Aerial Drone Preflight Checks

Checklist

Checklist

Preflight checks of your aerial drone are always a good idea, especially when you’re flying for a client. You may have seen a requirement from your insurance company to follow a written Standard Operating Procedure. That entails a checklist, which helps you to ensure your drone is ready for flight and to carry out its intended mission.

What does the FAA have to say?

The FAA’s position comes from the standpoint of safety of operation. Here’s the relevant sections:

14 CFR Section 107.15  Condition for safe operation:

(a) No person may operate a civil small unmanned aircraft system unless it is in a condition for safe operation. Prior to each flight, the remote pilot in command must check the small unmanned aircraft system to determine whether it is in a condition for safe operation.

(b) No person may continue flight of the small unmanned aircraft when he or she knows or has reason to know that the small unmanned aircraft system is no longer in a condition for safe operation.

FAA Advisory Circular 107-2 (June 2016, active to this date)

Para 5.9. Preflight Familiarization, Inspection, and Actions for Aircraft Operation. At 296 words, I’d rather provide you with a link than repeat it in this blog.

Para 7.3. Preflight Inspection. Ditto, 337 words, so please refer to the link.

Both paragraphs are well worth the five minutes to read.

What does your Insurance Company have to say?

Several insurance companies require aerial drone pilots to follow a Standard Operating Procedure (SOP). Although your drone manufacturer may not provide one, they’re fairly easy to develop, especially using the information in the FAA Advisory Circular.

Tips for Preflight Checks

Develop your own checklist.  We suggest including the following:

Software and firmware are up to date

SD card is installed

Camera lens is clean

Propellers are in good condition

Fresh batteries in your drone, controller, and cell phone/tablet

Develop a mission profile for your client and review prior to flight

Check the weather forecast, note the conditions prior to flight

Take off and hover at 5 feet; check propellers and flight controls

Add to this list as you see fit and go through it every time you fly. Pretty soon, your preflight checks will become second nature.

Flying Your Drone Indoors – What Could Possibly Go Wrong?

Flying Indoors

Who Is Your Insurance Company?

Flying your aerial drone inside a covered structure requires safety equipment, special settings, and a high degree of skill. This subject has been explored by a number of other bloggers, so we’ll summarize their recommendations and present a few of our own.

The FAA Does Not Have Jurisdiction over Indoor Flying

Part 107 doesn’t mention flying indoors because these areas are not considered navigable air space. However, there are a number of applications for indoor flying, including real estate photography, conventions, games, and drone competitions. Such applications require special considerations by the pilot. We’ll cover several in this article.

Insurance

When flying indoors, there’s significant risk that your drone will get damaged, harm people, and/or damage property. Therefore, check with your insurance company to see if indoor flight injuries and damages are covered.

Many drone pilots use Verify, now Thimble, a popular pay by the hour insurance company, which specifically excludes coverage for indoor flying. Our own insurance company, Global Aerospace, excludes coverage for competitions, but otherwise appears to cover indoor operations (per my agent). This gets confusing, since Thimble contracts with Global Aerospace. So, read your policy carefully to ensure you’re covered for flying indoors.

Tips for Flying Indoors

  1. Always use propeller guards to reduce injury and damage.
  2. Turn off GPS positioning. Interference or loss of signal can lead to unintended drone movements. For certain DJI drones, this means turning off P mode, and using ATTI mode instead.
  3. Related to 2, don’t use automated flight settings such as tracking or waypoints.
  4. Turn off obstacle avoidance. Although vision systems are excellent for outdoor flying, they can lead to stubborn flight control indoors and possible human error through over-reaction.
  5. Use beginner mode, if your flight controller supports it. Flight control stick sensitivities are decreased.
  6. Avoid ceilings, walls, and other flat surfaces. Prop wash causes unpredictable flight behavior.
  7. Turn off automatic Return to Home. If possible, set loss of signal action to hover in place.

For additional information, please refer to:

Drone U

Pilot Institute

Dronegenuity

Alternatives to Flying Indoors

Indoor photography can often be done just as effectively with a camera mounted onto a pole, rather than using an aerial drone. For example, mount your camera onto a glide stabilizer and walk your camera through the desired area. (We use our Samsung S20+ cell phone on a DJI Osmo for these shots.) Reduce camera shake with your video processor’s image stabilization filter.

