Posted: Sun Aug 14, 2005 2:23 pm
George,
You never give up, do you?
You never give up, do you?
The International Cessna® 170 Association
Formed to preserve and promote a truly classic airplane
https://www.forum.cessna170.org/forums/
C170B Vacuum Pumps
Page 3 of 3
Posted: Sun Aug 14, 2005 11:15 pm
Posted: Mon Sep 19, 2005 4:16 pm
George I have the belt driven pump arrangement, and I would like to install a venturi back up on the airplane. What would be a good venturi model and alternate vacuum valve to use in the plane? It will be driving an AH and DG only. Where could I get a valve for this install?
Scott
Scott
Standby Vacuum System
Posted: Mon Sep 19, 2005 5:43 pm
Hi Scott,
Once you've figured out the venturi part, it's probably worth checking out the Standby Vacuum Systems that used to be sold by Precise Flight ( http://www.preciseflight.com ), and are now available from The Vacuum Source ( http://www.thevacsource.com/svs.php ). You can download the installation manuals from their web site for free and see what you think. The question to ask them is whether the SVS could be plumbed into a venturi system instead of the engine intake manifold; what changes to the paperwork would be required, whether it would need a field approval, etc.
Best Regards,
John
Once you've figured out the venturi part, it's probably worth checking out the Standby Vacuum Systems that used to be sold by Precise Flight ( http://www.preciseflight.com ), and are now available from The Vacuum Source ( http://www.thevacsource.com/svs.php ). You can download the installation manuals from their web site for free and see what you think. The question to ask them is whether the SVS could be plumbed into a venturi system instead of the engine intake manifold; what changes to the paperwork would be required, whether it would need a field approval, etc.
Best Regards,
John
Posted: Tue Sep 20, 2005 2:23 am
Hi, Scott!S&G Lynn wrote:George I have the belt driven pump arrangement, and I would like to install a venturi back up on the airplane. What would be a good venturi model and alternate vacuum valve to use in the plane? It will be driving an AH and DG only. Where could I get a valve for this install?
Scott
Well, it depends upon a couple of factors.
If you want a venturi setup that appears original, then a dual set of 4" venturis PN 15050 ($50 each)from Aircraft Spruce would be the ticket. If, on the other hand, you prefer to install only one, but it must operate more than one gyro, then you should consider their 9" venturi, PN 15052 (also called a super-venturi) priced at $59.
As for installation legalities, that's a horse of a different color. You'll likely need a field approval or one-time STC. If I were to pursue such a mod, I'd consider a 3-way type valve such as an Imperial 108HD-06 such as Aircraft Spruce's PN 210-CN ($23). This is a valve normally used for fuel, but should work just fine on a vacuum system It has Three, 3/8" ports, and will feed vacuum from either side-port to the center port. With the gyros attached to the middle/center port, and the vacuum pump connected to one side, and the venturi(s) connected to the other port, then either pump OR venturi(s) could provide suction.
Get the STC yourself, and you'll likely be able to sell it to others as a simple backup system. Good luck.