Unnerving incident today…

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Expand view Topic review: Unnerving incident today…

Re: Unnerving incident today…

by Rich » Sun May 24, 2020 1:11 pm

Boatguy wrote: Sun May 24, 2020 4:23 am
Rich wrote: Sun May 24, 2020 1:32 am
blsewardjr wrote: Sun May 24, 2020 1:27 am For the backup instruments
I figured, but - really? You're more likely to have to replace a vacuum pump for your backup instruments than to actually need the backup instruments. Everyone else backs up glass with electrical backup instruments, often with battery backup for the backup instruments.
I flew lots of C172S in my primary which had G1000 and vacuum driven backup AI.

Yeah, kinda crazy. When you say "everyone else", you're maybe referring to Cirrus? Not Textron or Piper.
Cirrus and Diamond of course. I haven't dug into everyone's offerings but a couple of checks of current panels from others support my view that this approach is rare these days. I'm thinking even new 172's have now lost this system.

When you say instruments (plural) that's not quite right. It's only the backup AI (singular) that uses it. So to power that 1 instrument you put in the entire known-to-be unreliable additional system, including the gauge to monitor it?

Re: Unnerving incident today…

by Boatguy » Sun May 24, 2020 4:23 am

Rich wrote: Sun May 24, 2020 1:32 am
blsewardjr wrote: Sun May 24, 2020 1:27 am For the backup instruments
I figured, but - really? You're more likely to have to replace a vacuum pump for your backup instruments than to actually need the backup instruments. Everyone else backs up glass with electrical backup instruments, often with battery backup for the backup instruments.
I flew lots of C172S in my primary which had G1000 and vacuum driven backup AI.

Yeah, kinda crazy. When you say "everyone else", you're maybe referring to Cirrus? Not Textron or Piper.

Re: Unnerving incident today…

by Rich » Sun May 24, 2020 1:32 am

blsewardjr wrote: Sun May 24, 2020 1:27 am For the backup instruments
I figured, but - really? You're more likely to have to replace a vacuum pump for your backup instruments than to actually need the backup instruments. Everyone else backs up glass with electrical backup instruments, often with battery backup for the backup instruments.

Re: Unnerving incident today…

by blsewardjr » Sun May 24, 2020 1:27 am

For the backup instruments

Re: Unnerving incident today…

by Rich » Sun May 24, 2020 1:08 am

Just an interesting tidbit: I've flown somewhat later model 172's but not any G1000 variant. Did I understand correctly that there is still a vacuum system in these?

Re: Unnerving incident today…

by Rich » Mon May 18, 2020 11:06 pm

Once upon a time (1970's) I gave a lot of flight instruction, often in customers' airplanes. So I would jump from type to type, often in a single day. I always had to familiarize myself with the specific airplane, not just the type. Big differences abounded even then.

Fuel systems were the biggest difference, with details of LG retraction systems probably a very close second. There were also routinely differences in panel layouts, and avionics. Even the steam gauges had all sorts of nuances you'd better understand. (Ever flown with a vacuum system driven, not by a vacuum pump, but a Venturi tube?) It was also useful to know (TADA!) how the trim worked. Many have a tab on the elevator (possibly anti-servo) but others worked by changing the horizontal stabilizer incidence angle.

This hasn't really changed. One could argue it's potentially worse, since those old birds are still flying today. But, additionally, now you may or may not have glass panels. And each such model operates differently. A given plane might have all the integrated goodies (ADS-B In/out, XM, TCAS, etc.), and another one of the same type on the same flight line has some or none of the extras.

Re: Unnerving incident today…

by Soareyes » Mon May 18, 2020 2:01 pm

Not applicable to the 172 but in a Diamond the control stick can be jammed by a phone sized object slipping into the space between the stick and the seat.

Re: Unnerving incident today…

by CBeak » Mon May 18, 2020 1:11 pm

I just noticed last week that the trim wheel was “jammed” by a headset cord. It was as simple as moving it out of the way, but a wee bit unnerving. The headsets plug in so close to the trim wheel, and then come forward for the wearer. The cord was just loosely lying right in front of the trim wheel, and when I tried to apply down trim, it caught one of the little protruding knobs on the outer edge of the wheel.
It was not a big deal, but afterward I was thinking that might be a design flaw that nobody saw coming.
Of course, I just now realized you were in a 172 and that’s a different setup.

Re: Unnerving incident today…

by elmanzah » Sun May 17, 2020 6:37 pm

Thank you all for the responses.

Andrew: No.. the slight movement in the trim wheel didn’t result in any relief of the controls. Something was jammed with the trim wheel. I agree something was wrong but as of now I don’t know what it is. I am definitely interested in finding out what it is.

Peter: I love the idea of keeping a log. Going to do the same. I use ForeFlight (don’t we all?) and will see if there is a way I can employ tags to filter on those flights with good lessons learned. The checklist I used was the one the school created. Perhaps my takeaway there is to seek out the manufacturer’s check list and see what is omitted or added by the school. Overkill? I don’t know.

Russ: This was a kap140 plane. yes agreeing with what you said.

Re: Unnerving incident today…

by Boatguy » Sun May 17, 2020 5:33 pm

First, I agree with Peter that it's great to air out these incidents. I think you handled the problem correctly, transferred controls and landed immediately. The value of this community is through the sharing and comments. Now, could it have been avoided?

I trained on several C172Ss with G1000 and GFC700 autopilot. You didn't mention if this plane had a GFC700 or KAP140 autopilot. If it did, then read on, if not, then these comments are irrelevant to your situation.

One of the things on my C172 (and DA40) checklist is to verify the electric trim controls since those are used by the AP. I use the trim control switches on the yoke/stick to move the trim forward, then aft, usually coming to rest on the TO setting. Then I individually operate the switches which should NOT move the trim. This is to ensure that the switches are both operating correctly (i.e., both are required to move the trim) to prevent runaway trim.

Had you done a verification of the electric trim controls, it might have revealed the problem you experienced. I say might because I we don't know where the actual problem was in your trim controls.

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