Stabilizing helicopter payloads during medical evacuation rescues can be a challenging task due to the swinging or more complex conical motion of the patient. Hoist cable swing can have dangerous effects including loss of payload, contacting the side of the helicopter, and increasing time for search and rescues. The goal is to reduce the oscillations of the swing – like a pendulum – to be able to swiftly and safely raise the patient from the hoisting location and into the helicopter, so that they can then be transported to a medical facility as quickly as possible.
Helicopter hoist and winch training for search and rescue (SAR) and medical evacuation (medevac) is offered by many organizations using traditional methods and techniques. Some firms manufacture and supply equipment for safe hoisting as well as hoist training, such as Breeze-Eastern, which offers in-house hoist maintenance training at its facility in Whippany, New Jersey. Others specialize in operational training, like Air Rescue Systems, Priority 1 Air Rescue, and SR3 Rescue Concepts. Most of the US military medevac training occurs at Fort Novosel (formerly known as Fort Rucker) in Alabama for pilots, hoist operators (crew chiefs), and hoist riders (paramedics), with paramedics also receiving specialized training at Fort Sam in Houston, Texas. And there are companies that offer fully integrated haptic virtual training, like Bluedrop Simulation & Training. There are also companies that provide unique solutions to cable swing and spin, such as Vita Inclinata, whose Vita Rescue System Litter Attachment is affixed to the payload with cinch straps and quick clips, and uses two propulsion systems and a thrust vector system to directly control the movement of a litter.
A novel approach
The practical application of this method involves accurately measuring the angle and swing of the payload and then directly controlling the length of the line
A recent study has demonstrated that it is possible to achieve two-dimensional stabilization and even explore a three-dimensional solution by assuming a steady hover over the patient. This method involves precisely varying the length of the payload line according to the line’s motion and specific constraints, drawing on principles of pendulum nonlinear dynamics. The practical application of this method involves accurately measuring the angle and swing of the payload and then directly controlling the length of the line. The physics behind the payload control is shortening the line when the payload is slowest near its highest point in the swing. The line can also be extended when the payload is near the bottom of the swing. With the help of a low size, weight (<0.5kg), and power automated stabilization system on the payload that can be enabled and disabled with the flick of a switch at the hoist, this approach holds promise for medical evacuation rescues.
Ian Azeredo, Chief Engineer at Breeze-Eastern, explained how this will affect the community: “What this means ... is a future non-invasive means of controlling hoist reel-in without significant input control from the hoist operator. Or a good tool for training for dynamic hoisting motions.”
The system design for the device and test results were presented at the Third International Nonlinear Dynamics Conference (NODYCON 2023) on 19 June 2023, and the team’s paper will be published in the conference proceedings. User data are input into the system and a gyroscope sends angle and angular velocity data to an Arduino Uno, which sends a pulse width modulation (PWM) signal via Bluetooth to the motor controller to drive the motor. The motor mount holds the winch and the motor, and the Arduino Uno microcontroller powers the system by a connected battery pack.
Cable swing and conical rotation (oscillation) are very real hazards during helicopter rescue hoist operations
David Creech, CEO of Vertical Lift Consulting, stated: “Cable swing and conical rotation (oscillation) are very real hazards during helicopter rescue hoist operations.
“While proper training instills both proactive and reactive measures aimed at preventing a catastrophic event, there is always the potential for the rapid escalation of cable movement beyond the manual control abilities of the hoist operator.
“An automated hoist stabilization method – such as proposed by Mary Lanzerotti and her team at the Virginia Polytechnic Institute – would not only be very effective as a reactive measure for less experienced hoist operators, but also as a proactive/preventative measure for hoist operators of all skill levels.”
The future for the design
The next stage for this novel design will be to further test the method of action with longer lines and in outdoor environments. Rozzy Finn, Licensing Officer at Virginia Tech Innovation and Partnerships, stated: “I see great potential for the hoist stabilization system designed by the team; it’s an elegant idea that has great potential to save lives once deployed. I look forward to helping to commercialize this technology, and I’m excited to see it deployed.”