30 kt forward speed when the airplane touched down. When you have 0 head wind, and use full flaps and touch down at 30 kts, your are still touching down at 30 kts.
One last note. I think you are takeing the FAA books out of context. The are written in a somewhat abstract way. But they are not incorrect. Manytimes, it takes reading the paragraph, thinking about it, then reading it again to comprehend what they are trying to explain. The way I read them, many of their key points sound much like yours. Yours just go into more detail than the average person comprehends.
African_Swallow
Well-Known Member
tgrayson
New Member
That's a real smart-ass remark. Lose the churlish attitude and you might actually learn something.
FWIW, I went out and tried your method of full flaps no matter what at WJF on a day with 18G26 about 30 deg. of center line and it was very difficult to control when the gusts were kicking up, then I tried with 10 deg of flaps, and it was much eaiser to land, and it was also eaiser to keep red/white the whole way down w/out carrying any power. Then we came back to SZP, and I tired raising the flaps from various positions in the pattern with various flap settings and sim engine failure, AND NEVER MADE IT TO THE RUNWAY. The resultant sink trying to keep best glide speed just woulden't let it be. I also tried the same thing with flaps left alone, and made it to the runway about 90% of the time. The only times I didn't make it, and had to add power was when I let my speed get to slow.
WTG bud. Keep teaching your students how to kill themselvs:clap:. You may understand aerodynamics better (although thats debateable), but I am not sure you understand them well when they are put into practice.
WTG bud. Keep teaching your students how to kill themselvs:clap:. You may understand aerodynamics better (although thats debateable), but I am not sure you understand them well when they are put into practice.
wjmiller3
Well-Known Member
Full flaps, but when you lower them pitch nose down and slightly increase power, that will keep your airspeed where it was for the 20 degree position. You can do this from 10 to 20 as well as long as your under the Vfe for 20 of course.
Try that and you might have a different finding, most people can't land cross wind max performance (full flaps/full stall) because they are to scared to let go of the airplane and/or push the nose down when they are under 1000' feet.
I am not saying you, just students in general, and when a gust hits you must push nose forward slightly as well. Gust = AOA increases so you must lower it again, same as flap extension idea. Good luck!
Correct me if I'm wrong, but if the engine quits, and you have no power to add, won't you land short of the runway? Come out to SZP or WHP and look at what happens if you come up short (houses/power lines at WHP or power lines/trees at SZP)
This is not as necessary as getting the plane on the ground safe. I agree a full stall landing is usually the best thing to do. But when it blows at WJF, and your 5 feet off the ground and the wind suddenly gusts and puts you in a 15-20 deg. bank 3 kts from stall, you will bend metal. If you try to pick up the wing with aileron, you will stall that wing (increase in AoA). If you try to do it with rudder, the airplane will be all over the place and side load like crazy, if you manage to get the wing up in time.
elaborate. I thought AoA had nothing to do with speed and everything to do with chordline vs Relative wind???Excerpt from the PHAK:
"Actually, an aircraft could not continue to travel in level flight at a constant altitude and maintain the same AOA if the velocity is increased. The lift would increase and the aircraft would climb as a result of the increased lift force. Therefore, to maintain the lift and weight forces in balance, and to keep the aircraft straight and level (not accelerating upward) in a state of equilibrium, as velocity is increased, lift must be decreased. This is normally accomplished by reducing the AOA by lowering the nose. Conversely, as the aircraft is slowed, the decreasing velocity requires increasing the AOA to maintain lift sufficient to maintain flight. There is, of course, a limit to how far the AOA can be increased, if a stall is to be avoided."
I think I understand what your saying, just not sure if it's worded right.
tgrayson
New Member
If you are in a glide with 20 degree flaps, raise the flaps and increase the AoA. You won't get any sink rate. I have no idea what you mean about diving to achieve best glide.
Your inability to put into practice something you don't really understand and don't want to work doesn't really surprise me. You have about the most negative attitude of anyone that I've seen on this board.
SpiraMirabilis
Possible Subversive
With full flaps you still have enough rudder authority for almost any realistic wind situation.
Sorry I missed the part where you guys mentioned engine out, my bad. What I said will still work, you just will suffer an increased sink rate, the engine power was to keep the sink rate constant. Just to note, about 200 RPM is needed for each notch of flaps and about 2-3 degrees nose down to keep descent and airspeed constant. You will likely need 5-6 degrees nose down for each notch without engine power. (Numbers are guestimate not exact and in practice vary widely from as lower flap settings cause more lift than drag and so forth.)
