Software and firmware run the world of UAS, and some developer/manufacturers offer/require frequent updates. Updates are a component of the maintenance process for any UAS and should be manually checked at minimum, every 30 days. We recommend that any old software/firmware versions be archived if possible, in the event of problems encountered with a new update. Rolling back software is a good option (when possible). In addition to archiving old software/firmware versions (when possible), it is required by the FAA that any maintenance be logged. This includes logging any software/firmware updates to the aircraft system.
For many UAS pilots/operators, the process ends at the update. In fact, many updates occur in-field with automated software updates being required by some manufacturer/developers, so the pilot uses WiFi or cellular connection to update the aircraft, controller, software, or battery, just before flying the next mission. There have been many instances where the next action with the aircraft is to begin the planned mission.
This is a mistake.
Any time software or firmware on the aircraft, tablet, battery, IMU, or other component of the aircraft is implemented, it is recommended that the aircraft be re-calibrated. This step is frequently put aside in interests of time, and can result in disaster.
The issue this pilot had could have been avoided had the aircraft and system been recalibrated prior to flight. The aircraft is a total loss due to compass error.
Software/Firmware updates are not always reliable and in some cases, result in safety issues. Recalibration is an important step in mitigating risk due to unknown factors generated via the software/firmware update process. Compass, accelerometer, etc all must be recalibrated. It is also a good idea to let the aircraft sit for a few minutes after powering up, to acquire all satellites prior to flight after a recalibration.
Take 5 to avoid issues. Calibrate after every software/firmware update, and log the calibration along with the notice of update/firmware changelog. Your flights will be more safe and confident.
“1 October, Harvest Festival, Route 91” are all synonymous to Nevadans and first responders, marking the America’s worst-yet mass shooting event when a lone gunman in a high-rise hotel opened fire on concert goers (the official investigatory title for this event is “1 October”).
- 58 victims died of gunshot wounds.
- 422 individuals were injured by gunfire.
- Approximately 800 concert attendees were injured from gunfire, trampling, or other injury escaping the chaos.
Over the course of several hours following the shooting; law enforcement, fire, EMS services, and civilians acted as one to manage the scene, transporting victims to local hospitals, secure the area, and begin collection of evidence.
sUAS ON SCENE
sUAS were a component of the evidence-gathering process under the direction of the FBI and Las Vegas Metropolitan Police Department (LVMPD).
LVMPD partnered with Nevada Highway Patrol’s Multidisciplinary Investigation and Reconstruction Team and their sUAS as part of the scene given the size of the site, and the amount of data that needed to be collected in a short period of time. An outside technical advisor was also brought in to advise and as a subject matter expert to ensure automated mission compliance and best-practices were observed in each of the missions.
The area to be captured via sUAS was just over 19 acres in overall size.
Two primary considerations for data integrity:
- Corruption of image from shadow/moving sun in a static environment
- Corruption of area from propwash
To combat the second issue, altitudes for flight were selected based on height and downdraft from the aircraft.
Two types of aircraft were evaluated, a quadcopter and a hexacopter. The hexacopter offered significantly less ground disturbance and was selected for the mission. It was also much quieter and was expected to not attract undue attention at any altitude, as there were many tourists along Las Vegas Boulevard.
In order to counter the primary issue it was determined that the area would be captured with three simultaneous flights, spatially and temporally separated.
The mission requirements shed light on several challenges.
- The site is located in Class B airspace, less than 500’ from active aprons, taxiways, and runways.
- An active investigation underway created concern for flight in areas over investigators inside the secured perimeter.
- Time was at a premium, as this is an outdoor venue and weather/sun were actively degrading evidence.
- Helicopters from tour companies were not observant of the in-place TFR, and were constantly in the airspace, trying to show the crime scene to tourists.
- Completing the missions within a narrow window of time was a crucial element so as to obtain the best possible images at all four primary areas of flight without shadow distortion.
- A delicate balance of altitude and resolution needed to be struck to not affect evidence while obtaining the highest resolution possible.
