After having both a vac pump failure and an AI failure (not on the
same flight :) ) I decided its really time for a backup. I always
consider my Mooney to be an "IFR anytime" type of plane, in that I
consider it a solid IFR platform. When the vac pump goes out alarms
starting sounding, my voice annunicator starting saying "check vac
pressure" and the needle goes to 0. It's pretty obvious. I do a
voluntary IPC every 6 months with a local DE and always do partial
panel approaches so I'm as comfortable as you can be with that. A
couple weeks ago I had my AI go out. WOW, that's another story!! The
thing slowly rolled 30 degrees off and REMAINED RESPONSIVE!! When I
banked, it banked, when I pitched, it piched. Figuring out that it was
dead could be hard and it would be easy to miss it. I decided I need a
back up and those vac backup systems are a waste of money(Precise
Flight, electric vac, etc). After getting it back from overhaul my
partner reported that it did it again! I called a couple gyro places
and they said the vac AIs don't last very long because they have a
stream of "dirty" air running through them. The electrics last much
longer. So I'm getting an electric AI installed as my backup. I
noticed that the non-TSO'd electric AIs are almost $1000 less than the
TSO'd ones. I asked my mechanics and the FSDO and they said I could
probably get a 337 approved by the FSDO for a non-TSO'd unit as long
as it wasn't in the "T" area of the panel. One FSDO guy said I might
need to label it "VFR only" and I'd have to promise not to do 135. In
either case I'll end up having an electric backup AI for under $1500.
That's less than the price of a backup electric vac pump installed
about about the same price to put a Precise Flight in a Mooney (with
California labor rates of $95/hr ) with twice the redundency.

-Robert

Robert M. Gary wrote:
> After having both a vac pump failure and an AI failure (not on the
> same flight :) ) I decided its really time for a backup. I always
> consider my Mooney to be an "IFR anytime" type of plane, in that I
> consider it a solid IFR platform. When the vac pump goes out alarms
> starting sounding, my voice annunicator starting saying "check vac
> pressure" and the needle goes to 0. It's pretty obvious. I do a
> voluntary IPC every 6 months with a local DE and always do partial
> panel approaches so I'm as comfortable as you can be with that. A
> couple weeks ago I had my AI go out. WOW, that's another story!! The
> thing slowly rolled 30 degrees off and REMAINED RESPONSIVE!! When I
> banked, it banked, when I pitched, it piched. Figuring out that it was
> dead could be hard and it would be easy to miss it. I decided I need a
> back up and those vac backup systems are a waste of money(Precise
> Flight, electric vac, etc). After getting it back from overhaul my
> partner reported that it did it again! I called a couple gyro places
> and they said the vac AIs don't last very long because they have a
> stream of "dirty" air running through them. The electrics last much
> longer. So I'm getting an electric AI installed as my backup. I
> noticed that the non-TSO'd electric AIs are almost $1000 less than the
> TSO'd ones. I asked my mechanics and the FSDO and they said I could
> probably get a 337 approved by the FSDO for a non-TSO'd unit as long
> as it wasn't in the "T" area of the panel. One FSDO guy said I might
> need to label it "VFR only" and I'd have to promise not to do 135. In
> either case I'll end up having an electric backup AI for under $1500.
> That's less than the price of a backup electric vac pump installed
> about about the same price to put a Precise Flight in a Mooney (with
> California labor rates of $95/hr ) with twice the redundency.

FWIW, I have an electric AI in my Mooney and I wouldn't do it again. It's
expensive, failure prone, and too far out of my scan to be useful as a backup.

I've had the Precise Flight system in a previous airplane, and it was OK, but
has some drawbacks. Since it depends on the intake manifold as a vacuum source,
the vacuum available is dependant on throttle setting. In order to maintain
vacuum for the instruments, you may need a throttle setting that's not what
you'd prefer.

I now have the Aero-Advantage STCed dual-rotor vacuum pump and think it is
overall the best solution. It offers more redundancy and more reliable backup
for a reasonable price. http://www.aeroadvantage.com

Including installation it will be less than your electric AI, and a better
solution, IMO.

Dave
Remove SHIRT to reply directly.