If you still mean engine out then sure I understand landing a little faster since you don't have a backup if you are at full stall and get hit with a gust. That being said, on a gusty day if this situation happens to you a swift nose forward on the controls (remember just above stall your nose is probably 20 degrees nose up in ground effect) to level with the horizon a good quick shot of power with your coordinated aileron and rudder controls will solve this problem every time. You lower the AOA of the wing with the elevator, control the descent with the shot of power, and increase the AOA of the downwind aileron to lift it back up with coordinated rudder you will have no issues with stall.
Test this in the air a few times till you believe it is true. Climb 50-60 degrees nose up till you have almost no elevator authority (or till stall speed) then push full forward and while the nose is dropping. When this is happening use the ailerons and you will see even though your speed is below stall you have aileron control and will not stall the wing. You try it with such a high nose up attitude so that you can see even with extreme pitch angles you can prevent wing stalls from aileron use simply by applying forward pressure.
It depends on the direction the gust of wind comes from as this new gust would have to have its vector force introduced into the current relative wind. You probably have noticed sometimes you get a gust and it only raises the wing or nose a degree or so, then on that exact same approach another gust raises the wing or nose significantly. The reason for the difference is likely not the speed since the two gust differences would more than likely be within 5 knots of each other. All that is left is AOA to increase lift so drastically and since the gust could be combined with a thermal or other form of upward flowing air (a common characteristic of gusty unstable days) then it would certainly increase AOA by changing the relative wind. Does this make sense?
The bold statement is wrong, AOA, not lift must be decreased. Lift must remain the same to keep the cosmic balance between lift and weight in check. In 1g flight lift will always be equal to weight, consider this as something you can feel by the seat of your pants.
To keep lift equal to weight lift must be controlled, there are only 2 practical ways to control lift since the lift formula includes: AOA, wing area, air density, and velocity(speed). The wing area and air density will remain relatively constant throughout flight so we can ignore them and give lift a practical formula of lift = speed + AOA, it won't work with numbers but it is adequate for theoretical application.
Now you can apply any lift change, this would be any resulting bank or any nose up or down attitude must be due to some change in speed or AOA. Since AOA is controlled by chord line and RW and the chord line isn't changing unless you are changing the flaps, then a sudden lift increase without a gust must be due to an AOA increase. Since elevator controls AOA we can change this, in other words if you hit a thermal and feel your ass stick to the seat push the control forward to lower AOA till you feel 1G again and guess what! You just balanced lift and weight all by yourself, who needs stable airplanes now
P.S. You two bickering and sniping is getting old, it doesn't matter who started it your both professionals, can't we keep it private?
flyguy07130
New Member
Well at busy airports there often is a lot of traffic closely behind you so getting off the runway quickly would be in my best interest!
The problem is they fly the glide slope or relatively close to it. Get in close at near cruise speed on glide slope then about 1/2 - 1/4 mile out from my aim point, I idle the engine and start bringing in the flaps till full extension and make a beautiful full stall landing (or a wobbly one if it's a tail dragger). This is a busy airport landing procedure for me.
For normal landings I typically teach engine to 1300/1400 rpm at the numbers (used to be 15 but the pattern was too wide) and do flap extensions 10/20/30 on downwind/base/final respectively and I lower the nose with each new flap input to maintain 60-65. Keep it in tight, it will look high, especially on final but your descent angle is much greater than on a glide slope (with 1600 rpm and 10 degrees), and point the nose down fly it to the numbers at 60-65 knots full flaps. If you perform it right you should be on final at your approach speed with the nose pointed right at the numbers, using slight throttle inputs to keep the nose pointed there and you will flare on the numbers. (Aircraft: 172P)
ppragman
FLIPY FLAPS!
Only having read the first page of this, I'll voice my opinion.
