Why stall it?

flyingron said:
Agreed, but this has nothing to do with "stall."
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Kinetic energy is proportional to the square of velocity. I think Eddie's point is that if you're landing at a speed faster than stall, you're carrying more kinetic energy than you have to. If something goes wrong, it will go wrong with more energy needing to be dissipated, hence more damage.
 
Half Fast said:
Kinetic energy is proportional to the square of velocity. I think Eddie's point is that if you're landing at a speed faster than stall, you're carrying more kinetic energy than you have to. If something goes wrong, it will go wrong with more energy needing to be dissipated, hence more damage.
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No, the point is that if you're well above stall, you can start flying again when you don't want to.
 
Kritchlow said:
PS- the Bus laws in flair eff with you. I hate it. It changes at 50 feet.
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I know what you mean. Dassault does a good job of making the plane feel like a "pitch airplane" at 50 feet
 
I remember reading a chapter on this in a book I picked up before I even started flight training:
The Thinking Pilot's Flight Manual

I should probably go back and read that now that I've actually got flying experience, it might make more sense. It was a chapter called The Last 10 Feet. The author has to do a pre 709 check-out for a guy who had an incident. Boils down to the guy like many was carrying too much energy into his landings.
 
Maybe this helps some for the OP.

When I learned to fly the instructor said we were shooting to land close to a full stall, but the real goal as I learned it more thoroughly later on, was to land without enough energy remaining to fly again.

That's harder to communicate to a new student, so it gets shortened to "try to land right at full stall" mostly out of communications laziness and necessity.

One of the techniques to "prove" you landed slow enough is also generally a best practice anyway...

Keep the elevator moving aft after touchdown all the way to the up stop. If you landed with too much energy the airplane will come back off the runway, or you'll roll along on the mains for a very long time.

Which is also good practice for the other thing. Keep the ailerons moving into the wind all the way to the aileron stop too. The adverse yaw actually works in your favor as an additional "rudder" input when you do that, too.

Interestingly as the aircraft get bigger, you might not want to, say, start a takeoff roll from a dead stop with the ailerons locked over hard like you might do in a small single in a crosswind. The adverse yaw may be too strong with large enough ailerons.

The Seminole will actually lean hard into the main gear on the aileron deflected side and the adverse yaw will overcome the nose wheel before you can use rudder effectively and not create a steering problem for yourself.

If you're really good you can tweak a tiny amount more power up on the downwind engine, but I'm not that good. I'll chase ass all over the runway if I start that dance game. Haha. Takes finesse that I'll probably not get to before I'm done flying the thing and back to slumming it in single banger. (I'm hearing shades of Benevolent Dictator Ted in that last comment. Flying twins is kinda addictive...)
 
And just because the airplane is on the ground doesn't mean the flight's over. Any time there is airflow across the wings, lift is being generated. There just isn't enough to lift the airplane off the ground, but there will be enough to reduce traction, and if a good crosswind gust comes along, the airplane can easily go its own way. Can't relax after touchdown, even in a trike.
 
I've made a couple fully stalled landings, they weren't pretty. :)
 
Here's my thought experiment...

Let's say you knew beforehand that on the very next landing, you were going to t-bone a deer. Or an axle was going to break. Or whatever. Would you not want to be at the lowest possible speed when it happened?

Follow up question: how do you know that one of those things won't happen on your next landing?

So why not land as slowly as you can, just in case?

As homework, maybe someone could compute the kinetic energy of a given plane at 50k, then again do it for 55k. How much does the energy increase percentage-wise?
 
FastEddieB said:
Here's my thought experiment...

Let's say you knew beforehand that on the very next landing, you were going to t-bone a deer. Or an axle was going to break. Or whatever. Would you not want to be at the lowest possible speed when it happened?

Follow up question: how do you know that one of those things won't happen on your next landing?
So why not land as slowly as you can, just in case?
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You pretty much never want to stall an airplane airborne (other than training), so why do it on landing? I agree with working the speed down but personally, I just don't want to stall it and hope I've judged my height above runway exactly right. The airplane gets less and less controllable as it nears stall. I would rather preserve some of that controllability to ease it onto the runway. I'll take the chance that the extra few knots that aid responsiveness won't be the difference in life or death in the event a deer runs out.
 
Let me just say that I doubt that "full stall" landings are really fully stalled.

Maybe ground effect gets in the way.

Again, my goal is the stick/yoke all the way back, whether that's really stalled or not. Few pilots manage that consistently in real life, landing much faster than they have to. That's my real point.
 
I learned many years ago in an aeronca champ, some in a super cruiser. The instructor, a WW2 Stearman instructor,( how many hundreds do you suppose he Taught!?) and later a jug pilot, taught this way. Coming in , you chopped the throttle just past the fence and he would have already clued you to keep the nose a little high and try to be three feet or so above the runway. ( 2200 feet of grass, good approaches) Then he would keep saying....." Dont let it land,keep coming back on the stick " repeating this several times until we touched down in a three point. I caught on to this pretty quick and could land in a three point without much trouble sometimes as the plane touched, more often just a bit above the runway, ( six inches maybe) he explained that one wanted the airplane to STOP FLYING as one flared and touched down. That meant a stall to me and still does. I spent a lot of hours in that aeronca , over a hundred and in the super cruiser. Later I landed a mooney pretty much the same way, a Stearman, , a shrike, taylorcraft, etc. in the Stearman you wanted to be thru flying on touch down as until you were very adept in one, you could wind up anywhere. There was no AOA in many of these aircraft and I never used one anyway. You simply " knew" the right angle and your purifieral ( spelling!) vision did the rest. Simply practice. Over and over. Monkey and the typewriter stuff. Rote.
 
