NoFlyZone

Someone would have to research whether that 10000 foot number is above sea level or above ground level. Both figures are used in flight, depending on the purpose. And, they could have forgotten to make the announcement, too.....

rkkwan

The 10,000 ft number is definitely about sea level. I pay special attention on the departing flight from SLC, and then again on both flights into and out of SLC on my way back. It's 10K above sea level, no question about that.

The "no electronics" duration between 10,000 and 4,226 ft at SLC and the time between 10,000 and 97 ft in Houston is significantly different. In fact, 10K is just about the height of the mountain ranges east of the city.

NoFlyZone

I decided to take 5 and research. First, came up with this nice and official FAA summary of the rule and the reasons behind it:
http://www.faa.gov/news/news_story.c...2005&date=0805

(just published last month ... I wonder if someone has been monitoring Fodor's!)

Boeing has a good article on the issue:

http://www.boeing.com/commercial/aer...interfere.html

The US government has held hearings on the matter:

http://www.house.gov/transportation/...20-00memo.html

Back to the issue at hand, The FAA regulation prohibits operation of certain devides during landing and takeoff phases of flight without stating an altitude (although that may be covered elsewhere but I did not search for that). FAA Advisory Circular (AC) 91.21-1 recommends that the use of personal electronic devices be prohibited during the takeoff and landing phases of flight below 10,000 feet.

Although not explicit, it can safely be concluded that the altitude is above ground level (or at least the level of the airport of concern). And that is the airline interpretation.

rkkwan

NFZ - Your post basically reinstated what we're talking here. You used the words "FAA... recommends", and "airline interpretation".

I think most readers will get the point Cassandra and I are trying to make here.

Cassandra

And tell me, please, whether anyone's implying that the "interference" threatened by these electronic devices is somehow changed by altitude per se? If so, how on earth does that happen -- frequency affected by barometric pressure, what?

Again: duh.

NoFlyZone

The "recommends" just above applies to the 10,000 foot number, which is not specifically in the regulation. More important, the links contain specific examples of interference.

Cassandra, it indeed has nothing to do with altitude, but rather to different navigational techniques and instruments used during landing/takeoff as compared to enroute flight.

Cassandra

NoFlyZone -- I got that. Just pointing out arbitrarinesses..... And the fact that the whole business of the actual altitude of the airport is irrelevant or should be.

NoFlyZone

You are correct, ma'am.