Losing altitude in your carves in wind versus no wind

[ianmdrennan 2]

Quote

I am not a stupid person, and have not discussed this issue with stupid or inexperienced people.

I don't think you are a stupid person but your sources are misinformed, if you remember what they said correctly. This is an "old school" thought that appears to make perfect sense but simply doesn't. Like I said call up Scott Miller (if you don't know who he is - he was/is PD's chief test pilot) as he understands far more about canopies and how they fly than your sources. He's a great guy and will be able to explain the concept to you in terms that you can relate to.

Blue skies
Ian

Performance Designs Factory Team

[Hooknswoop 19]

If it were true that a canopy descends more in a turn when there is wind, then it would descend lees if the maneuver was done the exact opposite, so that the canopy was landed downwind. This is not the case.

If it were true that a canopy descends more in a turn when there is wind, then aircraft would descend and even climb faster (fpm) dependant on the wind, they don’t.

Have you seen the video of the porter flying next to the free-flyer? The porter descends at the same rate, regardless of the wind, as it circles the free-flyer.

A helicopter hovering next to a hot air balloon that is moving 20 mph over the ground will show zero airspeed, regardless of the direction it is pointed.

Do you agree that wind has no affect on a canopy's airspeed?

Derek

[SBS 0]

I know Scott, know that he knows this stuff very well, and knows far more than I do. I know as well, though, that the people who I speak to are also very well schooled in swooping and canopy control.

A) It is a pretty bold statement to say that he knows far more than my sources of information when we haven't discussed who my sources are.

B) My girlfriend has a degree in astrophysics and is getting a masters in math, but I can add and multipy numbers in my head far faster than she can...she knows infinitely more in this area than I do, but amount of knowledge does not mean that someone is better in every aspect of the study at hand, or is always right.

The only reason I continue this discussion is not to try to be right...this is a matter of safety; mine, and those reading these posts who are just learning.

I will continue to try to reach the people with whom I have discussed this in the past, as well as others who are knowledgable and I respect.

Blue Ones,

Steve

_____________
I'm not conceited...I'm just realistic about my awesomeness...

[ianmdrennan 2]

Quote

A) It is a pretty bold statement to say that he knows far more than my sources of information when we haven't discussed who my sources are.

You're right - it is pretty bold. Justified though I think. There are plenty of people running canopy schools (I can name a few) that still teach some of these canopy myths. My vote goes with the manufacturers, they understand this stuff waaay better than any of us. I'm not saying you have bad sources, I'm just saying that given inconsistencies in data that I'd err on the manufacturers side.

Quote

The only reason I continue this discussion is not to try to be right...this is a matter of safety; mine, and those reading these posts who are just learning.

Dude - that reason in itself is a great one. No doubt there's a lot of bad information out there - in fact that's something we're trying to put to rest now
Blue skies
Ian

Performance Designs Factory Team

[SBS 0]

Do you agree that wind has no affect on a canopy's airspeed?

---------------

I agree to the point that in straight and level flight, as in the examples of an airplane that you have used, that the airspeed is not affected by wind. I disagree with this analogy being used, though, because we are not talking about wind being presented horizontally to the canopy, we are talking about what would be more comparable to a thermal or a downdraft presented to a wing.

Further, what we are talking about is really another form of ground speed, as we are using the ground as a point of reference...I don't think that the question was asked because the person is concerned about the actual airspeed of a turn at high altitude, rather I believe that it was asking about how fast the canopy is going to approach the ground on landing.

-----------------------

If it were true that a canopy descends more in a turn when there is wind, then aircraft would descend and even climb faster (fpm) dependant on the wind, they don’t.

---No, this is not able to be concluded from my argument...it is referring to horizontal wind being presented to the front or rear of an aircraft wing in basic flight, not a dynamic turn.

Have you seen the video of the porter flying next to the free-flyer? The porter descends at the same rate, regardless of the wind, as it circles the free-flyer.

---Here you are talking about a heavy, fixed wing aircraft and not taking into account the amount of time that the top side of the wing is presented to the wind, and the added inertia that the aircraft has while diving at 160 mph, thus making it more or less susceptible to variances in speed, etc. The lift created by a fixed wing is going to differ from the lift created by a canopy that is susceptible to pressure changes through different points of its flight. One can go on and on with the differences between aircraft flight and canopy flight...although, it is similar, it is not exactly the same, so cannot necessarily be used to illustrate perfectly a principle of canopy flight.