This same technique can be used outdoors as well. A client once asked us to survey an asphalt road, suggesting that we fly just below the tree canopy. They were happy to learn of a much simpler method to mount a camera in front of and above their truck to capture their footage.

However, the cell phone/Osmo solution doesn’t work in high winds. For example, I once tried this technique from the open cockpit of a biplane but the 80 mph wind overpowered the Osmo. That approach was an epic failure, but salvaged by holding the cell phone and stabilizing the video in post processing.

When there’s no other solution than flying indoors, then we advise extreme caution, following these tips, and checking your insurance coverage.

DJI Phantom 4 Pro Yaw Drift

Phantom 4 Pro Yaw Drift

Compensate P4P Yaw Drift

What causes the Phantom 4 Pro to drift in yaw (heading) during programmed flights? This appears to be a common thread in a number of blogs and is a problem we’ve also encountered. As you know, I like to take on the hard problems, think them through and develop solutions. In this blog, I’ll offer ways to measure the offset and a method of compensation.

As I stated above, this is a common problem, but no one that I know of has determined the cause. Please comment if you have a better explanation and I’ll update this blog.

Are other aerial drones similarly affected? Please comment, I’d love to hear from you.

We See Yaw Drift in All of Our Programmed Flights

The yaw drift that we’ve encountered with our Phantom 4 Pro V2 is much more significant than crabbing (please see our April 28, 2019 blog on crabbing). Our data files indicated that the crabbing effect is around ±1.5 degrees, and is largely compensated by the drone’s flight controller. However, our measured yaw offset runs as high as 30 degrees, sometimes more.

Of note, from our data files we plotted the GPS position, which showed the drone stayed on its programmed circular path and its heading was tangent to the circle.

Measuring Yaw Offset

We program almost all of our aerial drone photography sessions, so when the drone’s camera offsets then it’s pretty obvious in the recorded video. A simple method to measure yaw drift is to record a Point of Interest video. That is, to run a circle around a point with the camera pointed at the center. A large radius allows the drone to be operated at maximum speed (we used 1000 feet radius and 21 mph in our test runs), where the drift was quite noticeable.

For example, print out a Google Map of the test site; then graph the video’s centerline of sight at 15-second intervals. You can measure the yaw offset with a ruler for distance, and a protractor for angle. E.g. measure the distance/angle from the centerline to the center point.

Graphical Data Results

Our data set included ten video runs, taken on different days so we had variations in drone speed, wind speed, and wind direction. In almost every case, the yaw drift was affected by both the drone speed and wind speed. One key measurement was the combined speed of the drone, where we found correlation between the maximum yaw drift and the combined air speed of the drone (that is, heading into the wind).

Our graphical analysis suggests that yaw drift can be minimized when both the wind speed and drone speed are less than 10 mph.

Conditions

  1. Drone: a 2-year old DJI Phantom 4 Pro V2 with an iPad 9.7-inch tablet. Yaw effects were similar for both DJI Go 4 and Litchi apps.
  2. Yaw drift appeared to be the same before and after INS and compass calibrations.
  3. We tried to force the drone’s yaw drift by hovering 5 feet above ground and blowing the drone with a fan. We blew the drone so hard that the camera’s gimbal was pushed into its stops, but it returned to linear after the wind was reduced. The drone’s airframe did tilt into the wind to maintain position, as we would expect, but it didn’t change its yaw (heading).
  4. We measured yaw drift in circular “Point of Interest” runs, where the drone’s camera was pointed toward the center and the drone airframe was flying sideways into the wind. CCW runs resulted in less yaw drift, so only one run was CW.

Conclusions

In flight, it appears that the drone’s flight controller is adjusting heading as the drone tilts into the headwind. So, if there’s a large headwind, the drone tilts more to maintain its GPS speed and it also yaws to the left. Since the drone’s legs don’t appear in the video, we conclude that the flight controller must be changing the drone’s airframe, not the camera.

Minimizing the Effects of Yaw Offset

  1. Fly your drone at a speed of less than 10 mph and when the wind is less than 10 mph.
  2. The yaw offset can be compensated by changing your programmed center point into the wind.
  3. Fly a larger diameter radius so the desired field of view is around 80% of the frame, then crop down to the desired field of view in post-processing.

