Royalist
"On 8 August 2011, the Japanese Ministry of Defense announced that two aircraft used for ground testing had developed tears in various parts of the craft, including the fuel tank and central part of the fuselage.
Repairs were planned to reinforce the affected areas.
Japan's Maritime Self-Defense Force took delivery of its first two P-1s on 26 March 2013, ahead of a planned two years of test flights. However, the planes were grounded on 14 May 2013, after one developed unstable combustion in some of its engines in flight.
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What you'd expect of an unproven design - why take the risk??? And the cost sseem similar or higher than a P-8