[logicallee]

I find it very hard to believe that landing gear isn't fine with landing under full starting weight -- after all what if you need to land shortly after taking off for some reason? (return to leaving airport.) So I "plane" don't believe it's an issue.

Regarding fuel weight not decreasing - could hydrogen fuel cells be burned and the resulting (h2o, water vapor) simply be left as contrails?

Reference: https://www.quora.com/What-does-hydrogen-give-off-when-burne... "In a flame of pure hydrogen gas, burning in air, the hydrogen (H2) reacts with oxygen (O2) to form water (H2O) and releases heat."

[dexterdog]

First, that would be an emergency landing. Second, they would likely dump the fuel.

[daenney]

They wouldn't, necessarily, be able to dump fuel. Most modern short to mid-haul aircraft like all of the Boeing 737's and the Airbus 320 series don't have a fuel dump system. It's only long-range twin-jets that are likely to have a fuel dump system and in some cases that's actually depending on what the customer ordered.

> (a) A fuel jettisoning system must be installed on each airplane unless it is shown that the airplane meets the climb requirements of §§25.119 and 25.121(d) at maximum takeoff weight, less the actual or computed weight of fuel necessary for a 15-minute flight comprised of a takeoff, go-around, and landing at the airport of departure with the airplane configuration, speed, power, and thrust the same as that used in meeting the applicable takeoff, approach, and landing climb performance requirements of this part.

http://www.flightsimaviation.com/data/FARS/part_25-1001.html

[logicallee]

This doesn't pass the smell test for me. The vertical velocity when it lands it not very great - if landing gear has no trouble supporting the plane during taxi off under full weight, I find it preposterous (and reckless) that it would be insufficient for landing. The idea that planes routinely dump fuel if they have to circle around and land immediately after take-off is absolutely ridiculous to me: if there is nothing wrong with a plane, highly combustible fuel is far safer inside than outside of it.

I found your suggestion so ridiculous I Googled "do planes dump fuel" and got this top answer

http://aviation.stackexchange.com/questions/29232/do-airplan...

"Do airplanes dump fuel before landing?"

For which Google picked the summary: "There have been many explanations given but ultimately the answer to your question is "No, aircraft do not dump fuel prior to landing unless it is absolutely necessary.""

Reading that page: as a rule fuel is not dumped!

[nradov]

You're not seeing the whole picture. Airliners don't routinely dump fuel during normal operations. However, if there's an emergency and the pilots decide to divert they will often dump fuel (if possible) or simply fly in circles to burn off enough to bring the airplane down to a safe landing weight. Safety isn't just a matter of preventing the landing gear from collapsing. A higher weight means a higher landing speed due to stall limits and thus a longer stopping distance and greater risk of brake failure or runway overrun.

[logicallee]

But we're not actually talking about emergencies here at all, but rather "by-design" in which nothing is wrong. And a future design at that!

I hope you can see why I am skeptical that a future landing gear for electric airplanes would not be able to support the fully loaded landing weight, which is not reduced as the batteries are depleted.

The idea that landing gears just "can't" support all that weight seems silly to me. The solution can be as simple as having twelve wheels instead of six, or another set of shock absorbers, or something short of "well sorry, you'll never build a landing gear that lands safely at that weight. Can't be done."

Note that I focused on just the weight the landing gears support - your other observations can remain on-point. I just don't buy that particular argument, just about the landing gears.

[dexterdog]

I was specifically talking about an emergency situation. Planes don't do early landings when nothing is wrong.

[scrooched_moose]

The difference is fatigue. I'm sure the landing gear can support the full weight, but how many times?

The gear may be rated for 20 uses at full takeoff weight or 100,000 uses at empty weight.