Airborne Satellite Weather Data

Objective

A pilot normally obtains a weather briefing before departure and for most short flight this is sufficient. However, on a long flight, airborne weather updates enable a diversion to be executed early, rather than flying all the way to the destination and discovering it is fogged-in, and having to proceed to the alternate on reserve fuel, with any problem at the alternate resulting in an emergency. In parts of Europe, the alternate options are poor, often with the only realistic option not having avgas or even Customs. Often, the alternate is some dump where you do not want to be at all. Most modern airlines have this facility using ACARS and the benefits are obvious.

In the USA there are satellite based services which carry aviation weather but Europe is way behind. One German company, MT, offers a service based around their own data servers and their own custom made tablet computer

but this is a very expensive product. Avidyne are now offering the MLX770 system

which is also very expensive unless you already have a compatible MFD, and even then it costs a lot for the rest of the system and its installation, plus the satellite data subscription. These products offer a weather radar image which is geo-referenced around the aircraft position, which is a nice feature.

The objective of this project was to find out whether a free service to individual pilots, avoiding all licensing issues, can be configured that provides METARs, TAFs, and perhaps basic weather radar, using a satellite phone linked to a tablet computer or a PDA.

Where does the weather data come from?

In Europe, weather data is commercially marketed, can be very expensive if you want near real-time, and any commercial product using it has to license it. Worldwide METARs/TAFs have been freely available for some years (mainly from the USA) and these are redistributed all over the internet to such an extent that few care about any copyright anymore, but radar data has only recently come out on the internet, in small sanitised doses which (like share prices) are time-delayed to limit its usefulness. Meteox offers an image for much of Europe but only via a page filled with advertisements. Sferics data (lightning discharges) is now available free for all of Europe from several websites, collected by a network of volunteers feeding data into a server which plots it geographically. So, for personal use, there is enough "out there" to be useful.

Which satellite operator?

The principal networks are Globalstar, Immarsat, Iridium, and Thuraya. All the satelline phone networks offer both voice and data, and most offer both PAYG and contract tariffs. Iridium is probably the most commonly used network for commercial data in both aviation and ground based applications such as vehicle tracking; both MT and Avidyne above use it. Iridium went bust some years ago but are back up and running, with a network comprising of a large number of low earth orbit satellites. However, its basic data rate is just 2.4k bits/sec (around 200 bytes/sec) which costs £2/minute and its phones are £1000+. Iridium is evidently aware of the light aircraft market but at a hefty price.

Thuraya was chosen for this project, for its compact phones, best value for money, and a good data rate (9.6k dial-up or ~50k on GPRS). Thuraya is based in UAE, has cherry-picked the market by not providing worldwide coverage but instead covering a large area centred on the Middle East

and is aggressively targeting the developing world with tariffs below traditional GSM rates. Their main satellite (Thuraya 2) is geostationary at 28 degrees East and therefore lies in the south easterly direction from the perspective of a European user. The phones run at 1525-1660MHz. Some technical information on Thuraya and others is here. The Wikipedia entry is here.

Thuraya does mention aviation applications here but this leads to a dead link and I have not found anybody actually doing it.

Unfortunately, Thuraya do themselves no favours with their "customer service" which is way short of what one would expect to be supporting such an executive / professional market product. They take anything up to several weeks to reply to an email and many are never replied to, and faxes are totally ignored. However, they do monitor various internet forums for any mention of Thuraya and contact the poster if they don't like something! It is also easy to find web reports from mountaineering expeditions who had a lot of Thuraya kit and found it barely usable for certain functions, notably SMS and the POP email function (this project uses neither of these features). I expect that this, as well as the lack of U.S. coverage, is why everybody offering "professional" products/services has gone to Iridium despite the much higher cost.

Thuraya Costs

The following cost examples are as at August 2008 and were supplied by AST Systems who were extremely helpful in the supply of loan equipment for this project.

Thuraya costs are not on their website and - as is normal in mobile telecomms roaming charges - are difficult to establish. There is a complex matrix of tariffs, made worse - on contract SIMs - by the rate varying according to the caller's location. On the two PAYG tariffs ("Classic" and "ECO") the caller's location does not affect the tariff. Given the context of this article is internet data, voice calls are largely ignored but, in general, voice calls to land numbers cost around $1.50/minute and can be as low at $0.20/minute on a Thuraya-Thuraya voice call on the "ECO" PAYG SIM. However, voice calls to Thuraya numbers can be eye-wateringly expensive - I have just called one from my Virgin UK PAYG mobile and it is £6/minute.

