Is it possible to hijack a quadcopter? Is it possible to hijack a quadcopter?
Like an attacker would jam the controller's signals and send his/her own signal to controll the drone. If so, what would be the technical steps?

Is it possible to hijack a quadcopter?

A)Yes
B)No

If so, what would be the technical steps?

Find a flying drone. Intercept the communication. If encrypted go and get a quantum computer before they switch to quantum encryption.
I will not detail the step-by-step process to hijack a quadcopter. It's already on the internet. If you didn't find it yet, you didn't ask yourself the right questions.


DJI F450 ESC calibration fail everyone. I am building a DJI F450 clone. I've got everything attached except for the propellers. The Pixhawk connects to my mission planner via USB. The remote controller is paired with the drone. Now I need to calibrate my ESB. Unfortunately, this is not working. The drone seems not to be going into calibration mode. It just blinks yellow and beeps.
Here is a video of the issue: https://youtu.be/t6_HZAf62zw
Potential problems and fixes I've tried:

PWM vs PPM on the remote. I've tried it both ways, with no luck.

Power connection is backwards. In the tutorial I'm following, the connections seem to be a bit different from my hardware. I've got a female XT60 on my shield, a male XT60 on the battery, a male XT60 on the "in" side of my power board and a female on the "out" side (the one which also has the data cable coming out of it.) The only way I can plug this thing together is to plug the battery into the "out" side of the power board and the shield into the "in" side, as seen in the video above. To test this hypothesis, I made some female-female and male-male jumper cables and tried to connect things the way they are on the tutorial...but no luck, same result.

I have used the FS-i6, it was my first radio. The throttle is generally on the left, and it is generally mode 2. In your case, it doesn't appear to be the case. So it might be useful to check in the transmitter settings if you have channel assigned correctly.
You can always see the signals sent to the FC in the Mission planner Setup tap under RC calibration. Ensure throttle signal moves as you desire.
From what I can see, there is probably some issue with the RC link and the signal being sent to the Pixhawk.

what don't you make a panel board within each propellers.
then give exact amount for each wing = Esb via pixhawk programme.
how to control?
1.try braille code instead of single unit code.
i would make the battery at the centre.wired it along the route toward propellers.why? : coz batteries and ppm in the centre will effect the signal divide for each propellers.
that why u dont get syno caliph for each propellers.


Why are quadcopters inherently unstable? I have heard it mentioned that quadcopters are inherently unstable and only become stable due to control. What does inherently unstable mean in this context, and 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, there's more weight on one side of the car than the other but the car doesn't flip over. The springs on that side of the car compress and push harder on the wheels. The tyres push harder on the ground and the ground pushes back. The extra force from the ground exactly balances the extra weight and (after possibly bouncing for a moment) the car stops moving.

In an unstable system, say a broom balanced vertically, once it moves from the perfect balance point gravity will pull it further away and it accelerates.

For a quadcopter, there is no force that returns it to its original location, holding it horizontal, or even preventing a gradual roll.

Even if the thrust from each motor was exactly the same, and the weight was perfectly balanced, it's very unlikely to be perfectly stationary. If there's even the slight amount of pitch or roll, the angle from horizontal will gradually increase. As the angle increases, the sideways thrust increases and the drone accelerates.

So the roll rate is constant, the angle and acceleration increase linearly, the horizontal speed increases faster as the acceleration builds, and the distance from the starting position increases even faster as the speed builds. To the pilot, it looks like the drone is accelerating away from its original position much like the broom falling over.

To a systems engineer, the rotation of the drone is neutrally stable - there are no forces increasing or decreasing the rotation rate. However the speed and position are unstable - once it starts moving, it accelerates.

I should mention that there are second-order (i.e. relatively minor) forces too. If you had a large fin on top of the drone, aerodynamic drag on the fin would return the drone to upright as the speed builds and limit the maximum speed - in practice this isn't useful as it doesn't return the drone to its original position.

It’s not entirely correct, that quadcopters are unstable. Most commercial copters have a center of gravity way below the Propeller plane and thus are actually stable. In contrast to that you want certain aircrafts to be instabile for better agility. For example some jet fighters are unstable and need electronic stabilization even for normal forward flight.


