‘Pilot error’ is often used as a tool to obscure the actual root causes of fatal military aviation mishaps.

November of 2023 — Yakushima Island, Japan

On November 29, 2023, a CV-22 Osprey callsign GUNDAM-22 crashed roughly one half mile off the coast of Yakushima Island, Japan. Eight special operations airmen were killed.

There are a few things working together to make the Japan Osprey crash a compelling and interesting case study from a narrative management perspective in assigning pilot error:

1. The narrative is transparent.
2. Experts quickly refute the narrative.
3. There are broader systemic failures that would incentivize the narrative.

The Air Force version of the Official Report is called an “AIB”. The Official Report for the Japan crash ultimately lists two causes:

1. Catastrophic Failure of the Left-Hand Proprotor Gearbox
2. Pilot Decision Making.

Both are presented as having contributed to the mishap equally. However, most of the Official Report’s contents are dedicated to bullet #2: Pilot Decision Making.

The following is a summary of the Official Report’s findings:

AIB CONCLUSIONS

I found, by a preponderance of the evidence, the Lead Pilot’s decisions were causal, as they prolonged the mishap sequence and removed any consideration of an earlier landing at a different divert location. Specifically, the Lead Pilot’s decision to continue with the mission after the third chip burn advisory, when the situation became Land as Soon as Practical…

And the Lead Pilot’s decision to land at Yakushima Airport, instead of closer locations after the PRGB CHIPS caution posted, when the situation became Land as Soon as Possible, were causal.

The Lead Pilot and Crew did not plan for, deliberate, or even discuss closer suitable landing options after the “L PRGB CHIPS” caution posted.

In addition, I found, by the preponderance of the evidence, the following factors substantially contributed to the mishap:

(1) Inadequate Risk Management; and (2) Ineffective Crew Resource Management*.*

Why Did Experts Dispute The Official Narrative?

A unique and rare aspect of the Japan Osprey crash is the unprecedented speed in which qualified experts from the military publicly contested the Official Report. It took less than a week.

The Short Answer:

The guys onboard GUNDAM-22 were dealt an impossible hand.

The crew did what they were trained to do — but they had no idea they were playing a game where the rules had suddenly and invisibly changed until it was far too late.

Other CV-22 Pilots:

“I can’t say I would have done anything different.”

Retired Marine Corps Lt. General Steven Rudder:

“As far as I know, this crew did all the right things. I would offer, for a Marine crew, I can’t say whether they would have done anything different.”

The Non-Public Mishap Investigation:

“Based on interviews, we determined the pilot enjoyed a sterling reputation within his squadron. He was highly respected for superior judgment.”

Hindsight fallacy is the deliberate misuse of outcome knowledge to unfairly judge past decisions, creating an illusion of predictability and assigning unwarranted blame.

The Long Answer:

To fully understand why experts and pilots dispute the Official Report’s findings blaming the pilot and crew of GUNDAM-22, some additional context is helpful.

There are three tiers of landing conditions that may occur in-flight:

1. Land as Soon as Practical — least severe
2. Land as Soon as Possible
3. Land Immediately — most severe

There are four tiers of notifications that can be presented to a V-22 crew in-flight:

1. Advisory — least severe; the only one without an audible caution tone
2. Alert Advisory
3. Caution
4. Warning — most severe

In each proprotor gearbox (PRGB) of an Osprey, there are three magnetic chip detecting sensors. They are capable of triggering the following alerts:

1. [CHIP BURN] (advisory) — the sensor detected something miniscule, e.g. “fuzz” in the gearbox, but the sensor was able to burn it off with one of up to three short pulses of electricity.
2. [PRGB CHIPS] (caution) — the sensor detected something magnetic that was too big to burn off.
3. [CHIP DETECTOR FAIL] — the sensor itself has malfunctioned.

For context on the mission itself, this is not a routine training exercise consisting solely of three CV-22s. It is the largest airborne joint forces exercise of its kind ever conducted in its area of operations to date, near the East China Sea. The lead pilot of GUNDAM-22 is also the Airborne Mission Commander for the exercise. Aside from having planned the mission, he is responsible for coordinating its execution from the air.

