PBY CATALINA PILOT DIRECTOR INDICATOR (PDI)

Whilst often regarded as one of the slowest aircraft of WWII, the Consolidated PBY Catalina was both  rugged and reliable aircraft and ideally suited to long distance maritime patrols where it performed a wide and diverse range of roles.

Initially designed as the eyes and ears of the fleet and able to cover large distances seeking out enemy shipping, the PBY Catalina also became an essential part of the allied’s search and rescue operations, locating and picking up downed aircrew and ship survivors.

For most of the war, Britain was extremely reliant on supplies and military hardware from the US and Canada, with North Atlantic supply convoys playing a critical IN maintaining the Allied war effort in Europe. 

The German High Command were well aware of Britain’s vulnerability and sent its fleets of submarine ‘wolf packs' into the North Atlantic to harass and sink as much allied shipping as possible.

Along with Britain’s Coastal Command Sunderland Flying Boats and their marinised, long-distant Wellingtons and B-24’s the PBY’s patrolled either end of the convoy routes seeking out the German submarines and attacking them with bombs and depth charges.

Unfortunately for the Catalina, its lack of speed was a major drawback in this role and unless it surprised a U Boat recharging its batteries on the surface or managed to drop its depth charges before the U boat had dived too deep, it could only report the U Boat’s position.

This was to change dramatically after the Allies had made significant advances in radar technology and had also secretly broken the German radio codes used to communicate with the wolf packs.  

German U Boats started to suffer substantial losses as they surfaced to find Allied aircraft already overhead seemingly waiting for them.

Rather than crash diving in the hope of evading depth charging, U Boat commanders were suddenly ordered to stay on the surface and defend themselves with their deck mounted anti aircraft guns.

For the PBY Catalina, with its slow speed and reliance on low altitude bombing this was to prove their greatest challenge.

In Europe, the USAAF were bombing stationary targets from great heights with hundreds of aircraft all focused on one target whereas in the often wild and stormy weather of the North Atlantic, the PBY’s target was one tiny, moving small speck in a vast ocean. 

It was a speck which was now firing a concentrated barrage of high calibre, anti aircraft fire directly at them as they made their slow, lumbering bombing run toward it.

With four bomb racks under each wing, carrying up to 1000lb of bombs and depth charges, the PBY’s ordinance was set to explode at a depth of 25 feet to 30 feet which was still effective enough against surfaced submarines if they could be delivered accurately.

Unfortunately the U. Boat was not only directing a steady stream of deadly fire at the approaching PBY but also frantically zig zagging through the water at the same time.

In the nose of the approaching PBY, the Bombardier/nose gunner would have slid down the aluminium concertina blind or removed the covering hatch that protected the plexiglass bomber aimer's window from salt spray and be adjusting his range finder bomb sight whilst making continuous adjustments to the PBY’s course in order to keep the U Boat in his cross hairs.

Check out this old Ministry of Defence footage of a Catalina bombing run here:

These course corrections were inputted via a course computer connected to the Catalina’s Pilot Direction Indicator (PDI) mounted in the middle of the cockpit flying panel.

Manufactured by the Roller Smith Company, the PDI had four graduation marks to the right and the left of a centre zero.

The pointer would fluctuate left or right in response to the signals received from the automatic pilot’s directional stabiliser. Movement of the aircraft in the desired direction would return the pointer to the zero position.

In the early days of bombing, the pilot would manually correct the bomb run course by manoeuvring the aircraft to bring the PDI’s pointer back to zero as directed by the bombardier but with the later refinements of bombsight technology and its integration with the aircraft’s autopilot, course changes were done without any pilot involvement whatsoever ever.

With the Bombardier now effectively in total control of the aircraft, the pilot could do nothing but wait until he heard the words ‘bombs gone’ over the intercom and then grab the column and wrench it back to put as much distance between the PBY and the anti-aircraft fire as quickly as possible.

While it was extremely dangerous work for the PBY, Coastal Command did achieve a number of successes with one PBY pilot, John A. Cruickshank receiving the Victoria Cross for sinking U-361 and still managing to nurse his badly damaged Catalina DA-Y back to base whilst also suffering serious injuries himself.

The Pilot Director Indicator (PDI) was installed in both the USN’s PBY Catalina and PB4Y Privateer as well as the USAAF heavy bombers such as the B-24 Liberator, B-29 Super-fortress and medium bombers like the B-25 Mitchell and B-26 Marauder. 

This model PDI is in excellent condition for a PBY Catalina flight instrument over 75 years old. The face dial glass is unmarked as too the PDI’s rear casing and would make a fantastic pilot gift or a one-of-a-kind gift for that special aviation enthusiast in your life. 

This PBY Catalina Instrument comes complete with detailed Scale Model, Mango Wood Stand & Plaque plus Printed Fact Sheet featuring photo of instrument in aircraft cockpit.

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