Standby Vacuum?

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 *
************************************************** ***********************

On 8/18/2005 10:49, wrote:

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.

Here's another way to think about this.

I've done what Maule Driver is talking about, and think of it rather
like using the VSI to assist in maintaining altitude. I use the VSI
to give me an indication that an altitude change is coming, and I need
to anticipate it and correct (the VSI doesn't react all that quickly,
but still...)

If I do this right, I never see the altitude change. Of course,
this doesn't change the fact that the altimeter is the primary pitch
instrument - it's just not the only pitch instrument.

So ... I do the same with the T&B giving me an indication that a turn
is coming, and I can anticipate it and react. The DG is still the final
authority as to whether or not you're heading in the right direction, but
I think it's better to keep it on the heading, rather than notice it's
not and having to correct (when the turbulence allows, of course ;-) )



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 *
************************************************** ***********************



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

Mark Hansen wrote:
: I've done what Maule Driver is talking about, and think of it rather
: like using the VSI to assist in maintaining altitude. I use the VSI
: to give me an indication that an altitude change is coming, and I need
: to anticipate it and correct (the VSI doesn't react all that quickly,
: but still...)

: If I do this right, I never see the altitude change. Of course,
: this doesn't change the fact that the altimeter is the primary pitch
: instrument - it's just not the only pitch instrument.

: So ... I do the same with the T&B giving me an indication that a turn
: is coming, and I can anticipate it and react. The DG is still the final
: authority as to whether or not you're heading in the right direction, but
: I think it's better to keep it on the heading, rather than notice it's
: not and having to correct (when the turbulence allows, of course ;-) )


Sure... they're all related of course. I guess the point I was trying to make
is that (barring turbulence), I don't *see* a change in VSI/AI/T&B in straight/level
cruise. A certain amount of pressure on the controls will fix small errors in DG/ALT.
Those are typical in non-turbulent flight, and there will be no perceptible indication
from the VSI/AI/T&B. For anything other than a minute change (e.g. turbulence) the
other indicators are better and then line up on the "primaries" (DG/ALT).

Like I said... to each their own. Probably saying the same thing anyway...

-Cory
--

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

Its a good idea if you can't afford a standby electric attitude
indicator. I've had more indicators fail then pumps myself.

-Robert

If your attitude indicator fails and you have a back up, you just look
at the other attitude indicator (this is what the airlines and military
teach).
If your attitude indicator fails and you have precise flight, you learn
to fly with the turn coordinator alone.

-Robert

Peter R. wrote:
Michael 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 see that Sporty's is encouraging this option, too, with their electric
AI.

However, doesn't the AI have the potential to tumble in an unusual
attitude? During my IFR training I recall learning that the turn
coordinator will not tumble in an unusual attitude scenario whereas the AI
may. Since recovery from an unusual attitude was taught to me by first
going to the TC, I would be hesitant to replace an instrument so reliable
during a UA.

What say you?


Vacuums tumble.

Saw it on Dave Letterman, "throwing household appliances off a building".

Peter R. wrote:
Michael wrote:


I see little chance of that happening with dual AI's, and even less
chance that the average pilot will recover from an aerobatic attitude
partial panel after screwing up enough to get into that mess.


Interesting that you pointed that out. I was thinking the same thing when
I posed the question but thought that two tumbling AIs would pretty much
guarantee that the pilot would not recover.


But hey - if you have the panel room, why not keep the electric TC too?


My Bonanza has the original TC along with a backup electric AI located to
the left of the TC. However, the electric AI keeps precessing and requires
a reset about four times per hour, which concerns me.


What brand ?

Stubby wrote:

Scott Moore wrote:

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?

TIA


Electric attitude. Vacuum pumps are going away.


But, can't an electric attitude indicator fail? Bearings wear out.
I've suffered that on a hard disk. Are there any MTBF numbers for the
two systems?

I have heard that EAIs have better fail numbers than vac, but sure, its
nonzero.

The reason why all electric panels are becoming common is because
electrical systems are more reliable than vacuum, and backup is easier to
provide for everything, a second battery. It also makes more sense to
unify around a single system, instead of having a hodge-podge of two
different systems.

I would go all electric and remove my vac pump, but I blew it and
got an NSD-360. The first repair bill for that utter piece of defective
junk easily pushed the total cost above what an all electric solution
would have cost (i.e., $5000 for the NSD360, and $4000 to get it to
work correctly).

wrote:
Seems that the best redundancy is a rate based autopilot (read STEC).
Since it is based on, and runs on, a turn indicator the issue of
whether yo have a good one is solved. However I still have an electric
backup vacuum pump in my C172.


I really believe this. The TC won't tumble. It comes down to two things:

1. If you have the presence of mind to engage the AP if the AI goes south.
Of course, in most IFR situations, the chances are good the AP is already
on.

2. Although the standard "ethic" says that engaging the AP during a loss
of control is a good idea, I tend to doubt it. The STEC has limits on what
control pressures it will tolerate, and the result can be for it to
simply disengage if it cannot overcome them.

Peter wrote:
: It took me a while to work out what the FAA was looking for in the IR
: written, on "primary" and "supporting". It's easy enough in straight
: and level flight, but on stuff like a transition from a stabilised
: level turn to a climbing constant-speed turn, it's very hard to get
: one's head around it. Luckily, I passed, and one has to learn these
: word tricks only once
:

Yeah, me too... that's why I came up with what I did (in my own mind, anyway).
Basically, it was something like:
attitude = rate = result

So, during the phases of flight while you are transitioning, the attitude is
generally the most important. Holding rates (CR climb, SR turn, etc) it's
rate-based
like VSI or TC. Result is the integral thing.

Anyway, I agree... I passed and now you just need to know how to do it, not
some cryptic wordplay to pass an exam.

-Cory


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