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Active runway = wind direction + ??

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Anonymous
June 12, 2005 5:05:17 PM

Archived from groups: alt.games.microsoft.flight-sim (More info?)

Alright....I've been digging through our archives, sifting through
rec.aviation posts also (I know...I'm a traitor! <g>), doing a lot of
reading....and I still have a hard time understanding this!
I guess I'll never get a pilots licence....good thing too, eh? :-)

Scenario:
--------------
A small island in the middle of nowhere, single runway (09/27), no
windsock, real weather on, vintage aircraft (Howard 500).

CTRL-Z info:
-----------------
WIND 180/04

Can you see where this is going? :-)


So I start up my engines, turn on my strobes and other lights, close the
door and look at the top of the screen: WIND 181/04
I figure with the wind being straight down the middle, it won't matter
which runway I use for t/o. So I dial in the traffic frequency, call out my
intentions, and begin to taxi to 27.
Just as I get into t/o position I notice the top of the screen displaying a
slight change: WIND 176/05
I figure a few degress aren't going to matter, so I begin the roll and lift
off a few seconds later. I noticed my bird being pushed around by the wind,
not much but enough to put the pilot to work, so I logged that information.

Just as I'm climbing out, reaching 4000ft, I noticed something coming
towards me....something small. I had just switched to the Center frequency
so I can't hear him transmitting (I could have switched back, but I was
flying manual for once), so I decide to turn around and watch this little
Skylane do his thing. Sure enough he landed on runway 09!

Keeping in mind that the FS AI isn't perfect....who was right? Me or him?


Oh....as I write this I'm approaching my destination, WIND 100/16, single
runway (08/26)....can you guess which runway I'll be landing on?

--

Marcel (SAG-21)
(Mmmmmm.....beer and doughnuts. - Homer Simpson)

More about : active runway wind direction

Anonymous
June 12, 2005 5:05:18 PM

Archived from groups: alt.games.microsoft.flight-sim (More info?)

Marcel Kuijper <zoepetier_nothing_here@hotmail.com> wrote:

> Keeping in mind that the FS AI isn't perfect....who was right? Me or him?

Several points to keep in mind:

1) In MSFS, it normally takes the AI aircraft about 10 to 15 minutes to get
caught up with the real weather downloads. In other words, AI aircraft
will initially be placed on approach to some runway that may or may not be
most aligned with the winds. Time will sort this out.

2) At uncontrolled airports, the pilot of each aircraft is the ultimate
authority as to what runway to land at. If the pilot sees an overriding
reason, he certainly can choose a runway opposite of the most aligned
winds. Obstacles and runway slope are two reasons that immediately come to
mind.

Certainly, though, courtesy and common sense prevail and if there are
aircraft in the pattern using a particular runway, it would be safest and
most courteous to fit into that pattern.

3) You mention someone inbound to your airport when you reach 4,000 feet.
Presumably, are you about 3,500 feet or so above the airport elevation? If
so, you are certainly no longer even close to being in the airports traffic
pattern altitude airspace. Thus, you, like every other aircraft, has a
primary responsibility to see and avoid. Period. No one is right in this
case. Just see and avoid. :-)

Also, there are many cases of VFR aircraft practicing IFR approaches to
airports that would have them come in from conceivably any heading. Again,
see and avoid applies here, including the VFR aircraft practicing or even
really flying an IFR approach.

4) Winds less than 180 degrees magnetic favor runway 9, not 27. This
simply means that if the winds were 174 (as in your example), the runway
with the most headwind component would be 9. So, technically, you were
departing on the runway with a tailwind component. Does this mean you were
wrong? Not if you first concluded that runway length, density altitude,
and loaded weight of your aircraft all allowed a safe tailwind departure.

I am based at a class C airport (Syracuse, NY), where its main runway is
over 9,000 feet long. My hangar is exactly at the approach end of this
main runway, runway 10. If there is a tailwind up to about 9 knots, I will
still ask for a departure off this runway to save me the long taxi to the
opposite end. In a Bonanza, the added runway length to liftoff is
inconsequential on this 9,000 foot runway.

Of course, ATC has ultimate authority to approve or deny my request,
depending on if there are other aircraft on approach to the opposite end,
but it's always worth it to ask.

--
Peter


















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Anonymous
June 13, 2005 1:03:11 AM

Archived from groups: alt.games.microsoft.flight-sim (More info?)

On Sun, 12 Jun 2005 11:42:21 -0400, Beech45Whiskey wrote:

> 2) At uncontrolled airports, the pilot of each aircraft is the ultimate
> authority as to what runway to land at. If the pilot sees an overriding
> reason, he certainly can choose a runway opposite of the most aligned
> winds. Obstacles and runway slope are two reasons that immediately come to
> mind.

How about take-off from an uncontrolled airport?


