Lear35pilot From United States of America, joined Sep 2000, 41 posts, RR: 0 Posted (9 years 1 month 1 week 1 day 1 hour ago) and read 7468 times:
I recently took an American Eagle flight from LGA to DCA on an Embraer 135. During the short flight, a passenger's cell phone began to ring, and continued to ring at least 20-25 times while at our cruising altitude of 21000 feet. The phone was in the overhead compartment, above the owner's seat, who did not acknowledge the ring until the flight attendant approached him, and urgently requested him to turn it off. The owner of the phone appeared to be a foreign national of middle eastern decent. While I am not trying to categorize any ethnic or religous group unfairly, my immediate thought centered around the use of a cell phone for detonating an explosive devise (similar to what happenned in Madrid and London on their mass transit systems). I was also quite surprised that the phone was able to receive a call at a fairly high altitude.
Does anyone have any background on cell phone technology, its affect on navigation controls during flight, and if it could be used as a detonation trigger? Again, I am not trying to paint any group as terrorists. I am more interested in understanding its potential affect on in-flight operations.
Starlionblue From Greenland, joined Feb 2004, 17056 posts, RR: 67
Reply 1, posted (9 years 1 month 1 week 1 day 1 hour ago) and read 7456 times:
Well I have several points.
If you wanted to use a cell to detonate a device, why would you let it ring? The signal is supposed to go the other way. But yes of course you can use it as a trigger. Just have a cellphone receiver wired to a bomb. When the receiver gets a call or an SMS with a certain code, boom.
As for navigational control. Yes there is evidence that electronics have affected flight systems. However there is no evidence to suggest any dangerous situation has occured. If there was, you can bet planes would have cellphone detectors installed.
As one pilot I spoke to put it: "A couple of cellphones won't do anything. If all the pax had their cellphones on and talked at the same time maybe, but even then the chance of affecting onboard systems is pretty remote."
"There are no stupid questions, but there are a lot of inquisitive idiots."
Mtnmanmakalu From Ireland, joined Nov 2004, 515 posts, RR: 3
Reply 2, posted (9 years 1 month 1 week 1 day 1 hour ago) and read 7445 times:
I have had a pilot call me and have me go to the cabin and check for a cell phone on an A320 during flight as they were getting interference on the "glass panel" affecting their gauges... I went to the cabin and found a PAX on his cell phone playing a game. The phone did not have an A/C mode and I had him turn it off... I then contacted the flight deck and the interference had stopped- the proof that it can happen and I have seen it myself!!
As for using a phone at cruise (35,000 feet), the cell tower signals DO NOT reach that high to even use your phone, although the phone still transmits a signal which causes the interference...
Iakobos From Belgium, joined Aug 2003, 3313 posts, RR: 35
Reply 3, posted (9 years 1 month 1 week 1 day ago) and read 7399 times:
A subject addressed at length in previous threads.
Cell communication can indeed tale place at ANY altitude, under certain conditions, the higher the less likely, except for cellular system(s) intended for air usage.
DrDeke From United States of America, joined Jun 2005, 830 posts, RR: 0
Reply 4, posted (9 years 1 month 1 week 23 hours ago) and read 7392 times:
Quote: As for using a phone at cruise (35,000 feet), the cell tower signals DO NOT reach that high to even use your phone, although the phone still transmits a signal which causes the interference...
That is incorrect. All current cell phones (AMPS, GSM, CDMA, iDEN, "TDMA" (IS-54/136), etc...) wait until they lock onto a signal from a tower before powering up their transmitters.
There are several reasons for this mode of operation. For one thing, a multiband phone doesn't know which band(s) are in use in the regulatory zone in which the phone is located. By waiting to receive a signal before transmitting, the phone prevents itself from transmitting on frequencies which are not licensed for cellular use in certain locations.
Thirty five thousand feet is only ~6.6 miles assuming you are more or less on top of the transmitting cell tower, which is a perfectly feasible distance for a cell phone signal to travel, especially given that there will not be any obstructions between the phone and the tower other than the airplane itself. There are other technical reasons why your phone might not work well at altitude, and why using your phone at altitude is detrimental to the operation of the cellular network, but the problem is not that you are too far away to receive a signal.
If you don't want it known, don't say it on a phone.
Squirrel83 From , joined Dec 1969, posts, RR:
Reply 5, posted (9 years 1 month 1 week 23 hours ago) and read 7382 times:
Quoting Lear35pilot (Thread starter): I was also quite surprised that the phone was able to receive a call at a fairly high altitude
I know back in 2001 I was flying to LAX-PVR on AS MD80 I was bored so i pulled out my handy and realized that it turned on in my pocket and me being curious decided to dial a number and it started ringing, after the answer machine picked up I hung up and shut off the phone, we were at cruising altitude, and not sure the location but somewhere over Mexico. Although it was a bad analog connection, I was surprised it even worked, and back then I was surprised that it even worked at PVR.
I have to say another time in EWR that I did start using my handy after we were on the ground and I could hear ATC in the background, that fraked me out a little so I just hung up and waited till I was in the jetway before I used my handy again.
RobertS975 From United States of America, joined Aug 2005, 943 posts, RR: 0
Reply 6, posted (9 years 1 month 1 week 23 hours ago) and read 7380 times:
I have turned on my cell phone several times while aboard private jet aircraft. At each time, I was greeted with "No Service" even when over large US metropolitan areas. Now, I have read (and cannot vouch for its accuracy) that cell phones are programmed to indicate "No Service" if they see too many cell towers.
Mtnmanmakalu From Ireland, joined Nov 2004, 515 posts, RR: 3
Reply 7, posted (9 years 1 month 1 week 23 hours ago) and read 7380 times:
Thanks Rusty for the clarification...
I was told the opposite by a Cingular Rep., but either way, like you said in a way, they don't work or won't work well at altitude- and it still CAN affect the communication/NAV system like I posted above....
If the FAA ban was lifted, from what I understand, all A/C would need a special device/antenna to make your cell phone work normally on-board at cruising altitude...