On 20 Feb 2004 08:49:48 -0800, (Robert M. Gary)
wrote:

>After having both a vac pump failure and an AI failure (not on the
>same flight :) ) I decided its really time for a backup. I always
>consider my Mooney to be an "IFR anytime" type of plane, in that I
>consider it a solid IFR platform. When the vac pump goes out alarms
>starting sounding, my voice annunicator starting saying "check vac
>pressure" and the needle goes to 0. It's pretty obvious. I do a
>voluntary IPC every 6 months with a local DE and always do partial
>panel approaches so I'm as comfortable as you can be with that. A
>couple weeks ago I had my AI go out. WOW, that's another story!! The
>thing slowly rolled 30 degrees off and REMAINED RESPONSIVE!! When I
>banked, it banked, when I pitched, it piched. Figuring out that it was
>dead could be hard and it would be easy to miss it. I decided I need a
>back up and those vac backup systems are a waste of money(Precise
>Flight, electric vac, etc). After getting it back from overhaul my
>partner reported that it did it again! I called a couple gyro places
>and they said the vac AIs don't last very long because they have a
>stream of "dirty" air running through them. The electrics last much
>longer. So I'm getting an electric AI installed as my backup. I
>noticed that the non-TSO'd electric AIs are almost $1000 less than the
>TSO'd ones. I asked my mechanics and the FSDO and they said I could
>probably get a 337 approved by the FSDO for a non-TSO'd unit as long
>as it wasn't in the "T" area of the panel. One FSDO guy said I might
>need to label it "VFR only" and I'd have to promise not to do 135. In
>either case I'll end up having an electric backup AI for under $1500.
>That's less than the price of a backup electric vac pump installed
>about about the same price to put a Precise Flight in a Mooney (with
>California labor rates of $95/hr ) with twice the redundency.
>
>-Robert

Let us know how the papework goes with the FSDO. I've heard it is not
easy (paperwork-wise) to install the non-certified ones in the panel.

Dave Butler > wrote in message >...
> I now have the Aero-Advantage STCed dual-rotor vacuum pump and think it is
> overall the best solution. It offers more redundancy and more reliable backup
> for a reasonable price. http://www.aeroadvantage.com
>
> Including installation it will be less than your electric AI, and a better
> solution, IMO.

I'm not so worried about losing the vac. What I'm worried about is
lossing the AI.

BTW: What is the purpose of the dual rotor pump. When my pumps have
gone out its always been because a vain got stuck and sheared off the
pump shaft. My mechanic said that's how they usually fail. Wouldn't
that kill both rotors?
-Robert

(Robert M. Gary) wrote
> noticed that the non-TSO'd electric AIs are almost $1000 less than the
> TSO'd ones. I asked my mechanics and the FSDO and they said I could
> probably get a 337 approved by the FSDO for a non-TSO'd unit as long
> as it wasn't in the "T" area of the panel. One FSDO guy said I might
> need to label it "VFR only" and I'd have to promise not to do 135.

As a sincere point of inquiry, would someone please point me to
the parts of the FAR that require an attitude gyro/indicator to
be TSO'ed. I thought that for part 91 ops, the only items that
required TSO compliance were the transponder and an IFR GPS.

Bob Moore

> Robert M. Gary wrote:
> > After having both a vac pump failure and an AI failure (not on the
> > same flight :) ) I decided its really time for a backup.

I had a similar revelation recently, after a challenging IPC at night
and a quiet reflection on a AI that did fail one me, albeit on a nice
day. Did lot of soul searching and decided to postpone a GPS upgrade
in favor of some attitude information backup first.

Dave Butler > wrote:

> FWIW, I have an electric AI in my Mooney and I wouldn't do it again. It's
> expensive, failure prone, and too far out of my scan to be useful as a backup.

Did you have a lot of problems with the electric AI ? I am also
considering one (the dual pumps sound promising, but still don't back
up the gyro...), so I am curious how they hold up (the RCA-26 series
or the non-TSO'd Falcon, the AIM / Midcontinet stuff is just too
expensive). I heard mixed reviews on the RC Allen, some people have
had them for years without any problems and some claim they they don't
hold up as well as quality vacuum gyros.

Re Falcon, I strongly considered the possibility (337 or not), but
with a custom tilt they are over $1100 (Chief), not *that* cheap
considering a brand new RCA goes for $1650 at the discounters (like
Spruce), factory tilt included and less paperwork hassle. Still, $500
is money, so if they are OK, might be worth considering. There seems
to be very little info on them besides the manufacturer,
unfortunately....

Thanks,

Martin

There are some non-TSO's EFIS systems around for under $2000! I saw
one at Oshkosh and was impressed! No moving parts, fully electronic.
Check out
http://www.dynonavionics.com

Doug

Robert M. Gary > wrote:
>I'm not so worried about losing the vac. What I'm worried about is
>lossing the AI.


Am I missing something? How is installing a 2nd AI going to solve
the problem of identifying an inaccurate indication? The old saying
goes, "A man with one watch knows the time, a man with two watches
is never sure." If you have two AIs and they disagree, how will you
determine which one is correct? You will have to cross check against
the DG and TC, same as you would if you had only one AI. Seems to me
a better approach would be to practice cross-check in a simulator,
where you can practice with an erratic AI rather than simply covering
it up.


