Northern IL Mechanic and Help, Suction Problems!!!

[derekhorner]

Hello all, hope Im doing this right. This is my first post ever, I am currently a new owner and still a student pilot. I have waited several years to finally get my own plane and start training. So with the purchase of a new plane, I have some questions with a couple things I have been having a problem with and figured I would start here since I live in a fairly small town west of Chicago. (Rochelle, IL).
So problem #1.
I'm having problems getting my suction to remain steady. Some days everything works fine then the next day I just don't get enough. I believe I have a single super venturi, running two instruments, My Artificial Horizon and Directional Gyro. What my flight instructor has observed is that everything seemed to start working again, then all the sudden the DG tumbles and we lose suction and use of those two instruments. I will say that I do not think I have a pressure relief valve, so not sure if that could be causing it or not. The previous owner replaces all the lines trying to fix it, so I'm guessing a leak is not the reason. Logic tells me, i may need to get another venturi, or maybe my DG is broken, but honestly, I know nothing about this, I'm learning and loving it but trying to save a couple bucks by getting some answers before I have an A/P do further checking for me.

Problem #2
while doing pre flight with mu instructor I found some scratches on the rudder on the elevator control connector side. Once again, I came to the internet to diagnose and read in the owners manual that the rudder deflection was set by increasing the number of washers or spacers to bring the rudder horn stop out to restrict more. I understand it that the Rudder should only deflect 16 degrees L or R, and Plus or minus 1 degree. I then noticed I have no washers and my rudder has full range of movement. So i guess the fix is installing more washers on the rudder stop till i get full clear movement. Can I do this legally or should I have a A/P do this. I want to do it not to save money but because i love learning about this stuff. I also want to do things the legit way.

#3
Anyone know anyone that works on 170 in the North central IL area?

Thanks everyone!!!

[Bruce Fenstermacher]

Hello Derek,

Suction.
You think you have a super venturi. Why do you think that? A super venturi is longer than the standard 4" venturi when measured from the edge of the front bell to the back. A standard 4" venturi is 10". If yours is not longer than 10" it is not a super venturi.

Does your system have a suction gauge in it telling you what suction you are getting?

All DG and AHs are not created equal. The old AN gyros ran on 4" of mercury which is what the standard 4" venturi can pull. Modern pictorial gyros need about 5.25" of mercury to run correctly though some see satisfactory operation on less. Does your DG have a full compass face or does it have a strip that moves left of right with compass headings on it. If the latter it is an AN type. Is your AH the standard 3-1/8" round face or is it larger. If the latter it is a AN type.

I have one of each a pictorial AH and a AN DG. I find that with one super venturi, even though the suction gauge indicates enough vacuum, at over 7000MSL or so it is not enough volume of vacuum. Or at least that is what I suspect. At 1500 MSL it works fine.

Rudder.
Your rudder should not touch any part of the elevator or control horn when deflected. One adjusts the stops so only 16 degrees can be attained and the rudder should not hit anything at that adjustment. You can not do this work and return your aircraft to service UNLESS you are qualified to perform the work OR you do it under the supervision of a person who is qualified to perform the work such as your A&P. What you need to do is find an A&P who doesn't mind looking over your shoulder or you looking over his.

[GAHorn]

WELCOME!

#1-- Do you have a suction/vacuum gauge? In order to determine whether the problem is loss of vacuum or a failing gyroscope..it would be helpful to have a gauge in the system to confirm the presence of proper vacuum. Also, why type/model gyros do you have? Older AN style? or modern pictorials?

#2--You don't say where the scratches are, but we can presume you mean it has contacted the elevator. Any changes to your flight control rigging will legally require the supervision of a certificated A&P. But the short answer is, yes the rudder stop may be adjusted, but also the rudder cable/rudder pedal rigging should also be checked. Our Library has the rigging instructions available free to TIC170A Members and I hope you'll join!

#3-- You've come to the right place to ask that question, and we have several Members in the area who will likely soon make recommendations.

Again, WELCOME!

[c170b53]

Derek, welcome to the association and thanks for your questions. Seems the previous posts will help you, both Bruce and George are some of our best.
I'm on the West coast, in Canada and I know of Rochelle Il because I've flown over it several times and almost had to land there in bad weather. I have this organization to thank for getting me out of a habit of flying the patch . I've since visited and enjoyed many great places in the U.S. I'm hoping your 170 is as good to you as my 170 has been to me.
With regard to your rudder, there can be a few things to consider. As an example , you might want to look at the condition of the bolts at the tail that act as rudder stops and look at the condition of the arms on the bottom of the rudder which contacts the bolts. The arms sometimes get distorted or they may be ok but if your new to aircraft maintenance , you're wise to seek oversight when you feel you're lacking information, it's the best way forward. Understand learning your plane will take time, try to find a IA that has time for you and willing to teach you the basics. Again good luck with your 170

[strangebird]

Lots of older airplanes a Poplar Grove, you might want to call them not that far from Rochelle.

http://www.poplargroveairmotive.com

[johneeb]

Derek,
You might try Brad Brady from Dwight, IL. Brad and his dad are long time members of the Association.

[N8293A]

Derek,
Welcome! I have to recommend the guys/gals at Poplar Grove Airmotive. I used to be based at KARR and had my airplane maintained at C77 for the last 10 years. They are very easy to work with. I was so satisfied that I moved up to C77, and now live on the field, and obviously will continue to use their services. Please feel free to contact me if i can help with anything.