A helicopter hovering next to a hot air balloon that is moving 20 mph over the ground will show zero airspeed, regardless of the direction it is pointed.

---Again, wind being presented horizontally to a wing in basic flight, not a dynamic turn.


-S

_____________
I'm not conceited...I'm just realistic about my awesomeness...

[SBS 0]

I'm just saying that given inconsistencies in data that I'd err on the manufacturers side.

-----------------

I did call a manufacturer and test pilots...

If I am right, and people believe you, they may hit the ground. If I am wrong, and they believe me, they will curse my name as they plane out high from a turn or two and then bring it down a little bit. I prefer the sound of the second one...

-S

_____________
I'm not conceited...I'm just realistic about my awesomeness...

[Hooknswoop 19]

Quote

Do you agree that wind has no affect on a canopy's airspeed?

---------------

Quote

I agree to the point that in straight and level flight, as in the examples of an airplane that you have used, that the airspeed is not affected by wind. I disagree with this analogy being used, though, because we are not talking about wind being presented horizontally to the canopy, we are talking about what would be more comparable to a thermal or a downdraft presented to a wing.

Further, what we are talking about is really another form of ground speed, as we are using the ground as a point of reference...I don't think that the question was asked because the person is concerned about the actual airspeed of a turn at high altitude, rather I believe that it was asking about how fast the canopy is going to approach the ground on landing.

Why would wind not affect a canopy in a steady state flight, but would affect it in a turn/dive? The wind hasn’t changed, it is still horizontal. It is the canopy’s attitude that has changed. It will not descend any faster if the air mass it happens to be flying through is moving over the ground or not.

Quote

If it were true that a canopy descends more in a turn when there is wind, then aircraft would descend and even climb faster (fpm) dependant on the wind, they don’t.

---No, this is not able to be concluded from my argument...it is referring to horizontal wind being presented to the front or rear of an aircraft wing in basic flight, not a dynamic turn.

To clarify, you are saying wind does not affect a canopy in stead state flight, but it does affect a canopy that is turning hard?

Quote

Have you seen the video of the porter flying next to the free-flyer? The porter descends at the same rate, regardless of the wind, as it circles the free-flyer.

---Here you are talking about a heavy, fixed wing aircraft and not taking into account the amount of time that the top side of the wing is presented to the wind, and the added inertia that the aircraft has while diving at 160 mph, thus making it more or less susceptible to variances in speed, etc. The lift created by a fixed wing is going to differ from the lift created by a canopy that is susceptible to pressure changes through different points of its flight. One can go on and on with the differences between aircraft flight and canopy flight...although, it is similar, it is not exactly the same, so cannot necessarily be used to illustrate perfectly a principle of canopy flight.

A helicopter hovering next to a hot air balloon that is moving 20 mph over the ground will show zero airspeed, regardless of the direction it is pointed.

---Again, wind being presented horizontally to a wing in basic flight, not a dynamic turn.

I don’t see the difference. The airspeed indicator reads zero regardless of the direction it is pointed. So if it changes attitude suddenly, there is still no wind acting on the helicopter. It is moving at the same speed as the air mass around it. There is no wind hitting the helicopter that would make the airspeed indicator read anything. Just because it changes attitudes does not change the fact that it is not moving relative to the air around it.

Back to the fish bowl analogy. A fish in a bowl swims around at 1 mph. It can descend, rise, and swim around exactly the same regardless if the fish bowl is stationary relative to the ground, or if it is moving relative to the ground. Do you agree with this?

Derek

[SBS 0]

What I am saying is that when you give a certain amount of input, you are creating a certain amount of energy to a given motion. Depending on what you have presenting itsself to the body and how that body is presenting its energy to the outside forces, will affect the vectors of the energy dispersement...not destroy the energy. What I see in your arguements is that the energy will simply disappear, being that you are not moving forward in relation to the ground. What I am saying, though, is that the energy has to go somewhere. I do believe that there is a difference between the wind being presented to the front of the wing and to the top or bottom of the wing. If you are in straight and level flight, and you have a head wind, the lift that the canopy is creating is not being cancelled out by anything. If, though, by presenting the source of that lift to the wind for an extended period of time, as in a carving turn, the lift is being cancelled out by the headwind, and thus changing the recovery arc. The energy within the arc remains the same, but is going to change based on the resistance that the canopy gets in movement one way or another.

