NASA Performs First Aircraft Accident Investigation on Another World

Engineers from NASA’s Jet Propulsion Laboratory in Southern California and AeroVironment are completing a detailed assessment of the Ingenuity Mars Helicopter’s final flight on Jan. 18, 2024, which will be published in the next few weeks as a NASA technical report. Designed as a technology demonstration to perform up to five experimental test flights over 30 days, Ingenuity was the first aircraft on another world. It operated for almost three years, performed 72 flights, and flew more than 30 times farther than planned while accumulating over two hours of flight time.

The investigation concludes that the inability of Ingenuity’s navigation system to provide accurate data during the flight likely caused a chain of events that ended the mission. The report’s findings are expected to benefit future Mars helicopters, as well as other aircraft destined to operate on other worlds.

Flight 72 was planned as a brief vertical hop to assess Ingenuity’s flight systems and photograph the area. Data from the flight shows Ingenuity climbing to 40 feet (12 meters), hovering, and capturing images. It initiated its descent at 19 seconds, and by 32 seconds the helicopter was back on the surface and had halted communications. The following day, the mission reestablished communications, and images that came down six days after the flight revealed Ingenuity had sustained severe damage to its rotor blades.

“When running an accident investigation from 100 million miles away, you don’t have any black boxes or eyewitnesses,” said Ingenuity’s first pilot, Håvard Grip of JPL. “While multiple scenarios are viable with the available data, we have one we believe is most likely: Lack of surface texture gave the navigation system too little information to work with.”

The helicopter’s vision navigation system was designed to track visual features on the surface using a downward-looking camera over well-textured (pebbly) but flat terrain. This limited tracking capability was more than sufficient for carrying out Ingenuity’s first five flights, but by Flight 72 the helicopter was in a region of Jezero Crater filled with steep, relatively featureless sand ripples.

One of the navigation system’s main requirements was to provide velocity estimates that would enable the helicopter to land within a small envelope of vertical and horizontal velocities. Data sent down during Flight 72 shows that, around 20 seconds after takeoff, the navigation system couldn’t find enough surface features to track.

Photographs taken after the flight indicate the navigation errors created high horizontal velocities at touchdown. In the most likely scenario, the hard impact on the sand ripple’s slope caused Ingenuity to pitch and roll. The rapid attitude change resulted in loads on the fast-rotating rotor blades beyond their design limits, snapping all four of them off at their weakest point — about a third of the way from the tip. The damaged blades caused excessive vibration in the rotor system, ripping the remainder of one blade from its root and generating an excessive power demand that resulted in loss of communications.

Although Flight 72 permanently grounded Ingenuity, the helicopter still beams weather and avionics test data to the Perseverance rover about once a week. The weather information could benefit future explorers of the Red Planet. The avionics data is already proving useful to engineers working on future designs of aircraft and other vehicles for the Red Planet.