Note 14 - Segment Reporting 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, 2021	Apr. 30, 2020
Top Customer [Member]
Aerospace Products – one customer in 2021, two customers in 2020	10.60%
Aerospace Products [Member] \| Top Customer [Member]
Aerospace Products – one customer in 2021, two customers in 2020	10.60%	32.60%
Professional Services [Member]
Aerospace Products – one customer in 2021, two customers in 2020

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
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-URI http://asc.fasb.org/extlink&oid=123594938&loc=d3e13531-108611

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592

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