Like you said earlier, if the wind were presented to the top skin, it would collapse the canopy. It doesn't collapse it, but it does change the pressurization and flight characteristics, which is one of the reasons that airplane analogies are not perfect.

Also, again, we are not talking about airspeed...we are still talking about ground speed, in so much as we are using the ground as a point of reference for the decent. We are just not talking about horizontal ground speed.

If we are talking about airspeed, then the canopy thinks that it is recovering into the air whether it is recovering relative to the ground or not. Again, it is like hitting a downdraft. If one is in straight and level flight and hits a downdraft, that will affect the canopy. It will depressurize the canopy, it will change its flight. When you make a turn into the wind, and you present the top skin, you are essentially presenting it to what would be comparable to a down draft in straight and level flight...if the wind is not high, your added speed from the carving turn will render the difference mostly unnoticable...but, if the wind is high in relation to your added speed, then it can affect the pressurization of your canopy and thus make your decent faster and your recovery arc will change.

I have always been taught, and felt that it is necessary to change the altitude of your turn based on a few factors, including: temperature, altitude, terrain (for thermals), and wind...just to name a few. I have heard mixed reports about what wind can do to an approach, from, "you can start your hook lower" to "you can start your hook higher", but what I had not heard until yesterday, was "start it at the same altitude". I think it's an interesting thing to think about, but I am just not convinced, from past discussions and personal experience, that that is the case. I dunno what else to say.

-S

_____________
I'm not conceited...I'm just realistic about my awesomeness...

[headoverheels 334]

If swoopers tend to start their swoop over the same point on the ground, regardless of the winds, they must turn faster in high winds, if they want to land at the same point on the ground as in no winds. So, if they always start over the same point, they will lose more altitude in high winds than they will lose in no winds, because they are turning faster/steeper. So, yes, in this case you will lose more altitude when there is more wind, but it is because the turn rate was adjusted, rather than the turn initiation point. That might, indeed, be what swoopers tend to do, since it keeps the picture closer to their typical swoop. If so, they do indeed need to start higher, since they are turning faster/steeper.

Edited to add: or they can start their same swoop rate/point higher, and have longer to fly upwind at the end of the swoop. It's not that you lose more altitude in high winds, with the same canopy contol input, it's that you will end up farther downwind, and need to fly upwind longer while remaining in your swoop.

[johnny1488 1]

If I recall correctly, when I had this conversation w/ Scott, he said most people say a canopy dives less in high winds. The reason he said they came to this conclusion is in say, a 180 turning into the wind, on a no wind day the jumper turns, lands, no problem. In, say, 20mph winds, he turns, during the dive isnt making the same headway over the ground (ground speed) sees himself now diving straight at the same point on the ground, and says, oh shit, I better pull out, whether consious or not. It is only the ground that makes the difference. Or, more correctly, the pilot that makes the difference.

Johnny
--"This ain't no book club, we're all gonna die!"
Mike Rome

[davelepka 4]

As much as I hate to get involved, lets look at it this way;

Judging from your jump numbers, canopy selection, and the fact that you're involved in this thread, I'm guessing you're a swooper (good choice). I'm also going to guess that you have done some high pulls, or even hop n pops from full altitude.

It's common for upper level winds to be blowing at speeds higher than you would ever want to jump in while the wind on the ground is more reasonable.

If you've ever had the occasion to pull at an altitude with winds blowing at 40, 50 or 60 knots, according to your argument, your canopy would dive MUCH longer than any landing approach you've ever flown (assuming that you are not jumping in winds much higher than 25PH on the ground).

Your assertion is that ground winds differing by a factor of 2x (lets say 12 mph compared to 24) would cause enough extra dive that the swooper could not toggle (or rear riser) out of, but that the swooper would need to initiate thier turn at a higher altitude to maintain a level safety.

Looking at this theory 10k ft higher, where you could easily see winds at a factor of 4x or 5x the 12mph gound winds, wouldn't you notice a dramatic difference in the duration and subsequent speed of your dive? Logic would state that you would see such a difference. Due to drag and other factors, it might not be the same magnitude as the increase in wind speed, it would certainly be noticeable.