Ross Oliver

>>
If you have two AIs and they disagree, how will you
determine which one is correct?
<<

You at least know one has gone south, and you can go PP. With only one AI, you
could be leaning first.

Jose



--
(for Email, make the obvious changes in my address)

Robert,

There was a recent article in Aviation Consumer about this (not sure if you
subscribe):

http://www.aviationconsumer.com/archives/34_1/safety/5307-1.html

Among other things, they discuss: dual chamber vac with a backup gyro and
PDA-style all electronic backups. If memory serves, a dual chamber vac with
a backup gyro is not terribly expensive and probably wouldn't require fancy
paperwork. I think they quote a price in the ballpark of $2000 for that
solution. The PDA-style all electronic solution is a bit more pricey and
wouldn't be panel mount.

mark

"Robert M. Gary" > wrote in message
om...
> After having both a vac pump failure and an AI failure (not on the
> same flight :) ) I decided its really time for a backup. I always
> consider my Mooney to be an "IFR anytime" type of plane, in that I
> consider it a solid IFR platform. When the vac pump goes out alarms
> starting sounding, my voice annunicator starting saying "check vac
> pressure" and the needle goes to 0. It's pretty obvious. I do a
> voluntary IPC every 6 months with a local DE and always do partial
> panel approaches so I'm as comfortable as you can be with that. A
> couple weeks ago I had my AI go out. WOW, that's another story!! The
> thing slowly rolled 30 degrees off and REMAINED RESPONSIVE!! When I
> banked, it banked, when I pitched, it piched. Figuring out that it was
> dead could be hard and it would be easy to miss it. I decided I need a
> back up and those vac backup systems are a waste of money(Precise
> Flight, electric vac, etc). After getting it back from overhaul my
> partner reported that it did it again! I called a couple gyro places
> and they said the vac AIs don't last very long because they have a
> stream of "dirty" air running through them. The electrics last much
> longer. So I'm getting an electric AI installed as my backup. I
> noticed that the non-TSO'd electric AIs are almost $1000 less than the
> TSO'd ones. I asked my mechanics and the FSDO and they said I could
> probably get a 337 approved by the FSDO for a non-TSO'd unit as long
> as it wasn't in the "T" area of the panel. One FSDO guy said I might
> need to label it "VFR only" and I'd have to promise not to do 135. In
> either case I'll end up having an electric backup AI for under $1500.
> That's less than the price of a backup electric vac pump installed
> about about the same price to put a Precise Flight in a Mooney (with
> California labor rates of $95/hr ) with twice the redundency.
>
> -Robert

(Ross Oliver) wrote in message >...
> Robert M. Gary > wrote:
> >I'm not so worried about losing the vac. What I'm worried about is
> >lossing the AI.
>
>
> Am I missing something? How is installing a 2nd AI going to solve
> the problem of identifying an inaccurate indication? The old saying
> goes, "A man with one watch knows the time, a man with two watches
> is never sure." If you have two AIs and they disagree, how will you
> determine which one is correct? You will have to cross check against
> the DG and TC, same as you would if you had only one AI. Seems to me
> a better approach would be to practice cross-check in a simulator,
> where you can practice with an erratic AI rather than simply covering
> it up.

I think you are missing something. If both AIs start showing different
results you will be suspecious and start asking questions. As I noted
a realistic AI failure situation can be very difficult to detect.

(Doug) wrote in message >...
> There are some non-TSO's EFIS systems around for under $2000! I saw
> one at Oshkosh and was impressed! No moving parts, fully electronic.
> Check out
> http://www.dynonavionics.com

You can also buy a solid stage gyro that feeds your IPAQ. If you use
AnywhereMap as your GPS already you can just switch modes. However,
having a dedicted instrument sounds like the best solution to me. I'm
probably going to postpone my traffic watch system in favor of the
electric AI.

In article >,
(Robert M. Gary) wrote:
> I think you are missing something. If both AIs start showing different
> results you will be suspecious and start asking questions. As I noted
> a realistic AI failure situation can be very difficult to detect.

How is this fundamentally different than if one AI disagrees with the DG
and turn coordinator? I try not to stare at the AI the entire time, and
it seems that a scan would pick up a discrepency regardless of whether
it included a second AI. Now, flying the plane with a second AI may be
easier once the failed AI is identified, but I don't see how a second AI
would make identifying the failure any easier, because it would be a
required scan item just like the DG and turn and bank.


