I didn't find this thread until now, some years in the future. Chris at Del Air was very helpful with my swap of C175 wings onto my 54 170B. There is the letter from Cessna that discusses swapping wings. Per that letter, the 3 things that have to be addressed are: increased fuel capacity, different fuel vent plumbing and electric fuel gauges. IMHO, this swap only really makes sense if you have other wing issues in addition to wanting more fuel. In my case, the 170B came to me with both wings previously swapped from different donor aircraft with different twists, resulting in a heavy left wing that could not be rigged out. Since I had a set of 175 wings, it made sense to make the swap. It gets complicated because a flight manual supplement is required, and this document must be approved. In the end, we had to use the 175 unusable fuel figure which was 9 gal. So, doing the math, I have 52 gal total fuel, but only 43 usable, which means I actually gained only 6 gal of usable fuel. (However, if one is comfortable doing it, a common pilot technique will allow 4.5 gal of that 9 unusable to make it to the carburetor and out the exhaust.) Initially, 2.25" Mitchell gauges were installed. These worked well, but the only calibration method available was to bend the sender float arm to make the gauge read "E" with 4.5 gal of fuel in the tank. A better option was Aerospace Logic FL202 fuel gauge. This is a TSO'd single 2.25" gauge that display's the quantity in 2 tanks, both with an analog bar graph, and a digital value. Even better, the gauge can be calibrated to your senders. The calibration procedure requires the aircraft to be leveled, and the tanks filled in 2 gal increments from the unusable quantity, to full. This will take some time, but the result is a very accurate gauge. Be sure to use original C175 senders, as the PMA'd McFarlane senders will not work with the Aerospace Logic gauge.
This owner is very happy with the results after the swap. Further, it was a pleasure working with Chris, as he came through, delivering everything he promised, getting it all approved - even if the feds he had to work with caused some significant delays along the way.
PS to the above: Since writing the above account, I discovered the resistive senders would often "drop out" near the bottom of the tank, causing the corresponding gauge to all of a sudden, intermittently indicate zero fuel, or empty. To remedy this, I again swapped the senders in the tank, this time to the CiES digital sender (Here:
https://ciescorp.net/applications/small ... ft/cessna/ ) This triggered another change in the fuel gauge, this time to the AeroSpace Logic FL202D (Here:
http://www.aerospacelogic.com/index.php ... gory_id=70) This solution requires a slight re-wire, as the sender needs 12vdc power, but the result is really worth it. This sender is "non-contact," meaning there is no wiper contacting a resistive element with the accompanying intermittent issues. This sensor has a lifetime warranty, and is calibrated precisely to the installation; so it is quite accurate throughout its range. Finally, even though this thread is about 175 wings on a 170B, CiES also makes a fuel sender that fits in the wing-root and replaces the mechanical gauge/sender our 170s came with. Something to consider when one or both of your stock gauges breaks, or you can no longer stand its accuracy issues.
