Every pilot wants the peace of mind provided by an on-board collision avoidance system, but unless you fly an airliner or bizjet, TCAS is probably out of the question. There are less expensive alternatives, however. A few months ago, AVweb publisher Carl Marbach installed a Ryan TCAD model 9900 in his Aerostar 601P — which itself involved some nasty surprises — and since then has been putting the unit through its paces. Carl describes what it's like to fly with this device, and discusses whether or not it's worth the money.
September 20, 1998
mid-air collision can, as they say, ruin your day. While we all know that we should spend
lots of time and effort looking outside for other aircraft, the increasing computerization
of our cockpits GPSs, FMSs, digital engine analyzers, and other bleeding-edge cockpit
gadgetry is demanding ever more of our time inside. A United Airlines check pilot once
expressed his airline's concern about the new flight management systems and "glass
cockpit" aircraft this way: "If you looked in through the windshield of a modern
jetliner, all you'd see is two bald spots." Those, of course, would be the heads of
the front seat occupants looking down at their FMS computers instead of looking outside.
To answer some of those concerns, airlines have had to install TCAS Traffic
Collision Alert Systems in all their aircraft. Bizjets have followed suit and most
modern jet aircraft are so equipped today. But, as often happens in aviation, those who
need it the most don't have it. General Aviation operates in a more crowded environment
than the airlines, and to make matters worse, we do it mostly VFR. There are about 5,000
airline aircraft flying today, but more than 200,000 GA planes in that same airspace. The
airlines fly most of their trips at the Flight Levels above 18,000 feet while GA spends
most of its time below 8,000 feet in the haze, smog, rain and other challenges to
When I invite non-pilot passengers aboard my Aerostar, most look
at the instrument panel and are comforted by the prominent radar in the center, because
they think it is used to avoid other aircraft. When they see a "Radar Equipped"
decal on the side of an aircraft, the general public thinks it is for traffic avoidance
rather, not weather avoidance. Most folks would be horrified to learn that our only tool
for avoiding collision is looking out the window.
So why not some type of collision avoidance system for GA? Well, the TCAS system
that the airlines and corporate jet-setters use is simply way too expensive. One bizjet
operator told me that the TCAS installations in their airplanes cost more than $75,000
each. Recently, BF Goodrich developed a lower-cost GA system, very similar to TCAS, that
sells for about half of that figure, but that's still far beyond what most piston GA
aircraft owners can afford.
The lowest-cost collision
avoidance solution presently approved for certificated aircraft comes from Ryan
International Corporation in Columbus, Ohio. Inventor Paul Ryan is perhaps best known for
developing the Ryan Stormscope thunderstorm avoidance system, which was later acquired by
3M and later by BF Goodrich. Ryan's solution for the GA collision avoidance problem is
called TCAD Traffic Collision Avoidance Device and has now evolved into a family of
five models with prices that range from $4,995 to $13,850 (not including antennas and
installation). A few months ago, I had a top-of-the-line Ryan TCAD 9900B installed in my
1979 Aerostar 601P, N6069N.
A Different Approach
The Ryan TCAD system is different than TCAS, which is why the names differ slightly.
The TCAD is a passive device, which listens to transponders, some of which may be a
collision threat, while TCAS is an active device that actually interrogates
transponders in the vicinity. Consequently, the TCAD is effective only if nearby
transponders are being interrogated by something else, like an ATC radar facility
or a TCAS-equipped aircraft. This doesn't seem to be a problem, however, at least in the
conterminous U.S. I've now flown with TCAD in some very remote areas of the "Lower
48" and it is a rare event indeed when my transponder reply light isn't blinking. (If
the transponder is blinking, it's being interrogated from somewhere, and the TCAD will be
Display unit, TCAD 9900 B.
The method of traffic display used by the Ryan TCAD is also very different from TCAS.
TCAS typically displays the position of threat traffic in graphic fashion on a circular
instrument showing your airplane in the middle, and some TCAS systems can display traffic
on a mapping system or EFIS display. In contrast, the Ryan TCAD has only an alphanumeric
display that shows the altitude and approximate distance of the threat and, on my
top-of-the-line 9900B model, an arrow showing the approximate direction of the threat.
The alphanumeric TCAD display takes some interpretation, and since the traffic may be
closing rapidly the non-intuitive nature of the display can be a problem. Fortunately,
after flying with the TCAD for a while, you learn how to determine quickly if the traffic
is a real threat (i.e. is at the same altitude and close by) and what direction to look
for it. My experience with the TCAD is that when it shows no threats you can relax, and
when it reports traffic, you better get your eyes out of the cockpit and start looking.
