There look to be two patterns of the large box on the raised platform at the front of the M901 launcher. I believe this is the generator.
The first pattern has various recesses and grills and looks to be common on most US Patriots. The later pattern is simpler with two large doors per side.
Trumpeter’s PAC-3 when purchased singly seems to have the first pattern.
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...but their M901/M983 PAC-3 combo seems to have the second pattern.
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So far, I’ve only seen photos of the second pattern on Japanese Patriots. Does anybody have photos of the later pattern on US-operated Patriots? So far no joy from Google, so any help is much appreciated.