Aritficial Horizon Woes

[MBDiagMan]

My vacuum pump went out and was replaced a couple of weeks ago. It now does not develop over about an inch and a half of vacuum at idle, but comes up to five or so with just a little RPM rise.

This morning my aritificial horizon tumbled and I had to ignore it. Once I shut down the plane, moved it by hand into the hangar and did several other things it was still spinning like crazy.

Is it out, or does the varying vacuum have something to do with this?

I don't remember having low vacuum at idle with the old pump before it quit and gave me no vac at any engine speed.

Any thoughts or experience sharing?

Thanks for your help.
Doc

 

[denverpilot]

Kinda sounds like maybe there's a leak?

 

[Fearless Tower]

You have a vacuum pump in a 140???

 

[Tom-D]

Low Vac pressure will cause the AI to tumble,, get the system fixed.. vac regulator may be stuck open.. or some type of leak. hose off or ?

 

[Skylane81E]

Hmm, The low vac at idle isn't terribly uncommon but if it's new maybe something is going on there.

I'd need the plane and my test set to really to figgure it out.

 

[taters]

Low Vac pressure will cause the AI to tumble,, get the system fixed.. vac regulator may be stuck open.. or some type of leak. hose off or ?

+1 I would take a look at your vac regulator

 

[MBDiagMan]

You have a vacuum pump in a 140???

Yes, it has a vacuum pump on an O200A, and a custom IFR panel with six pack and center stack. A previous owner got their IR in it.

Thanks for all the feedback. My IA replaced the vac pump and then went out of town. I will ask him to look further when he gets back. I will go to the airport tomorrow and check the lines to see if anything is loose.

 

[Fearless Tower]

Yes, it has a vacuum pump on an O200A, and a custom IFR panel with six pack and center stack. A previous owner got their IR in it.

Thanks for all the feedback. My IA replaced the vac pump and then went out of town. I will ask him to look further when he gets back. I will go to the airport tomorrow and check the lines to see if anything is loose.

Dang...that's a pretty nice panel!

I'm not super familiar with 140s....is the O200A stock?

I'm suprised it can take a vacuum pump when the C-145/O-300 in the 170s won't.

 

[MBDiagMan]

Fearless,

The C140 came with an 85HP, the O200A is 100HP. I need every bit of it to make up for the added weight, that panel being a lot of it.

The O200A is a Continental and one of these reasons this is a popular STC is because it has a means of adding the vac pump. Otherwise the engine shares similarities with the C85 and C90, the same engine family.

Maybe this is why they use an A model O200 is for the vac pump mount pad. It also has an oil filter.

Again, thanks to all for the feedback. I'm relieved that the problem is probably not the attitude indicator itself.

Doc

 

[denverpilot]

Again, thanks to all for the feedback. I'm relieved that the problem is probably not the attitude indicator itself.

I hate to point out that we didn't really rule it out. We just all thought the low vacuum would be the first thing to look at.

On the good news front, refurbished AIs are ridiculously cheap these days with all the kids going to glass.

Most avionics shops have piles of them sitting on a shelf in serviceable condition. You may not get a warranty, and you may not want to fly a ton of IMC behind it until you're sure it's behaving correctly, but even a new one can fail...

I think parts-cost-wise, we paid very little to swap ours when it died. Labor... that's a different story.

 

[MBDiagMan]

Well I have flown it several hours with no more AI trouble.

The disappointing thing was that when I asked my AI, who replaced the vacuum pump, about the low idle vac, he said "well the pump is turning slower." The problem is that I never noticed this behavior before the old pump failed.

His explanation doesn't give me a good feeling about him. Maybe I'm jumping to conclusions.

Doc

 

[WarriorPilot]

The rotor in the Attitude Gyro is dead or about to pass away, that is why it is spinning. Just pull the attitude gyro and ship it to a shop.

 

[brien23]

If a small piece of rubber from a old vacuume hose gets sucked into the pump the carbon vanes will be destroyed. When you change out the pump might look at the hoses under the panel if they are realy old you might want to change them out too as they are cheaper than another pump.