View Full Version : Install electric Gyros & remove Vacumn pump

tripacer Dan
03-11-2009, 10:39 AM
I was told that a vacumn pump uses over 10 HP at 2400 RPMs.

Has anyone installed electric attitude and directional gyros so they can Remove the wieght and HP drain of a vacumn pump?

Would this be a Major modification?

Any pluses or negatives besides:
- The replacement gyros cost about $4K
+ More HP = go faster
+ Less plumbing under the cowl

Thanks, Dan

03-11-2009, 10:44 AM
I can't see how that little shaft that drives the pump and is made to break would even hold 1 HP???

03-11-2009, 12:01 PM
Dan, I would be very surprised to have that 10 hp requirement claim confirmed. I installed a engine driven vacuum pump on my Colt when I restored it, to eliminate the two and a half venturiis that were on there (two nine inch and one two inch). Take into account that the accessory cover that came on my engine DID NOT have the pad machined for the pump (some did, some didn't), but I HAD ONE that was in my "pile". Finding and buying one of those could be a "$how-$topper" (but then, it sounds like you have the pump already...?). I saw NO difference in apparent performance with or without the engine driven vacuum pump. If I HAD TO evaluate it, I would say the decrease in drag removing the venturiis was perfectly offset by the decrease in power output from installing the pump drive (if that is even "true"). I'd call it a "wash" in that respect. I had an electric attitude gyro in a 22/20 that would have been "unnecessary" if someone had correctly diagnosed a "worn out vacuum DG" that "used all the vacuum". It was done as a Minor (logbook entry). But it seems we are STILL suffering somewhat from separate "localized FAAs" and vriable interpretations, so you need to get with your IA and/or FSDO and request some "guidance" (it helps if you have a decent "verbal argument" in favor of your belief that it would be a "Minor"). I wouldn't make the assumption "on my own" if I were doing it "here". I'd call my PMI and hash it out, first.

WHOOPS! You're Canadien!!! If you are "OM", I don't have a CLUE what TC says about you altering your aircraft... Sorry.

I think this is a case of "whatever blows yer skirt up" as far as tried and true "reasons" for doing it, one way or the other. Most times, what you WANT is usually the deciding factor.

03-11-2009, 01:07 PM
I also seriously doubt that that little pump uses over 1/4 hp max. Think of what a ten horsepower air compressor looks like, it's size and weight and how much heat is generated while consuming ten horsepower. Electric gyros are more expensive but may be a little more dependable than a vacuum pump. The negative is that you have all of your gyro instruments hanging on the electrical system. I prefer having both an electric T&B and vacuum gyros. That way you have to loose both to be in the grey stuff without a paddle. WAyne

Geoff Newcombe
03-11-2009, 03:11 PM
10 horsepower to drive a vacuum pump!? I really don't think so either. Maybe whoever said that was thinking about the AC compressor on a car. To further JW's expression, "whatever blows up your skirt" --- what is being blown up your skirt is smoke! You'd be wasting your time and money.

tripacer Dan
03-11-2009, 10:50 PM
Thanks for sharing your experiences and knowledge.
Should have said; I have a venturi powering my T&B. The DG, Attitude, and Suction gauge are powered by an existing vacumn pump. Good setup (I think).

Seems the electric gyros benfits are not what I thought.
Being new to airplanes and flying there is so much cool stuff to learn.

I am lucky to live in a time that this foums exists.
This forum is saving my mechanic excitement and gray hairs as well ;)

20 more days I will be home from Iraq on vacation and able to be with my airplane. Instead of dreaming about this stuff actually doing it. WEEEEE!

Thanks again, Respectfully, Dan