Dissecting the Official Report

There are primarily four reasons the Official Report gives for citing pilot error:

1. The crew inadequately assessed the risk of their situation.
2. The lead pilot pressed on after three chip burns.
3. There were closer landing locations after the PRGB CHIPS warning.
4. The lead pilot waited for runway traffic at Yakushima.

1. The crew inadequately assessed the risk of their situation

The bolded statement above is incomplete. It should read:

The crew inadequately assessed the risk of their situation because the risk was fundamentally unknowable until after the crash that occurred on November 29, 2023, when GUNDAM-22’s left-hand gearbox failed catastrophically in a way that no one had anticipated, prepared, or trained for. This is reflected by the resulting dramatic changes to policies, procedures, and training made after-the-fact.

Before the Japan crash, chip burns were not considered to be a primary indicator of impending catastrophic gearbox failure. Chip burns alone had only ever been false alarms or events with uneventful endings, and crews were trained to corroborate them with secondary indicators.

This is reflected by the only official guidance about them being:

• Three (or more) [CHIP BURNS] = Land as Soon as Practical.

However, after the Japan crash, chip burns are now known by operators to be a potential primary indicator of an impending catastrophic gearbox failure. This is reflected by their new official guidance:

• One [CHIP BURN] = Land as Soon as Practical.
• Two [CHIP BURNS] = Land as Soon as Possible.

Additionally, a [CHIP BURN] is no longer classified as an ‘advisory’, and they now trigger an audible caution tone.

Importantly, at no time did the crew of GUNDAM-22 ever violate any official guidelines, rules, policies, or procedures.

It would be factual to state that the crew’s actions were by-the-book. It would be factual to state that the crew did what they were trained to do. Finally, it would be factual to state that, due to an extremely unfortunate set of circumstances, the crew was made to encounter the symptoms and eventual manifestation of an insidious, novel mechanical failure that nobody at the time could have been fully prepared to handle because the information to do so was not made available to CV-22 operators.

Considering that, it becomes difficult to view the Official Report’s indictment of the crew’s decision-making and ‘risk assessment’ as being grounded in good-faith judgment.

It is challenging to rationalize the Official Report as anything other than being made through the lens of hindsight fallacy, judging the crew by the new standards and insights resulting from the crash versus what was known to them on November 29, 2023.

Again, chip burns are not yet considered to be a primary indicator of an impending catastrophic gearbox failure.

It would have been completely reasonable for a CV-22 Airborne Mission Commander in the pilot’s position to have chosen not to divert for a three-chip-burn Practical without any secondary indicators on November 29, 2023. Remember, this is a large-scale exercise months-in-the-making in which the lead pilot is responsible for coordinating and executing from the air. At the time, just about any Airborne Commander of such an exercise would likely choose to cautiously continue the mission with a ‘Land as soon as Practical‘ given the circumstances, considering there were no corroborating symptoms.

That’s not to suggest the pilot and crew are motivated by some primal drive to complete the mission — choosing to press is a calculus.

For example, a Pilot would be most willing to press while down range in a hostile environment, and least willing to press in a truly run-of-the-mill routine training exercise. In this case, willingness to press would probably land somewhere in the middle. Pressing here was a reasonable call given the perceptible risk (at the time) was low.

In contrast to the Official Report’s description of the dialogue, it is clear from the transcripts that the crew does indeed take the chip burns seriously, and the pilot does indeed explain his rationale for pressing:

1. Diverting is not without risk because GUNDAM-22 has the SOFME personnel onboard in case of a medical emergency during the day’s planned exercises.
2. The crew has been carefully monitoring for any corroborating secondary indications of a mechanical issue and there are none.
3. The chip burns are occurring with no discernable trends in frequency that one might expect in the case of an underlying mechanical issue (e.g. the first two were ~20 seconds apart and the third was 12 minutes later).
4. The crew is going to continue to closely monitor for any kind of secondary indications and pull back if they need to — they radio GUNDAM-21 that if they suddenly split off, it’s because they moved to “Land as Soon as Possible” conditions.

Regardless of the decision to press, the crew only does so for about 15 minutes before having to divert. Along the way, they are never more than 15 minutes from their planned divert location.

It is also worth thinking about what might have happened if the crew did choose to land at Kanoya Air Base after three chip burns, and if they did so without incident. At Kanoya, GUNDAM-22’s left-hand PRGB would be a ticking bomb. Regarding the failed part, the Air Force says:

“In the field, there’s nothing we could have done to detect this. The gearbox is a sealed system, meaning ground crews on base can’t open it to inspect the gears.”