The data call charge is $0.99/minute for dial-up data, or $5/MB (charged in units of $0.05) for GPRS and amazingly this applies to both PAYG (the "Classic" SIM) and contract. On PAYG these rates are independent of the caller's location. The "ECO" SIM offers a slightly lower dial-up rate of $0.76/minute but this tariff is believed to be blocked when over water.

The three Thuraya phones are priced as follows: 7100 £380 SO-2510 £330 SG-2520 £575

The other costs are as follows:

PAYG

GPRS Activation fee: $20 one-off charge

The tariff chosen was the "Classic" SIM which is the main PAYG product. The prepaid packs (scratch cards) come in various sizes up to $160. There is a big catch: any remaining balance on the SIM is confiscated at the end of a time period which for the $160 pack is 12 months.

If your credit runs out, the phone is de-activated and you have to pay a re-activation fee which varies according to how long the credit has been lapsed for.

Top-up options: There are traditional scratch cards one can buy from the dealer, and there is a 3rd party topup facility operated by FoneRecharge who offer both a topup website and a means of topping up using the phone; the latter is a free call so it can be used even when the credit has run out. It is also possible to telephone a Thuraya dealer who will take your credit card details, scratch a card, and give you the magic number.

CONTRACT

Activation fee: $20 one-off charge

Monthly payment: $20 - this gives you voice only and does not enable GPRS or dial-up data.

Additional monthly payment to enable dial-up data: $5

Additional monthly payment to enable GPRS data:
$20/month (5.12MB GPRS data included, $0.05/10k thereafter)
$55/month (15.36MB GPRS data included, $0.05/10k thereafter)
$105/month (35.84MB GPRS data included, $0.05/10k thereafter)

PAYG or Contract?

With traditional GSM, the choice between PAYG and Contract depends on one's usage, because contract rates come with various benefits e.g. lower call rates, monthly call and data allowances, extended geographical coverage, and reduced administration because the account cannot run out and does not need to be topped up. Some networks (e.g. Virgin) blur the difference by offering a PAYG product with automatic (direct debit) topup which gives "contract" geographical coverage without the administrative burden.

With Thuraya satellite calls, the Contract option - suprisingly - does not offer cheaper calls, free calling time, or subsidised handsets. It has just two benefits: the ability (on dual-mode phones such as the SG-2520) to make outgoing GSM calls, and easier administration through the elimination of scratch cards (though this one is mitigated by the 3rd party FoneRecharge facility) and the provision of usage statements (no way to find out where the money is going on PAYG other than by doing a 151-call balance enquiry before/after a call). However, the contract rental for the basic dial-up data functionality costs $25/month i.e. $300/year which is a lot to pay for not having to buy a scratch card once a year. The rental for both dial-up data and GPRS functionality is even more - $540/year. The GPRS-inclusive contract option comes with some included data which is cheaper than the standard $5/MB rate but this has no value when you consider the monthly payment as well. Contract would make sense for heavy users and that is about it.

The phones are the same price regardless of PAYG or Contract. The prices shown above include various accessories but do not include car mounting kits, remote antennae, etc. In fact the reason why the 7100 (a refurbished price; they are no longer made) costs more than the new SO-2510 is because the usual accessories on it were priced separately.

For this application (airborne weather data) I believe PAYG offers the best value. The $160 scratch card, if purchased every year (as it must be because that's how long the money lasts for) is equivalent to a "contract rate" of $13.33/month which includes free calls worth $160 during that year. On GPRS, this is 32MB which would cover countless thousands of METARs/TAFs, and hundreds of weather radar images.

Built-in GPS - Necessary?

Thuraya phones contain a GPS receiver. The appearance, most likely intentional, is that a GPS position fix is mandatory to enable a call to be made. It is a fact - on some tariffs - that if you travel around, Thuraya bill you at different rates according to where the call was originated, so they are tracking your position somehow.While few users will care about being tracked (the privacy issue), it creates an operational uncertainty because the GPS receiver is usually unable to obtain a fix if the telephone is powered up while airborne.

The firmware design of any GPS receiver is to some extent a compromise: if the designer assumes that the phone is not moving (much) when switched on, it can be optimised to get a much faster fix. It appears that Thuraya have taken this option; their GPS gets a fix within seconds if not moving but is hopeless at speeds above slow traffic speeds.

Therefore, if Thuraya truly mandated a GPS fix for every call, this system would be useless in this application, and in fact would not work in most motor vehicle applications - yet they do sell car kits....