Plans for automated flight were discussed on-site with time of flight determined by angle of sun. Once plans were determined and drawn, FBI and LVMPD personnel approved the automated flight areas, altitudes, and speed of flight. The automated, map-mission flight paths were programmed into each of the three ground stations, and verified by all authorized parties.
Flight plans included 85% overlap, 70% sidelap, with 25% additional area beyond the festival grounds captured for clean edges at the optical extremes.
Altitudes of flight were 60’, 90’, 150’, and 200’ with 5’ altitude offsets from center
North and South areas began flight in an easterly/westerly direction, while the center area began northerly/southerly directions, 5’ lower than north/south units. Temporal, horizontal, and vertical separation ensured no possibility of mid-air collision existed.
Road closures surrounding the crime scene provided a secure area for launch/recovery of aircraft with no traffic in the area, providing for VLOS over the 19 acre property.
Once safety checks and the normal pre-flight checks were completed, the aircraft were placed in the launch/recovery area and three aircraft were launched eight minutes apart.
During flight, the ground station controller provided real-time feedback indicating where images have been captured.
Donning sterile suits required to enter the perimeter of the crime scene allowed for manual flight in specific areas where closer inspection of complicated surfaces were required. Manual flights inside the area perimeter provided insights not visible from the ground level. Examples of projectile impact were found on a power pole at the intersection of two streets, and two impact points were discovered in the relay tower speakers that had not previously been found.
Original image courtesy of Las Vegas Review/Journal/modified by author
These areas were complicated for UAS flight, crossed with guy wires for tower stability, speaker cables strung across steel rigging, lighting instruments, hot, black metal in turbulent winds in areas where three observers were placed to assist the pilot in flying in these tight, physically and optically challenging spaces around the stage, speaker towers, food court/tents, billboard signage, and fence perimeters.
Original image courtesy of Las Vegas Review/Journal/modified by author
Following the nine flights (3×3) over the main grounds, a separate mission was executed over the abandoned hotel that extends into the entertainment property. These missions were a combination of manual inspection when potential evidence was observed, and automated mapping flights to capture the at-present data. In this particular instance, the benefits of the hexacopter were appreciated; turbulent ground winds, rotors, powerlines, palm trees, a confined area, and limited physical access each contributed to the challenges of this series of missions. VLOS was maintained with the observer standing on the rear of a patrol vehicle due to a high, covered fence and a limited launch area.
Three automated group flights at three altitudes, separate stage and hotel flights, manual flight inside the perimeter captured over 6,000 images. These images were input to two dimensional and three dimensional software applications for orthagonal mapping and 3D modelling. Survey markings were taken from previously operated TotalStation sites and physical objects used as GCP.
The author has not seen the final results from the orthogrammatic image render. The planned workflow is to render each of the separate areas for consistent GSD, added into a master render for each altitude. Once the flights were complete, memory cards were handed over to the federal agency.
This was very much a team effort. ATC, McCarran Airport, FAA, City of Las Vegas, Department of Public Safety, FBI, local subject matter expert, and other investigative agencies worked within a highly communicative environment to ensure no evidence was compromised, that all personnel were aware of each others activities, data/areas logged for clarity, and flights indicated in written, pictorial, and telemetry formats were shared between teams.
Until October 1, the World Trade Center had been the largest physical crime scene in America with a total area of approximately seven and a half acres. 1 October is nearly three times in size. Due to persons involved with both scenes, availability of data and cost from the two events may be compared and examined to gain an understanding of technical and operational improvements over the past 17 years.
In the last week of September, 2001, a Super Twin Otter with several sensor systems was called up to capture data from the World Trade Center scene.
Flying orbital and grid patterns over the course of five days, significant amounts of data were collected for analysis by multiple agencies.
Costs were reported over 1.5M, including fuel, personnel, equipment, and time.
Image courtesy of Wikipedia
Although the images captured are still classified, data from surrounding, unrelated areas demonstrate the poor quality of image capture. By comparison with modern technology, the images are of limited value, offering little useful data (by comparison).
The time, cost, labor, headcount, and quality of data are all areas where UAV have proven their value to law enforcement, and in this case, costing $1.5M vs $15,000 (cost of three aircraft, batteries, and accessories), while providing incalculably greater value through images that may be digitally shared in 2D, 3D form, annotated, analysed simultaneously by multiple agencies and investigators.
