Avionics ForHomebuilt Aircraft

By PETER LERT

I he nature of homebuilt aircraft, and ofour movement in general, has changedsignificantly during the last decade or so.As recently as ten years ago, most home-builts were still either relatively low-per-formance "fun aircraft" or, in some cases,high-performance special-purpose ma-chines like the Pitts - in either case,generaly built "from scratch" by dyed-in-the-wool enthusiasts. While there had al-ready been some exceptions to this rule,such as the very successful VariEze and,at the other end of the success scale, theBD-5, the general trend among EAAerswas toward keeping their cherishedhomebuilts as highly specialized recrea-tional machines, while relying largely onconventional production "spam cans" formore mundane "point A to point B" trans-portation - if they could ever find timeaway from their workshops for travel any-where but to Oshkosh.

In keeping with this, the avionics instal-lations - such as they were - of home-builts of that era tended toward the basic.After all, if the primary use of yourcherished bird would be not only VFR,but within a few miles of the home'drome, it made more sense to put youravionics dollars into the panel of yourWichita Wonder, Kerrville Kutie, or VeroBeach Vampire than into your "funairplane."

Now, though, the picture has changeddrastically. The most active area of home-building is in the area of "superkits" - air-craft which are not only orders of mag-nitude easier to build (and often, alas,more expensive) than their predecessors,but also vastly more sophisticated andbetter performing. Indeed, several amongthem offer levels of cross-country perfor-mance exceeding that of corporate tur-boprops. Combine this with the fact thatthe "Big Three's" future in affordablehigh-performance recip-powered aircraftis about as viable as that of the pterodac-tyl, and it's evident that the homebuilt air-craft is no longer considered an adjunctto factory-built aircraft, but rather an al-ternative - if not, indeed, an outright re-placement.

With this has come a change in missionand equipment requirements. Homebuiltsare no longer just "fair weather friends";no small number are used for long-rangeIFR transportation. Avionics develop-ment has also kept pace, both in terms ofperformance per dollar - while radios maycost a bit more than they once did, theycan do a LOT more and, inevitably, inwhat the FAA requires us to carry and

A VFR panel with a handheld radio clipped to the side.

use for almost anything but the mostbasic VFR flight in uncongested areas.

In this article we'll look at the range ofavionics available to today's homebuilt,as well as trying to define what might be"typical" avionics packages for variousclasses and typical utilizations of home-built aircraft.

THE KIND OF AIRPLANEPAUL LIKES .. .

Let's start at the lower end of the range:the "low and slow" VFR-only aircraft, includ-ing antiques, ultralights, and many classicsthat were once as much the epitome of EAAas the Cub was of light aircraft in general.

"LET'S TALK. . ."

Obviously, the most basic radio for manysuch aircraft is a simple comm set. Unfortu-nately, nowadays even "simple" means notonly that it should have the full 720 channels,but also that it must meet the recent stringentFCC requirements for frequency stability.This rules out many of the used comms andnav-comms of yesteryear such as King KX-160s or Narco Mark XI Is, which were oncesuch bargains.

Take heart, though, for those needingnothing more than "basic comm", includingthe pilots of gliders and balloons, there's awhole crop of low-cost handheld radios fromsuppliers including King, Terra, Narco,

The Argus series of moving maps.SPORT AVIATION 23

Another VFR panel, this one with a panel mount radio.

ICOM, Sporty's and others. Prices rangefrom about $250 to almost twice that, de-pending on features - including, in someunits, basic VOR navigation capability, ofwhich more shortly. While the handhelds'output power is modest, it's quite adequatefor VFR uses, particularly when the radiosare used with a decent airframe-mounted an-tenna rather than the "rubber ducky"supplied as standard.

Another advantage of handhelds, ofcourse, is their independence from aircraftelectrical power (although all of them canalso be operated on aircraft power, some-times with modest gains in performance).This means that an "installation" for an air-craft without an electrical system might benothing more than an antenna and a conve-niently located mounting clip or patch of self-stick material to secure the radio. Note, how-ever, that many early aircraft - and, morerecently, ultralights - have no provision forpreventing electrical noise from their ignitionsystems from interfering with radio recep-tion; fixes can range from shielded ignitionharnesses to elaborate enclosures andnoise suppression systems for some of the"dirtier" two-strokes.

WHERE AM I?"(Part 1)

During the Golden Age of Aviation, whenmost airplanes performed about the way ourmodern "low 'n slow" ones do now, basicnavigation consisted of the now almost lostart of pilotage - a fancy way of saying "look-ing out the window with your thumb on themap." Get confused in the midwest, whereall the little towns look the same, and youcould always buzz the water tower to readthe name. Nowadays, though, all the littletowns seem to be called "Senior Class of'91", so somewhat more sophisticated navi-24 MAY 1991

gation capability is helpful even for the basic-VFR types.

