Note 4 - Disaggregation of Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 31, 2023	Jan. 31, 2022	Jan. 31, 2023	Jan. 31, 2022
Revenues from customers	$ 20,464	$ 17,618	$ 55,093	$ 54,012
Percentage of Completion Contracts [Member]
Revenues from customers	6,875	4,899	15,750	15,877
Transferred at Point in Time [Member]
Revenues from customers	13,589	12,719	39,343	38,135
Casino [Member]
Revenues from customers	7,210	7,741	22,769	23,972
Sportsbook [Member]
Revenues from customers	1,160	0	1,985	0
Casino Non-gaming [Member]
Revenues from customers	1,102	1,059	3,284	3,222
Professional Services [Member]
Revenues from customers	102	102	242	266
Aircraft Modification [Member]
Revenues from customers	7,188	5,394	16,902	17,086
Aircraft Avionics [Member]
Revenues from customers	679	485	1,917	2,025
Special Mission Electronics [Member]
Revenues from customers	3,023	2,837	7,994	7,441
Professional Services [Member]
Revenues from customers	9,574	8,902	28,280	27,460
Professional Services [Member] | Percentage of Completion Contracts [Member]
Revenues from customers	0	0	0	0
Professional Services [Member] | Transferred at Point in Time [Member]
Revenues from customers	9,574	8,902	28,280	27,460
Professional Services [Member] | Casino [Member]
Revenues from customers	7,210	7,741	22,769	23,972
Professional Services [Member] | Sportsbook [Member]
Revenues from customers	1,160	0	1,985	0
Professional Services [Member] | Casino Non-gaming [Member]
Revenues from customers	1,102	1,059	3,284	3,222
Professional Services [Member] | Professional Services [Member]
Revenues from customers	102	102	242	266
Professional Services [Member] | Aircraft Modification [Member]
Revenues from customers	0	0	0	0
Professional Services [Member] | Aircraft Avionics [Member]
Revenues from customers	0	0	0	0
Professional Services [Member] | Special Mission Electronics [Member]
Revenues from customers	0	0	0	0
Aerospace Products [Member]
Revenues from customers	10,890	8,716	26,813	26,552
Aerospace Products [Member] | Percentage of Completion Contracts [Member]
Revenues from customers	6,875	4,899	15,750	15,877
Aerospace Products [Member] | Transferred at Point in Time [Member]
Revenues from customers	4,015	3,817	11,063	10,675
Aerospace Products [Member] | Casino [Member]
Revenues from customers	0	0	0	0
Aerospace Products [Member] | Sportsbook [Member]
Revenues from customers	0	0	0	0
Aerospace Products [Member] | Casino Non-gaming [Member]
Revenues from customers	0	0	0	0
Aerospace Products [Member] | Professional Services [Member]
Revenues from customers	0	0	0	0
Aerospace Products [Member] | Aircraft Modification [Member]
Revenues from customers	7,188	5,394	16,902	17,086
Aerospace Products [Member] | Aircraft Avionics [Member]
Revenues from customers	679	485	1,917	2,025
Aerospace Products [Member] | Special Mission Electronics [Member]
Revenues from customers	3,023	2,837	7,994	7,441
North America [Member]
Revenues from customers	17,832	16,520	50,833	50,042
North America [Member] | Professional Services [Member]
Revenues from customers	9,574	8,902	28,280	27,460
North America [Member] | Aerospace Products [Member]
Revenues from customers	8,258	7,618	22,553	22,582
Europe [Member]
Revenues from customers	90	578	396	2,535
Europe [Member] | Professional Services [Member]
Revenues from customers	0	0	0	0
Europe [Member] | Aerospace Products [Member]
Revenues from customers	90	578	396	2,535
Asia [Member]
Revenues from customers	92	93	503	856
Asia [Member] | Professional Services [Member]
Revenues from customers	0	0	0	0
Asia [Member] | Aerospace Products [Member]
Revenues from customers	92	93	503	856
Australia and Other [Member]
Revenues from customers	2,450	427	3,361	579
Australia and Other [Member] | Professional Services [Member]
Revenues from customers	0	0	0	0
Australia and Other [Member] | Aerospace Products [Member]
Revenues from customers	$ 2,450	$ 427	$ 3,361	$ 579