Long range cruise

[laserpilot]

I might want to do some long range cruise flights to Latin America.

I see on page 5-26 of the AFM the landing gear should be retracted. But how

What is a practical rule for long range cruise ?

[ingramleedy]

That page was amended/corrected.

[Chris]

I see on page 5-26 of the AFM the landing gear should be retracted. But how

I suppose if you have a support plane you could try a variant of the Gladys Ingle technique, but I can't recommend it.

Nice catch. For anybody looking, that is shown in the 01-Jul-2014 DA40-NG AFM, which is still available on Diamond's website. Corrected in a later revision, as Ingram pointed out.

I can't say I use long range cruise much. I typically just use whatever app-recommended power settings will give me the range/duration/reserves that I'm looking for and then tweak the settings during flight as necessary using the range rings.

[vincent99]

Assuming you have the long range tanks (39gal total) the practical rule is the meatbags inside are probably the limiting factor.

On the next page you'll see at 10k' and 45% you're burning 4gph, at ~100ktas that gets you ~800nm in 8 hours with still 7 gallons to spare. You could squeak out even more if you carefully consider required reserve, climb time, winds, etc.

On the other end 92% is 8.3gph and 143ktas, so ~550kts in a little under 4 hours, with 1hr reserve.

So just choose how long you want to be in a seat at a time in between those possibilities and there's a power setting for it.

With wife and kids on board I'd plan legs ~500nm <4hr max @ 80-90%. You don't get much more speed out of the last 10%, but it's also only about 1gph extra. And in 4 hours it's impossible to run (full) tanks dry.

[laserpilot]

In between islands I don’t want to land, and getting fuel in Brazil might also be a challenge. That’s why I ask.

[Rich]

To get max range the general rule is cruise at best L/D ratio, which is basically best climb speed and reduce power to maintain level flight at that speed. "A little faster" for headwinds, "a little slower" for tailwinds. This speed does change as you burn off fuel. For those of us with Lycomings, lean-of-peak applies here, but you have to concern yourself with extended running at very low CHTs - whether LOP or not.