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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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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2answers
838 views
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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1answer
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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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1answer
79 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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6answers
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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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2answers
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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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2answers
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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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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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1answer
76 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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1answer
213 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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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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2answers
346 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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1answer
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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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1answer
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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
241 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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2answers
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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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4answers
191 views
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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2answers
472 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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117 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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1answer
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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
741 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
142 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
230 views
Difference between Mach buffet and shock stall
What is the difference between Mach buffet and shock stall?
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3answers
479 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
129 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
358 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
683 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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0answers
96 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
220 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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4answers
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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
169 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
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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0answers
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What are typical Ki values for calculating indicated air speed?
IAS is defined as
IAS = CAS + Ki
where Ki is a correction factor typical of your aircraft. What is a typical value for Ki? I was not able to find any POHs online with Ki.
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3answers
229 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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0answers
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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
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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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1answer
378 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
432 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
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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
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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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1answer
374 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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1answer
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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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3answers
763 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 ...
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2answers
515 views
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
340 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
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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
123 views
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.)
