All The Ways The F-35 Tried To Kill Its Pilot Prior To Eglin AFB Crash
The pilot of the U.S. Air
Force F-35A stealth fighter that crashed at Eglin Air Force Base in Florida this past
summer struggled with an extraordinary catalog of problems before he ejected
from the jet. Though high-landing speed was determined to be the key culprit,
issues with the pilot’s helmet, the aircraft’s oxygen system, and the software
behind the jet’s fly-by-wire flight control system all contributed to the
accident, according to a recently released official report.
The F-35A from the 58th Fighter Squadron, the
“Gorillas,” part of the 33rd Fighter Wing, crashed upon landing at the Florida
base on May 19, 2020, after a routine night-training sortie. It was the second
crash of a stealth fighter operating out of the base in less than a week,
following the loss of an F-22 Raptor on May 15, and the two accidents led to a
“safety pause” on flying operations at the base.
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In its conclusion to the report, the Accident
Investigation Board President, Colonel Bryan T. Callahan, makes it clear that
no fewer than six factors led to the loss of the F-35.
The key factor to come out of the investigation
was the fact that the pilot was attempting to land the Lightning II at an
excessive speed. However, the tail was also unresponsive due to a problem with
the flight-control logic that wasn’t widely known up to that point.
There are other disturbing issues outlined in the
final report, among them numerous errors made by the pilot — a qualified
instructor who was flying as lead for the two-ship training sortie — in the
run-up to the crash. The aviator was fatigued, in part due to issues with the
jet’s “on-demand” oxygen system, leading to “cognitive degradation,” while a
misaligned helmet-mounted display meant that he was distracted at a critical
point, as well.
After ejecting, the pilot sustained
non-life-threatening injuries and was transported to the 96th Medical Group
Hospital for evaluation and monitoring.
U.S.
AIR FORCE/SENIOR AIRMAN CASSIDY WOODY
Weapons load
crew from the 33rd Fighter Wing prepare an F-35A at Eglin Air Force Base,
Florida.
Exactly how the third F-35 crash unfolded is worth
looking at in more detail, with a close examination of the accident report.
At the controls of the F-35A in question, serial
12-005053, the mishap pilot (MP) maintained a steady speed of 202 knots on the
approach — this was correct for this phase of flight, but would be a major
contributor in the accident later on. Meanwhile, problems were beginning to
make themselves known, distracting the pilot from the task at hand.
First, the pilot noticed
that his helmet-mounted display (HMD) seemed to be misaligned in relation to
the horizon. The F-35 does not have a traditional fixed head-up display (HUD), as found on a
typical legacy fighter, but instead projects that data directly onto the
helmet’s visor. The Joint Strike Fighter has had issues in the past with its HMD,
including with the alignment and clarity of the information
presented.
“The MP was fixated on the faulty symbology of the
HMD at a critical phase of flight to the exclusion of a crosscheck of either
AOA or airspeed,” the report noted.
As well as the misalignment, the pilot was
struggling with what seemed like excessive brightness, making it more difficult
to focus. This was a result of the “green glow” phenomenon in the cockpit,
created by the HMD’s projection brightness, and now made worse since it was combined
with local humidity. “The [pilot] reported having to squint through the green
glow in order to pick up on the environmental cues in the runway environment,”
the report stated.
After checking the virtual head-up display against
data from the instrument landing system, he then adjusted his aim point and
glideslope as the jet neared the runway threshold.
U.S.
AIR FORCE
A
representation of an aligned HMD.
U.S.
AIR FORCE
A misaligned
HMD with left-to-right crosswind, “Green Glow,” and aim point in the “black
abyss.”
Available data indicated to the pilot that the
fighter’s glide path was too high, and the jet’s attitude needed correcting,
being too nose-down for a landing. In his efforts to correct this, the
misaligned display readings became even more confusing.
The accident report identified the HMD
misalignment as the “critical confounding item that ultimately resulted in
over-saturation” of the pilot. It records the fact that the pilot had previously
experienced misalignment with the HMD, and maintainers had addressed these
issues on the ground, but, without modifications, there was no way of checking
alignment once in the aircraft.
In addition, the pilot had never experienced this
HMD error before at night, let alone during a critical stage of flight, such as
a landing. Furthermore, the report reveals, “simulator profiles train F-35
crews to fly HMD-out approaches, but do not emphasize HMD-misaligned
approaches.”
The report also notes that
the onboard oxygen system in the F-35 differs from those
used in other Air Force jets, meaning that “many pilots across the F-35
platform […] report feeling more fatigued than normal, when compared to their
prior legacy aircraft.”
When asked by investigators to rate his level of
mental fatigue on a scale of one to ten, the pilot reported “a four out of ten”
on a routine basis, but on the night of the mishap he reported a “six out of
ten.” The report also raised the issue of emerging research into an F-35A
physiological consideration called “work of breathing” — the physiological toll
taken on a pilot’s cognitive capacities as a result of breathing through the
jet’s unique oxygen system.
These facts, specifically
highlighted by the accident investigation board, are worrying, especially given
the number of U.S. military aircraft incident in recent years that have been
connected in one way or another to oxygen systems.
The pilot maintained the same speed throughout the
approach and landing, meaning the jet touched down on Eglin’s runway 30 around
50 knots faster than normal. At the same time, when it touched down, the jet
was approximately eight degrees shallower than it should have been — an angle
of attack of 5.2 degrees.