Like all good tools, it takes a little while to learn to use this one quickly and
easily. But, by my second or third flight after installing TCAD, I found that
interpretation took less effort, and I learned how to assess whether a warning was
something to worry about or not.
Ryan has recently announced the ability to display traffic from some TCAD models on
Eventide's ARGUS moving-map displays. Since I have an ARGUS installed in my Aerostar, I'm
looking forward to that enhancement.
Installation is No Picnic
TCAD 9900 B processor in nose avionics bay.
Installation of the TCAD turns out to be a non-trivial event, especially if you're
installing the advanced 9900B model. That system consists of a remote-mounted processor, a
transponder coupler that attaches to your transponder (the TCAD needs to suppress your
transponder periodically so that it can hear the transponder replies of other aircraft), a
panel-mounted indicator, two antennas (bottom and top), an optional visual traffic warning
light, and an optional connection to the aircraft's audio system. The TCAD 8800-series
does not require the remote mounted processor, but still needs all the other stuff. As you
can imagine, installing all this takes considerable time and effort.
And then, of course, there's the Friendly Aviation Agency...
Bottom antenna installation, TCAD 9900 B.
My Aerostar 601P is a pressurized aircraft, and the local Flight Standards District
Office (FSDO) here in Fort Lauderdale, Florida, insisted that a Designated Engineering
Representative (DER) inspect the aircraft, design the antenna installation, and create
engineering drawings to indicate where each rivet and mounting screw should go before
they'd let my avionics shop drill the first hole in the aircraft skin. The FSDO also
required that the radio shop create a wiring diagram and installation plan, and get that
whole package approved by an FAA avionics inspector before starting installation. As a
result, I was out-of-pocket for $1,000 before the first hole was drilled or screw was
I have heard that certain other FSDOs are not so difficult and demanding, and perhaps
in retrospect I would have been better off going "FSDO shopping" and taking the
airplane somewhere where the local Feds wouldn't make a Federal case out of a simple
avionics installation. It wasn't very long ago that radio shops could install antennas on
my airplane without any of this costly and time-consuming rigmarole. And, for what? What
airplane accident has ever been caused by the antenna installation? Well anyway, I can
tell you that here in South Florida, the FAA is more unfriendly to GA then ever before,
and they made us dot every i, cross every t, and jump through every hoop they could come
up with. (This will be the subject of a future article.)
TCAD display installation in my Aerostar.
The location is less than optimal.
There is a lot of wire to be run for the Ryan TCAD 9900B connecting the two antennas
and the panel-mounted indicator to the remote-mounted processor. The processor is mounted
with other remote avionics, generally in a nose or tailcone avionics bay or on the
firewall, while the indicator unit is mounted somewhere in your crowded panel. The 9900
indicator is 3.26 inches wide and 1.5 inches high and it about 9 inches deep, making it
easy to find panel real estate, but hard to find a spot that provides adequate depth
behind the panel. My panel is so tight that the only place I could find to mount the TCAD
display was on the center console aft of the throttle quadrant certainly not the ideal
location because it requires that I look down to read the alphanumeric display.
The processor and display are cabled to each other, to the transponder, and to the top-
and bottom-mounted antennas. Both antennas are required to ensure that your airplane
structure won't blind the avoidance system. The 9900B uses different (directional)
antennas than any of the other TCAD models because the 9900B has to resolve the direction
of the threat. In order to do this, the 9900B uses more sophisticated (and expensive!)
antennas and two additional receivers in the remote mounted box.
TCAD 8800-series display/processor.
The new, lower-cost 8800-series TCAD is all contained in one panel-mounted box,
simplifying the installation a bit, but it still requires two antennas. The panel-mounted
box is standard width, so if you have some radio room left it will fit nicely in your
Installation involved fabricating
a second avionics shelf.
When all was said and done, total installation time for my plane was about 125 hours.
(That's more than three man-weeks!) According to Ryan International, they expect between
50 and 100 hours to be more typical. There were several reasons that my installation took
longer than most. To begin with, Aerostars are tight and hard to work on. In addition, the
avionics shelf in my Aerostar was full and so the shop had to fabricate a second one.
Finally, there was all the nonsense with my local FSDO, which I would guess added about 25
hours of extra work, plus the DER charges. Hopefully not all FSDOs are this demanding.
The TCAD is STCd for the Cessna 414 and most installations on other airplanes are done
referencing that STC. I would also guess that the second Aerostar in this neighborhood to
have a TCAD installed would benefit from the experience the FAA had with mine and the
installers could use some of the drawings and things again. All of this adds up. It costs
to be first.
