What was the very first certificated American civil aircraft that could be sold/purchased new under a time payment plan in the USA? What other distinction did this aircraft have re one of it's engine choices? Please be specific with your answers.

The Health Parasol came to mind, but I don't think it fits the bill.

I'll keep mulling this one over..

Not the Health Parasol, nor the Heath Parasol. Please keep trying.

I'll plump for the Alexander Eaglerock.

It had many engine options from the 90 hp Curtiss OX5 up to the 220 hp Wright J-5 Whirlwind and beyond to 270 hp. Some radials, some inline, air and watercooled. Not sure which engine specifically stood out from the others, the only distinction I can find is that the OX5 was the last Vee engine designed by Glenn Curtiss. Saying that, I have probably got the wrong aeroplane in the first place!

Well Rob, close enough. I commend you! The Alexander "Eaglerock" Long Wing was built under ATC #8 and had a short wing version and different engines, but the US Department of Commerce in April 1927 was perhaps more lenient in their first airplane registrations.

The engine distinction was that the Eaglerock aircraft designs were the very first airplane use of Glenn Curtiss's famous OX-5 engine that were certificated. The OX-5 went on to power many later certificated aircraft.

The long wing version was somewhat unusual with the longer of the biplane wings was the lower wingspan, not the higher.

Specifications

Upper span: 36'

Lower span: 38'

Chord both: 60"

Wings total area: 360 sq. ft.

Airfoil: Clark Y

Length: 24'11"

Height: 9'11"

Empty weight: 1,470 lb

Useful load: 760 lb

Performance

Max speed: 92 mph

Cruise: 80 mph

Climb rate: 485 ft/min.

Landing speed: 35 mph

Ceiling: 11,500 ft

Fuel: 37 gallons

Oil: 4 gallons

Range: 380 miles

Initial FAF price: $2,475 increased to $2,750 in late 1927.

If you wanted lighting for night flight-that was $20 extra.

Neat! $2750 is about $37k today with inflation, $20 being $270 or so.

What would be a comparable aircraft today? Maybe an AcroSport II?

Interesting cost comparisons. Well, it is a given they are both biplanes but with different airfoils and the Alexander Eaglerock long and short wing versions had balanced rudders. The OX-5 engine is of 90 Hp but the OXX-6 of 100 Hp was also used, but sparely as it was so much more expensive. Performance of the Alexander Eaglerock was far below in all respects that of the Paul Poberezny much later design. Appearance wise? Somewhat homely vs. sleek. The age difference benefits the latter design of Paul's in so many ways that it is hard to find similarities other than both being open cockpit biplanes. The latter day design may be harder to fly well as things happen more rapidly in its flight characteristics.

Incidentally, the late Albert Mooney first worked for Alexander in Colorado on the Eaglerock designs under the Chief Engineer Daniel Noonan. We all know of Mooney's ensuing fame. I highly recommend reading "The Al Mooney Story (sub-captioned) They All Fly Through The Same Air, as told to Gordon Baxter. Shearer Publishing, 1985, Fredricksburg, Texas. A compellingly great read that covers the M-1 through M-23 designs of Al Mooney from 1925-1968. He also designed aircraft for Marshall/Montague, Bellanca, Dart, Monocoupe, Culver and Lockheed-Georgia.