How do you know how fast a plane is going?

Question

How do you know how fast a plane is going?

Answer 1

I like Thudley's and Craig's answers.

Indicates Airspeed (IAS) is a measure of an aircraft's movement through the air.  Groundspeed (GS) is IAS corrected for headwind or tailwind component.

Most of the time, I look at ground speed, if I want to know how fast a plane is going.  I do that, because it tells me how long it will take to get to a destination, and that's important in calculating fuel consumption.

Hope that helps.  Good answers Thudley and Craig....

Answer 2

You ask the pilot!

Answer 3

There are special instruments for that purpose.

You can know about them in www.wikipedia.org

Answer 4

Indicated airspeed is displayed on the airspeed meter.

True airspeed is displayed on some airspeed meters.

Groundspeed is displayed by RNAV equipment.

Groundspeed is displayed on ATC radars.

Groundspeed can be calculated from the time interval across a known distance

Groundspeed is not IAS corrected for headwind component.  Computation of groundspeed involves the TAS component in the direction of the track, and the headwind component.

Mach .76 is a TAS parameter.

Answer 5

the speedometer.

Answer 6

When you try to use the outside toilet but can't push the door open.

Answer 7

Craig.allan07

I think it is just possible you got your calculations the wrong way round.

Answer 8

by looking at the acceleration screen when your flying

Answer 9

As many answers have already provided great examples of how the Pitot tube reads airspeed, I won't cover that for you.  But, that will only tell you the airspeed.  Using some math, you could figure out that every 1000 feet in altitude over sea level, you were going 2% faster (due to the less dense air).  Still, that means winds should be calm to be accurate (and density of air should decrease linearly as you rise).  How often is that the case?

Airspeed is probably not what you want to know, because it won't tell you when you're going to get there.  In the old days, these answers were pretty much all that was available though.  But, what about that head wind, tail wind, or cross wind impact on your speed?

Autopilot devices would measure the distance to VOR and tell you your speed.  But, that too wasn't too accurate unless you were heading straight for the VOR.

Do you have a GPS system in your car?  This will tell you your speed.  Most airplanes have a GPS too.  And, so, this device will measure your speed by your change in position to the satelites.  This is the most accurate way to inform the pilot of their ground speed.

Answer 10

put your hand out the window if it gets ripped of thn your going fast...if not then yor going slow

Answer 11

u read the airspeed indicator

Answer 12

Ask the Captain or First Officer.

Answer 13

Too many wise answers.

Here's the simlest version: A hollow tube, called a pitot (pronounced "peetoe") is mounted on the aircraft and points in the direction of flight. As the aircraft moves forward, the wind going into the tube is directed to an instrunent in the cockpit, the airspeed indicator. The faster the plane moves through the air, the higher the wind pressure going into the pitot tube.

Inside this indicator there's a small spiral tube that receives the wind pressure. As the pressure increases, the spiral tube uncoils, moving a needle that is calibrated to show the proper airspeed relating to that pressure.

Sounds a bit complicated, but all it's really doing is measureing the speed of the air moving past the aircraft in flight.

Since the performance of planes in all phases of flight is related to the plane's speed through the air, this is an important measurement.

To find out how fast the plane is moving across the ground, you have to incorporate existing winds, and add a tailwind or subtract a headwind component, to the airspeed.

Answer 14

The indicated airspeed (IAS) is displayed in the flight deck. This is measured by the pitot tubes on the outside of the aircraft. The way it works is as follows;

The pitot tubes measure the speed of the airflow over the aircraft. So if the ground speed (the actual speed) is 100kts, and there is a headwind of 50kts, the IAS will be 150kts. If in the same situation there is a 50kts tailwind instead the ground speed will be the same but the IAS will be 50kts.

Hope this helps.

Answer 15

Depends on if your talking airspeed or ground speed

Answer 16

Pitot head on the front of the plane. next time you go flying you may 3 or 4 of these L-shaped protrusions on the nose. They measure ambient and outside air pressure and a little elf inside the instrument writes the results on a digital screen or turns the dials so the pilots can see.

Answer 17

It measures airspeed with an external sensor.

Look under a cockpit at the front of a plane and you will often see a small bar sticking out - that's what its for.

Answer 18

Some good answers.

A pitot tube usually located under the leading edge wing of light aircraft. And two located at both sides of the front fuselage of commercial jet, in the event that one fails.

Pitot tubes can become blocked and freeze when aircraft fly though cold water vapour such as clouds, so most if not all aircraft are equiped with a pitot tube heater that melt any ice formed within the tube.

On rare occasions such as the blocked pitot tubes incident on a 757 flight in America, a deliberate or accidental blockage of the pitot tubes can become fatal.

Pitot tubes measure the airspeed of the windspeed when stationary and the speed through the air when in flight.

Airspeed doesn't measure the speed over the ground since the higher an aircraft climbs in the atmosphere the less dense the air becomes and the slower the speed indicated on the Air Speed Indicator.

The airspeed is more crucial than ground speed becuase airspeed indicates whether or not their is enough airspeed to substain lift or too much for safe operation.

In order to measure the True airspeed a vector measurement has to be measured, adding the wind speed or taking it away relative to the direction of wind travel.

However at altitudes in exess of 29,000ft using the airspeed indicator cannot be used to determine the safe airspeed within the structural speed limit.

So, when passenger jet's reach this altitide, even with a safe airspeed of 260 knots indicated, well below the red. The mach speed is actually reaching it's maximum operating speed of mach 7.6, with mach 8.4 being it's limit.

So pilots have to select mach speed as opposed to airspeed to determine the safe operating speed below Vne.

Once the aircraft descends below the cruising altitude at a speed of mach 7.6 the airspeed will increase and airspeed as opposed the mach speed will then have to be selected for safer operating speeds.