Boeing KB-29P Superfortress Specifications (1951)

Boeing KB-29P Superfortress Specifications (1951)

Boeing KB-29P Superfortress Specifications (1951)

Mission

The KB-29P aircraft’s primary purpose was to perform in-flight refueling of other planes using the flying boom method. It differed from the standard B-29 plane by eliminating all defensive armament and installing specialized in-flight refueling equipment.

A Boeing KB-29P Superfortress, originally B-29-45-BA S/N 44-83951, with its Telescopic Flying Boom extended.
A Boeing KB-29P Superfortress, originally B-29-45-BA S/N 44-83951, with its Telescopic Flying Boom extended. (U.S. Air Force photo)

Dimensions and Weights

Boeing KB-29P Superfortress Dimensions
DIMENSIONSImperial Metric
Wing
  • Span
  • 141.2 ft43 m
  • Incidence
  • Dihedral
  • 4°29'23"4°29'23"
  • Sweepback(LE)
  • 7°1'26"7°1'26"
  • Wing Area
  • 1720 ft2159.8 m2
  • Aspect Ratio
  • 11.511.5
  • Wing Section
  • Boeing 117Boeing 117
  • M.A.C.
  • 154.4147.1 m
    Length120.1 ft36.6 m
    Height27.8 ft8.5 m
    Tread28.5 ft8.7 m
    Prop. Grd Clearance1.3 ft0.4 m
    WEIGHTS
    Loading
  • Empty
  • 69,011 lbs (E)31.303 kg
  • Basic
  • 70,645 lbs (A)32.044 kg
  • Operating
  • 74,705 lbs33.886 kg
  • Design
  • 135,000 lbs61.235 kg
  • Combat (*)
  • 84,665 lbs38.403 kg
  • Max Take Off (1)
  • 138,500 lbs62.823 kg
  • Max Landing (2)
  • 135,000 lbs61.235 kg

    (E) Estimated
    (A) Actual
    (*) For basic mission
    (1) Limited by performance
    (2) Limited by gear strength

    Engines

    Attribute Value
    POWER PLANT
  • No, & Model
  • (4) R-3350-57 or-57A
  • Manufacturer
  • Curtiss - Wright Corp., Wright Aeronautical Corp. Division
  • Engine Spec
  • 95-28266-5
  • Turbo
  • (2) B-31
  • Turbo Manufacturer
  • General Electric Co.
  • Red, Gear Ratio
  • 0.35
    PROPELLER
  • Propeller Manufacturer
  • Curtiss - Wright Corp.
  • Blade Design No.
  • 1016-4C4-18
  • Propeller Type
  • CS, FF, Reverse,
  • No. Blades
  • 4
  • Propeller Diameter
  • 16' 8" (5.1 m)
    ENGINE RATINGS
  • Take Off
  • 2200bhp/2800rpm
  • Military
  • 2200bhp/2600rpm/2500ft
  • Normal
  • 2000bhp/2400rpm/4000ft

    Electronics

    EquipmentUS Designation
    VHF CommandAN/ARC-3
    CommandSCR-274N
    InterphoneAN/AIC-2
    LiaisonAN/ARC-8
    Radio CompassAN/ARN-7
    Marker BeaconRC-193A
    RadarAN/APQ-13A
    LoranAN/APN-9
    IFFSCR-695B
    Rendezvous RadarAN/APN-2B,AN/APN-68 and AN/APN-11

    Crew

    Boeing KB-29P Superfortress crew and sections

    The KB-29P had a new crew member in the form of a boom operator who was responsible for operating the boom and connecting it to a receiver aircraft receptacle. This crew member sat in the converted tail turret position of the B-29.

    Boeing KB-29P Superfortress Boom operator
    The KB-29P added a new crew member for operating the Telescopic Flying Boom (U.S. Air Force photo)

    The crew list for the KB-29P was:

    1. Pilot
    2. Co-pilot
    3. Navigator
    4. Flight Engineer – Pumping system operator
    5. Radio operator
    6. Radar operator
    7. Flying Boom operator

    Fuel

    Boeing KB-29P Superfortress fuel system
    (U.S. Air Force)

    The KB-29P included form-fitting bomb bay tanks, each of which was jettisonable. All fuel tanks in the KB-29P tanker were made up of nylon non-self-sealing cells. The aircraft had a maximum fuel capacity of 11,954 gallons, which was greater than that of the B-29 bomber, which was 9,363 gallons.

