Gotcha on the first part. On the second (chord line of the airfoil), I’m not following. Extending the flaps should increase both the chord and the camber of the wing, right? And since flaps go down (and sometimes out), so the chord angle changes because the leading and trailing edge of the wing isn’t fixed. That chord line therefore has to change relative to the fuselage, no?
I don’t mean to hijack or nitpick, but it has been a while since I’ve talked about these things and I’m really interested.
That might be true for the standard chord line that they list on the spec sheets describing the craft, but the real physical chord line that determines how the wing actually interacts with the air will change when the flaps are deployed.
Another note is that bigger jets will have more complex flaps, slats, and leading edge extensions than smaller aircraft. This allows them to achieve much higher angles of attack without stalling, as well has having a larger speed difference between cruise and landing/takeoff.
This would explain why you notice this more with the bigger, heavier jets.
I can think of two reasons why you’d want to avoid stalling your wings during the landing flare - can someone confirm if I’m even on the right track with these ideas?
you want to maintain enough lift so you can control the aircraft and execute a go-around if you need to (you only want the wings to stop lifting once you’ve decided they should by using spoilers/thrust reversers/breaks)
IIRC wings generally stall asymmetrically; that is, one wing will stall before the other one, which tends to cause the plane to roll, something you’d like to avoid when you’re travelling at high speed 10 feet above the ground! Although on this point I’m not sure… I know wings stall asymmetrically if they’re dirty (e.g. ice buildup), but unless you have 100% perfect flying conditions, I can’t imagine anything that would force clean wings to stall at the same time if you reached the stall AOA. Wind direction alone means both wings are operating under slightly different conditions, right?
Commercial airliners have a “twist” built into the wing, so that the root operates at a higher AOA than the tip. This way, when a stall does happen, it’s gradual, starting at the root and progressing outward to the tip as the aircraft pitch increases. In this way the plane loses lift gradually instead of suddenly, and roll control (via the ailerons out near the wing tips) is maintained until the stall progresses out to the wing tips. So even though the stall may have some degree of asymmetry, the ailerons allow you to compensate for it until you’re so far into stall that the plane becomes an aero-brick.
mnemosyne is on the right track. I’ve never flown a jet, so anything I say relates only to light aircraft. On landing you want to be going as slow as possible, but still in control. That means getting near the stall speed, but definitely not actually stalling. It actually gives me slight shivers thinking about deliberately stalling an aircraft close to the ground - really not a good time to have the nose pitching down.
I think some of the confusion may arise because a good landing in a small aircraft will often set off the stall warning alarm just prior to the wheels making contact with the runway. But keep in mind that the alarm is designed to go off before an actual stall occurs, so that in flight the pilot has time to do something about it.
I’m a flight instructor, and I often have to field questions such as the one posed in the OP. Being a rather basic question, it’s actually a bit hard to answer without giving some background information. Ask something like this to an actual aerodynamicist and he will very likely wince, and start writing equations on a blackboard.
For instance, many people (including a lot of pilots) conflate “attitude” with “angle-of-attack”, when they are in fact two different things. I think the OP is asking about pitch of the plane relative to the horizon. That is, strictly speaking, attitude. To determine angle-of-attack, you need to look at chord lines and relative wind.
My answer to that is, yes, the plane is probably pitched up slightly relative to the horizon as it nears the runway.
Not everyone executes a “full-stall landing” in small planes, and you definitely don’t do that in larger planes. Tailwheel planes generally should be stalled when executing most landings. Because they have a significant angle-of-incidence (angle the wing is attached to the fuselage), they’ll start flying again if you land them too fast. In tricycle gear planes, you can get away with carrying some extra airspeed.
As you get into bigger planes, you generally fly them onto the runway rather than stalling them. I once executed a full-stall landing in a mid-sized twin, causing the instructor next to me to pucker a bit.
At a tower controlled airport, you have to maintain a set speed in the landing pattern. If the traffic is mixed, large jets and smaller regional prop jogs, etc…, everyone has to keep up a minimum speed to keep from getting overrun or vice versa. Flying my small plane in these situations often required nose down/level with the throttle still set high to maintain speed until the actual flare/landing.