> 3) You mention someone inbound to your airport when you reach 4,000 feet.
> Presumably, are you about 3,500 feet or so above the airport elevation? If
> so, you are certainly no longer even close to being in the airports traffic
> pattern altitude airspace. Thus, you, like every other aircraft, has a
> primary responsibility to see and avoid. Period. No one is right in this
> case. Just see and avoid. :-)

Since I was climbing out after take-off (in a straight line I might add),
the last thing I expected was incoming traffic from the same side.
This made me wonder: was I taking off in the wrong direction or was the
Skylane approaching the wrong runway?
Yes I was around 4000ft above the airport elevation, but the Skylane was
coming down from his cruise altitude and it was heading towards me.
And that's what sparked this thread.

Okay...maybe I shouldn't have switched to the Center freq. so quickly.
From now on I'll stay on the Traffic freq. until I feel it's safe to
switch.


> Also, there are many cases of VFR aircraft practicing IFR approaches to
> airports that would have them come in from conceivably any heading. Again,
> see and avoid applies here, including the VFR aircraft practicing or even
> really flying an IFR approach.

Wouldn't that depend on the country this is taking place in?
At EHLE for instance (one north-south asphalt runway), the wind direction
decides from which way one should fly in and it's up to the controller to
inform the pilots what the wind direction is, so one doesn't fly in on 23
while the other is taking off from 5.


> 4) Winds less than 180 degrees magnetic favor runway 9, not 27. This
> simply means that if the winds were 174 (as in your example), the runway
> with the most headwind component would be 9. So, technically, you were
> departing on the runway with a tailwind component. Does this mean you were
> wrong? Not if you first concluded that runway length, density altitude,
> and loaded weight of your aircraft all allowed a safe tailwind departure.

We're talking about a few degrees deviation either way, so that by itself
shouldn't have that much effect on the plane....but I like what you're
saying. 0-179 degrees for runway 09 and 180-359 for runway 27.
Simpley use the same principles used to determine an even or odd cruise
altitude. I can remember that!
This problem should no longer be a factor!


> I am based at a class C airport (Syracuse, NY), where its main runway is
> over 9,000 feet long. My hangar is exactly at the approach end of this
> main runway, runway 10. If there is a tailwind up to about 9 knots, I will
> still ask for a departure off this runway to save me the long taxi to the
> opposite end. In a Bonanza, the added runway length to liftoff is
> inconsequential on this 9,000 foot runway.

Uhm....I gotta ask this....doesn't that go against all the training manuals
there are out there? When I first started simming (almost 6 years ago now!)
I read in the manuals that a certain amount of lift was necessary to get an
aircraft airborne. One can achieve this lift by taking off against the wind
(i.e. face first).

Taking off with a tail wind would give the aircraft a little extra speed,
but wouldn't it also force it more downward than upward?

--

Marcel (SAG-21)
(Q: What do you do when Stormtroopers look for you?
A: Lock the doors. And hope they don't have blasters!)
Related resources
Anonymous
June 13, 2005 1:19:24 AM

Archived from groups: alt.games.microsoft.flight-sim (More info?)

> Uhm....I gotta ask this....doesn't that go against all the training
> manuals there are out there? When I first started simming (almost 6
> years ago now!) I read in the manuals that a certain amount of lift
> was necessary to get an aircraft airborne. One can achieve this lift
> by taking off against the wind (i.e. face first).
>
> Taking off with a tail wind would give the aircraft a little extra
> speed, but wouldn't it also force it more downward than upward?

Taking off downwind will mean that you will take longer to get the requisite
airspeed over your wings to get you airborne. Flying is all about airspeed,
it is navigation that demands groundspeed.
If the runway is long enough, (and that is the pilot's responsibility to
check), you can certainly take off downwind. It is clearly more economic and
shorter to take off against the breeze. In a small or unmanned airstrip
there would be nothing to stop you taking off or landing with the wind if it
was more convenient or even wiser. I recall once at my club airfield doing a
very difficult landing on rwy 24 directly into the sunset completely
blinded. When I got down and said to the tower how difficult it had been,
the controller said, 'Why didn't you land downwind then with your back to
the sun?' I was very inexperienced at the time, and it did not occur to me
to go against common practice, but that it all it is, NOT a rule.


--
Cheers
Quilljar


Try 'Living With Technology' magazine
http://www.livtech.co.uk
June 13, 2005 1:28:55 AM

Archived from groups: alt.games.microsoft.flight-sim (More info?)

<snip>
> Uhm....I gotta ask this....doesn't that go against all the training
> manuals there are out there? When I first started simming (almost 6
> years ago now!) I read in the manuals that a certain amount of lift
> was necessary to get an aircraft airborne. One can achieve this lift
> by taking off against the wind (i.e. face first).
>
> Taking off with a tail wind would give the aircraft a little extra
> speed, but wouldn't it also force it more downward than upward?

<snip>

A tail wind will give an increased ground speed, but reduces the airspeed,
since the airspeed is a measure of the air flowing over the wing from front
to rear. Airspeed is the important one for flight, since that is the factor
that determines how much lift you've got. That's why a significant tail wind
is not good for takeoff, because it detracts from the lift.

