(Example image from XS458)



Stores Ref. No.:6A/12667
Manufacturer:Sangamo Weston
Attachment:Clamp, instrument securing type C.12956


For monitoring external "ram air temperature", or "total air temperature", which can rise under conditions of hot ambient weather, and fast low level flight.

The purpose is to protect the airframe and certain pieces of equipment from overheating. The aircrew manual linked below gives temperature limitations.

This indicator is a ratiometer type of indicator, fed from a total air temperature probe mounted on the spine skin.

It will operate when DC power is online.


This indicator is included in the T Mk.5 electrical "Vol. 1" 1985 amendment but is not in the 1974 amendment, suggesting it was a modification introduced between the two dates. This window may also be narrowed further as the T Mk.5 wiring diagrams at A.L.3, from November 1981 also include this indicator.


The internals of the sensor and indicator illustrated, and interconnecting wiring taken from AP101B-1005-10 Sheet 28, A.L.3, Nov. 1981.


I wrote a 'nasal' script for the FGUK Lightning model to calculate the ram air temperature, which takes the ambient temperature and compensates for Mach No., so currently the data is available within the simulator model, I now need to find an indicator to work out how to electrically drive it.


Indicator general and technical information:
A.P.112G-0508-1,Chapter 1, Feb. 1993 - Indicator Type S149 Series

Indicator general and technical information:
A.P.112G-0508-1,Chapter 1-26, Feb. 1990 - Indicator Type S149-1-552

T Mk.5 electrical "Vol. 1":
A.P.101B-1005-1B, Sect. 7, Chap. 6, A.L.94 March 1985, Miscellaneous Instruments - Paragraph 12

F Mk. 3, T Mk. 5 and F Mk. 6 aircrew manual:
A.P.101B-1003, 5 & 6A, Part 1, Chapter 7, A.L.2, Nov 1984 - Instruments - Paragraph 53

F Mk. 3, T Mk. 5 and F Mk. 6 aircrew manual:
A.P.101B-1003, 5 & 6A, Part 2, Chapter 1, A.L.2, Nov 1984 - Airframe Limitations - Paragraph 56

Total Air Temperature:
Wikipedia Explanation ↗