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Is/was STVOL aircraft worth it, considering its limitations versus its advantages

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  • J-20
    Rank 4 Registered User
    • Jan 2018
    • 141

    Is/was STVOL aircraft worth it, considering its limitations versus its advantages

    Now that we have quite a few STVOL aircraft built and experiences (a variety of harriers, F-35B, and I guess the Yaks..)

    in retrospect has its advantages versus its disadvantages made acquiring them worth it?

    Limitations: more complicated machines, extra expenses, lots of dead weight that limit performance. usually less range and payload. Harder to train pilots
    Advantages: obviously, doesn't need as much runway. More flexibility in operations

    at least theoretically. maybe some people think its flexibility is not as useful as it seems. maybe others think its a very important asset. maybe some think newer technologies have negated a lot of the previous limitations?

    lets look at 2 areas


    1. Sea-based STVOL

    2. Ground based STVOL
  • LMFS
    Rank 4 Registered User
    • Feb 2018
    • 470

    #2
    There are all kinds of opinions on this topic, but IMHO:

    - Ground based STOVL makes little to no sense, now high TWR fighters can take off and land in a mater of 300 m. It is simply impossible to destroy the roads and runways of a country to the extent that not healthy stretch of this length can be found.

    - Sea based STOVL makes sense on LHDs only. STOBAR fighters, contrary to widely spread belief, can take off full or almost full weight if they have a decent TWR and good aero design. For A2A roles no restriction, for A2G only on certain cases and specially for militaries like that of the US, where land strike role is a main need. For most countries this is not relevant.

    Main advantages of STOVL nowadays:

    - Notably boost capabilities of LHDs and similar vessels, so they can operate in a bigger number of scenarios without support of a full-blown carrier.
    - Increase the resilience of a carrier regarding the effects that even small damages on the deck would have, essentially rendering it unable to operate its air wing. I (strictly personally) think this could be addressed with newer designs (both of the carrier and of the air wing) where alternative landing trajectories can be used, without the need of developing STOVL planes.

    For a manned fighter of the layouts we know, it is unavoidable to pay a serious price in terms of weight, fuel capacity, weapons payload, cost, complexity, reliability and layout (i.e. best place for placement of weapons bays not available due to the lifting HW) by using STOVL. A possibility would be on a unmanned fighter, where the cockpit would be replaced by the vertical lift-generating HW, with very good effects on layout and propulsion and essentially allowing to pay a way smaller price for the STOVL function than when placing these lifting devices close to the CoG of the plane.

    So, for a scenario where performance is not critical, a STOVL can make sense (namely LHDs deployed to relatively low-risk areas), for the highest performance required from the naval fighters in charge of defending the fleet from peer rivals, I don't really see the need for the jump jets.

    Comment

    • paralay
      Rank 5 Registered User
      • Aug 2005
      • 1396

      #3
      By total combat effectiveness:

      F-35B loses F-35A - 13%
      F-35B loses F-35C - 9%

      instead, it has an advantage in survival and the ability to base on unprepared sites.

      http://paralay.world/paralay_tab.xls

      Comment

      • LMFS
        Rank 4 Registered User
        • Feb 2018
        • 470

        #4
        F-35B is IMO the most accomplished STOVL fighter ever. But:

        > You cannot consider the A or C versions as independent from the B one, since the general layout of the three versions is influenced by the need to have one with STOVL capability. In all variants engine is displaced to the front, elements crowded around the CoG, cross sectional area is huge, weapons bays are suboptimal, weight is very big.
        > C version is 2.5 T heavier than the A one, that is a massive 19% increase, due to the basic version being very far from the requirements of naval application. Not every naval plane has such differences with the CTOL version. Wing in particular was not appropriate for the needed approach speed, so it grew substantially, adding drag and weight in big amounts.
        > Between C and B versions: C has 47% more fuel, 20% more payload, notably bigger weapon bays and 7% higher overload capability. How this translates into combat effectiveness would be the matter for a discussion of its own I think.

        Comment

        • eagle
          Rank 5 Registered User
          • Jan 2000
          • 2352

          #5
          Originally posted by LMFS View Post
          - Ground based STOVL makes little to no sense, now high TWR fighters can take off and land in a mater of 300 m. It is simply impossible to destroy the roads and runways of a country to the extent that not healthy stretch of this length can be found.
          Which fighter can take off and land on a 300 m strip? With ordnance of course. Answer: none.

