World War Photos

B-18A 37-503 #14 28 July 1939

The B-18 Bolo’s main landing gear was a crucial component of its operation, designed with hydraulic systems for reliability and ease of use. Here’s an overview of its features and how it functioned:

Main Landing Gear Design:

• Hydraulic System:

  • The main landing gear consisted of two independent hydraulic units, one for each wheel, mounted under the engine nacelles.
  • The gear was designed to retract into the nacelles, leaving only the bottom of the tire slightly exposed when fully retracted.

• Shock Absorbers:

  • The landing gear used oleo-pneumatic shock absorbers with a booster pump to maintain pressure, ensuring a smooth landing and takeoff by absorbing the shock.

• Wheels and Tires:

  • Bendix wheels were used, which were interchangeable between the left and right sides.
  • The wheels mounted 45×17-16, 10-ply tires, suitable for the aircraft’s weight and landing conditions.

Brakes:

• Brake System:

  • Bendix dual hydraulic 14×3 brakes were installed on each wheel. These brakes operated independently, controlled by toe pressure on the rudder pedals.
  • Hydraulic pressure, with a minimum of 500 psi, was transmitted through a power brake control valve, ensuring effective braking for each wheel independently.

• Parking Brake:

  • A plunger-type parking lock was located on the upper left corner of the control pedestal base. To engage the parking brake, the plunger was pulled, and the rudder pedals were depressed until the plunger locked into place. Releasing the brake involved depressing the pedals to unlock the spring lock.

Wheel Stop:

• Automatic Braking:
  • A wheel stop was attached to each landing gear upper truss. Once the landing gear retracted into the nacelle, this wheel stop engaged with the tire, applying sufficient braking to stop the rotating tire, which was necessary due to slipstream pressure acting on the exposed portion of the tire.

Operation of the Main Landing Gear:

• Retraction:

  • The landing gear retraction was initiated by setting the latch to the “LATCH RAISED” position. A red warning light illuminated to indicate that the latch was raised.
  • The landing gear control valve was then moved to the “UP” position, and hydraulic pressure retracted the wheels into the nacelles.
  • After retraction, a manual hand pump was used to ensure that the axles were securely against rubber bumpers inside the nacelle. This procedure was necessary to check and secure the gear’s position during flight.

• Extension:

  • To lower the landing gear, the control valve was pushed to the “DOWN” position, which automatically set the safety latch to the “SPRING LOADED” position, allowing the wheels to extend.
  • Once the gear was fully extended and latched, a green light illuminated to confirm the “DOWN and LOCKED” status. The latch control handle was then moved down to ensure it was in the “POSITIVE LOCKED” position.

Landing Gear Indicating System:

• Signal Lights and Horn:
  • The system included a Klaxon Type K-16 horn and signal lights to indicate the status of the landing gear.
  • The green signal light indicated that the gear was “DOWN and LOCKED,” while the red light indicated that it was not fully down or locked.
  • If the throttles were closed and the gear was not fully down and locked, the horn would sound as a warning.

Tail Wheel:

• Design and Control:
  • The tail wheel was fully swiveling and was designed to remain in the trailing position during takeoff and landing.
  • A latch controlled by a lever in the pilot’s compartment could lock the tail wheel in the trailing position.
  • The tail wheel assembly included an oleo-pneumatic shock absorber and a Hayes Industries 9×6 wheel, fitted with a 22x9x6, 8-ply tire.