# Questions tagged [groundspeed]

Ground speed is the horizontal speed of an aircraft relative to the ground. An aircraft heading vertically would have a ground speed of zero. Information displayed to passengers through the entertainment system often gives the aircraft's ground speed rather than its airspeed.

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### Is this flight GPS data intentionally manipulated?

Some flat Earth guy is trying to convince me that flight data is manipulated with and that planes travel faster in the Southern Hemisphere. Now this is obviously not true, in the video speeds of over ...
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### When and for what purpose APU is used on the ground? [duplicate]

When watching the below clip: at exactly 11:02, FO says that APU is not required. What could be the reason for using APU on the ground? What good could this bring? ...
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### Is my airspeed calculation code correct?

Not sure if I should ask here, on Drones SE, or on Code Review SE. Is my Python code for calculating airspeed given ground speed, ground direction, wind speed, and direction from which the wind is ...
• 71
1 vote
400 views

### How fast can a Cessna 172 taco?

What is the highest speed at which a Cessna 172 can taxi without lifting off the ground? If you removed the wings, how fast could it taxi? (Answers only answering the first part are fine; I doubt the ...
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### is DME groundspeed slightly inaccurate due to slant range?

When DME is calculating aircraft ground speed, is it doing it based off of the slant range? Wouldn't this mean that if the aircraft is at sea level and the DME is at sea level that the GS would be ...
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### How is CAS ans GS affected by instant wind changes at different altitudes

Okay, a theoretical example here which I hope will help me understand the physics better. Conditions: Altitude: 50 ft (over sea) GS: 300 knts CAS: 300 ktns Wind: 0 If I now get a 10 knts head wind (...
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### What ground speed reference is used for anti skid control?

I was reading about slip ratio controlled anti skid system and had this one particular question in my mind. In addition to the wheel speed data, slip ratio controlled systems need a ground speed ...
• 191
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### Ground speed question

A light aircraft has a landing speed of 70 knots. A wind of 25 knots is blowing over the airfield. What is the ground speed of the aircraft when it touches down, a) directly in the wind? Why is it ...
4k views

### Why don't small aircraft produce tyre smoke when landing, but big aircraft do?

On almost any recording of big aircraft landing, a huge cloud of smoke can be seen. This even applies to the relatively small Cessna Citation. But I never saw such smoke, at least not visible one, on ...
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### How does it feel like to be outside a flying airplane?

Riding a motorcycle on a freeway at over 200 kph you surely feel the rush of air around you. A typical commercial jet airliner travels at approximately 3-5 times that speed at cruise altitude. ...
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### What determines the maximum ground speed of hot air balloons?

I am wondering how the ground speed of hot air balloons is controlled. The wind is obviously going to have a large influence upon the ground speed, but apart from wind effects, do hot air balloons ...
• 403
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### Why does camouflage make some planes fly slower?

Why does camouflage decrease some airplanes' speed? I have noticed that some planes fly slower with camouflage than without it. For example, when the RAF applied camo on the P-51 Mustang, they noticed ...
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1 vote
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### What is the difference between TAS and GS? [duplicate]

I'm looking for an explanation of true airspeed and ground speed.
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### What was the lowest ground speed landing?

Planes fly if their speed relative to the air is high enough to produce lift. If there is no wind, the plane's air speed will be the same as its ground speed. If flying against wind, its ground speed ...
• 103
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### How far would a landing Airbus A380 go until it stops with no brakes?

If an Airbus A380 lands with all brakes disbled, including reverse thrust, wheel brakes and any other measures it has to stop or slow down. Then how long would it take it to reach a complete stop.
8k views

### What is wrong with a high-speed landing for an ultralight or GA aircraft?

Is it okay to land an ultralight or a general aviation plane at a speed higher than the recommended landing speed for such plane? Will there be any damage if the descent rate is very low?
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### Calculating Ground Speed - E6B vs Pythagorean Theorem

I have been trying to create an excel formula for calculating the ground speed of an airplane using the TAS, Course, Wind Dir, and Wind Velocity. The issue that I am finding is that I can't properly ...
• 101
1 vote
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### What is the unit for ground speed reported by ADS-B?

Strangely enough, I'm having trouble finding the unit reported by ADS-B on the Internet. Many sites simply refer to it as "ground speed". Is it measured in KPH?
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### What special tyres (tires) are needed for high altitude takeoff and landing?

I just watched this video of AA922 taking off from El Alto (LPB) to Santa Cruz. The video's author mentions that the aircraft needs "... special tyres" due to the high altitude. While I do ...
• 1,943
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### What is the name of centre of mass speed of an aircraft?

