Its all about angles and drift, son. Thats all you gotta know.
Thats what our first instrument instructor, a crusty old military type, had to say about flying a perfect ILS. A centered needle merely measured the results of flying a perfect intercept. Keeping it there required heading discipline.
Glitzy though they may be, new-age GPS mapcoms dont help in this regard for a couple reasons. For one, the display is center stack and out of the scan. For another, unless the box is customized just so, matching bearing and track to hold an approach course is like stacking greased ball bearings; more luck than skill. After all these years, flying the needle is still the method of choice.
One clever gadget we recently tried that helps is the NavAlert II, the latest product from Icarus Instruments, which developed the AltAlert, a combination altitude alerter, tank timer and multi-purpose cockpit nag.
The NavAlert II sells for $1595 complete or $1695 with a localizer/glideslope option.
What It Does
If youre not a serious IFR pilot with a grasp of the subtleties involved, turn the page. This product isnt for you.
What the NavAlert II does is combine various navigation data from a GPS into a single small display thats mounted center scan, ideally between the attitude indicator and the HSI or DG.
Its highly customizable but basically, it refines course, intercept and distance information into a couple of easily interpreted values.
For example, on a tight ILS, one side of the display can be configured to show groundspeed, distance or time to a fix while the other side displays track angle, the difference-in degrees-between the desired track and your current ground track. In other words, it tells you how far to turn and in which direction. (A tiny arrow points the way.)
Result? In an easy-to-understand format, the NavAlert arrests the tendency to needle chase by displaying both turn direction and value. (You do this mentally when you put the HSIs deviation indicator on the lubber line until the needle recenters.)
Other Functions
Like the AltAlert, Icarus previous (and still available) product, the NavAlert II has a number of altitude alerting functions, including off-level alert, climb and descend alert and a gear alerter if youre descending into the airport with the gear still in the wells. (It beeps whether the gear is down or not, as a reminder.) All it needs to know is the current local barometer setting and it calculates the rest. For example, if youve been assigned to climb and maintain 3000 feet, you first set the baro value before takeoff, then scroll in 3000 feet as the target altitude.
During the climb, the instrument emits a small audio boop as you approach the target and annunciates LEVL. If you deviate from that altitude, it will again beep, then issue a climb or dive directive, as appropriate. The audio alerts, of course, are piped through the audio panel so theres no mistaking them. Volume is controllable via set-up menu.
The altitude alerter function continues to run in the background, even if youve elected to display GPS nav information. If you deviate, the alerter function will override lateral navigation and annunciate aurally and visually.
In addition to these functions, the NavAlert II also shows what ATC sees as your Mode-C altitude. Since it takes pressure altitude output from your encoder and it knows the baro setting, it can do the math to calculate the radars displayed Mode-C value.
Gear alerting is entirely altitude based. The instrument isnt coupled to the aircraft gear circuit, thus it serves only as a dumb reminder. It can be customized to alert between 500 and 1000 AGL above the destination airport. On an approach, the NavAlert can be set up to prompt at intermediate altitudes and, of course, MDA/DH.
Just One Knob
Surprisingly, all of this is accomplished via a single knob with left/right/push-in as the only options. Although we found the AltAlert operating scheme baffling at times, the NavAlert strikes us as being easier to use, although it generally follows the same logic. The setting knob, for example, is hot for the most often used function; setting a new target altitude for a level-off reminder.
To set other functions or to customize the display, pushing the knob in opens a mode option which is used to set baro, destination field elevation and to customize what the display is showing. And we found the instrument to be quite customizable.
Its capable of displaying two fields, one left and one right. Whats displayed in those fields-distance to waypoint, groundspeed, time to waypoint, track angle, baro, course deviation, groundtrack, to name a few-is pilot selectable.
For example, while enroute, youll probably want distance to waypoint and groundspeed but on approach, youre more interested in track angle and time to waypoint.
Overall, we found the NavAlerts logic easy to master with a few minutes of practice. But a cautionary word: In exchange for its alerting and helpful data consolidation, it demands some attention, raising the workload at times, especially if you use the altitude alerting for intermediate stepdowns and MDA/DH. Also, if you want the audible tank timer function, the AltAlert has that, the NavAlert doesnt.
For an additional $100, you can add the LOC/GS option, which serves as a repeater for the primary localizer and glideslope display, a nice back-up for anyone flying serious IFR.
Conclusion
As noted, if youre a VFR-only pilot, the NavAlert II may be more sophistication than youll ever need or want. But for serious IFR flying, we think its a worthy addition to any panel, although not in the must-have category, given the relatively high cost.
It fixes a tiny but undeniable shortfall in the way GPS receivers display-or fail to display-the fine resolution you need to fly crisp IFR procedures, thus, we think it represents a fair value for the price.
Also With This Article
Click here to view the NavAlert Checklist.
Click here to view the Track Angle Error Illustration.
Click here to view the Icarus Address.
