Since the first one was introduced a decade ago, portable ADS-B receivers have become essential tools for any pilot who flies beyond the traffic pattern. These compact wireless devices deliver an incredible amount of information to electronic flight bag apps, including subscription-free in-flight weather, traffic alerts, backup attitude, and GPS position. The result is smarter decisions, safer flights, and happier passengers.
Over time, ADS-B receivers have grown to be much more than just weather receivers, integrating a variety of safety features into a single device. ForeFlight has carved out a dominant position in the market with Sentry, a small ADS-B receiver that also offers carbon monoxide monitoring and alerting. Pilots have given it high marks for its excellent battery life and long feature list.
Now there’s a new top dog in the portable weather receiver market, with the introduction of Sentry Plus. While slightly larger than the original Sentry, it’s still a compact and lightweight device that easily mounts on a side window via a suction cup. In addition to popular features like datalink weather and traffic, Sentry Plus includes some thoughtful upgrades and performance enhancements. Here’s a look at some of the new features.
Built-in OLED screen
The first change is obvious as soon as you take Sentry Plus out of the box—it features a sunlight-readable 1.3” screen on the front. This isn’t colorful enough or large enough for displaying radar images, but it does make it easy to monitor performance, including: connection status, battery life, carbon monoxide level, ADS-B reception, groundspeed, and G-load.
The familiar three lights from the first Sentry are still there, showing battery, CO, and ADS-B status, but now pilots can tap the power button to cycle through each of the screens for more information. This is ideal for troubleshooting, but for normal operations we found ourselves flying with it on CO status. The screen is an OLED, which is both easy to read in direct sunlight but power-efficient so there’s essentially no battery life penalty.
Unmatched battery life
Speaking of battery life, this is one area where Sentry Plus is the undisputed leader. With up to 18 hours of use on a single charge, it will last for an entire weekend of flying and still have a reserve. We flew with Sentry Plus for a week (four flights in a variety of airplanes) and never charged it. This just makes life easier—we always try to start a trip with a fully-charged battery, but sometimes that’s not possible. The long battery life offers some insurance for situations like that.
Another enhancement with the battery is the ability to charge from smart-charging plugs. Many consumer electronics these days, including newer iPhones and laptops, use USB-C plugs to provide faster charge times (sometimes called Power Delivery). While the original Sentry will not charge from these sources, Sentry Plus takes it in stride. It’s another convenience feature, since you don’t have to carry a proprietary charging cable or plug.
There’s also a new auto power on/off option. When this is set to on and Sentry Plus is connected to externalpower (cigarette lighter plug, battery pack, or aircraft electrical system), the device will automatically turn on without the need to push any buttons. It will also automatically turn off when it detects the flight is over (power off and groundspeed below 10 knots for 45 seconds). This is a great option for pilots who want to build a Sentry Plus into an experimental airplane panel or mount it in a more convenient location that’s out of arm’s reach.
Flight data recorder and replay
One feature that really impressed us was the built-in flight data recorder. This isn’t a “black box” to be used in case of a crash, but rather a way to systematically track your flights and improve your pilot skills. Other ADS-B receivers (notably Stratus 3) have this feature, but we always found it slow and hard to use. With Sentry Plus, ForeFlight has completely integrated flight logging and playback into the app. It’s like a FitBit for your airplane.
Sentry Plus continuously records when it is powered on, so there’s no button-pushing required to log a flight—you don’t even have to be connected to ForeFlight. It stores GPS position, altitude, and AHRS-derived attitude, while automatically organizing flights based on power-on time and groundspeed (up to 16 flights).
The real magic happens once a flight is logged. ForeFlight will automatically download all flight data from Sentry Plus when it detects the flight is over, eliminating the need to manually import flights into the app. After a flight, we simply turned off Sentry and grabbed our iPad (make sure you turn off Sentry Plus before you close ForeFlight). When we walked into the FBO, a new track log was available in ForeFlight—in fact, downloading flight data took just a few seconds. Manual importing is still available, but we never had to use it.
The app’s powerful Track Logs tool makes it easy to quickly review a flight without switching to a separate app, which is ideal for post-flight debriefs. Much more than just a two dimensional track log, Sentry Plus provides a detailed recreation of your flight, including altitude and pitch/bank information. You can also view important data like speed, altitude, pitch, and bank on the graphs below the map. This is perfect for reviewing training flights or practice instrument approaches, and because it’s fast and easy we found ourselves doing it much more often.
One final tip: disable auto start/stop track log in the main ForeFlight settings, since this uses the basic 2D logging feature, not the higher fidelity Sentry Plus track logs. You’ll have duplicate logs if you leave this on.
Astute pilots will notice a new graph option on the Track Logs page: G-load. That’s because Sentry Plus has a built-in G-meter, as you’d find in an aerobatic airplane. This can be viewed as a data field at the bottom of the Maps page for a real-time look, or it can be displayed as a historical trend in Track Logs. It’s also an option for the screen on Sentry Plus.
While aerobatic pilots are used to tracking Gs during a routine (including min/max), it has value for everyday pilots as well. Student pilots practicing steep turns or rusty pilots getting current on landings might be surprised to see how much G-load varies during common maneuvers.
