Note 4 - Disaggregation of Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Oct. 31, 2022	Oct. 31, 2021	Oct. 31, 2022	Oct. 31, 2021
Revenues from customers	$ 19,326	$ 18,649	$ 34,629	$ 36,393
Percentage of Completion Contracts [Member]
Revenues from customers	5,624	5,703	8,875	10,978
Transferred at Point in Time [Member]
Revenues from customers	13,702	12,946	25,754	25,415
Casino [Member]
Revenues from customers	7,744	8,042	15,560	16,230
Sportsbook [Member]
Revenues from customers	825	0	825	0
Casino Non-gaming [Member]
Revenues from customers	1,105	1,087	2,182	2,163
Professional Services [Member]
Revenues from customers	71	103	140	164
Aircraft Modification [Member]
Revenues from customers	5,878	5,910	9,714	11,692
Aircraft Avionics [Member]
Revenues from customers	523	665	1,237	1,540
Special Mission Electronics [Member]
Revenues from customers	3,180	2,842	4,971	4,604
Professional Services [Member]
Revenues from customers	9,745	9,232	18,707	18,557
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	9,745	9,232	18,707	18,557
Professional Services [Member] | Casino [Member]
Revenues from customers	7,744	8,042	15,560	16,230
Professional Services [Member] | Sportsbook [Member]
Revenues from customers	825	0	825	0
Professional Services [Member] | Casino Non-gaming [Member]
Revenues from customers	1,105	1,087	2,182	2,163
Professional Services [Member] | Professional Services [Member]
Revenues from customers	71	103	140	164
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	9,581	9,417	15,922	17,836
Aerospace Products [Member] | Percentage of Completion Contracts [Member]
Revenues from customers	5,624	5,703	8,875	10,978
Aerospace Products [Member] | Transferred at Point in Time [Member]
Revenues from customers	3,957	3,714	7,047	6,858
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	5,878	5,910	9,714	11,692
Aerospace Products [Member] | Aircraft Avionics [Member]
Revenues from customers	523	665	1,237	1,540
Aerospace Products [Member] | Special Mission Electronics [Member]
Revenues from customers	3,180	2,842	4,971	4,604
North America [Member]
Revenues from customers	18,043	16,754	33,001	33,520
North America [Member] | Professional Services [Member]
Revenues from customers	9,745	9,232	18,707	18,557
North America [Member] | Aerospace Products [Member]
Revenues from customers	8,298	7,522	14,294	14,963
Europe [Member]
Revenues from customers	124	1,114	306	1,957
Europe [Member] | Professional Services [Member]
Revenues from customers	0	0	0	0
Europe [Member] | Aerospace Products [Member]
Revenues from customers	124	1,114	306	1,957
Asia [Member]
Revenues from customers	274	675	411	763
Asia [Member] | Professional Services [Member]
Revenues from customers	0	0	0	0
Asia [Member] | Aerospace Products [Member]
Revenues from customers	274	675	411	763
Australia and Other [Member]
Revenues from customers	885	106	911	153
Australia and Other [Member] | Professional Services [Member]
Revenues from customers	0	0	0	0
Australia and Other [Member] | Aerospace Products [Member]
Revenues from customers	$ 885	$ 106	$ 911	$ 153