I have never noticed such a difference, nor would I suspect has any of the other jumpers on this thread. The absence of a nearby fixed object (the ground) for reference might make slight differences difficult to detect, but as we discussed, the difference at altitude, with a substantial wind, would have to be more than slight. With several thousand jumps on my current model of canopy, I would surely know by the feel of the harness if my canopy were diving for an unusaully long time.

From an aerodynamic standpoint, I think that you may be in the wrong, HOWEVER, your message has some merit in that it builds in an extra dose of caution while jumping in higher winds. Unpredictable gusts, or object related turbulence are some real-world factors that become more pronounced with higher winds. In these conditions, there is a distinct advantage to swoopers using an extra dose of caution, and hooking it a bit high. Whatever their reasoning may be, and if thier reasoning is scientificly sound or not, the end result is some additional caution in conditions that certainly merit it.

[SBS 0]

We are talking, though, about a ground that is very unforgiving...10 feet can make a huge difference. At altitude, there would obviously be differences...they can be felt in the opening, in the speed, etc... But, that does not mean that a canopy will dive for 300 feet...maybe 25, maybe 50...I don't know. There are a lot of factors as well...air pressure coming immediately to mind. I am not a scientist, I do not claim to understand everything fully, but have tried to illustrate a principle that I believe to be correct, as do others with much more experience than myself. In any event, I have spent a lot of time defending this position that I don't believe to be as bupkis as anyone here obviously does. Do what you want to do. When you know your canopy and how to land it in various situations, great...if you don't, err towards the side of safety...and when in doubt, start it high.

-S

_____________
I'm not conceited...I'm just realistic about my awesomeness...

[pilotdave 0]

I haven't read this whole thread, just parts, so maybe I'm wrong here. But it sounds like what you're arguing is that for a short period of time, during a maneuver, relative wind hits the top of the canopy, and this is different depending on the wind speed (ie the weather). This just doesn't make sense. Just think of it this way: Your canopy would collapse if the wind hit it from above. Or at least your lines would go slack. Does that happen? The angle of attack of the canopy INCREASES during a turn. The direction of the wind HAS NO AFFECT, assuming a steady wind. Imagine you're on a giant moving sidewalk. Your walking is not affected by the direction or speed of the sidewalk as long as it's constant. The only thing that is affected is your velocity relative to the fixed earth.

Gusts are a different matter. The way aerospace engineers think of gusts is as in finite changes of airspeed, angle of attack, and/or sideslip angle. In other words, when a gust hits, it'll affect your airspeed and the angle you're flying to the relative wind. Depending on the stability characteristics of the aircraft, it will return to a constant state. In other words, when a gust comes from the side, the aircraft will have a sidelsip angle. The aircraft won't continue flying sideways relative to the wind though.

It doesn't sound like you're talking about gusts though. For steady wind, the wind speed CANNOT have an affect on the way the canopy flies.

Now of course if there was a constant downdraft, sure, you'll be descending faster, relative to the earth (but not relative to the wind).

I'm no swooper but I do fly a 140 square foot wing loaded at 19:1.
Dave

[kallend 2,146]

Quote

Quote

Here is another example, using an airplane...

In order for an airplane to go straight down, it must nose over past vertical, because if it simply turns down 90 degrees, the lift created by the wings will cause the plane to travel at an angle...

A canopy creates lift...when the canopy is pointed towards the ground, the lift is created horizontally, based on the angle of attack of the canopy. Let's call this lift that it is creating "forward energy" in this case, because we are talking about the canopy being nose over in a carve. If there is no wind, this forward energy that is being created has nothing stopping its progression, so for every measure of energy that is created, it is spent on horizontal movement over the ground. Let's say that it is 20mph of wind speed that is created. Now, if that is being created pushing against 20 miles per hour of wind, that will not change your wind speed, but it will change your flight. Your foward vector will be reduced to zero (as relating to the energy that was specifically created by that lift), but the energy is not destroyed. As we remember from Junior High, energy is not created or destroyed, only changed in form. So, where does that lift that the canopy created go? It dispurses itsself into the other vectors of the canopies flight.

When we are presented to the wind, the lift is no factor, but when we point that lift into said wind, then it is affected. The energy has to go somewhere, and there are two major vectors in the approach...forward drive and downward drive.

You are thinking in terms of relative to the ground and not relative to the air mass.

First, define wind. Def n. a large body of air in rapid natural motion.

Second, how do we measure wind? With a wind meter that is fixed, usually in mph or knots. This tells us how fast the air mass is moving in relation to the ground.