However, as long as the aircraft can build enough airspeed in spite of that
tail wind (and the runway's long enough to build that speed), it's not
necessarily a problem. If the tail wind is too strong though, you're goung
to have a very high ground speed, which may not be a good idea if you've
still got wheels on the ground - planes are designed to be flown not driven,
so ground handling is best carried out at low speed!

For landing, you want to minimise ground speed, hence you tend to land into
the wind.

Tim
Anonymous
June 13, 2005 1:28:56 AM

Archived from groups: alt.games.microsoft.flight-sim (More info?)

Tim <void@invalidemail.com> wrote:

> A tail wind will give an increased ground speed, but reduces the airspeed,
> since the airspeed is a measure of the air flowing over the wing from front
> to rear. Airspeed is the important one for flight, since that is the factor
> that determines how much lift you've got. That's why a significant tail wind
> is not good for takeoff, because it detracts from the lift.

Absolutely not true. There is airflow relative to the ground, and airflow
relative to the wing. The two are different.

Discounting any gust factor, a tailwind's only disadvantage is that it
increases groundspeed of the aircraft. Increased groundspeed means
increased runway distance before the aircraft reaches proper liftoff, or
rotation speed.

This is what gets pilots into trouble when trying to takeoff downwind on a
shorter runway. Add a higher density altitude and maximum loading, and
there is your recipe for either going off the end of the runway or a pilot
panicking and attempting to lift off the aircraft before it is ready to
fly.

--
Peter


















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Anonymous
June 13, 2005 1:57:29 AM

Archived from groups: alt.games.microsoft.flight-sim (More info?)

>> Taking off with a tail wind would give the aircraft a little extra speed,
>> but wouldn't it also force it more downward than upward?
>
>No. Again, discounting gusts for this discussion (which can cause a type
>of windshear and can momentarily affect lift), a tailwind affects
>groundspeed, not relative wind across the airfoil.

A tailwind directly affects the relative wind across the airfoil.
That's why your groundspeed will be higher at the airspeed required for
takeoff. Conversely, a headwind means your groundspeed will be lower
at the same airspeed for takeoff (or landing).

>Thus, the aircraft's movement across the ground will be faster at the point
>where relative wind across the airfoil indicates proper rotation speed.

Correct. A tailwind affects relative wind. The groundspeed is a
consequence of this. Not at all to take away from your excellent
replies, but the two statements here seemed a little contradictory in
their wording.

Best regards, Kev
Anonymous
June 13, 2005 3:13:10 AM

Archived from groups: alt.games.microsoft.flight-sim (More info?)

Marcel Kuijper <zoepetier_nothing_here@hotmail.com> wrote:

> How about take-off from an uncontrolled airport?

Yes, the same applies when a pilot decides on which runway to depart, too.
The pilot is the PIC and ultimately responsible for using the runway at an
uncontrolled airport s/he concludes is the safest.

It is common at uncontrolled airports to have one longer runway and perhaps
one crossing runway that is much shorter. Or, in the case of my real world
across-the-US trip two weeks ago, flying into an airport with one long
paved runway and one crossing turf runway.

In either case it is conceivable that there could be one or more small
aircraft using the small paved or turf runway, whereas you are flying a
heavier, single or multi-engine aircraft that needs the longest paved
runway possible. Thus, no matter how many might be using the crossing
runway, you will choose to takeoff/land on the longer runway for the safety
of your flight.

I'll give you another example: A calm evening with winds 000 at 0 kts. I
was just taking the runway at an uncontrolled airport one evening when I
heard a commuter aircraft (Beech 1900) call that he was 10 miles out,
landing on the opposite runway as I was departing. As my aircraft began to
accelerate down the runway, I saw his landing lights come on in front of me
(albeit 10 miles off).

I simply re-iterated my call on unicom, stating that I was "on the roll on
runway xx, with a south departure, traffic approaching opposite runway in
sight" so that the commuter pilots were confident that I would turn away
from them soon after my departure.

> Since I was climbing out after take-off (in a straight line I might add),
> the last thing I expected was incoming traffic from the same side.
> This made me wonder: was I taking off in the wrong direction or was the
> Skylane approaching the wrong runway?

Neither. When that high (and speaking as if this were real life, rather
than limited AI aircraft), it is certainly conceivable that the Skylane
hadn't yet begun his maneuver for the traffic pattern of the runway from
which you just departed. Or, as I indicated, he may have been on a real or
practice instrument approach.

Nonetheless, neither of you would have been wrong, unless you banged into
each other. Then you both would have been faulted for failing to see and
avoid.

> Yes I was around 4000ft above the airport elevation, but the Skylane was
> coming down from his cruise altitude and it was heading towards me.
> And that's what sparked this thread.

There are no street signs in the sky. Aircraft can and do approach from
any direction, especially when considering climbing and descending
aircraft. I type it again, because it is so true: See and Avoid.

> Okay...maybe I shouldn't have switched to the Center freq. so quickly.
> From now on I'll stay on the Traffic freq. until I feel it's safe to
> switch.