Fortunately, it's obvious from the most casual usage that GPS reception is not mandatory for making every call, and the phone works just fine without a GPS fix having been obtained for 2-3 days. You can use the phone indoors, where it has a Thuraya satellite view (e.g. horizontally through a window - in the UK, the Thuraya satellite is quite low on the horizon) but the building blocks any GPS satellite reception.

There is an occassional GPS fix requirement, indicated by the GPS icon on the phone flashing but nobody knows what triggers this. It it is definitely based on a straight time limit of 2-3 days since the last GPS fix, but given that the Thuraya satellite emits a large number of separately generated "spot beams", it is also possible that Thuraya enforce a new GPS fix if the phone's last GPS position is inconsistent with the spot beam it is now communicating on.

Thuraya were contacted (8/2008) for a clarification of their policy on this, but declined to comment citing confidentiality of system design information. Eventually they said that the system will mandate a new GPS fix every "8-24 hours" (the actual period appears to be 2-3 days) or if the user moves more than 100km (which is highly unlikely to be true since the spot beam diameter is about 450km and I have done much longer flights than that with it). I am trying to establish the limits of the GPS fix policy but the only sensible advice at this time is to obtain a brief GPS fix prior to any flight and leave the phone switched on for the duration of the flight.

The procedure to get a GPS fix appears to depend on whether the phone actually needs one:

If the satellite icon is flashing (and it will be if you haven't used the phone for a few days) it has to get a fix to work at all, and it will get one automatically as soon as it is switched on.

If the satellite icon is not flashing, it doesn't need a fix there and then. If you wish to force a GPS fix however, enter the GPS Fix menu and get the phone to obtain and display the GPS position - merely switching on the phone doesn't appear to do it. More information is under Operational Recommendations at the end of this article.

It is believed that a GPS fix is mandatory at the initial SIM card registration time following the new phone purchase - this is possible and isn't an issue. It's a good idea with any brand new GPS device to let it get a fix otherwise it can take ages (anything up to half an hour) to get one when you need one.

I discovered that the need for the GPS fix is tied to the physical phone. For example, if you obtain a GPS fix with one phone and then transfer the SIM card to another phone, the other phone will request a GPS fix. If you then transfer the SIM card to the original phone, that phone will request a GPS fix even though it had one only minutes before. One can only speculate as to the reason for this bizzare policy.

During internet research which I did to see if anybody else had come across these issues, I immediately found that half the world is making Thuraya interception equipment e.g. here. Since the GPS position - if available - is transmitted with every call, this is a great system for any country wanting to keep tabs on somebody, particularly in remote regions where there is no GSM coverage.

Which weather data display device?

For a portable solution, there are really only two possible display technologies: a traditional Windows based computer or a PDA.

The former would be a tablet or a convertible tablet/laptop; a normal laptop is normally impractical in the cockpit. I use the LS800 tablet computer modified with a solid state 32GB hard drive

A PDA is a more compact option; I use the HP 4700 PDA

and believe that a good 640x480 PDA could deliver the best solution in this case - due to its small size, low power and freedom from hard drive altitude dependencies. Unfortunately PDA software is unreliable and rarely seems to do the same thing on two consecutive days, and few PDAs can act as a USB controller so Bluetooth is the only practical method of connecting to a phone.

The new low cost EEE PC products should also work fine.

It's easy to end up with a cockpit full of gadgets and interconnecting cables and I have tried hard to avoid this. Obviously the fully installed and certified solution (Avidyne) achieves this but at a huge cost, and I doubt anybody will be installing an Avidyne MFD for weather data. Any low cost route involves the use of uncertified devices but these need to be portable, ar at least removable, and these take us back to the "messy cockpit" scenario. There are several approaches to alleviate the problem:

Bluetooth avoids the phone to display device interconnecting cable. So, a bluetooth phone whose battery lasts the flight duration avoids the need for any cable connection to it - it merely needs to be located where it can see the satellite.

For METARs/TAFs, the SG-2520 phone can itself act as a primitive web browser, though its sunlight readability is almost nil.

