Can drones/uav's fly over international waters without FAA's regulations?

My conclusion is yes, the FAA regulations do not directly apply. However ICAO takes over and the FAA is in charge of enforcing ICAO rules. Thus, while you can fly without FAA jurisdiction, High Seas Airspace is not a Wild West where anything goes.

The FAA remains in charge of all US civil aircraft even in High Seas Airspace:

Sec. 91.703 - Operations of civil aircraft of U.S. registry outside of the United States.
Each person operating a civil aircraft of U.S. registry outside of the United States shall--
(1) When over the high seas, comply with annex 2 (Rules of the Air) to the Convention on International Civil Aviation and with Secs. 91.117(c), 91.127, 91.129, and 91.131;

Note that all US drones are required to be registered with the US, so they would fall under this clause.
The upshot is that ICAO regulations are in force in international waters. A circular can be found here: https://www.icao.int/Meetings/UAS/Documents/Circular%20328_en.pdf. It describes required BVLOS navigation aids.

RADIO NAVIGATION AIDS AND AIRBORNE NAVIGATION EQUIPMENT
6.26 As a general statement, all aircraft, whether manned or unmanned, must meet the navigation performance requirements for the specific airspace in which they will operate.
6.27 RPA that utilize VLOS as the basis for navigation would not require an on-board means for determining position or the ability to fly an instrument approach. Operations of these aircraft are usually conducted under VMC to ensure the remote pilot can maintain continuous and direct visual observation of the RPA and its surrounding environment.
6.28 RPA that traverse several airspace volumes may operate for the most part under IFR. Such RPA will have to meet the communications, navigation, and surveillance requirements and have an appropriate aircraft operational certification associated with the airspace.
6.29 In cases where small RPA have a requirement to fly beyond VLOS, they will need a means to meet navigation capabilities for the airspace within which they are operating. This could involve an alternate means of achieving the navigation performance.

In addition,

LICENSING AND TRAINING FOR PILOTS AND OTHER MEMBERS OF THE REMOTE CREW
7.8 Remote pilots and other members of the remote crew shall be trained and licensed in accordance with Annex 1.
7.9 Licensing and training requirements will be developed similar to those for manned aviation and will include both the aeronautical knowledge and operational components. Specific adjustments may be needed considering the particular and unique nature and characteristics of the remote pilot station environment and RPA applications (from both a technical and flight operations perspective, e.g. VLOS or beyond VLOS) as well as aircraft type (e.g. aeroplane, helicopter). In that context, qualifications for certain categories of remote crew (e.g. VLOS helicopter) may be  significantly different from those pertaining to the traditional qualifications pertaining to manned aviation.
7.10 On the basis of the foregoing, current and previous notional designations for personnel piloting RPA will need to be replaced with applicable terms as contained in Annex 1, appropriately modified to indicate their position being external to the aircraft, such as “remote pilot”, “remote navigator” and/or “remote engineer”, each of which is a member of the remote crew. A new crew position unique to some VLOS operations is “RPA observer”, an individual who, by visual observation of the RPA, assists the remote pilot in the safe conduct of the flight. Additional crew positions unique  to remote pilot station/RPA operations may be identified over time. These new positions will need to be incorporated into Annex 1 for international standardization.


Binding DX5e (or any other hobby controller) to generic "toy" drone - protocol compatability

There are many different communication protocols used for radio controlled models and even for the same vendor the parts/versions are not always compatible. While most use the same chips to build their systems everybody uses a different protocol and so the different parts do not understand each other.
Most of the companies do not release official information how the protocols works and are not interested to make their products compatible with a competing vendor.
So if a drone claims to be DSM2 compatible there are two options: a genuine spektrum receiver is used or somebody found out how the protocol is working by reverse engineering the system.
Most cheap drones do not use genuine receivers since the product costs less than the receiver alone. The drone you linked does not state DSM2 compatiblity so I'd say the problem is that you have no compatible tx. But information on the product page is not sufficient to tell what they are using.
You could try to find out what protocol the drone uses and check if the multiprotocol project supports it: https://github.com/pascallanger/DIY-Multiprotocol-TX-Module/blob/master/Protocols_Details.md
But even in that case you would need to buy a multiprotocol module and make sure it works with your DX5e.


At what current should I charge a LiPo battery?