I’ll quibble a bit with the “maintain a set speed” at a towered airport. There’s nothing that says I have to fly 90 knots in a Cherokee (my preferred pattern speed in that plane) while in the pattern. If I’m in Class D airspace for instance, all traffic simply has to be below 200 knots.
The tower can use speed, position and altitude to separate traffic. They’ll often ask smaller planes to “keep the speed up” to provide separation from faster traffic. Or sometimes ask faster traffic to slow down, but more commonly they’ll move slower planes out of the faster plane’s way. They can also ask for changes of heading, or require a 360 turn for spacing.
Another thing you’ll sometimes hear is the tower asking a plane to make a “short approach”. That means fly the tightest pattern practicable because someone else is fairly close behind.
A lot of times, if the pilots can identify other traffic and maintain visual separation, the tower doesn’t care much about your speed. But if you’re trying to land a Cessna 150 at JFK, it makes everyone’s life easier if you fly fast.
Tailwheel pilot here. In a three-point landing ideally you stall at the same moment you touch down. If you do so an inch or two above the ground no harm done (though you might bounce). If you don’t, if you’re going only a little faster than stall - well, you’ll still land, just roll out a little longer than otherwise. If you’re going more than just a little bit above stall you’ll either have problems getting it low enough to touch the pavement, or you greatly increase the risk of a bounce that could, if not corrected, lead to an accident.
In a tail-up landing in a taildragger, when you land on the two big wheels first, you are not in a stall. You still aren’t going much faster than one, though, because tailwheels tend to want to fly with even a little excess speed.
For Cessna type airplanes - meaning those with a nosewheel (there are tailwheel Cessnas), you can land them in a stalled condition as you do a tailwheel, that is, stalling at the point you touch down, but it is definitely not the preferred technique. Landings are usually 5-10 knots faster than stall speed (even higher under some conditions. Let’s not talk about the time that I landed a C150 at 110 mph - a student mistake that fortunately had no bad consequences)
You actually don’t need flaps - they are handy, useful, and definitely a good thing for many airplanes, but not all airplanes have them. I’ve flown about a half dozen that don’t have flaps. The Gimli Glider incident ended with landing the airliner without flaps. That said, if there are flaps I usually use them for landing.
About 30 years ago, I took some flying lessons with an eye towards getting my private pilot license. I spent my first so many hours flying a Piper Tomahawk which was a small, two-seat, low-wing, tricycle-gear aircraft. To land that plane you essentially cut power and pulled up the nose. The more you raised the nose (at reduced power, of course), the faster you dropped. When I ran out of money, I quit flying for a while.
When I had improved my financial situation a couple of years later, I decided to work on my pilot license some more. The flying school I went to that time had a Cessna 152 as its primary trainer. The Cessna was a small, two-seat, HIGH-wing, tricycle-gear aircraft. When I tried to land it the way I had learned in the Tomahawk, it would not go down AT ALL. The ONLY way to get that Cessna to land was to point its nose at the ground and fly that sucker almost into the runway, then flare up at the last second. I never could seem to get the hang of landing that plane in any way remotely resembling a smooth, controlled return to earth, so I gave up. Never did get my license. That’s one thing in my life I sometimes regret but quickly get over it when I think about trying to land that Cessna.
If I were you, I’d get back into flying when you can afford it and try and find a good, well recommended instructor. The ideas you have about the landing difference between the two types of aircraft are a little odd and probably reflect on some poor instruction. Cessnas and Pipers and pretty much everything else all fly in much the same way and you need to do much the same things to get them to do what you want. The trick is that the view out the front window isn’t always the same and you need to get used to what a normal approach looks like in the various different aircraft. So have another go, an inability to learn something isn’t a failure of the student, it’s a failure of the student/teacher combination. Find a teacher who can instruct you in a way that you understand.
On flaps and slats and angle of attack. Flaps effectively increase the angle of incidence (the angle between the chord and the fuselage) and slats decrease the angle of incidence. This corresponds to the different nose attitudes people are noticing. Slats, by the way, are flap type devices on the leading edge of the wing, while flaps are on the trailing edge.
An aircraft with no flaps or slats will have a high nose attitude on approach because the angle of attack is high, higher than the angle of descent. Aircraft with flaps will have a low nose attitude on approach. The more flap they have out, the lower the nose attitude will be. One of the advantages of flaps is that they result in a lower nose attitude in slow flight which improves visibility. An aircraft with slats only (not common) will have an even higher nose attitude than if the slats were not deployed. Aircraft with both flaps and slats deployed will have varying nose attitudes depending on the specific make-up of the flaps and slats.