An rather different approach is to use an existing panel mounted MFD e.g. the KMD550 as the display device

Most MFDs have NTSC video inputs (for weather radar data) and the resolution should be adequate for this application. One would need a display device with a VGA (640x480) output (a suitable PDA would do) and a VGA to NTSC video converter. If the MFD's video input was accessible via a BNC connector (an easy job for an avionics shop) the rest of the equipment could be mounted in a "removable" manner. Unfortunately the MFD will not provide the interactive interface so the Windows display device would still need to be accessible if you need to e.g. select different data sources. The problem with this kind of approach is knowing where to stop.... a dedicated keypad for airport code entry perhaps? One could get a lot of clean functionality while still keeping to an installation which is "removable" and thus avoids certification issues but it could be a lot of work.

Obviously, most users would prefer to use something they are using already. I normally have the LS800 tablet computer running and to hand even if not referring to it, because I print off approach plates only for departure, destination, and alternate, and any others would be looked up on Jeppview running on the LS800. I did experiment with PDAs extensively but found them too flimsy, both mechanically and bugs-wise.

A vital consideration is that the client display program should be a standard internet browser (Internet Explorer or Firefox). These are already provided and any departure from this generates a huge amount of software development work.

The Phone - Display Device Interconnection

The options are cable or wireless. The most common cable connection on phones is USB. For wireless, there is IRDA (not tested here because it requires line of sight and is generally unreliable) or Bluetooth.

For any Windows 2000/XP device, USB is straightforward. Unfortunately few PDAs (Windows Mobile / Pocket/PC) offer a USB controller function; all PDAs have a USB facility of some kind (for the hotsync feature) but most of them are USB slaves, not USB controllers.

Bluetooth is the method of choice and should enable the use of any Windows 2000/XP device, or any capable PDA.

Who to connect to for internet access?

One can obtain data in two ways: connecting to the internet (when any web-connected server is accessible, and either dial-up or GPRS can be used) or by dialling into a private modem (connecting you to a private data server, using dial-up only).

A private modem can support only one call at a time but a server on the internet has no real limit. However, connecting to a private modem is more efficient - it avoids the authentication/DHCP process (which you are paying for; about 15 seconds on a dial-up call), avoids various delays, and enables a chunk of data to be transferred in a call lasting just a few seconds. One could go a long way down this road and perhaps it would be worthwhile for a commercial service.

In this project, internet has been used, and this can be accessed via dial-up or GPRS.

On a WinXP PC, the dial-up connection is configured using the standard Windows Dial Up Networking function, where you enter the ISP's telephone number, login and password. Thuraya offers its own in-house dial-up ISP whose telephone number is 1722 (login and password are both blank); it connects in about 45 seconds and the billing starts then. Authentication and DHCP takes another 15 seconds or so. Alternatively, you can dial up your existing domestic ISP - if they offer a dial-up service; not all ADSL ISPs do and not all of those support incoming digital calls (satellite or GSM data calls are equivalent to V-110/ISDN) and not all of those have dial-in numbers which can be dialled from abroad. Finally, there is the option of dialling up one of the countless "free dialup" ISPs who make their money from the UK 0845 call termination commission; I tested Primax Internet and later Free Dialup. A satellite is effectively a "country" with its own country code; every call with a satellite phone is thus an international call and not all 0845 or similar numbers can be dialled from abroad. I don't see any point in using one of these "free" ISPs, other than as a backup for Thuraya's 1722 service.

GPRS is configured the same way as dial-up - it is treated as a "dial-up" connection under Windows - but the number dialled is *99# . The connection time on GPRS is much faster than dial-up: around 5 seconds followed by another 10 seconds for DHCP. Delays should not matter much on GPRS because you pay only for the data, but you do pay for the DHCP part. The quality of the GPRS service is much more variable than with dial-up, in both the number of failed connection attempts and the data rate actually achieved.

Satellite Antenna Options

Satellite internet is big business, in both high-end sailing and high-end (jet) aviation. There is a large choice of roor-mounted antennae such as these but it proved difficult to find out whether any of them have actually been tested with Thuraya. In principle any Iridium antenna should be OK because the frequencies are nearly identical. One needs a dual-connector (satellite and GPS) antenna since the satellite phone also contains a GPS receiver. At time of writing (10/2008) I am still trying to check out what kind of "approved data" package these come with.

