v-speeds database

[[email protected]]

Hello builders,
There's a v-speed database and we'd like to have it populated. Please put
in the appropriate v speeds for the aircraft that you fly. A nice
database will help everyone.

it's free.

www.aviationist.com/vspeeds-form.html

enjoy


--
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"And let's get one thing straight. There's a big difference between a
pilot and an aviator. One is a technician; the other is an artist in love
with flight." -- E.B. Jeppesen

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[Kevin Horton]

On Mon, 11 Jul 2005 13:17:44 -0400, nospam wrote:

> Hello builders,
> There's a v-speed database and we'd like to have it populated. Please put
> in the appropriate v speeds for the aircraft that you fly. A nice
> database will help everyone.
>
> it's free.
>
> www.aviationist.com/vspeeds-form.html
>

I can perhaps understand the interest in this database, but I questionits usefulness for homebuilt aircraft. The values in the database arein Indicated Airspeed (IAS). But, the aircraft has no idea what speedis indicated on the airspeed indicator - it only knows EquivalentAirspeed (EAS), which is effectively the same as Calibrated Airspeed(CAS) if the speed is less than 200 kt and the altitude is below 10,000ft.In an ideal world, IAS would equal CAS. But, in the real world, thereis static source position error and Airspeed Indicator (ASI) instrumenterror. And both these errors will vary from aircraft to aircraft. Ihave communicated with an RV owner who had a large enough static sourceposition error to result in about a 10 kt airspeed error. An RV-8builder reported a 22 mph airspeed error, which he corrected bymodifying his flush static ports. I have also read reports frombuilders who discovered 5 to 10 kts of instrument error in their ASIswhen they checked them with a water manometer.So, even if the homebuilt aircraft builder does a very accurate flighttest program to determine the V-speeds for his aircraft, the IAS V-speednumbers are only valid for his aircraft. If your aircraft has adifferent static source position error (maybe you used a flush staticport instead of Van's pop-rivet design), or your ASI has a differentinstrument error than his, then your V-speeds in IAS will be different. The difference between his V-speeds and yours could easily be greaterthan 10 KIAS, even if the two aircraft are identical in every other way.And, there are many variations in engines and props, which furtheraffect the climb and descent V-speeds.So, if you have a type-certificated aircraft, where the static systemsare identical by design, and the manufacturer does production flighttesting to confirm the stall IAS and cruise IAS are within histolerances, then you can simply use the V-speeds in your POH. You don'tneed this database.If you have a homebuilt aircraft, it could be dangerous to assume thatthe V-speed data that someone else gave you is applicable to youraircraft. Someone else's V-speed data might be better than nothing, inthe period between your first flight and when you have completed yourown V-speed flight testing. But you shouldn't use this database as asubstitute for determining your own V-speeds via flight test.

--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/
e-mail: khorton02(_at_)rogers(_dot_)com