Small single engine aircraft normally only have flaps, so they’ll have a low nose on approach. Twin turbo props also typically only have flaps so they will also have a low nose attitude depending on how much flap is deployed. Jets tend to have both flaps and slats and so the nose attitude is often high when compared to non-jets.
This varies between types. Some taildraggers sit fairly flat on the ground and will easily land tailwheel first if landed too slow. This can be desirable if not overdone as it means the angle of attack reduces when the main wheels touchdown and you’re less likely to bounce.
nmemosyne, a big reason not to land stalled is that in larger aircraft you run the risk of striking the tail on the ground which can cause lots of expensive damage. Most larger aircraft will have a pitch limit in the landing flare. As an example, the Dash 8 300 is limited to 6 degrees nose up at touchdown. This is not very much and it is very easy to exceed it using a light plane landing technique.
There are plenty of other reasons to “fly” the aircraft on to the ground rather than "stalling"on (in quotes because you don’t really stall it on, you just get close to the stall.)
In terms of big aeroplanes the goal in landing is to land at the certified speed and within the touchdown zone on the runway. Do this and you’ll get the certified landing performance. Achieving a nice gentle landing, although pleasing to passengers, is a secondary consideration. A smooth touchdown is useless if you’ve floated halfway down the runway trying to do it, and the brakes can’t start working until you’re on the ground.
If I were you, I’d get back into flying when you can afford it and try and find a good, well recommended instructor. The ideas you have about the landing difference between the two types of aircraft are a little odd and probably reflect on some poor instruction. Cessnas and Pipers and pretty much everything else all fly in much the same way and you need to do much the same things to get them to do what you want. The trick is that the view out the front window isn’t always the same and you need to get used to what a normal approach looks like in the various different aircraft. So have another go, an inability to learn something isn’t a failure of the student, it’s a failure of the student/teacher combination. Find a teacher who can instruct you in a way that you understand.
On flaps and slats and angle of attack. Flaps effectively increase the angle of incidence (the angle between the chord and the fuselage) and slats decrease the angle of incidence. This corresponds to the different nose attitudes people are noticing. Slats, by the way, are flap type devices on the leading edge of the wing, while flaps are on the trailing edge.
An aircraft with no flaps or slats will have a high nose attitude on approach because the angle of attack is high, higher than the angle of descent. Aircraft with flaps will have a low nose attitude on approach. The more flap they have out, the lower the nose attitude will be. One of the advantages of flaps is that they result in a lower nose attitude in slow flight which improves visibility. An aircraft with slats only (not common) will have an even higher nose attitude than if the slats were not deployed. Aircraft with both flaps and slats deployed will have varying nose attitudes depending on the specific make-up of the flaps and slats.
Small single engine aircraft normally only have flaps, so they’ll have a low nose on approach. Twin turbo props also typically only have flaps so they will also have a low nose attitude depending on how much flap is deployed. Jets tend to have both flaps and slats and so the nose attitude is often high when compared to non-jets.
This varies between types. Some taildraggers sit fairly flat on the ground and will easily land tailwheel first if landed too slow. This can be desirable if not overdone as it means the angle of attack reduces when the main wheels touchdown and you’re less likely to bounce.
nmemosyne, a big reason not to land stalled is that in larger aircraft you run the risk of striking the tail on the ground which can cause lots of expensive damage. Most larger aircraft will have a pitch limit in the landing flare. As an example, the Dash 8 300 is limited to 6 degrees nose up at touchdown. This is not very much and it is very easy to exceed it using a light plane landing technique.
There are plenty of other reasons to “fly” the aircraft on to the ground rather than "stalling"on (in quotes because you don’t really stall it on, you just get close to the stall.)
In terms of big aeroplanes the goal in landing is to land at the certified speed and within the touchdown zone on the runway. Do this and you’ll get the certified landing performance. Achieving a nice gentle landing, although pleasing to passengers, is a secondary consideration. A smooth touchdown is useless if you’ve floated halfway down the runway trying to do it, and the brakes can’t start working until you’re on the ground.