Charging Lithium batteries is a far more delicate process than discharging them because of the complex chemical processes involved. Batteries that are rated for tens of "c"s of discharge rate are usually only rated for 1-2 "c"s of charging rate. Standard charging rates are 1c for regular speed and 2c for fast charging, with 2c damaging the battery more.

C-ratings are an artificial marketing term that doesn't really help very much without being converted using this formula: Charging Current (amps) = C-rating * Battery Capacity (amp-hours) where one amp-hour (Ah) is equal to 1000 milli-amp-hours (mAh).

So, for example:

1500 mAh battery charging @ 1c = 1.5 A charging current
2000 mAh battery charging @ 1c = 2.0 A charging current
2000 mAh battery charging @ 2c = 4.0 A charging current
2000 mAh battery charging @ 0.5c = 1.0 A charging current

Charging at higher currents (higher c-ratings) is more damaging to the battery's cells and is more likely to cause complications like fires and explosions while charging. The opposite is true for charging at lower currents. It is hardly ever recommended to charge at more than 2c, and staying as close as possible to 1c is always recommended for safety and battery longevity.


How hot is too hot when it comes to multirotor motors?

Temperature is a killer of motors over time. If motors are exposed to prolonged heat, the magnets in the rotor lose their magnetic field strength over time and consequently reduce the lifespan of the motor.

Generally, a well-tuned drone should not have extremely hot motors after flying (with a few exceptions). It depends on the motor, but you should avoid raising the motor’s temperature past 170°F; any hotter, and you run the risk of damaging the rotor’s magnets and decreasing performance and longevity.

https://dronenodes.com/drone-motors-brushless-guide/

https://www.rcgroups.com/forums/showthread.php?1329288-Normal-brushless-motor-temperature-range


S800 Reptile Matek F411 auto launch question

A possible explanation is the flight controller compensating for propeller torque.
When a propeller spins, there is a counter-rotation applied to the aircraft (Newton's third law.) Assuming your propeller spins clockwise (viewed from behind the aircraft) this would be corrected in the air with a small amount of right roll - which is what is shown in your video. The amount of surface deflection will vary by airframe, so it is hard to judge from a  video if the amount of movement is correct.
More info: http://ffden-2.phys.uaf.edu/webproj/211_fall_2016/Collin_Lasley/collin_lasley/torque.htm


Many people choose to use Lithium Ion batteries on long range builds.

They have a very large capacity and I have seen them give in excess of 20 minutes of flight on a quadcopter.

The reason that they aren’t often used for other purposes is that their current output is less than LiPo batteries.

This means that whilst they are good for long range flight, they lack the power for aerobatics and racing.


How can I know the laws of a specific country regarding drones?

There are a large number of websites which collate drone rules in different countries; to list a few:

Dronegenuity
UAV Coach
Drone Rush
UAV Systems International

However, due to the rapidly evolving nature of drone rules these could quickly become out of date - in fact, at time of writing, some of the sites already contain old (now incorrect) information. The safest option is to check the website of the country's aviation regulator before you travel.


Aside from quality control issues with the product, the only real way to destroy an ESC faster than the effects or normal wear and tear (minimal) is to mistreat it:

Using it with a voltage higher than its rating
Using it with a motor that's dramatically too large
Drawing more current than its rating

Frequently stalling the motor against tree branches or alike

Not adequately cooling the MOSFET transistors when used in high-power applications

I will say, there's something to be said for having all of the ESCs on a model be the same make and model. This would minimize the risk of asymmetric behaviors between the ESCs in-flight.


What are the advantages or buying a small drone vs a larger drone?

The first thing you should consider is what you have room for. A larger drone will normally need more space to fly and can cause more damage if crashed. I would recommend a small drone if you are just starting out or if you can only fly indoors, in which case you would want a tiny whoop.

The next thing I would think about is cost. A larger drone will be much more expensive for the drone itself, the propellers, the parts (frame, electronics, etc.), and especially batteries. While a larger drone may have slightly longer flight times, one battery for a large drone might cost 10 times as much as a battery for a small drone. So, with smaller drones, you can get more flight time per dollar of battery. (you can buy 4-6 small batteries for the price of one large battery and get a lot more flight time for the same amount of money). So, if you're on a budget, I definitely recommend a small drone. It's also worth mentioning that larger drones usually use batteries with more cells so they can be more dangerous if they catch on fire or puff up.

