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Federal Aviation Administration, DOT 

§ 21.101 

(1) If the FAA finds that design 

changes are necessary to correct the 
unsafe condition of the product, and 
upon his request, submit appropriate 
design changes for approval; and 

(2) Upon approval of the design 

changes, make available the descrip-
tive data covering the changes to all 
operators of products previously cer-
tificated under the type certificate. 

(b) In a case where there are no cur-

rent unsafe conditions, but the FAA or 
the holder of the type certificate finds 
through service experience that 
changes in type design will contribute 
to the safety of the product, the holder 
of the type certificate may submit ap-
propriate design changes for approval. 
Upon approval of the changes, the man-
ufacturer must make information on 
the design changes available to all op-
erators of the same type of product. 

[Doc. No. 5085, 29 FR 14567, Oct. 24, 1964, as 
amended by Amdt. 21–3, 30 FR 8826, July 24, 

§ 21.101

Designation of applicable reg-


(a) An applicant for a change to a 

type certificate must show that the 
change and areas affected by the 
change comply with the airworthiness 
requirements applicable to the cat-
egory of the product in effect on the 
date of the application for the change 
and with parts 34 and 36 of this chapter. 
Exceptions are detailed in paragraphs 
(b) and (c) of this section. 

(b) Except as provided in paragraph 

(g) of this section, if paragraphs (b)(1), 
(2), or (3) of this section apply, an ap-
plicant may show that the change and 
areas affected by the change comply 
with an earlier amendment of a regula-
tion required by paragraph (a) of this 
section, and of any other regulation 
the FAA finds is directly related. How-
ever, the earlier amended regulation 
may not precede either the cor-
responding regulation included by ref-
erence in the type certificate, or any 
regulation in §§ 25.2, 27.2, or 29.2 of this 
chapter that is related to the change. 
The applicant may show compliance 
with an earlier amendment of a regula-
tion for any of the following: 

(1) A change that the FAA finds not 

to be significant. In determining 
whether a specific change is signifi-

cant, the FAA considers the change in 
context with all previous relevant de-
sign changes and all related revisions 
to the applicable regulations incor-
porated in the type certificate for the 
product. Changes that meet one of the 
following criteria are automatically 
considered significant: 

(i) The general configuration or the 

principles of construction are not re-

(ii) The assumptions used for certifi-

cation of the product to be changed do 
not remain valid. 

(2) Each area, system, component, 

equipment, or appliance that the FAA 
finds is not affected by the change. 

(3) Each area, system, component, 

equipment, or appliance that is af-
fected by the change, for which the 
FAA finds that compliance with a reg-
ulation described in paragraph (a) of 
this section would not contribute ma-
terially to the level of safety of the 
product or would be impractical. 

(c) An applicant for a change to an 

aircraft (other than a rotorcraft) of 
6,000 pounds or less maximum weight, 
to a non-turbine rotorcraft of 3,000 
pounds or less maximum weight, to a 
level 1 low-speed airplane, or to a level 
2 low-speed airplane may show that the 
change and areas affected by the 
change comply with the regulations in-
cluded in the type certificate. However, 
if the FAA finds that the change is sig-
nificant in an area, the FAA may des-
ignate compliance with an amendment 
to the regulation incorporated by ref-
erence in the type certificate that ap-
plies to the change and any regulation 
that the FAA finds is directly related, 
unless the FAA also finds that compli-
ance with that amendment or regula-
tion would not contribute materially 
to the level of safety of the product or 
would be impractical. 

(d) If the FAA finds that the regula-

tions in effect on the date of the appli-
cation for the change do not provide 
adequate standards with respect to the 
proposed change because of a novel or 
unusual design feature, the applicant 
must also comply with special condi-
tions, and amendments to those special 
conditions, prescribed under the provi-
sions of § 21.16, to provide a level of 
safety equal to that established by the 

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