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FastEddieB said:
Let me just say that I doubt that "full stall" landings are really fully stalled.

Maybe ground effect gets in the way.

Again, my goal is the stick/yoke all the way back, whether that's really stalled or not. Few pilots manage that consistently in real life, landing much faster than they have to. That's my real point.
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I agree 100 percent. When it drops a few inches onto the runway ,its. done flying.
 
FastEddieB said:
Thanks.

That "just 5 knots over" results in 21% more energy to dissipate.

That could turn a no injury incident into minor injuries; minor injuries into major, and major into fatal.

Just food for thought.
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So a 10% increase in speed (55 instead of 50) is 21%. That's the square of the increase in speed. A 20% increase (60 instead of 50) would involve 44% more energy. It gets bad real fast.

Kinetic energy is 1/2 of mass times velocity squared. IIRC.
 
FastEddieB said:
Here's my thought experiment...

Let's say you knew beforehand that on the very next landing, you were going to t-bone a deer. Or an axle was going to break. Or whatever. Would you not want to be at the lowest possible speed when it happened?

Follow up question: how do you know that one of those things won't happen on your next landing?

So why not land as slowly as you can, just in case?

As homework, maybe someone could compute the kinetic energy of a given plane at 50k, then again do it for 55k. How much does the energy increase percentage-wise?
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This is why a very old timer told me anyone doing wheels landing in a taildragger is just showing off.
 
You stall a canard before landing and you've got yourself a collapsed nose gear. :(
 
Depends on the plane. The Bonanza I land with the stall horn chirping and it is a soft touchdown. The Comanche I fly onto the runway. You only 'wheelbarrow' if you hit nosegear first with excessive speed. You don't if the plane is almost done flying and you touch mains first.
 
Dan Thomas said:
So a 10% increase in speed (55 instead of 50) is 21%. That's the square of the increase in speed. A 20% increase (60 instead of 50) would involve 44% more energy. It gets bad real fast.

Kinetic energy is 1/2 of mass times velocity squared. IIRC.
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Yep. Actually, just to be clear, a 10% increase means the speed is 1.1 times greater. 1.1 squared is 1.21. That's where the 21% comes from.
 
azure said:
Yep. Actually, just to be clear, a 10% increase means the speed is 1.1 times greater. 1.1 squared is 1.21. That's where the 21% comes from.
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For those really math impaired/phobic like myself, you get that 1.1 by dividing the lower speed into the higher. Then drop the 1 and express the .1 as a percentage (10%)

Or, take that 1.1 and square it to get the 1.21. Drop the 1 and express it as a percentage (21%).

This is probably absurdly obvious to the engineering types, but for some of us it has to be broken down.

I may try to work up a simple Excel spreadsheet later and post it here. Unless somebody beats me to it.

As an aside, a Cirrus SR22 can be landed at about 60 kias. I've seen reports of people landing at 80 kias. The resulting number there really drives the point home, I think.
 
FastEddieB said:
Let me just say that I doubt that "full stall" landings are really fully stalled.
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That is true.
Maybe ground effect gets in the way.
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Ground effect has nothing to do with it. Stall is determined by angle of attack. PERIOD. Not airspeed, not kinetic energy, not ground effect.
Unless you've got some bizarre wind where the relative wind is blowing UPWARDS from the ground, there is no way an airplane with the mains on the ground (or nearly there) is likely to be stalled.[/QUOTE][/QUOTE]
 
flyingron said:
Ground effect has nothing to do with it. Stall is determined by angle of attack. PERIOD.
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[/QUOTE][/QUOTE]

Well, sorta......

You're correct in free air, but in ground effect things get a little more complex.

Stall occurs at an angle of attack that results in separated air flow becoming dominant over attached flow, such that lift will diminish if AOA is increased. The real cause of lift going away is flow separation. Away from the ground, flow separation is purely a function of AOA. Close to the ground, however, the downflow at the trailing edge is diminished, causing less separation, hence less drag and more lift. You could be at the free air stall AOA while in ground effect and have the plane float down the runway.
 
Tom-D said:
This is why a very old timer told me anyone doing wheels landing in a taildragger is just showing off.
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The speed difference between a three-point landing and a wheel landing doesn't have to be large. If one touches down with the tailwheel just off the ground and then raises the tail to make sure the airplane stays put, one can actually stop much shorter due to less lift and more traction for braking. Have done this in numerous taildraggers.

We don't need to have 15 knots more for a wheel landing. Not even 5 knots.
 
