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Pt. 121, App. C
Appendix C to Part 121—C-46 Nontransport Category Airplanes

Cargo Operations

1. Required engines.
(a) Except as provided in paragraph (b) of this section, the engines specified in subparagraphs (1) or (2) of this section must be installed in C-46 nontransport category airplanes operated at gross weights exceeding 45,000 pounds:
(1) Pratt and Whitney R2800-51-M1 or R2800-75-M1 engines (engines converted from basic model R2800-51 or R2800-75 engines in accordance with FAA approved data) that—
(i) Conform to Engine Specification 5E-8;
(ii) Conform to the applicable portions of the operator's manual;
(iii) Comply with all the applicable airworthiness directives; and
(iv) Are equipped with high capacity oil pump drive gears in accordance with FAA approved data.
(2) Other engines found acceptable by the FAA Regional Flight Standards Division having type certification responsibility for the C-46 airplane.
(b) Upon application by an operator conducting cargo operations with nontransport category C-46 airplanes between points within the State of Alaska, the appropriate FAA Flight Standards District Office, Alaskan Region, may authorize the operation of such airplanes, between points within the State of Alaska; without compliance with paragraph (a) of this section if the operator shows that, in its area of operation, installation of the modified engines is not necessary to provide adequate cooling for single-engine operations. Such authorization and any conditions or limitations therefor is made a part of the Operations Specifications of the operator.
2. Minimum acceptable means of complying with the special airworthiness requirements. Unless otherwise authorized under § 121.213, the data set forth in sections 3 through 34 of this appendix, as correlated to the C-46 nontransport category airplane, is the minimum means of compliance with the special airworthiness requirements of §§ 121.215 through 121.281.
3. Susceptibility of material to fire. [Deleted as unnecessary]
4. Cabin interiors. C-46 crew compartments must meet all the requirements of § 121.215, and, as required in § 121.221, the door between the crew compartment and main cabin (cargo) compartment must be flame resistant.
5. Internal doors. Internal doors, including the crew to main cabin door, must meet all the requirements of § 121.217.
6. Ventilation. Standard C-46 crew compartments meet the ventilation requirements of § 121.219 if a means of ventilation for controlling the flow of air is available between the crew compartment and main cabin. The ventilation requirement may be met by use of a door between the crew compartment and main cabin. The door need not have louvers installed; however, if louvers are installed, they must be controllable.
7. Fire precautions. Compliance is required with all the provisions of § 121.221.
(a) In establishing compliance with this section, the C-46 main cabin is considered as a Class A compartment if—
(1) The operator utilizes a standard system of cargo loading and tiedown that allows easy access in flight to all cargo in such compartment, and, such system is included in the appropriate portion of the operator's manual; and
(2) A cargo barrier is installed in the forward end of the main cabin cargo compartment. The barrier must—
(i) Establish the most forward location beyond which cargo cannot be carried;
(ii) Protect the components and systems of the airplane that are essential to its safe operation from cargo damage; and
(iii) Permit easy access, in flight, to cargo in the main cabin cargo compartment.
The barrier may be a cargo net or a network of steel cables or other means acceptable to the Administrator which would provide equivalent protection to that of a cargo net. The barrier need not meet crash load requirements of FAR § 25.561; however, it must be attached to the cargo retention fittings and provide the degree of cargo retention that is required by the operators' standard system of cargo loading and tiedown.
(b) C-46 forward and aft baggage compartments must meet, as a minimum, Class B requirements of this section or be placarded in a manner to preclude their use as cargo or baggage compartments.
8. Proof of compliance. The demonstration of compliance required by § 121.223 is not required for C-46 airplanes in which—
(1) The main cabin conforms to Class A cargo compartment requirements of § 121.219; and
(2) Forward and aft baggage compartments conform to Class B requirements of § 121.221, or are placarded to preclude their use as cargo or baggage compartments.
9. Propeller deicing fluid. No change from the requirements of § 121.225. Isopropyl alcohol is a combustible fluid within the meaning of this section.
10. Pressure cross-feed arrangements, location of fuel tanks, and fuel system lines and fittings. C-46 fuel systems which conform to all applicable Curtiss design specifications and which comply with the FAA type certification requirements are in compliance with the provisions of §§ 121.227 through 121.231.
