Helicopter pilots frequently sustain injuries. And not just from accidents.
Rather, it’s from the seats and helmets in concert with the aircraft’s constant whole-body vibration (WBV) and flight control positions. The injuries can be permanent, debilitating, even career-ending, as pointed out by a study published in 2011 by the Naval Postgraduate School. According to a survey of hundreds of Navy helicopter pilots, 88.1 percent experience back pain on at least 50 percent of their flights, and 34.4 percent admitted that it affected their situational awareness. However, those who experience pain from uncomfortable seats are reluctant to seek treatment for it for fear of being removed from active flight status.
The study found that the problem was exacerbated by length of flight, poor seat lumbar support and padding, helmet-mounted night vision goggles, aircraft vibration, and the suboptimal posture sometimes required to effectively manipulate helicopter controls. Cockpit seats in particular were faulted for their thin padding that also resulted in leg pain and numbness due to lack of blood flow or “compression ischemia.”
Study recommendations included seat designs that facilitate improved posture and better flight control geometry including offset cyclics, a design incorporated into the cockpit of the Bell 525 super-medium twin, as opposed to traditional cyclics centered between the pilot’s legs. It also suggested the wider adoption of aircraft vibration reduction technologies and lighter flight crew gear.
In her 2013 Embry-Riddle Aeronautical University thesis that examined the ergonomics of pilot seats, Yolanda Andrade concluded, “The need for better seat designs that fit the target population and decreases biochemical problems and reduces fatigue is apparent.” She added, “Sustained exposure to seat vibrations can also contribute to muscle fatigue and damage of the [spinal] discs. Vibrations apply pressure to the spinal column, which in turn strain the intervertebral discs and end plates that can lead to blood flow problems and ultimately failure of nutrition to the discs.”
But when it comes to aircraft seating, particularly helicopter seating, the quest for comfort often takes a backseat to survivability via energy-absorption features, which emphasize structures and the regulatory requirements governing them. A 2020 study published in Progress in Aerospace Sciences noted, “The excessive impact energy exceeds the human tolerance, leading to heavy casualties for the occupants during a helicopter crash.”
The study also explained that causes for helicopter crash injuries fall into three general areas: inertial overload due to sudden acceleration; contact injury from collision with hard cabin surfaces; and environmental injury due to smoke, fire, or drowning. The seats, restraints, and subfloor must all work in concert to achieve energy-attenuation objectives.
For civil helicopters in the U.S., those are set via regulation for all new aircraft certified after 1989. Both Part 27 and 29 helicopters must have seats able to sustain a downward load of 30 g (14 CFR 27.562 and 29.562).
However, in 2020 only 10 to 16 percentof the total helicopter fleet met that requirement due to low turnover. Citing FAA data, Helicopter Association International president James Viola said that “from 2009 to 2017, non-crash-resistant seats caused the deaths of 307 people in helicopter crashes.”
There is a long list of popular civil helicopters certified before 1989. They include the series aircraft of the Airbus AStars and the Bell 206 and derivatives, a universe containing thousands of aircraft.
For these and other helicopters, the FAA advises against unapproved upholstery modifications that alter certification criteria, particularly those subject to the newer dynamic certification standard.
In a 2016 Advisory Circular (21-25B), the FAA advised, “Modifications affecting the strength or stiffness of a seat part may affect the seating system, and thus may affect the dynamic loading of the structure and the loads transferred to the occupant. Therefore, a modification to a part either in the direct load path or within striking distance of the occupant will typically require a dynamic assessment. For this reason, any changes to common components such as seatbelts, cushions, IFE system hardware, seat back tray tables, and any other item added or removed from the seat, an assessment must be conducted to verify that the seating system structural integrity and occupant injury performance is maintained.”
New seat cushion schemes designed to improve comfort are offered by several manufacturers, including Oregon Aero. Raytheon’s Collins Aerospace unit is working to improve helicopter seat comfort, incorporating features such as pressure mapping for ergonomic design, vibration absorption, adjustability, an integral seat bucket design, and customer-specified options including armrests. Cushion contouring is particularly critical for comfort on newer 30 g seats that have seatback structures that are typically uncomfortable because they are more upright to sustain impact g-loads and protect the occupant’s spine in the event of a crash.
In addition to traditional aircraft seating providers, some elements of the military are thinking decidedly out of the box when it comes to improving helicopter pilot comfort. The Army turned to Nascar, specifically Hendrick Motorsports. Hendrick not only fields race cars; it also builds components for them, including seats. For the Army’s AH-64 Apache gunship, Hendrick developed a new contoured cushion system that feels like memory foam and is self-extinguishing. The Hendrick Advanced Seat Liner can be air-conditioned and is covered in leatherette. Evaluating maintenance test pilots found it more comfortable than the standard seat. (Hendrick also has designed a high-performance Infantry Squad Vehicle for the Army that fits inside a Boeing CH-47 Chinook).
The worldwide helicopter seating market is large. Even without a retrofit mandate for 30 g seats, a January 2024 study by Global Industry Analysts estimated the overall helicopter seating market at $5.2 billion in 2022 and projected it would grow to $11.1 billion in 2030. Helicopter crew seating is expected to post an 11.7 percent compound annual growth rate over the next seven years.
While there are economic and technical challenges to retrofitting the existing legacy helicopter market with crash-worthy seats, a 1994 study by the U.S. Army’s Aeromedical Research Laboratory favorably reported on the feasibility and benefits of doing so, using the Bell OH-58 (civil 206) as a baseline. The Army reported that the new seats added just 20 pounds for each aircraft in which they were installed, were more comfortable, and able to attenuate energy three times better than the existing seat, thus improving survivability.