Standby Vacuum?

Jose wrote
I would not remove the T&B. If you add another AI, put it in a nearby
hole, but not the T&B. No other instrument provides turn rate
information.

After 47 years of civilian, military, and airline flying, I have
yet to see a reason for "turn rate" as long as I have a functioning
attitude indicator.

Bob Moore

Bob Moore wrote:
After 47 years of civilian, military, and airline flying, I have
yet to see a reason for "turn rate" as long as I have a functioning
attitude indicator.

As a recreational pilot of a simple IFR aircraft, I've recently
discovered a great role for the T&B; staying on heading. After a few
years of struggling to keep my non-AP equipped flivver on a MH, I've
re-discovered what many must know. The T&B is the best instrument to go
straight with. The AI gives you good info, and the heading gyro does
too, but the best way to keep it all centered in my Maule is definitely
the T&B. Especially in calm conditions.

Maule Driver wrote:
: As a recreational pilot of a simple IFR aircraft, I've recently
: discovered a great role for the T&B; staying on heading. After a few
: years of struggling to keep my non-AP equipped flivver on a MH, I've
: re-discovered what many must know. The T&B is the best instrument to go
: straight with. The AI gives you good info, and the heading gyro does
: too, but the best way to keep it all centered in my Maule is definitely
: the T&B. Especially in calm conditions.

I don't know if I'll agree with that. Once you dial in your wind correction
angle, the DG is the primary instrument for bank in straight-level flying.

When I was working on the instrument written, I tried to find easy ways to
remember primary vs supporting instruments for different stages of flight. One of my
conclusions was that for long-term accuracy, the instruments that provide the integral
of the chosen parameter are the most accurate, and thus "primary." For instance,
the result of a pitch change integrated gives you altitude, so it's primary for
straight-level. The result of a bank change integrated yields a heading, so the DG is
primary.

The trouble with direct-read indications is that they are not accurate enough
for long-term useage. The AI is good for radical attitude changes, but you cannot see
a 1/10 stdrad turn on either it or the T&B/TC. You *will* see it on the DG as the
numbers slows roll by.

Of course, to each their own. Just so long as you keep the shiny-side up!...


-Cory

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

Jose wrote:
I think that if you really feel the need for redundancy, the sensible
solution is replacing the T&B with an electric AI.


I would not remove the T&B. If you add another AI, put it in a nearby
hole, but not the T&B. No other instrument provides turn rate information.

Jose
If I remove the T&B the autopilot won't work!

Jose wrote:

No other instrument provides turn rate
information.

Why is rate of turn important compared to having another AI?

Why is rate of turn important compared to having another AI?

Because then you know how fast you're turning, which is new information.
Another AI only tells you the same thing you already know from the
first AI.

If you are asking which partial panel technique I prefer, I have found
that in the airplanes I fly (which are not very high performance), I am
more precise focusing on the TC than on the AI anyway. I'll defer to
those in high performance aircraft that in that case it's different, but
in an emergency, dropping the flaps and extending the gear should turn a
slippery high performance aircraft into a more stable platform to get
down in.

Jose
--
Quantum Mechanics is like this: God =does= play dice with the universe,
except there's no God, and there's no dice. And maybe there's no universe.
for Email, make the obvious change in the address.

Michael wrote:
What kind of airplanes do you have? I can understand wanting attitude
indication redundancy in a Bonanza, but it's overkill on a Skyhawk.

I'm of the general opinion that it's fairly difficult to go overboard
on safety equipment, though the C-150 with TCAS that I saw a year back
tripped even my meter.

I think that if you really feel the need for redundancy, the sensible
solution is replacing the T&B with an electric AI.

I'd agree with this. I have a 172 with the Precise Flight system that
was installed before I bought it and I certainly like having it. But
it's not really a cheap install and there is a recurring AD (unless
this is eliminated on new units?) so when you add it all in I doubt
it's much cheaper than the electric AI.

-cwk.

Mitty wrote:
Our club is looking at upgrading a couple of airplanes to Garmin 430s, etc.

It seems to me that standby vacuum would be a good thing to add, too.

1) Good idea? Do these systems really work?

2) Recommendations on type/brand/model?

- based on manifold vacuum, like Precise Flight: Inexpensive. Requires some
pilot training. Shuttle valve requires eventual maintenance. Even with training,
you might be surprised when you lose vacuum under some flight conditions (like
during a go-around). They work best when descending, stop working as you add power.

- separate electrically driven vacuum pump: heavy and expensive, but reliable.
Seamless operation. Turn it on and interpret all the gauges same as always.

- electrically driven attitude indicator: the models I know about have been
known to have quality problems, short life, frequent repair. Questionable value
if not in your scan (many seem to mount them on the copilot side).

- GPS with a pseudo-panel, like some of the recent Garmins: Might be OK in a
172-class aircraft. For faster and slipperier aircraft, I question whether
current models update fast enough to keep you out of trouble.

- solid-state gyros in a portable device: never seen one of these so I can't
comment, but some people are enthusiastic about them.

Did I miss any categories?

Dave

Dave Butler wrote:

Did I miss any categories?

Redundant engine driven vacuum pumps.
Quite common on twins and some of the bigger singles. The rub on
singles is having a place to mount the second one.

Ron Natalie wrote:

Redundant engine driven vacuum pumps.
Quite common on twins and some of the bigger singles. The rub on
singles is having a place to mount the second one.

Newer 172s (172R, 172S) even have dual vacuum pumps. That doesn't help
retrofitting, though.

- Andrew