411 413 inspection question

Unpleasant surprise on my .411 .413 check.

Person doing the check would not certify the inspection. He said that the
VSI is not connected to the pitot static system.

I am the first to say I am clueless about "systems". He said I would have
to take it to a certified repair place to get it fixed.

The VSI works, so I don't get this at all.

It passed 2 years ago, with no problems. Do things "disconnect" on it's
own or what's up with my VSI. Everything else appears to work just fine
(ASI, altimeter and VSI).

My plane does not have an alternate static in the plane.

What should I expect when I take it to a repair center?

Allen

On 5/17/2005 15:46, A Lieberman wrote:

Unpleasant surprise on my .411 .413 check.

Person doing the check would not certify the inspection. He said that the
VSI is not connected to the pitot static system.

I am the first to say I am clueless about "systems". He said I would have
to take it to a certified repair place to get it fixed.

The VSI works, so I don't get this at all.

Works, or appears to work. If it were not connected to the static source,
wouldn't it simply vent to the area behind the panel?


It passed 2 years ago, with no problems. Do things "disconnect" on it's
own or what's up with my VSI. Everything else appears to work just fine
(ASI, altimeter and VSI).

My plane does not have an alternate static in the plane.

What should I expect when I take it to a repair center?

Allen


--
Mark Hansen, PP-ASEL, Instrument Student
Sacramento, CA

On Tue, 17 May 2005 15:55:42 -0700, Mark Hansen wrote:

Works, or appears to work. If it were not connected to the static source,
wouldn't it simply vent to the area behind the panel?

Mark,

I plan to fly tomorrow to the practice area. What I am planning to do is
time the climb rate to see if it is registering correctly (I.E climb or
descend at 500 per minute).

I flew last week in IMC doing some ILS approaches in actual conditions and
I truly did not notice anything unusual about the VSI.

Like I said, I don't know anything about systems, other then when something
doesn't work, to get it to the repair shop and get it fixed.

As far as I knew before today, everything worked perfectly, so I was not
expecting any problems.

Allen

"A Lieberman" wrote in message
...
Unpleasant surprise on my .411 .413 check.

Person doing the check would not certify the inspection. He said that the
VSI is not connected to the pitot static system.


Interesting point. Although the VSI should be connected to the static
system, it is not required by 91.411 or FAR Appendix E. In other words, he
could have certified the system and you could have had an A&P investigate
why the VSI wasn't hooked to the static system afterwards.

The VSI will operate even though it is not connected the the official static
system. However, it should be fixed.

Mike

On Tue, 17 May 2005 19:28:37 -0500, Mike Ferrer wrote:

Interesting point. Although the VSI should be connected to the static
system, it is not required by 91.411 or FAR Appendix E. In other words, he
could have certified the system and you could have had an A&P investigate
why the VSI wasn't hooked to the static system afterwards.

Can an A&P work on the static system? Again, you are talking to a real
newbie even though I have owned the airplane for 2 1/2 years, so please
excuse the questions due to my ignorance.

The VSI will operate even though it is not connected the the official static
system. However, it should be fixed.

If this is such the case, why should it be hooked into the static system?
It seems to work good the way it is.

Also, one less instrument subject to failure should the pitot static system
go belly up?

Whatever the case, I want the plane to be as reliable as possible.

Allen

On Tue, 17 May 2005 20:05:31 -0700, Jim Burns wrote:

Talk with your instructor, pester your mechanic, watch, ask, listen, learn,
live, and fly safe!

Jim,

Thanks for your quality post! I am taking your advice to heart, especially
about watching the process and learning what could have gone wrong (and can
go wrong). Like you are implying, IMC is not the place to learn about what
is going wrong.....

I am trying to find a place that can check this out, and I am planning to
stay and observe if they allow me to do so. I was told the inspection
takes 2 hours without problems and 3 to 5 hours if problems are
encountered.

The last .411 and .413 check, I dropped the plane off, they did their
thing, and I picked it up. Because this came up, I am more interested in
getting the plane "right" rather then just passing the inspection.

Your above statement cannot be said any better. I am a strong believer
flying safe includes doing it right...

As far as the VSI, it's the original that came with the plane. Plane has a
little more then 2300 hours on it. I am planning down the road, upgrades,
but I do want to preserve what I have now, so I can do the upgrade right
the first time.