I tend to think that every landing should be treated as a short and soft field landing just so you can stay in practice, and because its easier on the equipment. So I'm an advocate of bringing it in fairly slow, and touching down gently and holding the nose off for aerobraking purposes (only in smaller airplanes, in the hondo, put the nose on the ground and then go into beta, etc.). The problem is, with a single engine airplane, chances are, on every landing there is going to be a point where you can't make the runway no matter what you do with the flaps, or how fast you lower the nose, so bickering about when to through the flaps in to make the runway seems irrellevant to me, unless your landing strategy is to touch down halfway down the runway at Vglide + 10. Every approach would be a power off 180 for you to constantly be in a gliding position.
I put flaps in on final, at about 400AGL, that leaves me the last 400' to be stabilized, and verify I'm on speed, and I stay roughly within gliding distance until I dump that last notch, which could easily be brought out, that being said, every situation is different, and there are times when unstabilizing and coming in clean then milking the flaps in the last couple hundred feet might be the only way to safely get in if there is terrible turbulence or something. It's all variable for me.
I tend to think that every landing should be treated as a short and soft field landing just so you can stay in practice, and because its easier on the equipment. So I'm an advocate of bringing it in fairly slow, and touching down gently and holding the nose off for aerobraking purposes (only in smaller airplanes, in the hondo, put the nose on the ground and then go into beta, etc.). The problem is, with a single engine airplane, chances are, on every landing there is going to be a point where you can't make the runway no matter what you do with the flaps, or how fast you lower the nose, so bickering about when to through the flaps in to make the runway seems irrellevant to me, unless your landing strategy is to touch down halfway down the runway at Vglide + 10. Every approach would be a power off 180 for you to constantly be in a gliding position.
I put flaps in on final, at about 400AGL, that leaves me the last 400' to be stabilized, and verify I'm on speed, and I stay roughly within gliding distance until I dump that last notch, which could easily be brought out, that being said, every situation is different, and there are times when unstabilizing and coming in clean then milking the flaps in the last couple hundred feet might be the only way to safely get in if there is terrible turbulence or something. It's all variable for me.
Who said anything about diving to maintain best glide speed. I said I was trying to maintain best glide, which just happens to also be approach speed with flaps. I tried for over an hour to use your method, and it never worked. I did everything I could think of (I was solo in the airplane, no student), and never made it work. You want to take the ADM out of flying an airplane by insisting that you must always land with full flaps, which is entirely unnecessary. After consulting every other CFI I work with, at wo different schools, I just can't find one of them that agree with raising flaps on an engine failure. Carrying power to touch down in a SE airplane is inviting disaster. I was on a x-country (when I was a student mind you, quite a while, and a few hours ago) to El Paso Tx, and landed in 35gG45 (IIRC) in a 172 where I had to use full rudder to maintain centerline, and just barely kept it over the runway. I used -0- flaps because the amount of rudder would have never allowed me to have -0- drift upon touchdown. At a full stall landing, I would have been blown off the runway. And I would have hated to try to re-configure the airplane on the runway while rolling out when it was a task just to maintain control of the airplane in those conditions.
I have included two videos of WHP and SZP for you to look at and see why carrying power to landing at both places would be deadly if you were carrying power to land, then the engine quits and you retract the flaps. Pulling when the engine goes quite is the WRONG thing to do, no matter how you want to argue it. You have been the only person I have ever come across that argues the point to increase your pitch when you are low and slow.
http://www.youtube.com/watch?v=HtJCtJtZzXM&feature=related
http://www.youtube.com/watch?v=SOUl0EVVSlQ&feature=related
I'd like to see a video of you "simulating" an engine faliure, being at the proper approach speed (65kts for a 172) and raising the flaps, just to prove to me that it actually works. Do it on final, about 1/2 to 3/4 mile. Mabey I am doing something wrong with your method?
ppragman
FLIPY FLAPS!
I completely agree, the airplane wouldn't be certified or popular if it wasn't flexible enough to go into short places with high x-winds. To be honest, a lot of cessna products seem to land better with full flaps IMO in a gusty condition with the crab-kick method than with the wing low method and low flaps settings.
Most I had in the 207 was a 40kt direct cross and full flaps seemed a lot more comfortable than coming in in a wicked slip.
ppragman
FLIPY FLAPS!
If you have a mile of runway to work with, then yes, play it safe, however, if you have to get down and stopped in less than about 1500' with a full load, then I'd recommend a different tactic, drag it in with power and flaps and touch down at stall. It's risk mitigation, what's more likely, running off the end of the runway because you came in too fast, or losing an engine on short final and smacking the trees? Obviously the overrun.