Third, define airspeed, the speed at which a body moves through the air.

Airspeed is irreverent of wind speed. An aircraft, glider, or canopy flys exactly the same regardless if the air mass it is flying through is moving across the ground or not.

A perfect loop as viewed from a hot air balloon will look exactly the same to the observer in the basket in zero wind as it would in a 50 mph wind, because the balloon is staying at the same fixed point within the moving air mass, even though it is moving over the ground at 50 mph. To an observer on the ground, the loops would look different because the air mass is moving relative to the observer on the ground. The loops would be identical to the pilot of the aircraft. The wind doesn’t affect how the aircraft flys, lift vectors, or anything else, only its ground speed.

Derek

Flying near the ground, we fly a path relative to the ground because that's what we see. We cannot see the air mass.

I submit that the pilot will adjust his/her control inputs in order to achieve the sight picture that they know from experience - and that picture is a picture of the ground.

I seriously doubt that the canopy pilot is actually flying the same path relative to the airmass on a high wind day as on a calm day. The control inputs will be different, and hence the canopy behavior will be different.

Same argument as the "downwind turn" in an airplane. The simple argument is that an airplane doesn't know the difference between a downwind turn and any other turn, which is true. Neither does a pilot flying under the hood by reference to ball and needle. But a pilot flying at low altitude by ground reference will see a big difference and will actually fly a different path relative to the air. That's one of the reasons the FAA tests for a pilot certificate require low altitude maneuvers by ground reference. To make a turn around a point in a strong wind requires quite different control inputs than on a calm day.

...

The only sure way to survive a canopy collision is not to have one.

[Hooknswoop 19]

Quote

Flying near the ground, we fly a path relative to the ground because that's what we see. We cannot see the air mass.

I submit that the pilot will adjust his/her control inputs in order to achieve the sight picture that they know from experience - and that picture is a picture of the ground.

I seriously doubt that the canopy pilot is actually flying the same path relative to the airmass on a high wind day as on a calm day. The control inputs will be different, and hence the canopy behavior will be different.

Same argument as the "downwind turn" in an airplane. The simple argument is that an airplane doesn't know the difference between a downwind turn and any other turn, which is true. Neither does a pilot flying under the hood by reference to ball and needle. But a pilot flying at low altitude by ground reference will see a big difference and will actually fly a different path relative to the air. That's one of the reasons the FAA tests for a pilot certificate require low altitude maneuvers by ground reference. To make a turn around a point in a strong wind requires quite different control inputs than on a calm day.

Right, the pilot perceives that a canopy dives longer on a windy day, but it doesn’t. Given the same input the canopy reacts exactly the same regardless if there is wind or not. The only difference is groundspeed.

Derek

[Erroll 80]

Just an observation: It is our season for violent Summer thunderstorms. I watch the clouds build up every afternoon. These storms are often accompanied by very high winds. I have yet to notice the clouds (front,top,bottom,back) get distorted by the wind. The clouds seem to rush by quite fast (relative to me on the ground) but hardly change shape within the airmass with which they are moving.

[The111 1]

All I have to say is this: the answer to this argument lies not in astrophysics or years of swooping experience. And it doesn't matter what expert you can pull out of what hat. You need to be able to explain your viewpoint on your own, for your sake at least. Take a basic physics course that covers fixed versus moving reference frames (relative motion), and if you can fully understand that then this issue will no longer be a debate.

The one thing you keep focusing on is how the wind will "hit the top of your canopy", and you are implying that it will hit it harder if the wind is faster. That would be true, IF your parachute was simply materializing out of thin air and diving into the moving air mass without any groundspeed. But in a huge mass of moving air, your canopy is already moving WITH the air.

Simple example:

Case A - The air is moving 60mph (relative to the ground). You are flying downwind, and your canopy flies 10mph airspeed. So your groundspeed is 70mph. You do a 180 hook (for simplicity the hook will not speed you up, simply change your direction), and end up going INTO the wind, now your ground speed is 50mph (although you are unfortunately going backwards relative to the ground).

Case B - The air is moving 10mph (relative to the ground). You are flying downwind, and your canopy flies 10mph airspeed. So your groundspeed is 20mph. You do a 180 hook (for simplicity the hook will not speed you up, simply change your direction), and end up going INTO the wind, now your ground speed is 0mph (it appears you are coming straight down relative to the ground).

