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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 

equipment; 

(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-
copter; 

(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] 

E

DITORIAL

N

OTE

: For F

EDERAL

R

EGISTER

ci-

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

§ 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 
data. 

§ 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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