Choosing Among the TCAD Models
There are five separate TCAD models available, two self-contained 8800s, and three
remote-mounting 9900s. Ryan offers a complex matrix that
compares the features of each model but to my way of thinking, it's actually pretty
simple to decide which model to buy.
The first thing you have to decide is whether to buy an 8800-series or a 9900-series.
The 8800-series is much less expensive, but cannot be upgraded to provide
direction-of-threat information. If you can live without that little arrow, my suggestion
would be to purchase the most basic TCAD (the 8800 Silver model, $4,995) and save yourself
about nine grand.
The TCAD 8800 Silver gives you the basic traffic warning information you need:
the altitude of the threat aircraft relative to your own (e.g., 100 feet above, 700 feet
below), and the approximate distance. For a thousand bucks more ($5,995), the 8800 Gold
adds a transponder code readout and a few other goodies, but nothing you can't live
without. Besides, the lower-priced Silver model is easily upgradable to the Gold if you so
The most basic of the TCAD 9900-series lists for $7,995 and
offers similar capabilities to the 8800 Gold but in a remote-mounting package. The 9900A
goes for $9,995 and provides customized "shield size" (discussed later) plus a
pleasant female voice that advises you of "Traffic" rather than just a beep.
Finally, the top-of-the-line 9900B costs $13,850 and is the only TCAD model that provides
direction-of-threat information. Once again, any of the lesser 9900-series units can be
upgraded to a 9900B.
Frankly, it seems to me that there are really only two TCAD models worth considering.
If you can't justify the cost of the direction-sensing 9900B ($13,850), I'd suggest going
with the low-end 8800 Silver ($4,995). To my way of thinking, the in-between models don't
seem to offer the added functionality that their incremental price commands. To make a
long story short, 8800 Silver gives you basic alerting with the threat's altitude and
approximate distance, and the 9900B adds direction-of-threat information and the ability
to display threats on an ARGUS moving map display if you have one. Your choice.
Flying With The TCAD
The TCAD installed in my Aerostar is the 9900B which
has all the bells and whistles. Its panel-mounted indicator has a main screen and a
secondary side screen, both of which comprise 20 LED cells to tell you what's going on.
The TCAD defines a "shield size" which it uses to determine when it should
alert you to traffic. When traffic enters your shield a tone sounds and the display tells
you about the "intruder." The 8800-series and the basic 9900 alert you with a
tone, while the 9900A and the 9000B have a female voice that says, "Traffic."
The 9900A and the 9900B TCAD defines three shields for you that can be modified by the
user, while the 9900 has one fixed shield size (the Enroute shield). The Enroute shield is
plus or minus 2,000 feet and 3.0 iNM.
"iNM" denotes Indicated Nautical Miles, and is the TCAD's best guess on how
far away the traffic is, based on the strength of the received transponder reply. This
guess will be most correct for general aviation transponders, but will show airliners
(which use higher-power transponders) to be closer than they really are. The Standard
shield is plus or minus 1000 feet and 2.0 iNM, and the Terminal shield is plus or minus
500 feet and 1.0 iNM. The 8800s have either 3 or 4 different fixed-size shields.
When the TCAD is powered up, it enters Ground Mode. To avoid nuisance indications from
taxiing aircraft and other ground traffic, Ground Mode limits its range to 1.0 iNM and a
height of 1000 feet above you (presumably there will be no aircraft below you). In
addition traffic at and below 100 feet above you will not be displayed. Approach Mode is
similar to Ground Mode in that the TCAD eliminates warnings from aircraft on the ground.
You must enter the elevation of the airport you are approaching for the TCAD to use
The more expensive TCAD systems allow you to set custom shield parameters if you want
to. In my flying, I have not found it necessary to modify the factory settings, but I do
use different shields for different segments of the flight. In some busy terminal areas,
if you use the Enroute shield, the TCAD will point out too many targets; using the
Terminal shield reduces the number of targets to a more manageable number.
When the TCAD is searching for traffic, but not finding any within your chosen shield,
the 8800 Gold and the all of the 9900-series units show your current altitude and
indicates that it is searching. The screen on the right will show if you have selected the
altitude alert feature. The altitude alert feature allows you to set a desired altitude
you are climbing or descending to. When you reach 500 feet away from this target altitude,
a tone will sound. After you are level at this target altitude, the tone will sound again
when you deviate from this by 200 feet. When the altitude alert function is enabled, a
small "a" is displayed on the right side display. While not quite as good as a
good altitude alerter system, this TCAD feature is useful. I would prefer a slightly more
penetrating tone for altitude deviations, but otherwise it is a worthwhile feature.