JKG

>>
How is this fundamentally different than if one AI disagrees with the DG
and turn coordinator?
<<

You don't know which to trust, and you are out of bullets. You have to figure
out which one is lying. Besides, you can bank while remaning straight, and
you can be level while turning.

With two AIs, you can go PP and use the TC and DG (and ball).

Jose

--
(for Email, make the obvious changes in my address)

Jonathan Goodish > wrote in message >...
> In article >,
> (Robert M. Gary) wrote:
> > I think you are missing something. If both AIs start showing different
> > results you will be suspecious and start asking questions. As I noted
> > a realistic AI failure situation can be very difficult to detect.
>
> How is this fundamentally different than if one AI disagrees with the DG
> and turn coordinator?

Because, a real world situation is that the AI dies very, very slowly.
There isn't that immediate "hmm, somethings wrong" like with a dead
vac (alarms going off etc). The TC has enough bounce in it that there
is really no way to detect small differences like 5 degrees when you
are in real IMC. Once you start bouncing around in the clouds the TC
starts bouncing back and forth. It will keep you upright but is far
from close enough to determine 5 or perhaps even 10 degrees off. The
DG you may or may not notice. In anycase two AIs being off is a pretty
quick and certain thing to notice.

Couple that with the fact that you have to decide which is right, the
TC or the AI. If you have 3 its easier to pick on that might be bad.

Robert M. Gary wrote:
> Dave Butler > wrote in message >...
>
>>I now have the Aero-Advantage STCed dual-rotor vacuum pump and think it is
>>overall the best solution. It offers more redundancy and more reliable backup
>>for a reasonable price. http://www.aeroadvantage.com
>>
>>Including installation it will be less than your electric AI, and a better
>>solution, IMO.
>
>
> I'm not so worried about losing the vac. What I'm worried about is
> lossing the AI.
>
> BTW: What is the purpose of the dual rotor pump. When my pumps have
> gone out its always been because a vain got stuck and sheared off the
> pump shaft. My mechanic said that's how they usually fail. Wouldn't
> that kill both rotors?
> -Robert

I understand your skepticism, but AeroAdvantage claims that they have a
mechanical arrangement that allows each rotor to fail independently. Check the
web site for more details, but if my memory serves it amounts to providing weak
points (necking) in the shaft in such a way that the shaft for each rotor can
fail independently. I have had trouble visualizing what the mechanical
arrangement is and would like to take one apart or see an exploded drawing to
see how they do that. I can't explain exactly how it's done, but they convinced
me to my satisfaction that they had solved the problem.

Dave
Remove SHIRT to reply directly.

Martin Kosina wrote:
>>Robert M. Gary wrote:
>>
>>>After having both a vac pump failure and an AI failure (not on the
>>>same flight :) ) I decided its really time for a backup.
>>
>
> I had a similar revelation recently, after a challenging IPC at night
> and a quiet reflection on a AI that did fail one me, albeit on a nice
> day. Did lot of soul searching and decided to postpone a GPS upgrade
> in favor of some attitude information backup first.
>
> Dave Butler > wrote:
>
>
>>FWIW, I have an electric AI in my Mooney and I wouldn't do it again. It's
>>expensive, failure prone, and too far out of my scan to be useful as a backup.
>
>
> Did you have a lot of problems with the electric AI ? I am also
> considering one (the dual pumps sound promising, but still don't back
> up the gyro...), so I am curious how they hold up (the RCA-26 series
> or the non-TSO'd Falcon, the AIM / Midcontinet stuff is just too
> expensive). I heard mixed reviews on the RC Allen, some people have
> had them for years without any problems and some claim they they don't
> hold up as well as quality vacuum gyros.

The electric gyro in my Mooney was installed before I bought into the
partnership, so I don't know all the details, but I think it's been in there
about 10 years or so, and has been overhauled twice. Each overhaul cost about
the same as the original purchase price.

Sorry, I don't know which brand it is. If I can find out, I'll post it.

The installation in my airplane is over on the copilot's side, so it's way out
of my scan and therefore pretty much worthless. I'd go partial panel with the
turn coordinator and mag compass before I'd try to use a gauge so far out of my
scan. If you install an electric, be sure to put it where you can see it.

Dave
Remove SHIRT to reply directly.

