SUPPLEMENTAL GUARANTOR INFORMATION - Supplemental Condensed Consolidating Income Statement (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 28, 2019	Dec. 29, 2018
Condensed Income Statements, Captions [Line Items]
Net Income	$ 305	$ 196
LESS: NET INCOME ATTRIBUTABLE TO NONCONTROLLING INTERESTS	(1)	0
NET SALES	1,465	993
COST OF SALES	664	429
GROSS PROFIT	801	564
SELLING AND ADMINISTRATIVE EXPENSES	201	122
AMORTIZATION OF INTANGIBLE ASSETS	40	20
(LOSS) INCOME FROM OPERATIONS	560	422
INTEREST EXPENSE - NET	248	172
REFINANCING COSTS	22	0
OTHER INCOME	(3)	0
EQUITY IN INCOME OF SUBSIDIARIES	0	0
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	293	250
INCOME TAX PROVISION	59	54
INCOME FROM CONTINUING OPERATIONS	234	196
INCOME FROM DISCONTINUED OPERATIONS, NET OF TAX	71	0
NET INCOME ATTRIBUTABLE TO TD GROUP	304	196
OTHER COMPREHENSIVE INCOME, NET OF TAX	127	(85)
TOTAL COMPREHENSIVE INCOME ATTRIBUTABLE TO TD GROUP	431	111
Eliminations
Condensed Income Statements, Captions [Line Items]
Net Income	(797)
LESS: NET INCOME ATTRIBUTABLE TO NONCONTROLLING INTERESTS	0
NET SALES	(57)	(19)
COST OF SALES	(57)	(19)
GROSS PROFIT	0	0
SELLING AND ADMINISTRATIVE EXPENSES	0	0
AMORTIZATION OF INTANGIBLE ASSETS	0	0
(LOSS) INCOME FROM OPERATIONS	0	0
INTEREST EXPENSE - NET	0	0
REFINANCING COSTS	0
OTHER INCOME	0
EQUITY IN INCOME OF SUBSIDIARIES	797	521
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	(797)	(521)
INCOME TAX PROVISION	0	0
INCOME FROM CONTINUING OPERATIONS	(797)
INCOME FROM DISCONTINUED OPERATIONS, NET OF TAX	0
NET INCOME ATTRIBUTABLE TO TD GROUP	(797)	(521)
OTHER COMPREHENSIVE INCOME, NET OF TAX	(180)	75
TOTAL COMPREHENSIVE INCOME ATTRIBUTABLE TO TD GROUP	(977)	(446)
TransDigm Group
Condensed Income Statements, Captions [Line Items]
Net Income	304
LESS: NET INCOME ATTRIBUTABLE TO NONCONTROLLING INTERESTS	0
NET SALES	0	0
COST OF SALES	0	0
GROSS PROFIT	0	0
SELLING AND ADMINISTRATIVE EXPENSES	0	0
AMORTIZATION OF INTANGIBLE ASSETS	0	0
(LOSS) INCOME FROM OPERATIONS	0	0
INTEREST EXPENSE - NET	0	0
REFINANCING COSTS	0
OTHER INCOME	0
EQUITY IN INCOME OF SUBSIDIARIES	(304)	(196)
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	304	196
INCOME TAX PROVISION	0	0
INCOME FROM CONTINUING OPERATIONS	304
INCOME FROM DISCONTINUED OPERATIONS, NET OF TAX	0
NET INCOME ATTRIBUTABLE TO TD GROUP	304	196
OTHER COMPREHENSIVE INCOME, NET OF TAX	127	(85)
TOTAL COMPREHENSIVE INCOME ATTRIBUTABLE TO TD GROUP	431	111
TransDigm Inc.
