23
votes
Accepted
Why are quadcopters inherently unstable?
A stable system is one where there's a force that pushes the system back towards it's original state when the system is moved from its balance point.
For example, when the driver gets into a car, ...
- 7,428
21
votes
Why do most drones have upward facing motors?
One practical advantage is increased ground clearance, reducing the likelihood of a prop strike on landing or take-off.
Aerodynamically, a pusher1 design can be less efficient because the propeller ...
- 6,056
17
votes
Accepted
How does a quadcopter yaw?
Any vehicle yaws (i.e. turns) by having a net torque applied. What's interesting about a quadcopter is not just how it yaws, but how it yaws and doesn't roll, pitch, or climb at the same time.
To ...
- 1,892
17
votes
Why do most drones have upward facing motors?
Expanding on @Kralc's answer:
Here's a study (unfortunately behind a paywall) that I'm going to copy key parts of below:
The hexacopter was mounted on a load cell test stand, and data were collected ...
- 752
14
votes
New Prebuilt Drone flipping on takeoff
There are several things that can be causing this with different likelihoods.
The first thing to check is - are your propellers on correctly? It is an easy mistake to make and always worth a check.
...
- 4,422
14
votes
Accepted
Why did a quadcopter in vertical descent appear to lose thrust and descend rapidly?
It sounds like you've encountered what's called "vortex ring state", when a rotorcraft descends into its own wake -- essentially, a self-created downdraft.
There are two ways to escape from such a ...
- 686
14
votes
Accepted
Quadcopter return to home function not working
Having Googled the S49 drone, it appears that your drone uses ‘headless rth’.
This means that instead of using GPS, the drone goes into ‘headless mode’ then pitches backwards towards you.
...
- 4,422
12
votes
How does a quadcopter yaw?
The yaw effect created by the same effect that would cause a helicopter to spin if it didn't have a tail rotor.
On a multirotor, half the propellers spin clockwise (CW) and half counter-clockwise (...
- 6,056
12
votes
Accepted
Can I configure Betaflight in the field without using a laptop?
Yes, you actually can! There are a couple of options for the Betaflight firmware which are mostly plug and play.
OpenTX Lua Scripts
Radios running OpenTX can use scripts written in Lua to control ...
- 6,018
12
votes
Freshly built quadcopter/drone flips on takeoff
There are several things that can be causing this with different likelihoods.
The first thing to check is - are your propellers on correctly? It is an easy mistake to make and always worth a check.
...
- 4,422
10
votes
Accepted
How does frame stiffness affect a quadcopter?
Background
Stiffness, oscillation, and vibration damping are separate concepts but all somewhat relevant to the question. Each affects flight dynamics, and each is (somewhat) a function of material ...
- 1,892
9
votes
Accepted
Quadcopter getting hot after a flight
"Hot quadcopter" is a bit broad of a term, a lot of things can be hot in there.
Maybe it's the VTX, then it's normal, they can get hot up to 80C. You might want to use a heatsink though, depends on ...
- 610
8
votes
Accepted
What process should I use to ensure my motors are spinning the correct direction when using Betaflight
Checking Direction
In Betaflight you can have your motors spinning either props out or props in. The default is props in (towards the body of the quad from the front and back). Be aware other flight ...
- 1,210
8
votes
Accepted
Why do a quadcopter's opposite rotors spin in the same direction?
This design is to prevent unwanted yaw when moving, or vice-versa.
Consider the following two actions:
When a quadcopter yaws, it does so by creating a speed difference between the opposite-rotating ...
- 6,056
8
votes
What are the advantages and disadvantages of a "plus" and "cross" quadcopter configuration? Is one preferred over another?
According to this paper:
pitch and roll control authority is up to about 30% greater for the
cross-configuration since all four (as opposed to only two) rotors are
used.
However this is a bit ...
- 7,428
7
votes
Why did a quadcopter in vertical descent appear to lose thrust and descend rapidly?
If the battery was low enough, voltage sag during flight could be enough to cause the loss of thrust. When the quad has enough time to sit, the voltage may bounce back enough to take off for a brief ...
- 311
7
votes
Which settings in Betaflight allows me to do flips and rolls?
It’s called Airmode.
It keeps the motors in a constant idle state, even at zero throttle. This gives you pitch, roll and yaw authority even when you are upside down.
You can enable it in the ...
- 4,422
7
votes
Accepted
How to clean a drone?
I have found that the simplest and probably one of the safest ways is to use a compressor (alternatively a compressed air can will probably work), to lightly blow away the dirt. This works especially ...
- 2,664
7
votes
Accepted
How does a quadcopter flip without falling very much?
The trick is speed. The reason why multirotors don't lose (very much) altitude while performing quick mid-air aerobatics is because of the speed of the move and the skillful management of throttle by ...
- 6,018
7
votes
Accepted
why do drone frames have spaces and holes
A major consideration is weight reduction; if material can be removed without significantly reducing the strength of the item, this will result in an increased payload or flight duration. This is ...
- 6,056
6
votes
Accepted
What's the purpose of airmode and idle up?
Airmode and idle up both seek to increase a control authority and stability during ultra-low throttle moves.
In normal flight, when the pilot commands the multirotor to pitch or roll (cyclic), the ...
- 6,018
6
votes
Accepted
How does the center of gravity affect a quadcopter?
Altering the location of the CG (center of gravity) also changes the CM(center of mass) because the force of gravity acts roughly on the CM. Normally, the motor arms are equally sized so that all ...
- 6,018
6
votes
What are the benefits to different types of frame arrangements?
Unfortunately it really seems to be a personal preference thing.
I tried logging the same move on both pitch and roll on a stretched x frame to determine exactly how much difference there was and I ...
- 468
6
votes
Accepted
Finding a ready-to-fly Taranis compatible, Eachine compatible, S4 compatible under 200€ drone
I think the Cidora SL5-E is a very good choice. What you need to look for is the "BNF" suffix in the description which stands for "Bind and Fly". In that case a receiver is already ...
- 486
6
votes
What are the advantages and disadvantages of a "plus" and "cross" quadcopter configuration? Is one preferred over another?
Practically speaking, "plus" blocks the camera and has a different flight characteristic, especially when landing as you can drag a single arm if not "flat" and the chance of using ...
- 1,068
5
votes
How to clean a drone?
I've got a paintbrush in my flight kit which I use for removing chunks of mud/grass from my quads so I can keep flying on the day.
If they get really dirty, I use a toothbrush dipped in alcohol once ...
- 468
5
votes
New Prebuilt Drone flipping on takeoff
I've had this recently with 2 different BNF's. One I had the props on the wrong way! The other I needed to recalibrate the accelerometer. You can either use Betaflight to recall, or the stick commands ...
- 81
5
votes
Accepted
New Prebuilt Drone flipping on takeoff
Additionally to the options listed above, looking into whether or not:
You may have a reversed or upside down prop
Motor spinning wrong way
FC board orientation isn’t what it thinks it is
- 66
Only top scored, non community-wiki answers of a minimum length are eligible