Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Disaggregation of Revenue [Line Items]
Revenue	$ 24,568	$ 24,866	$ 43,815	$ 49,944
Revenue from Contract with Customer | Customer Concentration Risk | Transferred over Time
Disaggregation of Revenue [Line Items]
Concentration risk			62.00%	61.00%
North America
Disaggregation of Revenue [Line Items]
Revenue	20,426	20,019	$ 36,288	$ 39,784
Europe
Disaggregation of Revenue [Line Items]
Revenue	4,142	4,847	7,527	10,160
Fixed wing aircraft
Disaggregation of Revenue [Line Items]
Revenue	10,071	10,176	19,960	19,966
Rotorcraft
Disaggregation of Revenue [Line Items]
Revenue	4,371	7,872	7,914	15,603
Energy components for power generation units
Disaggregation of Revenue [Line Items]
Revenue	4,346	5,102	8,003	11,565
Commercial product and other revenue
Disaggregation of Revenue [Line Items]
Revenue	5,780	1,716	7,938	2,810
Commercial revenue
Disaggregation of Revenue [Line Items]
Revenue	9,506	9,247	17,866	20,000
Military revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 15,062	$ 15,619	$ 25,949	$ 29,944