Lewis Engineering 502BL72 TIT Thermocouple Indicator 0-1500°C 7-Pin Aviation

Lewis Engineering 502BL72 TIT Thermocouple Indicator 0-1500°C 7-Pin Aviation

The Lewis Engineering 502BL72 is an aviation-grade Turbine Inlet Temperature (T.I.T.) thermocouple indicator designed to monitor engine inlet temperature across a 0 to 1500°C range. It features a circular analog dial face with a moving pointer scaled in units of x100°C, combined with a mechanical digital counter display — visible in the photos reading 332 (i.e., 332°C). The instrument is fitted with a 7-pin circular connector at the rear and incorporates a red-lighted potentiometer for illuminated cockpit use in low-light environments. Manufactured by The Lewis Engineering Co. of Naugatuck, Connecticut.

Specifications & What's Included

• Part Number: 502BL72
• Manufacturer: The Lewis Engineering Co., Naugatuck, CT, USA
• Instrument Type: Turbine Inlet Temperature (T.I.T.) Thermocouple Indicator
• Temperature Range: 0 to 1500°C
• Scale: Analog pointer, graduated x100°C; integrated digital counter display
• Display: Circular black dial face with white scale markings, labeled "T.I.T."
• Indicator: Mechanical digital counter (shows 332 in photos)
• Thermocouple Type: Potentiometer type (per rear label)
• Illumination: Red lighted potentiometer
• Connector: 7-pin circular connector (rear-mounted, threaded collar)
• Housing: Cylindrical black metal body
• "OFF" flag visible on dial face
• Country of Manufacture: United States
• Unit only — no additional accessories observed

Applications

Turbine Inlet Temperature indicators like the 502BL72 are used in aircraft to measure the temperature of exhaust gases entering the turbine section of a jet or turboprop engine — a critical parameter for monitoring engine health and preventing over-temperature damage. The T.I.T. reading is one of the primary engine instruments a pilot monitors during high-power operations such as takeoff and climb. Lewis Engineering was a well-known US manufacturer of aircraft engine instruments, producing gauges and indicators for both military and civilian aviation applications. Instruments of this type were common in fixed-wing turboprop and jet aircraft from the mid-20th century onward and remain relevant for maintenance, restoration, and spare-parts sourcing on legacy aircraft platforms. The 7-pin connector and potentiometer-type thermocouple design are characteristic of that era of panel-mount aviation instrumentation.