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Larry Anglisano |
You've purchased a new-to-you airplane
with a panel-mount IFR GPS -- but the placard reads "VFR-only." As
Larry Anglisano explained recently in Aviation
Consumer, you can upgrade your
unit to IFR (but you may want to sell it and start from scratch). Here's
what it'll take to make it happen.
This article appears in the April, 2002 edition of Aviation
Consumer, and is reprinted here by permission.
With the world of avionics changing faster than
you can cycle a master switch, even those of us who deal with this stuff every
day have our hands full keeping track of it all. What's new? What's best? And,
increasingly, what's legal?
Because of the massive influx of new technology, there's a long tail of
radios, navigators and displays stretching back more than a decade, leading many
owners to ask us if the old RNAV, loran or even first-gen GPS they still have in
the panel is legal for IFR.
Surprisingly, the answer is often yes. On the other hand, some recent
installations we've seen of supposedly IFR-approved navigators aren't legal at
all. They don't have the right components, lack the switching networks and the
required paperwork can't be found.
As more used GPS units find their way to market, expect to see more of these
installations in an airplane you might consider for purchase. Does it matter if
it's legal or not?
It depends on what you plan to do with the airplane. In most cases, the legal
nits don't matter on day-to-day, practical basis. If you file /G with a VFR
panel-mount, you're unlikely to get busted -- but it's still not legal. And if
you think you're buying an IFR navigator, make sure that's what you're getting,
not a "VFR-only" installation.
VFR-Only
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[Click any image for a larger version.]
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At a quick glance, both of
the Garmin navigators shown here appear to be identical. Yet the 150XL,
top, is a VFR-only GPS while the GPS 155XL, lower, is IFR approved.
However, that doesn't mean it was certified for IFR in the aircraft it was
installed in. Check the logs and AFM to find out if it's legal.
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The number of VFR-only GPS navigators in the fleet is relatively high. Some
are even "IFR approvable" but not legally certified. It's not uncommon
to see something like an older Garmin GPS 155 or even a Bendix/King KLN90B --
both IFR units -- installed on the cheap, with a "VFR-only" placard
somewhere on the panel. That might lead you to conclude that the placard is an
artifact, left over from a previous installation.
Chances are, however, the IFR navigator was put in by an owner who just got a
good price on it and had no intention of using if for IFR. The shop complied --
which it can legally do -- and put the placard on the panel, thus avoiding the
time and expense of an IFR flyoff and the additional paperwork.
Some owners, upon discovering this, assume that since they have an
"IFR-approvable" GPS, getting it officially blessed for legal IFR is a
piece of cake. Sometimes it is, but usually it's not. Nor is it cheap. Let's
examine what's required.
Keep in mind that every airplane is unique and we see all kinds of strange
scenarios that suggest that what works for one won't always work for another.
TSO Or No TSO?
As with most other avionics equipment, GPS units and their components are
built to a TSO specification and, in the world of GPS navigators, the two most
important are TSO C129 (A1) and TSO C129 (A2) -- A1 being en route, terminal and
non-precision approach-certified while the A2 versions allow en route and
terminal navigation only, no approaches.
There are some en route only boxes out there, such as the UPSAT GX-55 and
some versions of Garmin and Bendix/King navigators, that weren't signed off for
approaches in the particular airplane they were installed in.
What's the difference between en route and terminal operations? CDI scale,
mainly. The terminal mode allows a 1-mile scale while en route is 3 miles.
The IFR TSO is quite specific about what an IFR navigator is supposed to do
and how it must be installed. Some of the specifics include one-second position
updates, fixes stored in a non-corruptible database, pilot selectable CDI
sensitivity, RAIM integrity alarms and paths between fixes defined only by TO-TO
navigation.
Now, if your TSO'd receiver has the official approved designation, it will do
all this stuff and a lot more. But unless it's installed with all the required
annunciators -- including the required coupling to a CDI-- it may not be
IFR-legal.
Sometimes, a box that looks just like an IFR-approved navigator isn't. For
example, you can put two physically identical GPS units-- the Garmin GPS150XL
and the GPS155XL --side by side. The difference is that the GPS155XL is blessed
with TSO C129 (A1) while the GPS150XL isn't, falling under AC 20-138 for VFR-only
guidance.
Similarly, before it made the KLN89B and the KLN90B -- both
IFR-approved navigators -- Bendix/King had VFR-only versions.
To qualify for installation approval, the GPS sensor or antenna must also
meet the TSO. Some of the earlier Bendix/King KLN90 navigators, for example, had
a non-TSO antenna system. After all, they weren't IFR boxes so they didn't need
a TSO'd antenna. Don't assume that you can use the existing antenna with any IFR
navigator. Have your shop check the part numbers before proceeding with an
upgrade.
