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14 CFR Ch. I (1–1–18 Edition) 

§ 21.95 

(ii) Designated for dispensing fire 

fighting materials to which § 36.1583 of 
this chapter does not apply, or 

(iii) U.S. registered, and that had 

flight time prior to January 1, 1955 or 

(iv) Land configured aircraft recon-

figured with floats or skis. This recon-
figuration does not permit further ex-
ception from the requirements of this 
section upon any acoustical change not 
enumerated in § 21.93(b). 

(4) Helicopters except: 
(i) Those helicopters that are des-

ignated exclusively: 

(A) For ‘‘agricultural aircraft oper-

ations’’, as defined in § 137.3 of this 
chapter, as effective on January 1, 1966; 

(B) For dispensing fire fighting mate-

rials; or 

(C) For carrying external loads, as 

defined in § 133.1(b) of this chapter, as 
effective on December 20, 1976. 

(ii) Those helicopters modified by in-

stallation or removal of external equip-
ment. For purposes of this paragraph, 
‘‘external equipment’’ means any in-
strument, mechanism, part, apparatus, 
appurtenance, or accessory that is at-
tached to, or extends from, the heli-
copter exterior but is not used nor is 
intended to be used in operating or 
controlling a helicopter in flight and is 
not part of an airframe or engine. An 
‘‘acoustical change’’ does not include: 

(A) Addition or removal of external 


(B) Changes in the airframe made to 

accommodate the addition or removal 
of external equipment, to provide for 
an external load attaching means, to 
facilitate the use of external equip-
ment or external loads, or to facilitate 
the safe operation of the helicopter 
with external equipment mounted to, 
or external loads carried by, the heli-

(C) Reconfiguration of the helicopter 

by the addition or removal of floats 
and skis; 

(D) Flight with one or more doors 

and/or windows removed or in an open 
position; or 

(E) Any changes in the operational 

limitations placed on the helicopter as 
a consequence of the addition or re-
moval of external equipment, floats, 
and skis, or flight operations with 
doors and/or windows removed or in an 
open position. 

(5) Tiltrotors. 
(c) For purposes of complying with 

part 34 of this chapter, any voluntary 
change in the type design of the air-
plane or engine which may increase 
fuel venting or exhaust emissions is an 
‘‘emissions change.’’ 

[Amdt. 21–27, 34 FR 18363, Nov. 18, 1969] 





: For F





tations affecting § 21.93, see the List of CFR 
Sections Affected, which appears in the 
Finding Aids section of the printed volume 
and at 

§ 21.95

Approval of minor changes in 

type design. 

Minor changes in a type design may 

be approved under a method acceptable 
to the FAA before submitting to the 
FAA any substantiating or descriptive 

§ 21.97

Approval of major changes in 

type design. 

(a) An applicant for approval of a 

major change in type design must— 

(1) Provide substantiating data and 

necessary descriptive data for inclu-
sion in the type design; 

(2) Show that the change and areas 

affected by the change comply with the 
applicable requirements of this sub-
chapter, and provide the FAA the 
means by which such compliance has 
been shown; and 

(3) Provide a statement certifying 

that the applicant has complied with 
the applicable requirements. 

(b) Approval of a major change in the 

type design of an aircraft engine is lim-
ited to the specific engine configura-
tion upon which the change is made 
unless the applicant identifies in the 
necessary descriptive data for inclu-
sion in the type design the other con-
figurations of the same engine type for 
which approval is requested and shows 
that the change is compatible with the 
other configurations. 

[Amdt. 21–40, 39 FR 35459, Oct. 1, 1974, as 
amended by Amdt. 21–92, 74 FR 53387, Oct. 16, 
2009; Amdt. 21–96, 77 FR 71695, Dec. 4, 2012] 

§ 21.99

Required design changes. 

(a) When an Airworthiness Directive 

is issued under Part 39 the holder of 
the type certificate for the product 
concerned must— 

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