Short Video Clips

Our post-production services now include short videos to dress up aerial drone video clips that we have taken. This service is ideally suited to real estate firms that want customized information added to their advertising clips.

Our full-service videos include a number of video clips and photos, introduction slides, overhead map photos, closing slides, and audio track options. The difference with our short videos is that only one selected video clip is modified to include an intro slide with agency contact information and an overhead map photo showing property information such as boundaries.

Our short videos are much easier to create and they provide our clients with tailored information in their aerial videos. This information helps your customers visualize the location of the property and area features.

Although we don’t offer moving boundary lines for our videos, we can add them to the overhead map photos (typically credited to Google Maps). Just about any text information can be added to customize the short video to our client’s requirements.

Interested? Please follow this link to a larger example of the above short video:
https://youtu.be/55B2hrF1y9k

Price information is posted to Our Prices tab, under Post-Production. Economies of scale will apply, so if you have several similar short videos in mind, we can discount our price. Please contact us for details.

Flying Your Aerial Drone Over Water

Flying Over Water

Flying Over Water

Flying your drone at low altitude over water can be hazardous to its health. However, there are times when professional aerial drone photographers and videographers will have to do precisely that. The drones I fly are manufactured by DJI, which discourages flying over water.

DJI Manufacturer Statements Include:

The Vision System requires clear pattern variations, with light conditions greater than 100 lux. Further, they state that users should operate the aircraft with great caution when flying over water or transparent surfaces. And specifically, Vision Positioning may not function properly when the aircraft is flying over water.

What is a Vision System?

Vision systems may use ultrasonic sensors, infrared sensors, and cameras to detect objects in close proximity to the drone. Several drone models use combinations of sensors to accurately hold altitude and to enable object tracking functions.

How does a Vision System work?

Vision systems are used for short range detection and ranging. Ultrasonic-based sensors operate at about 40 kHz and use pulsed sonar techniques to detect the nearest object. Camera-based sensors employ image processing to determine objects that not only include the ground below but also people and moving vehicles.

DJI states their vision systems rely on very sophisticated image processing to detect nearby objects. Two models that I have owned are the Phantom 3 Professional and the Phantom 4 Professional Version 2. Both employ a combination of ultrasonic and camera sensors to determine their altitude above ground.

At low altitude, the fusion algorithm prioritizes the camera sensor above the ultrasonic sensor and the altimeter (barometer). e.g. the drone’s control system maintains a certain altitude that is stabilized by its downlooking camera. The problem with flying over water is that the downlooking camera sees what the human eye will see, including objects below the surface such as the bottom.

When hovering over water (or any other transparent object), the processor may be fooled into thinking the drone is flying too high, so it orders the drone to decrease its altitude. This happens fairly quickly, which risks the drone dropping into the water.

When you Absolutely Must Fly over Water . . .

If you have to fly below 2 meters for a special shot, we recommend that you turn off the Vision System to avoid unstable movements by the drone. DJI recommends that you fly the drone at low speed and stay alert to adjust altitude.

What else could possibly cause Altitude Issues over Water?

Other physical effects could fool the drone’s processor into decreasing altitude, but only one scenario seems to fit. For an ultrasonic sonar sensor, the sensitivity time control could cause a near-water second echo to be larger than the first echo, which would read a higher altitude.

What about Sonar Returns off the Sediment?

Although sound waves can penetrate the air-water interface, the transmission loss is about 99.95% – each way! Remember, the sound has to go back through the water-air interface for another loss of 99.95%. There’s just not enough signal return to fool the sensor.

You can likewise rule out other physical effects because they would lead the processor to read a lower altitude. These include: ground effect on the barometer and the increased sound speed caused by prop wash water vapor. In other words, the processor would be fooled into increasing the drone’s altitude.

Conclusion

Flying your drone at low altitude over water can risk losing your aircraft. If you must fly under these conditions, then turn off the Vision Positioning System, maintain a minimum altitude of 2 meters, and keep a close watch on your drone.

