Credit to A-4K on the game's official discord

Ideally all joints on a vehicle should be at least 15kg, anything below this is likely to create issues, such as a black screen, or crashing. This isn't a strict rule, and does depend on your physics rate and the relative mass of the craft and the part that is moving, so you might get away with smaller joints in some instances (for example cockpit levers or switches), in such cases it is still worth keeping the weight as close to 15kg as you can.

you can multiply the mass of joints between 0.1 and 10 times in the editor, (so you can also make heavy joints lighter). This means that, for any given joint the minimum unmodified weight should be at least 1.5kg.

for example for either a hinge joint or a swing joint this could be a radius of 0.1 and a length of 1, or a radius of 0.2 and a length of 0,25; either of which will provide 15kg with the multiplier at 10.

as a general rule heavier joints are stronger, and if your using multiple joints in the same system (for example complex gear bay doors) you'll usually want the last joint in the chain to be at least 15 and each previous one being progressively stronger

The gear box ratio should always be positive (above 0) whether your using a piston engine or jet as the input, and should be viewed as being absolute ( as a distance from zero). All parts that are designed to work with gearboxes for propulsion (propellers, ducted fans and rotors) are designed such that they can be rotated either clockwise or counter- clockwise (CCW) and can be switched in the parts options.

gear ratios vary depending on the relative inputs and outputs, but can generally be calculated by dividing the desired input by the desired output, so if you have an engine with a peak RPM of 4000, and want a prop to spin at 2000 RPM, you'll want a ratio of 2, if you want the prop to spin at 1800, you'll want a ratio of 2.2222... and so on.

generally speaking for ducted fans, you'll want a high RPM and thus a lower gear ratio. For rotors you'll want a high gear ratio as the optimal RPM for the rotor is somewhere between 300- 600rpm (see the AH-67 example vehicle for an example, the gearbox for the turbines is shown on the right)

For props it depends heavily on size and target RPM (which you can find discussed here in the propeller guide created by BIG_HAM which has everything you could want to know about propeller design).

if your using a Jet turbine as our primary power source it is likely to be operating at a peak of over 10,000rpm which means gear ratios will tend to be larger than those from a piston engine

OPR is the overall pressure ratio of your turbine, this is the difference between the pressure of the air prior to entering the inlet and after exiting the compressor. so if the OPR is 1 no pressure change is taking place, and if it's 50 it's 50x denser than it was when it entered the engine.

for most turbines in real life the OPR will be somewhere between 2 and 50 with a few falling slightly above 50 opr such as the the Rolls-Royce Trent XWB (used in Airbus A350 XWBs) with a OPR of 52:1.

for flyout generally speaking it's best to stick within this range though depending on your Physics update rate and other factors you may be able to go slightly higher but there shouldn't be too much of a reason to within the realms of real world aviation.

Landing gear and rotors are both parts that have a physics reaction with the rest of the aircraft, this means when the aircraft is too light the part can potentially behave in unusual and unintended way, or cause an issue such as a black screen.

For Landing gear, you can either increase the weight of the craft or decrease the size of the gear, or look at alternatives such as fixed wheels if neither of these are optimal. if the aircraft is too light for the gear this can create issues for take off and landing anyway, such as random bouncing and instability.

for rotors you can either adjust the physics update rate or increase the craft weight to try to solve this issue.

The Physics update rate is the number of times in a second that the game will attempt to make physics calculations for various parts of your craft ( all wings, all fuselage (that is marked with Aerodynamics), and most conventional parts).

Physics calculations are the main reason for the relatively high systems requirement of flyout.

a higher Physics Update Rate can potentially fix a blackscreen issue but will also increase the load on your system.

the Physics update rate can be found under Simulation in settings, from either the main menu, or the flight mode menu (but not in the editor).

The game has a number of graphical settings that can be used to improve performance on your machine, and in turn reduce the likelihood of black screen errors. it is also worth noting that these are not set automatically based on your system so once your black screen error has passed it may be worth turning some options down if your experiencing a low frame-rate.

these options (just like with the Physics rate) can be found in settings from the main menu or in flight mode ( not in the editor); though it is better to change them from the menu as the game needs to reload the world once some changes are applied.

for most systems setting Sky to simple should be sufficient but on a lower end system it might be worth changing other settings to ensure that the game runs smoothly and that you don't get a black screen. in particular things like Volumetric clouds and Volumetric Fog are likely to create a large performance hit, and other settings such as the effects (though not the Exposure, Contrast and Saturation), tree and building density, and Terrain topology should also reduce the overall system load if reduced or turned off.

In general unless you've specifically done this yourself or your using craft/ fuels that someone else has made your not going to have file edited fuels and parts.

there are a few guides discussing this here on steam (namely this guide on Custom fuels by Asunder and this guide on Piston Engines and Props by BIG-HAM ) if you'd like to play with that side of things.

if you have done file editting or someone else's craft your using is, and your having black screen problems, make sure that:

- Values are reasonable ( minimum 31 rpm for guns, not too many zeros in fuel positive mass etc)

- All values are an accepted type (if it can only take a whole integer (such as 5) do not give it a float (such as 5.5) or a string)), this is more likely to affect whether a part/ fuel will load correctly.

if your not sure what your doing with part editing it may be best to leave it alone for the time being, or ask for help.