Once again, the handhelds with VORcapability can be quite adequate. It's an"either/or" proposition - they can be used fornavigation or communication, but generallynot both at once. The first ones to offer VORcapability had only digital readouts of theVOR radial, which could require a bit of men-tal gymnastics (or a more flexible thumb onthe map) to figure out where you were. Somecurrent ones have actual left-right course de-viation indicators (GDIs), allowing more intui-tive navigation - although none are certifi-cated for IFR navigation, and I'd only want

to shoot an approach with one "in extremis."

"WHERE AM I?"(Part 1a)

The last few months have seen a very in-teresting development in the LORAN field -very low cost handheld LORANs from Voy-ager (a division of Micrologic) andSportNav. I haven't yet had the chance toevaluate any of these little units, which costin the $300 range and will work for severalhours on their own AA penlight cells, but ifthey work as well as their manufacturersclaim, a very basic airplane's complete navi-gation and communication needs might wellbe met simply by a pair of handhelds: acomm and a LORAN. Even those of us flyingrelatively heavy iron (or those, such as I, whodo a lot of foreign or overwater ferry work ina wide variety of aircraft) might want to havea pair of such handhelds stashed away inour flight bags in case of radio or electricalfailure.

THE BASIC OUTFIT

Moving up the scale of aircraft a notch, wefind what we might call "moderate perfor-mance" airplanes - those flown primarily day-VFR, but often used for fairly significantcross-country flights, occasionally at nightand/or even in the clag. I'm not necessarilytalking "hard IFR" here, with approachesthrough heavy weather right down tominimums - but how many times have youhad to put off departure for hours, waiting fora layer to burn off, when you could have filed"IFR to VFR on top" and cancelled thirty sec-onds after takeoff, then flown serenely abovethe clouds until descending, possibly intopretty good VFR underneath, at the destina-tion?

In this class, I'd include airplanes like RV-4s and T-18s, Rutan's various and sundryfiberglass pickle forks and their derivativesand descendants, and numerous others.Some, of course, are very heavily equipped,but most are constrained by both overall pro-

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ject cost and, in some cases, limited instru-ment panel "real estate" to relatively basicavionics suites. If only VFR operations arecontemplated, a single comm and a LORANmight be sufficient. For IFR, though, a realis-tic installation would include at least comm,VOR nav, localizer if not full ILS, and, nowa-days, a transponder. Loran would be a highlyuseful addition, while a single dual-purposehandheld can provide backup if necessary.

BASIC NAV AND COMM

Not too long ago, the "standard radio" fora lightplane was the so-called "navcomm",incorporating both the comm transceiver andthe nav (VOR/ILS) receiver. While somemanufacturers, notably King and Narco, stillput out such "all in one" boxes in the $3,500class, the trend has been toward separatenav and comm radios.

Among the older available units used, theKing KX-170 and -175 series have a goodreputation for ruggedness. While you canfind used Cessna (that is, ARC) radios atattractive prices, their reputation is less thansavory, and support and service increasinglyexpensive and difficult to find.

The erstwhile Narco "Centerline" radiosare still pretty decent; for those short onpanel space, the separate nav receiver (stillin production in an updated version) com-bines the complete receiver and indicator ina single 3-inch panel hole.

If your resources are sufficient for newradios, I'd suggest looking at the recentTerra offerings as well as those from Kingand Narco. In fact, I must admit that I'm per-sonally quite partial to Terra, particularly forhomebuilts; not only is the equipment rug-ged, light, compact, and relatively inexpen-sive - a complete nav-comm including glide-slope and indicator costs "only" $2,195 - butDick Donovan and his crew at Terra havelong been enthusiastic EAA supporters. Thestandard "form factor" for Terra radios is acouple of inches high and exactly half thewidth of the standard radio rack; thus, oneversion of the Terra "navcomm" fits into thesame space as some other manufacturers'nav-only or comm-only radios, plus an exter-nal indicator; alternatively, the wholeshebang, including indicator, fits into thesame space as an older Mark XII or similarradio, with the frequency selectors stackedvertically and the full-size indicator next tothem.

DO IT YOURSELF

Given our EAA orientation, we shouldn'tforget that longtime EAA supporter RadioSystems Technology (RST) in California of-fers a wide line of products - including a com-plete navcomm radio - as a do-it-yourself kit.If you have the interest, time, and a minimumof ability, you can cobble up your own equip-ment at very low cost - not to mention thefact that you'll learn a lot, and it's fun, be-sides. Completed radios are sent back toRST for final alignment and certification.