>
> Re Falcon, I strongly considered the possibility (337 or not), but
> with a custom tilt they are over $1100 (Chief), not *that* cheap
> considering a brand new RCA goes for $1650 at the discounters (like
> Spruce), factory tilt included and less paperwork hassle. Still, $500
> is money, so if they are OK, might be worth considering. There seems
> to be very little info on them besides the manufacturer,
> unfortunately....
>
> Thanks,
>
> Martin


--
Dave Butler, software engineer 919-392-4367

Mark Astley wrote:
> Robert,
>
> There was a recent article in Aviation Consumer about this (not sure if you
> subscribe):
>
> http://www.aviationconsumer.com/archives/34_1/safety/5307-1.html
>
> Among other things, they discuss: dual chamber vac with a backup gyro and
> PDA-style all electronic backups. If memory serves, a dual chamber vac with
> a backup gyro is not terribly expensive and probably wouldn't require fancy
> paperwork. I think they quote a price in the ballpark of $2000 for that
> solution. The PDA-style all electronic solution is a bit more pricey and
> wouldn't be panel mount.

Aviation Consumer's original article on the subject, written by Coy Jacobs, was
pretty negative on the dual vacuum pump. In a later article, maybe the one
referenced above, they were more positive about it. I think I paid $745 for the
dual rotor pump on an "Oshkosh Special" price. AeroAdvantage says 4-8 hours to
install, mine took 6 hours on an M20J.

Dave
Remove SHIRT to reply directly.

>
> mark
>
> "Robert M. Gary" > wrote in message
> om...
>
>>After having both a vac pump failure and an AI failure (not on the
>>same flight :) ) I decided its really time for a backup. I always
>>consider my Mooney to be an "IFR anytime" type of plane, in that I
>>consider it a solid IFR platform. When the vac pump goes out alarms
>>starting sounding, my voice annunicator starting saying "check vac
>>pressure" and the needle goes to 0. It's pretty obvious. I do a
>>voluntary IPC every 6 months with a local DE and always do partial
>>panel approaches so I'm as comfortable as you can be with that. A
>>couple weeks ago I had my AI go out. WOW, that's another story!! The
>>thing slowly rolled 30 degrees off and REMAINED RESPONSIVE!! When I
>>banked, it banked, when I pitched, it piched. Figuring out that it was
>>dead could be hard and it would be easy to miss it. I decided I need a
>>back up and those vac backup systems are a waste of money(Precise
>>Flight, electric vac, etc). After getting it back from overhaul my
>>partner reported that it did it again! I called a couple gyro places
>>and they said the vac AIs don't last very long because they have a
>>stream of "dirty" air running through them. The electrics last much
>>longer. So I'm getting an electric AI installed as my backup. I
>>noticed that the non-TSO'd electric AIs are almost $1000 less than the
>>TSO'd ones. I asked my mechanics and the FSDO and they said I could
>>probably get a 337 approved by the FSDO for a non-TSO'd unit as long
>>as it wasn't in the "T" area of the panel. One FSDO guy said I might
>>need to label it "VFR only" and I'd have to promise not to do 135. In
>>either case I'll end up having an electric backup AI for under $1500.
>>That's less than the price of a backup electric vac pump installed
>>about about the same price to put a Precise Flight in a Mooney (with
>>California labor rates of $95/hr ) with twice the redundency.
>>
>>-Robert
>
>
>


--
Dave Butler, software engineer 919-392-4367

Dave Butler wrote:
> Robert M. Gary wrote:
>
>> Dave Butler > wrote in message
>> >...
>>
>>> I now have the Aero-Advantage STCed dual-rotor vacuum pump and think
>>> it is overall the best solution. It offers more redundancy and more
>>> reliable backup for a reasonable price. http://www.aeroadvantage.com
>>>
>>> Including installation it will be less than your electric AI, and a
>>> better solution, IMO.
>>
>>
>>
>> I'm not so worried about losing the vac. What I'm worried about is
>> lossing the AI.
>>
>> BTW: What is the purpose of the dual rotor pump. When my pumps have
>> gone out its always been because a vain got stuck and sheared off the
>> pump shaft. My mechanic said that's how they usually fail. Wouldn't
>> that kill both rotors?
>> -Robert
>
>
> I understand your skepticism, but AeroAdvantage claims that they have a
> mechanical arrangement that allows each rotor to fail independently.
> Check the web site for more details, but if my memory serves it amounts
> to providing weak points (necking) in the shaft in such a way that the
> shaft for each rotor can fail independently. I have had trouble
> visualizing what the mechanical arrangement is and would like to take
> one apart or see an exploded drawing to see how they do that. I can't
> explain exactly how it's done, but they convinced me to my satisfaction
> that they had solved the problem.

Following up my own posting: here's what it says in the FAQ at
http://www.aeroadvantage.com (to visualize, the pump is mounted so that the
drive shaft is pointing forward):

1.) How can the rear pumps chamber continue to operate after the forward pump
chamber has failed?