Even if GUNDAM-22 had diverted after three chip burns, avoiding tragedy wasn’t guaranteed. Consider this arguably unlikely (but not impossible) sequence of events:

1. Maintenance doesn’t simply perform a standard gearbox drain-and-flush with a 30-minute ground run.
2. They somehow correctly diagnose an unprecedented, imminent catastrophic gearbox failure.
3. They determine it’s unsafe to fly the aircraft at all.
4. They refuse to fly the aircraft for further diagnosis or to return to base.
5. They decide to replace the entire left-hand proprotor gearbox at the foreign Japanese airport.

While this series of fortunate events could have saved GUNDAM-22, it wouldn’t address the root problem: high-speed pinion gears were not recognized as single points of catastrophic failure.

To prevent any such high-speed pinion gear tragedies in the future, the Osprey Program would need to:

1. Update relevant policies and procedures, reclassifying high-speed pinion gears as single points of catastrophic failure.
2. Implement more stringent inspection and replacement schedules for the high-speed planetary components.
3. Revise guidance on chip burns and chips to reflect their potential as indicators of impending catastrophic gearbox failure.

Without a tragedy, the odds of this series of fortunate events is essentially zero. The Osprey program deliberately chose not to test for the failure characteristics of the high speed planetary gears and had no plans to do so. As a result, they were tested in-flight by unwilling participants and the results were disastrous.

The Official Report suggests the crew of GUNDAM-22 was unaware that closer places to land existed upon receiving the [PRGB CHIPS] caution, and as a result, they chose a divert location that was needlessly far away.

When GUNDAM-22 gets [PRGB CHIPS], the crew immediately changes course to their planned divert location at Yakushima Island, roughly 15 minutes away.

At this point, it is crucial to remember that there are zero perceptible indications to confirm that something is actually very seriously wrong, and again, at this point, chip burns are not considered a primary indication of impending gearbox failure.

Regarding point #3 from the Official Report, it is just as likely the pilot knows that closer divert options do technically exist (the crew talks about flying around one of them having volcanic activity in the transcripts). The pilot would know this from having explicitly chosen a divert location while considering all possible divert locations while planning the mission.

There are two relevant criteria that a pilot would use to select a divert location:

1. Not logistically problematic.
2. Not politically problematic.

Logistically, the pilot knows the chosen location must accommodate the landing, maintenance, and subsequent takeoff of both their aircraft and the maintenance aircraft that will rendezvous.

Politically, the exercise is taking place in a sensitive area. The pilot would not want to choose a divert location where landing unexpectedly might cause tension or unintended consequences unless necessary. Additionally, it’s no secret the Japanese are highly skeptical of the V-22 Osprey, and any time one lands unexpectedly, it ends up in the news.

Like many decisions in aviation, ‘Land as Soon as Possible’ is still ultimately a judgment call where trade-offs exist. It’s just as likely the pilot knows about the other landing locations, but they would have been poor choices given his calculus based on known circumstances.

It’s also crucial to understand that [PRGB CHIPS] had never before graduated to catastrophe as quickly as they were about to.

One airmen told investigators after the crash:

“Before the crash, I didn’t think prop box chips were going to change into a lost rotor system as rapidly as it seems like it might have,” before adding that the investigation results would likely “change the calculus on how I handle a proprotor gearbox chip.”

So as GUNDAM-22 is flying totally normally with no secondary indications of trouble, what rationale exists for pushing for a landing five minutes earlier at a comparatively problematic location? At the time, doing so would arguably be more unusual than not. Why exchange minutes of flight time for the potential of hours of logistical or political headache and an ear-full later on?

Unless you already know the outcome.

4. The pilot waited for runway traffic at Yakushima.

The Official Report states that the lead pilot’s decision to wait for runway traffic at Yakushima was also causal to the crash.

First, the plane on the runway at Yakushima appears to be preparing to take off in the direction that GUNDAM-22 will come in for landing.

From the transcripts, the pilot says:

“Yeah, I don’t want to land right in front of him. Our situation is not that dire.”

The pilot doesn’t see the potentially dangerous maneuver of landing directly in front of another aircraft that’s headed towards them as being justified. This decision adds not more than two minutes of flight time.