Aerial Drone Altimeter Accuracy Specification

Measuring Your Drone's Altitude

Measuring Your Drone’s Altitude

One of the specifications that you won’t find for your aerial drone is its altimeter accuracy. In fact, if you call the manufacturer’s support staff they won’t be able to provide you with that spec either. Technology behind the common altimeter is consistent across many of the latest airborne vehicles, including drones. In most cases, altimeter inaccuracies are minor, so these instruments serve their purpose well.

However, aerial drones operate much closer to ground than most other aviation vehicles. This is where we as drone pilots might notice a drift in reported altitude throughout our drone’s flight. We’ll explain why this drift occurs and what can be done to compensate for it.

How Does an Altimeter Work?

What we know is that as one goes up in altitude, the air pressure goes down. The relationship between air pressure and altitude is quite predictable, but subject to minor variables such as the gas content and temperature. So, whether the readout is an analog meter or a more sophisticated digital instrument, the altitude is easily converted from the air pressure. Click here for a detailed explanation on how altimeters do this.

Which of These “Minor Variables” Affect My Drone’s Altimeter?

Over the time span of a drone flight, the atmosphere’s gas content, that is Nitrogen, Oxygen, CO2, water vapor, etc., can be treated as fixed. Surface-level barometric pressure changes can also be treated as fixed. That leaves variances in temperature as the most significant contributor to altimeter inaccuracy.

Think about where the barometer is located in your drone. It’s a small sensor mounted on or near the motherboard in a relatively confined space. From the beginning of a flight to its end, heat from the drone’s control circuitry builds up in this space, affecting the barometer. Whether it’s a change in air pressure or temperature, the result is the same – a change in reported altitude.

Low Altitude Operations

This is where the thermal effect on reported altitude is more noticeable. You may have noticed when coming in for a landing that your drone is reporting an altitude of some 15 feet or so when it’s actually 3 feet off the ground. If you were to simply take off and hover, you would find that the indicated altitude slowly increases while the drone is actually in a stationary position. These are thermal effects.

Temperature drift in your drone’s altitude reading is hardly noticeable when flying high, and may only be a minor nuisance when flying low. But, where it can cause trouble is when using a programmed mode that instructs the drone to fly at a certain altitude. If that happens to be 10 feet or so, then the program will try to drive the drone at that altitude, but in reality is flying it toward the ground. Even at higher altitudes, you can lose your margin when programmed flight decreases your drone’s actual altitude above objects such as buildings and trees.

What to do When Altitude Accuracy is Important

I recently had a client that required drone photography at several specific altitudes above ground level. This job had to do with precision surveying in advance of a construction project. Since my drone’s altimeter would not meet their requirements, they set up a surveying instrument to measure the drone’s altitude (see picture). You may also consider other workarounds, such as:

  1. At the time of your critical photos/videos, record the drone’s altitude, then land and record altitude again. Take the difference for true altitude.
  2. Allow the drone to warm up for several minutes before lift-off. At the end of flight, use the reported landing altitude to estimate in-flight altitudes. (e.g. interpolate the number of feet per minute of drift.)
  3. Use an independent measurement device, such as a laser rangefinder.

Flying Your Drone in Native American Reservation Airspace

Flying in Native American Airspace

Flying in Native American Airspace

A question was raised during my recent vacation to a National Park in Montana: Do Native American Nations have sovereign authority over their airspace? I had intended to fly the Park’s edge region from Tribal lands (which legally complies with the NPS Policy Memorandum 14-05). However, I realized the rules that apply to airspace over tribal lands might be different.

Airspace Sovereignty from the Native American Perspective

A retired chief of police of an Indian reservation (Gila River Indian Community, AZ) advised that tribal governments are very sensitive of their sovereignty and sacred grounds. He recommended that drone pilots contact the tribal government or police department and ask for permission to fly. The tribes appreciate a show of respect by asking. To sweeten the deal, perhaps you as a drone pilot could offer photos and videos that the tribe could use for its own purposes.

Unfortunately, there have been many cases of trespassers desecrating tribal lands and taking sacred artifacts. As a result, tribal governments now employ their own law enforcement officers that patrol their territory on 4×4’s. My understanding is that you do not want to be on the wrong side of a tribal LEO if you meet up with one!

Has Tribal Sovereignty over Airspace been Settled by the Federal Courts?

