Dr Bevilaqua developed the F-35-B lift fan
for the Short Takeoff / Vertical Landing (STOVL) variant of the Joint
Strike Fighter. He discussed the history of attempts to create a vertical landing fighter aircraft. The Harrier is the only successful such aircraft so far, using a ducted turbofan engine, but is not supersonic. The problem was to create an aircraft with the speed of an F-18, but land vertically like a Harrier.
The F-18's engines have only half the thrust needed to land vertically. Also engine's thrust is at the back of the aircraft and so the solution was to balance with with a shaft driven fan at the front. In retrospect this sounds obvious, but as Dr Bevilaqua pointed out that previously engines were either used as a turbojet or turbo-shaft, not both. Research shows the the combination is possible with only a small drop in power.
Interestingly Dr Bevilaqua's initial sketch for the aircraft has the lift fan mounted horizontally in front of the turbojet, with two nozzles to direct the air down, as with the Harrier. The final design for the F-35B has the fan vertical, so no nozzles are required. However, it seems to me this gives up some subsonic efficiency, as the fan is not used in forward flight (as it is in the Harrier). It might be possible to have an annular fan with a clutch. This would be shut down at high speed, but operate as a turbofan at low speed, then with additional doors open, direct air down for vertical landing.
Dr Bevilaqua pointed out that the stealth features of the F-35 are not designed to make the aircraft completely invisible to radar, just hard to spot from some angles.
Dr Bevilaqua related how the design of the VSTOL aircraft was turned into an idea for a conventional aircraft, simply by taking out the lift fan and replacing it with a fuel tank. He related how previous such "joint" designs had a bad reputation in the US DoD due to the TFX project (which resulted in the F-111 which Australia purchased).
One interesting part of the talk was the approach to making the prototypes of the X-35. 3-D printing was used to produce plastic mock-ups of the parts, so the companies making them had a full size template for making metal parts.
Dr Bevilaqua explained that the three variants of the F-35: Airforce, Beach and Carrier have essentially the same fuselage with some different components attached.
Australia is planning to order the conventional take-off
F-35A, which does not use a lift fan. Dr Bevilaqua explained that the US Marines have had their own air-support using Harrier aircraft and the F-35B is the supersonic replacement for it. Air support for amphibious operations is very relevant to the Australian Army, which is re-equipping itself to operate from Australia's two new Canberra Class amphibious assault ships. These ships have flight decks specifically designed for the Harrier and the F-35B STOVL aircraft. I have suggested Australia order eighteen F-35b aircraft, to equip the ships.
ps: The event was organised by the American Institute of Aeronautics and Astronautics - Australia. They
showed a very cheesy video promoting AIAA and aerospace technology.
What got my attention was that AIIA membership is free for school
teachers.
4 comments:
Very interesting! Did he touch on the safety aspects at all? One of the problems associated with buying kit from overseas (particularly the US) is the different safety regimes. The UK regulations - and presumably the Australian ones - can require different safety evidence from the US requirements.
Very interesting to hear about the use of 3D printing too; it's good to see it being taken up for things like this.
Actually the Canberra class LHDs can only 'lilypad' the F-35B - i.e. an F-35B can land and take off, but there is no means to stage the F-35B from the LHDs in the same way they can from say a Wasp class LHD in the USN. This was a deliberate design strategy with the LHDs to preclude the LHDs becoming seen as 'mini-carriers' or paving the way towards Australian acquisition of an aircraft carrier capability. Furthermore, acquisition of the F-35B was not supported within Defence due to the fact that it would drive the carrier debate, which is formally discouraged within the organisation.
Catherine Menon said May 01, 2014 9:21 PM:
> Did he touch on the safety aspects at all? ...
No, Dr Bevilaqua did not comment on safety aspects of the F-35. But he did say it had a higher than required thrust to weight ratio, making landings safer. Also it has "fences" similar to the Harrier, cushioning the vertical landing.
Differences in regulatory requirements have been a problem in the past when Australia has purchased aircraft developed overseas. But this has been more of a problem with bespoke development for Australia, and less of a problem with off-the-self purchases, which the F-35A is.
> Very interesting to hear about the use of 3D printing ...
Yes, the use of the 3D printing to produce a mock-up of the part is useful. It will be interesting to see how much this is used to make actual aircraft parts in the future. The maintenance depot might then not need to stock any parts. ;-)
Blogger Malcolm Davis said May 02, 2014 9:50 AM:
> Actually the Canberra class LHDs can only 'lilypad' the F-35B ...
Yes, the F-35B will be able to land and take off from Australia's new Landing Helicopter Dock Ships, but the ships are not being fitted out to service, fuel or rearm them.
> This was a deliberate design strategy with the LHDs to preclude the LHDs becoming seen as 'mini-carriers' ...
Yes, my understanding was that there was a vigorous debate in Defence over what STOVL capability to have on the LHD. I was told by "sources" that the retention of the ski-jump ramp was justified on cost grounds, when really it was kept to allow for future VSTOL use. But ILS was not included.
If a decision was made to equipment the LHDs with F-35Bs, this could be done relatively quickly and simply, adding some electronics and putting the required facilities in transportable shipping containers.
My suggestion would be for the RAN to invite the USN to send F-35Bs to Darwin for the commemoration of the bombing of Darwin, shortly before the next election. Friends of the RAN could then leak to the press that the Indonesian Navy was considering buying Chinese aircraft carriers.
TV news footage of a Chinese aircraft carrier, interspersed with old newsreels of Darwin being bombed would cause panic in the PM's office. In response, the RAN could arrange for the PM to announce the order of F-35Bs, standing on the deck of a LHD in front of the aircraft.
If that sounds far fetched, look at the video of the PM announcing ordering of the Triton UAV, standing in front of one, just before the SA election. ;-)
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