In Case A, your groundspeed went from 70mph to 50mph. While you were turning, it is true your top skin got exposed to a 60mph wind, but you were moving with the wind so it didn't matter. If you had been sitting still, in a dive position (which is impossible), 60mph of wind would sure as hell collapse your canopy, but you weren't sitting still, you were moving hella fast (rel to ground) with the wind.

In Case B, your groundspeed went from 20mph to 0mph. While you were turning, your top skin got exposed to 10mph of wind. True that is much less than 60mph, but it had the same effect since in this case your groundspeed was also much smaller.

If all else fails, remember that the earth is spinning and even when there's no "wind" (moving air relative to the ground), the air you are flying through is still moving.

EDIT: I'm not the most experienced canopy pilot and I didn't even attempt to make my numbers accurately reflect the speeds of canopies relative to the ground or air. It's a simple example just like the one about the aquarium and the rock, which was VERY relevant. The rock feels no sideways force from the water because they are both moving together! You feel no sideways ("topskin") force from the wind because you are moving with it! The only way the rock would feel a force from the water (regardless of the shape of the rock or the density of the water) would be if it was somehow held still while the water was forced past it. Likewise, if the hand of God reached up from earth and held you still while 60mph wind passed you by, you'd feel it. But normally, there is no hand of God, and you are moving with the wind. You never know how fast you are moving until you see the ground, and regardless of what kind of dives you do, you are moving WITH the wind.

www.WingsuitPhotos.com

[kallend 2,146]

Quote

Likewise, if the hand of God reached up from earth and held you

You make it sound like this never happens to you!

...

The only sure way to survive a canopy collision is not to have one.

[dsbbreck 0]

I admit I'm not canopy pilot expert, and I debated on putting in my 2 cents, but since Canuck and I talked about this the other day and that is what ultimately brought up this discussion, here it goes.

I tend to agree with SBS over Hooknswoop for two reasons.

1. I have witnessed faster decent rates during a hook turns in high winds many many times.

2. Here's an analogy that might explain why. For those of you that have done any white water rafting this will make perfect sense.

First let me set this up.

Raft = Canopy. Front = Front, Left = Top, Right = Bottom.

Water speed = Wind Speed

If your in a raft in the middle of a river running 30mph downstream and your facing with the front of your raft upstream you will not reach the side of the river (shore = ground) any faster than you would if the water was moving 0 mph. This is because you are moving with the flow of the water.

This is the same as a canopy reacts in the wind in normal flight.

But... If you turn your raft to the right presenting the left side to the flow of the water, your raft will move to the side and reach the shore quicker.

The same holds true for the canopy. During a hook turn, you are presenting the top of your canopy to the wind just like presenting the side of your raft to the water flow. You will decend to the ground quicker in high wind vs no wind, just like the raft will reach the shore quicker in fast water vs still water.

I'm not a physics expert, but this is how I understand what I have witnessed personally, and I up for debate on this.

David

"Socrates wasn't killed because he had the answer.......he was killed because he asked the question."

[ianmdrennan 2]

The problem with your analogy is that it uses horizontal ground speed for reference. If the wind blew away or towards the earth it'd have the effect (towards the ground not actual airspeed) that you are describing.

Think of it this way if you were in a submarine and the water was flowing 30mph over you and you submerged, would you submerge faster if the water was flowing faster?

Blue skies
Ian

Performance Designs Factory Team

[dsbbreck 0]

Quote

Think of it this way if you were in a submarine and the water was flowing 30mph over you and you submerged, would you submerge faster if the water was flowing faster?

Yes!!!!

Let me edit this. Yes it would submerge faster, if it was nose down presenting the top of the submarine to the flow of the water.

David

"Socrates wasn't killed because he had the answer.......he was killed because he asked the question."

[dsbbreck 0]

Now would you like me to prove my point using my Sailing Analogy?

David

"Socrates wasn't killed because he had the answer.......he was killed because he asked the question."

[Hooknswoop 19]

Does snow fall slower if the wind is blowing?

Does a submarine rise faster if there is a current or not? (all other things being equal)

Can a bird descend or climb faster if there is wind? (no up-drafts/downdratfs)

Does an aircraft descend or climb faster if there is wind?

A raft anagoly doesn't work well because it isn't completely submerged in the medium, it is partially in one medium and partially in another.