A rooftop antenna is without question the best technical solution which avoids the "blind spot" of flying directly away from the satellite in an aircraft which has a metal roof and no rear window, but it needs the phone to be mounted in a car holder such as this one

(the above is the SatTrans product; there are a few others) because there is no other practical way of connecting to its specialised antenna and power connectors and this, together with the installation certification, makes it into a significant avionics job. The car holder will obviously not come with "approved data" for an aircraft installation so it would need to be approved by a Design Authority (FAA DER or EASA as appropriate, which could prove impossible), or alternatively it needs to be installed in a removable fashion, with the antenna and power cables passing through a connector so the car holder can be removed when the aircraft goes in for maintenance. Additional work results from the satellite antenna having to be at least (roughly) 1m away from any other L-band (GPS, transponder, DME) antennae and these may need relocation which can be a lot of work. IFR GPS instalations are likely to require retesting for interference. I have investigated the remote antenna option for myself and while - being N-reg - the paperwork was not a big issue, I would have had to move one VHF (COM2) antenna from the roof to the underside.

This project concentrates on utilising the phone as it comes, with its internal antenna, and fortunately this works well and should be acceptable to a much wider user base.

Phone Tests

Equipment tested in this article was kindly loaned by AST Systems in the UK; the SG-2520 phone was eventually purchased.

The airborne tests were done in a 2002 Socata TB20GT aircraft

which has a maximum level flight speed of 165kt but 220kt+ can be achieved (for phone test purposes) by descending with a tailwind.

All satellite phones have a common feature: An uninterrupted line of sight to the satellite (which lies roughly to the South East of the UK) is mandatory, and any thick or conductive object, including one's head or body, will block the signal. The phone is thus virtually useless in a moving road vehicle unless one is driving in very flat country with no trees, houses, hills or any other obstructions.

The phones have an extendable antenna which pulls out by about 100mm. It is recommended that the antenna points towards the satellite but in practice this is not important, and would make usage for voice calls rather awkward! It works fine with the antenna being vertical.

Various scare stories have been circulating concerning Doppler effects, allegedly rendering satellite phones unusable in aircraft. In this test, ground speeds up to 185kt (213mph) were tested, on various headings deliberately chosen to present the best and worst Doppler shift scenarios, and no effects whatsoever were noted. 185kt adequately addresses the piston engined aircraft scene; turboprops can reach 350kt but being pressurised they also have much smaller windows and the phone position will be all the more critical.

The first test was done with a now discontinued but still very popular - and widely available as a refurbished unit - Hughes 7100 satellite phone

Website data sheet manual

The 7100 supports dial-up data only, no GPRS. The connection to the phone is cable only; no bluetooth.

The phone worked perfectly. The claimed dial-up data rate of 9600 baud (roughly 1000 bytes/second) was readily achieved, with variations of 700-1300 depending on how strong the signal was.

Actual internet access is satisfactory - as fast as one can expect at 1000 bytes/second. The dial-up phase takes around 45 seconds, after which the billing starts, followed by a 15 second period for authentication and DHCP IP allocation.

The 7100 is a good solid reliable phone, with working firmware, no gimmicks (e.g. a camera), the best in the class battery life (measured at around 24hrs standby with no calls made), good dial-up data performance, a sunlight readable display, and lowest purchase cost. It has the best GPS receiver of the phones tested; the only one which is capable of getting a fix in a moving aircraft (takes a few minutes) and like the others it can send the GPS position as a text (SMS) message.

Unlike the later (bug-ridden) Thuraya phones, the 7100 hangs up within a few seconds of receiving the hang-up command from the PC.

Its drawbacks are: no GPRS, no bluetooth, and a data cable whose phone end is easily disconnected through movement.

This phone would be ideal for a fixed rooftop-antenna installation because this sidesteps the connection and powering issues. However, the lack of bluetooth unavoidably means having a data cable to the display device - unless one connected it to an RS232-bluetooth transceiver module... This phone would also be my choice if I wanted a satellite phone for what most people would want one for: making phone calls!

For technical readers: the data interface on the phone itself is plain old RS232 and the phone presents a standard-ish Hayes modem port supporting the usual AT commands. It should therefore work with any computer device which can drive a Hayes modem. Two cables are available: RS232 or USB. The USB cable is merely a USB to RS232 converter (based on the common PL2303 USB-serial chip used in most USB-serial products) which requires the installation of a driver (supplied on a CD) on the computer; the driver creates a virtual COM port which is normally the first unused COM port number (e.g. COM6). However, as with most Prolific-chip based USB-RS232 converters, the COM port # will change if you plug this converter into different USB ports on the same PC.

The 7100 was manufactured by Hughes. The remaining Thuraya phones are made in the Far East.

The next test was done with the Thuraya SO-2510 phone

Website

This supports both dial-up and GPRS data.

The tests with this phone were not very successful.