Or, continue to monitor the unicom frequency with the second radio while
communicating with ATC on the first. However, listening to the radio does
not guarantee that you will have a totally correct picture, since there are
aircraft flying about legally that do not have radios (in class E or G
airspace, of course).

> Wouldn't that depend on the country this is taking place in?
> At EHLE for instance (one north-south asphalt runway), the wind direction
> decides from which way one should fly in and it's up to the controller to
> inform the pilots what the wind direction is, so one doesn't fly in on 23
> while the other is taking off from 5.

Now you are mixing controlled airports with uncontrolled airports. IIRC,
your primary question that started this thread pertained to uncontrolled
airports. The PIC determines what runway to use at uncontrolled airports,
based on several criteria, not the least of which is whether there are
other aircraft already in the pattern or not.

At controlled airports, wind direction *most often* determines runway in
use, but even that rule does have exceptions. For example, if the winds
were, say 5 knots straight down a runway, ATC could choose the opposite
runway if municipality noise abatement rules required them to do so. A 5
knot tailwind will not have any relative effect on a larger jet aircraft
and the runway length will more than compensate for smaller aircraft.

> We're talking about a few degrees deviation either way, so that by itself
> shouldn't have that much effect on the plane....

Nope, it shouldn't, but I was assuming by your example whether you were
wondering if headwind/tailwind components determined take-off direction. I
was simply pointing out that in your example, you had a tailwind component
when you departed runway 27, which may have contradicted what you believed
was the proper runway to use based on wind direction.

> but I like what you're
> saying. 0-179 degrees for runway 09 and 180-359 for runway 27.
> Simpley use the same principles used to determine an even or odd cruise
> altitude. I can remember that!
> This problem should no longer be a factor!

Sure, that problem works out cleanly for runways 09/27, but what about
single strip airports with runways 15/33? How about 1/19? The point is
that you may need to come up with a more generic rule of thumb for quickly
determining landing/takeoff direction strictly in a headwind, if that is
even possible.

I mentally calculate the headwind component by comparing the runway number
to the reported winds (if the uncontrolled airport has an AWOS/ASOS), or
quickly see the headwind/tailwind by observing the windsock/tee.

> Uhm....I gotta ask this....doesn't that go against all the training manuals
> there are out there?

There is the theory in training a primary student, and there is the
practicality in flying for several hundred/thousand hours.

Honestly, I do not know how to train someone to fly, so I couldn't answer
this with certainty (perhaps someday), but the problem with teaching a
primary student to NEVER take off in a tailwind scenario without explaining
the actual thought process behind the takeoff/landing runway decision is to
severely limit the student. I hope I have given you at least a few real
life reasons one may have to takeoff with a tailwind.

> When I first started simming (almost 6 years ago now!)
> I read in the manuals that a certain amount of lift was necessary to get an
> aircraft airborne. One can achieve this lift by taking off against the wind
> (i.e. face first).
>
> Taking off with a tail wind would give the aircraft a little extra speed,
> but wouldn't it also force it more downward than upward?

No. Again, discounting gusts for this discussion (which can cause a type
of windshear and can momentarily affect lift), a tailwind affects
groundspeed, not relative wind across the airfoil. Thus, the aircraft's
movement across the ground will be faster at the point where relative wind
across the airfoil indicates proper rotation speed.

The faster groundspeed results in more runway used up and this can be the
danger in taking off with a tailwind (considering short runways with
obstacles at the end). Lift is not affected.

--
Peter


















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June 13, 2005 9:23:55 AM

Archived from groups: alt.games.microsoft.flight-sim (More info?)

kdarling@basit.com wrote:

>>>Taking off with a tail wind would give the aircraft a little extra speed,
>>>but wouldn't it also force it more downward than upward?
>>
>>No. Again, discounting gusts for this discussion (which can cause a type
>>of windshear and can momentarily affect lift), a tailwind affects
>>groundspeed, not relative wind across the airfoil.
>
>
> A tailwind directly affects the relative wind across the airfoil.
> That's why your groundspeed will be higher at the airspeed required for
> takeoff. Conversely, a headwind means your groundspeed will be lower
> at the same airspeed for takeoff (or landing).
>
>
>>Thus, the aircraft's movement across the ground will be faster at the point
>>where relative wind across the airfoil indicates proper rotation speed.
>
>
> Correct. A tailwind affects relative wind. The groundspeed is a
> consequence of this. Not at all to take away from your excellent
> replies, but the two statements here seemed a little contradictory in
> their wording.
>
> Best regards, Kev
>

Was this a test? If it is answer 1 was correct as written.
"a tailwind affects groundspeed, not relative wind across the airfoil"


--

(Smiling) boB,
SAG 70

U.S. Army Aviation (retired)
Central Texas - 5NM West of Gray Army Airfield (KGRK)
Anonymous
June 13, 2005 10:11:32 AM

Archived from groups: alt.games.microsoft.flight-sim (More info?)

