Inadequate Vacuum

[GAHorn]

Yeah, you mighta messed up ripping out all that galvanized pipe!
Vacuum T&B's are kinda rare these days, but they are a reliable instrument. There's lots to be said for air-driven over electric gyros as far as reliability goes.
Of course, as you've already alluded to it (but just to reiterate for others) it's a good idea to have a mixed bag of power sources for gyros for redundancy. The most common being air driven horizon and DG, and electric T&B.
About 25 years ago had to descend thru a 4K-foot undercast using a vacuum T&B in my old Aeronca. I'd fallen for a "current" observation that was made by a wx man who apparently never really looked out the window and ended up trapped on top over BHM at sundown in a non-electric airplane. My hand-held got me a descent clearance from approach after making a "turn for identification". You know how long it takes to descend thru 4,000' of cloud on AS/needle/ball? Almost 24 hours! I'd entered it at about 7K and broke out around 3K.
I hope I never have to do it in rough air! (When I landed, I was instructed to call the TRACON facility. I expected to end up filling out all sorts of paperwork and maybe a scolding. Turned out the controller who worked me owned a similar Aeronca and he wanted to talk to me about what it was like. Whew.

[Bruce Fenstermacher]

Geoge your first mistake wasn't lisening to the wx man but flying an Aeronca at 7K ft. Don't Aeroncas have a fun service ceiling of about 2K

[zero.one.victor]

George, seeing as you had confirmation it was clear below,you shoulda "spun her down" thru the layer. Four thousand feet of descent probably equates to about eighty turns, then recover from the spin on the proper heading (reciprocal to the 45 entry), a descending long teardrop turn back onto the 45, then a close-in pattern and a short-field landing on the ramp to top it all off. You even had a handheld so everyone could hear your "hey y'all, watch this!".
That's what a REAL pilot woulda done!

Eric

[GAHorn]

Ha! That's funny, Eric!
I actually did spin that Chief a couple of times, and it scared me. It wouldn't spin at all unless you stalled it pretty nose-high....then at the second turn it'd suddenly wrap up pretty tight and before you knew it you'd be in turn #5 and wondering if it's ever gonna come out! It never recovered in the first turn after recovery was attempted, it always turned at least twice more.
It made more vibration and noises than I'd ever heard any airplane do, and this was a pretty nice example of a 65hp Chief. I quit spinning it after that second time. I just didn't have the cajones to believe it was always going to recover.
I'd read one time that Lindy had recovered from disorientation by spinning down thru an undercast. I tried it once in a C-150 back in the early '70's when Tx still had large areas of uncontrolled airspace down along the coast. I climbed up on top about 5K' and spun it down thru a layer that had a bottom around 3K'. It was a non-event in a 150.
But that Aeronca? No thanks.
I never did find out why that airplane spun so goofy. WD Thompson tells a story of spinning airplanes for the factory. He and another very experienced test pilot got into one airplane they thought they were going to die in. (172? Or a 195. Whatever.) In any case the airplane didn't do like it was supposed to do and numerous attempts failed to recover the airplane. The test was so common, and the results were always so positive and repeatable, that he'd not even put on his parachute...but had it lying on the floor. The centrifugal force prevented him from getting out of his seat to get the chute much less exiting the airplane! After spinning down from over 10K and repeated attempts had failed to recover the airplane it appeared they were going to die...when suddenly and without any identifiable reason the airplane quit spinning.
They later decided the smallest detail of change in the incidence of the horizontal's leading edge had caused the problem. It was due to worn tooling being moved to a new assembly line location and an ever-so-small, almost unmeasureable change which had resulted in the leading edge angle being slightly changed.
It has since occurred to me that perhaps I don't have as much interest in spinning airplanes as I once did as a young instructor. I don't care if it IS an approved manuever.

[beeliner]

Thanks for that Chief spin comment George. If we measure our flying by decades instead of years we have a few things that stick in our memory beyond all others. Your Chief spin story prompted one of mine. I was taking my father (a pilot) for a ride in my friend's Chief. I had frequently done no-big-deal spins in it by myself. I said "let's do a spin- it spins nicely. We were at a safe altitude so I tried a spin and it just wouldn't spin with my large dad in the plane- just dropped a wing but recovered itself within half a turn. So I got aggressive. I pulled the nose high and just at the break kicked in the rudder and to make sure added aileron. That time it did spin and with the aileron it did a tight spiral. The inside wing was stalled so it was technically a spin, but the rotation rate was incredible- must have been about 2 rotations per second. I neutralized tha aileron quickly, kicked the opposite rudder, pulled out at 110 mph, and was way more suprised than my passenger. I never spun the Chief again. I checked the aged fabric carefully after the flight. Those Chief's are different about spins!

