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Friday, March 4, 2011

Parameters Of In-Seat Power

Take a look around the cabin the next time your flight reaches 10,000 ft., when that familiar "ding" descends from the PA. As passengers unpack their laptops, iPhones and portable DVD players—among the most common carry-on personal electronic devices or PEDs—and plug in, consider where that power comes from and whether the supply will be plentiful enough for you to have any.
Complaints ensue from disgruntled flyers who can’t power up their laptops in the air. “The reliability of these [in-seat power] systems is not where it needs to be,” maintains an industry insider.
As with so many things in life, the term “reliable” is relative. It's a matter of definition, perhaps even of perception. “The reliability [of in-seat power is] somewhat commensurate with the reliability of the IFE system itself,” contends Joe Keegan, manager of IFE development for Boeing’s 787 program. In terms of seat availability, that’s “maybe 99.9%.” Keegan concedes “there’s a possibility” a particular seat may be bereft of power, but “it’s not generally because of the outlet itself.”
It’s related more closely to the number of people drawing power off the system and the order in which they plug in. On a given flight, the absence (often temporary) of in-seat power is a calculated function of how much power the carrier parcels out and to whom.
This first-come, first-served basis for granting access to aircraft power supply may be limiting airlines' potential to gain ROI from in-seat technology. Carriers use connectivity to generate ancillary revenue; services such as Air Cell's Gogo inflight internet recapitalize their investment. Without a charged device, broadband access is moot.
“You want to make sure the passenger can continue to charge and use his electronic device,” says Jonathan Norris, VP of Airbus’ cabin design office. "If he can’t charge, you can’t sell connectivity.”
Power To The People
“There has to be a finite end as to how much electrical power can be generated on an aircraft,” explains Norris. “One of the key things when we design an aircraft is understanding what the electrical load demand is from all the equipment.”
Subtract the juice necessary to power essential systems on the aircraft, and you’re left with what’s available for IFE and PEDs. When that IFE/PED demand increases, power “will be capped for the non-essentials to make sure…power is available for the systems that are actually controlling the aircraft,” says Norris.
If safety is the prime consideration, economy comes in a close second. It makes scant sense to “design a system to power a device…at every passenger seat simultaneously,” says Norris, especially in an age when fuel consumption dictates so many corporate decisions.
“The addition of weight to an airframe today can have a dramatic effect on fuel consumption,” says Luke Ribich, managing director of Avionics & Systems Integration Group (ASIG), a major in-seat STC/retrofit player. He says that’s where “design team expertise comes into play, knowing precisely how to minimize weight and optimally place in-seat power components.”
Weight aside, there’s another issue: just what is the demand for in-seat power in the passenger cabin, and from which areas does it emanate? Kevin Bremer, who manages Boeing’s Cabins Systems Technology Center, says studies indicate that “only 10-15% [of economy class passengers] plug in.” That means the available in-seat power, at least in the back of the aircraft, is limited. As for premium passengers sitting up front, carriers tend to allocate all they need.
“Say in first class you would want to give your high-paying customers 100% power,” he says. “There would be no system limitation on their ability to receive power.”
Bremer says power runs through a master control unit. The MCU has a limiter, “what’s called a ‘config’ module.” It determines how much power is fed from the MCU to the in-seat power system. The config module “will actually pick a certain power rating” and manage the system.
Much of that management is pegged to which passengers are fastest on the draw to plug in and power up, says Gary Weissel, VP and co-managing officer of consultant SH&E’s commercial and business aviation practice. “Let’s say that you have an airplane with 350 seats,” he says. “It’s an international airplane. There’s power access at all 350 seats. But there’s only enough power for 100 laptops. Basically the first 100 people to plug in their laptops are the ones that get power.” After the threshold has been crossed, no juice. “It will just show that the system at their seat, or at their outlet, is actually dead.”
Some carriers peg their product to high passenger expectations, touting the PED-friendly confines of their aircraft. A case-in-point is Virgin America. Its all-Airbus (A319 and A320) fleet sports “two outlets at every three person row,” says spokeswoman Abby Lunardini. As part of FAA’s certification process, Virgin America tested the in-seat power systems by operating 82 laptops, 10 DVD players and 10 electrical devices simultaneously.
“Each pair of outlets at every row can support a maximum of 225 watts per this certification,” she says. There’s enough onboard power for every outlet, on average, “to deliver 82 watts at any given time. We have found that this is an adequate amount of power to keep our guests charged while flying—whether [they’re] on their laptop, iPad or just charging their phone.”
Keegan says that on newer aircraft, such as the 787, power is managed on three tiers: 1) the seat group level, the traditional triplet of seats; 2) the column level, which divvies up the cabin vertically down the aisles; and 3) the overall aircraft level. He says these multiple layers of protection “prevent you from overloading the generators under certain limited conditions…say you’ve been dispatched with a generator out, or you’re under some other load-limiting condition.”
The emerging make-up of the consumer electronics market—combined with increased per-seat regulatory wattage allowances—means in-seat systems should continue to manage comfortably, Keegan says.
Based on roll-outs at the recent Consumer Electronics Show in Las Vegas, “I don’t think I’m stepping out on a limb to say…we’re not seeing as many laptops coming out,” he says. Instead, smaller, USB-rechargeable devices are the rage, devices with “very, very long battery life” that draw less power than their predecessors.

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