Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Revenue	$ 25,330	$ 27,777	$ 75,274	$ 84,521
Revenue from Contract with Customer | Customer Concentration Risk | Transferred over Time
Disaggregation of Revenue [Line Items]
Concentration risk			65.00%	60.00%
North America
Disaggregation of Revenue [Line Items]
Revenue	22,794	24,261	$ 62,578	$ 75,532
Europe
Disaggregation of Revenue [Line Items]
Revenue	2,536	3,516	12,696	8,989
Fixed wing aircraft
Disaggregation of Revenue [Line Items]
Revenue	8,941	13,730	28,907	39,130
Rotorcraft
Disaggregation of Revenue [Line Items]
Revenue	6,065	8,687	21,668	22,348
Energy components for power generation units
Disaggregation of Revenue [Line Items]
Revenue	3,199	3,804	14,763	9,879
Commercial product and other revenue
Disaggregation of Revenue [Line Items]
Revenue	7,125	1,556	9,936	13,164
Commercial revenue
Disaggregation of Revenue [Line Items]
Revenue	6,453	12,266	26,453	34,954
Military revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 18,877	$ 15,511	$ 48,821	$ 49,567