Seconds after acknowledging the aircraft on the runway, the crew receives a notification that their chip detecting sensor has failed. The aircraft is now telling the crew that the same sensor that has been posting the asymptomatic notifications for the last ~46 minutes is actually faulty.

Now, the pilot appears to have explicit confirmation that their decision to wait for the plane at Yakushima will not be exposing their aircraft to further degradation. In response, the Pilot says:

“Oh, chip detector fail, that sounds more accurate.”

Even so, the pilot and crew are still taking the [PRGB CHIPS] seriously. The Flight Engineer reminds the pilot they still have the Chips warning, and the pilot responds by saying they are still going to honor it — like they should.

However, what was actually happening with the chip detector was it had accumulated enough chips that it shorted, causing a [CHIP DETECTOR FAIL].

Tragically, a chip detector reporting itself as failed due to excessive chips was not an unknown behavior to the V-22 Osprey community at the time. This was already discovered by a branch of the military that flies the Osprey, and crews from that branch were trained to treat it as a secondary indication of impending gearbox failure when paired with [PRGB CHIPS].

Unfortunately, the Air Force was not that branch.

GUNDAM-22 had no way of knowing about this phenomenon because the Air Force’s Technical Orders (their guidelines for aircrews) said absolutely nothing about it. Had the pilot been aware of this behavior, it would have been the crew’s first perceptible secondary indication that a serious problem had been manifesting. Instead, the calculus for landing in front of the plane waiting at Yakushima was made using needlessly incomplete information. The relevant Technical Orders were quickly updated after-the-fact.

The other point of contention with #4 is the implied guarantee that it was the seconds or minutes that were the actual deciding factor in the mishap given that GUNDAM-22’s gearbox failed so close to landing. However, this is not at all a certainty.

To understand why, it’s helpful to watch the re-creation video of the moments before the catastrophic failure which the Air Force created with their simulator:

The aircraft had been flying normally without any perceptible indications of a mechanical issue for roughly 45 minutes. However, while rotating their nacelles for landing, GUNDAM-22 experiences the rapid succession of cascading mechanical failures which led to disaster. Why is that important?

Another possible cause of why the failure occurred when it did is increased gearbox torque. It’s not news that the torque loads experienced by the Osprey’s gearbox are substantially different in airplane mode versus in helicopter mode and at the different angles of nacelle rotation between.

After the crash, multiple recommendations were made to start training pilots on gearbox torque management when a [PRGB CHIPS] caution is present. These recommendations include lowering airspeed, avoiding speed changes, avoiding time spent in conversion, and avoiding landing in VTOL mode (like a helicopter). The goal of the recommendations is to decrease the torque load experienced by the gearbox. It is very possible that rotating the nacelles and the partial conversion to helicopter mode for landing is what ultimately triggered the rapid succession of cascading failures due to increased torque load on the failed gear.

Trial By Public Execution

It should be clear that the Official Report is not necessarily a reliable single-source-of-truth regarding the true reality of military aviation mishaps. They are often used as a tool for shaping cherry-picked information into a public-facing narrative.

In the case of the V-22 Osprey, when any degree of pilot decision-making exists in a deadly mishap, statistically, the narrative has proven to be ‘pilot error‘ 100 percent of the time.

Unfortunately, being unreliable does not equate to being ineffective. Pilot error is too easy of a story to sell.

When the media embargo was lifted for the Japan Osprey crash on August 1st, 2024, the Associated Press was the single big-name primary source to break the story.

The original article was mostly dedicated to descriptions of the pilot’s actions, calling him out by name. It took the Official Report even a few steps further, and and depicted a respected aviator as negligent and reckless for the sake of sensationalism, clicks, and views.

Unfortunately, being incorrect also does not equate to being ineffective — the AP’s story dominated the news cycle. Many other news organizations simply purchased the rights to their story and reposted it, further spreading disingenuous misinformation about the pilot and crew of GUNDAM-22.

Days later, someone made a video narrating the Official Report set to images from the report. The comments are a glimpse into how information about the Japan crash and the Official Report were perceived by the public.

The pilot error narrative isn’t free: pilots are killed twice. First, they die physically, and next, their legacy.

This is the price gold star families pay to ensure the larger failures that incentivized creating the narrative in the first place don’t get too much unwanted attention.