shall be marked for the benefit of passengers and crew.

§ 3.712 De-icers.

When pneumatic de-icers are installed, the installation shall be in accordance with approved data. Positive means shall be provided for the deflation of the pneumatic boots.

§ 3.713 Flare requirements.

When parachute flares are required, they shall be of an approved type. § 3.714 Flare installation.

Parachute flares shall be releasable from the pilot compartment and so installed that danger of accidental discharge is reduced to a minimum. The installation shall be demonstrated in flight to eject flares satisfactorily, except in those cases where inspection indicates a ground test will be adequate. If the flares are ejected so that recoil loads are involved, structural provisions for such loads shall be made.

§ 3.715 Safety belts.

Safety belts shall be of an approved type. In no case shall the rated strength of the safety belt be less than that corresponding with the ultimate load factors specified in § 3.386 (a), taking due account of the dimensional characteristics of the safety belt installation for the specific seat or berth arrangement. Safety belts shall be attached so that no part of the anchorage will fail at a load lower than that corresponding with the ultimate load factors equal to those specified in § 3.386(a) multiplied by a factor of 1.33. In the case of safety belts for berths, the forward load factor need not be applied.

EMERGENCY FLOTATION AND SIGNALING
EQUIPMENT

§ 3.716 Rafts and life preservers.

Rafts and life preservers shall be of an approved type.

§ 3.716-1 Life rafts and life preservers (FAA rules which apply to § 3.716). (a) The minimum safety requirements for life preservers and life rafts which are intended for use in certificated civil aircraft engaged in over-water operations have been established by the Administrator in the following Technical Standard Orders:

(1) No. TSO-C12, "Life Rafts," effective August 1, 1948 (§ 514.12 of this title).

When such emergency equipment is required, it shall be so installed as to be readily available to the crew and passengers. Rafts released automatically or by the pilot shall be attached to the airplane by means of a line to keep them adjacent to the airplane. The strength of the line shall be such that it will break before submerging the empty raft. § 3.718 Signaling device.

Signaling devices, when required by other parts of the regulations of this subchapter, shall be accessible, function satisfactorily, and be free from any hazard in their operation.

RADIO EQUIPMENT; INSTALLATION

Radio equipment and installations in the airplane shall be free from hazards in themselves, in their method of operation, and in their effects on other components of the airplane.

§ 3.721-1 Radio equipment installation (FAA interpretations which apply to § 3.721).

Engineering flight tests are not required for equipment installations unless a particular installation could conceivably interfere with flight operation of airplane or change the airplane configuration SO that performance or flight characteristics became adversely affected.

[Supp. 10, 16 F. R. 3292, Apr. 14, 1951]

§ 3.721-2 Radio equipment installations (FAA policies which apply to § 3.721).

(a) Wiring. Radio installations should be wired to minimize the possibility of fire or smoke hazards or the cause of unsatisfactory operation of the radio equipment.

(1) The radio installation should be connected to the airplane electrical system at a terminal strip or by a plug and receptacle connection.

(i) If a terminal strip is used, it should be designed or mounted so that loose metallic objects cannot fall across the terminal posts. Posts should be No. 6 or larger to permit proper tightening of the nuts, thus providing maximum cur

rrent-carrying capacity without a danger E of shearing the studs.

(ii) If a plug and receptacle type of I connection is used, the soldered connections of the wire to the plug and receptacle inserts should be individually insulated from each other and from other metallic parts of the plug and receptacle.

(2) Junction boxes should be used for enclosure of terminal strips. The boxes should be made of either fire-resistant or nonabsorbent, plastic material. They should be of sufficiently rigid construction to prevent “oil-canning" of the box sides thus avoiding the possibility of the sides causing internal shorts. They should be designed and installed to permit easy access to the enclosed terminals and to allow any loose metallic parts to Ffall away from the terminals. Sufficient space should be provided in the junction box so that it will not be necessary to bend the wires sharply as they leave the terminal strip. The terminal should be mounted within the box rather than on the inside of the box cover.

strip

(3) Interconnecting wires and cables · between various pieces of radio equipment should be supported by insulated clamps so that they do not rub against the airplane or each other under vibration conditions encountered in flight.