>Was this a test? If it is answer 1 was correct as written.
>"a tailwind affects groundspeed, not relative wind across the airfoil"

*laughing* Oh wait. We're saying the same thing, just differently.

>From one viewpoint, the answer is: the relative wind at takeoff speed
is always the same, but the groundspeed is higher.

OTOH, I'm pointing out that it's because the relative wind is against
you as you start your groundroll, then your groundspeed will have to be
higher to reach the equivalent takeoff airspeed..

Sorry for the confusion!
Cheers, Kev
Anonymous
June 13, 2005 4:19:13 PM

Archived from groups: alt.games.microsoft.flight-sim (More info?)

Hi,

It is not unusual to take off/land downwind, even at controlled
airports. At San Diego (KSAN) the controllers prefer runway 27, even
when light winds would favor runway 9. Only when the adverse wind gets
too high (or gusty) do they switch to 9. Also when the visibility gets
too low - 9 has the only ILS approach.

Hope this helps,

Tom Gibson

Cal Classic Propliner Page: http://www.calclassic.com

Cal Classic Alco Page: http://www.calclassic.com/alco

Freeflight Design Shop: http://www.freeflightdesign.com



Marcel Kuijper wrote:
> On Sun, 12 Jun 2005 11:42:21 -0400, Beech45Whiskey wrote:
>
>
>>2) At uncontrolled airports, the pilot of each aircraft is the ultimate
>>authority as to what runway to land at. If the pilot sees an overriding
>>reason, he certainly can choose a runway opposite of the most aligned
>>winds. Obstacles and runway slope are two reasons that immediately come to
>>mind.
>
>
> How about take-off from an uncontrolled airport?
>
>
>
>>3) You mention someone inbound to your airport when you reach 4,000 feet.
>>Presumably, are you about 3,500 feet or so above the airport elevation? If
>>so, you are certainly no longer even close to being in the airports traffic
>>pattern altitude airspace. Thus, you, like every other aircraft, has a
>>primary responsibility to see and avoid. Period. No one is right in this
>>case. Just see and avoid. :-)
>
>
> Since I was climbing out after take-off (in a straight line I might add),
> the last thing I expected was incoming traffic from the same side.
> This made me wonder: was I taking off in the wrong direction or was the
> Skylane approaching the wrong runway?
> Yes I was around 4000ft above the airport elevation, but the Skylane was
> coming down from his cruise altitude and it was heading towards me.
> And that's what sparked this thread.
>
> Okay...maybe I shouldn't have switched to the Center freq. so quickly.
> From now on I'll stay on the Traffic freq. until I feel it's safe to
> switch.
>
>
>
>>Also, there are many cases of VFR aircraft practicing IFR approaches to
>>airports that would have them come in from conceivably any heading. Again,
>>see and avoid applies here, including the VFR aircraft practicing or even
>>really flying an IFR approach.
>
>
> Wouldn't that depend on the country this is taking place in?
> At EHLE for instance (one north-south asphalt runway), the wind direction
> decides from which way one should fly in and it's up to the controller to
> inform the pilots what the wind direction is, so one doesn't fly in on 23
> while the other is taking off from 5.
>
>
>
>>4) Winds less than 180 degrees magnetic favor runway 9, not 27. This
>>simply means that if the winds were 174 (as in your example), the runway
>>with the most headwind component would be 9. So, technically, you were
>>departing on the runway with a tailwind component. Does this mean you were
>>wrong? Not if you first concluded that runway length, density altitude,
>>and loaded weight of your aircraft all allowed a safe tailwind departure.
>
>
> We're talking about a few degrees deviation either way, so that by itself
> shouldn't have that much effect on the plane....but I like what you're
> saying. 0-179 degrees for runway 09 and 180-359 for runway 27.
> Simpley use the same principles used to determine an even or odd cruise
> altitude. I can remember that!
> This problem should no longer be a factor!
>
>
>
>>I am based at a class C airport (Syracuse, NY), where its main runway is
>>over 9,000 feet long. My hangar is exactly at the approach end of this
>>main runway, runway 10. If there is a tailwind up to about 9 knots, I will
>>still ask for a departure off this runway to save me the long taxi to the
>>opposite end. In a Bonanza, the added runway length to liftoff is
>>inconsequential on this 9,000 foot runway.
>
>
> Uhm....I gotta ask this....doesn't that go against all the training manuals
> there are out there? When I first started simming (almost 6 years ago now!)
> I read in the manuals that a certain amount of lift was necessary to get an
> aircraft airborne. One can achieve this lift by taking off against the wind
> (i.e. face first).
>
> Taking off with a tail wind would give the aircraft a little extra speed,
> but wouldn't it also force it more downward than upward?
>
June 13, 2005 5:49:59 PM

Archived from groups: alt.games.microsoft.flight-sim (More info?)

