The original design concept for the LHA was to be alerted of a mission and starting from cold Iron build up a head of steam, load the troops and equipment and in eleven days or less be steaming in a two mile oval off the coast to be invaded. Granted this was pre V-22 and pre LCAC. The original design mission used a fleet of CH-53s and CH-46s along with a smattering of UH-1s and conventional landing craft. Now the LHAs are forward deployed and the 1800 marines are already on board. They will at some point have the V-22s on board but they will still have a contingent of large helicopters aboard as well as AV8-B Harriers. Since there is limited hangar space on the LHA, the numbers of each type aircraft will be limited. So, if they are twenty miles or more offshore the effectiveness of the V-22 may be shown up but the helicopters will have to fly further so there is a tradeoff in overall effectiveness.
The LHAs presently in the Persian Gulf are conventionally equipped with the exception of the LCACs however the troops and their equipment are already on shore so the original design concept is already out the window. If the V-22s were involved in the present day scenario they would be no more efficient than the helicopters and with the atmospheric conditions existent in the desert it would be stupid to send the V-22s in to support the troops fighting in the desert.
Over
