Aerial Video Platform Comparison

At this point in time, almost all cinema quality remotely piloted aircraft are based on VTOL (vertical take off/landing) aircraft designs. The two most common are single main rotor and multirotor configurations. Both types have inherent strengths and weaknesses.

Safety

It is believed by some that multirotor designs are the safer of the two options when it comes to flying around talent. The thinking being that the lesser of two evils is to be injured by 8 high rpm steak knives versus 2 medium rpm swords. This is a debate that has no real purpose. Both designs must be treated with the same respect when flown near people and property. To carry an equivalent weight camera package, both would have similar total weight and so would carry the same kinetic energy upon impact. If the risk advantage goes to the multirotor, due to less rotating mass, then the advantage goes to the single rotor platform in the event of a drive power failure due to this designs ability to still be guided during autorotation. Once again, such comparisons are pointless and safety must come from - the experience of the operator, the maintenance practices for the equipment, and well thought out risk mitigation planning for every shot.

The rig in the video below weighs approximately 20 lbs. and lost control with considerable force.

Vibration and Stability

A very common question is - which design provides smoother, steadier images? First let's discuss vibration. Further, lets define vibration as movement at fixed or semi periodic intervals (aka frequencies). In general it is a much simpler task to balance motors and fixed pitch propellers than drive shafts, gears and variable pitch rotors. This, more than any other reason, is why there are so few companies that can provide ultra smooth video from a single rotor machine. It is a very difficult undertaking that very few have all the technical/mechanical skills (and patience) to master. Can a single rotor design be built and balanced to the same relative vibration levels as a multirotor? Absolutely! The vibration frequency ranges are very different but in the end, if both are designed, built and balanced to exacting tolerances, the final product can be, for all intents and purposes, identical.

Regarding stability, there are two different, yet connected components that drive overall stability - one is the aircraft itself, with the second being the camera mount. If both operate smooth and stable, beautifully clean images result. If either is unstable, the other must absorb or dampen the unwanted motion. A perfect example is the current development of direct drive camera gimbals. These devices have both the speed and resolution to hide a multitude of sins being emanated from the aircraft airframe. Obviously, the smoother the airframe the better for camera and component life.

Within the next 12-24 months, it is reasonable to expect that a camera gimbal will be available that will provide near Cineflex quality for 10 -15 lb. cameras at a cost that is manageable for both top tier operators and insurance providers. This technology is already available for smaller cameras.

Flight Performance

In calm conditions, the flight performance is similar between the two arrangements. With electronic stability augmentation to assist the pilot, both have similar capabilities. In windy conditions however, the single rotor design wins hands down. This is due to the fact that a collective pitch rotor system is far more powerful and responsive to attitude changes when compared to multiple fixed pitch rotors. Think of this as driving a six speed performance sedan compared to a compact car with only third gear available. On top of this, the rotating mass of the larger rotors provides considerably more aerodynamic and gyroscopic stability than multirotors do. In general it is better to have an airframe/camera that never suffered from unwanted movement than one that did and had to have said movement removed through a correction in position.

Another significant difference is flying or descending at high speeds (above 55 mph) such as vehicle chase scenes. This is, once again, due to the advantages offered by a collective pitch rotor system used in single rotor designs over fixed pitch propellers on multicopters. A single rotor helicopter can descend at extremely high rates while still maintaining full control and camera stability.  This is made possible because the helicopter is being flown rapidly downward using collective pitch with power verses simply falling through its own downwash which usually results in unstable/unusable footage.

The next area, and this one is perhaps the most significant one, is pilot orientation. This factor alone is perhaps the biggest single reason that single rotor designs continue to dominate close range aerial filming in big budget feature films. It is not a major problem to clearly differentiate the nose from the tail at significant distances with a single rotor; Not so with symmetrical shaped airframes. To get around this limitation, multirotor designs rely on flight control systems with complex flight algorithms and GPS return to home features. The problem here is currently these systems are frequently subject to malfunction, and this is the last thing one would want when carrying $50K + of camera kit/glass. Flying first person view (FPV) and navigation lighting are workarounds for the orientation issue however, at present, all indications are that FPV mode of flight will be prohibited or very heavily regulated in the future and will only be permitted in unpopulated areas. First and foremost is to only use a pilot with years of the right kind of experience and one that can fly well without reliance on autopilots .

One area where the multicopter does have a very significant advantage is yaw axis stability. A single rotor helicopter must have a perfectly tuned anti-torque system that immediately and accurately corrects for even the slightest change in applied motor torque. It must also be fast and accurate enough to correct for wind gusts at every possible angle. Since multirotors control of the yaw axis is by varying motor torque through an opposing number of motors, this is a much less of an issue for this design. For a single rotor design, much of this limitation can be reduced by having the camera gimbal automatically correct for sudden movements in the yaw axis using stabilization devices.

A multirotor is also significantly less risky to launch and retrieve by hand than a single rotor helicopter. This can open up numerous opportunities to obtain shots in very tight spaces and difficult terrain.

As is often said "there is a perfect tool for every job" and this certainly applies to aerial cinematography. 

Cost

For most, making movies is a business endeavor, and so cost will always be a prime consideration. Currently the cost to build a rig capable of effectively carrying a Red Epic using a multiotor is roughly twice the cost of a single rotor design. You don't need to be a CPA to know that a lower initial investment, and the associated lower insurance costs, can result in a lower day rate being charged to the producer. This gap will likely narrow in the future, but for now, this is the current state.

Planning Ahead For a Successful Outcome

The list of things that can go wrong on an aerial shoot are almost endless. The secret is to properly prepare the things you can control - and have contingencies for those you cannot. 

