B-17 Ball Turret Lecture Notes

Introduction

• Topic: B-17 Ball Turret (Sperry Ball Turret)
• Purpose: Overview of the A-2 variant mounted on B-17F aircraft
• Presenter: David Webb, Blue Paw Print

Design and Functionality

• Structure:
  • Spherical gun emplacement mounted underneath B-17
  • Known for claustrophobic design and vulnerability
  • Designed for defensive fire against fighters from below
  • A-2 Variant Specs:
    • Diameter: 44 inches
    • Weight: 850 pounds

Parts and Assembly

• Materials:

  • Plexiglass domes for aerodynamic properties
  • Steel center assembly with viewing and mounting features
  • Aluminum entry hatch assembly, armor-plated steel bottom

• Turret Mechanism:

  • 46.5-inch hole in the fuselage for turret mounting
  • Trunnion ring allows turret rotation
  • Harness provides structural rigidity and electrical conduit

• Operational Safety:

  • Gunner must not be inside during takeoff/landing
  • Guns must be elevated and locked upon landing

Gunner's Operation

• Entry into Turret:

  • Gunner enters between 9,000 and 10,000 feet altitude
  • Unlock turret and position for access
  • Fetal position inside turret with feet in footrests

• Equipment:

  • Turn on turret power; engage gun sight
  • Oxygen supply and heated suit connection
  • Manual Control:
    • Handles for turret movement with speed based on force applied
    • Can rotate 360 degrees in 8 seconds
    • Elevate/depress at a 90-degree range

Combat Readiness

• Ammunition and Fire Control:

  • Two M2 .50 caliber machine guns, 750 RPM rate
  • Selector switches for gun operation
  • Ammunition Storage:
    • Two bins, 445 rounds for the right gun, 571 for the left
    • Turret has an indicator for orientation

• Sighting and Targeting:

  • Sperry K-4 Sight:
    • Automatic computing gun sight
    • Calculates firing solution based on various parameters
    • Gunner operates using pedal to zoom and buttons to fire

Gunner Safety and Survival

• Protection Measures:
  • Armor plate for protection against calibers up to .30
  • Plexiglass windows for visibility; main sight with increased resistance
  • Notable that ball turret gunners had lowest crew injury rates

Exit Protocol

• Returning to Base:

  • Clear guns of ammunition
  • Rotate turret for safe exit
  • Manual crank for emergency operation

• Jettisoning Turret:

  • Can be dropped in emergencies by removing nuts and hooks
  • Takes approximately 20 minutes

Production and Technological Advances

• Ball Turret Production:

  • Costs ~$250,000 today ($14,300 in 1944)
  • 25% of cost for Sperry K-4 sight

• Evolution:

  • Decline in use post-war due to remote-controlled technology
  • Challenges from jet fighters, electronic warfare, and missiles

Conclusion

• Learning Resources:
  • Brilliant interactive learning platform recommended for mastering complex topics
  • Offers free trial and discount for subscriptions

Final Notes

• Feedback encouraged for continuous improvement
• Support available via Patreon

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Key Takeaways

• Understanding the design, operation, and historical significance of the B-17 ball turret.
• Recognizing the technological advancements and safety measures involved with the turret.