Four rows of seven cylinders each, staggered to manage cooling, made the Wasp Major the most complex piston engine to reach production. The R-4360-35 variant represented the definitive bomber-class powerplant of the late piston era, arriving as turboprops and jets waited in the wings.
R-4360-35 Engineering Overview
The primary subject of this technical guide focuses on the Pratt & Whitney R-4360-35 Wasp Major engine, engineered specifically for 28-Cylinder, 4-Row Radial, Air-Cooled applications. Below is an essential digest of this powertrain configuration.
• 28 cylinders in four staggered rows
• 71.5L displacement
• 2,800 hp at 2,700 rpm
• Powered B-36 and B-50
Wasp Major R-4360-35 Specification Table
71.5 liters of displacement from 28 cylinders arranged in four staggered rows; power rated at 2,088 kW (2,800 hp) at 2,700 rpm; dry weight 1,636 kg.
The staggering of cylinder rows solved the fundamental cooling problem of stacking four radial banks: each row sits slightly offset from the one ahead, allowing cooling air to reach every cylinder. The trade-off was immense mechanical complexity, with 28 cylinders, four rows of induction plumbing, and a crankshaft that had to handle power pulses from every direction. The R-4360-35 powered the Convair B-36 and Boeing B-50, among others.
| Configuration | 28-cylinder, 4-row radial |
|---|---|
| Cooling | Air-cooled |
| Bore | 146 mm (5.8 in) |
| Stroke | 152 mm (6.0 in) |
| Displacement | 71.5 L (4,360 cu in) |
| Power | 2,800 hp @ 2,700 rpm |
| Weight | 1,636 kg (3,600 lb) |
| Fuel | Aviation gasoline |
Airframes Powered by the R-4360-35
This engine model is deployed across various operational frameworks. Here is a breakdown of the typical machine or vehicle applications using this unit:
Convair B-36 Peacemaker, Boeing B-50 Superfortress, Boeing C-97 Stratofreighter, Douglas C-124 Globemaster II
Pros & Advantages
Highest production piston power of its era; four-row layout maximized displacement within bomber nacelle limits; proven in long-range service.
Cons & Disadvantages
Extreme maintenance complexity; lengthy warm-up and cool-down cycles; poor power-to-weight ratio compared to turboprops.
Frequently Asked Questions (FAQs)
Q1: Why did the R-4360 have four rows of cylinders?
A1: Four rows allowed Pratt & Whitney to achieve 71.5 liters of displacement within a diameter practical for bomber engine nacelles. Staggering each row ensured adequate cooling airflow.
Q2: How much horsepower did the R-4360-35 produce?
A2: The -35 variant was rated at 2,088 kW (2,800 hp) at 2,700 rpm. Later Wasp Major variants reached higher ratings, with some approaching 3,500 hp.
Q3: What was the primary aircraft for the R-4360-35?
A3: The Convair B-36 Peacemaker used six R-4360 engines as its primary powerplant, making it the most prominent application of this variant.
The engine weighed approximately 1,636 kg (3,600 lb) dry, making it one of the heaviest piston aero engines ever produced.