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Pylon Decoder Unit (PDU) Type D

Technical Information

Catalogue No: C1792
Category: Stores/Weapon Management
Object Type: Module/Sub-Assembly/Component
Object Name: Pylon Decoder Unit (PDU) Type D
Part No: 32-011-03
Serial No: 5245
Manufacturer: Marconi Avionics
Division: Instrument Systems [ISD]
Platform(s): Tornado
Year of Manufacture: circa 1980
Dimensions: Width (mm): 55
Height (mm): 195
Depth (mm): 300
Weight (g): 2,667
Location: Rack RAA04 [Main Store]

Marconi Avionics
PDU Type D Part No. 32-011-03
Ser. No. 5245 Spec SP. P.80012
Design Code K0656 MFG. Code K0656
NATO Stock No.
Part No. 32-011-03
Serial No. 5245
Mod Status

Mod Status


The Stores-Management System (SMS) on the Tornado GR. Mk1 controls the selection, arming, and release of the aircraft’s bombs, rockets, guns and guided weapons and times the release in accordance with target data, wind, type of weapon, and other inputs.. Emergency and selective jettison facilities are also provided.

The system consists of four distinct unit types, which are interconnected by means of digital data transmission. The SMS comprises:

• 1 Weapon Programming Unit (WPU)
• 1 Weapon Control Panel 1 (WCP-1)
• 1 Weapon Control Panel 2 (WCP-2)
• Up to 7 Pylon Decoder Units (PDU), the actual number depends on the number of available pylons and the configuration loading

The armourers tell the stores management system, via a Weapon Programming Unit (WPU), what weapons are loaded and on which pylons. In the rear cockpit the Navigator/Weapon System Officer (WSO) then operates the Weapon Control Panel 1 (WCP-1). It has a multi-line display and programmable soft keys. He can enter the configuration loading, define weapon packages and select a weapon package for release, all before flight. A weapons package consists of the type of and number of weapons to be released, whether singly, in pairs, or in salvo. If a stick of bombs is to be dropped the desired interval is set in metres. Finally fusing is allocated. The WCP-1 also features selection keys for jettisoning single or multiple stores.

In the front cockpit the pilot operates the Weapon Control Panel 2 (WCP-2). It contains function keys and indicators for operating the self-defence A/A missiles and the guns which can also be used for attacking targets on the ground.

Each pylon may contain one or more  Pylon Decoder Units (PDU). The PDU comprises all power electronics to produce the power signals for stores release and monitoring circuitry for the stores. There is a special digital data link between a PDU and the WPU. In addition there are wing mounted Pilot Indicator Ordnance Release units.

The Power Interface Unit conditions the aircraft power for the SMS.

Crew workload is minimised by eliminating from the weapon package selection process both safety critical and non-applicable options.

The system can handle 26 types of weapon, controlling arming, fusing, firing or release functions from its 35 outputs. The system also initiates the timed and sequenced emergency and selective jettison of all weapons and other stores such as fuel and equipment pods.

This is a controlled output of 29 pulses over 2.2 seconds. A comprehensive bogus weapon inventory is also included for training purposes.

Among the principal design aims of the Tornado Stores Management system were: meeting the specified rates of safety, jettison availability and mission success, an unprecedented degree of electromagnetic compatibility hardness and a significant reduction in crew workload. The system was also engineered to provide a minimum of interconnect wiring between the twelve units.

To achieve these targets, the Company developed a dual channel digital architecture system employing mini-computers and a digital data transmission system to provide the required integrity. Wherever possible CMOS circuitry was used on account of its low power consumption, elimination of  the need for cooling and to meet the electromagnetic compatibility specification. Both channels are fully synchronized and perform in a consolidated mode until channel unserviceability is detected, when authority is given to the serviceable channel to proceed independently.

The level of redundancy ensures that the channels only close down for safety critical failures and that the emergency jettison system is not only separated from processor control but made duplex to avoid any consolidation requirements. The system is basically a duplicate, “both on line” arrangement and is highly self-monitored. A release is only permitted if both lanes agree, or if, on disagreement, the faulty lane is detected by its monitoring.

The need for safety and mission success has been the prime consideration in formulating system philosophy, design and implementation.

The contract was work shared with Selenia in Rome with the majority of the design carried out by Marconi-Elliott Avionic Systems Limited with Selenia responsible for manufacturing most of the later development phase hardware. An upgraded system was developed for the GR.Mk4

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