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Federal Aviation Administration, DOT 

§ 21.93 

(1) The modification involved in the 

amendment to the type certificate has 
been designed and constructed in ac-
cordance with the airworthiness re-
quirements applicable to the issue of 
the type certificate for the aircraft; 

(2) The aircraft substantially com-

plies with the applicable flight char-
acteristic requirements for the type 
certificate; and 

(3) The aircraft can be operated safe-

ly under the appropriate operating lim-
itations in this subchapter. 

(f) The applicant must submit a re-

port showing that the aircraft incor-
porating the modifications involved 
has been flown in all maneuvers nec-
essary to show compliance with the 
flight requirements applicable to those 
modifications and to establish that the 
aircraft can be operated safely in ac-
cordance with the limitations specified 
in §§ 91.317 and 121.207 of this chapter. 

(g) The applicant must establish and 

publish, in a provisional aircraft flight 
manual or other document and on ap-
propriate placards, all limitations re-
quired for the issue of the type certifi-
cate applied for, including weight, 
speed, flight maneuvers, loading, and 
operation of controls and equipment, 
unless, for each limitation not so es-
tablished, appropriate operating re-
strictions are established for the air-

(h) The applicant must establish an 

inspection and maintenance program 
for the continued airworthiness of the 

(i) The applicant must operate a pro-

totype aircraft modified in accordance 
with the corresponding amendment to 
the type certificate for the number of 
hours found necessary by the FAA. 

[Amdt. 21–12, 31 FR 13388, Oct. 15, 1966, as 
amended by Amdt. 21–66, 54 FR 34329, Aug. 18, 

Subpart D—Changes to Type 




: Docket No. 5085, 29 FR 14567, Oct. 

24, 1964, unless otherwise noted. 

§ 21.91


This subpart prescribes procedural 

requirements for the approval of 
changes to type certificates. 

§ 21.93

Classification of changes in 

type design. 

(a) In addition to changes in type de-

sign specified in paragraph (b) of this 
section, changes in type design are 
classified as minor and major. A 
‘‘minor change’’ is one that has no ap-
preciable effect on the weight, balance, 
structural strength, reliability, oper-
ational characteristics, or other char-
acteristics affecting the airworthiness 
of the product. All other changes are 
‘‘major changes’’ (except as provided in 
paragraph (b) of this section). 

(b) For the purpose of complying 

with Part 36 of this chapter, and except 
as provided in paragraphs (b)(2), (b)(3), 
and (b)(4) of this section, any voluntary 
change in the type design of an aircraft 
that may increase the noise levels of 
that aircraft is an ‘‘acoustical change’’ 
(in addition to being a minor or major 
change as classified in paragraph (a) of 
this section) for the following aircraft: 

(1) Transport category large air-


(2) Jet (Turbojet powered) airplanes 

(regardless of category). For airplanes 
to which this paragraph applies, 
‘‘acoustical changes’’ do not include 
changes in type design that are limited 
to one of the following— 

(i) Gear down flight with one or more 

retractable landing gear down during 
the entire flight, or 

(ii) Spare engine and nacelle carriage 

external to the skin of the airplane 
(and return of the pylon or other exter-
nal mount), or 

(iii) Time-limited engine and/or na-

celle changes, where the change in type 
design specifies that the airplane may 
not be operated for a period of more 
than 90 days unless compliance with 
the applicable acoustical change provi-
sions of Part 36 of this chapter is shown 
for that change in type design. 

(3) Propeller driven commuter cat-

egory and small airplanes in the pri-
mary, normal, utility, acrobatic, trans-
port, and restricted categories, except 
for airplanes that are: 

(i) Designated for ‘‘agricultural air-

craft operations’’ (as defined in § 137.3 
of this chapter, effective January 1, 
1966) to which § 36.1583 of this chapter 
does not apply, or 

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