landing flaps below 200 AGL?

[poadeleted20]

No, no, I didn't say "Do you always plan...", I said "Can you always plan...", meaning, to put it another way, "You cannot always expect your plans to work out".

I think that's what I was saying -- you have to keep collecting data and modify your plans accordingly so you don't, on arrival at your destination, discover to your surprise that the winds there are outside your personal limits, but you now have no remaining choice except to land in those otherwise-unacceptable conditions.

Or as George Strait said, "No matter what you do, no matter where you go, you've got to have an ace in the hole." (Lyrics: Dennis Adkins)

 

[nosehair]

you have to keep collecting data and modify your plans accordingly so you don't, on arrival at your destination, discover to your surprise that the winds there are outside your personal limits, but you now have no remaining choice except to land in those otherwise-unacceptable conditions.

Right, that's what you do constantly, to avoid getting beyond your personal limits, ...but what I am saying is that you should still be prepared for the unexpected.

No matter how much you stay on top of the situation, conditions can change so much that no one could have expected it, and if you fly constantly enough and long enough, you will experience the unexpected. That's why we practice emergency procedures.

In that same train of thought, we should practice cross-wind landings in conditions that are beyond our comfort level, because it may happen that we run out of options, just like an engine failure.

 

[dmccormack]

No matter how much you stay on top of the situation, conditions can change so much that no one could have expected it, and if you fly constantly enough and long enough, you will experience the unexpected. That's why we practice emergency procedures.

I consider risk in layers -- that is, there are the things about each flight I can control (when/ if to launch, fuel, W&B, weather, etc) then things that I have some control over (route, overall airplane performance, airport congestion, water in fuel, etc), and stuff I have no control over (Other aircraft NORDO and painted light gray at my altitude, water buffalo crossing the runway, cracked connecting rod, etc).

I've had a couple of no control events this flying season (lost plug on departure, lost all electric in IMC) and one some control event (broken alternator belt).

"Some control" because I choose to continue to flight VFR to my destination even though I was on an IFR flight plan. Any weather was behind me, I was 15 minutes from my destination, had enough battery reserves to squawk 7600, and was flying in uncongested airspace. I called ATC as soon as I arrived and everything was good (including the ASRS form I filed an hour later )

We're kidding ourselves if we think we can fly risk free. (It's sorta like the NFL claiming that "player safety" comes first. Oh really? Wouldn't "safety first" mean no contact at all?)

 

[poadeleted20]

Right, that's what you do constantly, to avoid getting beyond your personal limits, ...but what I am saying is that you should still be prepared for the unexpected.

On that, I think we are in violent agreement.

 

[poadeleted20]

In that same train of thought, we should practice cross-wind landings in conditions that are beyond our comfort level, because it may happen that we run out of options, just like an engine failure.

Well, on that, I would not agree, or at least, not exactly as stated. I would say that it's a good idea to get up with an instructor and go outside your comfort zone so you know exactly where your personal skill limits are compared to your comfort limits. But I would not recommend expanding the envelope without someone along whose known envelope is not being exceeded.

As for your initial scenario (being in a situation where you have no choice but to land with a crosswind that exceeds your personal limits), I just don't see how that can happen without violating my personal rule of always having an out, even if it's to land on a ramp or taxiway.

 

[COFlyBoy]

Well, on that, I would not agree, or at least, not exactly as stated. I would say that it's a good idea to get up with an instructor and go outside your comfort zone so you know exactly where your personal skill limits are compared to your comfort limits. But I would not recommend expanding the envelope without someone along whose known envelope is not being exceeded.

As for your initial scenario (being in a situation where you have no choice but to land with a crosswind that exceeds your personal limits), I just don't see how that can happen without violating my personal rule of always having an out, even if it's to land on a ramp or taxiway.

Amen. I went and tried to push my confort zone and it was .... well.... uncomfortable. 90 deg x-wind ~15 - 25 kts. It burbled over the houses and trees in the airpark. It took me 4 approaches to get down. Would have been much better with a capable instructor next to me. I had plenty of gas, the weather was good (except for the wind) and there are plenty of runways pointing all different directions in the Denver area, so it never got to the dangerous point, but it wasn't as much fun as I was hoping for.

