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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8
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1answer
249 views

Why this P-51 limitations placard for diving?

I noticed that this placard has different diving speeds related to altitud. My guess is that those values are a safety speed to prevent going into regions close to Mach 1. I know that the speed of ...
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1answer
89 views

What is the required accuracy of an airspeed indicator?

What FAA document specifies the accuracy to which an airspeed indicator must be calibrated to?
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396 views

Could airliners fetch data like AoA and speed from an INS?

If I understood what an inertial navigation system (INS) is, it should be able to calculate speed and orientation of the aircraft. If this is possible, why do airliners solely rely on sensors to ...
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6answers
146 views

Why does TAS increase as altitude increases and why does my C-152 POH seem to contradict this?

I remember learning and memorizing that TAS increases as altitude increases, however I don't understand why. Especially since my C-152's PoH seems to indicate the opposite in the cruise performance ...
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83 views

How is airspeed measured on supersonic aircraft? [duplicate]

Behind the shock wave air is subsonic, would that not cause an issue with the pitot tubes or any other sensor?
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4answers
124 views

What's the relationship between AOA and airspeed?

We know that any aircraft will stall at its stall speed (for a specific weight, CG position, etc.) but also, that the same airplane will always stall at the same angle of attack. I´ve read that IAS is ...
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1answer
87 views

Fighter Jets speed [duplicate]

How does an aircraft measures (or calculates) its speed while in air? Which equipment or sensors are used for measurement of speed? Does it takes Earth as a reference frame for its speed measurement ...
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0answers
65 views

Maximum climb angle [duplicate]

I've got this graph of vertical climb rate vs airspeed, and ive been asked to find the maximum climb angle from the graph, but I'm not really sure what part of the curve shows this. I can do the math ...
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4answers
157 views

What would cause a non-zero indicated airspeed reading on the ground?

What kind of failure would cause an indicated airspeed of say 200 knots on the ground (stationary)?
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3answers
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Why are pitot-static measurements preferred over other velocimetry techniques?

I believe hot wire anemometers (HWA, frequently used in wind tunnels to measure flow velocity) or other sensitive techniques could be used to determine the airspeed. Are there specific reasons for why ...
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2answers
405 views

Why do I get an overspeed warning at 250kts below 10,000ft in Microsoft Flight Simulator?

I'm flying the Cessna CJ4. I get overspeed warnings at 250kts when below 10,000ft, and the speed indicator has red lines at 300kts. Are these warnings triggered because it'll damage the plane to go ...
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2answers
104 views

How does altitude affect the TAS and thrust of an electric fan powered aircraft?

I'm confused about the relation between IAS, TAS, thrust, and shaft power, for an electric application. Yes, higher air is thinner, and thrust goes down due to higher airspeed. What I've researched ...
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3answers
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Is it possible for a plane to accelerate easily from 30 to 45 mph in flight while it struggles to reach 30 mph (the engine runs at constant power)?

In two letters sent to Dr. G. A. Spratt (an aviation enthusiast), Wilbur Wright reported the progress he and his brother had made, up to September 10, 1904, regarding Flyer II, a plane powered by a 16-...
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7answers
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Why angle of attack is always shown against the relative wind parallel to horizon?

I have a question about Stall, which I have difficulty to understand. According to the theory, stall happens when : 1- Speed is slow then a certain limit. 2- Angle of attack is greater than a ...
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1answer
149 views

Is Ducted fan or Propeller better to maximize forward speed of RC aircraft with a given power?

I'm designing an RC aircraft of which the final goal is a crazy top speed. I'll be 3D printing and sanding / finishing the air frame surfaces to reduce drag. In order to achieve maximum top speed, ...
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1answer
79 views

Is propeller wake turbulence quantifiable based on operating conditions?

I know the propeller does work on the air and thus the flow behind a propeller is higher than the airspeed. However, what is the quality of this flow? If I were doing a heat transfer analysis of an ...
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4answers
219 views

Why are true and indicated airspeed different?