Condensed Income Statements, Captions [Line Items]
Net Income	304
LESS: NET INCOME ATTRIBUTABLE TO NONCONTROLLING INTERESTS	0
NET SALES	45	41
COST OF SALES	25	23
GROSS PROFIT	20	18
SELLING AND ADMINISTRATIVE EXPENSES	54	41
AMORTIZATION OF INTANGIBLE ASSETS	0	0
(LOSS) INCOME FROM OPERATIONS	(34)	(23)
INTEREST EXPENSE - NET	250	177
REFINANCING COSTS	22
OTHER INCOME	(3)
EQUITY IN INCOME OF SUBSIDIARIES	(493)	(325)
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	190	125
INCOME TAX PROVISION	0	(71)
INCOME FROM CONTINUING OPERATIONS	190
INCOME FROM DISCONTINUED OPERATIONS, NET OF TAX	114
NET INCOME ATTRIBUTABLE TO TD GROUP	304	196
OTHER COMPREHENSIVE INCOME, NET OF TAX	43	(74)
TOTAL COMPREHENSIVE INCOME ATTRIBUTABLE TO TD GROUP	347	122
TransDigm UK [Member]
Condensed Income Statements, Captions [Line Items]
Net Income	9
LESS: NET INCOME ATTRIBUTABLE TO NONCONTROLLING INTERESTS	0
NET SALES	0	0
COST OF SALES	0	0
GROSS PROFIT	0	0
SELLING AND ADMINISTRATIVE EXPENSES	0	0
AMORTIZATION OF INTANGIBLE ASSETS	0	0
(LOSS) INCOME FROM OPERATIONS	0	0
INTEREST EXPENSE - NET	9	5
REFINANCING COSTS	0
OTHER INCOME	(18)
EQUITY IN INCOME OF SUBSIDIARIES	0	0
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	9	(5)
INCOME TAX PROVISION	0	0
INCOME FROM CONTINUING OPERATIONS	9
INCOME FROM DISCONTINUED OPERATIONS, NET OF TAX	0
NET INCOME ATTRIBUTABLE TO TD GROUP	9	(5)
OTHER COMPREHENSIVE INCOME, NET OF TAX	0	0
TOTAL COMPREHENSIVE INCOME ATTRIBUTABLE TO TD GROUP	9	(5)
Subsidiary Guarantors
Condensed Income Statements, Captions [Line Items]
Net Income	476
LESS: NET INCOME ATTRIBUTABLE TO NONCONTROLLING INTERESTS	0
NET SALES	1,130	809
COST OF SALES	480	338
GROSS PROFIT	650	471
SELLING AND ADMINISTRATIVE EXPENSES	97	64
AMORTIZATION OF INTANGIBLE ASSETS	30	18
(LOSS) INCOME FROM OPERATIONS	523	389
INTEREST EXPENSE - NET	(5)	0
REFINANCING COSTS	0
OTHER INCOME	2
EQUITY IN INCOME OF SUBSIDIARIES	0	0
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	526	389
INCOME TAX PROVISION	50	119
INCOME FROM CONTINUING OPERATIONS	476
INCOME FROM DISCONTINUED OPERATIONS, NET OF TAX	0
NET INCOME ATTRIBUTABLE TO TD GROUP	476	270
OTHER COMPREHENSIVE INCOME, NET OF TAX	5	12
TOTAL COMPREHENSIVE INCOME ATTRIBUTABLE TO TD GROUP	481	282
Non- Guarantor Subsidiaries
Condensed Income Statements, Captions [Line Items]
Net Income	9
LESS: NET INCOME ATTRIBUTABLE TO NONCONTROLLING INTERESTS	(1)
NET SALES	347	162
COST OF SALES	216	87
GROSS PROFIT	131	75
SELLING AND ADMINISTRATIVE EXPENSES	50	17
AMORTIZATION OF INTANGIBLE ASSETS	10	2
(LOSS) INCOME FROM OPERATIONS	71	56
INTEREST EXPENSE - NET	(6)	(10)
REFINANCING COSTS	0
OTHER INCOME	16
EQUITY IN INCOME OF SUBSIDIARIES	0	0
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	61	66
INCOME TAX PROVISION	9	6
INCOME FROM CONTINUING OPERATIONS	52
INCOME FROM DISCONTINUED OPERATIONS, NET OF TAX	(43)
NET INCOME ATTRIBUTABLE TO TD GROUP	8	60
OTHER COMPREHENSIVE INCOME, NET OF TAX	132	(13)
TOTAL COMPREHENSIVE INCOME ATTRIBUTABLE TO TD GROUP	$ 140	$ 47