11. Fuel lines and fittings in designated fire zones. No change from the requirements of § 121.233.
12. Fuel valves. Compliance is required with all the provisions of § 121.235. Compliance can be established by showing that the fuel system conforms to all the applicable Curtiss design specifications, the FAA type certification requirements, and, in addition, has explosion-proof fuel booster pump electrical selector switches installed in lieu of the open contact type used originally.
13. Oil lines and fittings in designated fire zones. No change from the requirements of § 121.237.
14. Oil valves. C-46 oil shutoff valves must conform to the requirements of § 121.239. In addition, C-46 airplanes using Hamilton Standard propellers must provide, by use of stand pipes in the engine oil tanks or other approved means, a positive source of oil for feathering each propeller.
15. Oil system drains. The standard C-46 “Y” drains installed in the main oil inlet line for each engine meet the requirements of § 121.241.
16. Engine breather line. The standard C-46 engine breather line installation meets the requirements of § 121.243 if the lower breather lines actually extend to the trailing edge of the oil cooler air exit duct.
17. Firewalls and firewall construction. Compliance is required with all of the provisions of §§ 121.245 and 121.247. The following requirements must be met in showing compliance with these sections:
(a) Engine compartment. The engine firewalls of the C-46 airplane must—
(1) Conform to type design, and all applicable airworthiness directives;
(2) Be constructed of stainless steel or approved equivalent; and
(3) Have fireproof shields over the fairleads used for the engine control cables that pass through each firewall.
(b) Combustion heater compartment. C-46 airplanes must have a combustion heater fire extinguishing system which complies with AD-49-18-1 or an FAA approved equivalent.
18. Cowling. Standard C-46 engine cowling (cowling of aluminum construction employing stainless steel exhaust shrouds) which conforms to the type design and cowling configurations which conform to the C-46 transport category requirements meet the requirements of § 121.249.
19. Engine accessory section diaphragm. C-46 engine nacelles which conform to the C-46 transport category requirements meet the requirements of § 121.251. As provided for in that section, a means of equivalent protection which does not require provision of a diaphragm to isolate the engine power section and exhaust system from the engine accessory compartment is the designation of the entire engine compartment forward of and including the firewall as a designated fire zone, and the installation of adequate fire detection and fire extinguishing systems which meet the requirements of § 121.263 and § 121.273, respectively, in such zone.
20. Powerplant fire protection. C-46 engine compartments and combustion heater compartments are considered as designated fire zones within the meaning of § 121.253.
21. Flammable fluids
(a) Engine compartment. C-46 engine compartments which conform to the type design and which comply with all applicable airworthiness directives meet the requirements of § 121.255.
(b) Combustion heater compartment. C-46 combustion heater compartments which conform to type design and which meet all the requirements of AD-49-18-1 or an FAA approved equivalent meet the requirements of § 121.255.
22. Shutoff means
(a) Engine compartment. C-46 engine compartments which comply with AD-62-10-2 or FAA approved equivalent meet the requirements of § 121.257 applicable to engine compartments, if, in addition, a means satisfactory to the Administrator is provided to shut off the flow of hydraulic fluid to the cowl flap cylinder in each engine nacelle. The shutoff means must be located aft of the engine firewall. The operator's manual must include, in the emergency portion, adequate instructions for proper operation of the additional shutoff means to assure correct sequential positioning of engine cowl flaps under emergency conditions. In accordance with § 121.315, this positioning must also be incorporated in the emergency section of the pilot's checklist.
(b) Combustion heater compartment. C-46 heater compartments which comply with paragraph (5) of AD-49-18-1 or FAA approved equivalent meet the requirements of § 121.257 applicable to heater compartments if, in addition, a shutoff valve located above the main cabin floor level is installed in the alcohol supply line or lines between the alcohol supply tank and those alcohol pumps located under the main cabin floor. If all of the alcohol pumps are located above the main cabin floor, the alcohol shutoff valve need not be installed. In complying with paragraph (5) of AD-49-18-1, a fail-safe electric fuel shutoff valve may be used in lieu of the manually operated valve.
23. Lines and fittings—(a) Engine compartment. C-46 engine compartments which comply with all applicable airworthiness directives, including AD-62-10-2, by using FAA approved fire-resistant lines, hoses, and end fittings, and engine compartments which meet the C-46 transport category requirements, meet the requirements of § 121.259.
