How far can you go?

The 8.000ft “industry standard” is probably also sales driven because for NA engines this is where you get the highest TAS…

I have never seen 8000ft as being defined as an industry standard

I never said it was an actual standard, but maybe it is, who knows? It is simply the number “everybody” uses when quoting cruise performance.

6,000 to 8,000 feet (ISA) is around full throttle, 75% power for most normally aspirated reciprocating engines – which usually translates to optimum cruise TAS – at least the TAS cruise speed quoted in the marketing literature.

I have not figured out how to import the range radius for the vintage Super Cub, but with a 90 HP Continental and 35 USG it has bladder testing endurance. 400 nm with ample reserves is a realistic cruising range. At a best range speed of around 75 knots and 45 minute reserve, on a smooth day, VMC range might be over 550 nm.

Maximum TAS is nearly always obtained at sea level for a normally aspirated engine.

8000’ is often quoted as it is about the maximum altitude that can still provide the maximum continuous or cruise power setting.
That will probably be WOT but with a more economical mixture setting and resulting in a slightly lower TAS than the max power sea level case.

So is IAS….

Can you explain why?

And while I know both are flawed, TAS is at least an actual speed through the air. Yes you need altitude but to compare on IAS is really odd.

Different aircraft tend to fly at different altitudes. You wouldn’t advertise an A320 by its speed at 8000ft and you wouldn’t advertise a C172 by its speed at 12000ft.

As to the Cirrus SR22T or Piper PA46 argument, these are touring aircraft designed for FL200+. If you don’t intend to fly them there, then you’re not really the target audience.

NA piston aircraft perform best at 8000ft which is why this is a very sensible altitude to use in comparisons. All POHs assume ISA (and usually give another set of values for above and below ISA) so TAS is the best way to compare aircraft performance.

Peter’s argument very much applies to how e.g. the T182T (the turbo fixed gear C182 that Cessna stopped producing last year) is marketed. It has a very draggy airframe but the TIO-540 makes it climb to FL200 and up there it is almost as fast as the TR182 (retractable gear) because the air is so thin that dragging the gear comes at a very small penalty. Same goes for the SR22T — at FL250 the fixed gear has a negligible influence. So the T182T is marketed with its high speed at a level it is rarely ever used while it is at least 20kt slower at normal cruising levels than its RG sibling.