(b) Location of radio equipment. The equipment, controls, and indicators should be located where they can be satisfactorily operated and read respectively from the appropriate crew member station. The equipment should be so located that there is sufficient air circulation to avoid overheating of the equipment. Also, clearance should be provided between high temperature areas of the equipment and readily flammable parts of the airplane.

(c) Mounting of radio equipment. The equipment should be attached to the (airplane with self-locking devices to prevent loosening in service. Mechanical I remote control devices should have the control cable so routed and so supported as to prevent kinking, binding or abrasion. Items mounted on shock mounts should have sufficient clearance for normal vibration and swaying of the equipment without hitting adjacent equipment or parts of the airplane. Electrical and mechanical cables to shock mounted equipment should be routed and supported so that they will not be unduly

stressed by motion of the equipment. In order that the occupants will not be endangered by moving equipment during minor crash landings, the equipment mounting and rack should be capable of withstanding ultimate accelerations of 9.0g in the forward direction and 1.5g in a sideward direction.

(d) Bonding. Radio equipment should be bonded to the airplane in order to provide a low resistance ground circuit and to minimize radio interference from static electrical charges. Nonconducting finishes, such as paint and anodizing films should be carefully removed from the attachment surface under the bonding terminal. Bonding jumpers should be as short as practicable and be installed in such manner that the resistance of each connection does not exceed 0.003 ohm. Where a jumper is for radio-noise prevention only and not for current-carrying purposes, a resistance of .01 ohm is satisfactory. Aluminum alloy or tinned or cadmium plated copper jumpers should be used for bonding aluminum alloy parts and copper, brass or bronze jumpers should be used to bond steel parts.

2

and reception of communications provided such antenna is a satisfactory compromise for the frequencies to be used. In a single antenna installation of this type, the antenna should be connected to the receiver and be switched automatically to the transmitter when the microphone "push-to-talk" switch is actuated.

(1) Fixed and trailing wire antenna installations should be tailored to fit the particular type of aircraft. Other types of antennas are much more compact and may be installed as complete units on various types of aircraft.

(2) Masts used to support a fixed-wire antenna should be as long as practicable to separate the antenna from the fuselage and/or wings in order to provide an effective antenna. Masts should be firmly attached to the airplane structure. If an antenna is attached at the trailing edge of wings and leading edge of horizontal stabilizers, the attachment should be made to lugs firmly fixed to the structure. The lugs should be welded, riveted, clamped, or bolted, whichever method is most suitable, to the structure.

(g) Range receiver antennas (200 to 400 kc). A “T” or “V” type antenna should be used and mounted on the top or bottom of the airplane (see figure 1) with an approximate clearance of one foot from the fuselage and wings. The main leg of the "T" and each leg of the “V” antenna should be a minimum of 6 feet long.'

(h) Direction finding antennas (100 to 1750 kc). Manual or automatic loop type antennas should be used with direction finder receivers. The loops are designed for use with a particular receiver.

be radiated. In general, the higher the frequency to be transmitted, the shorter the antenna necessary. Receiver antenna design and installation is controlled primarily by the degree of directivity necessary for the particular communication or navigation equipment.

Excessively long antennas are unsatisfactory because they are more directive in reception than relatively short ones. A trailing wire type of antenna will not prove suitable when used with a range receiver because it is highly directive; may cause a loss of distinct "cone of silence"; and changes in the airplane's direction, which may occur often in range flying, cause the antenna to "whip," resulting in breakage and loss of reception. The whipping action may also cause the course signals to shift continuously.

Connecting wires between the loops an receivers are also designed for the spe cific equipment. Accordingly, only com ponents meeting the specification cha acteristics of the receiver manufacture should be used.

(1) Loops are usually enclosed in streamlined housing for external moun ing on an airplane. However, loops ma be installed internally in the airplan when proper attention is given to avoid ing interference from metallic structu and skin of the airplane.