(b) Combustion heater compartments All lines, hoses, and end fittings, and couplings which carry fuel to the heaters and heater controls, must be of FAA approved fire-resistant construction.
24. Vent and drain lines—(a) Enginecompartment. C-46 engine compartments meet the requirements of § 121.261 if—
(1) The compartments conform to type design and comply with all applicable airworthiness directives or FAA approved equivalent; and
(2) Drain lines from supercharger case, engine-driven fuel pump, and engine-driven hydraulic pump reach into the scupper drain located in the lower cowling segment.
(b) Combustion heater compartment. C-46 heater compartments meet the requirements of § 121.261 if they conform to AD-49-18-1 or FAA approved equivalent.
25. Fire-extinguishing system.
(a) To meet the requirements of § 121.263, C-46 airplanes must have installed fire extinguishing systems to serve all designated fire zones. The fire-extinguishing systems, the quantity of extinguishing agent, and the rate of discharge shall be such as to provide a minimum of one adequate discharge for each designated fire zone. Compliance with this provision requires the installation of a separate fire extinguisher for each engine compartment. Insofar as the engine compartment is concerned, the system shall be capable of protecting the entire compartment against the various types of fires likely to occur in the compartment.
(b) Fire-extinguishing systems which conform to the C-46 transport category requirements meet the requirements set forth in paragraph (a). Furthermore, fire-extinguishing systems for combustion heater compartments which conform to the requirements of AD-49-18-1 or an FAA approved equivalent also meet the requirements in paragraph (a).
In addition, a fire-extinguishing system for C-46 airplanes meets the adequacy requirement of paragraph (a) if it provides the same or equivalent protection to that demonstrated by the CAA in tests conducted in 1941 and 1942, using a CW-20 type engine nacelle (without diaphragm). These tests were conducted at the Bureau of Standards facilities in Washington, DC, and copies of the test reports are available through the FAA Regional Engineering Offices. In this connection, the flow rates and distribution of extinguishing agent substantiated in American Airmotive Report No. 128-52-d, FAA approved February 9, 1953, provides protection equivalent to that demonstrated by the CAA in the CW-20 tests. In evaluating any C-46 fire-extinguishing system with respect to the aforementioned CW-20 tests, the Administration would require data in a narrative form, utilizing drawings or photographs to show at least the following:
Installation of containers; installation and routing of plumbing; type, number, and location of outlets or nozzles; type, total volume, and distribution of extinguishing agent; length of time required for discharging; means for thermal relief, including type and location of discharge indicators; means of discharging, e.g., mechanical cutterheads, electric cartridge, or other method; and whether a one- or two-shot system is used; and if the latter is used, means of cross-feeding or otherwise selecting distribution of extinguishing agent; and types of materials used in makeup of plumbing.
High rate discharge (HRD) systems using agents such as bromotrifluoromethane, dibrodifluoromethane and chlorobromomethane (CB), may also meet the requirements of paragraph (a).
26. Fire-extinguishing agents, Extinguishing agent container pressure relief, Extinguishing agent container compartment temperatures, and Fire-extinguishing system materials. No change from the requirements of §§ 121.265 through 121.271.
27. Fire-detector system. Compliance with the requirements of § 121.273 requires that C-46 fire detector systems conform to:
(a) AD-62-10-2 or FAA approved equivalent for engine compartments; and
(b) AD-49-18-1 or FAA approved equivalent for combustion heater compartments
28. Fire detectors. No change from the requirements of § 121.275.
29. Protection of other airplane components against fire. To meet the requirements of § 121.277, C-46 airplanes must—
(a) Conform to the type design and all applicable airworthiness directives; and
(b) Be modified or have operational procedures established to provide additional fire protection for the wheel well door aft of each engine compartment. Modifications may consist of improvements in sealing of the main landing gear wheel well doors. An operational procedure which is acceptable to the Agency is one requiring the landing gear control to be placed in the up position in case of in-flight engine fire. In accordance with § 121.315, such procedure must be set forth in the emergency portion of the operator's emergency checklist pertaining to in-flight engine fire.