Next, there is flight performance. Generally, it is true that a smaller drone is more nimble than a large drone, although Larger drones are usually capable of much higher top-speeds. I must say though, after having lots of experience with different drones I much prefer the performance of a large, powerful drone to a small drone because small drones often suffer from lots of battery sag due to the lower battery voltages and so they cannot sustain high throttle as well. Also, a larger drone can carry a GoPro or other camera with ease.

So in the end:

Get a small drone if: you only have a small area, you only have a little bit of money, you are very worried about damaging something, you want a lot of flight time for less money, or if you just don't want a big drone.
Get a larger drone if: You have enough space and money, you want high performance/top speed, you want something that can lift a GoPro/camera/payload, or if you just want a larger drone.


Why can't quadcopters handle failure of one rotor?

I saw a TED talk from a guy who had written quadcopter software to handle losing one motor. Perhaps you can find it.
With nothing to counter the unbalanced torque, the quad spun in yaw quite rapidly. Most software would attempt to counter this by increasing power on the motor opposite the dead motor, and decreasing power to the other two. Instead they allowed the quad to yaw and concentrated on maintaining stability.
Although the unbalanced lift would tend to tip the quad over, it would tip the quad back a fraction of a second later when it had spun 180 degrees. I guess the software also had to take account of gyroscopic effects, and the time taken to spin a motor up or down.
The demonstration was indoors, so I couldn't tell if the quad was capable of 'forward' flight, but it hovered and descended under control.
You may well ask why this isn't part of common quadcopter firmware. I can only speculate that it's because:

It's rare to loose a motor in flight (failures are usually a result of crashes)
The algorithm for 3 motor flight isn't public domain (maybe the above team sold it to the military or something)
Landing while spinning rapidly does almost as much damage as crashing.
People who care about redundancy just add more motors.


Possible to use Eachine E160 with Futaba T6EX transmitter/receiver set?

The product page of the helicopter states it is compatible with: FUTABA S-FHSS, expandable satellite receiver, and supports DSMX DSM2 PPM S-SUS
Your TX/RX are from Futaba but from the older FASST system so S-FHSS is no option. DSMX and DSM2 are from Spektrum and not compatible with Futaba.
There are two options remaining: PPM and S-BUS. Both do basically the same: send the signal of all channels via one cable. As far as I can tell your TX does not support either and only allows to send one channel via one output.
S-Bus is also from Futaba so you could try to find a FASST receiver that supports S-Bus output. Frsky also has compatible FASST receivers with PPM output (like FrSKY TFR4-B). Then you could solder a connector from the outputs from the RX to the E160 motherboard. The yellow cable in the picture is the S-BUS/PPM wire, red is 5V and black is ground. To find the correct matching pins on the RX I'd look in the manual. Usually you have some labels on the case.
A PPM enconder is also an option. This is a small board that encodes the servo signals to a single ppm stream. The downside is that you still have many cabels between the encoder and the RX and you need space for an additional board.


FTDI drivers can be downloaded from the FTDI Website.
You should then be able to install the driver using "Update Driver -> Browse my computer for driver software" and selecting the folder containing the extracted files.


The maximum altitude is 3000m (about 9800 ft.)
(Note that this is relative to mean sea level, not the ground.)
Sources:

DJI Mavic Mini "Specs" page (under "Max Takeoff Altitude")
DJI Mavic Mini "FAQ" page (under "Propulsion" > "What is Mavic Mini's maximum service ceiling?")


Can you cancel an automatic landing triggered by a low battery on the Dji Mavic 2 Pro?

If you have more then enough battery, you can disable it as stated in the manual:

Low Battery RTH
Low Battery RTH is triggered when the Intelligent Flight Battery is depleted to the point that the safe return of the aircraft may be affected. Return home or land the aircraft immediately when prompted. DJI GO 4 displays a warning when the battery level is low. The aircraft will automatically return to the Home Point if no action is taken after a ten-second countdown. The user can cancel RTH by pressing the RTH button or Flight Pause button on the remote controller.

Note: this function is intimated specifically so the drone has enough battery to come back to you, so if you cancel it, make sure you know what you’re doing.
The function can not be overridden if the drone only has enough battery to descend from its current altitude:

The aircraft will land automatically if the current battery level can only support the aircraft long enough to descend from its current altitude. The user cannot cancel the auto-landing but can use the remote controller to alter the aircraft’s orientation during the landing process.