(2) The outstanding characteristic a loop antenna is its directional sens tivity which makes it useful as an a curate navigational aid. Various thin can reduce this accuracy and should avoided. Metallic base paints should n be used on the housing. Location of t manual loop near an engine which h poor ignition shielding should be avoid since this location makes it difficult detect the "null." Loops should not located in positions where extensive m tallic airplane structure is between the and the ground facilities. After insta lation, a loop should be compensated"

5 Compensation of a loop for such error ! quires technical knowledge of the equipme and its operational use and should be a complished by a qualified technician.

correct for any azimuth error due to its location with respect to any metal structure of the airplane.

(i) HF transmitting antenna—fixed. (1) Two basic types of fixed antennas are used. One of these, the Hertz type, is tuned to its resonant frequency or a higher harmonically related frequency by being designed to a specific length. The lowest frequency at which this type antenna will be resonant is its fundamental frequency. At this frequency the antenna is approximately 2 wave length. This length may be determined by the formula:

1⁄2 wave length (in feet) =

=

300,000,000 X 3.28 2xf

in which 300,000,000 is the velocity of the propagation of radio waves in meters per second; 3.28 is the conversion factor from meters to feet; f is the frequency in cycles per second.

(2) The other basic type of antenna is the Marconi. This type is readily adaptable for use on different frequencies and has one end grounded through the transmitter to the metallic aircraft structure. Thus, the aircraft acts as a part of the antenna and it is possible to use only 14 wave length in the antenna proper. This length may be computed by the formula: 300,000,000 X 3.28 4Xf

1/4 wave length (in feet) =

operating in the 118 to 136 mc band. The proper length in inches should be 11,218 determined from the formula 4Xf(mc) (For 125 mc the length [4 wave length] would be approximately 22.5 inches.)

(2) When it is necessary to cover a broader frequency range than can be covered by the "whip" antenna, a blade type should be used, because it is resonant over a much broader frequency range. However, a broadband antenna is not as efficient as a small diameter "whip" antenna and, accordingly, should not be used with relatively low output transmitters (under 5 watts).

(3) Antennas of both these types should be located so that there is a minimum of structure between them and the ground radio stations. Thus, the location will usually be a compromise. The antennas may be mounted on the top or bottom of the fuselage or on the cowl forward of the cockpit.

be used between magnetos and spark plugs. Shielded type spark plugs should be used and a shielded metal cover for the magneto, if it is not of a shielded type, should be used. All connections in the shielding system should be tight metal-to-metal contact.

(2) If it is not feasible to shield the engine ignition system, the engine ignition noise should be suppressed by replacing the spark plugs with resistor spark plugs of a type approved for the engine.

(1) Marker receiving antenna. The marker receiver operates at a frequency of 75 mc. In order to keep to a minimum the number of antennas on an airplane, the marker receiver may utilize the same antenna as the range receiver. However, both receivers should include provisions to permit simultaneous operation without interference. A "whip" or other vertical type of antenna should not be used for marker reception since the ground facility transmits from a horizontally polarized antenna.

(m) Glide slope receiving antenna. The glide slope receiver of the instrument landing system (ILS) utilizes a small, simple dipole type antenna which should be mounted at right angles to the longitudinal axis of the airplane and near the forward part of the airplane. Several types of localizer and glide slope antennas are shown in figure 5.

(n) Distance measuring antennas. Antennas for Vortac distance measuring elements or civil DME should be mounted at an unobstructed location on the underside of the fuselage near the trailing edge of the wing, preferably at the lowest point on the aircraft when in level flight. (See figure 6.) During flight, the antenna should be as nearly vertical as possible. It should be mounted as far as possible from other antennas and at least 36 inches away from other obstructions. If separate antennas are used for transmission and reception, the antennas should be mounted on a line perpendicular to the longitudinal axis of the aircraft with a minimum spacing of 2 feet between antennas. Since transmissior lines losses are relatively high at these frequencies, the antenna connecting cables should be kept as short as possible (10 feet maximum unless special low los cable is used).

[Supp. 25, 22 F. R. 135 Jan. 5, 1957; 22 F. R 497, Jan. 25, 1957]