= §4a.1 Scope.

GENERAL

The airworthiness requirements set forth in this part shall be used as a basis for obtaining airworthiness or type certificates: Provided, That: (a) Deviations from the requirements of this part which, in the opinion of the Administrator, insure the equivalent condition for safe operation and, (b) equivalent requirements of the United States Army or Navy with respect to airworthiness may be accepted in lieu of the requirements set forth in this part. Unless

otherwise specified an amendment to this part will apply only to airplanes for which applications for type certificates are received subsequent to the effective date of such amendment.

(b) All sections not designated by a suffix are applicable to all categories, except as otherwise specified. [Amdt. 04-3, 7 F. R. 984, Feb. 14, 1942] AIRWORTHINESS AND TYPE CERTIFICATES

§ 4a.15 Requirements for issuance.

The airworthiness requirements specified in this part shall be used as a basis for the certification of airplanes: Provided, That an airplane manufactured in accordance with, and conforming to, the currently effective aircraft specifications issued therefor will be eligible for an airworthiness certificate, if the Administrator determines such airplane is in condition for safe operation: Provided, further, That an airplane which has not demonstrated compliance with the airworthiness requirements specified in this part but which, in the opinion of the Administrator, is in condition for safe operation for experimental purposes or for particular activities will be eligible for an airworthiness certificate.

§ 4a.16 Data required for airworthiness certificate.

When an airworthiness certificate is sought and a type certificate is not involved, data which are adequate to establish compliance of the aircraft with the requirements listed in this part shall be submitted to the Administrator.

§ 4a.17 Data required for type certifi

cate.

(Applicable to all airplanes certifilcated as a type on or after May 15, 1947.) After proof of compliance with the structural requirements contained in this part, and upon completion of all necessary inspection and testing on the ground, and proof of the conformity of the airplane with the type design, and upon receipt from the applicant of a report of flight tests conducted by him, there shall be conducted such official flight tests as the Administrator finds necessary to determine compliance with Subparts C-G. After the conclusion of these flight tests such additional flight tests shall be conducted as the Administrator finds necessary to ascertain whether there is reasonable assurance that the airplane, its components, and equipment are reliable and function properly. The extent of such additional flight tests shall depend upon the complexity of the airplane, the number and nature of new design features, and the record of previous tests and experience for the particular airplane model, its

components, and equipment. If practicable, the flight tests performed for the purpose of ascertaining the reliability and proper functioning shall be conducted on the same airplane which was used in flight tests to show compliance with Subparts C-G.

[Amdt. 048-6, 12 F. R. 1029, Feb. 13, 1947, as amended by Amdt. 048-7, 12 F. R. 2087, Mar. 29, 1947]

§ 4a.20 Procedure for type certification.

Acceptable procedures for type certification are outlined in Civil Aeronautics Manual 4.

CHANGES

§ 4a.25 Continued compliance.

Changes to certificated aircraft shall be substantiated to demonstrate continued compliance of the aircraft with the pertinent airworthiness requirements.

§ 4a.26 Minor changes.

Minor changes to airplanes being manufactured under the terms of a type certificate and which obviously do not impair the condition of the airplane for safe operation may be approved by authorized representatives of the Administrator prior to submittal to the Administrator of any required revised drawings. The approval of such minor changes shall be based on the airworthiness requirements in effect when the particular airplane model was originally certificated, unless, in the opinion of the Administrator, compliance with current airworthiness requirements is necessary. § 4a.27 Major changes.

Major changes to airplanes being manufactured under the terms of a type certificate may require the issuance of a new type certificate and the Administrator may, in his discretion, require such changes to comply with current airworthiness requirements.

§ 4a.28 Changes required by the Administrator.

(a) In the case of aircraft models approved under the airworthiness requirements in effect prior to the currently effective regulations, the Administrator may require that aircraft submitted for original airworthiness certification comply with such portions of the currently effective regulations as are considered necessary.

(b) All aircraft certificated under the transport category, the manufacture of which is completed after September 30, 1947, shall comply with the following sections of Part 4b of this subchapter, as amended: §§ 4b.58, 4b.442, 4b.445 (a), 4b.447, 4b.478, 4b.484, 4b.503 (c), 4b.5164b.518, 4b.556, 4b.557, 4b.560, 4b.561, 4b.586, 4b.621-4b.624, 4b.651-4b.655, 4b.661-4b.676 (14 F. R. 4102, July 16, 1949).

[Amdt. 48, 5 F. R. 1834, May 22, 1940, as amended by Amdt. 04-4, 11 F. R. 11353, Oct. 4, 1946; Amdt. 04a-8, 12 F. R. 5959, Sept. 9, 1947]

APPROVAL OF MATERIALS, PARTS, PROCESSES, AND APPLIANCES

(a) Materials, parts, processes, and appliances shall be approved upon a basis and in a manner found necessary by the Administrator to implement the pertinent provisions of the regulations in this subchapter. The Administrator may adopt and publish such specifications as he finds necessary to administer this section, and shall incorporate therein such portions of the aviation industry, Federal, and military specifications respecting such materials, parts," processes, and appliances as he finds appropriate.

