Questions tagged [airspeed]

The speed of an aircraft relative to the air. Among the common conventions for qualifying airspeed are: indicated airspeed ("IAS"), calibrated airspeed ("CAS"), true airspeed ("TAS"), equivalent airspeed ("EAS") and density airspeed.

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3answers
33k views

What is the true top speed of the SR-71?

By "true" top speed I mean the absolute fastest horizontal airspeed the aircraft can achieve if damage to the engines is disregarded (similar to how the MiG-25 apparently can reach mach 3.2 but may ...
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2answers
847 views

Do smaller wings mean faster flight? [closed]

I've known that military aircraft with small wings can fly very fast, while commercial aircraft with big wings cannot fly as fast. Why is this?
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1answer
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What is the relation between IAS and TAS at a constant altitude?

I have noticed that when calculating True Air Speed for any given altitude, the faster the Indicated Air Speed, there seems to be a larger increase in TAS? My thinking was that at a constant altitude ...
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3answers
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What determines the maximum speeds for a particular aircraft?

Aircraft have three different maximum airspeeds: VMO (maximum operating speed) - the maximum speed that the aircraft is allowed to reach during normal operations. VNE (never exceed speed) - the speed ...
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3answers
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Why do aircraft need Mach number? [duplicate]

Why don't aircraft operates with IAS only? Is there any other usage of Mach number except monitoring of shock waves formation? How Mach number is calculated?
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2answers
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Does airspeed affect the critical angle of attack on an airfoil?

I understand that the critical angle of attack is mostly affected by the shape of the airfoil. However does the airspeed of the airfoil or the density of the air affect the critical angle of attack? ...
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2answers
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What is the meaning of “static pressure”?

I don't really know what static pressure is. Does the ASI (Airspeed Indicator) use cockpit pressure as static pressure, to find the dynamic or differential pressure? I just found this statement : ...
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3answers
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What is the maximum angle F-16 can turn in x seconds flying at corner speed?

How can one calculate the maximum turning angle F-16 can turn in x second flying at corner speed. Is it changed with height or weight?
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2answers
431 views

How does the mechanical linkage of the airspeed indicator convert dynamic pressure to KIAS?

I understand the underlying principle of an airspeed indicator, ie. that it uses the Pitot-static system to measure the dynamic pressure as the difference between total pressure and static pressure. ...
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1answer
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What's going on with sudden acceleration/deceleration in mid-air?

I was recently on a flight between LGB and PHX. I've been flying since I was 5, am now 31. After takeoff, as the plane approached cruising altitude, the plane slowed down. A lot. Then accelerated ...
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How (and why) does engine thrust change with airspeed?

I'm interested in how the thrust of a turbofan engine is affected at higher airspeeds (TAS). I know (I believed) that engine thrust(at constant N1) was relatively constant like in the following graph (...
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3answers
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What scale is the speed trend line on a PFD's ASI?

A primary flight display (PFD) in a glass cockpit has an airspeed indicator (ASI) that doesn't just display the speed, but also a vertical arrow or bar that shows the "speed trend" i.e. the ...
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Is there a speed needed to achieve flight?

Is there a minimum speed needed for flight (universally)? For example, if something was going 10 miles per hour, could it achieve flight? And by flight I don’t mean throwing a paper airplane, I’m ...
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2answers
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How would a low-airspeed fixed-wing drone be designed to reduce effects from gusts and wind shear?

In a story I am working on, the characters need a fixed-wing drone that can rendezvous with a blimp, where by "rendezvous" I mean "come within a very short distance at low relative airspeed". The ...
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2answers
745 views

If maximum speed was a priority for modern military fighter jets and bombers, approximately how fast would they likely be?

Burt Rutan talks rather passionately about the lack of innovation in space flight, but also mentions how fighter jet (maximum) speed performance has stalled: In fact,...
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6answers
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Would a slower speed and lower altitude reduce fatal incidents?

If it became plausible to fly commercial aircraft much lower in the future (due to developments in technology and airway regulations permitting it), say at a standard height of 5,000ft, but with a ...
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2answers
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How can the zero-lift drag coefficient (parasitic drag) be calculated?

Consider a 3-D wing made from an arbitrary airfoil, say a NACA0012 airfoil. The wing has a trapezoidal shape, with a fixed span, root chord, and tip chord. Also, assume that the wing loading is known ...
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2answers
2k views

Why does an airspeed indicator not simply read TAS?

If the airspeed indicator has inputs regarding air density (static port) and temperature. Why isn't Indicated airspeed from the indicator simply the same as True airspeed
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1answer
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What is the rate of acceleration based on downward pitch?

In other words, I want to understand how gravity converts into thrust in respect to pitch. What is the general mathematical relationship? (For visuals, imagine a bird diving to gain speed.)
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1answer
153 views

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: $...
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2answers
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What is the relation between maximum airspeed and engine power?

I know that the drag force on an airplane scales as (velocity)^2 which implies that doubling the airspeed will produce a 4x increase in the drag force. So my question is: Imagine we have an airplane ...
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2answers
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Does the F-16 have a speed limiter?

In an aircraft like F-16, how do the pilot prevent going faster than Vne (velocity, not exceed)? From the block 50 manual it seems to indicate Vne is 800KIAS/2.05M. I believe even the earliest F-16s ...
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Why does X-Plane 11 show the SR-71 at 200 knots but Mach 3 at 80,000 ft?

So I noticed on X-Plane 11, the SR-71 reaches Mach 3 at 80000 feet, but the equivalent airspeed is only around 200 knots. What explains this difference between the mach number readout and the EAS ...
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1answer
317 views

Is it possible for an airliner to cruise at engine full thrust?

