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View Full Version : UWB kills TCAS?


Self Loading Freight
2nd Sep 2002, 10:29
From the Times today, http://www.timesonline.co.uk/article/0,,2-401104,00.html

"The Civil Aviation Authority, Britain’s air safety regulator, said that portable electronic devices such as laptops and personal organisers might have to be prohibited because of the risks posed by ultra wideband (UWB).

Tests on Boeing 737 and 747 aircraft by Nasa and United Airlines in California found that UWB devices “knocked out” the collision-avoidance system, which warns the pilot of converging aircraft, and the instrument landing system that guides aircraft to runways in bad weather. UWB may also interfere with air traffic control systems that rely on satellite signals. "

Has anyone been involved in UWB avionics testing here? I want to follow this story up: it seems to be based on a story in Aviation Now in June which seems to say the testing was rather ad-hoc (they had to turn the power up to many times the FCC limits for UWB, for example), but so far I haven't found the original research online and NASA is still asleep...

R

av8boy
5th Sep 2002, 05:28
I read something about this a few weeks ago. I believe it was Aviation Week. I'll see if I can dredge up the details...

As I recall (and I'm doing this from memory), there was a problem with UWB and avionics. What caught my attention was that it seemed to be localized on the flight deck. This is to say, that it wasn't so much a problem with an antenna on the fuselage being mucked with as it was direct interference with electronics in the front of the airplane. The reason this stuck in my head was that the article suggested that the only way to protect the flight deck from interference generated in the cabin would be to shield all windows and cabin doors--this because UWB radiation was apparently leaving the cabin via these routes, reflecting off of other, external parts of the airframe, and entering the flight deck from the outside. I'm no electrical engineer, but my first thought was that it might be easier to shield the flight deck than the cabin, but hey, what the heck do I know...

If I find the article I'll check my story. Of course, I welcome correction from those more knowledgeable than myself in this area.

Dave

Self Loading Freight
5th Sep 2002, 10:55
Thanks, Dave -- I found the article, and have emailed the researcher. Who hasn't emailed me back, but they're due to give a paper to a conference on the subject in October...

If it's not UWB, it'll be Zigbee or one of the other new mass market wireless protocols. An intractable problem!

R

Eboy
10th Sep 2002, 06:44
I'd like to see the original study also. Aviation Week shows them sticking UWB devices in the aircraft nose. Not a typical scenario. Any radio frequency device cranked up with enough power will cause interference. But, for now, just keep transmitters turned off in the cabin, including UWB (when deployed commercially) and Bluetooth, as is done now with cellphones, etc. Don't need UWB to use a laptop stand-alone.

I see a significant amount of text pager use in flight. But, hey, if you are not going to enforce the seat belt sign and 2-bag carryon rule, don't expect a lot of discipline elsewhere.

Consider placing a handheld spectrum analyzer on each plane, and the flight attendants can carry it up and down the aisle and sweep for unwanted transmitted signals when doing seat belt checks. Or, for covert monitoring, a Yagi antenna could be mounted to a bulkhead, and connected to a spectrum analyzer in the same cabinet the video player is. Less than $5000 per plane.

Self Loading Freight
12th Sep 2002, 06:41
Eboy--

I'm at the Intel Developer Forum in San Jose at the moment, and went to a Meet The Engineers bash this evening. Over the sushi and Sierra Nevada Pale Ale (where did it all go wrong?), I bumped into one Jeffrey Schiffer who chairs the Bluetooth Aviation working group. I asked him about the UWB report from Langley, and he'd seen it... I think it's fair to say that he didn't see it as at all significant, for the reasons you said before -- the power levels and positioning were very unlikely to be typical of any practical use of UWB.

He also added some interesting asides: the Bluetooth Aviation group had done a lot of research and testing, and the JAA now considered Bluetooth safe to use in flight. And Lufthansa has said that on average at least one mobile phone is on during every flight they make.

Interesting chap. He designed the audio modulator used on the LEM, so when Armstrong said "That's one small step..." the words came through Schiffer's bits. I guess that counts as mission critical...

R