(b) Any material, part, process, or appliance shall be deemed to have met the requirements for approval when it meets the pertinent specifications adopted by the Administrator, and the manufacturer so certifies in a manner prescribed by the Administrator.

[Amdt. 04a-1, 12 F. R. 7898, Nov. 25, 1947] § 4a.31-1 Approval of aircraft components (FAA rules which apply to § 4a.31).

Aircraft components made the subject of Technical Standard Orders shall be approved upon the basis and in the manner provided in Part 514 of this title. [Supp. 9, 16 F. R. 671, Jan. 25, 1951]

Subpart B-Definitions

SOURCE: § 4a.37 to 4a.46 contained in Civil Air Regulations, May 31, 1938, as amended by Amendment 75, 5 F. R. 3946, Oct. 8, 1940. except as otherwise noted.

§ 4a.37 Weights.

(a) Weight, W. The total weight of the airplane and its contents.

(b) Design weight. The weight of the airplane assumed for purposes of show

compliance with the structural reirements specified in this part.

(c) Minimum design weight. Weight pty with standard equipment, plus w, plus fuel of 0.25 pound per maxiim (except take-off) horsepower, plus as per capacity.

(d) Standard weight. The maximum ight for which the airplane is certified as complying with all the airrthiness requirements for normal rations.

e) Provisional weight. The maxim weight for which the airplane is tificated as complying with the airthiness requirements as modified for eduled air carriers in §§ 4a.687.

R, May 31, 1938, as amended at 15 F. R. , Aug. 8, 1950]

a) Design wing area, S. The area losed by the projection of the wing ine, including ailerons and flaps but ring fairings and fillets, on a sur

containing the wing chords. The ine is assumed to extend through elles and through the fuselage to the e of symmetry.

›) Design power, P. The total enhorsepower chosen for use in detering the maneuvering load factors. corresponding engine output will be rporated in the aircraft certificate maximum operational limitation in light operations other than take-off limbing flight (see § 4a.727). ) Design wing loading, W/S. n weight (§ 4a.37 (b)) divided by lesign wing area (paragraph (a) of section).

The

› Design power loading, W/P. The n weight (§ 4a.37 (b)) divided by lesign power (see paragraph (b) of section and Fig. 4a-3).

, May 31, 1938, as amended by Amdt. 5, 1171, Mar. 9, 1939]

39 Air density, p.

e mass density of the air through the airplane is moving, in terms e weight of a unit volume of air d by the acceleration of gravity. ymbol po denotes the mass density at sea level under standard atmos> conditions and has the value of #78 slugs per cubic foot.

is REFERENCE: For definition of standmosphere, see § 4a.45.

§ 4a.40 Speed.

(a) True air speed, Vt. The velocity of the airplane, along its flight path, with respect to the body of air through which the airplane is moving.

(b) Indicated air speed, V. The true air speed multiplied by the term Vp/po. (See § 4a.39.)

(c) Design level speed, VL. The indicated air speed chosen for use in determining the pertinent structural loading conditions. This value will be incorporated in the aircraft certificate as a maximum operational limitation in level and climbing flight (see § 4a.726).

(d) Design gliding speed, Vg. The maximum indicated air speed to be used in determining the pertinent structural loading conditions (see §§ 4a.73 and 4a.726).

(e) Design stalling speed, Vs. The computed indicated air speed in unaccelerated flight based on the maximum lift coefficient of the wing and the design gross weight. The effects of slipstreams and nacelles shall be neglected in computing Vs. When high-lift devices are in operation the corresponding stalling speed will be denoted by Vst.

(f) Design flap speed, Vt. The indicated air speed at which maximum operation of high-lift devices is assumed (see §§ 4a.73 and 4a.726).

(g) Maximum vertical speed, Vm. A fictitious value of indicated air speed computed for unaccelerated flight in a vertical dive with zero propeller thrust.

(h) Design maneuvering speed, Vp. The indicated air speed at which maximum operation of the control surfaces is assumed (see § 4a.73).

[CAR, May 31, 1938, as amended by Amdt. 5, 4 F. R. 1171, Mar. 9, 1939]

§ 4a.41 Design gust velocity, U.

A specific gust velocity assumed to act normal to the flight path. (See § 48.76.)

§ 4a.42 Dynamic pressure, q.

The kinetic energy of a unit volume of air.

9=2pVt (in terms of true air speed).

20.V (in terms of indicated air speed). =V2/391 pounds per square foot, when V is miles per hour indicated air speed. CROSS REFERENCE: For definition of ρι see

§ 48.39.

(a) Load factor or acceleration factor, n. The ratio of a load to the design weight. When the load in question represents the net external load acting on the airplane in a given direction, n represents the acceleration factor in that direction.

(b) Limit load. A load (or load factor, or pressure) which it is assumed or known may be safely experienced but will not be exceeded in operation.

(c) Factor of safety, j. A factor by which the limit loads are multiplied for various design purposes.

(d) Ultimate factor of safety, ju. A specified factor of safety used in determining the maximum load which the airplane structure is required to support.

