Today we’re looking at the injuries a pilot could expect were they forced to deploy their
ejection seat for emergency aircraft evacuation.
BROLL 1: Ejection and Explosion (these clips could be used elsewhere too if you don’t
need them all for intro)
Not too long ago, a U.S. pilot crashed somewhere above the south china sea in an F-35. Although
the jet was lost and now lays at the bottom of the sea, the pilot was able to eject from
the aircraft before it crashed and sank.
BROLL 2: Footage of crash / BROLL 3: Second angle from crash
The pilot ejected from the plane at landing speed which is fortunate since he was only
travelling at 202 knots or 232.4 mph on approach rather than at a faster speed associated with
cruising, which I am sure would have been much worse. The news of this incident was
the catalyst that sparked this video idea and got me thinking. What happens to the body
of a pilot when they are forced to eject from an aircraft?
BROLL 4: Historical footage. There’s lots of cool and funny stuff in here– Watch the
whole thing because clips could be used throughout the full video. I leave it up to your discretion.
The first clip of the homie jumping out of the plane is gold.
Since their invention in 1940, the ejection seat has been responsible for saving the lives
of thousands of pilots, with survival rates in the literature of 80-97%. These seats are
common on certain types of military aircraft such as the U.S. F-16 and the Soviet MiG-25.
In most designs, the seat is propelled out of the aircraft by an explosive charge or
rocket motor, carrying the pilot with it. As you might expect, this process is rather
– forceful? Because well the purpose of an ejection seat is pilot survival, not pilot
comfort.
The force of the rockets or explosions must propel the pilot up, out and away from the
aircraft which may, at the moment of ejection, be travelling at speeds approaching 800 mph.
These must therefore be very powerful forces. And you did hear me correctly. Speeds could
near 800 mph. In fact, Air Force pilot Capt.
BROLL 5: Brian Udell Footage. Same thing here, there’s some really good stuff. Have a watch.
Brian Udell is one of the only pilots in history to survive after ejecting from a fighter at
supersonic speeds. In his case, he was travelling at more than 768 mph when he ejected from
his aircraft.
BROLL 6: Footage showing steps
Typically an ejection seat operates in several stages. On modern seats, escape is initiated
by pulling a seat firing handle. Then follows:
1. Powered shoulder retraction. 2. The canopy or hatch above the pilot is
opened, shattered or jettisoned 3. The seat and occupant are launched through
the opening. 4. A rocket pack propels the seat away from
the aircraft 5. A charge separates the seat from the pilot
6. Parachute is deployed
Add to that list the initial event that triggers the need for a pilot to eject and we have
a significantly dangerous situation on our hands. On top of that, it is possible for
a pilot to lose consciousness during the emergency sequence. A lot can happen to an unconscious
human body subjected to several explosive thrusts in a very short window of time.
When the idea was in its infancy, it was theorised that ejection at supersonic speeds was not
survivable
and extensive tests (including some using chimpanzees as test subjects) were undertaken
to determine whether it was feasible.
Can you imagine being one of the chimpanzees in those early trials? Boldly going where
none have gone before?
Ejection seat - Wikipedia
Because of the forces involved, the spine, head and neck are susceptible to serious injury
during the emergency procedure, so we'll talk about those first. According to the Emergency
Medical Journal, vertebral fracture can be found in 30% - 70% of aircrew after ejections.
Obviously, with your life hanging in the balance, the risk is worth it. But the engineers behind
these seats are doing everything in their power to mitigate that risk. They have even
designed an “ejection gun” that fires in three stages with a short delay between
each (a few milliseconds), to offer the spine as much adaptation time as possible. But despite
their efforts, this isn’t a particularly delicate procedure.
The pilot typically experiences an acceleration of about 12-14g. To be clear, that is 12-14
times the force of gravity that is applied to the pilots body while they are being ejected
from the aircraft. Can you imagine weighing 12-14 times your current weight
and being catapulted into the air at speed? With this sudden amount of force propelling
pilots forcefully from the body of the plane, compression fractures of the vertebrae are
a recurrent side effect.
In an article with the Emergency Medicine Journal, C. A. Reed explains: “Individual
vertebrae are able to withstand large compressive loads if they are applied at right angles
to the plane of the intervertebral disc. However because of engineering constraints the initial
thrust is an impulsive load that is experienced at an angle to the long axis of the spine.”
Injuries sustained by aircrew on ejecting from their aircraft | Emergency Medicine Journal
Vertebral compression fractures occur when the bony block or vertebral body in the spine
collapses due to an axial load on the anterior part of the vertebrae. Although this injury
pattern is more common among people whose vertebrae are already weakened due to osteoporosis,
it can occur in people with otherwise healthy spines due to severe trauma… You know, like
a car accident, a fall from height or perhaps… 12-14 freaking g’s of rocket
propelled force applied directly to your behind. Yo, seat cushions can only do so much.
Vertebral Compression Fractures – Symptoms, Complications, Diagnosis and Treatments.