The value of sUAS proved itself through rapid access to available airspace, speed of operation, quality of data, cost of operation, ability of continuous flight, noise and traffic impact on the surrounding area and area of investigation, speed to solution, instant verification of data capture and image quality, ability to simultaneously capture multiple areas, and most importantly, safety to all persons involved in the acquisition of data, processing and investigation of the 1 October scene.
FoxFury, Pix4D, Sundance Media Group (SMG), and the Nevada Drone Center of Excellence came together during the InterDrone Conference, sharing techniques and technology used for capturing forensic scenes during night hours. This event will be repeated during the Commercial UAV Expo in Las Vegas on October 3, at the WestGate hotel. Register now for the Commercial UAV Expo CSI demonstration.
Sundance Media Group and the CSI data may also be viewed at Booth #5413 at the Global Security eXchange Security Conference and Expo, September 23-27 in Las Vegas, NV at the Las Vegas Convention Center. Register for the GSX show HERE.
“As you’d expect, the ratio of nighttime vs daytime crime is much higher,” said one investigator from a local law enforcement agency. “This sort of training and experience provides greater depth to our toolkit. We are grateful to have partners willing to research and share experiences that may benefit our agency.”
Using FoxFury Nomad Hi CRI, daylight-balanced lighting, to light the scene in an area of East Henderson where no power and no available light existed, the team used Hollywood makeup techniques, a bit of stage blood, and shell casings to re-create a genuine crime scene. The “crime scene” was kept pristine as nearly 100 attendees looked on.
The FoxFury Nomads, properly positioned, provide a no/low-shadow environment with accurate colors.
“Most LED lighting systems will generate a color-cast that may create problems in the post-capture investigation. Moreover, the lights do not require cabling that can trip up those on-scene, or create their own form of scene contamination. To place them, we merely pull down three legs, raise the pillar, and power up the lights. At half intensity, the lights provide approximately 12 hours of lighting,” says Douglas Spotted Eagle of Sundance Media Group. The FoxFury Nomads may be charged over a 12v connection in a patrol/support vehicle as well.
FoxFury Rugo’s are placed on the aircraft for additional lighting as well as for FAA compliance. The Rugo provides a constant flash indicator in addition to options for Flood, Flat, or Pinspot light distribution. The Rugo mounts for the Yuneec and DJI products offer a 360 swivel, allowing for light control in any direction. Users may choose from four intensities in addition to the flash/cycle option.
James Spear talked about the aircraft lighting, saying “We use the FoxFury Rugo’s for our scene and night lighting not only due to the many options for lighting focus, but also because of the interchangeable batteries. At full intensity, we enjoy about an hour of flight time, yet the lights will operate for up to three hours at lower intensities.”
Ground Control Points were laid into place on the perimeter of the scene, taking care to ensure no one stepped into the scene. These are used as tie-points during the 2D and 3D assembly of the data, using Pix4Dmapper. The GCP’s for night capture are painted with Day-Glo paint colors for bright visibility and identification in the darkness of night. Similar techniques may be employed during thermal mapping projects (Pix4Dmapper on the desktop may be used for thermal mapping if the thermal camera properly embeds/captures meta-data). Shown here by Brady Reisch of the SMG team, the GCP’s are a highly-valued component to set scale constraints to the scene.
The area was flown with a drone equipped with a camera capturing GPS location, capturing a reduced area for purposes of avoiding flight over persons, and for expediency during the demonstration.
The pilot, wearing a Brother AiRScouter HUD, is able to simultaneously observe the aircraft and telemetry. Attendees of the event had opportunity to wear the HUD and appreciate the value of a constant display that enables pilots to observe the aircraft, telemetry, and video data, all at once. Jennifer Pidgen of SMG commented, “We have equipped each of our pilots with the AiRScouter system not only for these scenarios, but more importantly for those times where we’re inspecting critical detail and looking away from the aircraft may increase risk. The AirScouter enables our pilots to observe the aircraft flying closely to objects while providing a constant stream of information to the pilot.”