So, I understand that True air speed is the motion of aircraft relative to air around it. And, indicated airspeed is speed arising due to dynamic pressure. Considering a true airspeed of 100 knots, ...
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1answer
277 views

How can the cruise speed be larger than Vne?

I recently read the POH for a M20V, the advertising for this aircraft states that the top speed is 242 KIAS. The POH gives the Vne at 196/195 KCAL/KIAS. I have found a similar discrepancy, the Vl3 (...
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1answer
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SR-71 flew 2193 mph. How can this mathematically be Mach 3.3?

Virtually every time I read about the Lockheed SR-71 (including other threads on this forum), I see that its speed record is listed as approximately 2193 mph. The same blurb will invariably say this ...
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1answer
231 views

What is CAS and EAS and how to calculate from IAS? [duplicate]

I am trying to understand IAS, CAS, EAS, and TAS. I was under the impression that CAS is IAS corrected for instrumentation error and position error. The error is specific to the type of aircraft. Why ...
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3answers
184 views

Why do turbofans go faster than turboprops? [duplicate]

Can someone explain why turboprops are less effective in terms of thrust than turbofans? But at the same time, why turboprops burn less fuel? For example, the Bombardier Q400/De Havilland Dash 8 has a ...
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2answers
147 views

What is the Saint-Venant formula for calculating equivalent air speed (EAS)?

I'm studying some ground exams (for a lapsed IR). In the course notes it says that EAS (Equivalent Airspeed, i.e. a compressibility-corrected airspeed) is calculated (e.g. by an aicraft's Air Data ...
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2answers
131 views

What is the relation between velocity and rate of pitch?

I saw the answer to airspeed and rate of turn but this I think isn't what I want. I've seen it many times that aircraft will pitch up much slower when at higher speeds particularly fighter aircraft. ...
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1answer
69 views

Is it possible to determine if winds were high without groundspeed, wind speed, AoA or AoS?

I have a data set that includes TAS, IAS, GPS Lat/Lon, Inertial Lat/Lon, ENU speed, inertial speeds, attitude, and accelerations. I don't need to know the exact wind speed, and I don't think that's ...
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1answer
200 views

What's the relation between TAS and Mach in tropopause?

I understand that TAS decreases with altitude with constant Mach number in troposphere, however I'm not sure what happens in tropospause, as the temperature is constant, however the density is still ...
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2answers
256 views

How close is the air resistance or drag force to being proportional to the airspeed squared?

How is the total air resistance force exerted upon a body (aircraft or car) related to its speed relative to air at far away? A simple Newton's force momentum analysis suggests that the force $F \...
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4answers
307 views

Why do gusts change the airspeed during landing, but turning (which changes where the wind is coming from) does not?

As we know it, aircraft are extremely sensitive to gust during its final landing stage. They can lose airspeed if the wind changes to tail, ad thus loose lift or need to adjust their thrust in order o ...
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4answers
4k views

Why would 2 aircraft fitted with the P&W PT6 Engine have different top speed?

Why can the Quest Kodiac and Cessna Caravan not exceed 200 knots? PT6 from Pratt and Whitney in other implementations like Epic E1000 and Pilatus PC12 can cruise at over 300 knots. The Kodiac and ...
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6answers
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What is the commercial passenger aircraft top speed record?

Aircraft manufacturers claim that commercial passenger aircrafts cruise at the speed of 400-500 knots. But, is the top speed of a commercial passenger aircraft recorded (while in air)? If so, what is ...
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1answer
180 views

What is the power curve [closed]

Someone help me understand this thing in a simple way. I understand it helps determine Vx.
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0answers
97 views

What plane has the widest range in speed in which it can operate? [duplicate]

What propellor plane, other than planes with vertical takeoff capability, has the largest gap in speed between its slowest stall speed and its maximum airspeed? I am looking for a plane with a short ...
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1answer
76 views

Constant turn radius with Δ airspeed and bank

Can someone explain how speed impacts rate of turn and and degree of bank required? I'm trying to understand this practice problem but can't get the concept: Say you have 2 vehicles travelling at ...
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4answers
381 views

Does “trimmed for current speed” mean that the plane will do whatever to maintain the current airspeed?

