Boeing and Sikorsky have grounded their prototype SB>1 Defiant superior compound helicopter after simply three flight assessments whereas they make modifications to the propulsion system. Continued points with the drivetrain had already delayed the primary flight, which lastly occurred in March 2019, by a further three months.
Chris Van Buiten, Vice President of Innovation at Sikorsky, which is now a division of Lockheed Martin, disclosed the change within the Defiant’s flight check schedule throughout a media occasion on the firm’s flight check facility in West Palm Seashore, Florida, on June 24, 2019. Boeing and Sikorsky have been working collectively on the SB>1 as a part of the U.S. Military’s Joint Multi-Position (JMR) superior expertise demonstration program and the 2 firms are proposing the design for the follow-on Future Lengthy Vary Assault Plane (FLRAA) program, which The Conflict Zone has beforehand coated intimately right here. FLRAA is a part of the over-arching Future Vertical Carry (FVL) program, which is searching for replacements for the entire Military’s present helicopters.
“We’re going via a tweak proper now and the PSTB [propulsion system test bed] is working with some modifications and we’re about to restart the flight assessments and, , we hope to march proper via the pace factors and , you’ve got seen it prior to now,” Van Buiten mentioned. “We moved the pace out [in] 20-, 40-knot increments.”
The aim is for the Defiant to finally show a cruising pace of 250 knots, considerably quicker than conventional helicopters in the identical normal weight class, such because the Military’s present UH-60 Black Hawks. The SB>1 makes use of a compound helicopter configuration with a pair of co-axial essential rotor blades on high, in addition to a pusher propeller within the rear, to realize this high-speed flight.
The design relies on classes realized from the equally configured Sikorsky’s X2 demonstrator and S-97 Raider compound helicopters. The S-97 has a demonstrated hurries up 220 knots, although it’s considerably smaller than the SB>1. Earlier this 12 months, The Conflict Zone carried out an in-depth interview with quite a lot of Sikorsky representatives, together with Van Buiten, discussing all three of those helicopters intimately, which you could find right here.
The video beneath exhibits the S-97 placing on a powerful efficiency on the latest media occasion in Florida.
Throughout the first two assessments in March and April 2019, “the crew proved out the anticipated pace for these assessments: 10 knots ahead, left, proper and rearward,” Van Buiten instructed reporters. “It additionally proved out hover efficiency maneuverability, pedal turns, and a hover ladder from floor stage as much as 30 ft altitude.”
The outcomes of the third flight are unclear and Van Buiten declined to supply specifics in regards to the cause for the pause in testing, saying he couldn’t present extra particulars with out Boeing representatives additionally current. As famous, although, this isn’t the primary time propulsion system issues have cropped up within the SB>1’s growth.
Boeing and Sikorsky had hoped the primary flight would happen in December 2018, already a 12 months not on time, however pushed that date again once more after coming throughout unspecified points throughout earlier testing of the PSTB. Bell’s V-280 Valor tilt-rotor, the opposite plane flying within the JMR expertise demonstration, which can also be set to be an FLRAA competitor, has been flying since December 2017 and has already demonstrated speeds in extra of 280 knots.
“Typically its instrumentation that was put in [that didn’t] get the measurements we have been hoping to get, or the software program wasn’t studying correctly,” Randy Rotte, the Director of Enterprise Improvement for Cargo Helicopters and Future Vertical Carry program at Boeing, instructed FlightGlobal on the time.
“It’s nothing that’s going to require a redesign of main parts or any of these items,” Rotte had added, insisting that the problems have been comparatively minor. “It’s candidly just a few interactions that the fashions didn’t all seize.”
Although we do not know what the issue is now, or whether or not it’s associated to those earlier points, it’s price stating that movies that Boeing and Sikorsky have launched of floor testing in January 2019 and of the primary flight in March 2019 don’t present the pusher propeller working.
This might merely mirror the established testing plan and the character of preliminary check factors. Van Buiten mentioned the Defiant had fulfilled the entire assigned check necessities to this point.
Nonetheless, it’s price noting that the S-97’s rear propeller was working throughout its first flight in 2015, regardless of equally restricted necessities. Up to now, there don’t seem like any movies or footage of the SB>1 with its pusher propeller working.
Regardless of the problem or points are, Van Buiten is optimistic that the Defiant can be flying once more quickly. “Over the summer season of 2019 we count on to broaden the envelope in flight assessments with extra pace and maneuverability and supply the U.S. Military with the mandatory, sturdy, and related knowledge in a well timed method that may allow them to make absolutely knowledgeable choices as they pursue the Future Vertical Carry program,” he defined.
However Boeing and Sikorsky could possibly be dealing with an more and more tight schedule now, it doesn’t matter what. The JMR program is about to finish this 12 months.
The Military might resolve to increase it, however has not indicated that it plans to take action. The service is already transferring forward with the follow-on FLRAA and is seeking to choose a ultimate design in 2021. The Military’s aim, because it stands now, is to start changing its UH-60 Black Hawks with no matter plane it picks by 2030.
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