30. Control of engine rotation. C-46 propeller feathering systems which conform to the type design and all applicable airworthiness directives meet the requirements of § 121.279.
31. Fuel system independence. C-46 fuel systems which conform to the type design and all applicable airworthiness directives meet the requirements of § 121.281.
32. Induction system ice prevention. The C-46 carburetor anti-icing system which conforms to the type design and all applicable airworthiness directives meets the requirements of § 121.283.
33. Carriage of cargo in passenger compartments. Section 121.285 is not applicable to nontransport category C-46 cargo airplanes.
34. Carriage of cargo in cargo compartments. A standard cargo loading and tiedown arrangement set forth in the operator's manual and found acceptable to the Administrator must be used in complying with § 121.287.
35. Performance data. Performance data on Curtiss model C-46 airplane certificated for maximum weight of 45,000 and 48,000 pounds for cargo-only operations.
1. The following performance limitation data, applicable to the Curtiss model C-46 airplane for cargo-only operation, must be used in determining compliance with §§ 121.199 through 121.205. These data are presented in the tables and figures of this appendix.

Table 1—Takeoff Limitations

(a) Curtiss C-46 certificated for maximum weight of 45,000 pounds.
(1) Effective length of runway required when effective length is determined in accordance with § 121.171 (distance to accelerate to 93 knots TIAS and stop, with zero wind and zero gradient). (Factor = 1.00)
Standard altitude in feet
Airplane weight in pounds
39,000
42,000
45,000 1
S.L
4,110
4,290
4,570
1,000
4,250
4,440
4,720
2,000
4,400
4,600
4,880
3,000
4,650
4,880
5,190
4,000
4,910
5,170
5,500
5,000
5,160
5,450
5,810
6,000
5,420
5,730
6,120
7,000
5,680
6,000
6,440
8,000
5,940
6,280
(1)
1 Ref. Fig. 1(a)(1) for weight and distance for altitudes above 7,000′.
(2) Actual length of runway required when effective length, considering obstacles, is not determined (distance to accelerate to 93 knots TIAS and stop, divided by the factor 0.85).
Standard altitude in feet
Airplane weight in pounds
39,000
42,000
45,000 1
S.L
4,830
5,050
5,370
1,000
5,000
5,230
5,550
2,000
5,170
5,410
5,740
3,000
5,470
5,740
6,100
4,000
5,770
6,080
6,470
5,000
6,070
6,410
6,830
6,000
6,380
6,740
7,200
7,000
6,680
7,070
7,570
8,000
6,990
7,410
(1)
1 Ref. Fig. 1(a)(2) for weight and distance for altitudes above 7,000′.
(b) Curtiss C-46 certificated for maximum weight 48,000 pounds.
(1) Effective length of runway required when effective length is determined in accordance with § 121.171 (distance to accelerate to 93 knots TIAS and stop, with zero wind and zero gradient). (Factor = 1.00)
Standard altitude in feet
Airplane weight in pounds
39,000
42,000
45,000
48,000 1
S.L
4,110
4,290
4,570
4,950
1,000
4,250
4,440
4,720
5,130
2,000
4,400
4,600
4,880
5,300
3,000
4,650
4,880
5,190
5,670
4,000
4,910
5,170
5,500
6,050
5,000
5,160
5,450
5,810
6,420
6,000
5,420
5,730
6,120
6,800
7,000
5,680
6,000
6,440
(1)
8,000
5,940
6,280
6,750
(1)
1 Ref. Fig. 1(b)(1) for weight and distance for altitudes above 6,000′.
(2) Actual length of runway required when effective length, considering obstacles, is not determined (distance to accelerate to 93 knots TIAS and stop, divided by the factor 0.85).
Standard altitude in feet
Airplane weight in pounds
39,000
42,000
45,000
48,000 1
S.L
4,830
5,050
5,370
5,830
1,000
5,000
5,230
5,550
6,030
2,000
5,170
5,410
5,740
6,230
3,000
5,470
5,740
6,100
6,670
4,000
5,770
6,080
6,470
7,120
5,000
6,070
6,410
6,830
7,560
6,000
6,380
6,740
7,200
8,010
7,000
6,680
7,070
7,570
(1)
8,000
6,990
7,410
7,940
(1)
1 Ref. Fig. 1(b)(2) for weight and distance for altitudes above 6,000′.

Table 2—En Route Limitations

(a) Curtiss model C-46 certificated for maximum weight of 45,000 pounds (based on a climb speed of 113 knots (TIAS)).
