You can overfill the tank from the aux tank. It adds about 15-25gal depending on who you ask.

L/D is independent of altitude. You gain nothing by climbing (in a no wind situation) as long as your IAS stays the same. You can do Carson Speed/or Vy speed at FL250 or at 500ft - makes no difference in range. The common belief that piston airplane maximum range improves with altitude is based either on constant power or constant TAS, neither of which provides the desired maximum range profile. So if you were out to break some sort of record, climbing would be a waste of fuel.

This is not true for turbines for reasons I don't understand. However, max endurance for turbines is also achieved at any altitude. Nothing is gained by climbing.

...and we're back.

You go ahead and try to put anything near 25 gallons of overfill in an A*. You'll be cleaning up a lot of those extra gallons from the ramp. Actually, if you pull that move where you live in the People's Republic of California, you'll probably get fined, picketed, and maybe beaten by the police, lol.

Correct me if I'm wrong; even if L/D max doesn't change as a function of altitude, doesn't TAS? That being so, wouldn't we get longer range in the thin air at altitude for a given IAS?

I think you actually get longest range at L/D max while in ground effect. Obviously that presents some challenges on long range flights. Max Conrad set some incredible max range flights and did them all at low altitude if I am remembering correctly. He was also flying a piston engine that remains efficient at low power settings.

For turbine powered planes the range extension at altitude is generally a function of getting the powerplant(s) up to an altitude where they are efficient. The airframe seems to only require proper IAS for efficiency.

Significantly less power (fuel) required to fly the target IND. airspeed down low.

This. The pesky Russians did a lot of experimenting with those Ekranoplan wave skimmers. They could carry a lot for the power they used and were more fuel efficient than airplanes, but seemed to have other problems.

By down low in ground effect, you're talking about witching 10' or so of the deck, right? Adam asserts he can go 2000NM on a tank of gas. Are you folks suggesting a 2000NM cross country 10' off the deck? Because if you're not, you'd best climb for some TAS I think. Also, while I know airplanes are far more efficient in ground effect, I don't know at what altitude the difference between IAS and TAS becomes large enough to be more efficient than ground effect because I don't know how to calculate the efficiency of ground effect.

If only we had a brainiac engineer around, say, someone from Southern Indiana...

Wait for it...

Are you familiar with Carson speed Craig?

TAS is irrelevant (if we are talking piston engines).

Why is TAS irrelevant?

Lets say target speed is 140kias.

At Sea Level, you go 140 kias on 20gph. Your TAS is 140kts. You have a 100 gallon tank so your range is 700NM.

At FL230, you go 140kias on 40gph. Your TAS is 280kts. You have a 100 gallon tank so your range is now 700NM. The rub is you also had to burn fuel to get to FL230 that was not required at sea level.

That would make sense if your fuel burn doubled at altitude where your speed also doubled, but that's not at all my experience.

What am I missing?

You have to power way back to go that speed at low altitude. I think you are missing how little power it takes to go 140kias at sea level.

You are always taking a chance, that's the nature of existence.

Even if you overhaul your prop after every flight, you take the chance that no maintenance error is introduced during that process. Every flight you take will be a post maintenance test flight under those circumstances.

Mike C.

You have to power way back to go that speed at low altitude. I think you are missing how little power it takes to go 140kias at sea level.

Then throw in the real world factors of climb fuel burn and engine efficiency at lower RPM.

Independent of obstacles and winds aloft, the lower the altitude the better in a piston.

This is where people get confused when turbine aircraft are considered. They certainly don't have linear fuel specifics. The engines need to be maxed out in order to be efficient, so the engine must be pre-selected to match the target altitude.