|Object Name:||Static Air Pressure Transducer|
|Year of Manufacture:||1967|
|Location:||Main Object Store|
S. Transducer Mk.2. Type A
Type No. 3D753
Ref No. 6A/6826
Ser. No. 1014/67
From ZF581, the former Gate Guardian at Rochester.
This Static Transducer unit was designed for and fitted to either the English Electric Lightning or the Blackburn Buccaneer.
The unit contains the pressure transducer which converts the Static pressure, from the aircraft sensor, to an electrical analogue. The static pressure system is open to the exterior of the aircraft to sense the pressure of the atmosphere at the altitude at which the aircraft is flying.
The difference between the Pitot pressure and the static pressure is called dynamic pressure. The greater the dynamic pressure, the higher the airspeed. So the Static Transducer working with the Pitot unit has the capability to provide an output of indicated airspeed, limits on the altitude and also to manage the maintenance of a specific altitude; the height lock function. The Pitot and Static transducers will drive a cockpit instrument for indicated airspeed but will also feed into the Autopilot and automatically control the flying surfaces to maintain a pre-set speed or altitude.
The Differential Pressure Transducer within the box contains two aneroid capsules, or diaphragms, which expands and contracts with the pressure input from the Pitot tube. The case around the diaphragm is airtight and is vented to the static port. The use of multiple aneroid capsules is to multiply the movement. The movement of the diaphragm is mechanically coupled to a non-linear cam assembly with two rows of fifteen adjustable grub screws to set the desired profile. Within the casing is a wire wound resistor which is driven by the cam mechanism such that an electrical output of indicated airspeed is provided corrected by the cam profile for the non-linearity of the diaphragm movement. A small servo motor was used to amplify the movement of the capsules to operate the internal gear train.
This is an early version of the Static Transducer probably for the first production run of Lightnings. The relationship between ‘Type’ and ‘Mk’ numbers is not known but it would seem that ‘Type’ (in this case ‘Type A’) can have incremental ‘Mk’ numbers; this is a ‘Mk2’.
This item also has a mod label:
A.D.S. Nos 72-88-109
And has a white circular stamp: "EBL627"