[GAHorn]

Beeliner...I don't know if I'm comforted to know my old Chief wasn't unusual or not.
Those old things were supposedly OK for some mild aerobatics, but I changed my mind after owning one. Even a simple barrel-roll ...wasn't so simple. It was more of a high-speed entry to a horizontal spiral...most of which involved plenty of time to wonder if it's ever gonna right itself again.

[N8249A]

Ok, I've adjusted the regulator ( in ) twice with little or no change in VAC. It still is running about 4.0 in cruise but I have to get the indicated over 95 to do this. I said I thought these were the "super" venturis because they are 9" or so in length. Is this correct?
The instruments were overhauled and the system was replumbed with new hoses. It has a regulator and a new filter. I am convinced that the people that put it together don't understand the venturis and most people don't know these older A/C. I recently had the system checked and there are no apparent leaks. I have studied the system and it appears to be plumbed correctly. So my questions are;

1 Best way to adjust regulator? Can I run the adjustment screw all the way in as a reference then back it out?

2. Is there anything to check with the venturis themselves such as new paint restricting something.

I really appreciate everyones input. This is without a doubt the most reliable source for information, etc for this A/C.

[N8249A]

OK, I'm an idiot. I don't have the super venturis. I have the 4" ones.
Can I install the supers as sold by Aircraft Spruce with just a logbook entry by an A+P?

I have been routinely getting 4.0 HG in cruise out of my current system
so this must be normal, but I have to be over 110 mph IAS to get it.

Thanks, Marty

[GAHorn]

Replacing std venturis with "super" venturis is a minor alteration,....just a logbook entry. (You're not an idiot. By the time this project is finished, you might be one of the most knowlegeable people around on venturi systems!)

[Walker]

If you put your regulator in a place where you can get to it "easily", you should be able to adjust it in flight, or safer still, the person in the right seat can adjust it. In regards to spinning Aeroncas, and most kites for that matter, I discovered that holding a little power makes them go in nice. Too much, though makes the spin go flat. Cutting the power fixes everything, as long as you put a halfhearted attempt at recovery input.

[N3243A]

Replacing std venturis with "super" venturis is a minor alteration,....just a logbook entry. (You're not an idiot. By the time this project is finished, you might be one of the most knowlegeable people around on venturi systems!)

Whoa there George!! What about the fact that the Aircraft Spruce "super" venturi (9" vacuum) is not an AN spec part and cannot be installed legally? Something about no basis for approval..... We went thru this in a rather heated discussion last year. Did you forget that the Spruce venturis are not AN spec or change your mind?

Bruce

[zero.one.victor]

Whoa there George!! What about the fact that the Aircraft Spruce "super" venturi (9" vacuum) is not an AN spec part and cannot be installed legally? Something about no basis for approval..... We went thru this in a rather heated discussion last year. Did you forget that the Spruce venturis are not AN spec or change your mind?

Bruce

Bruce, he's not changing his mind, he's "clarifying his position".
This week they're OK! (just don't you install them!)

Eric

[GAHorn]

Actually...you got me there, Bruce. I did not associate the "super" venturis description with the non-approved item. I'd forgotten they had no approval for aircraft use. Thanks for the reminder.

[HA]

oh, the abuse we heap upon each other

seriously, of course neither you nor I would ever just whip some shadetree fix at our aerochines without thinking through all the ramifications, so everything we would do will naturally be safe and yet cheaper.

but, apparently someone else (I wish I could find those killjoys) has not been so righteous and aboveboard in the past - imagine. So, the federales have had to invent procedures (paperwork, accountability, std procedures and parts) to try and herd those outlaws down the high road again. Stinks to be told, by the very existence of these procedures, that somebody out there doesn't necessarily trust you, but hey I understand they aren't really pointing the fickle finger at ME. So I don't mind doing my best to follow the party line. If I miss something, luckily I have my fellow aviators (pilots, mechanics) to hopefully see my oops and remind me. George seems to have accepted this function on this board - he must truly have a thick skin

If we don't like a procedure or current approval, we can try to modify it - there are even procedures for that, since this is America and all. But, due to the inertia of government it can take awhile - that's where the frustration sets in.

well, off the soapbox for today. Fly safe and think things through - aviation is best when you are ahead of it.

[blueldr]

So put the big venturi on your airplane and forget it. If anyone ever says anything, plead ignorance. It was always that way.
Who in hell is going to check it anyway? If some eager IA squaks
it, dump him and find a more reasonable guy. There are a good many well qualified , reasonable IAs out there. No one working for the FUZZ is going to know the difference and if they do , they're probably from the old school and are themselves reasonable. This does not seem to me to be an item over which sleep should be lost.