Consolidated Coronado seaplane flew in relative obscurity

If Consolidated’s PBY Catalina flying boats and amphibians set the tone for U.S. Navy seaplanes before and during World War II, that company’s larger four-engine PB2Y Coronado flew in relative obscurity.

Budgetary math did not favor the big Coronado; the first six PB2Y-2 models ordered by the U.S. Navy in March 1939 cost as much as 18 twin-engine PBYs.

More than 200 PB2Y-3 variants were built. Some served as patrol bombers, others underwent modification to become long-range transports.

PB2Y-5s were adapted from PB2Y-3s, and had engines optimized for low altitude flight. As the PB2Y-5H, some Coronados could carry 25 litter patients.

The conversion of former bomber Coronados to transports followed the Navy’s wartime migration into heavy land-based patrol bombers like the Liberator and Privateer instead of the continued use of seaplanes as bombers.

Only one PB2Y survives. It is a Dash-5 model in the National Naval Aviation Museum at Pensacola, Florida.

This Coronado has flown with the stars. The Hughes Tool Co. bought it and registered it as NR69003 circa 1946. It was said to have been used by Howard Hughes for proficiency in advance of his one flight in the much larger Hughes Hercules “Spruce Goose” flying boat in 1947.

And previously, this PB2Y-5 carried the staff of U.S. Navy Admiral Chester W. Nimitz to Tokyo Bay for the Japanese surrender aboard the USS Missouri, which took place Sept. 2, 1945.

Though we can’t fly in a Coronado, a preserved copy of the PB2Y-3 Pilot’s Handbook provides some interesting insight into this fabulous flying boat.

The hull of the Coronado was made of six main compartments, isolated with watertight bulkheads. The left and right wing floats retracted to form the wingtips of the Coronado, in the fashion of the smaller PBY Catalina. The Coronado’s two large floats were interchangeable from left to right. This simplified both construction and field repairs.

The floats were electrically operated. The pilot and the flight engineer each had a set of two push-pull knobs with which they could select “floats up” or “floats down.” The retraction or extension could be stopped in mid-cycle by pulling the engaged push-pull knob back out. The pilot’s float control knobs were the master system, and would override the flight engineer’s controls.

The action of extending or retracting these Consolidated floats involved folding or unfolding braces to make the floats rigid when extended. It’s not an instantaneous action, and requires some planning to get the floats sequenced when they are required to be in either position. The Coronado pilot’s handbook underlines a recommendation against operating the floats at speeds above 160 knots.

The Coronado was large enough to have a galley and crew bunks.

Between the wing’s front and rear spars, four sets of bomb bays in each wing could carry bombs ranging from 100 pounds to 1,000 pounds apiece. Additionally, external shackles could carry torpedoes and bombs.

If sending a lumbering four-engine flying boat on a torpedo run seems doomed in hindsight, provisions were at least built into the PB2Y-3 to allow this, as noted in the pilot’s handbook: “Firing of the torpedoes, MK13, 13-1, and MK15, is controlled by the pilot and co-pilot.”

Some aspects of the Coronado’s 1930s technology are simply rustic. In the bomber variants, the bombardier — listed in the pilot’s handbook as “the bomber” — had an aiming window that could become fouled by sea spray or other contaminants.

While it had provision for an alcohol spray to keep the glass free of ice or salt, there was another way to clean the bomber’s window, as noted in the handbook: “The bomber’s sighting window is wiped by hand. Armholes in the hull are located on either side of the window, which allow the bomber to reach outside and wipe the window with a cleaning brush, which is stowed in a canvas pocket on the starboard side of the bow compartment.”

The PB2Y-3 featured some design similarities with Consolidated’s B-24 Liberator land-based heavy bomber. Both used rudder pedals that rode in floor-mounted tracks. Both also had control wheels mounted to push-pull tubes instead of pivoting vertical columns, although the design of these features had a different appearance for the Coronado and the Liberator. The changes in rudder pedal appearance include the lack of brakes on the pedals of the water-borne Coronado flying boat.

The Coronado’s four Curtiss Electric propellers were different outboard and inboard. The inboard two propellers were reversible pitch. On some Coronados, these reversible props were four-blade while the outboard propellers were three blade.

The throttles on the Coronado were vertical levers with horizontal gripping surfaces in the fashion of the throttles on a B-17. These allowed for the simultaneous manipulation of all four throttles, or the deliberate use of the inboard engine throttles, which featured the Coronado’s reverse-pitch capability. The pilot had the reverse pitch controls at his station. The flight engineer controlled propeller feathering.

Reversible pitch propellers can aid in slowing the forward motion of a PB2Y on the water. The reversing action places loads on the engine, and the procedure required adherence to RPM limitations, as described in the Coronado pilot’s handbook.

Engine speed on the inboard motors needed to be reduced to 800 RPM. The reverse pitch safety switch was flipped to the On position. Then the reverse pitch control was moved to Reverse. Once an indicator light turned off to show the reversing movement of the propeller blades had taken place, the throttle could be advanced to achieve greater reverse thrust action.

A drifting flying boat has the capacity to inflict damage on itself and anything it strikes on the water. The manual said: “Full takeoff power may be used for emergency maneuvering in reverse pitch, but only for a short time and with care to see that the maximum allowable engine temperature is not exceeded. Normally, reverse pitch operation should be conducted within a range not to exceed 50% of full throttle.”

The Coronado pilot was warned to watch throttle settings on the Pratt and Whitney R-1830 engines. Spark plug fouling from low RPMs during water operations were a concern, while engine ignition system overheating could happen if the Coronado taxied on the water with high engine RPMs. Cowl flaps were to be full open for all taxiing operations.

Depending on configuration, empty weight of a Coronado ranged from about 39,000 pounds to more than 40,000 pounds. Gross weight was set at 66,000 pounds — that’s 33 tons floating on the waves until lifting off with a torrent of water shedding from the broad hull.