15 years ago a GPS unit installed in a light aircraft was a rare and wondrous thing.
Now they are almost the staple method of navigation for both VFR and IFR flights.
Their functionality and ease of use can be blamed for over-reliance on GPS.
Why do a wind calculation when all you have to do is follow the line to keep on track?
Why fiddle with your whizz-wheel, working out a ground speed, when it is displayed for you on the GPS screen?
Had pilots needed to do complex programming to make the system work, or have to make regular calibrations to be able to rely on them, the proliferation of GPS might not have been as fast or as wide-spread.
Having established GPS as the zenith of navigation technology, manufacturers have advanced the product by fine-tuning different aspects like display clarity, by weight reduction and adding super-capability that is – for Australia – uncertain to lead to any benefit, like Wide-area Augmentation System (WAAS).
With WAAS for Australia being over the horizon and going in the other direction, pilots need to weigh up whether or not this capability is of any advantage to them at all.
US manufacturers are building GPS units with WAAS as standard - but if you can’t use it, then there is no extra benefit over another unit that doesn’t have that capability.
But this could figure in your buying decision if you intend to take your Citation to the US a lot.
Australia will eventually get an augmentation system in some form, so the ability of the GPS to use other systems as well as WAAS may prove beneficial in the future.
Major decision factors
The two big manufacturers, Bendix King and Garmin, offer a huge range of GPS units to satisfy just about every price/capability requirement.
In a very broad sense, they are divided into those that have an integrated VHF comm and those that don’t.
This needs to be the first decision made.
Having the comm will allow you to retire your old set and at the same time save weight because you’re putting one box in where two would normally have to go.
Another big one is what other avionics you want it to talk to.
Integration is the way of the future and GPS units are already being asked to supply information to multi function displays (MFD), primary flight displays (PFD) and autopilots.
Cross-pollination of tasks is seeing the line between GPS and MFD becoming somewhat smudged, and the whole thing becomes a blur when the new flight management systems (FMS) come into calculation.
Further decisions to be taken are: colour display or two-tone, and the size of the display screen itself. With these decisions under your belt, you can then assess the need and benefit of all the other built-in tricky bits.
Honeywell Bendix King
KLN 35A
Being at the lower end of the GPS range, it is fair to expect these units to have not much above the basic functions.
The displays are both two-tone LCD, but the readability and contrast looks an improvement over GPS units that previously carried the Bendix King brand.
All the desired functions like Direct-to, flight planning and user-defined waypoints are included.
In short, these units are light on bells and whistles, but they get the job done and not everyone wants to pay for anything above that simple requirement.
If you’re thinking of fitting it to your workhorse Warrior, the price will be a lot more attractive than something more upmarket.
WxHxL (mm): 158 x 50 x 289
Weight (kg): 0.94
TSO: None stated
RRP: $US2,682 with Atlantic, Americas or Pacific database.
KLN 90B
BK has gone for another display type on the 90B: a green-on-black CRT.
Certainly, the display seems to be clearer and, not having a back-lit screen, it won’t wreck your night vision.
One tricky feature is that the screen can be split in two, so you can check on airport services, do calculations and call up VORs whilst still having the GPS OBS screen up.
The gem in all of this is that it enables the pilot to change the waypoint without having to change the page to do it; you can still have the nav info on the other side of the screen.
There are 70 different combinations of left/right page.
As an approach certified unit, the 90B has all the functions you would need to get on the ground smoothly and without fuss: airport data, navaid info, frequencies, SIDs, STARs and intersections.
Strangely, BK only offers two databases rather than the customary three: Americas and International.
Presumably, Australia and New Zealand are lumped with the rest of the non-Americans.
At 2.66kg, this GPS does seem a bit portly for one that doesn’t include a comm set.
WxHxL (mm): 160 x 50 x 334
Weight (kg): 2.66
TSO: C129
RRP: $US8,997
KLN 94
Bendix King introduces a colour display with the KLN 94, making it the GPS most likely to suit GA operations.
In short, it satisfies more demands than other units in their range.
