Aircraft and turning off your 'electronic devices'
Discussion
Eric Mc said:
IforB said:
7920ft for a statute mile, 9114 ft for a nautical mile.
Most airliners cruise between 36 and 41,000ft, around 6.8 to 7.7 statute miles up.
I assumed the GPS was geared for landlubbers and was using "ornery" miles.Most airliners cruise between 36 and 41,000ft, around 6.8 to 7.7 statute miles up.
Still pretty low whatver type of miles it was registering. It seems his GPS was reading the airpressure in the cabin. I didn't know they measured air pressure. I though they worked out altitude using the satellites.
Bushmaster said:
Eric Mc said:
IforB said:
7920ft for a statute mile, 9114 ft for a nautical mile.
Most airliners cruise between 36 and 41,000ft, around 6.8 to 7.7 statute miles up.
I assumed the GPS was geared for landlubbers and was using "ornery" miles.Most airliners cruise between 36 and 41,000ft, around 6.8 to 7.7 statute miles up.
Still pretty low whatver type of miles it was registering. It seems his GPS was reading the airpressure in the cabin. I didn't know they measured air pressure. I though they worked out altitude using the satellites.
The cell phone on board system used by us (Emirates) and I believe Ryan uses a pico cell on the aircraft, this then channels signals to ground stations if in range or satellite if not. This is deemed "safer" since a phone that has a cell in range will transmit at minimum power (to save battery power)thus reducing the risk of interference.
However....there really isn't a risk of interference, all aircraft wires are screened, critical systems are double screened, all are bonded to earth and the likelihood of establishing a loop that could transmit into the FBW system is nil.
Anyone who has travelled in the middle east has seen peple using their phone all the time there has never been an officially notified case of interference.
Most aircraft carried HF radios until very recently and most still do, the way that they were tuned was to send 25 watts of 10 meter wavelength power into a unbalanced load, this would generate enough power to physically move the aerial tuner to make the HF radio tune, it would move until the returned power equals zero meaning the aerial's electrical length was balanced. This power was essentially white noise and being deliberately sent into a unbalanced load, if anything was to disrupt an electrical system it would be this, but it was considered acceptable risk. At the other end of the radio spectrum the wx radar works at 25+KW of power, a broken waveguide releases all that power into the wild at the end of the aircraft, again no cases of this causing an accident ever, and since they were until recently on the end of a wagging disk, breakages were not unknown.
A cell phone produces 2.5w at max power. A computer none unless the wireless is turned on I guess.
However the issues of trying hand them off from system to system and to bill customers for their phonecalls made at 30 thousand feet were horrendous, they could be on multiple systems even carriers. The interference "risk" was very convenient.
However....there really isn't a risk of interference, all aircraft wires are screened, critical systems are double screened, all are bonded to earth and the likelihood of establishing a loop that could transmit into the FBW system is nil.
Anyone who has travelled in the middle east has seen peple using their phone all the time there has never been an officially notified case of interference.
Most aircraft carried HF radios until very recently and most still do, the way that they were tuned was to send 25 watts of 10 meter wavelength power into a unbalanced load, this would generate enough power to physically move the aerial tuner to make the HF radio tune, it would move until the returned power equals zero meaning the aerial's electrical length was balanced. This power was essentially white noise and being deliberately sent into a unbalanced load, if anything was to disrupt an electrical system it would be this, but it was considered acceptable risk. At the other end of the radio spectrum the wx radar works at 25+KW of power, a broken waveguide releases all that power into the wild at the end of the aircraft, again no cases of this causing an accident ever, and since they were until recently on the end of a wagging disk, breakages were not unknown.
A cell phone produces 2.5w at max power. A computer none unless the wireless is turned on I guess.
However the issues of trying hand them off from system to system and to bill customers for their phonecalls made at 30 thousand feet were horrendous, they could be on multiple systems even carriers. The interference "risk" was very convenient.
