Military SAR, a look ahead

If we look back over the history of using helicopters for rescue operations, we see that the US military has been at the leading edge of development – from when UH-1s in Vietnam had internal hoists installed, through the development of the original external hydraulic hoists for the US Navy. The US Coast Guard also played a pivotal part, pushing forward the installation of overload protection devices that are now standard across hoists worldwide. Recently, the driving force for hoist improvements has been the non-military SAR market. This has resulted in the dual installation typically seen on specialized SAR helicopters and the current project of developing new hoist standards with both the FAA and EASA. 

Coming soon

As we look ahead, we see that the US Army is developing the replacement for the ubiquitous Black Hawk helicopter in its Future Long-Range Assault Aircraft (FLRAA) configuration (the smaller Future Attack Reconnaissance Aircraft (FARA) program does not currently have a hoist specified). Both the prototype aircraft (Bell V-280 and the Sikorsky/Boeing SB-1) are significantly different from the current aircraft, in that they are designed to fly up to 300 knots and in the case of the V-280, have wings where a hoist would ‘typically’ be located. So, there are some basic questions to answer. Will a typical pod hoist hanging off the side suffice? Is 600 lbs still an acceptable load capacity? (We all know that the average American is getting heavier) And are there additional features that the Army will want to incorporate?

We do have some clues from the military.  Back in January 2019, the Army issued an FY 2019 Rapid Innovation Funding (RIF) invitation. This stated that “The Future Vertical Lift Program Office is interested in innovative technologies to develop a rescue hoist that will eliminate uncontrollable oscillations, uncontrollable spinning and lift up to 1,000 lbs.” It continued: “Controlling oscillation and rotation would result in a stable hoist that would also make insertion and extraction quicker, which lessens the hovering aircraft’s exposure to enemy fire. There are also emerging requirements including 1,000-lb lift capability, self-fault detection, infra-red lighting, and a readout to the operator of how far the load is from the ground.”

Controlling oscillation and rotation would result in a stable hoist that would also make insertion and extraction quicker, which lessens the hovering aircraft’s exposure to enemy fire

Although this project was not funded in 2019 for reasons unknown (and it may reappear in future RIF’s) it does give us many pointers on where the army wants to move to in the future. In addition, the US Army released a draft FLRAA System Performance Specification in July 2019 that requested a ‘threshold hoist capable of lifting 670lbs, and an objective (desired) capacity of 800lb’.

Load Capacity

Almost all current hoists (and helicopters) are rated to 600 lbs, which has worked well for 50 years, but even in the civilian market we are starting to see some manufacturers push capacities above 600 lbs.  Existing hoists can likely be readily extended to 670 lbs, but jumping to 800 lbs (or 1,000 lbs as per the RIF request) will likely result in significant re-engineering.

Lifting three people at once will also likely require changes to hoist techniques

Lifting three people at once will also likely require changes to hoist techniques, more power available from the aircraft and even a larger door into the helicopter.  Any increase in hoist capacity will likely result in a heavier hoist, and even for a piece of lifesaving equipment, weight must be balanced against loss of capacity or range. As always, the benefits of lifting more must be balanced against the increase in hoist weight and the required extra power that may be in short supply on a hot and high rescue mission in the mountains of Afghanistan in the middle of summer.

Controlling oscillation and swing

This is arguably the most interesting technology that the military is interested in developing. There are at least three companies (to the author’s knowledge) developing this technology, with some funding coming out of the US Air Force’s AFWERX program for small business innovation. Current prototypes (as shown at HAI Heli-Expo last year and this year) are focused on integrating with a rescue litter, but systems to use just with the hook are also planned. At least two different technologies are proposed, one using powerful fans and the other using a gyro-based system to stop the spin and/or swing, and have performed well in early demonstrations. As with any new technology, there is a long path ahead as these systems must be both reliable and robust enough to withstand use (and misuse) in extreme environments. There may also be opportunities to use this technology to enable precise positioning of the hook, a potential leap forward in hoisting capability. As always with hoisting, there is no free lunch and these types of systems will reduce the available load capacity of the hoist and require the hoist operator to do multiple jobs at once.

Speed

Hoisting speed is a critical feature for military SAR. Quite simply, it reduces the time that the aircraft (and the people on the hoist) are in the line of fire. The newest hoists for civilian SAR aircraft are AC powered and there is significantly more power available to the hoist, so speeds of up to 350ft/min are now possible. We may see speeds approaching 400 ft/min in the future as newer hoists come into use and more aircraft power is available.

Self-fault detection and hook height above ground

With advances being driven by the civil market and the opportunity to integrate into a completely new aircraft, this data should be readily available for integration with the aircraft avionics and HUMS systems and provide the capability for Prognostic Health Management (PHM) of the hoist system as part of the standard HUMS system.

Cable Inspection

The hoist cable is often the most maintenance-intensive part of a hoist, requiring regular inspection and, all too often, replacement. Although automated cable inspection systems for off-aircraft use have been developed, their accuracy and repeatability has often been questioned and installing such systems on the aircraft will result in more weight and complexity

Outside of the specific RIF requirements, there are other factors to take into account as well.

Integration with the aircraft

In order to minimize impact on the aircraft, speed integration with the aircraft will be very important, and is significantly different between the tilt rotor V-280 and the more ‘conventional’ SB-1.

speed integration with the aircraft will be very important

The V-22 (the only tilt rotor in operation today) has a hoist located over the aft ramp, but the current iteration of the V-280 has no ramp, so hoisting would be from the door under the wing, potentially leading to a hoist installed in the wing (as per Bell Patent US 10,549,854 B2 Feb 2020).

Overall Maintenance

Logistical support is a sometimes-ignored reality that can impact the military significantly more than the civilian operator due to the length of the supply chain. Systems where maintenance is minimized and components can be readily replaced by a field mechanic without specialized tools have an obvious benefit.

At the end of all this, it must be remembered that the aircraft manufacturers, Bell and Sikorsky/Boeing, have the unenviable task of having to integrate the hoist into an aircraft that has many (often conflicting) requirements, and a hoist is just one of many specific mission sets that may be installed, so it may take a back seat to other, higher priority equipment and functions.

Once the first FLRAA aircraft enter service in the early 2030s, we will be able to look back and see that there has been a significant leap forward in both hoists and hoisting techniques as all (or maybe just some) of these technologies make their way into the aircraft. And, as always, it will be interesting to see if they are adopted equally across both civil and military markets or if there is divergence with specific functions – stay tuned!