Can traditional aerial photogrammetry survive in the era of uncrewed aviation?
On December 11, 2024, a photogrammetry aircraft registered N818BR made an unscheduled forced landing on a busy highway in the vicinity of Victoria, Texas. The pilot survived with minor injuries, three cars were hit with occupants suffering minor injuries, too. The aircraft was destroyed.
At the beginning, it sounded like just another case of a pilot making the difficult decision to land on a paved road after an inflight emergency. As details emerged and the National Transportation Safety Board (NTSB) published its preliminary report, we found out that it was a photogrammetry aircraft owned and operated by Marc Inc., a Bolton, Mississippi-based contract flight services company that according to their website is “North America’s largest provider of specialized contract aircraft and flight crews for airborne GIS, survey and surveillance projects.”
The initial cause of the accident, according to interviews with the pilot by NTSB officials, was fuel exhaustion. The Piper Navajo was supposed to carry 236 gallons of fuel, but apparently the pilot failed to do a comprehensive fuel level inspection as part of the mandatory pre-flight.
The mission flown was a basic photogrammetric flight with long lines (about 60 miles each) oriented northwest to southeast, a few miles southeast of San Antonio, Texas. According to the authorities and public flight data, the flight took more than five hours, right on the limit of the Piper Navajo. The mission started at 9:52 a.m. central time and ended at 02:57 p.m., exactly five hours and five minutes.
The takeoff point, grid flown, and crash point of a photogrammetry mission in Texas.
On January 21, 2025, the NTSB published its final accident report and in it states the cause of the accident, “The pilot’s inadequate preflight planning and preflight inspection, which resulted in a total loss of engine power due to fuel exhaustion.”
So, what happened? The NTSB report states that, “The local aerial survey flight was flown at 16,500 feet mean sea level (msl) and lasted about [five] hours.” Which means that it was a perfect day and the pilot, the sole occupant of the aircraft, decided to stay aloft as much as he could and cover as much of the survey area as possible.
For those of us who fly photogrammetry flights, especially those missions conducted in complex aircraft (multi-engine and retractable landing gear), the pressure of taking advantage of clear, cloudless days is always there. The temptation to fly just another line that has eluded us for weeks and perhaps months, is omnipresent.
And it is here that we would like to make an analysis of the market conditions today in comparison to 10 or 20 years ago, when the marketplace for these types of missions was different, and the competition did not involve small, non-piloted aircraft.
Traditionally, a photogrammetric flight involved a pilot, a copilot, a navigator, and a camera operator. In countries where governments were concerned about rogue aircraft taking vertical photographs of sensitive installations, such as military bases and government sites, these flights also had onboard a military supervisor who made sure no pictures were taken of such facilities.
The last mission of N818BR was conducted with just one person onboard performing the tasks of piloting, navigating, and operating the camera. How is this possible? Well, the simple answer is automation. Let us analyze the three aspects of every photogrammetry flight to understand the reality of today.
Piloting: In the days before the normalization of Global Positioning Systems (GPS), photogrammetry flights were conducted using pilotage (navigating by reference to visible landmarks) and dead reckoning (calculating position based on time, airspeed, and direction). These aeronautical tasks are complicated enough when we are flying traditional missions to go from Point A to Point B, but on photogrammetry flights, navigating while aviating gets particularly difficult, and that is why we use two pilots, one to make sure the plane was level and at a constant speed during the actual photographing of lines and the other to make sure that the aircraft is clear of obstacles and other aircraft in accordance with Visual Flying Rules or VFR.
Camera Operation: In the old days when cameras were analog, it was impossible for a pilot to change the photographic roll during flight, therefore the presence of an experienced camera operator was imperative. On top of this, the crabbing of the camera to adjust for lateral wind had to be done manually, forcing the crew to untighten a bolt, turning the camera in the right direction in coordination with the navigator and tightening again.
It was tedious work but given the noise and the length of the flight it was intensive, exciting, and definitely a team effort. As soon as the airplane aligned with each new line, the camera operator, in coordination with the navigator, determined the crab and adjusted the camera. Each line is different, even by minute margins.
Navigation: The navigation for aerial photogrammetry is radically different to the traditional navigation used to get to the site. Pilot and copilot used traditional VFR methodology to arrive at the mission site and then delegated the navigation responsibility to the photogrammetry navigator who normally flew in the back of the cabin close to the camera operator. Some aircraft were equipped with a vertical periscope that allowed the navigator to see the ground directly through a lens.
In all cases, the photogrammetry navigator had a paper map in which the lines were painted in thick lines, preferably red, to indicate the position and length of each one and the separation necessary to comply with lateral overlap. The navigator identified features on the terrain and instructed the pilot to turn either left or right and then to align with the next target line. By looking through the window or using the periscope, the navigator gave precise instructions to the pilot during each line to make sure the camera was taking photographs over the correct alignment.
The remains of the crashed Piper Navajo, which broke in half upon an emergency landing on a highway.
Now that we understand the complexity of the analog years, let us jump a few decades to December 2024 when a single person can do all of that using automation.
First, aircraft today are heavily automated and use GPS and autopilots to perform most tasks except takeoff and landing, therefore the absolute need for a copilot has evaporated and some companies use a second pilot as a safety measure, but it is no longer a must-have.
Second, cameras are now digital and automated, so they can be operated from a central console in the cockpit by just operating a few switches and monitoring a few indicators on a screen, so the need for a dedicated camera operator has also vanished.
Third, photogrammetry navigation today is also managed by the aircraft GPS and sometimes, to add precision, a second GPS antenna, this time a geodetic device is added to the aircraft to turn the GPS signal precision to a few yards instead of a quarter of a mile. This precision is accomplished by adding a screen with dedicated software in which the lines of the mission have been programmed and all the pilot needs to do is to align the aircraft in straight and level flight with the entrance to each line, and the software and the autopilot will do the rest.
In short, automation has reduced the crew of four to a crew of one. Unfortunately, an unintended consequence of this drastic 75 percent personnel reduction is that there are no dissenting voices during a flight. In clear, cloudless, perfect days, the temptation to fly one more line when the fuel begins to look low is high. This is when a copilot or a navigator or a camera operator might offer some advice and make the pilot think twice before committing to a course of action that might end in a forced landing on a highway.
Perhaps this was the case of N818BR on December 11, 2024, or perhaps it was something else. But every indication of the accident and the subsequent investigation from the FAA and the NTSB point to a flight that was stretched to the limits of the aircraft. Just deciding to go back to the airport, after the previous-to-last line would have given the pilot plenty of time and fuel to land, refuel and return to the site.
The “why” this happened is a bit more complicated. Aerial photogrammetry companies today are under tremendous pressure from cheaper alternatives such as drones and smaller aircraft to reduce costs in order to remain competitive. But placing the public at risk by landing on a busy highway is too much. Perhaps insurance companies can demand a second pilot on board, leveling the playing field for all companies.
One thing is clear, when the decision to fly that final, fateful line was made, there were no dissenting voices and that created a series of events that culminated in the destruction of the aircraft, possibly the camera, and the injury of the pilot and people on the ground.
This accident should give the industry pause.