TRANSPONDERS

The transponder has just about become afact of life in any but the most bucolic rural

Today's standard sport aviation avionic package . . . a radio, transponder and loran.

areas - and while diehard anti-big-govern-ment EAAers may call me a heretic, I've got-ten to the point at which I'm ready to acceptthe requirement. Let's face it - transpondersaren't all that expensive anymore (althoughthey may be once again as Mode S becomesa requirement sometime in the future), andI'm willing to pay a certain amount of moneyfor a gadget that not only makes it easier forme to operate - such as going under orthrough ARSAs and TCAs instead of havingto fly around or over them - as well as possi-bly making it less likely that I'll be center-punched by an airliner while its crew is "headdown" reading a checklist.

With the transponder comes, nowadays,either an encoding altimeter or a separateencoder. Once again, this is someting that'snot all that expensive anymore, starling ataround $225; sooner or later most of us willhave to have one anyway, and even nowsome of them - notably II Morrow's whenused with certain of that firm's LORANs -can provide other useful capabilities like ver-tical navigation (VNAV), altitude alerting, etc.(In fact, low-cost altitude deviation warningdevices are available now; at about $100,they can cost less than a single violation re-ported by the "snitch patch" in a TRACON'sradar computer.)

LOOK, MA, NO CAVITIES

There are lots of used transponders onthe market, and buying one at a low pricemight make sense - particularly if that's theonly way you'll be able to operate out of yourhome 'drome near a TCA or ARSA, and ifyou intend to replace it within a couple ofyears with a new one anyway.

There's a problem with used transponder,though, and one that'll gradually get worse:their output stage uses a particular type ofvacuum tube called a "microwave cavity",and only one firm makes them anymore.Thus, we're faced with a critical single-source component that has a limited life

span and is expensive to begin with . . . andsooner or later the supply of replacementcavities is likely to dry up altogether.

At this writing, both King and Terra makesolid-state transponders that operate inModes A and C - the "conventional" modeswe're used to. They're not cheap - the Kinglists for $3,365, the Terra for $1,195 - butthey should keep playing for a long, long time. . . and they're fixable if they quit. The Kingunit is the standard 6-1/4" radio stack widthby a couple of inches high and includessome neat "bells and whistles", like the abilityto return to the standard VFR 1200 code atthe push of a button, or to display the altitudereported by your encoder on its front paneldigits; the Terra is half the width.

LORAN WARS - OR •WHERE AM I? (Part 2)

Currently, the "hottest" area of avionics de-velopment has been LORAN, with variousmanufacturers vying to add capabilities andoperating convenience. Most recently therehave been two significant developments:IFR certification (at least enroute and termi-nal, if not yet for approaches) of some units,and - about the time you read this - additionof two new LORAN transmitter chains toclose the "mid-continent gap" and provide re-liable LORAN coverage throughout the"lower 48" states. (In fact, one manufacturerhas gone so far as to call their newestsoftware version the "forty-niner", sinceHawaii also has pretty good LORAN cover-age - not to mention that the firm is based inthe San Francisco Bay area, and is hence a'Niners fan. For that matter, most of Alaskasouth of the Brooks Range also has decentLORAN coverage.)

Actually, we EAAers can pat ourselves onthe back as leaders in the so-called "LORANrevolution." Back when the conventional wis-dom was that LORAN was a marine systemand hence not suitable for aircraft, many ofus were happily and legally flying around

SPORT AVIATION 25

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with marine LORANs in our experimental air-craft - where they worked just fine, thankyou. (A similar phenomenon is currently oc-curring with GPS satellite navigation, ofwhich more later.) In the meantime, ofcourse, "official" airborne LORAN has be-come big business, with 'lull line" avionicsfirms like Bendix King and Narco as well asdedicated LORAN manufacturers like II Mor-row, ARNAV, and Northstar all vying for yourdollar.

FRILLS AND FEATURES

Over the last ten years or so, LORANshave steadily gotten smaller, more capable,and less expensive, particularly in terms ofperformance per dollar. I vividly rememberthe first one I used on transatlantic cross-ings; it was the size of a fat Jepp case, cost$8,000 back when money was worth some-thing, and getting a position fix required sev-eral minutes of delicately twiddling knobswhile watching "Chinese TV" on an oscillo-scope, then transferring the results to specialmaps with an overlay that looked like theweb of a spider on LSD. A few years later,my II Morrow "Avenger" was the size of askinny Jepp case, cost under $2,000, andread out latitude and longitude directly. Bynow, the "standard" LORAN can cost fromabout $1,000 (for a very basic, but still en-tirely functional, "no frills" unit) to six timesthat; starting at about $2,000 you'll have abuilt-in database containing at least all theairports in the USA; many are much moresophisticated. Most units fit the by-now stan-dard 2 inch by 6 inch radio stack form factor.

