NBAA Convention News

Meggitt’s ‘smart’ fuel probe more accurate

 - September 30, 2008, 7:10 AM

Meggitt (Booth No. 5189) is unveiling a new smart fuel probe that will give operators greater certainty over their aircraft’s current fuel reserves, as well as offer better reliable and easier maintainability.

The company has developed a device that uses time domain reflectometry (TDR) to send fuel data to the cockpit via digital buses, a first for civil aviation, it claims. According to Meggitt Sensing Systems vice president Stuart Parker, the smart probe is a big leap forward from existing fuel probes, which he said are barely more sophisticated than a lavatory sistern float.

“We developed many of the current generation of float and capacitance-type sensors, so we know the limitations of these devices,” he explained to NBAA Convention News. “What we found was that operators don’t trust conventional fuel level gauging systems, so they don’t use them. They fill up to the maximum and take care to track the distances they travel. What’s more, many of today’s level sensors can be used only with certain fuels and they deliver significant errors when fuels are changed.”  

Traditional fuel probes can also lead to major maintenance headaches, especially in larger business aircraft, which might have as many as 20 separate probes fitted throughout their fuel storage areas. The new smart probes are completely self-diagnostic, making it much easier to determine which probe is malfunctioning and to complete trouble-shooting.

The TDR sensors can work with any type of aircraft fuel, including jet-A, diesel, avgas or new bio fuels. They can recognize the differences between fuels and alert operators when the wrong fuel has been supplied.

The technology uses the electronic echoes from high-speed pulses fired down “waveguide” rods extending into the fuel tanks to locate the fuel-to-air interface and measure distance via the return time of the pulse. The gauging system includes probe antennas, signal processing and high-speed digital communications and an array of self-diagnostics. Fuel data is relayed to the cockpit avionics via digital buses.

The equipment has already been supplied for several commercial airliner applications, and at least one business aircraft manufacturer has agreed to start using them in its models. According to Meggitt, the new smart probes are easier to calibrate than traditional fuel probes and are also lighter.    

“We have overcome a number of challenges to bring this next generation sensor to market, including developing the ultra-fast analog electronics you need to determine differences in echo signals that last for picoseconds, which is around a millionth of a millionth of a second. And we had to make the sensor immune to unwanted environmental influences such as temperature,” explained Parker.  

Meggitt Sensing Systems also provides advanced condition monitoring sensors for demanding environments such as inside the hot sections of engines, for example on the Rolls-Royce BR725 turbofan for Gulfstream’s new G650. The company is providing this engine’s ignition system and other Meggitt divisions are supplying pneumatic valves, fire detection equipment, and wheels and brakes for the aircraft.

Meggitt is making substantial investments in extending condition monitoring to comprehensive integrated vehicle health monitoring (IVHM). The aim is to take a more holistic approach that would deliver comprehensive knowledge about an aircraft’s condition rather than just data.

In addition to the engine, this approach would analyze the fuel, as well as the structural condition of the airframe, wheels and brakes. Parker said that major manufacturers are now seriously considering this approach. He believes it could be in service in about 10 years and that it would be of particular interest to operators with large fleets.  

Meggitt is working with Canada’s AeroMechanical Services to improve the ability to report on maintenance issues and other aircraft data during flights. Data can be reported via satellite to ground stations where a secure Web-based server will relay it to operators and/or manufacturers.

The goal with IVHM is to make the technology scalable and affordable for business aviation applications. Separately, the group believes it has now achieved this for environmental control systems for cabins and cockpits, thanks to the incorporation of vapor-cycle technology provided by Keith Products, which the group acquired last year. According to Jim Duncan, president of Meggitt Thermal Systems, the company has been able to reduce the price point for ECS to the extent that it will be affordable as standard equipment on new aircraft, as well as available for retrofit.

Meggitt Thermal Systems is also engaged in R&D work on new electrothermal ice protection systems that are attracting interest from business aircraft OEMs. These will be able to deliver as much heat as is needed to where it is needed in a way that is more energy efficient than existing bleed-air pneumatic systems.