The GPRS connection did deliver the claimed 60k bits/sec download speed when it connected, but it did not connect reliably. A good connection was obtained about 10% of the time, and it never lasted for more than a few minutes. The rest of the time, the connection failed in various ways, from not connecting at all following the standard GPRS *99# dial command, to connecting OK but with massive packet loss which was so bad that even the initial DHCP operation would fail so no IP was allocated.

The dial-up connection worked fine but the data rate was about 600 bytes/sec i.e. about half of what the 7100 delivered. The data rate difference was verified several times by swapping the same SIM card between the two phones and running both in the same position, with the antennae fully extended, etc, on the ground under a blue sky with a perfect view of the satellite.

Accordingly, no further tests were done.

The final test was done with Thuraya's top model; the SG-2520 phone

Website data sheet

This is Thuraya's most modern phone which supports both dial-up and GPRS data, and connects to the computer using USB or bluetooth. It was eventually purchased and tested extensively.

Satellite reception is the best of the three phones tested, with a strong signal obtained through most double glazed windows. The SG-2520 supports both GSM and satellite, and Thuraya have roaming agreements with most GSM networks so the SIM card does not need to be changed. The phone is also SIM-locked to Thuraya. The GSM function works on PAYG but a Contract SIM is required to make outgoing calls.

Dial-up works fine, at close to the 9.6k advertised speed; ~1000 bytes/second. The connection suceeds very reliably.

GPRS works fine, at close to the 60k advertised speed; ~5000 bytes/second. The connection and authentication happen very fast (10-15 seconds) but with poor reliability which can be as low as 10%.

Bluetooth eliminates the data cable which, together with the fact that most flights are done on more or less the same aircraft heading all the way, enables a simple system whereby the phone is attached (with e.g. velcro) to one aircraft window when flying from A to B, and then moved to the opposite window when flying back.

Bluetooth connects flawlessly to the LS800 WinXP tablet computer and to another WinXP laptop, delivering dial-up and GPRS data modes, and fax. I was unable to get my HP4700 PDA to work - it found the phone and paired with it, but reported that the phone has no services it can use; I tried both FAX and DUN profiles. A more modern PDA might work.

The Bluetooth connection requires no driver installation on a PC which has Bluetooth support already. In the phone, it can be configured for "DUN" (dial-up networking) or "FAX", and both work equally for internet access. Most curiously, the FAX profile resulted in a ~15% higher data rate on dial-up, and ~5% on GPRS... but the DUN profile has better error recovery in the "hang up a lost connection and redial" scenario which is pretty common.

The Bluetooth FAX profile also works with Winfax. Fax appears to have little use while airborne but could be useful on the ground (for the usual reasons for which fax is handy in aviation; airport PPR being a common one) because not all terrestrial GSM networks support fax. I have Winfax already, on a GSM-enabled laptop, so this feature costs nothing extra to have. I suspect that nowadays most people - having an internet connection - will use an email2fax service instead. I did not test the phone with WinXP's built-in fax function, which definitely does not work with GSM fax modems.

The USB connection works fine. It requires the installation of a large software package on the PC which installs the USB drivers as well as Microsoft's Active Sync; fortunately the latter piece of bloat-ware can be uninstalled afterwards. The phone's USB interface can be configured to look like an active-sync device, or a modem. Both modes worked fine but active-sync is pointless in this application. The USB cable connector on the phone is far from sturdy but is fine for occassional use.

The phone has a 5V charging/power connector which draws a maximum of 1A. The Thuraya car cigar lighter charger accepts 11-32V input so would be usable in 28V aircraft. The input current was measured at 150mA at 28V, 350mA at 14V

Of the three phones tested, the SG-2520 was chosen for further work, largely because its Bluetooth function so much simplifies its usage in this specific application. However, it has some drawbacks:

The Bluetooth enable status is not saved at power-down and the phone powers up with Bluetooth OFF. This firmware bug means you have to turn on Bluetooth after every power-up (if you are using Bluetooth).

On dial-up, there is a serious bug: disconnecting the network connection on the PC does not terminate the call, and this happens with both cable and bluetooth connections. The phone appears to ignore the standard modem disconnect commands. The phone sometimes hangs up by itself after a minute or two ($1-$2 later) but really needs the user to terminate the call manually using the phone's keypad. This bug may be present on GPRS but fortunately GPRS has no pressing need for a timely disconnection because you pay only for data transferred.