Spinal Compression Fracture Reasons
Martin-Baker – the world’s leading manufacturer of ejection and crashworthy seats for many
years – gives ejection seat survivors a tie and lapel pin. (matter of fact) “Congratulations
on surviving a spine crushing impact at supersonic speeds and the life-or-death parachute acrobatic
manoeuvre that followed.” I’m not sure that the “ejection tie club” is a club
that I want to be a part of.
I wouldn’t be surprised if those lucky people in the “ejection tie club” entered my
clinic complaining of midline back pain. If a compression fracture were at the root of
their pain, radiographs and CT scans would indicate the fracture site at the same location
as their pain. Many of these fractures occur at the thoracolumbar junction which is the
transition zone between T12 - L2. This area represents the transition from a more stable
zone, where the thoracic vertebrae are stabilised by the attached ribs, to a less stable zone,
where the lumbar vertebrae are not stabilised by anything other than the adjacent vertebrae.
This leaves this zone vulnerable to the large forces experienced upon ejection, and consequently
more susceptible to injury..
C. A. Reed elaborates in the Emergency Medical Journal: “This part of the spine is subjected
to the static load of the trunk and head transmitted through the vertebrae above it. At this region
of the spinal column the vertebral end plate has the highest loading per unit area. The
vertebral bodies act as dampers, the blood within them being squeezed out under compression,
before vertebral collapse or fracture.”
Lumbar Compression Fracture - Physiopedia.
If the bone in the front is crushed, but the back of the bone unchanged, this is called
a wedge compression fracture. If the vertebra is crushed in all directions the condition
is called a burst fracture, which is a more severe injury. Any form of lumbar compression
fracture is a serious injury that may be accompanied with neurological damage. When this is the
case, surgery is recommended, though neurologic deficits are relatively uncommon.
First, we would seek to help our “ejection tie” members control the pain with non steroidal
anti-inflammatory drugs, muscle relaxants, and narcotic pain medication, if required.
Some of these compression fractures can be managed nonoperatively. Patients are put on
bed rest for a short period of time, followed by a period of bracing and limited physical
activity. However, in more severe cases surgery is necessary, the options for which may include
either Vertebroplasty or Kyphoplasty.
Compression Fracture | Cedars-Sinai
Vertebroplasty involves the insertion of a small needle to inject a special quick-setting
cement into the fractured vertebra. The cement provides structural support for the broken
vertebra, strengthens the area and usually results in pain relief for the patient.
Kyphoplasty is a similar procedure, but before the insertion of the cement, a small balloon
is used to expand the fractured space and help make the vertebra taller. The balloon
is then removed and the empty space filled with cement.
Complications in these procedures include: the extravasation of cement – which is when
the quick-setting cement leaks into surrounding structures and becomes symptomatic.
“Could you excuse me for a moment? My burst fracture is leaking quick drying cement internally.”
As well as, embolism, neurologic injury, bleeding, hematoma, infection and risk of similar fractures
at other levels.
Clinical outcome and subsequent sequelae of cement extravasation after percutaneous kyphoplasty
and vertebroplasty: a comparative review.
And that’s just the tip of the iceberg…
The cervical spine and head are also at risk in these emergencies as the forces applied
on the body may cause sudden movement away from, or may impact against the ejection seat.
Let’s have a look at the injuries sustained by a thirty-five year old aircraft navigator
who survived ejection after mid-air collision with another aircraft.
Radiographs of a pilot (pictured in the Emergency Medical Journal) showed evidence of C1-C2
subluxation, meaning that one vertebrae had slipped partially out of place with the other,
with a 1cm forward displacement of C1 on C2. He was kept immobilised on a spinal board
and intubated, paralysed while his lungs were ventilated. A CT scan showed that he also
suffered a left frontal haematoma. He spent 24 hours in intensive care before he was extubated
and further diagnostics were performed. It was then discovered that he actually suffered
an atlantoaxial dislocation with avulsion of the transverse ligament and gross posterior
soft tissue disruption. Okay that’s a mouthful– one thing at a time.
The head is basically a bowling ball resting atop the spine. When extreme force is applied
to the body underneath it, there is a delay in the transfer of force between that body
and the head. The body moves forward, and the head remains where it is in space – you
know like in the looney tunes? – only to be whipped forward once the tension of the
impact has been transferred through. In this interaction, the neck responds like a chain,
quickly stretching to its maximum and then catapulting the head forward. This puts the
cervical vertebrae under immense strain.The pilot would be subjected to this type of force
by the rocket mechanism used to propel the ejection seat away from the compromised aircraft.