In my blog “Does an Aerial Drone Pilot have the Right to Fly Over Private Property?” we looked at property owners’ rights to the airspace within their property lines. It would be consistent, then, that Tribal Nations would have the same airspace rights. That is, they own the airspace up to 500 feet above ground level. This policy was affirmed in a 2016 paper by the University of Oklahoma College of Law Digital Commons “Why Indian Tribes Possess the Sovereign Authority to Regulate Tribal Airspace.” However, in this paper, an argument was made that Tribal Nations own ALL of the airspace within their boundaries.

Of course, such an assertion by tribal governments conflicts with federal regulations and FAA jurisdiction. However, the author makes a good point that Native American Nations enjoy significant sovereignty in other areas of the law. Since the airspace jurisdiction question had not been resolved as of 2016, drone pilots should contact tribal authorities and request their permission to fly.

Your Rights to Retrieve a Drone If It Lands On Private Property, Part 2

What If An Irate Property Owner Has Your Drone?

What If An Irate Property Owner Has Your Drone?

Aerial drones are usually reliable, and in the hands of an experienced operator are brought home with sufficient battery power in reserve. However, there may be circumstances when the aircraft can’t be brought home and it lands on someone else’s property. I established in Part 1 that the property owner does not have a lawful claim on your aircraft. In this blog, we review your recovery options in less-than-friendly circumstances.

What Are My Options?

If the property owner refuses to return your aircraft, or allow you to retrieve it, then you should call local law enforcement to intervene. As long as no harm was done, then it’s likely that the property owner will hand over your drone to a law enforcement officer. Although the owner may be reluctant, they may come around after being advised that they face a charge of larceny if they hold onto it. There are several other ways this scenario can play out (such as intentionally destroying your aircraft), but if none turn out favorable to you, then you’ll have to ask for a law enforcement report and proceed with a civil or criminal complaint.

I recently heard of a scenario where a novice was using their drone for low-level spying, which violates state and federal privacy laws. If the property owner gets your drone under these circumstances (using any available means) your claim is going to be an uphill battle.

If your aircraft gets stuck in the owner’s tree or is on their rooftop, then be prepared to pay for a service to come out to retrieve it for you. For example, this may cost you $150 for a tree service to come out, climb the tree, retrieve your drone, and assure the owner that no harm was done to their tree.

Sometimes the best grease is money. If the property owner is annoyed, then you may offer a modest sum for their troubles. Conversely, if the property owner demands a “salvage” fee, then this may be the path of least resistance that gets your aircraft back. Even if the law of ownership is on your side, getting a legal judgment will be costly and take time. In the meantime, you’ll probably have to buy another drone.

There is the unpleasant scenario where your drone damaged property or injured a person (or animal). In such a case, your drone deprived the owner of their full enjoyment of the land and your situation has become a whole lot more complicated. This is why you need a good liability insurance policy.

What if the Property Owner Refuses to Return My Aircraft?

Aerial drones can be expensive, with the value of some in the thousands of dollars. At this price point, a court proceeding may be worth the cost. For less expensive drones, a court proceeding may give you some degree of satisfaction but the cost may exceed the drone’s value. Some property owners are so belligerent that they will destroy your drone. I wish I could be gentler in advising that you may need to be prepared to accept the loss of your drone.

In Any Scenario with Complications, Document Everything and Take Pictures

If your operations require flying over private property, then carry an insurance policy that covers liability AND loss of aircraft. If it goes down, then collect as much information as possible about the circumstances, take pictures, print out your controller’s log files, and take names. When dealing with property owners, always be professional and affirm their rights as well as your own. Even though the law is on your side, the property owner has possession of your drone so carefully assert your rights in the kindest manner possible.

Your Rights to Recover a Drone If It Lands On Private Property, Part 1

Did Your Drone Come Down On Private Property?

Did Your Drone Come Down On Private Property?

Aerial drones are usually reliable, and in the hands of an experienced operator are brought home with sufficient battery power in reserve. However, there may be circumstances when the aircraft can’t be brought home and it lands on private property. Does the private property owner have a lawful claim on your drone? In Part 1, we review your recovery options in relatively cooperative, no-harm circumstances. In Part 2, we’ll review your recovery options in less-than-friendly circumstances.

What Could Possibly Go Wrong?