To cover the whole range of available unitswould require an entire additional article -one probably larger than this one! Suffice itto say that there are now LORANs for almostevery purpose and almost every pocket-book, including used ones - as feature-hun-gry EAAers succumb to what Stewart Brandcalls "the tyranny of the new", earlier modelsshow up at radio shops, not to mention EAAChapter meetings or the Oshkosh Fly Mar-ket, at attractive prices.

CAVEAT EMPTOR

Note, however, that for some not everyused LORAN is that great a bargain. If yourflying is generally in one specific area, youcan save significantly by getting an older unitwithout a built-in database (or, if you have alaptop computer, you can have not only adatabase, but a moving map display - I'lltouch on that a bit later). On the other hand,if you contemplate flying in what used to bethe mid-continent gap - basically a stripabout 400 nm wide from Canada intoMexico, starting at about the eastern edgeof the Rockies, plus most of Arizona and vir-tually all of New Mexico - you should beaware that most of the older LORANs cannotbe field-modified to work with the new NorthCentral and South Central LORAN chains.By the time you have one of these units fac-tory modified, you might have been better offgetting a new one to begin with.

THE CERTIFICATION ISSUE

Some LORANs, both old and new, can becertificated for enroute and/or terminal IFR.This generally requires not only one of theIFR-certificated units, but a certain amountof jumping through local FAA hoops by youand your radio shop. If you contemplate ex-tensive IFR flying - particularly if you want tolegally file the /R suffix - you may wish toconsider one of these units. IFR LORANsgenerally cost more than their VFR counter-parts; moreover, they often offer LESS in theway of nifty features, since certificating allthose features would be prohibitively com-plex and expensive.

There's some merit to the idea that an IFR-certificated LORAN can replace or supplantother navaids, but there are gray areas. IfCenter asks for your DME from a VORTAC,you're probably legal giving him the distanceyour LORAN indicates - at least enroute. Onthe other hand, unless your unit is certifi-cated for approaches (none are at this writ-ing, though some are getting close), you

probably can't use it in lieu of DME or ADFfor approaches requiring those components- only for LORAN approaches, of which onlyhalf a dozen are published so far, and thoseonly on an experimental basis.

THE OLD HEADING PLOY

Although actually beyond the scope of thisarticle, this is the place to mention an entirelylegal "cheat" that can secure you most of theadvantages of an IFR-certificated LORAN orRNAV without actually having to have one:once you're handed off from the departureagency to Center, check the indication ofyour LORAN for the correct heading to thedestination, then ask Center if you can flythat heading - "N123X requests heading 125degrees to Louisville." If Center approves,they'll say something like, "N123X, fly head-ing 125 until receiving Louisville." As long asCenter says the magic word "heading",you're legal - even IFR - even if everythingquits but the whiskey compass on thewindshield frame. Of course, you can cross-check against your non-IFR LORAN or othernavaids as much as you like . . . just be sureyou have enough in the way of legal navaidsto get down at the destination or your alter-nate when and as necessary.

FULL HOUSE RADIOS

At the top of the current homebuilt totempole we find the high-performance cross-country machines - Glasairs, Ventures, Lan-cairs, Cirruses (Cirri?), and the new designsthat will inevitably arise in this class. Theseare the airplanes that may often be flown"hard IFR" for personal or business travel.Many perform right up with corporate aircraft;many require similar avionics capabilities.

NAVCOMM FOR FULL IFR

Basically, there's no difference in basicnav and comm requirements between theseand lesser aircraft. Given the IFR mission,however, common sense dictates two ofeach: two comms, two VOR/ILS receivers,at least one - preferably both - with glide-slope. Somewhere along the line, a markerbeacon receiver will come in as well, butthat's a pretty minor item as far as size,weight, or expense are concerned; in manycases it's part of the audio switch panel.

ADF, DME AND RNAV

In production airplanes, the standard "fullhouse" IFR package has always been con-sidered to include dual navcomms, trans-ponder, ADF and DME. In later years, top-end outfits often also included RNAV - equip-ment that could electronically "displace" aVORTAC to a different location. Do we needall that stuff today?