 

[flyingcheesehead]

Does slipping flight change the stall speed of the aircraft?

Okay, I turned this over in my mind a bit, and I'm not really sure.

In a slip, an airplane with dihedral will have an increase in AoA on the down wing and a decrease on the up wing. But the overall effect should be negligible, I think.

Please explain!

I would say yes but by a negligible amount - anytime your wings are not exactly level (like in slipping) your stall speed goes up.

Not true. Stall speed doesn't go up in a turn, either, UNLESS you make a *level* turn, which will increase your load factor.

 

[dmccormack]

Okay, I turned this over in my mind a bit, and I'm not really sure.

In a slip, an airplane with dihedral will have an increase in AoA on the down wing and a decrease on the up wing. But the overall effect should be negligible, I think.

Hmmm...

Try stalling from a slip. Which wing drops?

 

[flyingcheesehead]

Hmmm...

Try stalling from a slip. Which wing drops?

The down wing... But since we're talking about crosswind landings here, that will be the upwind wing, which is the side we want to come down first anyway.

I generally don't do a full-stall-to-the-break landing. I might get the horn to chirp, but there's a couple knots left. But, AoA is high enough that when I lower the nose, the plane's done flying. (I haven't done any of these extreme crosswind landings in a tailwheel yet, and I probably won't. )

Regardless, I still don't see how being in a slip would affect your stall speed to the degree that you would want to add speed for a *crosswind* as opposed to gust factor.

 

[dmccormack]

The down wing... But since we're talking about crosswind landings here, that will be the upwind wing, which is the side we want to come down first anyway.

Ummm....

The high wing will stall first in a slip, which will return the airplane to somewhat wings level, making a stall from a slip somewhat benign.

A skid will cause the low wing to drop. inverted flight may ensue.

From the AFH:

If the airplane is slipping toward the inside of the turn at the time the stall occurs, it tends to roll rapidly toward the outside of the turn as the nose pitches down because the outside wing stalls before the inside wing. If the airplane is skidding toward the outside of the turn, it will have a tendency to roll to the inside of the turn because the inside wing stalls first.

I agree that airspeed adjustment for crosswind makes no sense, but a bit of distrust of the ASI during an aggressive slip is a good thing.

I tend to slow up to 50, put in a full slip, then drop the nose.

The speed builds up a bit (usually indicates 60 but I don't care) and the airplane drops like a rock.

 

[flyingcheesehead]

Ummm....

The high wing will stall first in a slip, which will return the airplane to somewhat wings level, making a stall from a slip somewhat benign.

A skid will cause the low wing to drop. inverted flight may ensue.

Okay, I'm confusing myself with the up/down wings here, because I'm thinking of level flight.

Let's say I'm coming in with a crosswind from the left... I have right rudder and some left aileron to hold the left bank. The upwind wing (the left one) should stall first... Right? Stand in front of and to the left of a high-wing airplane, where the relative wind would be coming from, and look at each wing - The left wing, in this case, has a higher angle of attack than the right one. That's how dihedral makes a plane more stable.

The only thing that would make sense to me as far as the downwind wing stalling first is that it's got the down aileron. But, with your average modern airplane, there's some washout built in to keep the aileron from stalling, so that's not going to be the cause.

 

[nosehair]

I have right rudder and some left aileron to hold the left bank.

The right rudder will cause a yaw to the right, and subsequent wing drop. In every stall, the nose (and wing) will go in the direction that the rudder is deflected.

 

[gismo]

The right rudder will cause a yaw to the right, and subsequent right wing drop. In every stall, the nose (and wing) will go in the direction that the rudder is deflected.

Clarified it for ya. (your statement was correct but slightly ambiguous).

And Kent, if you apply that to the original issue of stalling in a forward slip, you'll see that the low wing is the one that comes up. If you were in a slipping turn (e.g. right rudder in a left turn) applying enough rudder relative to the bank angle to make the airplane turn right puts you into a skid whether or not the airplane remains banked to the left and stalling in that condition would cause the low/left/outside wing to come up.

 

[jesse]

Okay, I'm confusing myself with the up/down wings here, because I'm thinking of level flight.