First and foremost is to select a qualified, experienced, professional aerial service. Here are a few suggested qualifying inquiries:

1. Ask for relevant references for work of similar type using equivalent cameras and glass.

2. Clearly understand what type of insurance they provide. A world-class company will have no problem providing adequate third-party liability insurance. If the company asks you to split or cover the cost of their equipment, should an incident occur, this is a warning sign that you may not be working with competent professionals.

3. Ask to see raw, unstabilized footage of the types of shots you require, using the exact camera and glass you plan to shoot on.

4. Ask about their fleet. Remotely piloted camera rigs are complex machines made up of a myriad of electromechanical devices. If they only have one platform, this would be cause for concern. It is not practical to have every possible spare component on hand, much less the time needed to install and test. Even worse, should even an minor incident occur, your plans for aerials could quickly evaporate.

5. Don't fall for the "camera bait and switch". Many aerial video websites will indicate that they "can fly" the Red Epic for example. But when pressed to task they will quickly attempt to sway the prospective client to a DSLR. You don't have to settle for less. If all there shots are short and close, and you require a longer, continuous shot, this may be a warning sign that they do not have the confidence or experience to pull off long range shots with a cinema camera. See item 1 above and keep looking.

6. Ask for a copy of the pilots resume and professional flight experience. Statements like "3 years flying experience" is not much assurance. Sport flying at the local model club and flying on a movie set are worlds apart and very different skill sets. What really matters is actual flight hours shooting aerials. If the only platforms they have experience with are octocopters, then their experience is likely limited, as these platforms have only recently become viable tools for filming.

It is also important to gain an understanding of the equipment's limitations:

1. For the camera stabilization to function properly, the camera must be perfectly balanced on

every axis. If the aerial service has not flown the exact kit previously, time will be required in

advance to make all the necessary adjustments. Often even a filter change can upset the whole

apple cart. The most capable operators will have the capability to cover a wide array of cameras

and glass.

2. What is the flight time of the aerial rig? If electric powered, are enough batteries available to 

fly/recharge on a continuous basis?

3. If the shooting location is prone to wind, ask for raw footage examples shot in windy conditions. 

Also, the larger the rig, the better it's ability to hold position in the wind.

4. Ask about the range of motion for the camera gimbal. For example, almost all multicopters

suffer from very limited tilt range. With a wide lens, the frame tubes will come into camera frame,

even at a level tilt position. This can be a real problem for a variety of shots.

Last but not least, try to get a feel for the companies commitment to safety. Ask for a copy of

their safety manual. Ask them to outline their emergency procedures in the event something might go wrong. And do the entire industry a big favor and don't ask for shots requiring 

overflight of large crowds. The entire flight path should be considered an exclusion zone as

far as the general public is concerned.

Advanced Helicam Aerial Cinematography

Most Helicam aerial imaging is performed within a framework known as "line of sight" or LOS. There are several reasons for this. The most obvious being that if the pilot has a clear, continuous visual link to the aircraft being flown, it can be controlled at all times. The up side of this arrangement lies in its simplicity. Aside from flying behind an obstacle, having sudden vision problems or flying so far away as to lose orientation, there is very little that can go wrong, (aside from aircraft mechanical/electronic control problems anyway). The down side of this arrangement is that it limits the range of use to an area extending about 1200 feet horizontally and 400 feet vertically from the pilots fixed position. For the majority of shots required, this is a non-issue.

The radio control systems used today are capable of transmitting a clear signal several times further than the LOS distance. The position of the pilot is also critical for optimum LOS shooting. In some cases it is most effective to place the pilot on top of a building, mobile manlift or other fixed structure to improve visual range over any obstacles. This is particularly useful for flying just above tree-top level - skimming over a dense forest where trees would obstruct the pilots view if shot from ground level.

Helicams can also be piloted directly from the cameras transmitted video signal in what is called "first person view" or FPV. While this can improve close maneuvering around obstacles and extend operational range, loss of video feed remains a significant additional risk factor however. While this may be an acceptable risk for low end equipment, with the equipment currently available, it is not recommeded to fly a $50K to $100K camera kit using this method.

Recent advances in GPS based autopilots show great promise for extending the range of use well beyond the visual LOS range noted. These devices can be programmed in a manner that allows the aircraft to fly a series of "waypoints" and then return to its home position with just the flip of a switch. While this type of technology will assuredly advance the capabilities of Helicam systems for engineering and aerial mapping, for the moment there are several major technological hurdles that must be overcome first. Most notably among such obstacles includes the requirement of the system to sense and avoid both full sized aircraft and ground based obstacles. Another limiting factor is a pilot is capable of executing extremely complex, continuously variable commands that, at present, are well beyond the current capabilities of programmed systems.

As mentioned previously, Helicams are very well suited for operation from many types of moving platforms and vehicles in order to extend range. When land based vehicles are used for this purpose on public roads, local authorities should always be retained to temporarily shut down traffic and provide an escort if required in order to safely acquire the shot. Due to privacy concerns, state and local governments are also passing laws limiting or outright banning use of remotely piloted aircraft. Make sure to check local ordinances when scouting out aerial filming locations.

Another viable technique lies in the use of two or more pilots wherein one pilot hands off control to another in what is known as "relay mode". This effectively doubles the range of operation compared to single pilot operation and can be performed in a very seamless manner through radio communication.

At present, line of sight operation remains the predominant mode of operations for close range aerial imaging due to its inherent simplicity, flexibility and reliability. This will most certainly be augmented in the future in ways that are hard to imagine now.

For more info please visit http://www.perfectperspectivesaerial.com