Boeing has selected Crane Aerospace & Electronics (Hall 5, Stand A20) to supply tire- and brake-monitoring (TBMS) and AirWeighs onboard weight-and-balance systems for Model 777 aircraft. Deliveries of TBMS-equipped aircraft began last month, while AirWeighs, which is to be a standard production-line fit on 777F cargo variants, will enter service when deliveries begin in late 2008.
Using Crane’s SmartStem wireless technology, the TBMS transmits tire-pressure and brake-temperature information from each landing-gear wheel to the flight deck, via a wireless stem that replaces traditional valve stems. The same data and other stored information can be sent to an onboard control unit or a handheld reader through a tire-pressure sensor wand.
SmartStem is designed to provide easy and accurate tire-pressure monitoring, important in ensuring optimum life from the tire carcass. For example, Goodyear has demonstrated that a 5-percent drop in tire pressure can result in a 50-percent fall in carcass life. Also, the lighter system can save weight, up to 60 pounds on a 777, according to Crane.
The wireless technology originates in general aviation, where Crane has forged an agreement giving Cessna distribution rights to a “miniversion,” while retaining access to the commercial and military aviation markets. Crane then was able to supply Boeing with the equipment as an onboard (not handheld) system with integral wiring and a cockpit display.
This led to an application that can be specified for the 777, including the freighter variant, which will sport the onboard AirWeighs system that also has generated interest among regional airlines, according to Crane.
Accurate weight-and-balance and center-of-gravity calculations are vital for safety, including correct fuel uplift, and for economic operation. Pointing out that there was no regulatory mandate beyond keeping paperwork for civil flights, Crane customer-satisfaction group vice president Kevin Wright said the latter was a factor in a Lockheed C-130 Hercules accident during military operations.
Developed for Navair
AirWeighs is currently being developed for the U.S. Naval Air Systems Command (Navair) for the C-130 Hercules, as well as commercial applications. The system uses a unique method of automatically establishing aircraft gross weight and center of gravity, said Wright. AirWeighs measures actual aircraft weight and determines c.g. by converting landing-gear strut measurement to “on-aircraft scales” that calculate the load-bearing pressure at each leg.
While current methods use historic data for, say, average passenger, baggage and aircraft weight, combined with passenger and cargo location data, Crane said such calculations are only estimates. In addition, aircraft manufacturers and airworthiness authorities should consider the practical limitations imposed by manual systems, according to Crane.
The AirWeighs equipment provides the greatest benefit when integrated into both operations and maintenance practices. Crane said that use of the system permits less-restrictive flight envelopes, reduced turnaround times, fewer gate delays, improved fuel efficiency, enhanced utility with multiple forward-c.g. operations, reduced need for ballast and central load-control efficiencies.
Wright said Navair had become interested because it had no system to meet the need for quick aircraft dispatch. After developing a military system, Crane plans to promote the equipment in the civil market, starting with aircraft manufacturers.
