Airspeed Indicator

[badhorse]

I wish the redline mark on the airspeed incidator was a real redline mark(shows the never exceed speed of the airplane) and not the true airspeed.  Not only would this be more accurate, it would be more useful.

[4deck]

UMMM. I dont want to loose my real airspeed indicator.

[badhorse]

Originally posted by 4deck
I dont want to loose my real airspeed indicator.

Not sure what you mean.  I'm not saying the airspeed indicator should go away.  Just that the redline mark should reflect the never exceed speed of the airplane you are flying instead of true airspeed.

[BaldEagl]

Indicated airspeed is good for judging manouverability potential, landing speed, stall speed, compression speed, etc (basically lift... white needle) but you still need to know how fast you are in terms of the ground going by (red needle).  I don't want to lose my true airspeed indicator either.  

I think what you're asking for is a fixed redline (not the moving red needle but a red area painted on the speedometer face) showing compression speed.  The problem is that compression speed varies by altitude and by control input.  A simple example is that you can be in a compressed dive and pull right out of it by manually trimming up elevators.

Also, many planes can be pushed safley beyond compression and recovered.

[Yoshimbo]

maybe like a thrid line on the speed o' meter that moves to show your "never exceed speed " according to altitude?

many planes can be pushed safley beyond compression and recovered

what do  you mean? elaborate if you will, i don't think i quite understand what you are saying here.

[BaldEagl]

Yoshimbo,  A plane compresses when the airflow over the surfaces becomes so fast that you can no longer operate the controls.  The speed of the airflow won't allow you to move the elevators, ailerons or rudder either individually or in combination effectively locking you in your dive.  This is the point which, when moved beyond, most pilots lawn dart.

There are ways to move beyond compression and recover however.  The simplest is to cut throttle until the airflow decreases enough to allow elevator control.  Another is to mannually trim elevators up.  This disrupts the airflow enough to re-allow full use of the elevators.  Rudder and rudder trim can also be used sometimes to create additional drag to slow the airflow but this should only be used if ailerons are also free allowing you to side-slip.  As soon as your slipping the elevators will be available again.

[TalonX]

This would be a bit confusing I think.  The never exceed speed is driven by the indicated speed.   The "fixed line" can be exceeded by the true air speed, but not the indicated.  This is due to the details given above...that is the density of air and the resultant forces.  Speed and air density determine the indicated air speed (and hence, the stresses).

The true air speed, always equal or higher than the indicated, is useful for knowing ground speed for planning purposes (how long will it take me to get there...).   Since we have no wind, true air speed = ground speed (in level flight).

In any event, I think it's better to learn the limits in your aircraft, and how it handles compressibility.  I don't think watching an airspeed indicator at that point is useful.  I imagine being in a dogfight, where I am only watching the other guy, not staring at gauges.

[Yoshimbo]

@BaldEagl


Ohhhhhhh, i see ok i misunderstood, tx

i read about using the trim like that a couple weeks ago and have been using it in the 109s and P47s...i must say, a real life saver.

[cav58d]

Complete waste of time.

[Stoney74]

Most of the U.S. aircraft didn't have colored markers on their airspeed indicators like G.A. aircraft today do.  Most had placards mounted on the panel indicating Vne and included altitude differences.  So, if you're a geek like me, you prefer the gauges to be as historically accurate as possible...

I use my airspeed indicator all the time during fights as its a good predictor, to me anyway, of what maneuvers are available to me--especially those involving the vertical.  In the Jug, for example, with 200 showing on the Airspeed Indicator, I know I can just barely immel the ship, whereas with 175 indicated, I won't try it at all.

It also helps, as has been described above, to learn the different speeds for your plane, as they are pretty accurately modelled.  I also keep an eye on the E6B for mach effect when I'm at high altitude.  If you start showing over .7 mach, its time to ratchet down the throttle or slow your decent, or both...

[Serenity]

First, lets get ACCURATE ASIs. Anyone noticed the spitfire's is wrong? And im sure its not the only one...