Weight & Balance

Ronald and John make some good points.

If your friend doesn't have a recent empty weight for his Ercoupe, it's worth getting one. They've all had a lot of additions and subtractions over the years.

Someone can correct me if I'm wrong, but I believe that the original design weight for the 415-C was 1400 lb., but the Powers That Be were spooked by the novel "unspinnable" certification and insisted on reducing the gross weight by 10% - giving us the stock 415-C gross weight of 1260 lb.

Later models gained that gross weight back, and now there are STCs available to upgrade gross weight in earlier models to 1320 lb. (this was nicely congruent to the previous Sport Pilot & LSA rules) with a few modest upgrades, or to 1400 lb. (now also Sport Pilot applicable under MOSAIC.) The 1400 lb. STC involves changing the elevator to the split "E model" elevator and, I believe, upgrading the skin above the nose tank.

If the engine, like most, has been upgraded to a C-85 then the 1320 lb. STC is easy to accomplish.

That's not a lot compared to the empty weight of a latter-day Ercoupe. The original design was aiming for 750 lb. empty weight, but that was before adding an electrical system. Throw in a starter, generator, voltage regulator, battery, lights, comm radio, and transponder and you're lucky to stay below 850 lb. The original design weight was also with a polished, not painted, fuselage... and very basic instrumentation.

As John mentioned, the best bang-for-the-buck is the certified EarthX 900-series battery at a weight savings of 18-20 lb. for less than $1000. A lightweight starter & alternator can save that much again but for a cost of several thousand dollars. A wooden propeller saves weight but you lose a little performance.

My Ercoupe was 896 pounds when purchased. I removed two venturis, a vacuum turn coordinator, and vacuum attitude indicator. Those were replaced with a Garmin Aera + GDL 50 so I got all that functionality back plus mapping and ADS-B traffic. The new gear weighs about 1 pound total!

I removed the old, heavy radio & transponder and replaced them with new lightweight Trig units, Even the new brackets are a lot lighter.

Someone had constructed a 3-piece floorboard that was bracketed together. I cut a new 1-piece, original-style floorboard using very light 6mm Okume (kayak) plywood and saved a pound.

I also replaced the main "fat" electric cable (battery to master to starter) with MIL-W-22759/16 and a master solenoid STC. That saved almost three pounds! The old cable had a much heavier jacket and was several feet longer than it needed to be.

On the down side, I added an electric fuel pump, baggage compartment, and shoulder harnesses. Those cost me about 7 pounds total.

Now that the 1400 lb. STC is Sport Pilot legal, that's my next move. I just need a new elevator!

Ercoupe empty weights can vary a lot and there are also several different gross weight limitations depending on models and STC. Most weigh in empty at between 850 and 950 pounds depending on wing covering, propeller, paint, instruments, upholstery, battery, accessories, etc. Gross weights can be 1260, 1320, 1400, or 1450 for the Forney and M10. So the real useful load can vary a lot.

Look for ways to reduce the zero fuel weight. Changing to a lithium battery can save approximately 20# for example.

I'm a private pilot new to the Ercoupe, helping a friend with an Ercoupe refresh (under the direction of the local EAA chapter and an A&P) and hoping to fly with him or taking my wife for a ride.  Neither of us is heavy, probably 5-11, 170 pounds each (wife is lighter).  I'm confused as to the real useful load for Ercoupes.  It appears from the POH's I've read that the useful load is about 432 pounds, with the STC.  A full fuel load is about 24 gallons (6x24=144 pounds), leaving 288 pounds for radios, ELT, cargo, etc. As I watched on YouTube, how do two grown adults stay within the 280 pounds to stay within max gross weight?  Obviously, carrying less fuel is one way, what else am I missing?