The sUAS captured nearly 100 photos used to create the overall model/map of the scene. Normally, the scene would encompass the entire area in the event that there may be more clues hidden in the brush or sandy areas surrounding the site. Thermal may also be used to search for other bodies, or persons involved in the crew.
“The images were then taken into the Sundance Media Group AVOC computers, where we assembled them as a low-resolution 2D file to verify all areas of the scene were adequately captured,” said Sam Pepple, of Pix4D. “Once verification and confirmation are complete, the scene may be released to the rest of the CSI team for standard investigation. Following the low-resolution verification, a high-resolution image was processed and evaluated by the team, as shown in the Pix4D booth at InterDrone.”
The point cloud of the scene is shared online here. Hold CTRL+SHIFT to rotate the scene in 3 dimensions.
Once the scene is captured, the rectified scene may be viewed internally or via secured online site by CSA, or Crime Scene Analysts, allowing measurements to be verified, retaken, or examined from a multitude of angles.
The Sundance Media Group team will be demonstrating this experience at the Commercial UAV Expo in Las Vegas on October 3. Location TBA, near the WestGate hotel (walking distance). REGISTER HERE. It is recommended that attendees register early. The last event ran out of space/slots within three days.
Douglas Spotted Eagle addresses a crowd of nearly 100 attendees at the CSI demo.
Sam Pepple of Pix4D addresses the crowd, describing how Pix4D will be used to capture the scene, the importance and value of GCP, and why these models are valuable to crime scene investigators.
An investigator briefs the crowd on how UAS are changing the face of scene capture, and details how a scene is approached, observed, captured, and processed.
We captured the scene using multiple drones. Brady Reisch captured video of the event; we’ll soon have that available for viewing.
The SMG AVOC was the hub of activity prior to the night flight. Pizza and drinks provided by FoxFury and Pix4D.
The FoxFury Rugo lights are a key component to SMG night flight. They may be mounted to nearly any sUAS platform including Yuneec H520, Hplus, DJI Phantom, Inspire 1, Inspire 2, Matrice 200 series, AEE Mach 4, and many others.
IF A HOMEOWNER DOESN’T OWN THE AIR ABOVE THEIR HOME, WHO DOES?
Recently, heated discussions surrounding the topic of “Air Rights”have arisen within the UAS community, generating confusion and division within the community. In one forum of UAS professionals, an industry member was so angered by the confusion that negative press releases were threatened, jobs were held ransom, and phone calls to local FSDO’s were made.
The intent of this article is to clear up a few misconceptions. Note the author is not an attorney, but rather a very active, long-time member of the aviation and UAS communities (although this article has been vetted by multiple aviation attorneys).
As recently as July 2018, the FAA has re-emphasized their dominion over the National Air Space (NAS), meaning that the citizens of the United States own the NAS, with the FAA being the governing body. Municipalities, cities, and states may not abrogate nor preempt federal control over this airspace.
In general terms, once an aircraft is a theoretical “inch above the blades of grass,” it is in the NAS and subject to federal control, not state nor local control.
In general terms, an aircraft at rest/on the ground, may be subject to state or local regulation. Municipalities may control where an aircraft may launch or be recovered through regulation of public grounds. Municipalities should not govern launch/recovery on private property. That said, a few misguided municipalities have created regulation surrounding UAS launch/recovery in much the same way they have mandated that dog houses must meet a certain specification, or that small animals such as chickens may not be raised in certain zones.
We also are observing either blissful ignorance or a coordinated attempt at stifling commercial enterprise in the recent actions of the Uniform Law Commission (ULC), who have proposed national legislation creating “aerial trespass” regulation. These absurd notions have inspired the FAA to release the aforementioned press release regarding their dominion over the skies of CONUS. The National Press Photographers Association offered up a few words to the ULC as well. However, the ULC proposal is just that at this point; a proposal of legislation. It is not law, and unlikely to become such as currently written.