          The closest to that is the Gripen. It can operate from a 600 m strip, probably not with a heavy load though.

          How can less be more? It's impossible. More is more.
          Yngwie Malmsteen

          Comment

          • LMFS
            Rank 4 Registered User
            • Feb 2018
            • 470

            #6
            Originally posted by eagle View Post

            Which fighter can take off and land on a 300 m strip? With ordnance of course. Answer: none.

            The closest to that is the Gripen. It can operate from a 600 m strip, probably not with a heavy load though.
            Those are rough figures considered for Su-57. Half lading distance of a Su-35 ca. 375 m, for the Su-35 take-off run at normal TO weight 450-600 m. Maybe I exaggerated a bit, but it does not matter a lot if the run is 400 m instead of 300. The core of the point is that with modern, properly designed fighters you don't need long runways. And if that was a big problem, springboards would be already available at the air bases.

            Comment

            • eagle
              Rank 5 Registered User
              • Jan 2000
              • 2352

              #7
              So Su-35 landing distance is 750 m and it has been cut in half for the Su-57?
              I'll believe it when I see it.
              600 m take off run is certainly possible but it is already 2 times 300 m.

              Until then, there's only the Swedish fighters that have been optimised for STOL and they need 600 - 800 meters.

              For reference, here's the F-16C Block 52 landing distance, on a dry runway, with brake chute and full brakes. Worse conditions increase landing distance obviously.
              Click image for larger version

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              How can less be more? It's impossible. More is more.
              Yngwie Malmsteen

              Comment

              • LMFS
                Rank 4 Registered User
                • Feb 2018
                • 470

                #8
                eagle

                Just for sake of being factually correct:

                > Su-57 has been explicitly designed as STOL

                https://z5h64q92x9.net/proxy_u/ru-en.../samolety/410/

                > Reference to half landing distance of the Su-35 was stated by current chief designer (Mikhail Strelets) at the Zvezda documentary about the Su-57 end of last year.

                >Data for the Su-35

                from UAC:
                TO run@normal weight = 500 m
                Landing @normal landing weight with brakes and chute = 750 m

                Old KNAAPO booklet referred at Air Power Australia:
                Take-off run in "full afterburning" mode with standard take-off weight, m 400-450
                Landing roll on concrete runway in braking mode with brake parachute and wheel brakes use, with standard landing weight, m 650

                Comment

                • FBW
                  FBW
                  Rank 5 Registered User
                  • Dec 2011
                  • 3287

                  #9
                  What characteristics make the Su-57 capable of STOL?
                  Does it have thrust reversers? No
                  Does it have air brakes (outside of control surface deflection like many aircraft)? No
                  Does it have special braking system? Not specified in any literature.
                  Does it have the inherent light weight, low landing speed of aircraft meant for rough/short field landings? No.

                  like the adage any aircraft can be a glider once, in ideal conditions many aircraft can land on a shorter runway in optimal conditions and light loads. But its neither practical, nor practiced.

                  Comment

                  • Al.
                    Al.
                    Rank 5 Registered User
                    • Nov 2008
                    • 1003

                    #10
                    For Naval operations STOVL has three big advantages (which is not trivialise the cost, range and payload penalties which ARE significant).

                    The flat top does not have to turn into the wind for launch. That's not just a convenience issue it can make the path and location of said carrier and its escorts far less predictable.
                    'Stopping and then landing' rather than 'landing and then stopping' imposes less (and fewer) stresses on the airframe and is supposedly an easier skill to master (I've never tried either method outside of a consumer simulator so I cannot claim great personal insight).
                    Operations can continue in far less benign weather conditions (not an issue on the pacific which is pacific but it was certainly a factor down south in the winter).
                    Rule zero: don't be on fire

                    Comment

                    • Ozair
                      Rank 5 Registered User
                      • Oct 2015
                      • 813

                      #11
                      Originally posted by Al. View Post
                      For Naval operations STOVL has three big advantages (which is not trivialise the cost, range and payload penalties which ARE significant).

                      The flat top does not have to turn into the wind for launch. That's not just a convenience issue it can make the path and location of said carrier and its escorts far less predictable.
                      Sailing into the wind is standard for F-35B operations. It lowers take off distance and increases payload.

