AUTOPILOT PROS & CONS

"Peter" wrote:

CON: Autopilots can fail. If you exclusively rely on the autopilot to fly
the plane, you quickly become the passenger, not the pilot. You need to
stay attentive and proficient enough that if the autopilot fails, you don't
kill yourself.

How true. My KFC225 has failed about a dozen times in 4 years, most of
them without any indication.

My buddy has a KFC225 with a similarly dismal history. The avionics shop
tells him this is not unusual for that model. Not usual!!!

My S-Tec 50, a 2-axis, rate-based unit, has operated with only one glitch-- a
bad switch--in 700+ hours since installation. It's a much simpler piece of
gear, not as precise or as smooth in turbulence as the KFC225, but I'll take
reliability over capability every time.

--
Dan
C-172RG at BFM

My S-Tec 50, a 2-axis, rate-based unit, has operated with only one glitch-- a
bad switch--in 700+ hours since installation.

A friend of mine has a 50 in his Bo, and it hasn't fared as well as
yours. If went 'dead' - meaning no action on aileron control and no
annunciation - multiple times before the problem was resolved. Usually
by the time he got it to the A/P shop it was working again, and the
shop could not figure out what was wrong. Eventually it died for good.
It was a bad motor in the roll servo.

On the flip side, I once instructed a student in an Ovation who told me
his KFC-225 never hiccupped.

Michael

"Michael" wrote in message
ups.com...
My S-Tec 50, a 2-axis, rate-based unit, has operated with only one
glitch-- a
bad switch--in 700+ hours since installation.

A friend of mine has a 50 in his Bo, and it hasn't fared as well as
yours. If went 'dead' - meaning no action on aileron control and no
annunciation - multiple times before the problem was resolved. Usually
by the time he got it to the A/P shop it was working again, and the
shop could not figure out what was wrong. Eventually it died for good.
It was a bad motor in the roll servo.

On the flip side, I once instructed a student in an Ovation who told me
his KFC-225 never hiccupped.

Michael

Some autopilot failures are very subtle. I was shooting a coupled ILS to
minimums with a King autopilot in a Mooney. After capturing the glideslope,
I noticed the rate was about 75'/min more than I was used to. As we got
closer to DH, the DME was still showing about 2 miles to the airport. I
leveled at DH, and while motoring along 200' above the houses, I tapped the
Vor/loc. The GS needle snapped to the top of the case. It was "stuck"
centered, and the autopilot
was literally flying the needle. Iron Mike, indeed.

Al

"Al" wrote in
:

Some autopilot failures are very subtle. I was shooting a coupled ILS
to minimums with a King autopilot in a Mooney. After capturing the
glideslope, I noticed the rate was about 75'/min more than I was used
to. As we got closer to DH, the DME was still showing about 2 miles to
the airport. I leveled at DH, and while motoring along 200' above the
houses, I tapped the Vor/loc. The GS needle snapped to the top of the
case. It was "stuck" centered, and the autopilot
was literally flying the needle. Iron Mike, indeed.

Technically speaking, that wasn't an autopilot failure, it was a GS needle
failure. The results would have been nearly identical if you were hand-
flying. Although you might have noticed inconcistencies in airplane
response more quickly and fixed it earlier. Then again, you might have been
so busy keeping the needle centered that it would have gone unnoticed until
you flew your plane right through someone's living room.

Hard to say.

"Judah" wrote in message
. ..
"Al" wrote in
:

Some autopilot failures are very subtle. I was shooting a coupled ILS
to minimums with a King autopilot in a Mooney. After capturing the
glideslope, I noticed the rate was about 75'/min more than I was used
to. As we got closer to DH, the DME was still showing about 2 miles to
the airport. I leveled at DH, and while motoring along 200' above the
houses, I tapped the Vor/loc. The GS needle snapped to the top of the
case. It was "stuck" centered, and the autopilot
was literally flying the needle. Iron Mike, indeed.

Technically speaking, that wasn't an autopilot failure, it was a GS needle
failure.

Correct.

The results would have been nearly identical if you were hand-
flying. Although you might have noticed inconcistencies in airplane
response more quickly and fixed it earlier.

Naw, If I'd set the plane up for the descent, and got it exactly right the
first time, with no additional trim, I'd be real suspicious...Never happened
before.

Then again, you might have been
so busy keeping the needle centered that it would have gone unnoticed
until
you flew your plane right through someone's living room.

Hard to say.

It's really a matter of cross checking and a cynical attitude.

Al

On the Century-2000 equipped Bonanzas I fly, there's an interesting
trim problem with the AP, which is basicly that it doesn't trim.

Engage the AP while you're being vectored for the ILS and let it
fly the approach, as you keep reducing power to slow down and then
track the GS. As you slow down, you should be dialing in nose-up trim
(and, indeed, the AP prompts you to do this, but if you're not paying
attention, you can miss the flashing light).

Now, at DH, click off the AP to hand-fly the landing. All of a
sudden, you've got a fistfull of yoke trying to pull your arms out of
their sockets until you get the trim fixed. Even worse if you didn't
see the runway and clicked off the AP to execute the missed.

Of course, the AP is performing as designed, and it's the pilot who's
unairworthy, but it's a common enough mistake that I've got to believe
it's a design flaw in the system. If nothing else, it should have a
more obvious alert than a small blinking light outside of your main
visual scan. Like maybe a mechanical arm that smacks you upside your
head with a rolled-up sectional while a synthesized voice says, "Trim
up, trim up".