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SCADC Static Pressure Compensator (SPC)

Technical Information

Catalogue No: C1241
Category: Air Data
Object Type: Sensor/Transducer
Object Name: SCADC Static Pressure Compensator (SPC)
Part No: ACA1310
Serial No: LM514
Manufacturer: Dunlop Aerospace
Division: Unknown
Platform(s): F-4 Phantom
Year of Manufacture: Unknown
Dimensions: Width (mm): 132
Height (mm): 146
Depth (mm): 101
Weight (g): 2,280
Location: Rack RAA10 [Main Store]

Unit ACA1310
No LM514
Mod 1,2
[repair marks]
ACA1312 Iss/G
M22740 DA18
000 PrG
SerNo LM514
FSCM K1037
ACO 45127 Iss 1 DA1312


The Static Pressure Compensator (SPC) was used in the CPU-143/A (50-059-XX), one of the Standard Central Data Computer SCADC family units, and was used on the F-4 Phantom. Its function was to provide reversionary pneumatic Static Source Error Corrected (SSEC) data to the Pilot instrumentation. To do this, high pressure Engine Bleed Air was passed over a jet valve (inside the SPC) to create negative pressure; this is then regulated and mixed within the SPC under control of the SCADC electronics to create a pneumatic output equivalent to the Error Corrected Pitot-Static (Ps) pressure.
The tall structure with a stainless cylinder is the regulator diaphragm, the smaller diameter grey anodised structure with the pipe on top houses the jet valve and Solenoid Valve, whilst the black structure holds the Servo Valve which mixed the positive and negative pressures (under control of the Pc transducer) to create the SSEC output. (Akin to a hot/cold water mixer.)
The unit was designed by Andy Gibson in collaboration with Dunlop.

In 1981 Instrument Systems Division began the design of a new generation of Air Data Computers designed for the combined USAF and USN Standard Central Air Data Computer (SCADC) programme. The system was designed to fulfil the retrofit requirements of 38 different aircraft types and to do so with only four configurations. The aircraft types include the following:-


A-4M and TA-4J Skyhawk, A-6E/F, KA-6D and EA-6A Intruder, EA-6B Prowler, TC-4C Gulfstream, A-7D/E/K and TA-7C Corsair II, C-2A Greyhound, E-2C Hawkeye, KC-135 Stratotanker, C-5A/B Galaxy, C-141A/B Starlifter, F-111A/E/D/F, FB-111A, EF-111A, F-4C/D/E/G/J/N/S, and RF-4B/C Phantom and the S-3A/B and US-3A Viking. In 1992 an order for a further 290 units was received, being the eighth option, bringing the total procured to 5552 units. 387 units of the SCADC system were at this time being supplied for the F-14 Tomcat.


The high commonality was achieved with a unique software re-configurable design. Output parameters, ranges and scalings are selected for each aircraft type by the software, which recognises the host from a code wired into the aircraft connector pins. The SCADC core hardware set provides over 80% of the hardware in every application and the remainder is addressed by one or two special-to-type modules. A multiplicity of analogue interfaces can be handled and the Mil-Std 1553 DataBus is also a feature. Production commenced in 1985 with first deliveries the following year and in 1989 these deliveries surpassed 4,000 units. In addition in 1988 ISD received the Queen’s Award for Technological Achievement for SCADC.


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