                      Originally posted by Al. View Post
                      'Stopping and then landing' rather than 'landing and then stopping' imposes less (and fewer) stresses on the airframe and is supposedly an easier skill to master (I've never tried either method outside of a consumer simulator so I cannot claim great personal insight).
                      Operations can continue in far less benign weather conditions (not an issue on the pacific which is pacific but it was certainly a factor down south in the winter).
                      A good reference I have seen for landing the F-35B is here, https://www.aerosociety.com/news/uk-...proach-to-qec/

                      So, what is the F-35B like to fly? Thanks to the pioneering work of UK's DERA (now DSTL/QinetiQ) VAAC Harrier testbeds and test pilots like Justin Paines and John Farley in developing advanced FBW software for VTOL aircraft it is extremely simple. Whereas the Jedi-like skills are needed to control the Harrier in the hover requires movement of throttle, nozzle control and stick and has been likened to 'balancing on the top of a pencil while needing three hands', the F-35Bs fly-by-wire controls are just a sidestick and throttle HOTAS - with the flight computers doing all the hard work. (It is noteworthy that the UK is the only country after the US to have its own lines of code in in the F-35 software).

                      To assist pilots coming into land, there are two velocity vectors - a traditional one, and a ship-shaped one - showing where the ship will be. The ships speed is also entered into the flight management computer via the touchscreen display.

                      Approaching the ship from behind at around 170kt and 500ft, once at 200ft the pilot hits the 'brake' deceleration button and the aircraft begins slowing and transitioning to a hover, with the LiftFan engaging and the rear nozzle swivelling down for vertical flight. Once slowed down, the pilot can swing to the left side of the ship. The aircraft's flight computers now cleverly match the ship's speed, with the pilot pushing forward on the control sidestick (or inceptor) to go down. At 100ft and about a wingspan across from the deck, the pilot is thus ready to transition sideways over the deck, with fine hovering control being provided by the moving rear nozzle, LiftFan and the STOVL roll jets at the tips of the wings. At this point, with the flight controls engaged and the aircraft happily matching speed with the ship, the pilot can even take his (or her) hands off the controls - a move that would most likely be suicidal in the Harrier for the average squadron pilot.

                      Hitting another thumb switch on the HOTAS throttle engages a translational controller mode, enabling the pilot to slide across in the hover and line up with the centreline. Once in position it is a case of pushing forward on the sidestick to a software-controlled stop to descend and put the aircraft firmly on the deck. At this point, control of the engine thrust and vertical motion has passed to the right hand, rather than the left hand - which on the first occasion is slightly disconcerting to push full forward on what is normally a pitch control, some 50ft above a deck.

                      Those raised on Call of Duty Xbox controllers will have no problems. Feet on the brakes and the aircraft lands itself. Effectively with these flight controls you are flying an aeroplane that cannot stall and where intuitive pull back/go up and push forward/go down still work - even when hovering. Says BAE: "The control philosophy is such that the left-hand commands go-faster / go-slower whilst the right-hand commands the aircraft to go-up / go-down and go-left / go-right. Each hand commands a response in the same axis in both wing-borne and jet-borne flight." It is not quite the 'take me home and land the aircraft automatically coffee bar button' that legendary Harrier test pilot John Farley often joked about as something that a future VTOL fighter would need, but it is close.
                      SVRL factors in a wind over deck of approx 25kts.

                      When executing an SRVL recovery, a pilot descends the aircraft to a 200ft plateau to line up and decelerate, before flying short finals along a 7˚ glideslope at a speed of approximately 60kt (110km/h). Assuming 25kt wind over the deck, this equates to a 35kt overtake speed. The pilot can fly a manual approach or engage "Delta Flight Path" mode to automatically fly the glideslope with minimum intervention.
                      https://www.flightglobal.com/news/ar...trials-454087/


                      Comment

                      • Ozair
                        Rank 5 Registered User
                        • Oct 2015
                        • 813

                        #12
                        Originally posted by eagle View Post
                        So Su-35 landing distance is 750 m and it has been cut in half for the Su-57?
                        I'll believe it when I see it.
                        600 m take off run is certainly possible but it is already 2 times 300 m.

                        Until then, there's only the Swedish fighters that have been optimised for STOL and they need 600 - 800 meters.