The Dual Rotor Vacuum Pump incorporates a shear coupling between the forward
rotor and the driveshaft. The forward rotor’s shear coupling can shear away from
the driveshaft without causing the driveshaft to fail. Similarly, the rear rotor
also incorporates a shear coupling. As an Additional safeguard, the shaft has a
necked down area between the two rotors. Either the rear rotor’s shear coupling
or the necked area in the driveshaft can shear away from the forward rotor
without effecting the forward rotors continued operation.

and also:

6.) When a vacuum pump fails it can contaminate the vacuum system how do you
prevent one vacuum pump chamber from contaminating the other in the event of a
failure?

The Dual Rotor Vacuum Pump incorporates an intake manifold with dual check
valves. When a rotor disconnects from the driveshaft the check valve for that
chamber closes, preventing contamination of the other pump that is still
operating. Also, since the pump's chambers share a common exhaust, the exhaust
from the operating pump helps contain the contamination to the failed chamber by
applying positive pressure to the failed chamber.

Dave
Remove SHIRT to reply directly.

Dave Butler wrote:
> Martin Kosina wrote:
>
>>> Robert M. Gary wrote:
>>>
>>>> After having both a vac pump failure and an AI failure (not on the
>>>> same flight :) ) I decided its really time for a backup.
>>>
>>>
>>
>> I had a similar revelation recently, after a challenging IPC at night
>> and a quiet reflection on a AI that did fail one me, albeit on a nice
>> day. Did lot of soul searching and decided to postpone a GPS upgrade
>> in favor of some attitude information backup first.
>>
>> Dave Butler > wrote:
>>
>>
>>> FWIW, I have an electric AI in my Mooney and I wouldn't do it again.
>>> It's expensive, failure prone, and too far out of my scan to be
>>> useful as a backup.
>>
>>
>>
>> Did you have a lot of problems with the electric AI ? I am also
>> considering one (the dual pumps sound promising, but still don't back
>> up the gyro...), so I am curious how they hold up (the RCA-26 series
>> or the non-TSO'd Falcon, the AIM / Midcontinet stuff is just too
>> expensive). I heard mixed reviews on the RC Allen, some people have
>> had them for years without any problems and some claim they they don't
>> hold up as well as quality vacuum gyros.
>
>
> The electric gyro in my Mooney was installed before I bought into the
> partnership, so I don't know all the details, but I think it's been in
> there about 10 years or so, and has been overhauled twice. Each overhaul
> cost about the same as the original purchase price.
>
> Sorry, I don't know which brand it is. If I can find out, I'll post it.

Followup after talking to one of my partners: We're pretty sure it's an RC
Allen. It's been in a little longer than I thought, more like 12 years instead
of 10. It's been repaired twice in the 12 years. The first time was relatively
reasonable and cost a few hundred dollars. The second time was over a thousand
and was called an 'overhaul'. The overhaul was done by Kelly Instruments. My
partner's feeling is that the reliability and repair cost was no different from
any typical gyro. The net is that maybe it's not as bad as I thought.

>
> The installation in my airplane is over on the copilot's side, so it's
> way out of my scan and therefore pretty much worthless. I'd go partial
> panel with the turn coordinator and mag compass before I'd try to use a
> gauge so far out of my scan. If you install an electric, be sure to put
> it where you can see it.
>
> Dave
> Remove SHIRT to reply directly.
>
>>
>> Re Falcon, I strongly considered the possibility (337 or not), but
>> with a custom tilt they are over $1100 (Chief), not *that* cheap
>> considering a brand new RCA goes for $1650 at the discounters (like
>> Spruce), factory tilt included and less paperwork hassle. Still, $500
>> is money, so if they are OK, might be worth considering. There seems
>> to be very little info on them besides the manufacturer,
>> unfortunately....
>>
>> Thanks,
>>
>> Martin
>
>
>


--
Dave Butler, software engineer 919-392-4367

In article >,
(Robert M. Gary) wrote:
> Because, a real world situation is that the AI dies very, very slowly.
> There isn't that immediate "hmm, somethings wrong" like with a dead
> vac (alarms going off etc). The TC has enough bounce in it that there
> is really no way to detect small differences like 5 degrees when you
> are in real IMC. Once you start bouncing around in the clouds the TC
> starts bouncing back and forth. It will keep you upright but is far
> from close enough to determine 5 or perhaps even 10 degrees off. The
> DG you may or may not notice. In anycase two AIs being off is a pretty
> quick and certain thing to notice.
>
> Couple that with the fact that you have to decide which is right, the
> TC or the AI. If you have 3 its easier to pick on that might be bad.


