Indicated Speed vs. Real Speed

[WarTooth]

Guys,

I'd like your feedback on the topic of Indicated Speed vs. Real Speed.

1. Which is which? Which is the red indicator and which is indicated by the speedometer?

2. Why is there simply not one indicator for speed?

3. What does it mean to you, i.e. what are common tactics that can be employed given the values of these speeds?


Thanks for clarifying this,

WT

[Shane]

sigh...

short version... fly by white, argue about red.

 

[dkff49]

Here is a link to description of all the gauges. In there it explains the difference.

http://trainers.hitechcreations.com/gauges/gauges.htm

As far as the benefit of knowing the Indicted speed, I don't know for sure. I would venture to guess it is there for some level of realism.

The True Air Speed (TAS) is there because the speedometer actually measures air-pressure to acquire the speed. This changes with relation to altitude and the IAS gauge does not account for this, which throws off the actual speed. The TAS needle takes this change in air pressure into account, so this is important because it will tell you what speed you are actually doing.

Now I am not a pilot in real life but airplanes do not have a TAS indicator, this has to be judged in other ways that are either extremely difficult or impossible in game, due to limitations that exhist in a 2D world.

[TequilaChaser]

a short answer is to use IAS ( indicated air speed ) for all your aircraft maneuvering.......and acknowledge the higher in altitude the more you need to maneuver in a easy, smooth flowing gentle manner, to not use up excessive Energy.....

TAS ( True Air Speed ) is your planes speed in relation to the Ground ( to earth ). TAS is what most people use when they are reporting test data, some still use IAS though or make it a point to point it out in the test data.

[ImADot]

TAS ( True Air Speed ) is your planes speed in relation to the Ground ( to earth ).

That's why it is very important to calibrate your bombsight to the true airspeed indicated in your E6B...that will ensure your bombsight is indicating a correct impact point as you fly across the target.  If you were to calibrate to indicated airspeed, from say 20,000' you will be miles off in your bomb drop since the airspeed indicators could be 20, 50 or more miles per hour different.

[bustr]

So for the Newbie......

At Dok Gonzo's fighter compairison site:  http://www.gonzoville.com/ahcharts/index.php

Are the speeds in TAS or IAS.......

[BaldEagl]

So for the Newbie......

At Dok Gonzo's fighter compairison site:  http://www.gonzoville.com/ahcharts/index.php

Are the speeds in TAS or IAS.......

TAS

IAS basically measures the airflow over the wings.  You need to maintain a minimum level of airflow, which varies by altitude due to air density, to remain in flight.

When people talk about stall speed, landing, best corner speed, etc. they are talking in terms of IAS.  When they talk about things like top speed, dive speed, etc. they are generally talking in terms of TAS.

[Golfer]

airplanes do not have a TAS indicator, this has to be judged in other ways

That is not true.  It's very common on modern airplanes to have TAS displayed in addition to a groundspeed readout.  The F-4 Phantom also had an analog TAS indicator:

[dkff49]

That is not true.  It's very common on modern airplanes to have TAS displayed in addition to a groundspeed readout.  The F-4 Phantom also had an analog TAS indicator:
(Image removed from quote.)

That is interesting there. I thought I read somewhere that this is not something that is normally in an airplane. My appologies.

As a "how it works" kind of person I am, I have a question.

Can you guess?

How does an analog TAS indicator acquire it's measurement? The IAS I understand uses air pressure much like the way my boat does, but what reference would an analog gauge use?

[Golfer]

The gauge pictured above is from an F-4 Phantom and not having flown one I have no idea how.  I would expect it would involve taking into account altitude and current indicated airspeedbut couldn't tell you with certainty.  I can ask the person who took the picture who was flying when he snapped it.

A more common display is electronically generated using onboard air data systems and/or GPS to present the information.

You can see in the upper right hand corner of this MFD (Multi-Function Display) from the Embrear 175:
-Wind components with directions and arrows.  This is showing a 34kt xwind component from the left with a 47kt headwind component.
-Static Air Temperature (Temperature outside)
-Total Air Temperature (Accounts for the heat generated by the airplane traveling through the air)
-True Air Speed shown in knots.



In this setup the groundspeed would be displayed on the PFD (Primary Flight Display) in front of each pilot as seen here:

Groundspeed is in the middle left of the display below the airspeed tape.