Paul Ryan's philosophy of collision avoidance is simple: aircraft cannot collide if
they are at different altitudes. Using this principle, you should either see the traffic,
or make sure you are at a different altitude than the threat aircraft is. All of the Ryan
TCAD models even the lowest-cost one display the altitude difference between you and
the threat to be certain that you will not have a collision, on the theory that altitude
separation is the only sure way. Since the TCAD is reading pressure altitude from both the
threat's altitude encoder and your own, the altitude differential shown on the display is
independent of any altimeter setting you or the threat may have entered. It does assume
that both encoders are working correctly and calibrated accurately. An indicator on the
TCAD display tells you whether your altitude separation in getting larger or smaller.
Ryan suggests that if you have a threat that is getting closer and your altitudes are
the same, then you should climb or descend to eliminate the chance of a collision. If my
TCAD shows that a threat is at my altitude and the indicated distance is getting smaller,
I start to worry. Unless I can spot the intruder, I will change altitude by 100 or 200
feet to eliminate the possibility that the traffic is overtaking me from behind or is
somewhere else I can't see.
All pilots know that they are much less likely to have a midair collision if they are
actively looking outside for traffic. The best thing about the TCAD is that it reminds you
to look outside, and tells you when you should be looking in earnest. Like most of the
traffic pointed out by ATC, you are not likely to see all of the threats the TCAD
tells you about. This does not mean that the TCAD is reporting traffic that doesn't exist,
it just means you didn't see them because they were behind you, obscured by the haze or
whatever. If they had been in front of you, or on a near collision course at your
altitude, and you were looking hard, I believe that the TCAD would give you a good chance
of seeing and avoiding that traffic.
|| (9900 B only)
All TCAD models receive, decode and display traffic from transponder replies within
your shield. All models report the threat's relative altitude and approximate distance.
The 9900B uses two extra receivers and a more complex antenna system to resolve the
direction of the threat, and displays this information by means of an arrow on the display
that points to the threat in 45-degree increments.
When a threat enters your shield the alert tone or voice sounds, an annunciator light
is lit and the panel mounted unit displays the intruder's altitude difference from you and
his indicated distance. Next to the altitude difference is an indicator telling you if the
altitude difference is increasing or decreasing. The display provides a variety of useful symbols that help you assess the
When traffic gets within 500 feet vertically and within 1.0 iNM, the TCAD generates a
repetitive beep to get your attention. The beeps increase in frequency if the traffic gets
within 300 feet and 0.7 iNM. By this time, your head is really on a swivel as you scan for
Some Experiences Flying With TCAD
Ideally, the TCAD display
should be mounted in a position that makes it easy for you to shift your eyes between the
display and your outside traffic scan. Unfortunately, that was not possible in the limited
space available in my Aerostar's crowded panel. The TCAD wound up being installed on the
center console, where I have to look down to see it.
The good news is that even with this poor positioning, I found that with some practice
I can look at the TCAD and very quickly look back outside. If you know what you are
looking for on the TCAD display, only a very brief glance at the readout is required. When
traffic enters my shield, an annunciator light mounted directly in front of me and at eye
level lights, a female voice calls "traffic," and a tone sounds. I then quickly
glance down to the TCAD, absorb the information on altitude, distance and direction and
then look outside to see if I can see the threat.
Usually I can find the target visually. Flying over the Everglades into my home base of
BCT (Boca Raton, Florida), for example, I heard a King Air call in on Unicom also
reporting west of the airport. There were two of us, converging on BCT, both at about the
same speed. Even if we were separated now, we would get closer together as we approached
the airport. The TCAD registered a threat, pointed 45 degrees to the right of the nose,
and indicated the traffic was 2.5 miles away and 200 feet below me. Bingo! There it was.
From here it was easy to fall in behind (even though everyone knows Aerostars are faster
than King Airs!) and follow him into the pattern. Neat, easy and safe.
Another flight from PWM (Portland, Maine) to N71 (Mt. Joy, Pennsylvania) took me west
of Boston. The weather in my vicinity had just cleared from a frontal passage, but BOS was
still low enough IFR that they were holding airplanes all around the area waiting their
turn for the approach. As we flew about 35 miles west of the coast, the TCAD faithfully
pointed out all the holding aircraft as they circled the intersections surrounding the
area. Boston was so busy that VFR advisories would have been out of the question, and
fortunately for me, I had my own little box telling me where the potential traffic was.