Occassionally, the phone crashes and a power-down is necessary. This rarely happens in normal data usage but the phone can crash so thoroughly when bluetooth device pairing has failed, or after a fax has been sent, that its battery needs to be temporarily removed. I would not recommend mixing faxes and internet access without an intervening power-down. Bluetooth devices everywhere tend to be buggy and the advice for any bluetooth connection is: when it works, leave it alone! The SG-2520 bluetooth compliance can be checked here (search for "Thuraya") although I cannot see anything much there.

While merely enabling Bluetooth does not affect the phone's battery life, the act of dialling out (dial-up or GPRS) stops the phone's screen saver operating (until the next power-down) which is a plus because you can see what it is doing, but it reduces the battery life from ~20 hours down to ~3.5 hours - without even making any calls! One can adjust the screen brightness downwards but, due to another bug, an active bluetooth connection re-illuminates the screen at maximum brightness and leaves it there even if the other bluetooth device is subsequently turned off. Paradoxically, therefore, while bluetooth does away with the data cable, it may force the DC power/charging lead to be connected. Fortunately the bigger battery is only £30 and is highly recommended - it increases the 3.5 hour life to a measured 7 hours.

The colour screen is only just about visible in sunlight.

The built-in miniature 1024x768 camera can store images to the phone's SD card. The files can be accessed via active-sync or by removing the card. The camera is of exceptionally poor quality - example.

The GPS receiver almost universally fails to get a fix if switched on in an already moving aircraft. It also contains obvious (if irrelevant) bugs: the speed and altitude are about 3x too high. There is also uncertainty over when the GPS receiver actually gets enabled and starts looking for satellites - sure enough it gets enabled if one selects the GPS menu and requests a fix, although presumably it must also get activated at other times e.g. when making calls. This selective activation could cause problems if a GPS fix was at some point mandatory, because it cannot be obtained once you are moving.

Which weather website to access?

There are many websites and pilots have their own preferences. However, for airborne data, one can split up the requirements into two categories:

1) Conditions at the destination, alternate and potential diversions (METARs, TAFs)

2) Tactical data (weather radar, sferics)

METARs and TAFs are simple textual downloads e.g.

METAR
METAR EGKK 160850Z 16008KT 130V200 9999 FEW016 SCT022 17/13 Q1009=
METAR EGKK 160820Z 14007KT 120V190 9999 SCT020 17/13 Q1009=
METAR EGKK 160750Z 14008KT 9999 FEW048 16/13 Q1009=
METAR EGKK 160720Z 13007KT 110V170 9999 FEW046 16/12 Q1010=

TAF
TAF EGKK 160602Z 160716 14007KT 9999 SCT040=
TAF EGKK 160412Z 161212 17010KT 9999 SCT040 TEMPO 2306 7000 RA BKN012 PROB40 TEMPO 0205 17015G25KT 3000 RADZ BKN006 BECMG 0508 26008KT=

Weather radar images are more of a problem because of their size. Moreover, most websites providing this data are packed with bandwidth-wasting junk and the free ones e.g. Meteox contain advertisements which are often huge Flash/Active-X feeds. Even if the bandwidth was not an issue, the surrounding material has to be displayed on the client browser and the pilot has to take some positive action (with a mouse/pen) to view the real information.

More complex websites, sometimes generating megabyte-plus images, are out of the question because of the limited bandwidth, cost of data, and the less-than-100% reliability of the connection.

It is highly desirable to get the data formatted so it fits onto the small-screen display device conveniently used in aviation applications.

The solution is a custom web proxy. This is just another website which is created with custom software running on a private server, which goes to the real website, strips off the redundant information, and returns the desired portion to the client. I am not aware of any legal issues with this provided the end product is not charged for. In reality, many ISPs run web proxies and Google would be out of business overnight if this mattered. The really important thing is that the proxy server should not hit the weather website at some ridiculous frequency because, at best, this loads up their server and, at worst, they might be running some security software which would regard this as a DOS (denial of service) attack and blacklist traffic from that IP.

A web proxy has been developed and is available here - shown below running on an 800x600 display device; the LS800:

This offers a METAR/TAF facility with periodic updates, several weather radar pages, and a sferics page. The server is a Unix PC running on the end of a 448k-uplink ADSL line so not capable of handling heavy traffic. The proxy server does not visit the websites it uses unless there is a request from the airborne client device - it does not generate any superfluous traffic.

The METAR/TAF page currently comes from Avbrief but if necessary can be changed in the web proxy software to use the common U.S. sources.