At any rate True Air Speed is a very common item to be displayed in many of todays airplanes.

[Mace2004]

Speeds in aviation can get confusing.  There's Indicated Airspeed, Calibrated Airspeed, True Airspeed, and Ground Speed (and Mach Number but we won't go there).

Indicated Airspeed is a measure of the Impact Pressure (also called Dynamic Pressure) of the air as you move through it.  Impact Pressure is the force exerted by the air as it "impacts" the airplane.  Stick you hand out the window of your car.  The force you feel is impact pressure.

IAS is only displayed on the airspeed indicator as MPH or Knots due to convention as it really isn't a direct measure of distance traveled over time except in one condition and that's at sea level on a standard day with no wind.  You could actually change the numbers on the IAS dial to A, B, C, D, etc. and learn to use it just fine, it's only by long standing convention that it's numbered as it is. 

What's important about IAS is that part about it being a measure of impact pressure.  Impact pressure is the physical force against your airframe due to speed and it's what lets you generate lift.  The higher you are in altitude, the thinner the air is and the faster you have to fly to get the same amount of pressure against your wings to generate the same amount of lift; however, since IAS directly measures this pressure, it's the most useful indicator of how your airplane will fly.  Say you're flying at 200mph IAS on the deck and your airplane can pull 4G before stalling.  If you're flying at 20,000 feet at 200mph IAS you can still pull 4G before stalling but your actual speed is much higher.

Calibrated Airspeed is just your IAS after you apply corrections for your aircraft's system inaccuracy which is not an issue in AH.

Unlike IAS, TAS is a true measure of distance over time (i.e., speed); however, it is a measurement of the distance traveled through the airmass, not the ground.  You arrive at TAS by taking IAS and adjusting it for altitude which is done in an aircraft manually or automatically by an Air Data Computer.  In AH, this is done for you by the program.  Now that you've extablished your actual speed through the airmass, you can add or subtract the speed of the airmass (wind) to arrive at your ground speed.  If you're flying 400mph TAS and you have a 100mph headwind then your actual ground speed will be 300mph.  In modern aircraft your ground speed is measured directly by an Inertial Navigation System or GPS.  These systems can tell you the actual wind direction and speed by the difference between your ground speed/course and TAS/heading.

In AH main arenas there is no wind so your TAS will equal your Ground Speed as long as you're flying level (if you're diving straight down at 400mph TAS your ground speed would equal zero)  Use your TAS as a reference point for level bombing and to determine how long it will take you to get from point A to point B.  Use your IAS for everything else.

[TequilaChaser]

Speeds in aviation can get confusing.  There's Indicated Airspeed, Calibrated Airspeed, True Airspeed, and Ground Speed (and Mach Number but we won't go there).

In AH main arenas there is no wind so your TAS will equal your Ground Speed as long as you're flying level.  Use your TAS as a reference point for bombing and to determine how long it will take you to get from point A to point B.  Use your IAS for everything else.

hence the only reason I had just mentioned IAS and TAS in the description I gave.....I was refering to the game only, my bad for not pointing that out.

very nice indepth post, Mace  <S>

[uptown]

sigh...

short version... fly by white, argue about red.

 

  that's what I do.

[Golfer]

Mace did the F-14 have an analog TAS indication like the F-4?

If so, how did it work?

[Mace2004]

Mace did the F-14 have an analog TAS indication like the F-4?

If so, how did it work?

No, the primary flight instruments included a single airspeed indicator that gave you IAS and Mach; however, the AWG9 could display TAS as well as actual GS.  TAS came from the CADC and GS from the INS.  The F14 really didn't need a TAS indicator since the navigation system would figure out your time to go to designated points. 

On the other hand, a rough rule of thumb for a quick estimate is to use the coincidental fact that your Mach number roughly equals the number of miles per minute you're traveling. For instance, if you're flying at .6 Mach (a typical cruise speed) then you're going about 6 miles per minute.  You'd use that rough number to quickly figure out TTG.  For instance, say you're on CAP 200NM from the CV.  To figure out how long it'll take to get back overhead for your recovery time then divide 200nm by 6 and it'll take about 33 minutes.  If you're running late bump your speed up to .9M and get home in 22 minutes.  If you've got enough gas then hit 1.1M and you'll be there in 18 minutes.