Let's say I'm coming in with a crosswind from the left... I have right rudder and some left aileron to hold the left bank. The upwind wing (the left one) should stall first... Right? Stand in front of and to the left of a high-wing airplane, where the relative wind would be coming from, and look at each wing - The left wing, in this case, has a higher angle of attack than the right one. That's how dihedral makes a plane more stable.

The only thing that would make sense to me as far as the downwind wing stalling first is that it's got the down aileron. But, with your average modern airplane, there's some washout built in to keep the aileron from stalling, so that's not going to be the cause.

You don't spin from a slip. In a left turning slip you'll have right aileron applied. When the stall occurs it'll either just remain nicely in a stalled slip (common in most of our aircraft) or it may roll to the right, past wings level, into a skid, and then into a spin.

Video of me running through this in a 172. In this case it wouldn't spin from the slip. I had full left aileron and full right rudder and the yoke back to the stops and it just remained in a stable stalling slip. If it were to spin it would first have to roll into a skid.:
http://www.youtube.com/watch?v=5xDxj_CRfqY

 

[flyingcheesehead]

Clarified it for ya. (your statement was correct but slightly ambiguous).

And Kent, if you apply that to the original issue of stalling in a forward slip, you'll see that the low wing is the one that comes up. If you were in a slipping turn (e.g. right rudder in a left turn) applying enough rudder relative to the bank angle to make the airplane turn right puts you into a skid whether or not the airplane remains banked to the left and stalling in that condition would cause the low/left/outside wing to come up.

Aha, much better.

But now, back to the issue that brought me to re-light this thread: Does stall speed increase in a slip? And if yes, a) why? and b) how much (ie is it significant to the issue at hand, landing in a crosswind)?

 

[dmccormack]

Aha, much better.

But now, back to the issue that brought me to re-light this thread: Does stall speed increase in a slip? And if yes, a) why? and b) how much (ie is it significant to the issue at hand, landing in a crosswind)?

A slip will increase drag and disturb airflow over the wings.

So I will presume that yes, there is an increase in the indicated speed some part of the wing will stall.

Nevertheless, I'll defer to the astrophysicistbiochemicalaerodynamicfluid engineers that will inevitably chime in.

 

[flyingcheesehead]

A slip will increase drag

But that doesn't change your stall speed...

and disturb airflow over the wings.

But in a significant way?

My thought was that since the fuselage is blanking out one part of the wing, that will increase your descent rate and thus require an increase in AoA to compensate - But that's something you actively do, not a physical effect that's going to surprise you.

Plus, I'm genuinely curious whether a crosswind alone warrants any increase in landing speed, because I don't think it does.

Nevertheless, I'll defer to the astrophysicistbiochemicalaerodynamicfluid engineers that will inevitably chime in.

 

[dmccormack]

But that doesn't change your stall speed...But in a significant way?

My thought was that since the fuselage is blanking out one part of the wing, that will increase your descent rate and thus require an increase in AoA to compensate - But that's something you actively do, not a physical effect that's going to surprise you.

Well, if you have to increase AoA to compensate for loss of let's say 1/3rd the wing's lifting potential... what's the Vs impact?

Plus, I'm genuinely curious whether a crosswind alone warrants any increase in landing speed, because I don't think it does.

Did I say that?

Nope.

 

[flyingcheesehead]

Well, if you have to increase AoA to compensate for loss of let's say 1/3rd the wing's lifting potential... what's the Vs impact?

But what I'm saying is that the increase in AoA is something the pilot has to actively do, and doing a slip does not automatically require it if you're trying to increase your descent rate. In other words, it's the pilot increasing the AoA that will put you closer to the stall, not the fact that the pilot is slipping.

Did I say that?

Nope.

No. But that's the entire reason for this latest line of questions - I do not think that a crosswind alone is a good reason for increasing approach speed, while some others do. I'm trying to find out if there is or isn't a scientific reason behind it, or if it's yet another OWT.

 

[dmccormack]

But what I'm saying is that the increase in AoA is something the pilot has to actively do, and doing a slip does not automatically require it if you're trying to increase your descent rate. In other words, it's the pilot increasing the AoA that will put you closer to the stall, not the fact that the pilot is slipping..

The high wing must have a higher AoA.

How close to stall?

I don't know because my pitot is not getting direct ram air.

Which is why a slip is a feel exercise and not a "Check the Panel" exercise.