ALTIMETER

[The Hangman]

Hi, could anyone render some advice as to what would remedy my Altimeter.
when in flight it seems to jump or wobble between readings as if the damping does not work.
Would I need to get a new ALT. or can this be fixed? could I put something in the air intake line to help with this problem?
any advice is welcome...
The Hangman.

[AndyG]

Hi, could anyone render some advice as to what would remedy my Altimeter.
when in flight it seems to jump or wobble between readings as if the damping does not work.
Would I need to get a new ALT. or can this be fixed? could I put something in the air intake line to help with this problem?
any advice is welcome...
The Hangman.

Why would your altimeter have an air intake line. Are you maybe talking about the pitout on your airspeed indicator? that must be left unobstructed and free.

[thys bas]

Hangman,

you are correct in mentioning the "air inlet". It is the "static" air measure point and should measure the air pressure outside the aircaft without positive or negative pressure which could be generated by the forward air speed. You probably do not have a pipe leading to the side of the aircraft where such a "un-influenced" still air pressure can be picked up, and the altimeter is picking up the buffeting air pressure inside the aircraft. Have a look at another aircraft's installation where there is a pitot and static pickup, make yours the same. Don't go buy a new instrument. (Apparently the Air France Airbus which crashed had this Static point frozen over in very bad freezing rain at high altitude and incorrect altitude and speed info was given to the computer, which then decided the aircraft was overspeeding at the wrong altitude, closed throtttles, and splash!...... something like that). Fortunately we do not have autopilot and all we are stuck with is the wobble in the needle

[Goose]

Hangman,

Have a look at another aircraft's installation where there is a pitot and static pickup, make yours the same. Fortunately we do not have autopilot and all we are stuck with is the wobble in the needle

Or ask the builder of THE plane how he fixed the new planes "wobble in the needle"

[AndyG]

I think Thys has nailed it on the head.

[MAGNIficent]

Altimeter only have the STATIC Port, which is connected with the Airspeed indicator STATIC port to have the same pressure.
This connected ports will have a small 2mm hole to pick up the equalized static pressure.

[sailor]

A scetch of how to connect your instruments.

Pitot-Static.jpg (35.16 KiB) Viewed 1707 times

[The Hangman]

Thanks I will take a look at the piping. the aircraft has two static vents, which are open. I have noticed that some of the piped connections tned to come loose.
However on the pre-flight this usually all looks connected.
I will update you when I have examined this all again closely.

[The Hangman]

Hi All,
Just to follow up with regards to the wobbly ALT.
I was fortuneate enough to go fly again in calm weather.... for a cahnge. after a close inspection on the gauge and all the pipng we went up.
this time the alt. was still a bit shaky but not that bad. as time went on and the wind died down a bit the gauge started to become more stable.
I think it is just a inconsistant airflow into the tubes/static venst causing the wobble. maybe a large compensator chamber in the line will help or maybe an internal static vent?
Thanks for all the advice ..