Note 12 - Industry Segmentation and Sales by Major Customer - Schedule of Revenue by Major Customers by Reporting Segments (Details) - Customer Concentration Risk [Member] - Revenue Benchmark [Member]	12 Months Ended
	Apr. 30, 2020	Apr. 30, 2019
Top Customer [Member]
Concentration risk percentage	21.20%
Aerospace Products [Member] | Top Customer [Member]
Concentration risk percentage	32.60%	15.10%
Professional Services [Member]
Concentration risk percentage