I have a list of positions (X [NM], Y[NM], Z[NM]) of an aircraft. Every coordinate is given every 1 second. I calculate the speed [knots] between two consecutive coordinates in the following way: \$...
• 1,054
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### Why did the speed of this plane drop so much? [closed]

(Disclaimer: I know nothing about aviation. It is not even a hobby to me. I'm sorry if this question sounds obvious or silly to experts.) I was casually checking the arrival time of a flight on ...
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### How to calculate the real Ground Speed from True Air Speed?

In most of the formulas I've found online GS = TAS + Vw, i.e. true air speed plus wind. However, on the simulator, GS changes drastically if I dive or climb which is obvious because I'm covering 0 ...
• 207
1 vote
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### What is the groundspeed history of an aviation of such as a Boeing plane? [closed]

I would like to see groundspeed data of civil aircraft for distances such as 300 miles. What could it look like for a popular model such as Boeing 737?
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### Does ground speed represent the horizontal speed measured at sea level?

Which of the following vectors is refered to as the Ground Speed? The green one I expect is TAS, the blue one would be Vertical Rate Note that for simplicity I did not draw them as geodetic curves, ...
• 173
1 vote
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### Is there a formula to calculate ground distance traveled given rate of climb and true airspeed?

I'm looking for a formula to calculate the horizontal distance (guess it is the Ground Distance) passed during the phase of ascent (or descent), having the rate of climb in ft/min and the TAS in knots....
• 13
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### Why do we need to know both groundspeed and airspeed? [duplicate]

As far as I understood it correctly: airspeed: is obtained by measuring the difference in airpressure (using Pitot tubes I guess?) around the aircraft and the airpressure caused by propulsion. ground ...
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1 vote
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### Where does the difference between calculated and actual groundspeed come from?

I'm a paragliding pilot. At school we learn that the trim speed of a paraglider is about 38km/h airspeed, the accelerated airspeed is about 45km/h and the minimum airspeed is 22km/h - being inside the ...
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### How do head- and tailwinds affect airspeed?

I'm sure this was asked somewhere, I just can't find it. So if it's a dupe, let me know. Anyway, I'm one of those guys that actually looks at the flight information when I'm flying. I fly ...
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### How much leverage do commerial pilots have on cruise speed?

If you fly frequently there are chances you have seen some delays in departure where you end up waiting in the aircraft sometimes for multiple hours. Almost every time that happened I remember the ...
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### How do pilots manage the speed during the approach?

Once the initial approach fix is reached, what are the different "speed stages" to the runway? I often read about landing speed and approach speed. For example on this chart, Boeing indicates ...
• 113
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### How is TAS affected by wind?

Does True Air Speed (TAS) change with wind speed and direction? My understanding is that if an aircraft were travelling at 470kt TAS, with a hundred knot tailwind, the ground speed would be 570kt. In ...
• 121
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### How did planes measure their speed relative to the ground before GPS?

How did planes measure their ground speed before GPS? If they used some sort of anemometer to measure speed, that would only measure the speed of the plane relative to the air through which it is ...
• 369
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### Why does the speed of commercial airliners fluctuate, sometimes as high as 1,060 km/h or as low as 800 km/h?

I've noticed that (long-haul) airliners sometimes travel at as high as 1000 km/h (I believe I've even seen 1040 km/h), but usually they fly closer to 800 km/h, for most of the trip. This seems odd ...
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### Is it centrifugal force that allows a non-aerodynamic body to achieve lift purely because of thrust? [closed]

If a body has a greater than one thrust to weight ratio, then is the centrifugal force acting perpendicular to the Earth's gravitational pull that allows it to fly ? Or are there other forces that I ...
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### What is the difference between ground speed and airspeed? [duplicate]

What is difference between ground speed and airspeed? Is ground speed used only for takeoff or is it used for flight too?
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### What could cause an irregular climbing pattern on takeoff?

Yesterday (Dec 21, 2015), I was on board Ryanair flight FR4966 from London Stansted (STN) to Lamezia Terme (SUF). The aircraft was a Boeing 737-800, registration EI-EFW. On takeoff, the climbing ...
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### Why did the Flightaware groundspeed readout suddenly spike for this flight?

My 18yr old son is currently in Barcelona - first time abroad and in a plane. Being an overprotective parent I thought I'd track his flight so I could see when he had landed safely = and save the data ...
• 61
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### Why do planes accelerate when they touch down on a aircraft carrier [duplicate]

I was watching a plane documentary, and when the part about aircraft carriers came on, I noticed that as soon as the plane hits the aircraft carrier runways, the plane speeds up. Why is this happening?...
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### How is the actual ground speed of an airliner measured?

Do pilots have the "ground speed" information available? If so, how is the ground speed measured? Or do they rely on GPS info to calculate it?
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