Taking a specific case in point; a property owner and their real estate agent hire a UAS pilot to capture aerial photos of a home coming onto the market. During the capture of these photos, the pilot’s aircraft is hovering over a neighbor’s home. The camera targets the for-sale home and at no point does the camera capture images of the neighboring home.
Does the neighboring homeowner have a right to demand the aircraft not fly over their home?
So long as the images being captured are of the home the pilot was hired to capture, the neighbor has no claim to control where the UAS flies. Moreover, there is little right to expectation of privacy should the camera capture ancillary areas of the neighbor’s yard (known in legal terms as “curtilage”).
Curtilage “is the area to which extends the intimate activity associated with the ‘sanctity of a man’s home and the privacies of life.’”71 As property owners may “reasonably . . . expect that [this] area immediately adjacent to the home will remain private,”72 the Court has found that curtilage is protected under the Fourth Amendment. Although the Fourth Amendment’s protections extend to curtilage, the Court has held that property owners do not have a reasonable expectation of privacy against naked-eye observation of curtilage from publicly navigable airspace. (Columbia Journal of Law)
Based on existing jurisprudence, warrantless drone surveillance of curtilage may not violate the Fourth Amendment if the drone operates within airspace legally navigable by drones. While this paragraph is predominantly related to law enforcement, it is reasonable to extend the concept into commercial/107 flights.
Homeowners have a right to an expectation of “reasonable privacy.” What is “reasonable” is a matter of debate. Sunbathing in the backyard next door to a home that has a deck higher than a fence, for example, would not be a “reasonable expectation of privacy.”
*it is important to note that the legal term “reasonable expectation of privacy” differs greatly from “right to privacy.”
Unfortunately, there is no Fourth Amendment right to privacy as relates to private citizens or commerce, leaving room for discussion and interpretation. Restrictions which law enforcement must follow in order to observe a property are very different from what a commercial UAS pilot must observe.
It is also a requirement in reading any law regarding privacy that may encompass law enforcement be accompanied by an understanding that law enforcement is held to a higher bar of respecting privacy than a citizen flying a commercial drone. Many states require warrants for any form of aerial surveillance, photography, or videography. Some states require additional certification for public safety officials/first responders, although this issue has recently been seen as a preemption and these requirements may quietly fade away.
IN GENERAL TERMS
The discussion regarding UAS photographing, mapping, or overlying a private home is fairly simple.
Regardless of whether the UAS is flying over a home, yard, easement, or other accessoral structures, a UAS pilot is well within their rights as granted by the FAA (discussion of waivers and airspace aside). So long as there are no MOA, TFR, or similar restrictions in place, the sky is a broadly accessible highway for aerial vehicles.
But…what about the UAS the hovers in a backyard and takes photos of sunbathing children? Doesn’t the FAA regulate this? Doesn’t the homeowner have “air rights?”
No to both questions.
-the FAA doesn’t govern what can/cannot be photographed.
-In theory, the homeowner has no so-called “air rights.” (The concept of “air rights” does exist, but is not related to aviation, rather relating to property views, sunlight blockage, etc, frequently found in large cities such as NYC or LA)
What the homeowner does have, is a potential claim of invasion of privacy. No different than a Peeping Tom putting a ladder on a fence and using the ladder as a photographic elevation, the aircraft’s violation of law is governed by state or local law, not federal law. Privacy laws vary from state to state. For example, in the State of Georgia, taking upskirt photos was legal until late 2017.
Each state has its own definition of “invasion of privacy” and there are no federal laws, and no FAA position on this topic. State laws tend to lean towards anything being under cover, or behind a fence as “private.” However, many state laws do not consider areas over a fence as being “private.” An example might be a two story home with a deck on the upper floor that over looks the neighbors yard. Several precedents have demonstrated that this is an “open view” and not an area that holds an “expectation of privacy.”
In most states, while privacy is a concern, any attempt to regulate “air rights of privacy” would be likely considered preemptive and the FAA has made it clear in recent months they are the controlling agency of aerial operations. The question becomes “at what altitude does the FAA relinquish ownership of the air and the property owner takes possession? Three feet? Ten feet? Eighty three feet? Or is it the theoretical 1” above the blades of grass?
