IIRC the Mission System for MRA4 and P-8 were very similar and essentially a BAESYSTEMS/Boeing collaborative project. The Indian P-8s have a Magnetic Anomaly Detector (MAD) boom whereas the rest do not. It is understood that due to its normal operating height the P-8 would find the MAD of limited value and is better off carrying 3,000lbs of extra fuel. Further, there are many new high-fidelity techniques - both acoustic, active and off-board that effectively renders a MAD not worth all of the effort.
As for MRA4's airframe: conceived in 1943, first flew 1949, maritime role conceived 1964, first flew 1967, then bastardised in the 90s with new engines and wings with a variety of build issues dating back from the time when the fuselages were built in wooden jigs. It is understood MRA4 had too small a tailplane/rudder to cope with the new engines and a workaround had to be found for loss of engine(s) at slow speed. There were build quality issues. Some of the control circuits were understood to be at the back of the bomb bay and so opening it at low level and taking a bird could have been catastrophic. It is understood that the RAF were asked to accept the aircraft with a speed limitation on the bomb bay and without a sonobuoy dropping clearance - not a lot of good for a maritime aircraft! Finally, it appeared that we had learned nothing from the sad loss of the MR2 in having fuel, heat and a source of ignition in enclosed zones without fire detection and extinguishing systems. We should have pulled the plug on the programme several times but the need outweighed common-sense judgement on many occasions; plus the good old 'Buy British' flag waivers had been allowed to get carried away without realising at that point that BAESYSTEMS is a
global company.
Thankfully all will end up as it should have 10 years ago - a fleet of Boeing P-8 Poseidon with RAF roundels on them. It's just a shame we didn't do it earlier.
All in my humble opinion of course...
LJ
