If one were to fill the fuselage of an aircraft with helium gas, how would that effect it's flight capabilities?

I’m not an engineer, but I’d imagine it would effectively offset a small percentage of the cargo onboard the plane. Think about how many helium balloons it would take to lift 1 suitcase, now how many could you fit in a fuselage? It’s an interesting question.

^I’m years removed, from chemistry, I couldn’t think of a better/stable gas…

@gorillapaws is correct. The difference in mass between helium and air is enough to make a balloon float, but it’s not a very large proportion of the weight of a typical airplane, so it would just be like it were a bit more lightly loaded.

For a drone, it might be a somewhat higher proportion of its weight, as drones can be pretty light.

A drone could no doubt be designed to be especially light and to be filled with helium so that it would be very light and able to hover with little or no energy needed. After all, see blimps and zeppelins.

^Would it effect the performance, of the drone’s capabilities flying?

The weight of the aircraft, is not necessarily what I’m interested in, but I did say drone, because yes they could be much lighter.

Ok.
I SHOULD have asked; if an aircraft is lighter than air, would that negatively affect it’s ability and flight characteristics?

I was thinking you might HAVE to fly them faster than normal, which would potentially make them less agile.
But more speed could mean a need for a more aerodynamic design…

Honestly.
I have had my aluminum foil hat on tonight, and I was trying to think of a way to recreate some of the recent (currently unexplained) “drone” videos.

Every person that understands drones (not me,) says that some of recent drones in like NJ, have been seen hovering for much longer than what they consider possible for the short power supply typical of such aircraft.

I was thinking, could it fly like a normal drone to it’s desired location, then cut/reduce motor power, so it could hover longer.
You know, because it had at least partial augmentation from a lighter than air gas.
Then, it maybe releases the gas, and takes off?......
Some of the way these things start to move, almost looks like a fast gas release reaction.
Think of what a balloon does if you fill it with gas, pinch the balloon knot closed, then let it go. The gas could explain the hovering, and maybe even give it a boost as it releases it when they seem to just fly away quickly. An unfortunate similar example, would be how “The Challenger” rocket tank behaved. A giant metal balloon, being propelled by gas escaping from the path of least resistance…

Spit ballin here…

Not significantly unless you are referring to an aircraft that is built like a balloon.

@MrGrimm888 Yes, it would affect the performance and flight characteristics.

You’re right that there are crucial differences at certain thresholds, for example:

* If the amount is equivalent to less cargo or fuel or whatever, then that’s all it is.

* If the amount makes the craft less than it ways with no cargo, then it’s going to be outside its designed specifications. A small amount may not matter much, but a large amount may put it into untested situations, and may cause some design assumptions to be incorrect, possibly catastrophically, especially if it is a computer-piloted drone or fly-by-wire aircraft, because those are programmed to assume they know WTF is going on with themselves, and they aren’t generally programmed (AFAIK) for weird situations such as being filled with helium.

The manual of my most capable drone (whose flight ability is impressive, to me, anyway) says not to attach ANY cargo or non-officially-approved object to the drone, or all bets (and warranties) are off. It’s of course erring on the side of caution and CYA, but it points to how changing the weight can/will throw off the flight characteristics and invalidate some of the flight programming.

* Being actually lighter than air overall is especially going to screw the design and autopiloting of any aircraft not specifically designed for that possibility. Most aircraft are designed to be able to land with the help of gravity, for a basic example.

Yes, a lighter-than-air craft will be less maneuverable, because it’ll be out of its design spec by a lot.

However I wouldn’t expect to “HAVE to fly them faster than normal”. In general, mass actually tends to help maintain speed, because it means the relative effect of air resistance is greater compared to the mass of the object. All else being equal, a heavy object is affected much less by air resistance (and gusts of wind).

But yes, it would mean being able to hover for very long periods of time (at least, without high winds).

And a tethered balloon (or one in no wind) can hover for an indefinite amount of time. In theory, a drone could drop an anchor . . .

The idea of releasing gas is interesting. Hmm.

^OK. (Just for conversation’s sake.)
So what if you custom made a drone for this.
Let’s say some hobbyists, thoroughly tested it after the build, so they knew how to fly it.

What about making lighter than air, with a gas, and putting a weight inside to offset the gas until it gets to it’s destination, then drops it’s weights (like a diver) to hover.
Now lighter than air, it could potentially hover for a time, then release the gas, to return to base flying normally again.

Couldn’t it be like there’s one remote for each stage, for the difference in performance.
Experts say these things (of the recent sizes) should require a “team” of people.

I mean, some vehicles have rain mode, insane mode, etc.
Those are designed to alter the way the vehicle performs.
If a car/motorcycle could have multiple “modes” why not a drone?
If the drone with gas + weights, weighs the same as the drone without either, it would be even simpler.

Yes, sure, if it turned out that was what was needed. Once could certainly make a lighter-than-air drone so it could hover while using minimal power, though it’d still need to apply some thrust to counter the wind, unless it could drop an anchor.

Or you could just be willing to drift with the wind.

Or you could wait until you’re starting to run out of power at night, and then have another drone with more power come over next to you, and turn the light off on one while you turn the light on on another.

Or you could have a tethered balloon with no devices, but shine a light on it from the ground.

I’m not at all clear what the actual design parameters are here, though. Lighter-than-air is a great way to stay up for a very long time. You could also drift with the wind and then later (eject lighter gas or not, and) switch flight mode to powered.

Well, I’m curious about the drones, we’re seeing.
Apparently, similar shit has been going on, and we seem to have an issue.

I see what you’re saying about an anchor now. It would need to maintain it’s desired position, requiring power…Duh…
Drones aren’t my wheelhouse…
Hence the question.

Watch out! For those Puffer Fish drones…

Dunno, buy the restriction on bag weight has been lifted.

You’d have to subtract the weight of the air in that volume and add the weight of the helium that replaced it. https://www.engineeringtoolbox.com/gas-density-d_158.html

^So. You’re saying there’s a chance?...