What would happen if the pilot of a modern airliner like the boeing 747-800 or Airbus A380 left the throttle at full thrust at cruise altitude for an extended period of time e.g 4 hours if the ...
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2answers
676 views

What type of airspeed are wind speeds given in?

When you get wind speed from an ASOS/AWOS or from ATC, are those speeds in true airspeed? Are the instruments weighted for elevation? Say you're on approach to 05R at MEX and you're given wind speed ...
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1answer
401 views

How does an ADIRU convert ram air pressure from the Pitot tube into Airspeed?

I know how the analog Airspeed Indicator shows the Airspeed from the ram air pressure from the pitot tube. But I'd like to know how an ADIRU converts the raw pressure data to Airspeed that is ...
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7answers
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Is it possible to accurately measure airspeed without pitot tube?

This is a follow-up to my previous question: How does this IMU work and how to convert its output into meaningful information? for which many people asserted that I need a pitot tube and a static ...
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6answers
707 views

How can a passenger determine airspeed without a handheld GPS?

This question is in the context of being a passenger on a commercial airliner, where you're in the cabin and the cockpit door is locked. In another question, someone posited that if an airliner had ...
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8answers
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Does a sudden drop of the velocity of the headwind affect the airspeed by lowering it?

I had a discussion about air speeds with one of my instructors recently. He is claiming that there is a sudden drop in the wind velocity as you get closer to the ground (which is absolutely true, due ...
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1answer
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What's the relationship between drag divergence Mach number and maximum operating limit Mach number?

The drag divergence Mach number, also known as the force divergence Mach number, is the Mach number where drag waves start to form. The drag divergence Mach number is typically between 5 to 10 ...
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1answer
582 views

How to calculate the best climb rate and glide rate?

Considering the lift equation $$L = C_L \frac{1}{2}\rho v^2 s$$ Given $P$ is 1,000 ft, $\rho$ is 0.002308, and $V$ is the cruise speed of a Piper Archer or 126 knots, we get $$L = (0.4) (0.002308) (...
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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 ...
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4answers
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Why does indicated airspeed change with altitude?

I know that if you fly at a low altitude and at a high altitude at the same TAS, your IAS will be lower at the high altitude than at the low altitude. Why is this though? Wouldn't the static vent ...
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1answer
5k views

How are IAS to CAS conversions calculated?

How do I calculate calibrated airspeed (CAS) from indicated airspeed (IAS)? For example, how is 600 knots indicated calculated to 595 knots calibrated?
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3answers
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What prevents a Machmeter from being the standard airspeed indicator?

Airspeed is more accurate when displayed by a Machmeter than when displayed by an airspeed indicator. It isn't affected by ambient temperature / density changes. It is still affected by position error,...
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6answers
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Why does Airbus not display the exact airspeed on the PFD?

On every other PFD (I know), the exact airspeed is displayed as big number on the PFD. To clarify what I mean, here are two pictures: Source, added square, Boeing PFD Source, added square, D10A EFIS ...
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1answer
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What would be the stall speed of Solar Impulse?

In most of the tables, only the take off (22 mph) and cruise (43) speed of the Solar Impulse are listed. It is an experimental plane, slow, with very huge wing for solar batteries. The take off speed ...
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14answers
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What is the slowest fixed-wing airplane?

It's easy to find information about the fastest airplanes, in different categories (e.g. X-15, SR-71, the Concorde etc), but what is the slowest one? Which powered, manned airplane is capable of ...
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1answer
484 views

What's the speed callout by the PNF on airliners for?

On all Airliners, there is a speed callout by the PNF at some point during take-off, usually at 80 or 100 KIAS. Whats the reason for those callouts? And why are some at 80 KIAS and some at 100 KIAS?
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What is the difference between a pitot tube and a pitot-static tube?

What is the difference between a Pitot tube and a Pitot-static tube? If an aircraft fitted with Pitot tube and static holes on the fuselage, is it necessary to consider the static pressure ...
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2answers
520 views

What was the first operational U.S. military jet fighter to fly at mach 2?

Was it the McDonnell Voodoo or the Lockheed F-104A?
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3answers
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How does change in airspeed affect pitching moment?

In aircraft with conventional elevator control, if I increase the speed, the horizontal tail sees higher velocity and hence higher lift. Does it mean that increasing airspeed creates nose down ...
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2answers
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What are typical airspeeds and lift coefficients for UAVs at different flight stages?

I've been trying (unsuccessfully) to figure out the relationship between airspeed of a fixed wing UAV at different flight stages. What I mean is, I would like to know the order of airspeeds from ...
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1answer
599 views

Is there a difference in aerodynamic efficiency between single engine and twin engine airplanes?

I've learned a lot of great information about aviation on this website. One insight I learned from a poster here is that, all else equal, for every doubling of engine power that you give an airplane, ...
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3answers
17k views

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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3answers
511 views

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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0answers
582 views

Why Planes Don't Fly Faster? [duplicate]

I recently Stumbled on this Why Planes Don't Fly Faster on youtube and it talked about how less speed is more economical for airlines and he also said something that plane above and below speed of ...
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5answers
1k views

Would mechanical indicators have helped in the Air France 447 incident?

NB I am not an aviation professional. I saw a documentary about the terrible Air France 447 disaster the other day. I was struck, as were the experts in it, including David Learmount, who's known as ...
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1answer
81 views

Where can I find speed and thrust data for airplanes during the approach?

While trying to gather information on fuel consumption during the approach I have found this equation : $$f=C_{f1}\cdot (1+V_{TAS}/C_{f2})\cdot T$$ (on this FAA paper) $f$ is the fuel flow $T$ is ...
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2answers
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What is the reason for changing the speed reference (IAS or Mach number) with altitude?

Inspired by that question: How is the airspeed-Mach number transition handled in modern airliners? When pressure and density decrease IAS also decreases. When temperature and pressure/density ...