A frayed wire likely triggered stray voltage to shut off fuel valve, causing the catastrophic loss of an MQ-9 Reaper drone last August, according to a new Air Force investigation report.
The aircraft, valued at $23.6 million, was destroyed in place. It is among at least 40 MQ-9s lost or shot down over the past 18 months.
Air Combat Command released the Accident Investigation Board report on Aug. 13, nearly a year after the Aug. 31, 2025, mishap. The exact location of the mishap was not disclosed—the report said only that it took place in the U.S. Central Command area of responsibility.
The MQ-9 belonged to the 432nd Wing at Creech Air Force Base, Nev., while the pilot and sensor operator were from the 89th Attack Squadron at Ellsworth Air Force Base, S.D. The drone was returning from a mission to its base in the region and had been in the air nearly 19 hours when the engine shut off.
The drone automatically attempted to restart the twice, and the crew tried two manual restarts as well before the Reaper crashed to the ground. Operators tried for a soft landing to preserve the aircraft but were not successful.
After sorting through several options to avoid population centers and minimize damage, the crew selected a “relatively flat and isolated” piece of desert and tried to go in with the landing gear down, according to the report. But the crew lost contact with the aircraft as it descended below 2,000 feet.
The Reaper landed near the selected landing area, but “the force of the impact caused its landing gear to collapse,” according to the report. “Following the landing, sensitive equipment was removed from the [aircraft] and the remaining wreckage was demolished on site.”
The problem occurred on the aircraft’s first flight after its engine was replaced as part of a routine 3,000-hour engine inspection. During that inspection, personnel from contractor Honeywell noted three issues beyond normal wear:
- The propeller governor cable was chafed and replaced
- The fuel control unit was replaced with a new unit overhauled in April 2025, due to a missing log card
- The compressor seal was leaking and replaced
Notably, the inspection and replacement routine did not include removing the top cover from the fuel control unit, which regulates the flow of fuel to the engine—despite “known examples of the FCU sensor wire chafing,” according to MQ-9 manufacturer General Atomics. Honeywell personnel reported they had observed “a relay wire shorting and sparking” while servicing a different aircraft.
Based on data logs, investigators determined the MQ-9 engine experienced a spike in fuel flow just before plummeting to zero. General Atomics was able to recreate that sequence in its lab by suddenly closing the electrical fuel shutoff valve.
Those tests combined with the known issue of the wires chafing inside the fuel control unit led investigators to conclude the most likely explanation for the mishap was that a frayed wire inside the fuel control unit leaked enough voltage to trigger the the fuel shutoff valve to close.
The board noted that while most U.S. Air Force aircraft are required to undergo some sort of check flight after their engine is replaced “to ensure the aircraft is airworthy and to test the flight integrity of all systems, particularly critical systems like those affecting engines,” the MQ-9 maintenance manual has no such requirement, the board said.
What’s more, investigators noted surprise that a complete engine change is considered “routine maintenance” on MQ-9s, and that the crew controlling the drone was never informed that their aircraft had just received an entirely new engine.
The Accident Investigation Board cited inadequate planning and briefing and inadequate written standards as “relevant factors” in the mishap.
MQ-9 Losses
The MQ-9 mishap occurred during a relative lull in operations in the Middle East. Just months earlier, from March to May 2025, Operation Rough Rider sought to halt attacks on commercial shipping by Iranian-backed Houthi rebels in Yemen. The Houthis downed about a half dozen MQ-9s during that stretch using electro-optical/infrared surface-to-air missile systems, Air & Space Forces Magazine previously reported.
At least two dozen MQ-9s were subsequently lost during Operation Epic Fury against Iran in late February. In the six months since, several dozen MQ-9s, some to air defense missiles and some struck on the ground.
By May, after a brief ceasefire took hold, the Air Force was down around 30 Reapers, Air & Space Forces Magazine reported. Hostilities began again in earnest by July, and the Washington Post reported last week that “at least 45” MQ-9s have been destroyed.
The Air Force reported having 230 MQ-9s in its inventory at the start of fiscal 2025; one year later, it had just 182. In May, Lt. Gen. David Tabor, Air Force deputy chief of staff for plans and programs, said the fleet was down to around 135 aircraft.
Air Force officials have praised the performance of the MQ-9 in the Iran conflict, saying it has accounted for many of the thousands of strikes conducted during the campaign and gathered valuable intelligence. Some have also hinted that commanders have sometimes employed them in ways that put the drones at greater risk.
With the fleet shrinking, leaders are discussing how to replace the losses. Options include acquiring the few remaining MQ-9As from General Atomics, buying the larger MQ-9Bs now being built, or developing replacement platforms. Among the alternatives backed by some on the Air Staff is a project jointly pursued by the Defense Innovation Unit and the Air Force. The so-called “massed modular aircraft,” or MMA is conceived as an “attritable” aircraft whose loss is treated more like a munition than a aircraft. Vendors have offered proposals and an acquisition official said in July that one or competitors could be selected by the end of 2026.