So install a suction gauge. They make them itty-bitty versions that I believe surface-mount so you don't even have to cut up your panel,just find an empty spot. Pretty easy job to cut a tee into the vacuum plumbing & run a line to the new gage. Surprised that anyone would have installed vacuum gyro's without a suction gauge,but a friend's A model is set up the same way.
Eric
Flying in the soup
Moderators: GAHorn, Karl Towle, Bruce Fenstermacher
-
rudymantel
- Posts: 451
- Joined: Sat Nov 23, 2002 4:03 pm
John, that does sound like a pretty hairy experience.Glad you got out of it. Ice is perhaps the one disadvantage of venturis over vacuum pumps. Of course we all try to stay out of ice, especially if it's severe enough to block venturis.
I have venturi-driven gyros with a vacuum gage and like the system.
Rudy
I have venturi-driven gyros with a vacuum gage and like the system.
Rudy
Water in the pitot system can freeze and do what you experienced. Later Cessna's had a pitot-system sump installed, which you can certainly add if you like.wa4jr wrote:I am not too worried about the pitot tube either, as I've flown with it blocked by internal ice. While encountering rime ice in November over Kentucky, I did worry about losing the AI and DG. Has anyone ever had the venturi tubes ice up enough to prevent vacuum and kill the gyro instruments? Airspeed indicator is one thing, but I would hate to loose the vacuum gyro instruments as well...especially since there is no vacuum gauge and thus no way to know the AI is dying and flopping over until everything else starts to go down hill. The only usable instrument at that point for attitude control is the turn coordinator and I think it is useless for anything beyond a standard rate turn and of course useless for pitch.
If the airframe icing is vicious enough to fail the venturi's, the airframe will already be heavily iced up and in a descent. I don't think venturi icing will be your biggest problem. This airplane is not approved for any kind of icing condition. I have a suction gauge, but the OAT gauge is more important, in my opinion. (I'd a lot rather have venturi's than I would a dry vacuum pump.)
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.
I do have the sumps...actually the static system has a small section of tubing running vertically down from the tee fitting and is then sealed off...I suppose to make a sump of sorts. I have had the plastic sump added to the pitot line. The water that was frozen and causing a problem was in the pitot tube itself, between the little flapper cover and the wing. Guess some water managed to get around the flapper in a rain storm and then froze...from my days tied down on the ramp. I'll think about a suction gauge if I ever get around to redoing my panel with a center stack. You said what I wanted to hear George, in that the airframe would ice up to the point of going down before the venturis iced up. Then there is some spindown time on the gyros before they become a problem. No, I don't fly in ice as a rule, but I can see the real possibility of getting caught on top of a low overcast and needing to do an instrument approach down through the muck while ice is starting to build up. Was also thinking about time when I am clawing my way up through the icy clouds to VFR on top. But warmer weather is coming so this will not be such an issue for the next few months...if only I could get my fuel tank repaired.
John, 2734C in Summit Point, WV
In my younger, more foolish days (notice I said that in a relative sense) ..... I once got caught on a pipeline patrol in fog while within the right-of-way cut thru trees. I was in a C-140 with only a T&B and was up against the proverbial wall with sudden zero-zero visibility and obstacles all around.
I pulled up into a needle/ball/airspeed climb to what I knew to be clear above 2,000'. What they don't tell you in Instrument training school is that the vertical climb speed is also affected on needle/ball/airspeed. It took roughly 24 hours to climb that 1500' ASL.
Ten years later I found myself foolishly on top of an undercast nearing dusk, while on a trip to the Atlanta area. We decided the best thing to do in a non-electrical system Aeronca was to descend thru it and land near BHM. Descents are a lot easier on T&B. Keep it straight and avoid turns and power changes. (In other words, trim it to make it as stable a glide as you can.)
..... I once got caught on a pipeline patrol in fog while within the right-of-way cut thru trees. I was in a C-140 with only a T&B and was up against the proverbial wall with sudden zero-zero visibility and obstacles all around.I pulled up into a needle/ball/airspeed climb to what I knew to be clear above 2,000'. What they don't tell you in Instrument training school is that the vertical climb speed is also affected on needle/ball/airspeed. It took roughly 24 hours to climb that 1500' ASL.
Ten years later I found myself foolishly on top of an undercast nearing dusk, while on a trip to the Atlanta area. We decided the best thing to do in a non-electrical system Aeronca was to descend thru it and land near BHM. Descents are a lot easier on T&B. Keep it straight and avoid turns and power changes. (In other words, trim it to make it as stable a glide as you can.)
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.