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OldMork t1_isqbuhl wrote

same as parents school commute, against the wind, uphill and fighting bears, every single day.

23

ChuckChuckelson t1_isqcgku wrote

unless they are big jets, then it doesn't matter. Landing/Takeoff distance is more important than speed. Into the wind shortens distance.

−18

ChevExpressMan t1_isqhs81 wrote

That's normal knowledge, and I'm no pilot. You always look for the orange sock to determine direction. That's usually at small airports.

−12

RedSonGamble t1_isqj5cb wrote

The opposite as when I ride my bike

4

AvNerd-Dispr t1_isqjf6t wrote

Depends on the jet and how much payload and fuel it’s carrying. Also depends on the airport, altitude, temperature, obstacle clearance requirements, etc. I have planned and dispatched 777’s off 13000’ runways where we were bumping cargo to other flights due to poor takeoff performance.

Runway length is only 1 piece of a very complicated formula for determining payload allowed, its called Runway Allowable Takeoff Weight, or RATOW - this number can be higher than structural, in which case structural would be the weight limit, or it can be much lower depending on a whole host of factors, in addition to the length of the runway and the amount of headwind or tailwind.

6

FLTDI t1_isqjs52 wrote

A 10 kt wind would mean you need to have 20kts more groundspeed to have the same airspeed. You'll eat up that runway much quicker with a tailwind.

And 15 to 20 kts at an airport can be common, impacting ground speeds by 30 to 40 kts, which is not incidental.

1

Senna_65 t1_isqljlx wrote

They try to, but not necessary..and sometimes it's just impossible...gotta love crosswind landings!

87

AvNerd-Dispr t1_isqn86d wrote

As a pilot and someone who plans these numbers for dozens of flights on passenger jets everyday at work, I can confirm that the Vr is not static. It changes based on weight, flap/slat configuration, headwind/tailwind, temperature, ambient pressure, location of the CG… all of it affects the V speeds and they do very much change.

6

corrado33 t1_isqrph2 wrote

Fun fact: This is also somewhat related to why the "airplane on a treadmill" idea would never work.

Airplanes don't care about groundspeed, only airspeed. (At least, in terms of "can this airplane maintain altitude/take off.")

So long as the wheels were properly lubricated, the plane wouldn't really notice the treadmill under it and would take off like the treadmill wasn't there regardless.

Propellers push the airplane through the AIR, not along the ground. The fact that the airplane happens to be sitting on the ground at the time is of no consequence.

34

Cold_Situation_7803 t1_isqwxbi wrote

No, the runway can be landed on in either direction. An East/west runway will have you land into the west if the wind favors that; if the winds changes direction enough, the airport will begin landing towards the east.

4

black_flag_4ever t1_isr09s7 wrote

Preposterous, everyone knows that they use fairy dust.

1

OnionTruck t1_isr1rn7 wrote

I learned this at 10 years old when I learned that aircraft carriers go to full speed into the wind when conducting flight operations.

0

ppitm t1_isr2nro wrote

Imagine if you were trying to land with a strong wind behind you. A big gust of 40-50 kts could easily drop you down below stall speed and crash the plane.

4

draftstone t1_isr3osh wrote

Next time people someone talks to you about this, ask him why a floatplane can takeoff if it has no wheels. What makes contact to the ground has no effect other than possibly slowing you down due to friction.

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sparky22- t1_isr40ib wrote

What if their is no wind

−1

Bo_Jim t1_isr8cug wrote

In both cases, it's to increase lift vs. speed.

−1

CADnCoding t1_isr9xhs wrote

That’s exactly what happened to the crew of the C130 fighting fire in Australia a couple years ago. Coming in at a little over 100 knots for a retardant drop and a huge tail wind. Pilots earlier in the day were reporting 70 knot tail winds. Stalled and went down.

RIP Tanker 134 and crew.

7

Good-Cardiologist679 t1_israwnc wrote

No. A flight planner is in a remote location. Theres a pilot and co pilot. Theres 2 tablets and the plane has built in gps, weather radar, navaids etc in it. Anything in the air is up to the pilots flying to make decisions

2

Iz-kan-reddit t1_isrd5b3 wrote

>They try to, but not necessary..and sometimes it's just impossible...gotta love crosswind landings!

They're still landing into the wind, just not parallel to the runway.

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twinn5 t1_isrjf6f wrote

Aircraft carriers turn into the wind for launch and recovery.

4

kbielefe t1_isrkuiy wrote

I used to work across the street from a small airport. You could often tell when a storm was coming because the car alarms would go off in the parking lot, due to planes at full throttle taking off over the parking lot, due to shifting wind direction.