(e) Yield factor of safety, jy. A specified factor of safety used in connection with the prevention of permanent deformations.

(f) Ultimate load. A limit load multiplied by the specified ultimate factor (or factors) of safety. (See definitions in this section and § 4a.61.)

(g) Yield load. A limit load multiplied by the specified yield factor (or factors) of safety. (See definitions in this section and § 48.62.)

(h) Strength test. A static load test in which the ultimate loads are properly applied. (See §§ 4a.61 and 4a.230 (b).)

(i) Proof test. A static load test in which the yield loads are properly applied for a period of at least 1 minute. (See4a.62.)

(j) Balancing loads. Loads by which the airplane is placed in a state of equilibrium under the action of external forces resulting from specified loading conditions. The state of equilibrium thus obtained may be either real or fictitious. Balancing loads may represent air loads, inertia loads, or both. (See § 4a.116.)

§ 4a.44 Aerodynamic coefficients, CL, CM, CP, etc.

The coefficients hereinafter specified are those of the "absolute" (nondimensional) system adopted as standard in the United States. The subscripts N and C used hereinafter refer respectively to directions normal to and parallel with the basic chord of the airfoil section. Other subscripts have the usual significance. When applied to an entire wing or surface, the coefficients represent

average values and shall be properly correlated with local conditions (load distribution) as required in § 4a.99.

§ 4a.45 Standard atmosphere (standard air).

Standard atmosphere refers to that variation of air conditions with altitude which has been adopted as standard in the United States. (See any areonautics text book or handbook, or NACA Technical Report No. 218.)

§ 4a.46 Primary structure.

Those portions of the airplane the failure of which would seriously endanger the safety of the airplane. [Amdt. 5, 4 F. R. 1171, Mar. 9, 1939]

Subpart C-Structural Loading
Conditions

SOURCE: §§ 4a.61 to 4a.216 contained in Civil Air Regulations, May 31, 1938, as amended by Amdt. 75, 5 F. R. 3946, Oct. 8, 1940, except as otherwise noted.

GENERAL STRUCTURAL REQUIREMENTS § 4a.61

Strength.

The primary structure shall be capable of supporting without detrimental permanent deformations, for a period of alt least one minute, the yield loads (see § 4a.43(g)) determined by the loading conditions and yield factors of safety; specified in this part, the loads being properly distributed and applied. Where no yield factor of safety is specified a factor of 1.0 shall be assumed. In addition, temporary deformations which occur before the yield load is reached shall be of such a nature that their repeated occurrence will not weaken or damageN the primary structure.

The airworthiness rating of an airplane with respect to its strength under flight loads will be based on the air speeds and accelerations (from maneuvering or gusts) which can safely be developed in combination. For certain classes of airplanes the acceleration factors and gust velocities are arbitrarily specified hereinafter and shall be used for those classes. The air speeds which can safely be developed in combination with the specified acceleration factors and gusts shall be determined in accordance with the procedure specified in this part and shall serve as a basis for restricting the operation of the airplane in flight. (See § 4a.726.)

except that it need not be greater than either VL+100 miles per hour or 1.5 VL, whichever is lower. K, is specified on Figure 4a-1. Vm is defined in § 4a.40 (g). A special ruling may be obtained from the Administrator if the design gliding speed thus determined is greater than 1.33 VL and appears to be unnecessarily high for the type of airplane involved.

(c) V, shall not be less than 2Vst. Vst is defined in § 4a.40 (e).

(d) Vp shall not be less than

Vst+Kp (VL-Vsf),

except that it need not be greater than VL. Kp is specified on Figure 4a-2.

(e) (See §§ 4a.120, 4a.123, and 4a.125 for exceptions for multiengine airplanes.)

[Amdt. 5, 4 F. R. 1171, Mar. 9, 1939, as amended by Amdt. 75, 5 F. R. 3946, Oct. 8, 1940]

The flight load factors specified in §§ 4a.75-4a.99 shall represent wing load factors. The net load factor, or acceleration factor, shall be obtained by proper consideration of balancing loads acting on the airplane in the specific flight conditions.

§ 4a.75 Maneuvering load factors.

The limit maneuvering load factors specified in this part (see Fig. 4a-3) are derived largely from experience with conventional types of airplanes and shall be considered as minimum values unless it can be proved, to the satisfaction of the Administrator, that the airplane embodies features of design which make it impossible to develop such values in flight, in which case lower values may be used subject to the approval of the Administrator.

§ 4a.76 Gust load factors.

The gust load factors shall be computed on the basis of a gust of the magnitude specified, acting normal to the flight path, and proper allowance shall be made for the effects of aspect ratio on the slope of the lift curve. The gust velocities specified shall be used only in conjunction with the gust formulas specified in Civil Aeronautics Manual 4.2121.

[Amdt. 48, 5 F.R. 1935, May 22, 1940] § 4a.77 Factors of safety.

The minimum factors of safety are specified for each loading condition.

CROSS REFERENCE: For multiplying factors of safety required in certain cases, §§ 4a.207-4a.216.

see