THERMOCOAX Aircraft Products – Bleed Air Leak Detector – NEGACOAX©


The THERMOCOAX Bleed Air detector is designed to detect leaks in an aircraft’s pneumatic duct system by sensing the temperature of the overheated air surrounding the leaking duct.

The NEGACOAX technology gives the location of the overheat condition, annunciates the overheat to the aircraft’s crew warning system.

The NEGACOAX consists in a homemade Mineral Insulated Cable, doped with eutectic salts. When the NEGACOAX detects an overheat (air leakage) the cable Impedance value will drop down and the capacitance value will increase very fast.

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Example of curve with NEGACOAX NG124 :

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The THERMOCOAX’s current technology uses the Binary compound within Eutectic as described below, in others words, liquidus and solidus will melt entirely at the same temperature.

This specificity gives the high accuracy of this technology :

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Insulated Cable homemade manufacturing, this technology offers a high reliability and nearly no maintenance.

The maximum length of each NEGACOAX detector is 5 meters. We have no length limitation regarding the number of detector connected together to make a complete loop.

THERMOCOAX’s NEGACOAX detectors are typically installed at heat critical points throughout the aircraft structure. Typically, these are located in the wings, engine pylon, fuselage, empennage and tail cone (APU compartment).

This technology can be applied to military, commercial transport and general aviation aircraft.

The electronic control system associated will get 2 separated electrical parameters :

  • Impedance

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  • Capacitance

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By connecting both ends of the NEGACOAX loop with the electronic system, the leakage location can be determined by current ratio.


NEGACOAX Detector Characteristics

  • Nickel Sheath
  • Insulant: Al2O3 + eutectic salts
  • Constantan conductor
  • Line resistance at 20°C: 2,15±0,05Ω/m
  • Diameter Ø2,2mm +0,2/-0,4
  • Length L<300cm ±6mm
  • Length 300cm<L<460cm +19/-0
  • Max detector Length 460cm
  • Mass=25gr+(27*L)gr with L= length in meter
  • Service Life: 20 years
  • MIL and RTDO 160 standard
  • 100 000 Flight hours
  • MTBF > 300*106 hours
  • FMEA 1.954*10-7 Failures/FH



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NEGACOAX Product Ranges :

  • NG124
  • NG154
  • NG180
  • NG204
  • NG215
  • NG232

Thermocoax has a large experience on aircraft platform with :

  • McDonnel Douglas MD90
  • Airbus A340
  • Dassault Falcon F5X
  • Embraer KC390
  • Bombardier Global Express
  • Airbus Helicopter


Thermocoax supplies a large range of accessories to fix the detectors on the aircraft structures

Mechanical System for :

1 or 2 loops :

303 925    303 925 (3)

Electronic System

NEGACOAX is compatible with any electronic system with the following characteristic :


Thermocoax is working in partnership with aircraft industry electronic specialist.


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Test Loop

Thermocoax offers as option an upgrade of the detector with integrated shunt resistor in the connector. This shunt (>30KΩ) is connected between the core and the sheath.


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