IforB said:
Urban_Ninja said:
I can understand the bit about phones interfering.
but what the hell is the reason for turning a MP3 player or nintendo DS off, JUST when your taking off. If its ok for me to use it in flight its ok for me to use it during take off.
they dont interfere with anything cos they dont transmitt like a phone does. so why do it
#but what the hell is the reason for turning a MP3 player or nintendo DS off, JUST when your taking off. If its ok for me to use it in flight its ok for me to use it during take off.
they dont interfere with anything cos they dont transmitt like a phone does. so why do it
When you have ear phones on can you hear the PA for emergency announcements? No, you can't, so headphones off please.
I've had stewardesses be very stroppy about it, even when I just had them in one ear to accomodate their initial excuse as per your comment above. They CLAIM it's because it's an electronic device, but they won't listen to the physics that if it's non-transmitting it can't cause any issue. Jobsworths...both them and the muppets in the airlines that write over-the-top rules.
IforB said:
Being one of the two muppets up the front myself. I can confirm that you can ring and order a Chinese for the entire crew whilst on the approach, though that is on a nice clear night in a manky old turboprop with the only bit of "fly by wire" being the paperclip holding the Captain's trousers up..............
I wouldn't want to try that in anything designed by Airbus though.
I can also confirm that you can call from a fair bit up, as my old man has called me several times to inform me to set off to pick him up from the airfield.I wouldn't want to try that in anything designed by Airbus though.
Although this is in smaller twins, King Air, Golden Eagle and a few others of that size.
IforB said:
GPS does work out altitude by satellite, not by pressure altitude. With 4 visibile satellites it gives you a 3D fix.
I assume the chap with the GPS had something like this..https://buy.garmin.com/shop/shop.do?cID=145&pI...
..and was looking at the barometric readout rather than the GPS altitude. That being said, they obviously require a pressure setting to be input, which I doubt he had...so without a valid pressure setting, in a pressurised cabin the display might as well have said "Raspberry Ripple" for all the use it was..
eharding said:
IforB said:
GPS does work out altitude by satellite, not by pressure altitude. With 4 visibile satellites it gives you a 3D fix.
I assume the chap with the GPS had something like this..https://buy.garmin.com/shop/shop.do?cID=145&pI...
..and was looking at the barometric readout rather than the GPS altitude. That being said, they obviously require a pressure setting to be input, which I doubt he had...so without a valid pressure setting, in a pressurised cabin the display might as well have said "Raspberry Ripple" for all the use it was..
The default altitude is barometric (apparently it is more accurate?), but it also shows GPS altitude if you press the right buttons.
It is cool to upload the tracks into Google Earth and see where you flew over!
bobt said:
As this is petrol head forum and not a plane spotters or frequent flyers forum, how about the nonsense rule at a filling station. FFS. My car has six sparky plug things, a sparky generator/alternator thing, a sparky starter motor thing, and a whole load of sparly relays. In my compression ignition vehicles, I dont have spark plugs, but I have been known to have a very hot (red hot) turbo, and occasionally the brakes might get a tad warm. Now what is more likely to start a fire, one of the vehicle related spark or heat devices, or my little nokia ?
I had a long chat with a bloke who'd spent 18 months of his life testing the effects of four inch long sparks at filling stations. Never caused a problem.The info from the pump to the till is sent via a radio connection and the stations really don't like false readings on these.
havoc said:
IforB said:
Urban_Ninja said:
I can understand the bit about phones interfering.
but what the hell is the reason for turning a MP3 player or nintendo DS off, JUST when your taking off. If its ok for me to use it in flight its ok for me to use it during take off.
they dont interfere with anything cos they dont transmitt like a phone does. so why do it
#but what the hell is the reason for turning a MP3 player or nintendo DS off, JUST when your taking off. If its ok for me to use it in flight its ok for me to use it during take off.
they dont interfere with anything cos they dont transmitt like a phone does. so why do it
When you have ear phones on can you hear the PA for emergency announcements? No, you can't, so headphones off please.
I've had stewardesses be very stroppy about it, even when I just had them in one ear to accomodate their initial excuse as per your comment above. They CLAIM it's because it's an electronic device, but they won't listen to the physics that if it's non-transmitting it can't cause any issue. Jobsworths...both them and the muppets in the airlines that write over-the-top rules.
