Comments

You must log in or register to comment.

Senna_65 t1_isqljlx wrote

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

87

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.

15

darrellbear t1_isrhg1z wrote

This is why aircraft carriers turn into the wind when launching or landing aircraft.

5

kdogg8 t1_isrgocj wrote

If a car T-Bones the side of your car, do you say you ran into the other car? Cross wind can be at a 90° angle to the runway heading.

3

eaglescout1984 t1_isrj5cb wrote

And at major airports, they pretty much make runways one way so they can line up take offs and landings. If the wind shifts, they just have to deal with it.

−3

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

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.

16

Reddit_Is_Bollox t1_iss8r1b wrote

So what are you saying - the airplane-on-a-treadmill does work or doesn't work?

1

RandoCalrissian11 t1_issi7db wrote

The reply made it seem like they thought the treadmill wouldn’t work, but the reply was correct saying the treadmill is irrelevant in the equation.

1

corrado33 t1_issxase wrote

The treadmill would NOT stop an airplane from taking off is the point I'm making.

1

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

danielcw189 t1_ist4rsy wrote

Put a plane on a treadmill in the normal world. let the plane try to take off. It will.

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

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

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

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

PizzaQuest420 t1_isr9dng wrote

i've never heard of this idea, do you talk to a lot of little kids or something?

−6

tsunami141 t1_isrjwzc wrote

> do you talk to a lot of little kids or something?

I think it’s more like physics nerds lol

2

AirborneRodent t1_isrmobc wrote

It's an old meme from 2007 or so. It's up there with the blue/black dress on the list of memes that caused the most arguments on the internet.

1

nrin005 t1_isruajz wrote

This is a very very common question online

1

OldMork t1_isqbuhl wrote

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

23

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

RedSonGamble t1_isqj5cb wrote

The opposite as when I ride my bike

4

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

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_isr8tqm wrote

If the wind is behind you, you would come in to fast and overshoot your landing point.

1

twinn5 t1_isrjf6f wrote

Aircraft carriers turn into the wind for launch and recovery.

4

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

black_flag_4ever t1_isr09s7 wrote

Preposterous, everyone knows that they use fairy dust.

1

rededelk t1_isslw86 wrote

Nice Einstein bot

1

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

RonSwansonsOldMan t1_isu1qt9 wrote

I'm older now, and still running...against the wind.

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

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

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

_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

sparky22- t1_isr40ib wrote

What if their is no wind

−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

Bo_Jim t1_isr8cug wrote

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

−1

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

swolypinger t1_it0aczm wrote

Not necessarily. I had never considered it before flight school so I just assumed a tailwind would help you get up to speed faster when taking off.

2

[deleted] t1_istsjcy wrote

[deleted]

−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

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

[deleted] t1_isqrpy0 wrote

[deleted]

−17

son_et_lumiere t1_isr2nmo wrote

I feel like a lot of airports have runways that are perpendicular to each other, so they can choose to use the E<->W or N<->S depending on how the winds are.

7

Positive-Source8205 t1_isr6nod wrote

Airports are designed with runways oriented to the prevailing wind direction for that location.

5

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

Goalie_deacon t1_isr3naa wrote

I’m sure they can’t land north/south on a east/west runway.

However there are runways that can rotate 360 degrees. They’re called aircraft carriers.

−4

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

AvNerd-Dispr t1_isqe7ix wrote

Incorrect. Headwinds improve performance, short distance required, and lower the Vr (speed at which rotation is initiated). Tailwinds, even for big jets, have HUGE performance penalties.

16

Nokneemouse t1_isqkbmc wrote

They rotate at a given airspeed, which doesn't change, they just have a head start getting there due to wind speed.

1

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

Nokneemouse t1_isqomm7 wrote

I mean that the VR is set for a given configuration of the aircraft.

3

son_et_lumiere t1_isr2whw wrote

Who or what does all the calculations that tells you how fast you have to go within what distance?

1

Good-Cardiologist679 t1_isr920e wrote

A flight planner, it’s someone’s job to crunch numbers for the pilot, but now pilots use ipads and etc and they have flight planning apps like foreflight that tell you all the info you need.

2

son_et_lumiere t1_israjdd wrote

I would have to assume the flight planner is in the cockpit with them, to account for changing variables in real time? Also, do they still exist in case like the iPads break or malfunction or something?

−1

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

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

ChevExpressMan t1_isqiapw wrote

You mean only for takeoff. Otherwise tailwind help the jet in flight.

−1

ChuckChuckelson t1_isqf33b wrote

you are right I meant to point out its less important for jets hat have two mile of runway

−8

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