A cervical disc injury occurs when there is a herniation or protrusion of the disc contents
from within the dics in the spine. The vertebrae of the spine are separated by discs between
each bone that allow for flexible movement of the spine. However, the connection between
C1 and C2 is slightly different– The atlantoaxial joint (which has no vertebral disc) between
C1 and C2, where the C1 ring rests on the C2 post, is secured by a thick, strong ligament
called the transverse ligament. If this ligament is compromised your neck becomes unstable
at the C1-C2 level. In the case of our pilot, the C1 vertebrae (which is attached to the
head), was forced forward and out of alignment with the C2 vertebrae underneath it, with
enough force to tear the transverse ligament and compromise the soft tissue at the back
of his neck. He was also experiencing some loss of motor function in his upper extremities,
which suggested associated neurological damage. This is the type of thing that must be treated
operatively– and fast!
In order to restore structural integrity to the neck, he underwent a C1 to C2 modified
transarticular C1/C2 fusion and fixation. In this procedure, the surgeon will wedge
a bone graft (harvested from the iliac crest of the patient) between the spinous process
of C2 and underneath the posterior arch of C1. Sublaminar wiring made from surgical grade
stainless steel holds the graft in place as it fuses to the C1 vertebrae above it and
the C2 vertebrae below it. This procedure stabilises the neck in place of the compromised
transverse ligament, but limits flexibility in the process since the vertebrae can no
longer move independently from one another. The C1 C2 spinal motion segment primarily
provides rotational motion and once fused, reduces a person’s ability to turn their
head freely from left to right.
Postoperatively, a patient requires external orthosis during the healing process. Sontagg,
who modified Gallie’s original technique, recommends the use of a halo to immobilise
patients for three months after surgery, and the use of a rigid cervical collar for one
to two months after that. With this kind of immobilisation, Sontagg has demonstrated a
97% fusion rate in his patients.
After 6 months, the pilot in our study was well on his way to recovery and had recovered
motor power in his right arm. Unfortunately weakness in his left arm has persisted and
he has not been able to return to flying. Upon further examination, this injury is thought
to be associated with a brachial plexus injury– a network of nerves in the shoulder that carries
movement and sensory information from the spinal cord to the arms and hands– which
brings us to our next point of consideration.
After initial ejection, the seat tumbles through the air at variable speed, which may reach
as high as 180rpm. Though ejection seats are equipped with drogue parachutes and deployable
aerodynamic panels to prevent said tumbling, “ejection tie members” are susceptible
to injuries from flailing limbs while in the air. Think about it: the torso is secured
to the ejection seat as it falls, but the limbs are not. Perhaps our pilot’s arm was
flailing and the brachial plexus nerves in the shoulder were stretched, compressed or
torn away from the spinal cord to some degree. If the pilot loses consciousness in the ejection,
the risk of extremity flail injuries is even worse as they cannot tuck their limbs inward
against their body to resist the forces of wind and rotation. Although having said that,
were I ejected from an air craft at over 700 mph, my arms and legs are not going to be
tucked in against my body, I can assure you. [show roadside blow up flappy advertising
dummy here]
In speaking about his own ejection experience in which his copilot was killed, Udell stated,
“It felt like somebody had just hit me with a train,..When I went out into the wind stream,
it ripped my helmet right off my head, broke all the blood vessels in my head and face,
my head was swollen the size of a basketball and my lips were the size of cucumbers. My
left elbow was dislocated and pointed backward, the only thing holding my leg on was an artery,
the vein, the nerve and the skin and my left leg snapped at the bottom half.” Sounds
like just another day at the office.
After a specified amount of time, an altitude sensor causes the drogue parachute to pull
the main parachute from the pilots chute pack and a seat-man-separator motor fires causing
the seat to fall away from the crewmember.
The deployment of this parachute is yet another opportunity for injury as it stalls the momentum
of the body attached to the seat, causing the weighty head to continue its trajectory
forward until the cervical spine is stretched to its limit and whips the head backwards
again. Sound familiar? This mechanism is also associated with injuries to the cervical spine
as we mentioned before.
And we still have the landing to consider… Once the parachute is deployed, the air speed
of the ejection seat is reduced to approximately 17mp/h– but that speed packs enough of a
punch to do some harm when the pilot makes contact with the ground. Depending on the
angle at which a pilot lands, and rotational force applied at landing, they may be susceptible
to lower leg injuries.
So in 0.5 seconds, the seat has lifted to about 100 - 200 feet from ejection altitude.
At 0.52 seconds the seat-man-separator motor flies; cartridge fires to release crewmember
and his equipment from the seat. At 2.5 - 4 seconds the main parachute fully deployed.
And this isn't even an exhaustive list of potential injuries in this short time frame.
What about the powerful gust of wind that enters the cockpit when the hatch is jettisoned
posing danger to the lungs, or the potential for suffocation in high altitude ejection?
What about the scrapes and burns one might suffer from airborne debris? I mean the list
goes on– so as David Newman, a researcher in aviation medicine, reminds us: “the entire
process can take less than three seconds from tugging the ejection handle to descending
“safely” under a chute. But it is a rapid sequence full of violent jerks that can injure
you.”
At least– there is a good chance you’ll live to see another day!
Let me know what you’d like me to cover next–
Thanks for watching. As always, that’s been a word from Dr. Chris, not your everyday ortho.