Weight (pounds)
Terrain clearance (feet) 1
Blower setting
45,000
6,450
Low.
44,000
7,000
  Do.
43,000
7,500
  Do.
42,200
8,000
High.
41,000
9,600
  Do.
40,000
11,000
  Do.
39,000
12,300
  Do.
1 Highest altitude of terrain over which airplanes may be operated in compliance with § 121.201.
Ref. Fig. 2(a).
(b) Curtiss model C-46 certificated for maximum weight of 48,000 pounds or with engine installation approved for 2,550 revolutions per minute (1,700 brake horsepower). Maximum continuous power in low blower (based on a climb speed of 113 knots (TIAS)).
Weight (pounds)
Terrain clearance (feet) 1
Blower setting
48,000
5,850
Low.
47,000
6,300
  Do.
46,000
6,700
  Do.
45,000
7,200
  Do.
44,500
7,450
  Do.
44,250
8,000
High.
44,000
8,550
  Do.
43,000
10,800
  Do.
42,000
12,500
  Do.
41,000
13,000
  Do.
1 Highest altitude of terrain over which airplanes may be operated in compliance with § 121.201.
Ref. Fig. 2(b).

Table 3—Landing Limitations

(a) Intended Destination.
Effective length of runway required for intended destination when effective length is determined in accordance with § 121.171 with zero wind and zero gradient.
(1) Curtiss model C-46 certificated for maximum weight of 45,000 pounds. (0.60 factor)
Standard altitude in feet
Airplane weight in pounds and approach speeds 1 in knots
V
50
V
50
V
50
V
50
40,000
42,000
44,000
45,000
S.L
4,320
86
4,500
88
4,700
90
4,800
91
1,000
4,440
86
4,620
88
4,830
90
4,930
91
2,000
4,550
86
4,750
88
4,960
90
5,050
91
3,000
4,670
86
4,880
88
5,090
90
5,190
91
4,000
4,800
86
5,000
88
5,220
90
5,320
91
5,000
4,920
86
5,140
88
5,360
90
5,460
91
6,000
5,040
86
5,270
88
5,550
90
5,600
91
7,000
5,170
86
5,410
88
5,650
90
5,750
91
8,000
5,310
86
5,550
88
5,800
90
5,900
91
1 Steady approach speed through 50-foot height TIAS denoted by symbol V50.
Ref. Fig. 3(a)(1).
(2) Curtiss model C-46 certificated for maximum weight of 48,000 pounds. 1 (0.60 factor.)
Standard altitude in feet
Airplane weight in pounds and approach speeds 2 in knots
V
50
V
50
V
50
V
50
42,000
44,000
46,000
43,000
S.L
3,370
80
3,490
82
3,620
84
3,740
86
1,000
3,460
80
3,580
82
3,710
84
3,830
86
2,000
3,540
80
3,670
82
3,800
84
3,920
86
3,000
3,630
80
3,760
82
3,890
84
4,020
86
4,000
3,720
80
3,850
82
3,980
84
4,110
86
5,000
3,800
80
3,940
82
4,080
84
4,220
86
6,000
3,890
80
4,040
82
4,180
84
4,320
86
7,000
3,980
80
4,140
82
4,280
84
4,440
86
8,000
4,080
80
4,240
82
4,390
84
4,550
86
1 For use with Curtiss model C-46 airplanes when approved for this weight.
2 Steady approach speed through 50 height knots TIAS denoted by symbol V503.
Ref. Fig. 3(a)(2).
(b) Alternate Airports.
Effective length of runway required when effective length is determined in accordance with § 121.171 with zero wind and zero gradient.
(1) Curtiss model C-46 certificated for maximum weight of 45,000 pounds. (0.70 factor.)