The main weather radar page comes from Meteox. Unfortunately the geographical coverage is more limited than the basemap suggests and the limits are not obvious.... N Italy is not covered, for example. [Work in progress: establish the radar coverage limits, by overlaying thousands of past images, and put them on the map image]

The Meteox image, shown here pixel for pixel

is about 60k but the background map is cached by any normal web browser and only the radar overlay is downloaded - this ranges from zero to around 20k on a really bad day.

On Thuraya GPRS, the radar image downloads in a few seconds and - if 20k - costs about $0.10 on GPRS which is peanuts. The total cost of making a connection, collecting a load of METARs/TAFs, and one Meteox radar image, is going to be around $0.20.

The proxy is expandable but any major work would need funding.

Phone and Client Device Configuration

The details are here. There isn't much to do to get a working system. Configure the phone for the Bluetooth profile, and configure a dial-up connection within Windows.

However, there is a reliability issue: satellite data - indeed all mobile data including GSM, GPRS, 3G - is nowhere near as reliable as your home ADSL. There are two separate aspects to this: failure to establish a connection, and a failure to detect (and redial) a broken connection. The first one is handled fine by the Windoze dialler which will just keep redialling until it gets a connection (specifically, until it gets an IP allocated; internet access is never actually checked). The second one is more tricky because the data link often breaks a long way upstream which is undetectable other than through the obvious lack of data. The solution is to use a different dialler to the default one; one that periodically (say, every 60 secs) pings some site and hangs up / redials on a ping failure. There are several such products on the market; mainly shareware. I have tried FlexibleSoft XP and HiDialer 2000 of which the first works a lot better. With these, you can configure an application to launch when the connection is made - in this case, the web browser with the web proxy URL as a parameter - and the end result is not only a big reduction in the amount of fiddling but also a largely automatic recovery from dropped connections.

"Executive Summary"

The system works satisfactorily and offers satellite weather data for an initial purchase cost of under £600, plus $160/year for the basic 12-month data package, plus the cost of a display device.

Thuraya does not deliver a rock solid 100% reliable solution which can be just switched on and left alone, and some user interaction is required to get it to work. However, given that one would be getting the data during the usually quiet enroute segment of a flight, the performance is acceptable.

Operational Recommendations

Phone location is important because a good signal is required for a reliable internet connection. The phone needs a direct unobstructed satellite view - in Europe the satellite will lie to the South East of you. It may be possible to get a good signal with the phone hanging in the centre of the cockpit e.g. between the two front seats but a far better location is right up against a window, oriented vertically. Self adhesive velcro is a suitable attachment method but a piece of insulating tape is just as good! Another simple and totally effective method is to make something with suction cups, and tape the phone to it

Ensure the phone is within your reach because it does occassionally need to be powered down/up to restore operation!

Following each power-up, one needs to enable Bluetooth in the phone, and one should also obtain a GPS fix before each flight:

1) Switch ON the phone when on the ground.

2) Enable Bluetooth in the phone (see Systems/Device Configuration) - this must be done because the phone powers up with Bluetooth=OFF.

3) Set the phone to display a GPS fix (under the Navigation menu).

4) Ensure the phone battery cannot go flat during the flight. At maximum display brightness (the only useful setting) the standard battery lasts for 3.5 hours and the extended battery last for 7 hours. If in doubt, plug in the car charger lead.

Interference with other avionics - other than the subdued noise one can hear in ANR headsets when there is an active GSM phone in the cockpit - has not been detected but I strongly recommend not having the phone switched on when flying any instrument approach.

Other Applications

Well, a phone is a phone and can be used for ... making phone calls! On the ground, in modern Europe, this use is likely to be limited because GSM coverage is nowadays very good. However, GSM reception is often poor in the countryside.

With the Bluetooth-equipped Lightspeed Zulu aviation headset it can even be used to make calls while airborne, for airport PPR, taxi booking, etc. I have tested it and it worked although for some reason the voice quality was poor.

And it makes a good emergency device; the ability to simply text your GPS position to somebody is pretty slick.

Being able to text while airborne enables you to let someone know accurately when you will be arriving. This is suprisingly useful.

You can send a text message to a Thuraya phone via the Thuraya website here. There used to be a general email-to-text facility but is now gone - unsuprisingly as it would have suffered massively from spam.

It makes a good enough fax modem which is not affected by a local GSM provider not supporting fax calls.

Thuraya data pricing is pretty good: the $5/MB tariff on Thuraya GPRS is 1/4 of what I pay to Vodafone, and 1/2 the cost of Virgin, for roaming data on GPRS/3G!!

This page last edited 5th December 2008

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