The concept of privacy is not federal; it is local, and no commercial UAS pilot engaged in common, authorized activity such as surveying, mapping, photographing, a client property should hold any concern for this topic at this time. As we evolve from law enforcement situations into privacy situations, it is entirely possible that federal law may change in favor of creating some sort of regulation relevant to aerial invasion of privacy. The FAA has done an exemplary work in providing states with a basic fact sheet that should advise municipalities on what they may/may not regulate with regard to UAS use.
WHAT ABOUT AVIGATION? (air easements)
In the recent spate of social media word battle, one or two individuals brought up their expertise in “avigations.” Avigation is an easement generated for purposes of keeping the peace in areas where aircraft may be landing or taking off. Issues ranging from fuel dispersion, noise abatement, dust/debris, fumes, vibration, etc may impact a homeowner’s quality of life. These issues bear no relevance to UAV operations. Avigations frequently fall under categories of “hazard” and “nuisance.” These sorts of issues frequently precede condemnation actions. Only an airport may possess an avigation easement.
“Control” easements also exist, requiring property owners to restrict the height of buildings, trees, power poles, etc yet again, these easements are of no concern to UAS pilots.
BUT, BUT, BUT…WHAT ABOUT UNITED STATES V CAUSBY?
“Doesn’t that judgement say that property owners own the air up to 83’ above their home? That’s what a lot of websites say…”
Causby’s decision primary does exactly the opposite of what some may feel it controls. Causby demonstrates that airspace is within the public domain, but did NOT determine the quantity of curtilage left to the land owner. Even in the instance that some court somewhere determines that 100% of non-built up property is sacrosanct, Causby provides jurisdiction by the FAA, not state nor local authority. This is likely the most misunderstood of all legal decisions relating to aviation with regards to UAS.
It is of significant note to realize that currently, the vast majority of precedent decisions relate to law enforcement use of manned aircraft for purposes of surveillance. As society becomes more aware of issues surrounding privacy, federal legislation may eventually be enacted which restricts FAA control of the NAS. To date, there are three relevant cases to non-law enforcement uses of UAS.
Singer v Newton relates to private use of UAS, and is a District Court decision, affecting only areas within the State of Massachusetts, although it will likely be referred to in many courts to come. City of Chicago v Hakim determined that the local police had failed to meet a burden of proof in arresting a holder of an RPC for “flying over people.” Chicago v Hakim also demonstrates why the FAA must remain the sole arbiter and controlling agency over the skies. Similarly, City of Los Angeles v Chappell determined that Los Angeles municipal laws (MCS 56.31) were a preemption of FAA authority over the skies, although the code is similarly worded to FAA regulations found in Part 107 of the Code of Federal Regulations. In LA v Chappell, Mr. Chappell’s drone had been confiscated and he was charged with violation of municipal ordinances. It’s interesting to note that the last line of the ordinance nullifies the entire ordinance if the aircraft and operator are operating under permissions of the FAA. In other words, a holder of a 107 RPC could not be found in violation unless violating other FAA operational or airspace requirements. The courts found in his favor and his aircraft was returned.
Eventually, complaints will come before the Courts, and we’ll likely see an invocation of some form of legal statement, and perhaps case law, setting a precedent. For now, what we have are listed above. Change, is inevitable.
Aside from the legal implications and responsibilities, it is this author’s opinion that UAS pilots have an obligation to the community and each other to raise awareness of activities. Awareness can be raised through common practices such as wearing blaze orange or yellow hazard vests, putting up sandwich boards, marking launch/recovery areas with hazard cones, placing advanced notification handbills on front doors or mailboxes in the area of operations, notifying local authorities of operations, having vehicles marked as a commercial UAS vehicle, having a visual observer in place to communicate with anyone questioning the operation, and more. I believe it is incumbent on the professionals engaged in this infant industry, to help the general public learn to understand and accept our activities and see that it can be professionally practiced, vs the poorly dressed, angry guy that shows up with a small drone, launches from a sidewalk, and screams at the neighborhood about “his right to fly the drone anywhere he damn well pleases.” Being positive, firm, and informational goes a long way to helping concerned individual understand what a pilot is photographing, and allay fears of invasion of privacy.
