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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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What will be the performance penalties of increasing the wing area of a delta winged aircraft to obtain a lower approach speed?

Delta winged aircraft such as the Dassault Mirage III have an approach speed of 170 knots as specified by the manufacturer. The Mirage F1 was designed to have a lower take off and landing speed than ...
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How to find TAS for given CAS, FL and OAT?

Here is another question for my PPL Exam. If anyone can illuminate me with explaining every step to achieve TAS with given parameters, it would be great. Given: Calibrated airspeed (CAS): 155 kt. ...
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69 views

How to calculate Equivalent Airspeed immediate from Calibrated Airspeed?

I want to calculate each step like IAS -> CAS -> EAS -> TAS as a chain. Each chain step should depend on the previous chain step. IAS is clear. This is function of pressures. With Bernoulli equation, ...
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430 views

Does diving after a take-off help gaining altitude?

I have often read fictions about aircraft, where a pilot does an action that I cannot explain: During a takeoff with an heavy aircraft (four motors for example), the pilot rolls to the end of the ...
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111 views

Airliner speed when descending through 10,000 feet

How do airliners get to 250 kts when descending through 10,000 feet as required by the FAA? Do you level off at 10,500 feet until speed is less than 250 and then descend further? Must pilots ask ATC ...
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Why does an increase of airspeed result in a decrease of angle of attack?

In Chapter 02: Aerodynamics of Flight of Helicopter Flying Handbook, on page 10, it says: Induced flow velocity is increased, resulting in a decrease in AOA. I don't understand how airspeed can ...
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1answer
55 views

How do changes in flight affect L/D max and the speed at which I must travel to maintain it?

I have an plane flying at L/D max and I want to maintain L/D max. Firstly, if this plane burns through a portion of fuel and becomes lighter, how would I have to change the speed to maintain it? My ...
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What’s the speed for lowest sink rate on a DA20?

In the DA20, the POH lists for glide speed (flaps up) only one speed giving the best glide angle / furthest distance (73 KIAS). But what about, if I don’t need that much distance to glide (e.g. ...
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258 views

Why is airspeed different in climbs and descents although the AoA doesn't change?

Here are the background facts: This excercise has the objective to familiarise the student with the slow flight characteristics. The steps are: 1)Establish straight and level, 90% RPM, 15 units ...
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What is the effect of altitude on true airspeed?

I know that wind is taken into account when we compute the TAS(true airspeed) and GS(ground speed). However what is the relationship between the TAS and altitude? For example: What is the true ...
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152 views

How is altitude correlated with true airspeed?

I am trying to understand the BADA 3.0 dataset (specifically I am looking at Performance Summary Tables): E.g. What is not obvious to me is why those tables mention only single TAS for specific FL. ...
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86 views

Is there an increased concern for stall safety in a 1G steep turn?

Most people know the standard, "At a 60 degree bank, an aircraft experiences 2G's" checkpoint for load-factor on an airplane. I assume that this statement has an underlying, unspoken assumption that ...
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Why is indicated airspeed rather than ground speed used during the takeoff roll?

My instructor asked me this question during my lesson and I couldn't come up with any answers. He asked why do I need to look at the indicated airspeed rather than ground speed when in takeoff roll or ...
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Pitot tube pressure question

I have this question is the pressure measured in the entry of the pitot tube the same when the plane is flying headwind or turning a 360 degree turn while maintaining the same indicated airspeed?
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Why is trim for take off affected to Vmc(Speed maintain control)?

I am studying in Vmc part, but I have hard time to understand that trim for take off is affected to Vmc. How and why does it make Vmc speed increase?
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3k views

What is a jet (unit) shown in Windows 10 calculator? [closed]

From Windows 10's calculator: What is a "jet" (physical unit)? And why does it equal 480 knots or 888,88 km/h, if a jetliner's cruising speed is around 950 km/s? Or why does it equal 0.73 M, if a ...
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85 views

Temperature sensor are needed to compute True Airspeed for low speed aircrafts?

I know standard air data computer can produce true air speed with total air pressure, static air pressure, and total air temperature. But for a low speed aircraft <100 knots, do I need to install a ...
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225 views

Why were the space shuttle’s flight controls only certified for low airspeeds?

Somewhat ironically for a vehicle designed to reach orbital speed, the space shuttle’s flight control system was only certified for airspeeds up to 333 KIAS, and exceeding 470 KIAS (the maximum ...
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121 views

How should I answer this question about measuring airspeed using dynamic pressure?

I have come across a question in the PPL Principle of Flight material which I can't understand how to answer: Give your opinion on the statement "Measuring dynamic pressure is the way to ...
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364 views

What are the consequences of touching down at too low of a speed?