Continuing on to N71, I entered the pattern with the knowledge that I was the only
plane in that pattern because the TCAD was silent. The TCAD can be as helpful quiet as it
can be when active. Remember that it is a "big sky" out there and that most of
the time the TCAD will be silent. I believe it was Burt Rutan that said, "Next time
someone tells you about the crowded sky, tell them to go outside and look up!" The
proof of this is that the TCAD is silent most of your flying time which adds enjoyment to
the flight. When it wakes up and announces "traffic," it's time to start looking
When entering a busy terminal area, the TCAD can become too busy. The processor
is capable of showing three threats at once and tracking more than 50 threats, determining
which three are the most critical and displaying them. Although it requires some button
pushing to see more than the threat it considers the most serious, with practice you can
manage to keep track of the secondary and tertiary threats as well. When there are too
many threats, switching the shield from Enroute to Terminal usually solves the overload
Flying from Denver, Colorado, to Las Vegas, Nevada, over some of the more uninhabited
part of the U.S., the TCAD was mostly silent. The 9900 A&B have an
"Unlimited" setting which sets the shield size to plus or minus 10,000 feet and
6 iNM. Using this setting finds traffic that is definitely no factor but helps to break
some of the monotony of just cruising over the desert. Using the
"identification" feature (available in all but the lowest-cost 8800 Silver
model) allows you to see the transponder code the threat is squawking, or the tail number
if the traffic has a Mode S transponder (as all TCAS-equipped aircraft do). It isn't
unusual to see N970AA cruising 9,000 feet above you this would be some American
Airlines jet which wouldn't show on any shield size except "Unlimited."
During these low traffic quiet times, the TCAD can serve its purpose the best there's
no traffic to worry about. Here when we are most complacent is when we are ripe for
trouble. The TCAD's ability to "wake us up" is one of its most valuable
attributes. In the '50s, it was a mid-air collision of two airliners over the sparsely
populated Grand Canyon the spurred the radar-based ATC system we have today. We all know
we have to be vigilant in busy terminal areas, but at some time during most flights we
kick back and relax a little. The TCAD could bring you back to full attention if a threat
enters your shield.
I use the altitude alert feature to remind me of where I am climbing or descending to
should I forget. As a bonus, it also shows the altitude you are sending to ATC from your
own altitude encoder. In one case, it alerted me to a problem when my encoder became
intermittent instead of the aircraft's altitude, the TCAD display showed only
I recently spent a lot of time flying a friend's Cessna 340 that did not have a TCAD
aboard and I found that I missed its friendly "traffic" alerts. The TCAD adds a
lot of relaxation to a flight when there are no alerts showing. I realized while flying
the 340 that traffic was possible at any time. This doesn't imply that it is impossible
for traffic to enter your shield without the TCAD responding. That could happen if there
is a fault in the intruder's transponder or encoder, there are no ATC facilities nearby to
interrogate the other transponder, or there could be a malfunction in the TCAD itself.
But, when the TCAD is quiet, it is certainly less likely that there is a collision
I Like The TCAD, But...
The bottom line
here unfortunately is the bottom line. The TCAD is undeniably expensive. Even the
least-expensive 8800 Silver (at $5,000) is not exactly cheap, and in an era of $500
handheld GPSs, it seems like a lot of dough for what ought to be a fairly simple box. Add
$750 for installation and another $750 for antennas, and even the least-expensive TCAD
installation will set you back almost $7,000.
On the other hand, the price is in line with some of the newer multifunction GPS
navigation units being introduced. The TCAD is definitely leading-edge electronics for
your plane, and is priced accordingly. The top-of-the-line 9900B lists for $13,995 (also
not including antennas) and will cost about $1,000 to install. Nobody ever said airplanes
were cheap. The TCAD adds to this expense burden, but without a doubt also adds a level of
confidence and safety that surely enhances the value of your airplane and the experience
of flying it.
The TCAD is clearly not a required piece for your panel. But neither is that second
ILS, radar altimeter, altitude alerter, fancy clock/timer, ANR headset, stereo music
system and lots of other stuff that make your job easier and the flying safer and more
pleasant. The Ryan TCAD adds some serious functionality to your airplane.
When I buy scuba diving equipment (which ain't exactly cheap, either), my wife always
asks if what I am buying involves breathing. When I say yes, she says, "buy it."
When you go to write the check for the Ryan TCAD, ask yourself if it involves avoiding
midair collisions. If it will help keep you and other flying machines from running into
each other, you might just say, "buy it."