Difference between T700 carbon frames and 3k carbon frames? I have heard that iflight's Green Hornet uses T700 carbon instead of 3k carbon. What difference does the new T700 carbon make?

First of all, the 300 or 700 is the grade value of carbon fiber and generally, a higher grade means more strength and better performance. The main differences between T300 (3k) carbon and T700 carbon are that T700 carbon has almost 40% more tensile strength than 3k carbon, T700 carbon is slightly denser (and thus heavier for the same volume of carbon), T700 carbon fiber has a higher carbon content and a lower nitrogen content, and T700 carbon fiber is smoother looking while T300 carbon looks more bark-like.

So, overall, T700 carbon is better for making a drone frame because it is significantly stronger with only a small increase in weight.

T700 and 3K are different indication.
T700 indicate the strength of the frame (higher strength/weight ratio) 3k usually means the number filaments on the surface layer.
You can have a carbon fiber sheet T700 3K


Why do most drones have upward facing motors? Most freestyle quadcopters I have seen are specifically designed to fly with the motors facing upward and have the arms of the drone underneath the propellers like this:

As you can see in the picture ^ , the arms of the drone are fairly wide (as is common in lots of quadcopters of this type) and it seems to me that the arms would block a portion of the air coming from the props. I imagine that having the arms like this would reduce efficiency or top speed and maybe cause some amount of prop wash.

There are significantly less quadcopters which have the motors mounted under the arms like this:

(and almost all of them are home-made projects like this one which modified an existing frame to work upside down)

What I am wondering is, why are so many manufacturers and hobbyists making so many drones with upward-facing motors as it seems that downward-facing motors would be better in many ways? What are the advantages and disadvantages of upward-facing motors vs downward-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 is spinning through the wake of the fuselage - this results in 'lumpy' air, causing vibrations. I don't have exact figures, but I've heard anecdotally that this can be a 10 to 15% drop for fixed-wing designs and the exact fuselage configuration will make a difference!

1: Pushers are often defined as '[motor/engine] shaft under compression'; which seems to apply to the 'upside down' motor configuration.

They are more stable since the drone is suspended from a higher point.  If the drone tilts, the side that gets lowered has its propellers move outwards, giving them more leverage while the side that gets raised has its propellers move inwards, giving them less leverage.  That makes the drone right itself again.  The lower the propellers are, the less effective this self-stabilising system becomes.


Isn’t flying FPV drones illegal accoding to FAA rules? I understand there is First Person View (FPV) drone flying which involves putting on a headset and controlling the drone from the live camera feed,

The FAA Rules For Unmanned Aircraft Part 107 state:

  Visual line-of-sight (VLOS) only; the unmanned aircraft must remain within VLOS of the remote pilot in command and the
  person manipulating the flight controls of the small UAS.

If that is true, then surely FPV flying is illegal as you don’t maintain a visual line of sight with the aircraft?

FPV is not actually illegal because that document also states:

  Part 107 does not apply to model aircraft that satisfy all of
  the criteria specified in section 336 of Public Law 112-95.

and the criteria specified in section 336 of Public Law 112-95 is:

  (1) the aircraft is flown strictly for hobby or recreational use;

  (2) the aircraft is operated in accordance with a community-based set
  of safety guidelines and within the programming of a nationwide
  community-based organization;

  (3) the aircraft is limited to not more than 55 pounds unless
  otherwise certified through a design, construction, inspection, flight
  test, and operational safety program administered by a community-based
  organization;

  (4) the aircraft is operated in a manner that does not interfere with
  and gives way to any manned aircraft; and

  (5) when flown within 5 miles of an airport, the operator of the
  aircraft provides the airport operator and the airport air traffic
  control tower (when an air traffic facility is located at the airport)
  with prior notice of the operation (model aircraft operators flying
  from a permanent location within 5 miles of an airport should
  establish a mutually-agreed upon operating procedure with the airport
  operator and the airport air traffic control tower (when an air
  traffic facility is located at the airport)).

This is essentially saying that if it is a recreational drone, follows community guidelines, is not more than 55lbs, doesn't interfere with manned aircraft, and notice is given to airports before flying within 5 miles of them, that FPV is perfectly Legal

No body mentions the FCC license requirement for the camera transmitter on the Drone used to provide FPV to the pilot. That transmitter requires an FCC license!!!!