The consequences of a high speed touchdown / high vertical speed are very much obvious. However, what will the consequences be of a low speed touchdown? How severe are they (if any)?
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248 views

Why are the positions of an aircraft's angle-of-attack vanes dependent on airspeed?

According to this answer to an earlier question of mine, the positions of the angle-of-attack sensor vanes on the A330/A340 are dependent not only on AoA, but also on airspeed (and, according to @ymb1'...
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What is a simple way to explain why best range airspeed is below normal cruise airspeed? [closed]

Without using complex mathematics, please explain why best range airspeed is less than normal cruise airspeed.
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4answers
305 views

What is the official unit of airplane/aviation speed?

Some units I read/found are commonly used in aviation: mach, knot (nautical mile per hour), mile per hour (mph), kilometer per hour (km/h or kph). "Official" meaning like the units used by the flight ...
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Why do aircraft have a crossover airspeed, and why does it increase at higher vertical load factors?

According to the NTSB accident report on the crash of USAir Flight 427, all commercial aircraft have a crossover speed (the speed at which the maximum rolling force from the aircraft’s ailerons and ...
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Do airline pilots use speed stability to cope with unreliable airspeed indications? If not, why not?

There have been a couple of airline accidents in which unreliable airspeed indications (or the fear thereof) have played a role: Birgenair Flight 301 in 1996, where one of the pitot tubes was blocked,...
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656 views

Why do pilots normally fly by CAS rather than TAS?

I think I know the answer to this question, but I want to confirm. Airline pilots normally fly a CAS/Mach profile, which means that above the CAS/Mach transition altitude they fly by Mach, and below ...
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195 views

What is an accurate expression to calculate IAS as a function of TAS? [duplicate]

Does anyone know a good source for an expression of IAS as a funtion of TAS? I was hoping to find an accurate IAS equation that is only dependent upon TAS, static pressure and static temperature.
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216 views

Why are airspeed gauges labeled above Vne?

Examples: Cessna 150L Vne = 141 knots (162 MPH), gauge labeled to 170 knots. It looks like there's room to extend the scale to 180. Cessna 152 Vne = 149 KIAS, gauge labeled to 170. Cessna 172R Vne = ...
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7answers
1k views

How does maximum speed vary with altitude?

Question: How does a commercial jetliner's highest possible groundspeed vary with altitude (assuming wind=0) ? My understanding is that drag decreases with altitude, therefore maxspeed increases with ...
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2answers
159 views

Why is the normal operating airspeed so much lower than the cruise speed in this table?

I need to work with the following table. I'm interested in vMO which I assume I can simply obtain from converting MMO to vMO through $M = v/ \sqrt{1.4 * 287 * T}$. (Is that correct?) However, I ...
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1answer
311 views

Difference between Mach buffet and shock stall

What is the difference between Mach buffet and shock stall?
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561 views

How can I compute the minimum possible bank angle for a turn with a given radius?

I know that I can find an upper bound for the bank angle for a plane, if I know the maximum sustained load factor of that plane because the roll angle and the load factor $n_z$ in a turn are directly ...
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1answer
138 views

How do the vortices of a fixed wing and horizontal stabilizer interact? [duplicate]

What interaction of vortices between the fixed wing and horizontal stabilizer? How do the vortices affect the flow of the horizontal stabilizer upon leaving the wing? when will the downwash effort ...
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1answer
372 views

Is there an aircraft that can go supersonic at sea level without using afterburner?

Is there an aircraft that can go supersonic at sea level without using afterburner? Quick look through the "supercruise" capable aircraft might be helpful in narrowing down the possibilities, though I ...
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1answer
868 views

Best glide speed vs. best glide angle? Maximum glide range?

I have some open questions regarding best glide in a descent: I understood, that there is a best glide speed. This best glide airspeed occurs at the highest lift-to-drag ratio (L/D). This best glide ...
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114 views

How does pitot tube shape affect indicated airspeed? [closed]

Air flow over wings and engine inlets greatly changes due to a number of factors, such as atmospheric conditions, speed, and the design of the surfaces. On some engines you can see mist behind the ...
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1answer
244 views

What is the bank angle that should be sustained to move in a uniform circular motion? [duplicate]

I want to deduce the rate of turn of targets that move in a uniform circular motion. The radius of the different circles are known in advance. I have searched for my question and found the following ...
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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
189 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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2k views

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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299 views

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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159 views

How can I calculate different airspeeds given atmospheric data?

I want to calculate various airspeeds (TAS,CAS,IAS,..) given a certain altitude. With the given altitude I can figure out the pressure, density, speed of sound, temperature, and viscosity. However, I'...
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3answers
2k views

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
529 views

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
470 views

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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2answers
2k views

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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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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440 views

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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2k views

How (and why) does engine thrust changes 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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855 views

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 ...