Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Revenue	$ 25,078	$ 26,207
Revenue from Contract with Customer | Transferred over Time
Disaggregation of Revenue [Line Items]
Concentration risk	58.00%	61.00%
North America
Disaggregation of Revenue [Line Items]
Revenue	$ 19,766	$ 23,776
Europe
Disaggregation of Revenue [Line Items]
Revenue	5,312	2,431
Fixed wing aircraft
Disaggregation of Revenue [Line Items]
Revenue	9,790	11,335
Rotorcraft
Disaggregation of Revenue [Line Items]
Revenue	7,731	6,848
Energy components for power generation units
Disaggregation of Revenue [Line Items]
Revenue	6,462	2,658
Commercial product and other revenue
Disaggregation of Revenue [Line Items]
Revenue	1,095	5,366
Commercial revenue
Disaggregation of Revenue [Line Items]
Revenue	10,753	10,191
Military revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 14,325	$ 16,016