Innovative technology and design reduce the risk for U.S. aircrew who eject in an emergency.
An aircraft ejection seat is a pilot’s last resort in an emergency. When a pilot pulls the ejection handle, the aircraft’s canopy is jettisoned and the pilot is launched out of the cockpit and into the sky at rocket-like speed. Many factors are at play during this sequence – the aircraft’s speed, attitude and altitude at the time of ejection and whether the pilot is wearing helmet-mounted devices – which can greatly increase the risk of injury or death.
Mitigating this risk and ensuring pilot safety is the top priority for UTC Aerospace Systems, the primary supplier for the U.S. Air Force (USAF) and the sole ejection seat manufacturer in the U.S. Their latest ejection seat, the ACES 5, is designed to address the variables at play in an ejection sequence and provides significant safety improvements, all with the aim of saving a pilot’s life and minimizing injury. Since its introduction in the late 1970s, ACES II has saved more than 620 aircrew members.
Here are four ways the ACES 5 builds on that impressive legacy:
Better seat technology to accommodate newer pilot head gear: Advances in military gear means pilots can now be wearing helmet-mounted devices like night vision goggles while in flight. According to an article in Forbes, “although these devices greatly enhance situational awareness and safety under normal flying conditions, they can become killers in an emergency escape using current ejection seats.” The ACES 5 addresses this issue by providing passive head and neck protection (PHNP) that acts like a catcher’s mitt, cushioning and supporting the head and neck to avoid the “slam back” from the high speed wind streams associated with the ejection.
Passive leg and arm restraints: The ACES 5 seat includes passive leg and arm restraints that help keep a pilot’s limbs close to the body, avoiding harm as they are catapulted out of the plane at high speed and preventing flailing injuries that can cause serious injury or death.
Upgraded parachute performance: In order to better protect the pilot, the ACES 5’s upgraded parachute slows descent rate while significantly minimizing pilot oscillation, which reduces the landing injury rates to pilots by over 50%. Historically, 43% of all ejection event related injuries occurred during the “parachute landing fall”.
Smart rocket motors: During an ejection sequence, not all pilots are created equal. Typically, ejections are less safe for female pilots because they are much lighter than male pilots. Unlike foreign seat designs, the ACES 5 rocket catapult uses a variable burn profile to provide more energy for heavy pilots and less for lighter pilots, varying the “G” load forces between 9 to 12 G’s. This is coupled with the ACES 5’s unique gimbal stabilization package, optimizing rocket motor pointing and ensuring proper tail clearance and maximum terrain clearance. These two innovations reduce back injury risks to approximately 1%; far exceeding the Air Force overall injury risk requirement of 5% for pilots weighing between 103 and 245 lbs. By comparison, foreign seat designs can exceed 18 G’s for expanded aircrew sizes, resulting in higher head, neck and spinal injury rates. A Royal Air Force study of other ejection seats cited injury rates of nearly 30%.1
Ejection seats in the U. S. Air Force’s legacy fighter and bomber aircraft can easily be upgraded to this improved configuration because of the 70% commonality with the ACES II. Retrofitting can be completed in one day. Once in the aircraft, maintenance is also simplified. The modular seat design has four pieces which improves access to the internal components of the seat. The entire seat can be removed from the cockpit without removing the canopy and without the use of a crane because of this modular design. In fact, ACES 5 can be removed in 15 minutes and re-installed in 25 minutes, saving the U. S. Air Force thousands of man-hours of labor each year across the fighter and bomber fleets.
1M. Lewis, “Survivability and Injuries from Use of Rocket-Assisted Ejection Seats: Analysis of 232 Cases”, Aviation, Space and Environmental Medicine, Vol. 77, No. 9:936-943, Sept 2006.