Allen

Allen,
For an instrument pilot especially, a complete understanding of all of your
airplanes systems is imperative. Your knowledge of the airplane systems
normal operations, failures, possible causes, and indications may be all
that saves you if you have a failure while IMC. A quick google for "pitot
static system" will bring up plenty of hits to start your way towards a
better understanding of why your VSI may appear to work but may also not be
connected to your static system. I would also strongly recommend sitting
down with your instructor and your mechanic for a quick review of your
aircrafts systems, possible failures, how to recognize them and the proper
decision making action to take once a failure occurs. While turning it over
to your local repair shop may be the easiest solution, you will get more for
your money if you stand over their shoulder, watch, learn, and ask plenty of
questions.

You also probably already know more than you think, don't sell yourself
short! You said that they told you the VSI was unhooked, right? Unhooked
from what? The only thing the VSI is hooked to is the static line, which
leads to the static port, typically on the exterior of the airplane so it
can vent to the outside static air pressure. Remember, the VSI is similar
to the altimeter, but instead of having a sealed bellows like the altimeter,
the VSI contains a bellows that has a small hole through which the air
pressure inside the bellows can slowly be equalized until it reaches the
outside static air pressure. Thus, measuring a "rate" of change in air
pressure which is indicated on the face of the VSI as a rate of climb or
descent.

Now, if it is unhooked, what is the VSI measuring? Well, since the
instrument is inside the cockpit, it must be reading the interior cockpit
air pressure. Now the question becomes, is there that much difference
between the outside air pressure and the inside air pressure? It "seems" to
be working, so it must be operational, but is it accurate? Normally, if you
have an alternate static source that is vented inside of the cockpit, when
you open it your VSI will momentarily indicate a climb because the cockpit
pressure is less than the outside air pressure but then it should settle
towards a normal indication. After this initial adjustment to the cabin air
pressure the accuracy of the indications of your VSI should be suspect due
to the non-constant air pressures inside the cockpit.

Truthfully, I'd be more concerned with your VSI sucking in dust and dirt due
to the lack of a filter than the accuracy of the instrument.

Talk with your instructor, pester your mechanic, watch, ask, listen, learn,
live, and fly safe!

Jim

Great Allen! I'd be willing to bet and I hope that you'll come away from
your experience with more questions than answers. Let us know what you
find!!

Knowledge about your airplane is like altitude below you, runway in front of
you, and fuel in your tanks.... the more you have, the better off you are
and the safer you are.

(Ok Ok, I know... unless you are out of oxygen or on fire, but you know what
I mean

Jim

A Lieberman wrote:

Can an A&P work on the static system? Again, you are talking to a real
newbie even though I have owned the airplane for 2 1/2 years, so please
excuse the questions due to my ignorance.

Yes, but it takes a repair facility who can do the appropriate tests to
recertify the plane for IFR after most static system work.

On 5/17/2005 16:54, A Lieberman wrote:

On Tue, 17 May 2005 15:55:42 -0700, Mark Hansen wrote:

Works, or appears to work. If it were not connected to the static source,
wouldn't it simply vent to the area behind the panel?

Mark,

I plan to fly tomorrow to the practice area. What I am planning to do is
time the climb rate to see if it is registering correctly (I.E climb or
descend at 500 per minute).

I flew last week in IMC doing some ILS approaches in actual conditions and
I truly did not notice anything unusual about the VSI.

If the VSI is vented to the cabin, you won't notice much of a difference.
Unless the cabin is pressurized, the air pressure will be slightly lower
than the actual static air pressure (from outside the cabin). However, when
you climb, the VSI will still show a climb, and at virtually the proper
rate.

Using the cabin air pressure as an "alternate" static source for the VSI
is fine in an emergency.


Like I said, I don't know anything about systems, other then when something
doesn't work, to get it to the repair shop and get it fixed.

Even thought you don't notice a problem, given that someone found that it is
not connected up properly, you should take this as a problem that needs
to be fixed ;-)


As far as I knew before today, everything worked perfectly, so I was not
expecting any problems.

Allen


--
Mark Hansen, PP-ASEL, Instrument Student
Sacramento, CA