                        For reference, here's the F-16C Block 52 landing distance, on a dry runway, with brake chute and full brakes. Worse conditions increase landing distance obviously.
                        F-16 isn't a good example though as it really doesn't like to land...

                        Comment

                        • LMFS
                          Rank 4 Registered User
                          • Feb 2018
                          • 470

                          #13
                          Originally posted by FBW View Post
                          What characteristics make the Su-57 capable of STOL?
                          Does it have thrust reversers? No
                          Does it have air brakes (outside of control surface deflection like many aircraft)? No
                          Does it have special braking system? Not specified in any literature.
                          Does it have the inherent light weight, low landing speed of aircraft meant for rough/short field landings? No.

                          like the adage any aircraft can be a glider once, in ideal conditions many aircraft can land on a shorter runway in optimal conditions and light loads. But its neither practical, nor practiced.
                          Are you correcting me, M. Strelets or Sukhoi? I am just transmitting their claims.

                          Yours are not quite tight either: the plane IS meant for rough field landings, has an over-dimensioned undercarriage and braking system + braking chute + full movable keels as air brake and is designed to have remarkable high AoA / low speed controllability beyond that of the Flankers. If the claim is that Sukhoi is lying, then I think you would need stronger evidence. If it is simply that you don't know how do they manage the STOL characteristics, then I already submitted my theory on that regard.

                          Comment

                          • J-20
                            Rank 4 Registered User
                            • Jan 2018
                            • 141

                            #14
                            Originally posted by Al. View Post
                            For Naval operations STOVL has three big advantages (which is not trivialise the cost, range and payload penalties which ARE significant).

                            The flat top does not have to turn into the wind for launch. That's not just a convenience issue it can make the path and location of said carrier and its escorts far less predictable.
                            'Stopping and then landing' rather than 'landing and then stopping' imposes less (and fewer) stresses on the airframe and is supposedly an easier skill to master (I've never tried either method outside of a consumer simulator so I cannot claim great personal insight).
                            Operations can continue in far less benign weather conditions (not an issue on the pacific which is pacific but it was certainly a factor down south in the winter).
                            while LMFS and FBW are debating.. it does seem like the only consensus here? is Naval operations has some advantages for STOVL
                            not so much for land based operations

                            Comment

                            • Ozair
                              Rank 5 Registered User
                              • Oct 2015
                              • 813

                              #15
                              Originally posted by J-20 View Post

                              while LMFS and FBW are debating.. it does seem like the only consensus here? is Naval operations has some advantages for STOVL
                              not so much for land based operations
                              STOVL clearly has application for land based operations but it really depends on the respective Air Force. Were more Air Forces inclined to change their doctrine and embrace distributed operations to a greater extent then STOVL would be more common, noting that STOVL is more expensive than conventional operations which probably limits the take up especially in the post cold war budget world.

                              The future takeup of STOVL is probably dependent on how hypersonics and DEW emerge. Hypersonics may make airbase defence significantly more difficult while lasers may also make airbase defence easier. DEW will allow airbases to operate reasonably freely from threat but hypersonics will likely allow rapid targeting and engagement of pop up targets.

                              Finally I expect that STOVL will become more common in fighter aviation although likely as loyal wingman than manned aircraft, for example what will come out of the Tempest program.

                              Answering questions in the House of Commons, the Minister of State, Ministry of Defence (MoD), Deputy Leader of the House of Lords, Earl Howe, said that the Tempest needs to be compatible with the Royal Navy's two new Queen Elizabeth-class aircraft carriers, and that the concept currently being considered is that the UAV 'loyal wingmen' will be ship-based rather than the fighter itself.
                              https://www.janes.com/article/86417/...arrier-capable

                              No reason that a STOVL UCAV couldn't operate from land based FOBs as well as naval platforms.

                              Comment

                              • sandiego89
                                Rank 5 Registered User
                                • Feb 2008
                                • 353

                                #16
                                The main "advantage" for Naval applications is that it allows some countries to enter the carrier/LHD game that would not otherwise be able to be able to afford conventional aircraft operations, which are massively expensive to build, maintain and man. Spain, Italy, the UK, India and Thailand could only afford STOVL carriers at various times. Japan and perhaps Australia to perhaps follow.