Angry bystanders, homeowners, or property owners typically become angry due to fear, uncertainty, or doubt (FUD). Generally, they are uninformed. Politely and firmly providing educational information in a calm manner will generally allay their concerns. There will always be “that one person” who won’t accept what they’re being told, and situations may be escalated. Try to keep yourself calm. If authorities are summoned, have your relevant documentation available such as any waivers, RPC, etc. A recording of the altercation may be valuable.
Remember that the municipality *may* have determined authority over launch/recovery areas, so ensure public areas are always used for launch/recovery, or that the landowner has provided (preferably written) permission to launch/recover from their property.
At the end of the day, it is the responsibility of the UAS pilot to be familiar with all local and State regulations regarding UAS flight, and aware of what is and is not permissible. After all, being fully informed is but one facet of being a professional, wouldn’t you agree?
Relevant reading material:
California v. Ciraolo (1986)
Florida v. Riley (1989)
Los Angeles vs Chappell (2016/Chappell prevailed)
City of Chicago v Hakim (2017/Hakim prevailed)
Singer v Newton (2017/Singer prevailed)
As sUAV/drones become more and more popular, it seems that more and more of them are striking the sides of buildings, trees, or poles without the pilot understanding why.
“It was flying fine and all of a sudden it zipped up and into the side of the building.” “Everything was great until the drone had a mind of its own and flew straight to the ground.”
“The drone was flying over the trees and all of a sudden it spun around and dropped into the trees.”
Reading forum conversations around the internet suggests this is a common, yet unfortunate and avoidable experience.
First, let’s establish that flying in GPS mode may be ineffective when very close to a building. Signal may be lost, and this could explain a few of the building strikes.
However, far and away more likely in most instances the UAV was caught in a “rotor.” These are also known as up/down drafts, lee waves, or cross-winds, depending on which aviation discipline one adheres to. Needless to say, these phenomenon do exist, and play havoc with any sort of aerial activity whether it’s wingsuiting, parasailing, skydiving, model aircraft flight, swooping, small aircraft, and particularly light-weight multirotors.
THESE “WAVES” ARE INDICATORS FOR MANNED AVIATION AND CONSTRUCTION CREWS, YET THE PRINCIPLE IS
ONLY A MATTER OF SCALE.
Even when a manufacturer provides a statement of stability in “X” winds, this should not fool a pilot into thinking that the sUAS is turbulence-resistant. Given enough turbulence or infrequency of a wave, the UAV will become unstable.
It’s always better to be down here wishing we were up there, instead of being up there wishing we were down here.
The first rule is to set wind limits. Small quad-craft should stay on the ground at windspeeds of greater than 12mph/5.5 meters per second. Hexcopters should consider grounding themselves at 22mph/10meters per second. Of course, this figure may vary depending on your organizations policy and procedures manual, insurance requirements, or payload on the sUAS.
This video provides some demonstration of the cycle of the wave and how a gyro and accelerometer might cope with the cycles. Notice how all the aircraft are “cycling” in an attempt to maintain altitude and position, even as the waves of the wind rotate?
Truly, knowing about them is half the battle. Staying away from them is the rest of it. Failing the former, being able to manage the craft in turbulence is the next-best step.
A building blocks the wind on one side (windward side) and on the opposite side (leeward side) the wind will pay all sorts of havoc with any flying object. Winds will extend in distance up to four times the height of the obstacle, and two times the actual height.
40×4=160 feet. Therefore, for 160’ beyond the obstacle at ground level, your multirotor is at risk for catching either a down draft or an updraft.
OK, say there is a building that is 40 feet in height, and you have a medium wind blowing. Gusting or steady, it makes no difference.
40×4=160 feet. Therefore, for 160’ beyond the obstacle at ground level, your multirotor is at risk for catching either a down draft or an updraft. Either way, the airframe/hull is not in clean air. In extremely high velocities (high winds) the ratio of obstacle/distance may be as great as 15X (of course, a UAS would likely not fly in these winds)!
