Can I get my private pilot training in an sport plane, specifically an Ercoupe? I know the paperwork would probably say “without rudders”.
I figure it would have to ADS-B?
First, the Ercoupe is not a light sport aircraft. It is certified in the Normal category under CAR 3. The Univair 415C and 415CD meet the criteria outlined in Part 1 to be flown by a person with a Sport Pilot certificate.
Next, the big considerations are
61.87(d)(14), which requires pre-solo training on slips to a landing. You cannot cross the controls in the Ercoupe to do a slip (forward or sideslip).
61.93(e)(9), which requires training in the use of VFR navigation and communication radios prior to solo cross country. There is an exception, but it only applies to students pursuing a Sport Pilot certificate.
61.93(e)(12), which requires training on flight solely by reference to the instruments prior to solo cross country flight.
61.45(b) requires that an aircraft used for the practical test must have the equipment for each area of operation required for the test and no prescribed operating limitation that prohibit its use in any of the areas of operation required for the test.
You didn't mention which model of Ercoupe you have or how it is equipped. These were basic airplanes and didn't typically have gyro instruments. While it may not have a VOR or GPS installed, a handheld GPS may be used to train and test, as long as you can perform all the requirements of the Private Airman Certification Standard (ACS). Intercepting and tracking is the one task that some people have a problem understanding. You could also use a handheld Comm radio, if needed.
Alternatively, you could do most of the training in the Ercoupe and the other tasks in another airplane that is capable of performing the maneuvers.
Another issue might be that procedures used in the Ercoupe might not translate well to other airplanes. You steer the Ercoupe on the ground just like your car. You use the yoke. In most other airplanes, you steer on the ground by using the rudder pedals. In the Ercoupe with a crosswind, you land in a crab, because you cannot cross the controls. In other airplanes you would touch down with a wing low and aligned with the runway centerline (hopefully).
I have flown an Ercoupe. It didn't drop the nose in a stall, just sort of mushed along in a nose high attitude.
Great question. A light-sport aircraft can be used for training to obtain your private pilot certificate, provided the aircraft is properly equipped for the training required and the aircraft manufacturer does not specifically prohibit such training in that aircraft. ADS-B out equipment is not mandatory unless you will be entering airspace where ADS-B out is required. This would be the same airspace where a transponder is required. See 91.225.
It used to be that you could get your PP in an Ercoupe 415 without rudder controls and receive a PP certificate limited to Ercoupe 415's, but it appears that is no longer in FAA Order 8900.1. As noted above, later versions of that aircraft from Alon and Univair have rudder controls and can be used to get your PP. The later 415C and 415CD models can be considered LSA's and operated by Sport Pilots, but still used to get your PP without limitation.
Of course, the aircraft would need sufficient instrumentation to do the “flight by reference to instruments” task. At least in theory, that could be done with nothing but very basic flight instruments (airspeed, altitude, turn and bank aka “needle and ball”, and mag compass), but it's a whole lot easier with gyroscopic attitude and heading instruments.