How to recognize damaged brushless outrunner motors?

There are many signs that a brushless motor is broken or getting worn out. Something that can happen to motors that have been used for a long time is their bearings wear out. If you notice that the bell of a motor feels loose or the motor is excessively noisy or has a grinding sound, it is likely worn-out bearings. You can either replace the bearings or buy a new motor.

Another thing that happens is the magnets can demagnetize over time if the motors get hot. A way to know if this has happened is to run the motor with no load. If the RPMs are unusually high, the magnets are likely losing their strength. In this case, you need a new motor.


What is headless mode?
Headless mode is a specialized flying mode that is common in store-bought drones. It eliminates the need for focusing on the drone’s orientation and enables a much easier Line of Sight flying experience. This can make drone flying easier especially for beginners still learning how to control the flight path of the drone.
Whilst it may be useful for beginners to learn flying using this mode, it wouldn’t be too recommended. You can then get used to this mode and then have trouble unlearning it and learning how to fly the drone properly.
The only thing is that when you launch the drone, the front of the drone must be facing away from you to launch properly.
How does it work and how is it different to normal mode?
When you take off with the drone pointing forward, algorithms within the drone’s microcontroller will ensure that any directional changes are compensated. The drone will take instructions based on your current orientation as opposed to normal mode where the drone moves in regards to the drone's orientation, no matter where you are regarding the drone.
For example, if you are in normal mode and the drone is facing toward you, and you press left, the drone will go right (as left in the way it’s facing means right in the way you are facing) whereas, if you are in headless mode, the drone will move left in the direction you are facing the drone.
This diagram illustrates how normal mode is different from headless mode:

(image source)
This is another diagram showing a more detailed visual of how the drone will move differently in normal mode compared to headless mode:

(image source)
How do I enable it?
This will vary from drone-to-drone so one specific answer cannot be given. If your drone has it built-in (which most do), there should be something in the instruction manual saying how to enable it. Most likely it’s a button that needs to be pressed on your controller.


Betaflight with Mamba F405 MK2 stack 40A ESC's and XING-E 2207 motors problem

If you have airmode enabled as a feature then the motors will spin on arm no matter what other settings you have.
It sounds to me like you may have accidentally set your ESC's to bi-directional in BL-heli configurator which is NOT the same as bi-directional DSHOT protocol.  Check out this video for explanation on the difference : https://www.youtube.com/watch?v=DXfAnCLr3q0&t=65s


What are the specs of the DJI Mavic 2 Pro motors?

The most information I could find and definitely link back to the Mavic 2 is the following from the EU CE testing report:

1.5.1   TABLE: List of critical components
╔═════════════╦═══════════════════╦═══════════════╦═══════════════════╗
║ Object/part ║ Manufacturer/     ║ Type/model    ║ Technical data    ║
║ No.         ║ trademark         ║               ║                   ║
╠═════════════╬═══════════════════╬═══════════════╬═══════════════════╣
~             ~                   ~               ~                   ~
╠═════════════╬═══════════════════╬═══════════════╬═══════════════════╣
║ Motor of    ║ DZ DJI Technology ║ WM240-2009    ║ 14,8 V, 0,5 A     ║
║ airscrew    ║ Co Ltd            ║               ║ max. 1040 rpm/V   ║
╚═════════════╩═══════════════════╩═══════════════╩═══════════════════╝


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 control software such as FlightOne and Kiss have different defaults.

Default Direction

Reversed Direction

If you are running props out, make sure you flip the switch on the Betaflight configuration tab to adjust that, otherwise your first flight will be VERY short and very fast!

Note that this switch does not change the actual direction of the motors! It's just a way for you to tell betaflight which way they're actually spinning. To check that the displayed and actual directions match, do the following:

In Betaflight go to the motors tab, read the warnings, then plug in your battery and click the enable motors switch. Run up the motors one at a time from their slider and ensure they match the direction and position of the charts above.

If you don't have access to a computer, alternatively you can simply arm your quad without props on and check the direction that way. Make sure you don't raise the throttle though, or airmode might kick in and you'll have the motors wind up due to I term buildup from the PID controller. This isn't an issue from the motors tab, so choose that option preferentially if you can.

In both cases, you can either brush the flat of your finger lightly against the motor or put a piece of tape on the shaft before you run them up. Make note of any motors that are out of order or not spinning the direction you want.

