The International Cessna^® 170 Association

Hi
First post, I have made up my mind that a 170 will be my first aircraft purchase. I am curious about how many people out there have 170's that are set up for IFR flight. Can it be done with the venturi or will it need a vacuum pump? What mods need to be done?

Biscuit - you will find more than a few IFR certified 170s owned by members of this forum. Some IFR 170s have vacuum pumps, others have the venturi powered gyros. The Venturis powered gyros tend to be the Artificial Horizon and the Directional Gyro - most of us back up the venturi powered gyros with an electric turn and bank indicator. I have the venturi powered A.I. and D.G. with the eletric T&B. I had a partner in the aircraft once upon a time and was able to install a IFR Garmin 430. In addition I have a King Nav/Com - both OBS are loc/Glide slope. I fly often IFR . The venturi system seems to function realibly - however, stay away from icing encounters.

Thanks for the reply, it sounds like you have what I am looking for. I like the Idea of the venturi for vacuum, I don't plan on flying in ice, I Live in Fl. so that should not be a problem. Are to venturis needed one for each? Also where in the panel did you install the 430?

I also prefer the simplicity of venturis and I fly light IFR with my 170B. I don't know where folks get the idea that two venturis should be split ..."one on each side"... Cessna installed both on the right side. See your Illustrated Parts Catalog (IPC) for the installation.

Ice is never a problem for me either, since the airplane is not approved for flight in icing conditions, I never fly in it. No need for a heated pitot either.

I have one large venturi on the right side - produces plenty of suction. Just keep in mind that it takes some airspeed before the gyros spin up - usually about 70-80 IAS. You will also notice on downwind in the pattern when you pull the throttle back for landing the suction will descrease noticably. The 430 fit nicely into the hole left by the oldnav/com I replaced with the 430. Lower left hand side of the panel - below the yoke. I have found that the moving map is still quite useable on approaches - and, when you select VLOC you will paying more attention the OBS needle (loc/Glide slope) anyway. The lower left hand side works well enough for me and meets the IFR certification requirements.

My 170A is somewhere in the middle of the ocean, on her way to Sandhill Aviation, NH, for engine upgrade (TCM IO-360) and interior/exterior works. I keep thinking that I want to make her IFR capable, for ocassional "light" IFR. But the thing that stops me most is changing the classic appearance of the panel. Even if it is "light" IFR flying, it must be extremely reliable and my guess is that old instrument, aside of being hard to find, might not be as dependable as they should. Any ideas?
Could anyone post some pictures of your cockpits to see how you solved this matter. Thanks guys!!

wenetz-
Here's one way to do do an IFR panel while trying to keep it somewhat original looking.

It is surprisingly functional even though it's not the standard 6-pack. I got my intsrument rating in it in 1979.

WAAS approaches with vertical guidance (glideslope) at uncontrolled airports are especially impressive.

Click on image for enlargement.

Thanks Richard!

The panel arrangement you worked out for your 170 looks very nice and the pictures are excellent. Although you put in new instruments and gauges, you still keep the original setup. Thanks a lot, it really helps! I'll have to see how the price works out though. The 430 is a bit expensive I think, but it's sure worth the money.

Take care,
Pedro.

When I bought N4401B, it had a KX125 nav/com, an ancient Apollo COM, a King ADF, xpdr, and a Trimble VFR-only GPS. It was IFR, but only barely. I wanted an IFR GPS, and at about $16000, a Garmin 430 was actually the least expensive way to upgrade the panel for IFR. The ADF had quit working, so I removed that, the Trimble and the Apollo COM and had the 430 installed. Saved 10 pounds, too!

I added a Garmin 496 as well, and I find it makes a really superb addition to the 430. What ever flight plan or approach I have selected on the 430 appears on the 496 automatically, through a data link in the power cable. I seldom use the 430's moving map display. The 430 has WAAS, so you get a synthesized glide slope on all GPS approaches. Many of them are legal down to 250' AGL.

I used the same order to keep original. Had to combine instruments for room. SL30 & SL60. I have a large venturi.

John

I have a single stock venturi. It runs both my attitude indicator and directional gyro fine under 3000 ft on just the 4.2 inches it pulls. 4.2 is low for the new style gyro instruments however.

I don't spend much if any time above 3000ft but recently on my trip to and from Branson I was at 7500 ft. At that altitude my single gyro only pulled about 3.5 to 3.7 inches and my gyros died. Glad I didn't find this out in the clouds.

I am not advocating removing the venturi. In fact I'm likely to add another to see if I can correct the problem at altitude. Again I have a single venturi. Lots of 170s already have two and I think that was the IFR setup from Cessna.

I've also eyeballed the so called super venturi from Spruce or Wag Aero which pulls more vacuum and believe that may be a better way to go rather that just adding another standard venturi but there is no basis of approval for it and of course by airplane is otherwise stock.

Thanks for the picture John!

Bruce helped me to edit my previous picture for a better view.

John

N9149A wrote: I've also eyeballed the so called super venturi from Spruce or Wag Aero which pulls more vacuum and believe that may be a better way to go rather that just adding another standard venturi but there is no basis of approval for it and of course by airplane is otherwise stock.

Bruce, which venturi do you have, is it the original 4" or 8" suction? The super venturi you mention pulls 9"s but is not approved, Wag-Aero sells an 8" model which meets AN standards and are so labeled. I'm getting ready to install 2 of the 8" AN models and new style gyros.

I have a standard 4" venturi. BTW folks 4" is the vacuum not the fiscal size of the venturi. A standard 4" venturi is about 9 inches long. Confused yet.

Wow I'll bet two 8" venturis will be way overkill. Do you have two standard venturis now? If so are the plumbed together as the should be or each to separate instruments?

I'd plumb both lines together and try one 8" with a 4" first and see how that works. The 8" should be enough by itself and the 4" just along for the ride. I'd just leave the 4" in place to plug the holes. What regulator are you going to use?

As for whether the venturi meets a AN standard or not does not decide whether the venturi is legal to install or not. But it might make the installation slightly less illegal. In other words one would have to determine whether changing the venturi it is a major or minor alteration and the venturi meeting a standard may be more acceptable than one that doesn't. Then at the end you need execute the appropriate paper work and once properly executed the installation becomes legal.