Let's see, I have 4 instruments in a basic IFR panel that can indicate
the position of the wings. AI, DG, TC, and wet compass. If my AI
starts to roll over 5 or 10 degrees and I level it, that's not going to
put me in a death spiral, but I should notice heading changes regardless
of what the TC is doing. If the ride is so rough that you can't obtain
meaningful data from any of the other instruments, then you're not the
guy I'd send to buy my lottery ticket.

Bottom line is that a scan should include all instruments. The more
data you incorporate into your scan, the more data you'll have to work
with if something looks amiss. The TC isn't the only practical backup
for the AI and, in fact, provides no pitch information anyway; for that,
you'll have to include airspeed and altimeter.

If I had to pick between having the TC, DG, altimeter, and airspeed as
my AI backup, or picking a second AI, I'd take the data from 4
instruments rather than one.

Maybe it's just me. Wouldn't be the first time.



JKG

In article >,
(Teacherjh) wrote:
> You don't know which to trust, and you are out of bullets. You have to figure
> out which one is lying. Besides, you can bank while remaning straight, and
> you can be level while turning.
>
> With two AIs, you can go PP and use the TC and DG (and ball).


If I have two AIs and they begin to disagree, what then? How do I
determine which one to believe?

If I incorporate the AI, DG, TC, wet compass, altimeter, and airspeed
into my scan and one instrument begins to disagree with the others, I
know almost instantly which instrument to disregard. Not sure how a
second AI helps substantially more with that, since it seems that I have
quite a few instruments to reference without the second AI. The second
AI would probably help me fly the airplane after I identified a faulty
AI, but wouldn't contribute substantially more to recognition because
I'd still have to use the other instruments in the panel to identify
which of the two AIs is accurate.

And, I flew partial panel in actual IMC just fine with *NO* AI many
times during my instrument training. The AI was covered and I knew that
I "lost" it, but I certainly didn't need a second AI to fly partial
panel, even on approaches.

I don't mean to make things sound trivial, because they're not.
Recognition and recovery is definitely not trivial for something like an
AI (I've had an AI die on me). However, thinking that a second AI is
going to bail your butt out of the recognition game is dangerous, IMO.
It all comes down to practice and practice often, which I suspect that
many of us (myself included) don't do enough of.



JKG

Jonathan Goodish > wrote in message >...
> In article >,
> (Robert M. Gary) wrote:

> Let's see, I have 4 instruments in a basic IFR panel that can indicate
> the position of the wings. AI, DG, TC, and wet compass. If my AI
> starts to roll over 5 or 10 degrees and I level it, that's not going to
> put me in a death spiral, but I should notice heading changes regardless
> of what the TC is doing. If the ride is so rough that you can't obtain
> meaningful data from any of the other instruments, then you're not the
> guy I'd send to buy my lottery ticket.

Its very common for me to be in actual conditions that are bouncy
enough that the TC isn't going to do anything other than keep me
upright. I'd be banking back and forth like a mad man as it flopped
around. The compass is pretty useless, it just spins back and forth.
That's the problem with most IFR, its usually very, very bouncy.

> If I had to pick between having the TC, DG, altimeter, and airspeed as
> my AI backup, or picking a second AI, I'd take the data from 4
> instruments rather than one.

But its not one, its two. If you look at the two AIs and they disagree
you will say to yourself "Hmmm, something is wrong". The ability to
say that is HUGE. A real AI failure is so mild that you probably would
never notice. If just using the TC, DG and compass worked, you
wouldn't hear about people dieing after partial panel situations. You
wouldn't see big warnings on vac pumps. The airlines decided to get
extra AIs and dump the TC a while ago.

Dave Butler > wrote in message >...
> Mark Astley wrote:
> > Robert,
> >
> > There was a recent article in Aviation Consumer about this (not sure if you
> > subscribe):
> >
> > http://www.aviationconsumer.com/archives/34_1/safety/5307-1.html
> >
> > Among other things, they discuss: dual chamber vac with a backup gyro and
> > PDA-style all electronic backups. If memory serves, a dual chamber vac with
> > a backup gyro is not terribly expensive and probably wouldn't require fancy
> > paperwork. I think they quote a price in the ballpark of $2000 for that
> > solution. The PDA-style all electronic solution is a bit more pricey and
> > wouldn't be panel mount.
>
> Aviation Consumer's original article on the subject, written by Coy Jacobs, was
> pretty negative on the dual vacuum pump.

It seems that Coy likes the items that he sells in his shop and tends
to not like the items that are not sold in his shop. I've never been
very happy with his objectivity. The whole scandal with the CorrosionX
vs the competitor was a good reason for me to drop the subscriptions.
Clearly he was going after the company that didn't want to let him
resell their goo (in my opinion).

