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.
0
votes
2answers
116 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 ...
3
votes
2answers
316 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)?
4
votes
1answer
88 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'...
3
votes
1answer
78 views
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.
0
votes
4answers
224 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 ...
9
votes
2answers
164 views
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 ...
4
votes
4answers
174 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,...
3
votes
2answers
241 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 ...
0
votes
2answers
61 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.
6
votes
1answer
198 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 = ...
2
votes
7answers
443 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 ...
0
votes
2answers
105 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 ...
1
vote
1answer
144 views
Difference between Mach buffet and shock stall
What is the difference between Mach buffet and shock stall?
3
votes
3answers
380 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 ...
1
vote
1answer
106 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 ...
0
votes
1answer
239 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 ...
3
votes
1answer
459 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 ...
3
votes
0answers
80 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 ...
0
votes
1answer
206 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 ...
6
votes
4answers
9k 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 ...
0
votes
2answers
164 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?
2
votes
1answer
1k 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 ...
0
votes
0answers
30 views
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.
1
vote
3answers
196 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 ...
0
votes
0answers
128 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'...
7
votes
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?
5
votes
1answer
272 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? ...
0
votes
2answers
379 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 :
...
2
votes
2answers
908 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?
3
votes
2answers
162 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.
...
1
vote
1answer
310 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 ...
8
votes
1answer
1k views
How an Engine thrust changes with airspeed? Why?
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 (...
5
votes
3answers
652 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 ...
0
votes
2answers
430 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 ...
6
votes
2answers
242 views
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 ...
4
votes
2answers
318 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,...
18
votes
6answers
7k views
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 ...
2
votes
2answers
1k views
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 ...
5
votes
2answers
1k 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
3
votes
1answer
111 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.)
2
votes
1answer
146 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:
$...
4
votes
2answers
681 views
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 ...
2
votes
1answer
805 views
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 ...
6
votes
2answers
878 views
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 ...
4
votes
1answer
199 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 ...
9
votes
2answers
324 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 ...
3
votes
0answers
130 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 ...
13
votes
6answers
4k views
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 ...
7
votes
6answers
518 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 ...
22
votes
7answers
3k views
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 ...
