BASIS OF PRESENTATION (Details)	3 Months Ended		9 Months Ended
	Jan. 31, 2019 USD ($) item	Jan. 31, 2018 USD ($)	Jan. 31, 2019 USD ($) item	Jan. 31, 2018 USD ($)	May 01, 2018 USD ($)	Apr. 30, 2018 USD ($)
Revenue from Contracts with Customers
Number of primary product revenue streams | item	2		2
Revenue from contracts with performance obligations satisfied over time	90.00%		90.00%
Assets
Contract assets	$ 1,003,000		$ 1,003,000		$ 102,000
Inventories	2,897,000		2,897,000			$ 2,362,000
Equity
Accumulated deficit	(9,058,000)		(9,058,000)		(8,641,000)	$ (8,743,000)
Net sales	4,750,000	$ 4,529,000	14,097,000	$ 13,742,000
Cost of goods sold	3,680,000	3,091,000	9,874,000	9,686,000
Gross profit	1,070,000	1,438,000	4,223,000	4,056,000
Loss from operations	(370,000)	31,000	(333,000)	(533,000)
Loss before income tax expense	(406,000)	3,000	(417,000)	(586,000)
Net loss	(406,000)	(307,000)	(417,000)	(671,000)
Net loss	$ (406,000)	$ (307,000)	(417,000)	(671,000)
Contract assets			(901,000)
Inventories			(535,000)	(214,000)
Net cash used in operating activities			$ (590,000)	$ (462,000)
Aerospace and defense industries
Revenue from Contracts with Customers
Percentage of revenue	90.00%		90.00%
Industrial and commercial
Revenue from Contracts with Customers
Percentage of revenue	7.00%		7.00%
ASU 2014-09 | Balances Without Adoption of ASC 606
Assets
Inventories	$ 3,404,000		$ 3,404,000
Equity
Accumulated deficit	(8,562,000)		(8,562,000)
Net sales	4,214,000		13,094,000
Cost of goods sold	3,377,000		9,367,000
Gross profit	837,000		3,727,000
Loss from operations	(603,000)		(829,000)
Loss before income tax expense	(639,000)		(913,000)
Net loss	(639,000)		(913,000)
Net loss			(913,000)
Inventories			(1,042,000)
Net cash used in operating activities			(590,000)
ASU 2014-09 | Effect of Change Higher/(Lower)
Assets
Contract assets	1,003,000		1,003,000		102,000
Inventories	(507,000)		(507,000)
Equity
Accumulated deficit	(496,000)		(496,000)		$ 102,000
Net sales	536,000		1,003,000
Cost of goods sold	303,000		507,000
Gross profit	233,000		496,000
Loss from operations	233,000		496,000
Loss before income tax expense	233,000		496,000
Net loss	$ 233,000		496,000
Net loss			496,000
Contract assets			(901,000)
Inventories			$ 507,000