If you swim underwater at a 90-degree abngle across a stream, it takes the same amount of time to reach the other side regardless if there is a current or not. If there is a current, you just end up on the other side of the stream down stream instead of directly across from where you started. The current accounts for the added distance covered over the stream bed.

If you point a Pilatus Porter straight down, 90-degrees to the ground in zero wind and a steady 30 mph wind, it will have the exact same descent rate. The difference will be it's ground track. In a straight down dive in zero wind, the Porter will have a ground track across the ground in the direction of the top of the wing. If there is wind, and the top of the wing is on the up-wind side, the wind will cancel out the aircraft's ground track, but the descent will be the same. If it rolls 180- degrees, it's ground track will be whatever it would be in no wind plus 30 mph.

The ground has zero effect on aerodynamics once you are out of ground effect.

Wind is measureed in refernce to speed the air moves over the ground. Air speed is measured in reference to the air mass the vehicle is flying through. The key is reference points. Wind "hitting the top of the wing" (a canopy diving with the top skin into the wind is not being hit by the wind) does not cancel out it's lift, only it's groundspeed that that lift would produce.

I have witnessed a Piper Cub flying backwards across the ground. It still had airspeed, but the wind was more than it's airspeed making it's ground speed negative.

Derek

[Hooknswoop 19]

Quote

Think of it this way if you were in a submarine and the water was flowing 30mph over you and you submerged, would you submerge faster if the water was flowing faster?

--------------------------------------------------------------------------------


Yes!!!!

Let me edit this. Yes it would submerge faster, if it was nose down presenting the top of the submarine to the flow of the water.

Why would it submerge faster?

What causes a submarine to submerge?

Would it submerge faster if it was doing 30 knots through calm water or 0 knots into a 30 knot current?

Derek

[dsbbreck 0]

Quote

Does snow fall slower if the wind is blowing?

A snowflake is symetrical and doesn't have the rectangular shape needed to change reletive to the wind in order to increase or decrease speed.

Does a submarine rise faster if there is a current or not? (all other things being equal)

I believe it does, but I guess we'd need to ask a submarine pilot


Can a bird descend or climb faster if there is wind? (no up-drafts/downdratfs)

I believe it can, but once again, we need to ask a bird.

Does an aircraft descend or climb faster if there is wind?

Most defenatly, this is proven every weekend when we climb over the mountains to use the wind
coming off the mountains to create more lift.

A raft anagoly doesn't work well because it isn't completely submerged in the medium, it is partially in one medium and partially in another.

You can't honestly believe that the low aspect of the raft can be affected that greatly by wind or any other force. The water is the biggest factor.

If you swim underwater at a 90-degree abngle across a stream, it takes the same amount of time to reach the other side regardless if there is a current or not. If there is a current, you just end up on the other side of the stream down stream instead of directly across from where you started. The current accounts for the added distance covered over the stream bed.

True, but change to a 45 degree angle and you'll get there quicker in a current.

If you point a Pilatus Porter straight down, 90-degrees to the ground in zero wind and a steady 30 mph wind, it will have the exact same descent rate. The difference will be it's ground track. In a straight down dive in zero wind, the Porter will have a ground track across the ground in the direction of the top of the wing. If there is wind, and the top of the wing is on the up-wind side, the wind will cancel out the aircraft's ground track, but the descent will be the same. If it rolls 180- degrees, it's ground track will be whatever it would be in no wind plus 30 mph.

Agreed, because it doesn't have the angle needed to use the wind to create a faster decent rate. Put it at a 45 degree angle instead of straight down and it will have a greater decent rate.

To justify both of the swimmer and porter arguments, you'd have to compare them to flying your canopy straight to the ground. Which, if you were doing that, I would agree that the wind would have no affect. It's the angle to the wind that created more speed.

The ground has zero effect on aerodynamics once you are out of ground effect.

Wind is measureed in refernce to speed the air moves over the ground. Air speed is measured in reference to the air mass the vehicle is flying through. The key is reference points. Wind "hitting the top of the wing" (a canopy diving with the top skin into the wind is not being hit by the wind) does not cancel out it's lift, only it's groundspeed that that lift would produce.

I have witnessed a Piper Cub flying backwards across the ground. It still had airspeed, but the wind was more than it's airspeed making it's ground speed negative.

Derek

David

"Socrates wasn't killed because he had the answer.......he was killed because he asked the question."