6

batatatchugen t1_isrlmmx wrote

Considering that it's wind speed that matters when talking about generating lift for an airplane, it's kinda obvious that this would be the desirable condition to land and takeoff, no?

−1

thebedla t1_issb0l8 wrote

Which is why aircraft carriers steam into the wind when launching and recovering aircraft. Adding the ship's speed and wind speed to "ground" speed makes takeoff shorter and effectively makes the landing strip longer.

3

Yak_52TD t1_issbqcl wrote

Birds do too. If fleeing a predator, they take off into wind and then immediately turn with the wind to escape as quick as possible.

2

AvNerd-Dispr t1_issgdu0 wrote

For a commercial operation, the aircraft dispatcher. For a private pilot flying on their own, the pilot is responsible. Charter operations vary, its the pilots responsibility but some choose to hire flight planners and/or dispatchers as well and the responsibility is delegated to them.

The numbers and charts are found in the airplane manual for small aircraft, for commercial jets a separate manual is generally produced for the performance charts; my airline calls it the Operations Data Manual, or ODM. Our engineering team has gone through the ODM and coded all of the numbers into our flight planning system, so that as we plan the flight and update items like passenger count and the weights for checked bags and cargo, the system automatically updates and displays the numbers for those conditions for us to cross check and verify.

1

This_one_taken_yet_ t1_issujr4 wrote

It's air moving over the wings that generates lift. The real speed of the plane is irrelevant for this. Think about birds at the beach on a windy day. They can essentially hover in the air because the wind is enough to generate the lift they need to stay in flight.

0

stu8018 t1_isszw4v wrote

Airspeed not groundspeed. Groundspeed is irrelevant.

0

Admetus t1_ist33xj wrote

As long as airspeed is high enough. Put a plane on a treadmill in a wind tunnel I'm sure it can take off.

It's probably a gap in education regarding physics making people assume that relative ground speed has anything to do with taking off.

1

pjabrony t1_ist70za wrote

Much like the Monty Hall Problem, the "airplane-on-a-treadmill" problem creates controversy because of how the problem is defined.

If you had a proper runway of proper runway length, but you turned it into a treadmill, that would not affect the takeoff of the airplane because it doesn't care how fast its wheels are spinning for takeoff purposes.

But, if you just had a treadmill the length of the airplane and you tried to use that to allow the airplane to get up to speed so it could take off without a long runway, that would not work.

1

_Sebaceous_cyst t1_ist93o5 wrote

Yes and it’s also called a headwind and a tailwind. Both of these influences take off and landing.

0

whitelightnin1 t1_istk8tm wrote

Tailwind increases airspeed. Headwind reduces airspeed but makes it easier to take off. Tailwind is favorable only during travel. Headwind is favorable during landing as well for the same reason. It slows the plane down and they don't need as much runway to land.

1

Doggydog123579 t1_isu56qh wrote

The second interpretation does not make physical sense as the plane will immediately leave the treadmill. The only way to make that short of treadmill work is to put it in a wind tunnel, at which point the airplane takes off anyways.

It creates controversy because people think the wheels are important to it moving, not because of the treadmill size.

1

Doggydog123579 t1_isu6e1t wrote

Absolutely wrong. Wake turbulance is always an issue regardless of the wind direction. Even on a day with a perfect headwind you leave a space between flights to allow the wake turbulance to disappear. The reason stated in the OP is the entire reason we take off into the wind, and it has been that way since the Wright Brothers, where the turbulance left behind was effectively negligible.

2

pjabrony t1_isu9abt wrote

> The second interpretation does not make physical sense as the plane will immediately leave the treadmill.

I understand that, but I think not everyone does which is why there's a question.

Put it this way: if you put a car on a treadmill, which does operate by the wheels' grip on the road, and you spun the wheels and the treadmill up to high speed, the car wouldn't have gone anywhere. Then say you quick-stop the treadmill. Would the car take off at a high speed? Could you get a lower zero-to-sixty time this way?

1

Doggydog123579 t1_isvii8c wrote

Then they take off on whatever runway they want, preferably the one pointing closest to their destination. Runways are long enough you can take off and land without a headwind, the wind just makes it a little easier.

1

Will12239 t1_isyl52a wrote

Not always. I was on a flight last month that took off with the wind. I was very surprised when I saw the wind sock while turning onto the runway. Probably much safer to do with powerful airliner engines compared to GA engines.

1

swolypinger t1_it09zil wrote

Most likely the wheels wouldn't have enough grip at high rpms to do anything other than wheelspin until they had slowed down a bit.

That's the same reason f1 drivers dont just slam on the gas at the statt of a race, they would just burnout and go nowhere

1