First, let’s review some of the circumstances that are covered in this blog: (1) unexpected mechanical failure, such as a battery issue, electronic failure, or motor/propeller malfunction; (2) loss of control, such as an automatic return to home at too low of an altitude and it crashes into an object; or (3) forced landing due to an exhausted battery.

Please note there are a number of circumstances not covered in this blog. Primarily, these are activities that might deprive the property owner of the full enjoyment of their land, including evidence of: (1) the drone is causing a nuisance: (2) being flown recklessly; or (3) violating a state privacy law. For whatever reason an aircraft may come down under these circumstances, your rights may be compromised. Please read my blog on flying over private property. In addition, if your aircraft enters controlled airspace and a law enforcement or military activity takes it down, you’ll have an uphill battle getting it back.

Do You Still Own Your Drone?

Case law is well settled that ownership of your property is retained, regardless of where that property may be situated. Conversion of lost property doesn’t occur unless it remains unclaimed by the owner. So, for a property owner to cite conversion (that is to assume ownership), they must post a notice of “found property” or turn it over to law enforcement for a period of time, typically 3 months.

So yes, you have the right to recover your aircraft from a property owner. This doesn’t mean that you can intentionally trespass, especially if the owner is standing there with a shotgun, or there are other obstacles such as dangerous animals. But you do have the right to ask for the return of your property.

How Do You Get Your Drone Back?

If you know where it landed, then you should introduce yourself to the property owner, identify yourself as the drone owner, and ask for its return. The owner may be annoyed, but a reasonable explanation of how it ended up on their property will be helpful. Further, if it has an FAA registration number and other identifying information, then you have established your right of ownership. Don’t forget that your controller also establishes ownership, simply proven by operating the drone; e.g. moving the camera, starting the motors, etc.

Of course, there may be other scenarios where the property owner is less cooperative. These include situations where your aircraft is stuck in their tree, on their roof, or has caused damage. There may also be scenarios where the property owner is just plain uncooperative. We’ll address those in Part 2.

Does a Private Property Owner Have the Right to Shoot Down Your Drone?

Shooting at a Drone is Illegal

Shooting at a Drone is Illegal

Shooting down an aerial drone is a federal crime and could result in criminal liability. Regardless of how a property owner feels about a drone’s (perceived) invasion of privacy over their private property, there are more civil solutions available.

State Privacy Laws Favor Property Owners

We established in our May 2019 blog that case law has favored property owners for altitudes up to 500 feet above their property. So, the wise drone pilot will ensure that they’re flying in accordance with FAA regulations and avoiding any appearance of: (1) the drone is causing a nuisance: (2) being flown recklessly; or (3) violating your state’s privacy laws.

Federal Aviation Laws Favor Drone Pilots

For obvious safety reasons, a drone hit by gunfire could crash, causing injury to persons or damage to property on the ground, or it could collide with other objects in the air. So, shooting at an unmanned aircraft could result in criminal or civil liability, just as firing at a manned airplane. The FAA has cited federal law in their declaration that shooting a drone constitutes a federal crime and could result in criminal liability. Where does it say that?

Federal Law states it in U.S. Code Title 18, Section 32 “Whoever willfully sets fire to, damages, destroys, disables, or wrecks any aircraft in the special aircraft jurisdiction of the United States . . . shall be fined under this title or imprisoned not more than twenty years or both.” Under subsection (c), threatening a drone or a drone operator would also be a federal crime subject to five years in prison.

What if My Drone is Shot Down?

Aerial drone pilots who have an FAA registration number affixed to their aircraft, are Part 107 certified, and flying in accordance with FAA rules will probably have a good case for filing a criminal complaint . . . As long as they’re respecting the rights of property owners! However, case law can go against the drone pilot if it can be shown that they were depriving the property owner of their rights, particularly invasion of privacy.

Summary

Drone pilots must be careful about flying over other people’s property, especially at low altitude. State laws control property rights and in at least one case have favored an owner for shooting down a drone that was allegedly used for spying. In light of Amazon’s recent approval to deliver small packages by drones, the gray areas between federal and state rights certainly need to be clarified.

Drone pilots should know their rights but also avoid situations that may place their drone in jeopardy. Getting entangled in the legal system is expensive and should be avoided if at all possible.

Don’t miss our next blog on your right to retrieve a drone that lands/crashes onto private property.