What it takes to keep military aircrew safe, sitting in advanced ejection seats used around the world

Posted by John Fyfe on May 31, 2018 4:50:00 PM

Imagine you are piloting a B-2 Spirit a few years from now. Your bomber has experienced some type of catastrophic damage or system failure. You assess the situation—it’s clear that the aircraft is no longer flyable, and you and your co-pilot need to eject. You feel confident because of the trust you have in the ACES 5® ejection seat you are sitting in.

Here’s what happens next: you pull one of the ejection handles at your side and the hatch is jettisoned. Your ACES 5 seat then launches you upward. In a fraction of a second, the relatively tranquil environment of the cockpit is instantly transformed into an icy-cold, pitch-black nighttime sky.  You are hit with the sudden, earsplitting force of windblast at a few hundred miles per hour and around 10 Gs of acceleration.

But you are safe. The calibrated, controlled burn of the main catapult rocket has already compensated for your weight and is propelling you safely clear of the aircraft. As the seat separates from the aircraft, the drogue parachute deploys, and rockets ignite to keep your seat stable while the aircraft falls away. Less than two seconds later the main parachute deploys as you are released from the seat, and you descend under the parachute. You land safely, confident that you have a survival kit that covers your essential and immediate needs; a life raft, an emergency locating beacon, a sleeping bag, an escape and evasion kit, first aid supplies, and other equipment. And thanks to your ACES seat, there is a greater than 99 percent chance you will walk away from the ejection without a back/spinal injury.

Ejections weren’t always so safe. During the early decades of flight, aircrew in trouble bailed out of their aircraft while attempting to avoid hitting the aircraft’s tail and stabilizers, and then had to manually release their ‘chutes. Those early aircraft typically cruised at 150-350 knots and altitudes of anywhere from 10,000 to 25,000 feet—and all too often, a bailout resulted in serious injury or death. Ejection seats fired by explosive cartridges didn’t enter the market until the mid-1940s.

Today, it’s a totally different situation. Modern military fighters like the F-22, F-15, and F-16 employ at much higher airspeeds and altitudes, sometimes in excess of Mach 1.0 and altitudes as high as 50,000 feet. Likewise, aircrew equipment now includes fully loaded survival vests, and sophisticated helmets that can weigh more than five pounds due to helmet-mounted devices. For multi-crew aircraft, the ejection process is even further complicated. For example, a successful ejection from a B-2 Spirit bomber requires both the pilot and copilot seat to each have its own sequenced ejection delay to achieve two different ejection seat trajectories. For the modern military aircrew, safely ejecting from a jet aircraft is a highly complex and challenging event well beyond the simplicity of “bailing out.”

At UTC Aerospace Systems, our mission for 40 years in the ejection seat business has been to overcome the challenges of high speed ejections, heavier helmets with helmet-mounted devices, and safely accommodating aircrew of all sizes. Constant ejection seat innovation is required to keep military aircrew safe—to not only successfully get them out of their aircraft, but also bring them to the ground safely with the ability to walk away with little to no injuries.  

Through constant ingenuity and innovation, ACES 5 makes aircrew safer by addressing three key issues:  

  1. Safely ejecting at higher speeds. Since the early 1980s, ejecting above 450 KEAS has posed a high risk of injury for military aircrew. Initially, these risks were deemed acceptable. Thanks to the ingenuity and innovation of our ejection seat engineering team, aircrew no longer have to accept that risk. A critical feature of the ACES 5 design is the ability to safely protect aircrew at all airspeeds.

    ACES 5 expands the safe ejection envelope out to 600 KEAS and uses passive arm and leg restraints to protect aircrew against “flail” injuries that historically result from high airspeed ejections. Upon ejection, these devices provide supportive webbing that extends to catch an airman’s arms and restraints that secure their legs, holding them firmly to the seat structure until seat separation. 
  2. Safely ejecting wearing helmet mounted devices. Aircrew helmets used to be simple: light, round, and smooth. Air would flow over them evenly during an ejection, and an airman’s head was more likely to stay straight and safely aligned into the windstream. As new technologies entered the cockpit, helmet-mounted devices (night vision goggles, helmet-mounted cueing systems, etc.) became the norm, providing aircrew with improved sensing and targeting cues. Initially, the ejection risks posed by these devices were not fully appreciated. Some of these helmets weigh up to five pounds, with every pound being affected during an ejection by an extra nine-12 G’s of force. The additional windstream forces can be asymmetrical, and without adequate protection can violently force the head to either side creating a potentially fatal injury.

    ACES 5 safely protects aircrew by incorporating a unique mechanical head and neck protection system, free of inflatables. During an ejection a protective steel framework extends from the seat back, cradling the occupant’s head and preventing any sudden backward or side head movements.

  3. Safely accommodating aircrew of all statures. Great airmen come in all shapes and sizes, and in 2016 the U.S. Air Force expanded injury requirements so that ejection seats would safely accommodate all occupants from 103-245 pounds. Seat stability is a key requirement toward providing safe ejections across the entire aircrew spectrum.

    The ACES 5 ejection seat stability package contains a gimbaled rocket that ensures the seat remains upright, preventing forward or aft seat pitch caused by the different centers of gravity from varying sized aircrew. This unique feature helps maximize the height of the ejection seat trajectory, while minimizing risk of injury by keeping the seat in the upright stabilized attitude that optimizes aircrew position during opening of the parachute.

Different sized aircrew experience different acceleration forces during an ejection.  When ACES 5 ejects, the main catapult rocket propelling the seat from the aircraft automatically compensates for aircrew weight by adjusting acceleration and speed, minimizing the risk of spinal compression and other back-related injury. Because of this step change in innovation, aircrew of all sizes can safely eject. With ACES 5, airmen don’t need to worry about dangerous excess acceleration forces or selecting manual seat/cockpit settings.

To further address cockpit fit accommodation, we updated our ACES 5 to include both height and tilt adjustment capabilities so that aircrew of any size are best positioned in the cockpit to complete their mission.

ACES 5 is the product of a team comprised of innovative engineers and pilots. Our entire organization holds itself to the highest quality standards and is committed to safely bringing our aircrew home on their worst possible day. We have flown in ACES seats, and our friends and family still do, so we know firsthand what’s at stake.  While ACES II® ejection seats already have a historical spinal injury rate of less than one percent, our team designed ACES 5 to move that statistic closer to zero--so that airmen safely exit their aircraft, return safely to the ground, fly again tomorrow, and have a great story to share.

ACES 5 is the next step in our longstanding mission: protecting those born to fly so that they may live to walk away. 

Topics: Performance, Safety

Written by John Fyfe

Director of Air Force Programs, UTC Aerospace Systems
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