venturi tube location

[Gary Wallace]

i am looking for some input on venturi tube placement for vacuum gauges...any input would be appreciated. thanks

[whee]

Side of the boot cowl is where they are frequently installed on legacy airplanes. That's when the one on my Luscombe was installed. I was going install one on the belly just aft of the tunnel. IDK if that's a good spot or not though.

[Battson]

With greatest respect, in the year 2018 what is the attraction of a vacuum system over modern electronics in a brand new aircraft?
Vintage aircraft and vintage pilots need not answer that question, the answer needs no explanation in that case.

[whee]

Hi Hotrod180, when did you joint the forum😉😆

I'm not so confident in our EFIS systems that I'd trust my life to them. I'm getting close and may be there after I get some time behind mine but I'm not there yet. If you looked at the vans forum you'd see fairly regular posts about people having issues with their efis systems that could be deadly if it happened in IMC. We know we aren't seeing all the failures even though we know they are still rare occurrences. Instrument flying is the only reason I'd consider installing a vacuum gyro.

[Chris In Milwaukee]

Hi Hotrod180, when did you joint the forum😉😆

Ha! That’s funny right there!

[Battson]

Hi Hotrod180, when did you joint the forum😉😆

I'm not so confident in our EFIS systems that I'd trust my life to them. I'm getting close and may be there after I get some time behind mine but I'm not there yet. If you looked at the vans forum you'd see fairly regular posts about people having issues with their efis systems that could be deadly if it happened in IMC. We know we aren't seeing all the failures even though we know they are still rare occurrences. Instrument flying is the only reason I'd consider installing a vacuum gyro.

Fair shot

All I would say in defence of my question is this:

- I have seen no data to suggest that old-school mechanical vacuum systems are more reliable than proven* electronics. *Forget the bleeding edge stuff.
- If you have dual systems installed for IFR flight into IMC, reliability is basically a maintenance concern only. See below.
- Vacuum systems are definitely maintenance hogs, where electronics have zero maintenance. They either work or they don't.
- Anecdotally the electronics have a range of obvious advantages. Weight, size, non-mechanical, simplicity, etc etc etc

I get that they are loved by those who grew up flying a six pack, such as your old man, Jon. No argument there.

[whee]

Sorry Battson, I just couldn't resist.

[JimParker256]

I fly a "legacy" Champion 7ECA with dual venturis (!) as the vacuum source driving an Attitude Indicator and a DG. Until you get to about 60-65 mph, the gyros are barely spinning at all. They don't really get enough vacuum to run correctly until you're at cruise airspeed. Maybe these guys are just old and tired (perhaps needing a rebuild), but I would hate to rely on either of them to fly an instrument approach. And unless you have an RMI-type DG, precession will always be an issue for vacuum-powered DGs, whereas it simply doesn't exist in the electronic world (assuming you have the magnetometer, of course).

When flying instrument approaches, I prefer to be stabilized at something approaching 1.3 Vso at or before the FAF, so as to minimize the aircraft reconfiguration that has to happen when you break out at 300' AGL... That would mean flying 15-20 mph below the point where sufficient vacuum is being generated to keep the instruments aligned. Like Batson, I place a lot more trust in the electrons driving the EFIS-type systems (or even the "instruments" supplied by the ForeFlight/Stratus2 combination) than I do the venturi-powered AI/DG in the Citabria.

[Bdflies]

Through the years, I've seen vacuum gyro's fail. Electric gyro's fail. I think I've had 2 vacuum pumps fail. Probably the most ironic failure I've ever seen, was a sheared coupling of an electric driven standby vacuum pump. The standby unit was probably not run in a long time. When it was checked, the pump had seized and the coupling sheared cleanly. I've had rough engines and landing gear fail to extend. Thinking through those issues, I'd say the least reliable system has been air driven gyros.

Just a rambling observation. I'm with Battson.

Bill

[Gary Wallace]

It sounds like electronics is the modern day favor. I may have to let my son know he can't go to law school! Will have to see.

[jaredyates]

The expensive choice is flying in conditions where you want the gyros. Fly day vmc and send him to school, and everybody wins!

[whee]

I can't counter their arguments with any authority. During the measly 600hrs we put on our Luscombe our T&B of unknown age and origin (the plane sat in a farmers field for 20yrs beginning in 1981 so we know it was at least that old) was trouble free. It was up and running before the wheels left the ground and was accurate till after touchdown. It's not saying much but I did all my PPL hood time with a T&B, airspeed and altimeter. Someone I know accumulated 5 hrs of actual IMC with that setup. Venturis don't fail and T&Bs are stupid simple unlike artificial horizons. If I don't have the $$$ for a GRT Mini-AP when the time comes that I want to fly IMC then I'll install a $500 vacuum T&B.