Changing Direction

There are two ways you can fix the motor direction. One relies on a soldering iron or bullet connectors, the second relies on using software to change the direction.

Method One - Physically Change the Wires.

On the motors that are not spinning the correct direction simply desolder and switch pads on the ESC of any two of the motor wires. This will swap the direction of that motor.

Method Two - Betaflight and BLHeliSuite

If you already have your computer up, you can use BLHeliSuite to change the motor direction. The first thing you need to do is identify what type of ESCs you have. If you have BLHeli_S ESCs you'll need the Suite labeled 16.XX from the BLHeli Google Share. If you're using BLHeli 32 ESCs, download the 32.XX Suite.

Once you've downloaded the appropriate suite, make sure the Betaflight configurator is disconnected from your flight controller, extract the contents of the zip file, and run the executable.
Make sure you select the E (Cleanflight) interface from the interface dropdown list.

Select the correct COM port from the dropdown list (the same as Betaflight) and click connect.

Click the "Check" button on the right, then you'll see a confirmation of your ESCs and some summary information.

At the bottom of the screen, right-click on the ESC number that needs to be reversed, then go to the "Motor Direction" slider and change the direction.

Click "Write Setup".

Repeat for any other ESCs needed and then click "Disconnect".

Once you've finished, go back and repeat the check process once again until everything is correct! That's all there is to it!

Put the propellers on correct

Finally, when you go flying, ensure that you put your propellers on according to the direction of your motors. Most flip outs are caused not by the motor spinning in the wrong direction, but by a right propeller being mistakenly put on a left motor or vice-versa!

If you're new to the hobby, it might help to carry a sheet of paper with you with the directions printed on it, or color-code your motors and props with a marker so you can't go wrong.


Isn’t flying FPV drones illegal accoding to FAA rules?

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


How do I pick my gear when getting started with FPV multirotors?

There are quite a few aspects of FPV, so a I’ll give a summary here. I’ll try to be concise so if any extra info is required or wanted, please let me know.

The first thing to look at when you’re flying FPV is the kind of aircraft, all the way up from a small Tiny Whoop to an X class (please not for beginners though!). In general, the larger props tend to give more flight time up to a point - it’s generally agreed that 7 inch props should be used for long-range because of this.

Video Transmitters

Another important thing to look at on your aircraft (excluding the advantages of different flight controllers etc, which I would love to talk about but would end up writing a massive wall of text) is the video transmitter, or VTX.

When looking at these, the first important thing is to check your local laws about what frequencies and transmitter powers you can use. Once you know that, keep in mind that more power tends to equal more range in open spaces, but can lead to more interference in places like abandoned buildings.

Another important fact to remember about the VTX is that you should manually select the channel on your VTX AND goggles as auto-scan sometimes picks the wrong channel and will cut out after a few feet. Also, never turn on your VTX without an antenna installed, or you risk damaging it. It is perfectly normal for your VTX to get warm on the bench when there is no airflow.

Finally, you will see people talking about Smart Audio - this is just a way to control the settings on the VTX from your transmitter.

Other hardware

Motors are very important. If possible, get brushless motors as they last longer and are more powerful.

When getting your first FPV quad, check out how repairable it is. It’s almost certain that at some point you will need to repair or modify it, so it’s good to know that before getting the quad.

Check what voltage your quad is designed to run at. If you have too little voltage, your quad will be underpowered, but if you have too great a voltage your quad may burst into flames (possibly a slight exaggeration to get a point across).

The ESC or Electronic Speed Controller is what tells your motor what to do, and you need one for each motor. If possible, get BLHeli_32 ESCs as they are more modern and natively support bidirectional Dshot so you can enable something called ‘RPM filtering).

When looking at flight controllers, the higher the value of X is in the naming format FX, the better. At the time of writing, F4 is the most common and F7 is becoming more popular. As I said, I won’t go into too much detail, but the higher the number, the more processes the CPU can complete per second so the more filtering and other leaguers you can have.

Goggles

There are two main types of goggles - box goggles and slimline goggles.

In general, slimline goggles are more expensive, lighter, arguably more comfortable and tend to have a narrower field of view and better quality displays. Box goggles, on the other hand, have massive screens and tend to be cheaper, however they are larger and heavier so may be less comfortable.

