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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, ...
Robin Bennett's user avatar
20 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 ...
Kralc's user avatar
  • 6,036
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 ...
Kenn Sebesta's user avatar
  • 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 ...
Krish's user avatar
  • 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. ...
Drones and Whatnot's user avatar
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 ...
Mark's user avatar
  • 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. ...
Drones and Whatnot's user avatar
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 (...
Kralc's user avatar
  • 6,036
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 ...
ifconfig's user avatar
  • 6,008
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. ...
Drones and Whatnot's user avatar
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 ...
Kenn Sebesta's user avatar
  • 1,892
9 votes
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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 ...
Nikita Pedorich's user avatar
8 votes
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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 ...
QuadMcFly's user avatar
  • 1,200
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 ...
Kralc's user avatar
  • 6,036
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 ...
Robin Bennett's user avatar
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 ...
Jim's user avatar
  • 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 ...
Drones and Whatnot's user avatar
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 ...
Hannes Hultergård's user avatar
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 ...
ifconfig's user avatar
  • 6,008
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 ...
Kralc's user avatar
  • 6,036
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 ...
ifconfig's user avatar
  • 6,008
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 ...
ifconfig's user avatar
  • 6,008
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 ...
Ben Wilson's user avatar
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 ...
Flyback FPV's user avatar
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 ...
FunHog.me's user avatar
  • 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 ...
Ben Wilson's user avatar
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 ...
Carpe Canem's user avatar
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
user172's user avatar
  • 66

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