Beech45Whiskey wrote:
> Tim <void@invalidemail.com> wrote:
>
>> A tail wind will give an increased ground speed, but reduces the
>> airspeed, since the airspeed is a measure of the air flowing over
>> the wing from front to rear. Airspeed is the important one for
>> flight, since that is the factor that determines how much lift
>> you've got. That's why a significant tail wind is not good for
>> takeoff, because it detracts from the lift.
>
> Absolutely not true. There is airflow relative to the ground, and
> airflow relative to the wing. The two are different.
>
> Discounting any gust factor, a tailwind's only disadvantage is that it
> increases groundspeed of the aircraft. Increased groundspeed means
> increased runway distance before the aircraft reaches proper liftoff,
> or rotation speed.
>
> This is what gets pilots into trouble when trying to takeoff downwind
> on a shorter runway. Add a higher density altitude and maximum
> loading, and there is your recipe for either going off the end of the
> runway or a pilot panicking and attempting to lift off the aircraft
> before it is ready to fly.

Am I really "absolutely" wrong? A tailwind must reduce the airspeed, unless
I am horribly mistaken...

The airspeed referred to in flying is a measure of the airflow relative to
the wing (from front to rear), so if the aircraft is stationary and pointing
into a 30kt wind, you have effectively 30kts of airspeed standing still.
Start moving the plane forward and you add the forward speed component of
the aircraft to that to get your total airspeed. Hence by taking off or
landing into the wind you do so with a reduced ground speed. If you have a
30kt tailwind, doesn't that mean you've got to be going 30kts along the
ground just to get any forward airflow over the wing? I accept that this may
be a simplification, but I don't believe it's that far off the mark.

Tim
June 14, 2005 12:12:28 AM

Archived from groups: alt.games.microsoft.flight-sim (More info?)

kdarling@basit.com wrote:
>>Was this a test? If it is answer 1 was correct as written.
>>"a tailwind affects groundspeed, not relative wind across the airfoil"
>
>
> *laughing* Oh wait. We're saying the same thing, just differently.
>
>>From one viewpoint, the answer is: the relative wind at takeoff speed
> is always the same, but the groundspeed is higher.
>
> OTOH, I'm pointing out that it's because the relative wind is against
> you as you start your groundroll, then your groundspeed will have to be
> higher to reach the equivalent takeoff airspeed..
>
> Sorry for the confusion!
> Cheers, Kev
>

I think it's just a matter of definition I guess. Relative wind is
parallel and opposite the direction of the airfoil. So some may say, and
I believe, Relative Wind does not occur until the airfoil is actually
moving forward (against) the wind. Anything else is just airflow over an
airfoil. When you get to Resultant Relative Wind, it gets complicated.
Not only is a rotor blade moving forward on the advancing side and the
retreating blade is moving aft, but still forward into the Relative
wind. You still have to factor in flapping, feathering, hunting (fully
articulated rotor system - eg. TH-55) and induced flow (the blades
change the direction of the Relative Wind simply because the rotor
system is pulling the air downward as it maintains lift.

I know that's over-simplified but you can read about it if you wish.
There are many web sites, use google to find more.

http://www.dynamicflight.com/aerodynamics/relative_wind...


It also depends on which type of rotor system you are flying:
Rigid, Semi-ridged, or Articulated

http://www.centennialofflight.gov/essay/Dictionary/heli...
--

(Smiling) boB,
SAG 70

U.S. Army Aviation (retired)
Central Texas - 5NM West of Gray Army Airfield (KGRK)
Anonymous
June 14, 2005 10:30:13 AM

Archived from groups: alt.games.microsoft.flight-sim (More info?)

Marcel wrote:

> Well....when AWOS/ASOS isn't available, and you're still a couple of miles
> out, I can only guess that one would have to circle the airport until a
> visual of the windsock gives the pilot the information he's looking for.
> Or he/she could ask pilots in the area if they know.

If the uncontrolled airport does not have ASOS/AWOS, the first thing
the pilot would probably do is monitor the unicom frequency to see of
there are other radio-equipped aircraft in the pattern. If so, this
will most likely give the pilot the most wind-favorable runway.

If there is no activity on Unicom, the next preferable option is to
call unicom while still out and ask for an airport advisory. "Podunk
Unicom, Cessna 123, two-five miles to the northwest, requesting airport
advisory, Podunk." If someone is manning the unicom radio, that person
should respond with something like, "Cessna 123, Podunk Unicom, winds
favor runway 32, no traffic in the pattern."

However, it is possible that there might be no one at the radio, so the
final option is to then overfly the airport at 500 feet above traffic
pattern altitude to observe the windsock as well as the traffic pattern
for no-radio (NORDO) aircraft.

> That is...if the pilot in question even cares about something so trivial.

I apologize if I left you with the impression that wind direction is
trivial, because at a smaller, uncontrolled airport with typically
shorter, narrower runways the wind direction is very important. Many
accidents have occurred with wind as a contributing factor at these
types of airports.

> I'm considering taking MLA lessons some time next year,

What are MLA lessons? Micro-light aircraft? Whatever type of
aircraft it is, definitely pursue those lessons when you can. Life is
too short to sit on the sidelines! :) 

> Thanks again!