If possible, get goggles with a diversity receiver (or if you get Fat Sharks of Orqas, get a diversity receiver module like Rapidfire). This has two receivers and can either merge the two signals into one (cleaner) signal, or just automatically pick whichever signal is the strongest.

RC Transmitters

The most commonly used protocol at the moment is FrSky's D16, with Crossfire becoming more and more popular not only for long-range, but just for general flying.

When picking your transmitter, look for Hall gimbals, which use the Hall Effect to measure movement instead of potentiometers, so last longer and (apparently- I haven t used them) feel nicer.

Much of your transmitter will be personal preference, about the ergonomics and whether you pinch, thumb or hybrid-pinch.

Batteries

For anything more than 1S, you need a balance charger to make sure all the cells have the same voltage. To find the nominal voltage of a battery, multiply the number of cells by 3.7, as the nominal voltage of a single cell is 3.7.

I will leave you with this - don’t leave charging batteries unattended - LiPos are very dangerous if mistreated and can burst into flames if damaged or overcharged.


Does the sharpness of a propeller blade affect efficiency?

Rounded leading edges are better for subsonic aerofoils.

Props and wings have to work at a range of angles of attack. The airflow has to split to pass either side of the aerofoil, and a rounded leading edge allows the separation point to move smoothly. Sharp leading edges cause a lot of drag at extreme angles of attack when air has to flow across the sharp edge.

That said, the sharp edge on some props is just mould flash and can be sanded off with fine sand paper.

Sharp trailing edges are OK aerodynamically but easily damaged, and dings in thin plastic can cause drag, so there's a practical limit to the sharpness of a trailing edge.


Turtle Mode, Flip Over After Crash in Betaflight, is a mode that allows your drone to flip over if it is upside down by reversing the prop direction and spinning up very rapidly in order to lift a side of the drone so it flips to the upright position.

This is a manual process - the drone doesn't do this automatically when it flips over (you need to enable turtle mode after the crash, manipulate the sticks to flip the drone over, and disable turtle mode in order to resume flight).  It's beneficial because if your drone goes down 100' away, for example, you can put your drone in turtle mode and flip it back to the normal position, and resume flying.

There are some cases where turtle mode won't work, like when you land upside down in tall grass, the grass could bind the motors/props, preventing turtle mode from working effectively.


Why are larger propellers generally more efficient than smaller ones?

Thrust is proportional to the change in momentum of the air passing through the prop - i.e. how much the prop speeds it up.

The power required to do this is proportional to the kinetic energy of the air, which is proportional to speed squared. That 'squared' is the problem.

A smaller prop acts on less air, so it has to speed it up more to generate the same thrust. Half as much air moving twice as fast generates the same thrust, but takes twice as much power.

This explains why helicopters can hover relatively economically, propeller planes only if they're powerful aerobatic models, jets only if they're extremely powerful and carrying a minimum of weight, and no one uses rockets unless they have to.


Like you said in your answer, it does depend on the ESC... so you definitely want to look into the specifications for your particular components.  However, to be safe, a good rule of thumb suggested on this forum is that you want to be able to put your finger on it without discomfort for five seconds.  If your reflex is to withdraw after only 2 seconds, chances are you're running a significant risk of overheating it.

As to what happens if you exceed the temperature... it's not pretty.  Insulation on electric components starts to melt, resulting in shorts...  Overheating will typically result in a pretty instantaneous failure.

It's always a good idea to keep your ESC exposed to a constant airflow.  If you put it inside a closed compartment, ensure that you have some way that airflow is being sent through that compartment.


How can I learn to fly RC planes using a simulator?

I've enjoyed the Great Planes RealFlight simulator for a number of years. It has lasted well and I like the included transmitter controller. It is not free nor cheap, but it will save you a lot more in RC models that you can bring home from the flying field ready to fly again (i.e. it will save you many crashes).


Would I be able to program a smartphone app to control a smartphone-controlled drone?

This certainly seems doable. The SDK documentation is not very clear but basically it's a simple string command over UDP. So it looks like the drone creates a WiFi access point which you connect to with your phone and you have a dedicated IP address/port number to send commands to the drone.

There is a simple python application linked in their SDK document that shows the basics. And there is a github repository that also has a python program that shows how to get the video feed from the drone over the command API described in the SDK.

Given the SDK and the example projects in the github repository I think it would be a feasible project by someone with some Android development skills.