Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Revenue	$ 19,247	$ 25,078
Revenue from Contract with Customer | Customer Concentration Risk | Transferred over Time
Disaggregation of Revenue [Line Items]
Concentration risk	57.00%	58.00%
North America
Disaggregation of Revenue [Line Items]
Revenue	$ 15,862	$ 19,766
Europe
Disaggregation of Revenue [Line Items]
Revenue	3,385	5,312
Fixed wing aircraft
Disaggregation of Revenue [Line Items]
Revenue	9,888	9,790
Rotorcraft
Disaggregation of Revenue [Line Items]
Revenue	3,544	7,731
Energy components for power generation units
Disaggregation of Revenue [Line Items]
Revenue	3,657	6,462
Commercial product and other revenue
Disaggregation of Revenue [Line Items]
Revenue	2,158	1,095
Commercial revenue
Disaggregation of Revenue [Line Items]
Revenue	8,360	10,753
Military revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 10,887	$ 14,325