You are welcome.

--
Peter
Anonymous
June 14, 2005 11:45:04 AM

Archived from groups: alt.games.microsoft.flight-sim (More info?)

Tim wrote:

> Am I really "absolutely" wrong? A tailwind must reduce the airspeed, unless
> I am horribly mistaken...

OK, so perhaps "absolutely" is too harsh. :) 

Based on my understanding (which comes from an active general aviation
background) I would disagree with the above quote, and would prefer it
to read: "A tailwinds requires more *groundspeed* to overcome."

--
Peter
Anonymous
June 14, 2005 4:04:00 PM

Archived from groups: alt.games.microsoft.flight-sim (More info?)

Uncontrolled airport = all runways are considered active. There may be a
"wind is favoring...." type of deal, but all r/w's are active. So you are
both right... see and avoid springs to mind. Oh and don't switch to dentre
until out of the terminal area.

- Barney
"Marcel Kuijper" <zoepetier_nothing_here@hotmail.com> wrote in message
news:uy9gp53bgnce$.1hsdgkufccrr1$.dlg@40tude.net...
>
> Alright....I've been digging through our archives, sifting through
> rec.aviation posts also (I know...I'm a traitor! <g>), doing a lot of
> reading....and I still have a hard time understanding this!
> I guess I'll never get a pilots licence....good thing too, eh? :-)
>
> Scenario:
> --------------
> A small island in the middle of nowhere, single runway (09/27), no
> windsock, real weather on, vintage aircraft (Howard 500).
>
> CTRL-Z info:
> -----------------
> WIND 180/04
>
> Can you see where this is going? :-)
>
>
> So I start up my engines, turn on my strobes and other lights, close the
> door and look at the top of the screen: WIND 181/04
> I figure with the wind being straight down the middle, it won't matter
> which runway I use for t/o. So I dial in the traffic frequency, call out
> my
> intentions, and begin to taxi to 27.
> Just as I get into t/o position I notice the top of the screen displaying
> a
> slight change: WIND 176/05
> I figure a few degress aren't going to matter, so I begin the roll and
> lift
> off a few seconds later. I noticed my bird being pushed around by the
> wind,
> not much but enough to put the pilot to work, so I logged that
> information.
>
> Just as I'm climbing out, reaching 4000ft, I noticed something coming
> towards me....something small. I had just switched to the Center frequency
> so I can't hear him transmitting (I could have switched back, but I was
> flying manual for once), so I decide to turn around and watch this little
> Skylane do his thing. Sure enough he landed on runway 09!
>
> Keeping in mind that the FS AI isn't perfect....who was right? Me or him?
>
>
> Oh....as I write this I'm approaching my destination, WIND 100/16, single
> runway (08/26)....can you guess which runway I'll be landing on?
>
> --
>
> Marcel (SAG-21)
> (Mmmmmm.....beer and doughnuts. - Homer Simpson)
Anonymous
June 14, 2005 6:09:22 PM

Archived from groups: alt.games.microsoft.flight-sim (More info?)

Marcel wrote:

> Why not use runway 9's ILS backcourse?

Most localizers (the glideslope is not part of a backcourse approach)
are not used from the opposite end. In order to be a legal approach,
the localizer backcourse has to be a published approach (in other
words, it has been test flown by the goverment and proven to meet many
approach-safe criteria). I am not 100% certain as to why most
localizers are not used from the backside, but I would suspect that
man-made obstacles and terrain at the opposite approach end play a role
in this decision.

With all of that mentioned, San Diego does offer a localizer (not a
backcourse, however) approach to rwy 27. No glideslope is offered
here most likely due to much greater slope needed to clear the hills
and buildings just east of the approach end of rwy 27.

The difference in ceiling minimums between the localizer 27 and the ILS
9 approach is a difference of about 300 feet (660 compared to 335 MSL).
Knowing the "marine" layer" that often sets up over San Diego, I would
speculate that even this 300 feet would mean the difference between
getting into the airport and having to go missed. Hence the preference
for ATC to use the ILS rwy 9 in low weather unless the winds are really
strong out of the west.

--
Peter
Anonymous
June 15, 2005 12:47:53 AM

Archived from groups: alt.games.microsoft.flight-sim (More info?)

On 14 Jun 2005 06:30:13 -0700, Beech45Whiskey wrote:

>> I'm considering taking MLA lessons some time next year,
>
> What are MLA lessons? Micro-light aircraft? Whatever type of
> aircraft it is, definitely pursue those lessons when you can. Life is
> too short to sit on the sidelines! :) 

Yep.
It's either that or Ultra Lights. At least the Micro Lights *look* like
airplanes instead of scooters with wings...propelled hanggliders...

MLA lessons are a lot cheaper than RPL and PPL lessons and without the
hassle of being required to fly 60 hours per year to keep your licence.
Just 12 hours for MLA pilots and two 1 hour flights with an instructor to
make sure you're still up to it. No age restrictions. Just a clean medical
record. So that's definately on the list for next year.

