AS-LLS Aircraft Qualified Liquid Level Sensor

FCI provides single point liquid level switches that utilize a no moving parts thermowell mounted sensing element with either integral or remote electronics that provide indication of presence or absence of liquid or interface at the sensing location. The liquid level element is directly installed into tanks, reservoirs, sumps and gearboxes on commercial and military aircraft, spacecraft, vehicles and marine applications.

Please complete and submit an FCI Aerospace Application Data Sheet or contact FCI's Field Representative in your area to receive a technical quotation for your Liquid Level and Interface Switch application.


  • Oil Level Sensor
  • Collection Sumps
  • Automation of Sight Gauge Level Detection
  • Waste or Grey Water Reservoirs
  • Hydraulic Reservoirs
  • Coolant Reservoirs
  • Fuel Level Detection
  • Oil / Water Interface Detection
  • Potable Water Reservoirs
  • Backflow Reservoir Detection


Service: Level switch for liquid / gas and liquid / liquid interfaces

Sensor Element Material: 316 stainless steel all welded construction

Electronics Enclosure: 316 stainless steel; hermetically sealed

Electrical Connection: D38999 or compatible

Process Connection: Flanged with O-ring seal

Insertion Length: Per customer requirement

Signal Output Options
  • Sourcing output: Wet signal: source 240 mA at 28 VDC; dry signal: source Ø VDC
  • Open collector output: Wet signal: closed, sinking up to 100 mA at less than 0.5 VDC; dry signal: open, leakage < 10 µa at 30 VDC

Electrical Power Input: 28 VDC nominal per MIL-STD-704

Power Consumption: 50 mA to 85 mA depending on type of output signal(s)

Weight: 8 oz [227g] maximum

Proof Pressure: up to 2,000 psig [138 bar (g)] as required by application

Switch Point Adjustment: Factory set at customer specified switch point

Operating Temperature Range
Sensor Element: - 65 °F to 500 °F [- 54 °C to 260 °C]
Specify actual requirement
Electronics: - 40 °F to 257 °F [- 40 °C to 125 °C]
Higher temperatures available optionally

Repeatability: ±1/8 ″ [3 mm] of liquid level elevation

Time Response: 1-3 seconds typical, depending on fluid type and switch point

EMI and Lightning Protection: MIL-STD-461 and RTCA/DO-160

Qualifications: MIL-STD-810 and RTCA/DO-160

Quality Systems Approval: ISO 9001, AS9100