If I understand right, when you are trimmed for current speed, let’s say 290 KTAS, does that mean if airspeed increases to 295, the plane will pitch up to slow it back down? And vice versa for the ...
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1answer
60 views

Linking equivalent airspeed with waypoints, altitude, time and speed

Say I want to find out EAS and I'm given a time that a pilot will reach a waypoint that is "X" Nautical Miles away, an altitude & I'm also given a ground speed that is increased by a tailwind. Is ...
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1answer
218 views

What are the equation linking static air temperature with true airspeed & altitude?

If I want to calculate static air temperature (OAT), but I'm only given an altitude and a true airspeed. Is there such an equation that relates these principles together. I've had a look at wikipedia ...
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1answer
4k views

Why is a 737 Original speed-restricted below 10 kft with inoperative windscreen heating?

According to this page on the 737's operational limitations, the Original 737s (737-100/-200) are limited to 250 KIAS below 10 kilofeet if the windscreen-heating system is inoperative: Anti-Ice & ...
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4answers
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Is any device installed on airplane to measure wind speed relative to the ground, and its direction?

A device or tool which can measure actual wind speed to the ground rather than to the airplane. Also a device which detect the wind direction to the plane. The device I meant is something like this ...
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2answers
2k views

Is it right to extend flaps only in the white arc?

If the cruise speed is >80kts on the downwind leg but I can only extend flaps in the white arc, am I right in saying I need to get to the white arc, even if I'm on - for example - 100kts? For ...
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1answer
517 views

Why use Mach number for describing the speed of aircraft?

What does Mach speed mean for describing aircraft speed if the speed of sound changes with temperature?
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1answer
341 views

Why does the F16 HUD give you one number for your speed and the analogue gauge another?

Why does the F16 HUD give you one number for your speed and the analogue gauge another different number?
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4answers
3k views

How does speed affect lift?

I understand the lift coefficient shown above. But does lift increase with speed, and how? I understand I can't apply this to the graph as it is a coefficient, but if I had an angle of attack of 10 ...
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2answers
243 views

What is a jet engine's fuel flow at constant IAS?

Here is my assumption: In straight and level flight of a jet turbine engine: One IAS = One drag = One thrust = One fuel flow Therefore, the fuel flow will be approximately the same for a given IAS, ...
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1answer
104 views

Airspeed Calibration alternate static source, what is this for?

I found a 'Airspeed Calibration Alternate Static Source' Figure in C172R POH. There are three kinds of Figure, 1. Heater off, Vents and Windows Closed 2. Heater On, Vents Open and Windows Closed 3. ...
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1answer
523 views

What is the highest indicated airspeed ever achieved in a traditional aircraft?

It is fairly well known that the SR-71 holds the record for highest speed for a traditional aircraft (not a rocket/able to land and takeoff under its own power). However since the SR-71 flies much ...
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3answers
3k views

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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2answers
202 views

Are there locations/altitudes with minimum speed requirements?

For example, a slower aircraft operating on the North Atlantic Track System would have an operational impact on surrounding/overtaking aircraft as well as potentially increasing ATC workload to ensure ...
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2answers
86 views

How can I calculate the speed gain from using multiple STC modifications together?

Looking at a parts manufacturer website, they list various STC'd modifications for Mooneys with estimated (cruise?) speed gains for each. However, I've heard that those gains are not additive. For ...
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2answers
498 views

What is the fastest unpressurized aircraft?

What is the fastest unpressurized aircraft with oxygen masks that can carry people?
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1answer
181 views

How do I calculate TAS from IAS in this question?

How can I calculate the answer to this EASA PPL ECQB question? An aircraft cruises at altitude 5000 ft on a heading of 180° with an indicated airspeed of 100 kt. The wind vector is 180° with 30 ...
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2answers
4k views

What is the regular stall speed of an F-16 flying in a straight-and-level path?

I want to know what is the minimum speed that an F-16 can fly at without stalling. I have searched the web, but found no exact information answering my question. Most of them say that it depends on ...

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