[Code of Federal Regulations]

[Title 14, Volume 1]

[Revised as of January 1, 2006]

From the U.S. Government Printing Office via GPO Access

[CITE: 14CFR21.93]



[Page 132-133]

 

                     TITLE 14--AERONAUTICS AND SPACE

 

CHAPTER I--FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION

 

PART 21_CERTIFICATION PROCEDURES FOR PRODUCTS AND PARTS--Table of Contents

 

                 Subpart D_Changes to Type Certificates

 

Sec. 21.93  Classification of changes in type design.



    (a) In addition to changes in type design 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 appreciable effect on the 

weight, balance, structural strength, reliability, operational 

characteristics, or other characteristics 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:



[[Page 133]]



    (1) Transport category large airplanes.

    (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 external mount), or

    (iii) Time-limited engine and/or nacelle 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 provisions of Part 36 of this chapter is shown for 

that change in type design.

    (3) Propeller driven commuter category and small airplanes in the 

primary, normal, utility, acrobatic, transport, and restricted 

categories, except for airplanes that are:

    (i) Designated for ``agricultural aircraft operations'' (as defined 

in Sec. 137.3 of this chapter, effective January 1, 1966) to which 

Sec. 36.1583 of this chapter does not apply, or

    (ii) Designated for dispensing fire fighting materials to which 

Sec. 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 reconfigured with floats or skis. This 

reconfiguration does not permit further exception from the requirements 

of this section upon any acoustical change not enumerated in Sec. 

21.93(b).

    (4) Helicopters except:

    (i) Those helicopters that are designated exclusively:

    (A) For ``agricultural aircraft operations'', as defined in Sec. 

137.3 of this chapter, as effective on January 1, 1966;

    (B) For dispensing fire fighting materials; or

    (C) For carrying external loads, as defined in Sec. 133.1(b) of 

this chapter, as effective on December 20, 1976.

    (ii) Those helicopters modified by installation or removal of 

external equipment. For purposes of this paragraph, ``external 

equipment'' means any instrument, mechanism, part, apparatus, 

appurtenance, or accessory that is attached to, or extends from, the 

helicopter 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 equipment or external loads, or 

to facilitate the safe operation of the helicopter with external 

equipment mounted to, or external loads carried by, the helicopter;

    (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 removal of external 

equipment, floats, and skis, or flight operations with doors and/or 

windows removed or in an open position.

    (c) For purposes of complying with part 34 of this chapter, any 

voluntary change in the type design of the airplane or engine which may 

increase fuel venting or exhaust emissions is an ``emissions change.''



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



    Editorial Note: For Federal Register citations affecting Sec. 

21.93, see the List of CFR Sections Affected, which appears in the 

Finding Aids section of the printed volume and on GPO Access.