-Robert

> Followup after talking to one of my partners: We're pretty sure it's an RC
> Allen. It's been in a little longer than I thought, more like 12 years instead
> of 10. It's been repaired twice in the 12 years. The first time was relatively
> reasonable and cost a few hundred dollars. The second time was over a thousand
> and was called an 'overhaul'. The overhaul was done by Kelly Instruments. My
> partner's feeling is that the reliability and repair cost was no different from
> any typical gyro. The net is that maybe it's not as bad as I thought.
>
> >
> > The installation in my airplane is over on the copilot's side, so it's
> > way out of my scan and therefore pretty much worthless. I'd go partial
> > panel with the turn coordinator and mag compass before I'd try to use a
> > gauge so far out of my scan. If you install an electric, be sure to put
> > it where you can see it.

Dave, thanks for the feedback ! Sounds like RCA, Kelly Inst. is the
manufacturer of that brand.

I bit the bullet and got one, will put it just right of the center
stack for now, but I could also go into what is now the #2 CDI spot
and move that to the right. That would look a bit funny, but may make
for a much better cross-check. In any case, I'll definitely practice
with it before considering it a solid backup.

Martin

I'm surprised no one has mentioned wet vacuum pumps. I'm considering a
wet pump when the current dry pump gives up the ghost, as it sounds like
wet pumps are nearly bullet-proof. That said, I have been lucky in that I
still have not had a vacuum pump go out on me. I have had several gyros
fail though.

>

--
--Ray Andraka, P.E.
President, the Andraka Consulting Group, Inc.
401/884-7930 Fax 401/884-7950
email
http://www.andraka.com

"They that give up essential liberty to obtain a little
temporary safety deserve neither liberty nor safety."
-Benjamin Franklin, 1759

If you already have a few oil leaks, then the wet pump won't annoy you.
Those oil/air separators in the discharge are not perfect.
---JRC---

"Ray Andraka" > wrote in message =
...
> I'm surprised no one has mentioned wet vacuum pumps. I'm considering =
a
> wet pump when the current dry pump gives up the ghost, as it sounds =
like
> wet pumps are nearly bullet-proof. That said, I have been lucky in =
that I
> still have not had a vacuum pump go out on me. I have had several =
gyros
> fail though.
>=20

Ray Andraka opined

>I'm surprised no one has mentioned wet vacuum pumps. I'm considering a
>wet pump when the current dry pump gives up the ghost, as it sounds like
>wet pumps are nearly bullet-proof. That said, I have been lucky in that I
>still have not had a vacuum pump go out on me. I have had several gyros
>fail though.

At one point I thought about replacing the dry pumps on a Twin Comanche with
wet ones. Seems that you need to go through a bunch of STC or 337 field
approval paper work to do the swap. So I dropped the idea.



-ash
Cthulhu for President!
Why vote for a lesser evil?

"Ash Wyllie" > wrote in message =
...
> Ray Andraka opined
>=20
> >I'm surprised no one has mentioned wet vacuum pumps. I'm considering =
a
> >wet pump when the current dry pump gives up the ghost, as it sounds =
like
> >wet pumps are nearly bullet-proof. That said, I have been lucky in =
that I
> >still have not had a vacuum pump go out on me. I have had several =
gyros
> >fail though.
>=20
> At one point I thought about replacing the dry pumps on a Twin =
Comanche with
> wet ones. Seems that you need to go through a bunch of STC or 337 =
field
> approval paper work to do the swap. So I dropped the idea.
>=20
>=20
I don't know about Lycoming engines, but Continentals still have the oil =
galleries
under the mounting pads for the vacuum pumps.
I know because I recently had to replace a leaking seal on one of my dry =
pumps.
Probably a simple 337 would suffice for Continentals.
You'd just be changing back to the configuration they were originally =
designed for.
---JRC---

Mine (a '65 model) originally had a wet pump, and I believe it is what is listed
on the TC.


> At one point I thought about replacing the dry pumps on a Twin Comanche with
> wet ones. Seems that you need to go through a bunch of STC or 337 field
> approval paper work to do the swap. So I dropped the idea.
>
> -ash
> Cthulhu for President!
> Why vote for a lesser evil?

--
--Ray Andraka, P.E.
President, the Andraka Consulting Group, Inc.
401/884-7930 Fax 401/884-7950
email
http://www.andraka.com

"They that give up essential liberty to obtain a little
temporary safety deserve neither liberty nor safety."
-Benjamin Franklin, 1759