Transplant It
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Two must-have items for most
GPS IFR installations include a TSO'd antennna, top, and a remote
annunciator / switching panel, such as the MD41, lower photo. Some
navigators have self-contained annunciation.
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Our advice is that, if you're in the market for a quality used IFR system,
find an entire system that was removed from the same aircraft and purchase all
components as a package. For example, the aforementioned IFR KLN90A/B can be had
on the used market quite reasonably, complete with the required annunciation
control panels and appropriate antenna removed from the very airplane it was
approved on before.
While on the subject of antennas, the shop may want to replace any cable you
already have in place. Let them. Although the existing cable from a VFR
installation will likely work for feeding signal to the receiver, low-loss
coaxial cable is required and for good reason.
You're guaranteed top performance with the bonus and flexibility for longer
cable runs with minimal signal loss. Most common is the expensive RG142 coax
and, if you don't have it already, it should be added to meet the IFR criteria.
With some navigators and applications, an RF signal notch filter, appropriate
for the 1.5GHz band, should be installed to provide uninterrupted GPS signal
flow. These filters were imperative with many earlier GPS systems and your shop
may recommend one.
As a side note: with panel and fuselage space often tight, optimum placement
of components is an ever-increasing challenge. Major manufacturers are learning
what works well and not so well with different airframes and/or when mixing
equipment. You can only hang so many antennas on a airplane without conflict.
Even with the best possible combination of placement, outside factors such as
noisy strobes and beacon power supplies will make their presence known, even if
they have previously caused no problems.
The Baro Connection
It's a 50/50 deal whether that old beater VFR GPS currently in your panel
talks to your altitude encoder -- but your new IFR GPS will have to.
Altitude information must be fed to all IFR installations from an encoding
altimeter or blind encoder. Why? Because the altitude feed is necessary for RAIM
computations and is also used in conjunction with navigators that have VNAV
descent profile features.
Most common altitude encoders output "gray code" data format
altitude information. However, some navigators -- the entire line of UPSAT/Apollo
units, for example -- accept only serial data, a more precise data stream.
In these cases, either an appropriate serial encoder must be installed or a
gray-code-to-serial "happy box" converter will be needed.
The point is, while better shops go the extra mile to provide the baro
interface to even VFR boxes, some shops don't bother. Plan for it if you want an
IFR-approved system.
Similarly, if the transponder/encoder system is getting tired, now's the time
for upgrade because there's little room and tolerance for marginal equipment
when interfacing IFR GPS. As we have reported, newer transponders such as the
Garmin GTX327 and UPSAT SL70 output altitude data in either serial or gray code
format for the purpose of feeding a navigator. It's nice to have the choice but
it'll cost money to get there.
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En Route Only
or Approaches, Too?
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When
making the switch to IFR from a VFR install or buying a new or used
navigator, many owners struggle with the question of certifying for
enroute only or enroute and approaches.
As always, the cost Delta
comes into play and when it’s all added up, it almost always makes sense
to opt for full approach certification, if there’s a choice.
As far as the legalities are
concerned, if you have an (A2) box -- enroute/terminal only -- you can
freely use it as a DME substitute, for off-route IFR navigation and to
substitute for ADF on ADF-required approaches. DME substitution also
applies to precision approaches.
The good thing about an (A2)
box is that you needn’t have a current database for legal IFR
navigation. You’re allowed to use current paper charts to check fix
accuracy. (As if anyone actually does that.) For approaches, you’ll need
a full-up (A1) box, installed with all the remote hardware, flight checked
and with an approved AFM supplement. We’re quite certain there are
owners out there flying approaches with properly installed IFR GPS that
isn’t legally approved. If you’re picky about such things -- we are --
get the flyoff and paperwork done.
If your existing GPS is VFR-only,
it’s probably what we call standalone, meaning it doesn’t drive a CDI
and/or it isn’t interfaced with the altitude encoding system.
To make it en route or
(A2)-approved, a flight test will have to be done and a Flight Manual
Supplement prepared and you’ll still need mode annunciator lights.
So the steps and equipment required to make it IFR-legal are
similar whether you go C129 (A1) or (A2).
Of course, if the navigator is only approved to C129(A2), such as
the UPSAT GX55, you’ll have no choice other than another navigator
entirely.
Some owners have suggested
that an approach-approved navigator be interfaced for en route and
terminal only, in hopes of saving some money. But that makes little sense.
Get a quote for both options and you’ll see why.
And last, if you’re still
on the fence about the IFR versus VFR issue, but want to install a GPS
navigator, buy a box that’s TSO C129 (A1) approved.
