Future Vertical Lift – has the US Army learned the right lessons?
Over the next decade, the US military is seeking a wholesale refresh of its rotorcraft fleet with a family of related Future Vertical Lift (FVL) platforms. This is intended to provide replacements for four legacy models, from the small OH-58 Kiowa scout (already retired) to the large CH-47 Chinook.
Although officially an army-only concept thus far, it is probable that the other branches will adopt at least some of the aircraft. At present, most progress has been made on what was originally the medium-size Joint Multi-Role platform, currently flying as the Bell V-280 tiltrotor. This was selected over the Sikorsky-Boeing SB>1 compound rotorcraft as the Future Long-Range Assault Aircraft (FLRAA)... Continues below
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Above: A production version of the V-280 is due to enter service as the Future Long-Range Assault Aircraft by 2030 under current FVL plans. (Photo: Bell)
The structure of the programme has been heavily influenced by several recent problematic development efforts. The expensive failure of the early 2000s Future Combat Systems initiative has made the army wary of large and interconnected efforts that rely on – and could be foiled by – one element not working to expectations.
This ‘single point of failure’ risk-aversion has guided FVL planning with emphasis on shared software and core systems, but using different platforms, likely supplied by more than one manufacturer. Thus, while Bell is confident that the V-280 design could be evolved into other FVL categories, there is little expectation that the profile of the different models will bear a strong resemblance.
This perspective has been further informed by the ongoing F-35 saga. The compromises necessary to develop an aircraft for three services were viewed early on as potentially troublesome, and such fears have proved well-founded. This is a cyclical trait of defence programmes and a lesson that never seems properly to be learned; the army was therefore keen to avoid falling for the chimera of a common aircraft for a diverse set of roles.
Nonetheless, to reduce cost and maximise efficiency, all FVL aircraft are planned around a shared core common mission system, under development by Lockheed Martin. This will follow lessons from the difficult software evolution on the F-35 and benefit from the current Block 4 efforts under way.
As a further nod to commonality, a developed version of the F-35’s Distributed Aperture System electro-optics and helmet is planned. This will likely be tested on the current V-280 development aircraft long before the in-service variant is completed. Mature, lower-risk weapons are also expected to feature, such as a variant of Rafael’s Spike Non-Line of Sight missile.
There was some surprise that, following the issues surrounding the V-22 Osprey, another tiltrotor was selected to replace the far simpler Black Hawk. While the speed and range performance of the Osprey has been praised, development was protracted and a series of fatal accidents have led to it being viewed as something of a mixed blessing.
However, the V-280 design takes heed of various lessons learned. The production variant is planned to use the same Rolls-Royce AE 1107 engines as the V-22, but for additional redundancy, a common driveshaft runs the width of the wings, allowing both rotors to be run from a single powerplant.
Supporters of the tiltrotor approach suggest that negative publicity has resulted in the Osprey’s reputation being out of proportion to actual loss rates and the performance offered offsets the risks inherent in a more complicated design.
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Although it has not progressed far, Leonardo’s AW609 (with which Bell was closely involved) shows that other companies are exploring whether the concept could be more widely adopted by defence and civil operators.
The rival SB>1 design also used a less common approach with a contra-rotating main rotor and pusher propeller. Although the former element has been widely used by Russia’s Kamov, it was novel for the US and brought own complications as well as benefits.
The next stage for FLRAA will be development of both the final physical airframe and onboard systems. An in-service goal of 2030 offers a relatively balanced timeframe and allows output from the development phase to guide selection of the smaller Future Attack Reconnaissance Aircraft (FARA).
Above: Sikorsky’s Raider X FARA competitor features the same coaxial compound configuration as the SB>1 Defiant. (Image: Lockheed Martin)
Bell and Sikorsky are again competing for this award, but have been somewhat reticent to provide explicit details of their efforts or comprehensive information on their designs. Sikorsky’s Raider X retains the SB>1’s compound approach whereas Bell’s Model 360 has a more conventional main and tail rotor arrangement.
The successful candidate will likely use a large proportion of the larger FLRAA’s subsystems, but as noted above the aircraft are entirely different and the cancellation of one would not fundamentally fell the other.
No total programme numbers have been stated. The S-70/H-60 fleet in US service numbers several thousand and it is not believed that either of the current FVL designs will be produced in similar quantities. Both are – as a rule of thumb – likely to prove more costly than existing aircraft and while offering significant capability improvements, do not essentially need to replace all current models.
The range and speed of the V-280 fits well with the US’s concerns over operational distances in the Pacific theatre, but there are many missions for which the S-70 will still prove perfectly capable. The same is likely to apply to the tiltrotor’s export opportunities, with various potential interested customers, but little likelihood of any service seeking a 1-1 replacement for its current medium helicopter fleet.
Lessons learned from Ukraine will undoubtedly be used to evolve the capability and systems on all projected FVL variants. One common conclusion has been that high speed and low altitude are key to survival, boosted by exploiting poor weather and lighting conditions where aircrews can keep track of threats, but basic air defence systems have greater difficulty with targeting.
Fortunately for the US military, these aspects were built into the performance requirements long before the current conflict and as such the designs in place seem well suited to this type of warfare.
The 2030 in-service objective is somewhat ambitious and may not be fulfilled to the full extent of hopes. With S-70s still being built and upgraded, FVL can afford to slip somewhat, but with operational tempo remaining high for US forces, the advent of newer and more capable designs can be put off only so far before the legacy fleet begins to falter.
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