In terms of height, depending on wind velocity, the UAV may have to climb as high as 80’ to find clean air above an obstacle. yet at 80′ AGL, the winds are likely entirely different as well, depending on the weather and other obstacles in the area.
The air goes over the obstacle and is “pulled” to the ground (downdraft), where it then “bounces” upward (updraft) and tries to resume its level flow.
These phenomena are entirely independent of sinks,thermal rises, dust devils, and the like.
This also occurs in natural/unbuilt up areas. Trees, canyons, ridges, rock-lines; any large object will incur rotors. Avoid them. It’s virtually impossible to determine exactly where the down draft vs. the updraft may be occurring, and the location of these dirty winds will change with swind velocity.
FLYING IN URBAN ENVIRONMENTS
When wind flows between buildings, the mass of the air/gas is compressed. This results in an increase in velocity. Think of squeezing hard on a tube of toothpaste, compressing the contents through the tiny hole in the end of the tube. This increases the speed/velocity at which the toothpaste squeezes out. The same thing occurs with moving air between buildings or other solid objects.
Depending on the wind speed, the increase may require as much as 4-10 times the distance before the winds return to “normal” velocity seen before the gap or corner.
IMAGE COURTESY OF RHEOLOGIC
Ground winds and winds “aloft” (true winds aloft are beyond the reach of most UAS operations) are rarely equal. Winds at 50′ are rarely the same as winds at ground level in an urban or suburban environment. Even small berms in the ground can cause jarring turbulence (as shown above) that settle in the low areas. These urban “microclimates” can be very problematic for light weight UAS in required-precision environments.
Here is a more complex example of winds blowing at 22mph in an urban environment.
Compression of the flow due to building dynamics push the wind into more than 40mph in some areas. While the overall winds, and reported winds in the area suggest that the windspeed is perfectly acceptable for most commercial aircraft, turbulence and accelerated velocities within tight areas are far beyond the risk limits of most small UAS’.
Flying from warm sands to flying over water on a hot summer day may also create challenges to smooth and level flight.
Dust devils are summertime phenomena that can be very dangerous to humans anywhere a UAS may be flying. If they happen in a city, there is usually ample evidence of their existence, as debris flies high in the “funnel.” These nasty actors can show up anywhere there is hot asphalt, sand, dirt, and if that mass of rapidly moving air connects with a cool surface, they can turn violent very quickly, slinging a sUAS far from its intended flight path.
DUST DEVILS IN THE NEVADA DESERT CAN BE FRIGHTENING, ESPECIALLY WHEN TWO OR THREE COMBINE INTO ONE VORTEX.
If by chance a dust devil is seen climbing in the distance, prepare to bring the aircraft home and land. If the dust devil is anywhere near the vehicle, climb in altitude while moving in any direction away from the dust devil. They are usually very short-lived.
IMAGE COURTESY WASHINGTON POST
How do we avoid getting caught in turbulent air? The long answer is “experience.” Flying in these challenging spaces teaches us to find the lee, based on the behavior of the UAS, which will always be slightly latent to the wind.
The short answer is to study environments. Look at the wind indicators that might normally be missed. Learn to read the environment; it’s not hard once one begins to look for the details around buildings, trees, brush, monuments, chimneys, and other ground obstacles.
Two standard practices that may save pilots from troubles;
- Always use a windmeter/anemometer, and check the winds frequently in midday flights.
- Have a corporate or personal policy of a hard-deck/stop speed. This eliminates wishy-washy/should I/shouldn’t I decisions in the field. Our cap for teaching students with a Hexcopter/Yuneec Typhoon H is 16mph. If a gust crosses 16, we immediately stop, and wait it out to determine the wind trendline.
Another practice (although not standard) is to put a 5′ stream of crepe’ paper on a stick at eye level or so. This WDI, or Wind Direction Indicator, will immediately demonstrate changes in windspeed or direction, both clues that the weather may be rapidly shifting.
Determine distances from obstacles as accurately as possible prior to flight in order to best understand where the rotors will occur. Doing so goes a long way to maintaining control and safety when the drone is in flight. With a bit of experience, one rarely needs to worry about obstacle turbulence.