    Initially, all fuel tanks were serviced with Mil-F-5572 aviation gasoline, which was available in two grades – 100/130 or 115/145. However, when the KB-29Ps were later used to refuel jet aircraft, the fuel servicing strategy was changed. The four main wing tanks and the two bomb bay tanks were restricted to the use of aviation gasoline, while the wing center section tanks were serviced with JP-4 jet fuel.

    LocationNo. TanksGalLiters
    Wing, outbound *2280010.599
    Wing, inbound *2300011.356
    Wing, center114005300
    Bomb bay, forward*125739740
    Bomb bay, afterward*121818256
    Total11,95445.251

    (*) nylon non-self-sealing cells

    Refueling Equipment

    A maneuverable telescoping boom with an articulated nozzle is attached to the bottom of the fuselage near the tail, serving as a connection and medium for fuel transfer between the tanker and receiver aircraft. The boom operator’s compartment (formerly the tail gunner’s compartment) houses hydraulic and aerodynamic controls for the boom.

    The fuel system comprises a manifold system for normal operations and a high-capacity pump system for refueling. With the exception of the hydraulically-operated brakes and boom, all equipment is operated electrically.

    The list of refueling equipment is the following:

    • Telescopic Flying Boom
    • Articulated Boom Nozzle
    • Ruddevators for aerodynamic control
    • Signal Amplifier
    • Radar equipment necessary for rendezvous with receiver:
      • AN/APN-2B
      • AN/APN-68
      • AN/APN-11
    Boeing KB-29P Superfortress Telescopic Flying Boom with Ruddevators
    Telescopic Flying Boom with Ruddevators (U.S. Air Force photo)

    Refueling Operation process:

    A KB-29P conducting a refueling operation with an RB-45C aircraft belonging to the 91st Strategic Reconnaissance Wing.
    A KB-29P conducting a refueling operation with an RB-45C aircraft belonging to the 91st Strategic Reconnaissance Wing. (U.S. Air Force photo)

    The KB-29P’s refueling operations were carried out with precision, requiring coordinated crew activities and careful formation flying.

    1. The KB-29P aircraft would assume a cruising altitude, extending the boom, and positioning the receiver aircraft below and behind the tanker.
    2. The boom operator would then guide the boom into the receptacle via ruddevator flight surfaces, which the boom operator manipulates using a conventional control stick. Contact is detected by a signal amplifier that controls equipment based on aircraft positions, rate of position change, and refueling line fuel pressure.
    3. Then, the flight engineer and boom operator would work together to transfer fuel into the receiver aircraft. The tanker is equipped to supply fuel to the receiver plane at a selectively controlled rate, up to 600 gallons per minute.
    4. During the fuel transfer, the receiver pilot would use the indicator lights, which displayed RIGHT, LEFT, UP, DOWN, FORWARD, and AFT, to make minor attitude adjustments and maintain position. As the weights of the two aircraft changed, and the center of gravity shifted, these adjustments became necessary.
    5. If any predetermined limits are exceeded, an involuntary disconnect is automatically triggered. A voluntary disconnect may also occur, initiated either by the boom operator or receiver pilot, resulting in a fuel shut-off and boom disconnect.
    6. Once refueling was complete, the receiver aircraft would drop off the boom. The boom operator would purge the refueling manifold with nitrogen to prevent any trapped fuel from causing an explosion.
    Boeing KB-29P Superfortress Telescopic Flying Boom operations details
    U.S. Air Force via Alwyn T. Lloyd

    Performance

    The basic performance of the KB-29P was the following:

    Combat radius

    1000 nm

    with 35,000 lb of transfer fuel at 216 knots avg. in 16.90 hours

    Combat range

    1594 nm

    with 35,000 lb of transfer fuel at 204 knots avg. in 9 hours

    Combat speed

    288 kn

    at 10,000 ft alt, max power

    Maximum speed

    349 kn


    at 30,000 ft alt, max power

    Climb

    500/2135

    fpm sea level, take-off weight normal power
    /fpm sea level, combat weight max power