Based on the operating system of the deleted KLN 89B, the 94 has been designed to make IFR flight easy, particularly the approach phase.
Selecting an approach procedure is fairly straight forward with minimal tweaking needed to get the profile active.
For VFR pilots, the data base also contains cartographic info, so as well as your airports, VORs, SIDs and STARs, you also get railway lines, roads, rivers and towns.
Again, BK hasn’t seen fit to include a comm set, but the KLN 94 can be connected to a KX 155A or KX 165A transceiver.
This enables frequencies selected in the GPS to be loaded as the standby frequency.
The 94 can also be linked to the budget-priced KMD 150 multifunction display to create a cost-effective display system.
WxHxL (mm): 160 x 50 x 274
Weight (kg): 1.63
TSO: C129a Class A1, en-route, terminal and approach
RRP: $US4,805
Garmin
GNC 300XL / GPS 155XL TSO
What you have here is the “Jetstar” of the Garmin range: while these units lack the pizzazz of the more popular, higher-priced models, they are good fits for customers who want no more than the basic functions.
All the mandatory features for a good GPS are here and the operation is simple regardless of whether you’re after airport data, VORs, NDBs, SIDs or STARs.
Three databases are offered: Americas, International and Worldwide.
Both units are TSO’d for en-route, terminal and approach, but the NPA is only for the US.
The display on both is the basic two-tone black-on-yellow with auto contrast and is reversible for night flying.
It also has an auto-zoom feature that will keep the dots that represent you and your destination always on the screen.
The 300XL has the standard 760-channel comm. set. Good for starters, but for serious IFR, look further up the scale.
WxHxL (mm): 143 x 51 x 159
Weight (kg): 300XL–1.16; 155XL–0.93
TSO: C129a Class A1, en-route, terminal and approach; 300XL–C37d and C38d also.
RRP: $US5,595
GNC 250XL / GPS 150XL
At face value, these unit are the largely the same as the 300XL/155XL combination.
The difference comes in the high-definition LCD display that has (according to Garmin) twice the number of pixels as any other panel-mounted moving map display.
This means that curved lines are less jagged and alpha-numeric characters stand out better.
Another variation is that neither has a TSO’d GPS, with certification available only to AC 20-138 (VFR), which is an airworthiness approval.
The transceiver on the 250XL is TSO’d.
WxHxL (mm): 143 x 51 x 159
Weight (kg): 300XL–1.16; 155XL–0.77
TSO: Not for GPS–AC20-138 (VFR) only; 250XL–TSO C37d and C38d (comm) also.
RRP: $US3,340
GNS 430W / 530W
Garmin’s superstars, even if measured only by sales.
Ease of use, versatility and functionality have made these units the weapons of choice for many Australian pilots, both IFR and VFR.
Don’t be concerned with the new ‘W’ designation, it just means they are now WAAS capable, which for the time being is of no value in Australian airspace.
The good news is that new models are fitted with a high-speed processor that Garmin claims does calculations five times faster than the older models, and the older ones were by no means tardy at doing that.
Both the 430 and the 530 are TSO’d as sole means navigation, unsurprising given that there is little they can’t do for you.
As well as the usual GPS magic, sophisticated information such as TAWS and stormscope couples with a VHF comm/nav ability to make a complete integrated navigation system.
The difference between the two is the 125mm display on the 530 compared with the 430’s 100mm screen.
WxHxL (mm): 430W–158 x 67 x 280; 530W–158 x 116 x 280
Weight (kg): 430W–2.8; 530W–3.7
TSO: GPS 146a Class 3, transceiver C38/37, VOR C40, ILS C36
RRP: $US11,295
GPS 500W / GPS 400W / GNC 420W
Shadows of their more famous brothers, the 500W and 400W are effectively the 530 and 430 without the nav/comm.
Together they offer cheaper alternatives if you’re happy to keep your existing VHF nav/comm units.
They are TSO’d to the same level as the 530 and 430.
The GNC 420W has a comm set, but no VHF nav capability.
Before you select one of these units to integrate with your existing system, make sure you have your avionics expert have a good long look over your entire panel and the concept you are going for.
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