It actually happened today!! Vacuum failure in IMC.

Victor J. Osborne, Jr. wrote:


That's why I'm looking at the Mid-Continent Sporty's electric AI
replacement T/C.

And what will you do if that AI tumbles for some reason in IMC? That's been
my big concern about replacing the TC with an AI, and the relevent AC
doesn't even refer to that particular vulnerability.

Are there tumble-free AIs?

BTW, the Sporty's unit is not the Mid-continental; it's a Castle-something
(IIRC). The Mid-continental is more expensive than the Sporty's.

[...]
Keep in mind that even George w/ bail on you if the vacuum/pressure goes.
(S-Tec aside)

If George is, like most (all?) S-Tec units, rate-based then it'll survive a
vacuum failure in NAV mode. HDG mode, of course, will be unavailable
(unless you want to circle with the DG {8^).

Or is my understanding incorrect?

- Andrew

I know the Mid-Co. is more money. I left out and simple OR. But that's
also why I'd like to get pireps on the two systems.

Are there tumble-free AIs?

The Sporty's does have a cage button but I think having one could prevent a
tumble in the 1st place. BTW: My avionics shop says they add a toggle
switch for the unit so you don't have to use it all the time in VMC. Also,
they say the Mid-Cont. unit there most popular upgrade.

If George is, like most (all?) S-Tec units, rate-based then it'll survive
a
vacuum failure in NAV mode. HDG mode, of course, will be unavailable
(unless you want to circle with the DG {8^).

Yes, S-Tec's w/ function w/o vacuum/pressure. Big plus. My Bo' came w/ a
KFC-200, so I'm stuck w/ it until it dies (hopefully w/ ample warning)

Thx, {|;-)

Victor J. (Jim) Osborne, Jr.

"Andrew Gideon" wrote in message
online.com...
Victor J. Osborne, Jr. wrote:


That's why I'm looking at the Mid-Continent Sporty's electric AI
replacement T/C.

And what will you do if that AI tumbles for some reason in IMC? That's
been
my big concern about replacing the TC with an AI, and the relevent AC
doesn't even refer to that particular vulnerability.

Are there tumble-free AIs?

BTW, the Sporty's unit is not the Mid-continental; it's a Castle-something
(IIRC). The Mid-continental is more expensive than the Sporty's.

[...]
Keep in mind that even George w/ bail on you if the vacuum/pressure goes.
(S-Tec aside)

If George is, like most (all?) S-Tec units, rate-based then it'll survive
a
vacuum failure in NAV mode. HDG mode, of course, will be unavailable
(unless you want to circle with the DG {8^).

Or is my understanding incorrect?

- Andrew

Skym,

Well done!

Now, for the paperwork.


What paperwork??? Don't tell me you still believe in that myth about
paperwork having to be filled out after declaring an emergency. I
wondered about your phrase "bit the bullett", too. There's nothing to
bite. Just declare away!

--
Thomas Borchert (EDDH)

... most of the GPS approaches at CAE want a
WAAS capable GPS, which my G430 isn't.

All four of the RNAV (GPS) approaches at CAE are flyable without WAAS. Having
WAAS would provide an electronic glideslope and allow you to use the lower
LNAV/VNAV or LPV minimums (which are all higher than the ILS minimums).
However, your choices to divert to someplace closer, and then land visually
when you had the chance, definitely seem to me like the right way to go in
this situation.

Barry

skym wrote:
Departed Asheville NC today into IMC enroute to Columbia SC. Well into
IMC and about 6500 MSL the DG started to slowly just start rotating and
the AI started to lean over. Backup vacuum-no help.

As others have already said, I'd appreciate some elaboration on why your backup
vacuum was no help.

I couldn't
believe this was happening in IMC; I only fly it about 5% of the time.
Columbia was just a bit above minimums. I was not prepared to try an
ILS with no operative DG, and most of the GPS approaches at CAE want a
WAAS capable GPS, which my G430 isn't.

Putting aside the anthropomorphism implied by approaches "wanting" a WAAS
capable GPS, I'd like to understand how this figured into your planning. All the
RNAV approaches at CAE have LNAV MDAs, so could be flown with your GPS. Why was
the lack of WAAS a consideration?

Second, I'd like to understand in what way you felt prepared to fly an RNAV
approach without a DG, but not an ILS approach. I'd think the workload is about
the same. Do you think having vertical guidance would be a distraction?

Congratulations are in order for handling your emergency safely and competently!

Dave

Dave Butler wrote:

Second, I'd like to understand in what way you felt prepared to fly an
RNAV approach without a DG, but not an ILS approach. I'd think the
workload is about the same. Do you think having vertical guidance would be
a distraction?


For that matter, the 430/530 has the ability to display track. That's even
better than heading for approach purposes.

[In fact, it's easy to become *too* dependent upon track, desired track, and
x-track error.]

- Andrew

Dave,
I'll use this to answer both you and Barry, since you have both raisede
the WASS question, but you have a second one.

The rnavs 5,11, 23, and 29 at CAE have an entry that is "LNAV/VNAV".
I'm new to the panel GPS, having just gotten it about a month before
this trip so, although I have flown the approaches when familiarizing
myself with it, I had not thoroughly studied the GPS approach plates.
Before I left AVL, I'd looked at the plates and saw those notations,
and didn't look further. They require WAAS. I now (for the first
time) see that there are also simply LNAV approaches. I'm more
familiar with ILS than GPS approaches (obviously), and planned on an
ILS approach anyway, so hadn't really studied the GPS approach plates.
As for flying the GPS rather than the ILS into CLT, I've been so
indoctrinated into flying headings rather than "chasing the needle" on
an ILS that I had to rule that out. Although I was wrong about the
need for WAAS, I believed that I had no choice at that point-I'd do the
best I could with the GPS approach. The ceilings and vis were better
at CLT than at CAE (which was close to minimums) so it was less of a
risk (in my mind) to do the GPS approach at CLT even though I wasn't
(erroneously) properly equipped with WAAS.

As for flying the GPS rather than the ILS into CLT, I've been so
indoctrinated into flying headings rather than "chasing the needle" on
an ILS that I had to rule that out.

I agree with flying a GPS approach instead of an ILS when partial panel - it's
much easier to fly because the needle doesn't get more and more sensitive as
you continue. Another factor to consider is that with only the magnetic
compass it's easier to hold an east or west heading than north or south. So,
for example, at CAE, I'd ask for the GPS 11 or 29 instead of 5 or 23.

Barry

Barry wrote:

As for flying the GPS rather than the ILS into CLT, I've been so
indoctrinated into flying headings rather than "chasing the needle" on
an ILS that I had to rule that out.


I agree with flying a GPS approach instead of an ILS when partial panel - it's
much easier to fly because the needle doesn't get more and more sensitive as
you continue. Another factor to consider is that with only the magnetic
compass it's easier to hold an east or west heading than north or south. So,
for example, at CAE, I'd ask for the GPS 11 or 29 instead of 5 or 23.

I'd fly an ILS over a GPS any day if I was PP. I WOULD use the GPS to
give me a better indication of the heading as opposed to the compass,
but why give up the lower minimums and greater accuracy offered by an
ILS, especially when the chips are already down a little.


Matt

I'd fly an ILS over a GPS any day if I was PP. I WOULD use the GPS to give
me a better indication of the heading as opposed to the compass, but why
give up the lower minimums and greater accuracy offered by an ILS,

Because the GPS approach is easier to fly - less chance of going to full-scale
deflection.