REFLECTOR: Static port calibration
Scott Derrick
scott at tnstaafl.net
Thu Mar 5 17:57:57 CST 2009
I agree. Two uncalibrated ports would probably be just twice as bad as
one uncalibrated port.
I'm mystified why people are so reluctant to do it? Its butt simple.
On the next flight, going anywhere, make a low pass on departure or
arrival. Note which way or how much the error is, add a single or
multiple layers of metal tape to the port. Repeat until its correct.
Done until you paint the airplane again. You could probably pull the
layers of tape off when done, measure the thickness and fabricate an
aluminum fence of the same thickness and permanently rivet it on.
Scott
Scott Baker wrote:
> hi jack
> i don't think dual static ports are guaranteed to help neutralize
> static system pressure. it may even multiply errors!
> sb
>
> ----- Original Message -----
> *From:* Jack Prock <mailto:jackprock at comcast.net>
> *To:* Velocity Aircraft Owners and Builders list
> <mailto:reflector at tvbf.org>
> *Sent:* Wednesday, March 04, 2009 6:24 PM
> *Subject:* Re: REFLECTOR: Static port calibration
>
> Scott,
>
> Do you see any benefit to having two static ports, one on each side?
>
> Jack
>
> ----- Original Message -----
> *From:* Scott Baker <mailto:sbakr at comcast.net>
> *To:* Velocity Aircraft Owners and Builders list
> <mailto:reflector at tvbf.org>
> *Sent:* Wednesday, March 04, 2009 3:20 PM
> *Subject:* Re: REFLECTOR: Static port calibration
>
> A typical static system installation includes the connection
> of the altimeter; air speed; VSI; and altitude encoder.
> Sometimes autopilots with altitude/vertical speed control
> functions are connected to the same static source; and
> sometimes they have their own static source.
>
> The placement of the static source determines what pressures
> influence the static system. A static port located in a high
> pressure area, for example, will cause air speed indicator to
> erroneously report lower than actual numbers. The degree of
> error differs with the aircraft air speed and altitude, since
> both affect 'pressure' on the static port. It's possible to
> get correct readings at one altitude and air speed - and large
> errors at different altitudes and air speeds. We obviously
> want to locate the static pressure port in a neutral air
> pressure area. In the Velocity design, the best location for
> the static port is halfway down the fuselage (just behind the
> rear door beams). Even then, air pressures may be present to
> the degree that they cause errors in the static instruments.
> When this occurs we can install a fence (a small air dam made
> of wood, plastic, or whatever) near the static port. To
> reduce the pressure on the static system, install the fence in
> front of the static port. To increase pressure, install the
> fence behind the static port. The height of the fence
> determines the amount of pressure change. Correcting static
> errors often turns into a trial and error process of flying,
> measuring, and then altering the height of the fence.
>
> Some EFIS systems allow field calibration of the altimeter and
> air speed. Correcting static errors becomes a simple process
> - go fly with keyboard in hand, and enter the correct values
> on the calibration scale. Those who want to impress their
> friends and neighbors are able to display 300 knots on the top
> end simply by changing the calibration scale. We at the
> factory would never do that, of course!
>
> Regarding the question about the altitude reported by the
> transponder. The transponder receives its altitude
> information from the altitude encoder. Encoders must be
> inspected and calibrated by a licensed shop every 24-months.
> The inspection and calibration is done with the aircraft
> standing still (static pressure is neutral). Static pressure
> differences during flight (see above) affect the accuracy of
> the altitude being reported by the encoder. One would assume
> that the same error would appear on the stand alone
> altimeter. Pilot and ATC controller should be seeing the same
> altitude - but the reported altitude may not be accurate
> because of static errors! It is a good idea to test the
> accuracy of the system - comparing side by side aircraft
> performance with a friend - or maybe with WAAS GPS altitude.
>
> Scott B.
>
>
>
>
>
>
> ----- Original Message -----
> *From:* aminetech at bluefrog.com
> <mailto:aminetech at bluefrog.com>
> *To:* Velocity Aircraft Owners and Builders list
> <mailto:reflector at tvbf.org>
> *Sent:* Wednesday, March 04, 2009 1:16 PM
> *Subject:* Re: REFLECTOR: Static port calibration
>
> If ATC is seeing the altitude transmitted by your
> transponder, naturally it will be identical, assuming you
> are reading from the same instrument that feeds the
> transponder. Am I missing something?
>
> John
>
> --- ALVentures at cox.net <mailto:ALVentures at cox.net> wrote:
>
>
>
>
>
> I’ve always found my altitudes consistent with where ATC
> says I am – so I don’t think I need to change anything.
>
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