Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 24,873	$ 28,681	$ 81,331	$ 80,726
North America
Disaggregation of Revenue [Line Items]
Revenue	20,301	24,197	68,745	65,544
Europe
Disaggregation of Revenue [Line Items]
Revenue	4,572	4,484	12,586	15,182
Commercial revenue
Disaggregation of Revenue [Line Items]
Revenue	14,713	15,071	41,213	44,091
Military revenue
Disaggregation of Revenue [Line Items]
Revenue	10,160	13,610	40,118	36,635
Fixed wing aircraft
Disaggregation of Revenue [Line Items]
Revenue	12,557	16,087	38,949	43,610
Rotorcraft
Disaggregation of Revenue [Line Items]
Revenue	5,088	5,516	17,261	16,385
Energy components for power generation units
Disaggregation of Revenue [Line Items]
Revenue	4,887	4,629	13,347	16,318
Commercial product and other revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 2,341	$ 2,449	$ 11,774	$ 4,413
Transferred over Time | Revenue from Contract with Customer
Disaggregation of Revenue [Line Items]
Concentration risk			56.00%