Beware! possible smartphone interference with panel-mounted GPS!

Your iPhone may interfere with your GPS!

It has come to my attention that a significant number of pilots may be experiencing smartphone interference with their GPS avionics equipment. The iPhone in particular may cause loss of GPS signal reception for 10-15 seconds at a time or longer. At least one club airplane I’m aware of has experienced repeated instances of signal loss reported by various members carrying iPhones, “but the problem goes away when pilots leave their iPhones on the ground.” The pros at my avionics shop (at the opposite end of the country) have also heard numerous such reports.

According to my CFI friend and Apple technology guru, Patrick, the issue can arise whenever your smartphone is left on in flight; although you might not be texting or calling, the phone continually transmits cellular queries to sustain ongoing signal access. Patrick says that these transmissions become stronger the farther you are from a cell tower. The IMPORTANT bottom line is that if you experience loss of GPS navigational signal aloft, the first thing to check is that your smartphone is off.

This growing concern explains why it is truly important to:

  1. Turn off portable electronic devices prior to flight, particularly those like smartphones that continually transmit, especially when flying under difficult navigational conditions like IFR, over water, and at night.
  2. When using an iPad or other tablet for in-flight charts and navigation, turn off cellular and wifi data services to minimize the possibility of interference. (Be aware that iPad’s “Airplane mode” turns off location services, too, disabling the device’s internal GPS. However Bad Elf claims their external GPS continues to work in “Airplane Mode.”)

If you need to access your smartphone in flight for chart backup, backup GPS navigation, or passenger music or games:

  • Set your iPhone to “airplane mode” in flight. The internal GPS may not work, but reportedly some external GPSs like Bad-Elf will, or
  • For AT&T iPhones only, Patrick recommends enabling the “SIM PIN” ID in your iPhone’s settings. (Settings > Phone > SIM PIN) This isn’t your general “passcode lock,” but rather an additional code you must enter to enable your phone’s sim card for cellular activity. Yes, you’ll need to enter an additional code to enable phoning and texting when first turning on your phone, but by not enabling it during flight Patrick says you can leave your phone on to access charts, GPS, music, and other non-communication uses, without risking cellular interference to your avionics.

As Patrick observes, most of the nifty new electronics devices and features we enjoy in the cockpit (smartphones, Bluetooth, and WiFi hotspots in particular since they actively transmit RF), appeared on the scene long after most of our cockpit avionics were designed and installed. Therefore the manufacturers and installers of our panel equipment could not have foreseen or protected against interference from many of the devices we now carry. That’s why it’s so important to turn them off, especially when the stakes are high as in instrument flight.

Disclaimer: I’m no avionics expert, nor have I collected statistically-relevant data, so it is entirely possible these concerns may be incorrect in fact or scope. (For example, if the problem exists is it just with iPhones? Or Android and other smartphones too?) However, I’m hearing enough anecdotal reports from trusted sources that it seemed important to alert fellow pilots to the possibility, especially since the problem (if true) is insidious, potentially dangerous, nonintuitive, and yet potentially easy to avoid or rectify. Also, I have not personally tested most of the above tips, so try them yourselves, and do not take them as proven techniques. Rather, as another CFI observes, “It’s important to remember that none of these devices are TSO’d or even tested to that standard so it’s very much use at your own discretion.”

I will add to this post as new information comes to light. In the meantime, fellow pilots, turn off your smart phones (or at least disable their cellular service) prior to flight!

©2011 Gregory N. Brown

6 thoughts on “Beware! possible smartphone interference with panel-mounted GPS!

  1. Greg,
    Can you provide any other source for this interference story beside your friend, Patrick?

    Color me skeptical, but it seems that just as the iPad 2 3G (with pilot-oriented apps like ForeFlight) is out there doing some amazing things–short of real-time WX–for under $1,000, certain companies, like Garmin, would likely be getting nervous. I wouldn’t be surprised to see a negative rumor campaign getting started.

    Just wondering. {taking tin foil hat off}

    Disclosure: I own an iPad 2 3G with a ForeFlight 4.0 subscription and absolutely love it. I think it would be an incredible tool for most VFR pilots, especially those who rent.

    1. Hi Bruce, I have it from three independent sources at this point, all well qualified to comment. I agree with your concern about a negative rumor campaign, however. At this point it appears that the major risk of interference exists only when cellular phone and data services are active. Turn them off, as you can in iPad settings or via “Airplane mode,” and such concerns largely go away. Keep using your iPad!

  2. Thanks for the update, Greg!

    If the day comes when I get my plane with the fancy Garmin panel-mounted GPS, I would likely only use the iPad in the plane for the EFB goodies, and kill the geo-tracking features.

    In the meantime, I’m enjoying the heck out of my iPad 2.

    BTW, I knocked out my night T/Os and landings requirement last night with Fred. FUN!!

    I’ll be taking the written a week from Friday and with a few more hours of dual should be taking the Practical around first of June. Getting so close, I can taste it.

    1. In the meantime, Bruce, just turn off cellular and wifi services in flight (in lieu of using Airplane mode) and you can still use your iPad’s internal GPS in flight.

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