                                - Conventional carriers need to be large to operate effective aircraft. This comes at a massive cost to build and operate. A STOVL carrier can be smaller, slower, with no need for extensive catapults, arresting gear and the crews to operate them. Nuclear/steam is ideal for a large supercarrier due to speed, range and frequent speed fluctuation requirements for flight operations, but is unaffordable for most.
                                - STOVL aircrews do not require nearly the same level of initial or currency training. The F-35B has been described as quite intuitive to and straightforward to bring aboard the ship. Reduced aircrew training requirements was cited as a major reason for the UK choosing to go STOVL (after initially being first STOVL, then cat and trap for a few years, then back to STOVL). Cost of the carriers was likely the major factor .

                                The whole concept of dispersed land based operations had been a major part of UK and USMC harrier operational doctrine, but in practice rarely proved essential (and likely a good thing, especially for a European WWIII scenario)

                                Comment

                                • TomcatViP
                                  Rank 5 Registered User
                                  • Nov 2011
                                  • 6001

                                  #17
                                  Don't forget that dispersed STOVL allow a fewer number of airframe to log a greater nbr of operational sorties. Dispersed operation being more than ever a prerequisite for operating close to the FLOT.

                                  I have also talked about this extensively in the past but IMOHO STOVL allows small countries with higher asset cost to divest expensive infrastructure and relocate their airbase farther away from population centers without inducing the prohibitive high cost that comes with CTOL airframe fleet.

                                  If/when the public will become fully familiar with STOVL on demand mobility (and this seems to be something that will come quite soon as this industry market it), invariably taxpayers will turn toward their airforces demanding more than ever justifications for the perceived nuisance of military jets. When this time comes, the accusations of failure will be a natural temptation for the public.
                                  Last edited by TomcatViP; 30th May 2019, 14:55.

                                  Comment

                                  • djcross
                                    Rank 5 Registered User
                                    • Jan 2000
                                    • 5417

                                    #18
                                    USMC Harrier dispersed flight operations choked after the first few sorties as equipment breakage and resupply became the primary hindrance to sortie generation. Consolidated operations at a forward operating base did not experience a drop in sortie rate because supplies and maintenance were present at the FOB. F-35B should be no different from Harrier in that respect.

                                    Comment

                                    • TomcatViP
                                      Rank 5 Registered User
                                      • Nov 2011
                                      • 6001

                                      #19
                                      Absolutely something to be expected when no STOL cargo delivery system was fielded. Today, you have one one hand the drastic reduction of ordinance tonnage per target destroyed and on the other the availability of platforms able to deliver vertically a massive increase of cargo (CH-53K, autonomous rotary wing assets...).
                                      This (taking many shortcuts to say that in a few words) put aviation in the same field today as forward operating helicopters has done for many years.

                                      Comment

                                      • Sanem
                                        Rank 5 Registered User
                                        • Oct 2010
                                        • 590

                                        #20
                                        Well we might see revival of STOVL aircraft as new UCAV designs mature.

                                        DARPA and the USN planned to have Tern, a prop tailsitter demonstrator, flying by late 2018. But the USN took over the program and has gone quiet since then.
                                        The USN is now also looking to field larger drones and cranes that can launch and catch drones, so there might be possibilities there too.

                                        But the most interesting and mature design is probably the UTAP-22, which is essentially an upgraded BQM-167A, meaning it's a proven platform.
                                        Production is said to start this year, and Kratos has been given approval to export them to close allies.
                                        This system could VTOL an aircraft that can fly out 1600 miles at 50,000 feet and Mach 0.9 with a small but deadly payload.
                                        This means that any ship with even a small helipad can launch and recover these for as little as $2 million a piece.

                                        Possible payloads would include:
                                        - 1 SDB + 4 Hellfires
                                        - 6 Hellfires
                                        - 1 AMRAAM + 4 Stingers
                                        - 2 Sidewinders + 4 Stingers
                                        - 16 Stingers
                                        - 2 R-73 + 2 R-60
                                        - 7 R-60

                                        I mention the Russian missiles because India has already shown interesting to buy the Avenger UCAV, and is also looking to find a way to increase its naval force projection.
                                        With their current need to update their forces to balance Pakistan and China, they'd be a strong potential user of such aircraft.
                                        They could also be launched close to border area's for example, anywhere a truck can reach really.

                                        Comment

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