Maybe because the Osprey don't meet specifications. Surf the web and check out the specs. Not only is the Osprey more expensive, it has about half the load and considerably less range. Keep in mind the Osprey is designed for use by the Marine Corps off amphibious ships.
If you compare V22 against DHC-4 Caribou they actually compare favourably,9T payload compared to 3.6T range is shorter in the V22,same amount of pax and no need for a landing strip, but remember that all that DHC-4/V22 can do so can the CH-47F at about half the fly away cost .
C17/C130J will become the long haul oversize lift, C27J intra theatre lift, CH-47F tactical lift to troops in the field.
an old paper for AIR 5190
AIR 5190 analysis
AIR 5190 Phase 2: Light Tactical Airlift Capability
Aircraft will be a replacement for the current Caribou. Phase is also likely to provide for a Level 5 full-flight simulator. Possible options could include platforms such as the CN295 ((sic)), C27J, V22 Osprey or Chinook. Replacement options may be affected by solutions for AIR 5414 Phase 1 C-130H Refurbishment and recommendations flowing from an ongoing Airlift Study.
YOD 2004/05. RFT release 2005/06. Contract 2006/07. In-service delivery 2010.
Scale of expenditure: $750m - $1000m.
Within AIR 5190, industry expects iteration but not so much as to fundamentally change the nature of the project. In its studies Defence has exhaustively analysed the LTAC several times. Evidently each time a definite decision was reached, it was for LTA rather than more C-130s and/or more CH-47s while possibly accepting separately that more of each would be useful. So the next ITR or RFP is likely to resemble the 'definitive' RFT issued to the primes on 1 May 1998. Nevertheless DCP2001 implies that AIR 5190 might be revised to acquire additional Hercules - C-130Js or KC-130Js - instead of LTA. Parameters indicate that an almost fully loaded C-27J or C-295M (or a fully loaded CH-47D or V-22B) can readily land and takeoff from short and confined airstrips unusable by a C-130J and which the latter could not approach for a LAPES delivery. Also the system cost of adding five C-130Js is similar to the system cost of adding 12 CH-47Ds or introducing 8 CV-22Bs, 10 C-27Js, or 14 C-295Ms. Operating costs might favour the smaller number of Hercules but they would provide less concurrency.
Repetitive proposal of the V-22 as a viable candidate for AIR 5190 may result from Air Force attempts to reclaim a position in VTOL operations but it is more likely to reflect concern for the prompt recovery of downed aircrew. Army might see the V-22 as useful for interdiction but not if that led to a reduction in the number of utility helicopters. The V-22 has not been included in any publicly released list of candidates for the land/ship-based utility helicopters. As addressed in AIR 5406 Phases 5/6, these could be a marinised version of the Blackhawk with some commonality also with 16 Seahawk anti-submarine and surface warfare helicopters operated by Navy. The main alternatives are the Sea King and various derivatives of the Iroquois.
Examination of photographs indicates the hanger door of the 9,000 tonne amphibious warfare ships Kanimbla and Manoora is high enough to admit an HV or MV-22 but that probably only one could be accommodated. These ships reach their expected design life in 2015. Their replacement is to be considered under joint project JP 2027 Phase 4 with a YOD of 2009/10. Navy has one other 6,000 tonne amphibious warfare ship. This has a smaller hanger, and reaches its expected design life in 2010. The CV-22 could be less costly to acquire than the HV or MV-22 which have the wing swivel system for maritime stowage. If however the HV/MV-22 is unlikely to be acquired on the grounds of performance and cost for ADF land/ship-based operations, then it is unlikely that a similar number of CV-22s would be acquired for ADF land-based operations. If size was the deciding factor, then AIR 5190 is the only current project that might acquire the V-22.
The main argument for the V-22 is its capability for VTOL and the main argument against is the inefficiency of its highly loaded wing when used as a STOL aircraft. If one rotor was disabled in STOL mode, the V-22 could recover to an expedient airstrip. It is more expensive than the competitors and would provide less concurrency but it is an outstanding technical achievement. So this could be an instance of an unusually effective system versus a more efficient or notionally cost-effective alternative. The power needed to drive its rotors for VTOL does translate into a heavy potential payload in STOL mode but the V-22 cabin is smaller than that of the Caribou. Its capacity is non-compliant with the troop/paratroop and vehicle loads specified as essential in the ITR for AIR 5190.
