SIM_XPlane: fix memory problems #42843

Job	Run time
build (base)	4m 44s
build (clang)	2m 3s
build-gcc-heli	2m 15s
autotest-heli (sitltest-heli)	10m 20s
autotest (sitltest-copter-tests1a)	7m 44s
autotest (sitltest-copter-tests1b)	9m 22s
autotest (sitltest-copter-tests1c)	11m 34s
autotest (sitltest-copter-tests1d)	8m 58s
autotest (sitltest-copter-tests1e)	9m 49s
autotest (sitltest-copter-tests2a)	9m 4s
autotest (sitltest-copter-tests2b)	31m 2s
	1h 46m 55s

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