Cabin Crew are not there to debate physics with you, they are there to ensure your and all the other pax's safety. If the airline has a rule that says thou shalt not wear headphones whilst on approach, then the CC will enforce it. That is their job. They are not jobsworths, they do it because they don't have any choice. It isn't a rule by the way, it is law, when you are onboard an aircraft, the a/c commander is the boss, he delegates responsibility to the CC for issues like this.
Seriously, you are the type of passenger that makes me wish I was still flying cargo. If you started being a pr*ck like that with some of the CC I know, expect to have them get their own back. I know how they do it and frankly, you don't want to mess.
They do a very tough job and dealing with obnoxious passengers just makes it tougher. Some people are so unspeakably rude that I do wonder how more CC haven't been sent to prison for stabbing people through the head with a plastic fork.
Bushmaster said:
eharding said:
IforB said:
GPS does work out altitude by satellite, not by pressure altitude. With 4 visibile satellites it gives you a 3D fix.
I assume the chap with the GPS had something like this..https://buy.garmin.com/shop/shop.do?cID=145&pI...
..and was looking at the barometric readout rather than the GPS altitude. That being said, they obviously require a pressure setting to be input, which I doubt he had...so without a valid pressure setting, in a pressurised cabin the display might as well have said "Raspberry Ripple" for all the use it was..
The default altitude is barometric (apparently it is more accurate?), but it also shows GPS altitude if you press the right buttons.
It is cool to upload the tracks into Google Earth and see where you flew over!
IforB said:
Accurate? Not sure about that. Especially given that altitude is worked out by knowing the pressure at sea level. The barometric setting will probably default to 1013 Mb, thought the real setting maybe significantly different, so you might have a huge error. Something you won't have with a GPS altitude.
You can calibrate the altimeter by pressing a few other buttons. A calibrated barometric alimeter is significantly more accurate than a GPS altimeter.
IforB said:
That's fine, but you need to know the sea level pressure and since the dumbing down of the weather reports, you need to go looking for them.
For the sort of accuracy that a hill walker will need, GPS will be fine. I wouldn't want to do an approach in a hilly area using it though.
Perhaps rather fortunately for all concerned, I wasn't using my GPS to fly the plane! The pilots up front were doing that, with their (I assume) barometric altimeter. As regards sea level, fine, but this flight took off from a sea level airport on the South Atlantic coast, flew across a continent including a 20,000 foot mountain range, and eight hours later decended to another sea level airport on the equatorial Pacific coast, so the air pressure 'at sea level' would be a bit different throughout. I assume the crew obtains the atmospheric pressure of the destination airport prior to landing, but sadly they don't tend to share this level of detal with the paying cargo.For the sort of accuracy that a hill walker will need, GPS will be fine. I wouldn't want to do an approach in a hilly area using it though.
When we take off we use QNH, which is the sea level pressure at the airfield we are departing from.
Once we climb past transition altitude, we change to a standard setting of 1013 Millibars. This means that all of us are flying on the same setting. This means we are no longer flying at an altitude (above sea level) but at a flight level. (for example 36,000ft becomes FL360.)
When we are descending we will be given the QNH at the arrival field/area so that we can reset our altimeters and see what altitude we are at. This is necessary for terrain clearance.
If landing at a sea level airport, then the altimeters should read 0 on touchdown. If the airport is 100ft above sea level, then the altimeter should be reading 100 on landing.
Once we climb past transition altitude, we change to a standard setting of 1013 Millibars. This means that all of us are flying on the same setting. This means we are no longer flying at an altitude (above sea level) but at a flight level. (for example 36,000ft becomes FL360.)
When we are descending we will be given the QNH at the arrival field/area so that we can reset our altimeters and see what altitude we are at. This is necessary for terrain clearance.
If landing at a sea level airport, then the altimeters should read 0 on touchdown. If the airport is 100ft above sea level, then the altimeter should be reading 100 on landing.
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