Feature 2 | AMPHIBIOUS/LOGISTICS VESSELS
LCAC’s fuel – but take over four times as long to complete. Te BMT fast landing craſt will straddle these rates, burning 315 US gallons an hour, using 525 US gallons to deliver the payload 40nm (but taking 40 minutes longer). The following tables compare broad
speed and estimated fuel consumption data from the US LCAC, a UK LCU Mk 10, the Tribow FLC and the US Amphibious Assault Vehicle (AAV), showing time taken to deliver combat loads to beaches at 30nm and 12nm. A common offload time of 5 minutes, and a reload time of 10 minutes, has been added to each assault wave interval period. Tere are some roles that are far better
BMT’s Caimen 90 is a shaped monohull with a ‘Tribow’ design; it has been tank tested to deliver a 90tonne load at 24knots, and 40knots when unloaded
a far more detrimental impact on a loaded LCAC’s operating speed. There are other associated penalties
with operating LCACs. High daily and routine maintenance rates reflect both the complexity and cost of a gas turbine against a diesel engine, and the vulnerability of some LCAC components such as the skirt. Te twin gas turbine
engines have a high fuel use rate, at approximately 1,000 US gallons per hour (with payload) to transit 40nm. Compare this to a UK LCU Mk 10,
which carries a similar payload. In the same hour it will consume approximately 70 US gallons – but will only travel 9-10nm. To deliver the same payload the same distance, the LCU will use less than a third of the
Table 1: Performance figures - 12nm to beach
Planning Speed (knots)
LCAC (H) 40
LCU Mk 10 10 FLC
AAV 12
Planning Speed (knots)
LCAC (H) 40
LCU Mk 10 10 FLC
AAV 40 12
24 out/40 return
24 out/40 return
1st wave on beach
18 mins 72 mins 30 mins
60 mins Table 2: Performance figures - 30nm to beach
1st wave on beach
45 mins
2nd wave on beach
3rd wave on beach
150 mins 255 mins
180 mins 555 mins 930 mins 75 mins
210 mins 345 mins 150 mins
Estimate of total fuel used (US Gallons)
4,250 1,085
1,1811 53
2nd wave on beach
69 mins
3rd wave on beach
120 mins
231 mins 390 mins 98 mins
166 mins
Estimate of total fuel used (US Gallons)
2,000 455 872
21
suited to the displacement landing craft than a hovercraft, exploiting its ability to operate for extended periods independently, or as part of a boat group temporarily detached from its parent platforms. Te ability to patrol, loiter, moor, anchor
and beach, all at distant range, allows the LCU to act as a floating command post/mother craft for boarding operations or riverine patrols, with smaller assault craſt using it as a refuelling, maintenance and accommodation base from which to operate for days or weeks. Such capabilities can be extended for disaster assistance and humanitarian relief roles, including logistical and medical support, the movement of plant and heavy equipment, a diving platform or ferry operations. Developments in hul lform
hydrodynamic design have now freed the landing craſt utility from its ‘floating skip’ reputation. Te step change increase in performance offers a surface connector that can meet the demands of increased operating range and de-risk this vital link of the amphibious chain. Tey provide a compelling alternative to heavy LCACs for those forces that cannot justify the resources necessary to operate this impressive capability. And for LCAC equipped navies, a fast landing craft’s heavy payload lift, reductions in dock footprint, fuel use and maintenance regime, matched with a capacity for wider amphibious roles, provides a complimentary capability to operate on similar terms alongside these larger surface connectors. WT
Warship Technology October 2014
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