    Ceiling

    23,500/
    39,500 ft

    100 fpm, take-off weight, normal power
    /500 fpm, combat weight max power

    Loading and Performance – Typical mission

    ConditionsBasic MissionHigh Alt RefuelFerry range
    TAKE-OFF WEIGHT138,500 lbs62.823 kg138,500 lbs62.823 kg138,500 lbs62.823 kg
  • Fuel at 6. 0 lb/gal (grade 100/130)
  • 28,795 lbs13.061 kg35,271 lbs15.999 kg63,795 lbs28.937 kg
  • Military load (transfer fuel)
  • 35,000 lbs15.876 kg28,524 lbs12.938 kgNone
  • Wing loading
  • 80.5 lb/sq ft393 kg/m280.5 lb/sq ft393 kg/m280.5 lb/sq ft393 kg/m2
  • Stall speed (power off, landing configuration)
  • 103 kn191 km/h103 kn191 km/h103 kn191 km/h
  • Take-off ground run at SL (1)
  • 5,075 ft1.547 m5,075 ft1.547 m5,075 ft1.547 m
  • Take-off to clear 50 ft (1)
  • 7,570 ft2.307 m7,570 ft2.307 m7,570 ft2.307 m
  • Rate of climb at SL (3)
  • 500 fpm152,4 m/min500 fpm152,4 m/min fpm152,4 m/min
  • Time: SL to 10,000 ft (3)
  • 23. 8 min23. 8 min23. 8 min
  • Time: SL to 20, 000 ft (3)
  • 61.8 min61.8 min61. 8 min
  • Service Ceiling (100 fpm) (3)
  • 23,500 ft7.163 m23,500 ft7.163 m23,500 ft7.163 m
  • Service Ceiling (one engine out)
  • 19,000 ft5.791 m19,000 ft5.791 m19,000 ft5.791 m
    COMBAT RANGE (4)1594 n.mi.2952 km1957 n.mi.3624 km/h4987 n.mi.9236 km/h
  • Average speed
  • 204 kn378 km/h204 kn378 km/h192 kn356 km/h
  • Initial cruising altitude
  • 10,000 ft3.048 m10,000 ft3.048 m10,000 ft3.048 m
  • Final cruising altitude
  • 10,000 ft3.048 m25,000 ft7.620 m10,000 ft3.048 m
  • Total mission time
  • 9.00 hrs10.74 hrs26.13 hrs
    COMBAT RADIUS (4)1000 n.mi.1852 km1154 n.mi2137 km
  • Average speed
  • 190 kn352 km/h211 kn391 km/h
  • Initial cruising altitude
  • 10,000 ft3.048 m10,000 ft3.048 m
  • Refueling altitude
  • 10,000 ft3.048 m25,000 ft7.620 m
  • Refuel speed (6)
  • 248 kn459 km/h311 kn576 km/h
  • Final cruising altitude
  • 10,000 ft3.048 m25,000 ft7.620 m
  • Total mission time
  • 11.71 hrs12.08 hrs
    COMBAT WEIGHT (5)84,665 lbs38.403 kg86,120 lbs39.063 kg81,085 lbs36.780 kg
  • Combat altitude
  • 10,000 ft3.048 m25,0007.620 m10,000 ft3.048 m
  • Combat speed (2)
  • 288 kn533 km/h332 kn615 km/h290 kn537 km/h
  • Combat climb (2)
  • 2,025 fpm617.2 m/min1,735 fpm529 m/min2,160 fpm658.3 m/min
  • Combat ceiling (500 fpm) (2)
  • 39,500 ft12.040 m39,200 ft11.948 m40,450 ft12.329 m
  • Service ceiling (100 fpm) (3)
  • 42,900 ft13.076 m42,500 ft12.954 m43,800 ft13.350 m
  • Service ceiling (one engine out) (3)
  • 38,800 ft11.826 m38,450 ft11.720 m39,700 ft12.101 m
  • Max rate of climb at SL (2)
  • 2,135 fpm650,7 m/min2,080 fpm634 m/min2,275 fpm693,4 m/min
  • Max speed at 30,000 ft (2)
  • 349 kn646 km/h348 kn644 km/h350 kn648 km/h
    LANDING WEIGHT (5)76,145 lbs34.539 kg76,469 lbs34.686 kg81,085 lbs36.780 kg
  • Ground roll at SL
  • 2,060 ft628 m2,075 ft1.547 m2,175 ft663 m
  • Total from 50 ft
  • 2,750 ft838 m2,760 ft841 m2,890 ft881 m

    (1)Take-off power
    (2) Max power
    (3) Normal power
    (4) Detailed descriptions of RADIUS and RANGE missions are given on page 6.
    (5) For Radius Mission if the radius is shown
    (6) At normal rated power but not exceeding 250 MPH (EAS) as per T. O. AN 01-20EJAB-1 NOTES 1

    Further reading

    Bibliography

    • B-29 Superfortress in detail & scale, Part 2: Derivatives by Alwyn T. Lloyd
    • KB-29P Superfortress SAC 8-MAR-1951, Air Materiel Command, U.S. Air Force

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    Javier Guerrero
    Javier Guerrero
    Javier is the editor @ Nuclear Companion and loves to investigate and write about the cold war.

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