"lift going away" is NOT the definition of stall either. Stall is the point where further increase in angle of attack doesn't result in increase in lift. In fact, the slope of the lift vs. aoa reverses at that point but has about the same absolute value. It's not the case when you stall you lose all (or nearly all the lift). Ground effect does not affect stalling. What it does do is increase lift and decrease drag, both of which help very much with flight at low airspeeds.

The answer is that yes, carrying excess speed in increases the energy and causes problems, but it is completely unrelated to being stalled or not.
 
Under normal conditions in the landing configuration, my aircraft generally stalls at 60kias. Based on watching numerous cockpit videos and analysis from CloudAhoy of 30+ landings, it looks like I touchdown at 62 or 63kias pretty consistently. There's a little energy in reserve, but not much.
 
coma24 said:
Under normal conditions in the landing configuration, my aircraft generally stalls at 60kias. Based on watching numerous cockpit videos and analysis from CloudAhoy of 30+ landings, it looks like I touchdown at 62 or 63kias pretty consistently. There's a little energy in reserve, but not much.
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Cloud ahoy knows your airspeed? Wouldn't IAS be somewhat lower than TAS in a no wind situation, then you have to add the head wind to your ground speed, maybe its a wash. But whatever you're doing, you're doing it consistently :)
 
exncsurfer said:
Cloud ahoy knows your airspeed? Wouldn't IAS be somewhat lower than TAS in a no wind situation, then you have to add the head wind to your ground speed, maybe its a wash. But whatever you're doing, you're doing it consistently :)
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Yes. At least computationally. CloudAhoy uses wind data and some algorythm to provide IAS, TAS and GS in its debriefings.
 
midlifeflyer said:
Yes. At least computationally. CloudAhoy uses wind data and some algorythm to provide IAS, TAS and GS in its debriefings.
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Then it is not reliable down to a few knots. Not even close.

What wind data? The METAR? Winds could have no relation to reality. That suffers crippling sampling error.

Obvious case of GIGO.
 
I was suspicious at first as well, and in fact, enroute, I have seen some IAS discrepancies because the winds aloft data was inaccurate. However, in cases where the surface winds are accurate, it seems to do a good job. Again, comparing the video replays of the actual cockpit instruments vs the cloudahoy replay has boosted my confidence in the cloudahoy numbers quite a bit.

Also, while I can't do it in my airplane, there are avionics suites (such as G-1000 and Dynon) which can export the actual IAS numbers from the stack straight into CloudAhoy.
 
MAKG1 said:
Then it is not reliable down to a few knots. Not even close.

What wind data? The METAR? Winds could have no relation to reality. That suffers crippling sampling error.

Obvious case of GIGO.
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True, if you are looking for perfection.
 
midlifeflyer said:
True, if you are looking for perfection.
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We have people making conclusions using that data, to a couple of knots. It's not good enough for that. Not even close.

It's true if you're looking for any result other than assuming TAS = GS. I.e., completely worthless. Except MAYBE if the winds are several tens of knots and don't vary or gust.

There is something wrong with a lawyer thinking he can lecture a numerical modeler about sampling and measurement error. Just what training in numerics did your law degree include?
 
MAKG1 said:
We have people making conclusions using that data, to a couple of knots. It's not good enough for that. Not even close.
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But in a practical sense a couple knots doesn't matter. Can you fly within a couple knots? If you can you are much better than me.

We have people here who love theoretical equations but you do not fly in a laboratory under strictly controlled conditions.
 
coma24 said:
I was suspicious at first as well, and in fact, enroute, I have seen some IAS discrepancies because the winds aloft data was inaccurate. However, in cases where the surface winds are accurate, it seems to do a good job. Again, comparing the video replays of the actual cockpit instruments vs the cloudahoy replay has boosted my confidence in the cloudahoy numbers quite a bit.

Also, while I can't do it in my airplane, there are avionics suites (such as G-1000 and Dynon) which can export the actual IAS numbers from the stack straight into CloudAhoy.
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Of all of the elements involved in flight planning, wind direction and velocity are the weak links. In order for a Winds and Temperatures Aloft Forecast to be close to accurate you must fly directly over the reporting station (only a couple of hundred, nationwide), at the pressure altitude in the forecast, at the valid time. Can't be done reliably. Skew-T is far more accurate, with thousands of sites and an altitude continuum, for starters.

Bob Gardner
 
Dan Thomas said:
The speed difference between a three-point landing and a wheel landing doesn't have to be large. If one touches down with the tailwheel just off the ground and then raises the tail to make sure the airplane stays put, one can actually stop much shorter due to less lift and more traction for braking. Have done this in numerous taildraggers.

We don't need to have 15 knots more for a wheel landing. Not even 5 knots.
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Ever see what happens when you do a wheels landing not knowing you have a brake stuck?
 

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FastEddieB said:
To be fair, can we know what would have happened in a full stall landing with the same stuck brake?
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It's a matter of where the CG is, with the tail way low on a three point landing it would have screeched to a halt with both wheels skidding.
As I was doing a wheels landing it touched stuck wheel first, and I was 90 degree to the runway before I could react. crow hopped sideways twice and broke the gear off, and down it went.
 
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