Standard altitude in feet
Airplane weight in pounds and approach speeds 1 in knots
V
50
V
50
V
50
V
50
40,000
42,000
44,000
45,000
S.L
3,700
86
3,860
88
4,030
90
4,110
91
1,000
3,800
86
3,960
88
4,140
90
4,220
91
2,000
3,900
86
4,070
88
4,250
90
4,340
91
3,000
4,000
86
4,180
88
4,360
90
4,450
91
4,000
4,110
86
4,290
88
4,470
90
4,560
91
5,000
4,210
86
4,400
88
4,590
90
4,680
91
6,000
4,330
86
4,510
88
4,710
90
4,800
91
7,000
4,430
86
4,630
88
4,840
90
4,930
91
8,000
4,550
86
4,750
88
4,970
90
5,060
91
1 Steady approach speed through 50 foot-height-knots TIAS denoted by symbol V50.
Ref. Fig. 3(b)(1).
(2) Curtiss model C-46 certificated for maximum weight of 48,000 pounds. 1 (0.70 factor.)
Standard altitude in feet
Airplane weight in pounds and approach speeds 2 in knots
V
50
V
50
V
50
V
50
42,000
44,000
46,000
48,000
S.L
2,890
80
3,000
82
3,110
84
3,220
86
1,000
2,960
80
3,070
82
3,180
84
3,280
86
2,000
3,040
80
3,150
82
3,260
84
3,360
86
3,000
3,110
80
3,220
82
3,340
84
3,440
86
4,000
3,180
80
3,300
82
3,410
84
3,520
86
5,000
3,260
80
3,380
82
3,500
84
3,610
86
6,000
3,330
80
3,460
82
3,580
84
3,700
86
7,000
3,420
80
3,540
82
3,670
84
3,800
86
8,000
3,500
80
3,630
82
3,760
84
3,900
86
1 For use with Curtiss model C-46 airplanes when approved for this weight.
2 Steady approach speed through 50 foot-height-knots TIAS denoted by symbol V50.
Ref. Fig. 3(b)(2).
(c) Actual length of runway required when effective length, considering obstacles, is not determined in accordance with § 121.171.
(1) Curtiss model C-46 certificated for maximum weight of 45,000 pounds. (0.55 factor.)
Standard altitude in feet
Airplane weight in pounds and approach speeds 1 in knots
V
50
V
50
V
50
V
50
40,000
42,000
44,000
45,000
S.L
4,710
86
4,910
88
5,130
90
5,230
91
1,000
4,840
86
5,050
88
5,270
90
5,370
91
2,000
4,960
86
5,180
88
5,410
90
5,510
91
3,000
5,090
86
5,320
88
5,550
90
5,660
91
4,000
5,230
86
5,460
88
5,700
90
5,810
91
5,000
5,360
86
5,600
88
5,850
90
5,960
91
6,000
5,500
86
5,740
88
6,000
90
6,110
91
7,000
5,640
86
5,900
88
6,170
90
6,280
91
8,000
5,790
86
6,050
88
6,340
90
6,450
91
1 Steady approach speed through 50 foot-height-knots TIAS denoted by symbol V50.
Ref. Fig. 3(c)(1).
(2) Curtiss C-46 certificated for maximum weight of 48,000 pounds. 1 (0.55 factor.)
Standard altitude in feet
Airplane weight in pounds and approach speeds 2 in knots
V
50
V
50
V
50
V
50
42,000
44,000
46,000
48,000
S.L
3,680
80
3,820
82
3,960
84
4,090
86
1,000
3,770
80
3,910
82
4,050
84
4,180
86
2,000
3,860
80
4,000
82
4,140
84
4,280
86
3,000
3,960
80
4,090
82
4,240
84
4,380
86
4,000
4,050
80
4,190
82
4,340
84
4,490
86
5,000
4,150
80
4,290
82
4,450
84
4,600
86
6,000
4,240
80
4,400
82
4,560
84
4,710
86
7,000
4,350
80
4,510
82
4,670
84
4,840
86
8,000
4,450
80
4,620
82
4,790
84
4,960
86
1 For use with Curtiss model C-46 airplanes when approved for this weight.
2 Steady approach speed through 50 foot-height-knots TIAS denoted by symbol V50.
Ref. Fig. 3(c)(2).
Graphic of Ref. Fig. 3(c)(2).
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[Doc. No. 4080, 30 FR 258, Jan. 3, 1965; 30 FR 481, Jan. 14, 1965, as amended by Amdt. 121-207, 54 FR 39293, Sept. 25, 1989]