DVII and DR1 Air Speed Gauge

[FLS]

This is such a cool looking instrument.  I'm wondering how it actually works. It appears that it simply measures the rotation of the spinner on the top. It starts spinning when the prop starts but it doesn't show anything on the dial until the aircraft is moving forward. Once in the air it shows IAS instead of TAS. It seems like it should be showing TAS but I wonder how it would even work when it's located in the propwash.  So I'm curious about the real gauge as well as how it's modeled in Aces high.

[olds442]

This is such a cool looking instrument.  I'm wondering how it actually works. It appears that it simply measures the rotation of the spinner on the top. It starts spinning when the prop starts but it doesn't show anything on the dial until the aircraft is moving forward. Once in the air it shows IAS instead of TAS. It seems like it should be showing TAS but I wonder how it would even work when it's located in the propwash.  So I'm curious about the real gauge as well as how it's modeled in Aces high.

i think that it would read the wind off the prop but they would turn the needel to 0 so if the prop makes 20mph on idel the turn a noob till the needel goes to 0and so on

[hitech]

We have nothing in the game to make something spin based on airspeed. So the animation is simply hooked to the prop.

How they worked I would GUESS would simply be a small generator and a volt meter for the gauge.

2nd I believe they would measure true airspeed instead of airspeed , which is very undesirable.


HiTech

[FLS]

Thanks! True airspeed might have been useful if your biggest worry was going so fast things start to break.

[FLS]

On second thought things break from air pressure so that would probably still be IAS.

[Citabria]

things break based on ias just like irl.

tas is what you worry about at near compressability higher mach speeds.

for all intents and purposes in the low alt 25% fueltard ww1 arena TAS is irrelevant and only IAS is a concern at higher speeds near engine and structural failure.

[GNucks]

intents and purposes

Somebody on the internet actually wrote that expression correctly...

[colmbo]

2nd I believe they would measure true airspeed instead of airspeed , which is very undesirable.

Anything that works from the energy of the relative wind is going to be indicated airspeed -- unless this thing has an Air Data Computer in it. <G>

[FLS]

Wouldn't the advancing spoke add resistance proportional to the air density? Of course I don't know what resistance the generator would put on the axis and what portion of total resistance that would be.

[hitech]

Anything that works from the energy of the relative wind is going to be indicated airspeed -- unless this thing has an Air Data Computer in it. <G>

Based on the pitch of the prop, it will make a helix as it passes threw the air. Since there be almost zero slip of the prop due to no loading, the helix will not change dimension with speed or density.  And hence the same number of revolutions will be created per unit of travel regardless of the density.

This is very different from a modern pitot tube speed gauge that is messaging pressure/force on a diaphragm instead of speed with an air screw.

HiTech

[Sid]

naca-report-420.pdf - Aircraft Speed Instruments

[FLS]

Thanks Sid!