You can always add the required accessories and interface later on.
The cost difference between a basic VFR versus basic IFR navigator is
surprisingly little. It’s
the interface and accessories that drive the cost up.
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Remote Hardware
All IFR installations require varying degrees of remote annunciation, except
the Garmin GNS530/430 and Bendix/King KLN94 in which annunciation is integral to
the navigator. But when remote annunciation is required, it must be positioned
within the pilot's normal instrument scan.
These mode annunciators and control switches advise the pilot of any messages
transmitted from the navigator and appropriately arm and activate the approach,
if the navigator is approach-capable.
Also required for both en route or approach certification is a course
deviation indicator which displays GPS navigator left/right and nav flag
information. This can be accomplished with most HSI systems and many options are
possible for interfacing with rudimentary nav heads, as we reported in the March
issue of Aviation Consumer.
In any case, if your existing VFR GPS doesn't display steering information on
a remote head, this will be the most costly part of getting it approved for IFR,
assuming it's a TSO'd box.
The Paper Chase
Now that IFR GPS has become relatively routine, most FAA FSDOs seem to know
what's required to make these systems legal. We don't hear many horror stories
about FSDOs requiring a $10,000 contract to a DER to write a POH supplement.
However, there's no question that some FAA regions are quicker at IFR approvals
than others.
We polled several shops on both coasts and most report that the IFR GPS
approval process and satisfying the expected criteria usually goes without a
hitch. What's important is that approval paperwork is clearly drafted and all
the details appropriate to the installation are noted.
System integrity has to be proven and all of the hardware and interfaces
we've described here must be referenced.
Most shops that routinely turn out IFR GPS installs aren't running into snags
with the FAA. Buyers should remember that until it's officially approved, the
system is to be used for VFR navigation only and placarded accordingly. Consult
with your shop beforehand and review the exact procedure for your region.
Generally, what FAA offices seem to want is proof of absolute system
integrity. Most owners underestimate the amount of paperwork and testing
required for an IFR GPS, whether approach or en route-certified. A Flight Manual
Supplement is drafted and this booklet is specific for each installation. It
describes all aspects of the GPS installation and includes general system
information and specifications, emergency operating procedures in case of
malfunction, system limitations, normal procedures, proof of flight testing and
applicable FAA paperwork, such as FAA Form 337.
Most FSDOs are specific about flight test data. If the navigator is
approach-approved, multiple GPS/overlay approaches must be flown to prove that
the system will navigate the approach and the missed procedures. If the
navigator is interfaced with an autopilot, it must also be proven that the
autopilot will fly correctly. Other parameters include passing through fixes
within a specified degree of accuracy and proper interface with existing
on-board stuff, including a radio interference test.
Once the Flight Manual Supplement is approved by the FAA and the shop, it has
to remain in the aircraft at all times, since it's part of the AFM.
We're not sure how interested the FAA is in enforcing these fine points in
the regulations. Theoretically, if you fly an IFR approach and are ramp checked
and found wanting in the paperwork department, it's no different than getting
ramped without having required weight and balance aboard the aircraft. According
to our polling there have been violations, but we don't know how often it has
happened. We don't think it's a good idea to ignore these legalities, but it's
your ticket.
If the navigator and/or installation are certified for only VFR, a placard
must be installed on the instrument panel that says as much. We've even heard of
folks failing an IFR ride because they filed a /G plan without having the GPS
approval paperwork. We assume the examiner was paying back the applicant back
for weaseling out of the ADF portion of the test.
Conclusion
Although system certification has become straightforward, we have seen many
instances in which a customer has purchased an aircraft that was represented as
being IFR GPS-equipped, only to find that the documentation was missing.
Either the seller had an IFR system slapped in to make the aircraft more
attractive but never followed through with the certification paperwork or the
work was done and never filed properly. We have also worked on a few factory-new
Mooneys, going back to the early 1990s, that were represented as IFR
GPS-equipped but didn't have appropriate annunciation for the GPS system.
Somehow, they slipped off the assembly line unfinished.
In any case, expect your shop to proceed through the installation with a
fine-toothed comb because they're accepting responsibility for the integrity of
the system.
In short, making an IFR system out of a VFR system can be relatively painless
or a nightmare, or anything in between. In many cases, it may actually be
cheaper and more practical to buy a used transplant system and keep the VFR GPS
in the panel as back-up -- or sell it on the used market and apply the proceeds
to the IFR installation.
Larry Anglisano is the Aviation
Consumer avionics editor. He works with EXXEL Avionics in
Hartford, Connecticut, where he does GPS flyoffs, among other tasks.
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