U.S.
AIR FORCE
The
incorrect landing attitude as seen through the F-35’s Distributed Aperture System (DAS).
While a speed of 202 knots was appropriate for the
approach to the airfield, the pilot should have disengaged the speed hold,
reducing velocity for the landing. Leaving the speed hold engaged was a
prohibited maneuver, although there are no “audible warnings” that this was
dangerous.
As the jet continued down the runway at this
higher than approved speed, the pilot had to push the stick forward to bring
the jet’s nose down, which had the result of what was almost a three-point
landing — when the wheels on all three landing gear legs touch down
simultaneously.
The nose gear, which would normally be the last to
contact the ground runway, now bounced, throwing the F-35’s nose up violently.
As the pilot attempted to push the stick forward again in an effort to bring the
fighter to a stop, the pitch oscillations became “increasingly violent.”
A rapid succession of stick movements from the
pilot then followed, in an effort to recover and set a landing attitude. As the
report states, “the MP’s stick inputs quickly fell out of synch with the
aircraft pitch oscillations and aircraft control cycles.” These multiple inputs
overburdened the jet’s computerized flight-control system in which a glitch
subsequently meant that the trailing edges of the horizontal stabilizers were deflected
down and locked, which in turn pushed the nose down.
When questioned, neither
the mishap pilot nor other experienced F-35 instructor or test pilots were
familiar with “some of the details of the control logic,” the report explained.
It also highlighted how the complexity of the jet’s flight-control logic is
such that it’s impossible to train pilots on every possible scenario. “F-35A
simulator models do not accurately represent the aircraft flight dynamics seen
in this scenario,” it stated. Furthermore, the simulator allows for high-speed
landings and the aircraft can be consistently recovered in the simulator, even
after bouncing. At least two members of the accident investigation team were
able to successfully land the jet in the simulator when replicating the speed
and attitude of the Eglin mishap. You can read all about the extremely complex
software and subsystems that make-up fly-by-wire flight control systems and how
the pilot is just a voting member of those systems in this War Zone article.
The pilot’s final effort to recover the jet saw
him hold the stick aft, which would normally bring the nose back up, and then
select full afterburner on the jet’s F135 engine in an attempt to abort the
landing and get back in the air for another landing attempt. Take-off, however,
was made impossible by the fully deflected stabilizers, which kept the nose
down.
Only five seconds passed between when the tires
hit the tarmac and the pilot’s ejection, which he initiated as the aircraft
continued to bounce down the runway.
The jet, which the accident report valued at
$175,983,949, “rolled, caught fire, and was completely destroyed,” leaving
debris strewn across the runway, making it a Class A accident, the most severe
category. Class A mishaps involve incidents that result in more than $2 million
in damage, a fatality or a permanently disabled servicemember, or any
combination thereof.
U.S.
AIR FORCE/STAFF SGT. PETER THOMPSON
A 33rd
Aircraft Maintenance Squadron crew chief marshals an F-35A at Eglin Air Force
Base, Florida.
We often hear a lot about
how the F-35 is an easier aircraft to fly than previous-generation
fighters. One test pilot went as far as to
say it was “the easiest aircraft I’ve ever flown in my life.” Comments from the
pilot involved in the May 19, 2020, accident present a different picture. The
aviator reflected that he was not only fatigued at the time of the crash, and
had been suffering increasingly poor sleep, but also that he found the F-35 to
be significantly more tiring to operate than his previous aircraft, the F-15E
Strike Eagle.
In an interview for Air & Space Magazine, one F-15E-turned-F-35
pilot provides an interesting comparison between flying the two jets. “The
transition from a fourth-gen fighter to a fifth-gen fighter was like learning
how to drive an automatic car from a manual. The F-35 actually handles a lot like
the F-15E, with the difference being, the F-35 is a high angle-of-attack
fighter with advanced control logic. Those of us not used to low-speed,
high-AOA performance from our previous aircraft must practice and adapt to
those flight regimes.”
The accident report also notes that the pilot had
additional tangential distractions on his mind that added to the here-and-now
worry about the HMD. A day earlier, for example, the pilot was notified of
exposure to the COVID-19 virus and was awaiting a colleague’s test results to
determine his susceptibility.
In the report, the pilot notes other more
immediate distractions too, including a poorly lit runway area that meant he
had to “point into the black abyss” to get his jet back onto the runway. At the
same time, this was compounded by the aforementioned green glow issue.
For all the advances that it brings with it, the
F-35 program has presented its fair share of challenges and its path to the
front line has been anything but smooth. The loss of this example from the 58th
Fighter Squadron last summer is a reminder of the complexities inherent in the
jet — and the fact that flying fast jets will always involve a degree of
risk.
The cold reality is that
automation and technological advances that make tactical aircraft easier to fly
also make them harder to fully understand and to operate effectively when
things all don't work perfectly as advertised. An over-reliance on simulators
for training has its compounding pitfalls, as well, just as fleet pilots have warned of. This is especially true
when those simulators inadequately reflect what would actually happen in the
air, as was the case in this mishap. When it comes to manned tactical aviation,
experience in the cockpit remains absolutely essential, especially when flying
an aircraft that we are still trying to understand nearly a decade and a half
after it first took to the skies.
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