Flight Plan: How to Produce Professional Aerial Video, Part 1

Anatomy of a Multi-Rotor Copter

Your multi-rotor copter will no doubt be one of the most, if not the most sophisticated piece of equipment you have at your disposal as a video producer. It is essentially a flying laptop computer. '

Every copter has at least an airframe, a flight controller, a power source and some sort of power distribution, electronic speed controls, electric motors, and a radio transmitter and receiver used by the pilot to send control inputs.

The flight controller contains the primary processor and sensors that are necessary for stable flight. These tiny electronic sensors, known as gyros and accelerometers, send information to the flight control software to determine the position and to compensate for external influences such as wind. Control inputs from the pilot in combination with the information from these sensors result in commanded voltage signals being sent to the individual ESCs (Electronic Speed Controls).

These ESCs are, in fact, tiny computers themselves that determine how much voltage is to be sent to the individual motors thus determining the rotation speed of the propeller.

The copter maintains controlled flight through this constant cycle of information-updating. There will always be the same amount of ESCs as there are motors. Half of the motors on your copter will have clockwise rotating propellers, while the other half will have counter-clockwise propellers. When replacing a propeller it’s important to always make certain you replace it with a like kind propeller that is designed to rotate in the proper direction. Many copter setups will incorporate a GPS and navigation unit that is capable of offering enhanced auto-flight features such as position hold, altitude hold, auto return to home, auto takeoff, and landing and waypoint flight. While these auto features are impressive, they are no substitute for developing the proper flying skills and maintaining proficiency.

Let’s take a closer look now at some of the individual components of sUASes, revealing some important information that might not be readily identifiable.

Airframe

There are many different multi-copter frame types available. Some are barebones DIY kits, while others are marketed as Almost Ready to Fly (ARF) or Ready To Fly (RTF). Most are made from fiberglass and carbon fiber-cut tubing and plate materials. Many of the consumer-grade copters (such as the Phantom) are made from injection-molded plastic and/or aluminum.

It’s important to understand that each type of construction material has its advantages as well as its disadvantages. Molded plastic parts can be very proprietary and require a complete body replacement, while the CF tube and plate construction will offer you the ability to fly heavier payloads with component-level replacement in many cases.

Be forewarned that the term “Ready to Fly” is really a misnomer--even so-called RTF units will almost always require some sort of preparation before you are actually ready to fly. For the beginner, the DJI Phantom series provides, in my opinion, one of the most painless out of the box “ready to fly” experiences available with fairly sophisticated camera gimbal technology designed to be used in conjunction with the GoPro camera.

Flight Controller

There are a number of flight controllers on the market, some more user-friendly than others, with each offering many of the same features. For instance, the NAZA flight controller is the heart of the Phantom. DJI has created a relatively simple flight control user interface for the NAZA that does not require a tremendous “geek” factor to understand and manipulate. It is this simplified approach that has made the Phantom a favorite among newbies. Ironically, it is this same simplicity that has created the illusion that anyone can safely operate a multi-rotor copter without much effort or proficiency. Nothing could be further from the truth.

At the time I am writing this article series, the NAZA is, arguably, the flight control of choice for the novice and user who wish to minimize the amount of tinkering. You will be advised to pay close attention to the guidance provided in the 40-page user manual as well as the wiki online. (This is true for all flight controllers.) Most flight controllers will offer you several different flight control modes, each offering a higher level of automation. The manual mode of flight refers to flying your copter without the aid of the GPS and compass. While this can be a very challenging and difficult mode to operate in, even for the most proficient pilot, your flying experience in other modes will be enhanced by mastering flight in the manual mode.

The next mode, manual/full auto mode, is somewhat of a hybrid, as the name suggests. Your copter offers you an enhanced amount of attitude stability in this mode, providing a more comfortable sense of control. This is often used when the pilot would like to have a bit more control response than that offered in full auto. The GPS/full auto mode provides for position hold, altitude hold, and a slew of automated features that lend themselves to reducing the pilot workload, thus allowing attention to be diverted to shot composition and video feeds. Clearly the full auto mode (or some of the features of auto) is the mode of choice for most aerial work. Be advised, however, that a number of variables that can compromise the reliability of this mode of flight resulting in what appears to be a loss of control at times--thus the need to be able to fly in the first place without the aid of automation.

DJI flight controllers are known for their relative simplicity, but there are limits to just how far the software will allow you to make changes and add features. On the other end of the spectrum would be the Mikrokopter flight controller, which has become the gold standard from which others seem to be measured. Mikrokopter is known for the vast amount of control it provides through the software interface that enables you to take advantage of many features that will enhance your aerial cinema/photo capabilities. Your mileage may vary, depending on how you balance simplicity with performance.

It’s important to note that all of these electronics are “hobby” grade. I am not aware of any certification studies that would assure protection from RFI (radio frequency interference) sources. This translates once again to making certain you have the skill to fly without relying on the “gee whiz” features.

Battery Technology

Advances in battery technology have contributed to the rapid proliferation of electric-powered aircraft. The Lithium Polymer (LiPo) battery is the standard power source for multi-copters. LiPo batteries are lightweight and have the ability to be made into just about any size and shape. They are capable of high-voltage capacities with high discharge abilities capable of meeting the demanding power requirements of the multi-copter. These batteries can be expensive, and if not cared for properly, will not last very long.

Because of the volatile nature of the electrolyte they use, LiPo batteries can catch fire or explode. Proper care (as outlined in manufacturer’s information) is paramount to prolonging the lifespan of your LiPo as well as preventing your LiPo from deteriorating into a dangerous state that could lead to a fire. A simple google search for LiPo battery fires will reveal a number of unfortunate events that could have been prevented with a dose of common sense once you are aware of the volatility.

Note that discharging the LiPo below a value of 3.3v/cell will cause damage. Using a high-quality LiPo charger with cell balancing is a must as overcharging will certainly result in a fire or explosion.

LiPo components and specifications might prove a bit perplexing if you’re not accustom to the nomenclature. Essentially, each LiPo is comprised of individual cells. The letter “s” is used to designate cell. So a “3s” battery would be a 3-cell battery. Each cell in a LiPo has a nominal charged value of 3.7v, so a 3s battery would have a total voltage of 11.1 volts. Likewise, a 4s would be 14.8v, a 5s would be 18.5v, and a 6s would be 22.2v. It’s not unusual for a fully charged LiPo to have a slightly higher voltage value than what is listed on the battery. For example. 3s at 12.5v, 4s at 16.7v, and so on.

Most copters that are carrying a GoPro-sized camera will use 3s or 4s battery, while those carrying heavier weights will typically use 4s–6s sized batteries. The discharge rate of the battery is listed as a “c” value and can lead to a rather lengthy and technical discussion. Until you develop a deeper understanding of electrics and batteries, my advice is to use the batteries recommended by the manufacturer. A typical LiPo for a small quad-copter might read like this: 3s 25c or 4s 30c.

To ensure that your LiPo lasts as long as possible, be certain to reference the proper charging, discharging, and storage requirements and techniques recommended by the manufacturer.