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Note 10 - Industry Segmentation and Sales by Major Customer (Details Textual)	12 Months Ended
	Apr. 30, 2017
Number of Operating Segments	2
Customer Concentration Risk [Member] \| Sales Revenue, Net [Member] \| The Five Aerospace Customers [Member]
Concentration Risk, Percentage	25.20%
Customer Concentration Risk [Member] \| Sales Revenue, Net [Member] \| Top Customer [Member]
Concentration Risk, Percentage	10.50%
Customer Concentration Risk [Member] \| Sales Revenue, Net [Member] \| Next Top Four Customers [Member] \| Minimum [Member]
Concentration Risk, Percentage	0.90%
Customer Concentration Risk [Member] \| Sales Revenue, Net [Member] \| Next Top Four Customers [Member] \| Maximum [Member]
Concentration Risk, Percentage	9.20%