Boeing tweaks BBJ with EVS

By Matt Thurber

May 21, 2008
Avionics

Boeing continues to add utility to its BBJ series corporate jets, and the latest effort is the addition of enhanced vision system (EVS) capability to the BBJ’s head-up display (HUD). To add safety to BBJ operations, however, Boeing is also working on delivering the EVS display on one of the Honeywell LCDs on the instrument panel, so the first officer can see the same EVS picture that the pilot sees on the HUD. “That’s a fairly significant safety element,” said Boeing Business Jets chief pilot Stephen Taylor.
Boeing is also working on certifying the EVS system so that operators can receive credit to descend below published minimums to 100 feet per FAR 91.175.

Boeing had flown EVS on a 737 technology demonstrator about a year ago, according to Taylor, but the infrared sensor was mounted low on the nose of the aircraft. “We found the parallax is quite significant if the sensor is below the pilots’ feet,” he said. The sensor mounting was changed and now it is installed in a small blister on top of the radome. This brought the sensor closer to eye level and eliminated the parallax problem.

The program also was delayed when HUD supplier Rockwell Collins had to switch sensor manufacturers because of an International Traffic in Arms Regulations issue with the first sensor. Boeing has already completed the service bulletin for the bracket and wiring installation for the EVS add-on, and Rockwell Collins is working on a supplemental type certificate (STC) for the EVS sensor installation and software changes to the HUD computer. Certification should take place early next year, Taylor said.

Customers are now asking about synthetic vision systems (SVS), which are spreading rapidly into general aviation aircraft. For BBJ operators, SVS “is still fairly leading edge,” said Taylor. “We’ve been studying it for quite some time. It will come, but we won’t be at the front end of that market.”

Boeing is seeing increasing market acceptance of its lower cabin altitude (LCA) STC package. Because BBJs fly far fewer hours and log fewer cycles than Boeing airliners, Boeing was able to engineer a 6,500-foot cabin altitude modification for BBJs. The modification, which lowers cabin altitude from the original 8,000 feet, is available for earlier BBJs and is now incorporated in the BBJ production line.

Boeing conducted a study where volunteers stayed in altitude chambers for 12 hours, and it was found that at the 6,500 foot cabin altitude, the volunteers experienced a significant reduction in fatigue and discomfort. There are many benefits to lowering cabin altitude just 1,500 feet, Taylor said, including better immune system health, less fatigued crew and greater comfort.

Eight BBJ customers ordered the retrofit and six are now flying. The retrofit includes replacing the cabin pressurization controller and revising the pressurization schedule. To implement the LCA modification, Boeing must first analyze the customer airplane to see how any previous modifications or repairs might affect the pressurization system. BBJ serial numbers prior to number 30 or so need some floor beam modifications, but more modern BBJs don’t need that treatment. “The biggest element is the analysis of the previous history,” said Taylor. “That’s a little bit of a wildcard.”

BBJ operators should be able to switch to carbon brakes later this year after Boeing’s service bulletin is approved. The carbon brakes last longer and weigh 700 pounds less than the original steel brakes, providing a substantial increase in available payload.
While the carbon brakes cost more, they also last longer, so the extra cost balances the savings in replacement costs. “The cost is almost a wash,” Taylor said. “Weight is the big thing. Every airplane I’ve flown, weight matters.”  

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