Note 15 - Segment Reporting and Sales by Major Customer - Professional Services (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 31, 2022	Jan. 31, 2021	Jan. 31, 2022	Jan. 31, 2021
Revenues from customers	$ 18,132	$ 14,612	$ 55,369	$ 43,572
Interest expense	725	758	1,979	2,411
Depreciation and amortization	699	740	2,106	2,858
Operating income (loss)	4,402	1,868	13,167	3,683
Gaming [Member]
Revenues from customers	9,314	7,843	28,551	20,706
Interest expense	668	682	1,792	2,166
Depreciation and amortization	562	617	1,714	2,499
Operating income (loss)	2,867	1,924	9,486	2,935
Aircraft Modification [Member]
Revenues from customers	5,394	4,472	17,086	15,206
Interest expense	49	62	157	194
Depreciation and amortization	44	49	133	142
Operating income (loss)	1,464	705	3,852	2,092
Aircraft Avionics [Member]
Revenues from customers	485	569	2,025	2,109
Interest expense	0	0	0	0
Depreciation and amortization	3	3	6	6
Operating income (loss)	(132)	(102)	(265)	0
Special Mission Electronics [Member]
Revenues from customers	2,837	1,670	7,441	5,356
Interest expense	6	6	17	20
Depreciation and amortization	45	34	115	99
Operating income (loss)	1,380	607	3,368	1,726
Product and Service, Other [Member]
Revenues from customers	102	58	266	195
Interest expense	2	8	13	31
Depreciation and amortization	45	37	138	112
Operating income (loss)	$ (1,177)	$ (1,266)	$ (3,274)	$ (3,070)