ADS-B and FLARM traffic
Besides weather, most pilots’ favorite feature on their ADS-B receiver is traffic. Especially since the 2020 deadline for aircraft to equip with ADS-B Out, the traffic information available has become more complete and quite useful, especially in busy airspace. Sentry Plus has a dual band ADS-B receiver, so you’ll see traffic both directly from other aircraft equipped with ADS-B Out (air-to-air transmission) and from ground stations (TIS-B traffic broadcasts).
We found the reception to be outstanding, easily picking up 10 ground stations in cruise and airplanes broadcasting 1090 MHz out from over 100 miles away. If your airplane is equipped with ADS-B Out, ForeFlight will even provide pop-up and audio traffic alerts.
Sentry Plus adds another traffic feature for European pilots: a dedicated FLARM receiver. FLARM is a short-range collision avoidance technology, particularly popular in Europe and among glider pilots, that uses small, transponder-like devices to transmit aircraft position. The FLARM receiver in Sentry Plus is optimized for the European FLARM frequencies, specifically the SRD860 band (868.2 – 868.4 MHz). Note that you’ll need to purchase a FLARM decoding license from ForeFlight in order to enable FLARM traffic on your iPad. For US pilots, this feature won’t mean much, but it’s a helpful addition for those flying in the UK, France, or Germany.
WiFi client mode
One final new feature will be most useful for pilots flying larger airplanes with on-board WiFi systems, but is invaluable in these situations. Since Sentry Plus connects to your iPad via WiFi, such a connection would typically mean the internet connection is unavailable while using the ADS-B receiver. However, a new WiFi client mode option allows Sentry Plus to join your existing network (eg, GoGo), so you can get in-flight weather and traffic but still enjoy the benefits of your cabin WiFi. You can even select an option that will remember your aircraft’s wireless network and join automatically in the future. For business jet and airline pilots, this feature should be a welcome addition.
Carbon monoxide detector
Carbon monoxide is a hot topic in aviation, especially since the National Transportation Safety Board (NTSB) published a recommendation that all general aviation pilots fly with some type of CO detector. It’s not required, but it’s definitely a wise investment, especially if you fly a piston airplane where the cabin heat comes from a shroud around the exhaust stack. One small leak in the exhaust can cause deadly CO poisoning.
Among its long list of features, Sentry Plus includes a CO detector so it can fill that role quite easily. Since it’s integrated into a device most pilots use on every flight, there’s no extra battery to charge or screen to monitor; you’re more likely to use it and notice it. In fact, ForeFlight makes it hard to ignore a high CO alert. In addition to a visual alert both on the device and in the app, Sentry Plus will emit a loud audio alert. We had no trouble hearing this over the drone of a Lycoming.
Sentry Plus has a more sensitive CO sensor than its predecessor, so it can detect potential leaks earlier. However ForeFlight still uses smart algorithms to reduce nuisance alerts: you’ll get a yellow alert when CO is elevated, and a red warning if it continues to rise. In general, if you hear an alert you should shut off all cabin heat and consider landing at a nearby airport. Talk to a mechanic before you fly again.
The CO sensor in Sentry Plus lasts 10 years, so there’s no need for annual recalibration. It requires no additional ForeFlight subscription level either. In fact, since it’s totally self-contained on the device itself, it can work without the app at all.
Plus pilot favorites
In spite of all these new features, the best feature of Sentry Plus—like all ADS-B receivers—is still the subscription-free ADS-B weather. Once you’ve flown with 10-minute old NEXRAD radar and up-to-date METARs, you’ll never go back. Sentry Plus receives all the weather products transmitted by the FAA, including newer options like icing forecasts and cloud tops. As long as you’re in range of a ground station (usually by 500-1000 feet AGL), everything is regularly refreshed. ForeFlight makes it easy to overlay multiple weather graphics on your route of flight, so you can make informed decisions and stay safe.
Sentry Plus also includes a multi-constellation GPS receiver that is incredibly accurate and reliable. We almost always see 1 meter accuracy on the moving map, which unlocks all kinds of powerful features like terrain alerts and glide advisor. The receiver will even switch to Europe’s Galileo satellite constellation if the US’s GPS system is jammed or unavailable for any reason. It’s a powerful bit of redundancy, and it’s all automatic.
Finally, the built-in AHRS drives a real-time pitch and bank display in ForeFlight. If you subscribe to Synthetic Vision, you can even see a 3D view of the world, complete with airports, terrain, obstacles, and traffic. This is not intended for primary reference, but it’s a great backup, and in an emergency we would not hesitate to use it.
Sentry Plus packs a lot into one small device, but it remains easy to use. On our first test flight, we simply mounted it on the side window using the included suction cup and turned it on. Without reading the instructions, ForeFlight lit up with weather, traffic, synthetic vision, and much more. It’s the perfect enhancement to your iPad, like having a virtual co-pilot sitting next to you. Sentry Plus is now shipping, and is available for $799. It requires ForeFlight version 14.4 or later.
Compared to the original Sentry, the Plus model adds 50% longer battery life, a built-in screen, G-meter, flight data recording, FLARM traffic, WiFi client mode, and some overall performance upgrades. Overall, it feels like a next generation product and a nice upgrade for any pilot flying with an older ADS-B receiver. If you’re looking for a good value portable, the original Sentry is still available and it’s a great value at $599.