--

Marcel (SAG-21)
(Any landing you walk away from wasn't one of Melissa's! <g>)
Anonymous
June 15, 2005 12:49:48 AM

Archived from groups: alt.games.microsoft.flight-sim (More info?)

On Mon, 13 Jun 2005 12:19:13 -0700, Tom Gibson wrote:

> It is not unusual to take off/land downwind, even at controlled
> airports. At San Diego (KSAN) the controllers prefer runway 27, even
> when light winds would favor runway 9. Only when the adverse wind gets
> too high (or gusty) do they switch to 9. Also when the visibility gets
> too low - 9 has the only ILS approach.

Tom,

Why not use runway 9's ILS backcourse?
(hmmm...there's something wrong with that sentence <g>)

Probably a stupid question, but I am a bit tired....

--

Marcel (SAG-21)
(life is a tricky thing...I'm glad I'm good at it!)
June 15, 2005 1:42:40 AM

Archived from groups: alt.games.microsoft.flight-sim (More info?)

Marcel Kuijper wrote:

>
> Yep.
> It's either that or Ultra Lights. At least the Micro Lights *look* like
> airplanes instead of scooters with wings...propelled hanggliders...
>

Hi Marcel,

But remember, the purpose is to fly. Personally I wouldn't care if it
was a 3 axis (airplane look-a-like) microlight or a powered para-glider
or parachute. I would rather fly something a bit faster but all in all,
it's still flying.

--

(Smiling) boB,
SAG 70

U.S. Army Aviation (retired)
Central Texas - 5NM West of Gray Army Airfield (KGRK)
June 15, 2005 2:57:25 PM

Archived from groups: alt.games.microsoft.flight-sim (More info?)

Beech45Whiskey wrote:
> Tim wrote:
>
>> Am I really "absolutely" wrong? A tailwind must reduce the airspeed,
>> unless I am horribly mistaken...
>
> OK, so perhaps "absolutely" is too harsh. :) 
>
> Based on my understanding (which comes from an active general aviation
> background) I would disagree with the above quote, and would prefer it
> to read: "A tailwinds requires more *groundspeed* to overcome."

Peter,

I admit my flying activities IRL have been nil since 1992, so I don't mind
being picked up by someone more current ;) 

Even so, I felt the urge to pick up my copy of The Air Pilot's Manual by
Trevor Thom (The Aeroplane Technical), for my own peace of mind...

"An aeroplane stopped at the end of the runway and facing into a 20kt
headwind is already 20kt closer to the lift-off speed compared to the
nil-wind situation. A 10kt tailwind would worsen the situation considerably,
as the aircraft would have to accelerate to a groundspeed of 10kt before it
had an airspeed of zero."

This is what I was trying to say; I wasn't suggesting that the tailwind
increased the groundspeed, but rather that as a consequence of the tailwind,
the aircraft would have a higher groundspeed for a given airspeed. Mind you,
reading my original post, I can see how I might have worded it better;
that's what comes of posting to NGs when I should be tucked up in bed!

Tim
Anonymous
June 16, 2005 2:14:51 AM

Archived from groups: alt.games.microsoft.flight-sim (More info?)

On Tue, 14 Jun 2005 21:42:40 GMT, boB wrote:

> But remember, the purpose is to fly. Personally I wouldn't care if it
> was a 3 axis (airplane look-a-like) microlight or a powered para-glider
> or parachute. I would rather fly something a bit faster but all in all,
> it's still flying.

I'm surprised at how fast some of these Micro Lights can go.
The one I saw, the type I would be taking lessons in, has a maximum speed
of 240 km/h (150 mph).

Travelling through Europe (actually over Europe) in a rented MLA already
sounds a lot more adventurous than driving, eventhough pulling over for a
snack or to take a leak is out of the question. :-)

--

Marcel (SAG-21)
(Gear up, AP engaged...hey...what's that emergency light?)
June 16, 2005 2:14:52 AM

Archived from groups: alt.games.microsoft.flight-sim (More info?)

Marcel Kuijper wrote:
> pulling over for a snack or to take a leak is out of the question. :-)


I really don't see your dilemma Studmuffin......... Pack a few Twinkies
and the other problem is solved with a small funnel and piece of fuel
line...
d:->))
Anonymous
June 17, 2005 2:00:59 AM

Archived from groups: alt.games.microsoft.flight-sim (More info?)

On Wed, 15 Jun 2005 17:45:49 -0500, CRaSH wrote:

> I really don't see your dilemma Studmuffin......... Pack a few Twinkies
> and the other problem is solved with a small funnel and piece of fuel
> line...
> d:->))

I just remembered something....there are more professional solutions that
take the place of funnels and fuel lines...or empty bottles for that
matter. :-)

But one problem still remains, my good man....we don't have Twinkies here.
Lord knows I've looked for em!
I'll just pack a cooler and fill it with a few beers and turkeysandwiches.
It'll be just like going to a race! ;-)

--

Marcel (SAG-21)
(That's no moon...it's a space station!)
!