ADF - For some pilots, ADF is indispen-sable - particularly during World Series orSuperbowl time! For others, it gathers dustin the panel. Nowadays, I'd install it onlyunder certain circumstances - for instance,if I planned flights in areas like northernCanada where it's the only navaid available,

or if I foresaw a need to (legally) fly NDBapproaches. Speaking entirely unofficially,now that the North and South CentralLORAN chains are going in, I'd probably usea good LORAN with a waypoint at the NDB,monitoring the approach with the ADF - butto be legal, you still need an ADF. It's alsohandy as an ILS orientation aid at placeswhere there's an outer compass locator - al-though, again, in the real world I'd probablyprefer LORAN.

DME - Much the same holds true of DME- in general, at least in the Lower 48, a goodLORAN will do the job just as well. Onceagain, though, if you're going to shoot VOR/DME approaches, you need one to be legal.Note that like transponders, older DMEs usea hard-to-replace cavity or "lighthouse" tube,so if you're going to buy one, look for a morerecent solid-state type - and be prepared tofind yourself on the wrong side of $2,500 ifyou get a new one!

RNAV - RNAV is a special case; by now,at least one of its uses (the ability to fly point-to-point direct) has been almost entirelysupplanted by LORAN. On the other hand,if your planned operations include flyingRNAV approaches (for instance, if that's allthat's available at your home field), you haveto be legal to have one; note that, at leastfor the present, the FAA makes a clear dis-tinction between RNAV and LORAN ap-proaches, and you can't legally fly the formerusing the latter equipment, no matter howwell it may appear to work.

One type of unit is worth looking into:an integrated VOR/ILS/DME/RNAV systemsuch as the Bendix/King KNS-80 or theNarco NS-800. These units are pricey new(about eight grand for the King, five for theNarco), but crop up used at much more af-fordable rates - and cost little or no morethan a separate nav receiver and DME withno RNAV capability. They're both certificatedfor enroute, terminal, and approach IFR, thusallowing you to add the coveted /R to yourequipment type on your flight plan. Person-ally, I'd put the money into the best LORANI could afford first, and a conventional RNAVsecond - but if your operations require RNAVor even just a DME, one of these gadgetsmakes sense when you're planning yourpanel.

Incidentally, while many installers givethese integrated RNAVs pride of place asthe #1 NAV receiver, I prefer to hook themup in the #2 spot. This allows me to use the#1 nav, generally wired to an HSI, as theprimary approach radio; for ILS or VOR ap-proaches, I can then set the #2 RNAV toshow distance to the runway or missed ap-proach point. For those rare RNAV ap-proaches, flying on the #2 radio isn't an ex-cessive hardship.

AUTOPILOTS

What?! Autopilots in homebuilts? You bet. . . and particularly at the high end. Bear inmind that while some of the "hot ships" areterrific travelling machines and carry a fullcomplement of IFR avionics, they're notnecessarily the most stable instrument plat-forms in the sky; in fact, some of them aredownright twitchy, particularly at approachspeeds. Some kind of autopilot - possiblynothing more than a wing leveler - can make

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your life not only easier and safer, but muchmore relaxing.

WING LEVELERS

In fact, let's look at the "lowly" wing levelerfor a moment. This most basic of autopilotsmay do little more than, as its name implies,hold the wings more or less level - but thatalone can make a big difference, particularlyin a hot ship that may slide off into a spiraleverytime you look at a map. You'll often findused ones at good prices at your neighbor-hood radio shop, and they're simple enoughto be easy to adapt to most homebuilt instal-lations. Some can even do a remarkablygood job of following a VOR or LORANcourse when wired to your nav radios.

I should note that a wing leveler can be asignificant aid not only in convenience, butalso in safety for those homebuilts that areflown IFR: since most are wired to the turncoordinator and function entirely electrically,they can generally do a far better job of flying"partial panel" after a gyro or vacuum failurethan we mere humans can. Given the notori-ous unreliability of vacuum systems, I per-sonally would rather spend about the samemoney on a used wing leveler as I would ona new standby vacuum system; both wouldsave my tush in an emergency, but the wingleveler will make my life easier day in andday out.

FULL AUTOPILOTS

Installing a used full-function autopilot in ahomebuilt can be a tricky proposition. Thatsuper deal from the radio shop may turn outto have come from, say, a 310 - so its controlresponses may be tailored for a much largerand heavier aircraft than the one you plan toinstall it in. Setting up an autopilot for a givenaircraft is half science, half black magic - andit's what takes even autopilot manufacturersweeks sometimes.

I should point out that a couple of currentautopilot manufacturers (S-Tec and Century,both in Mineral Wells, TX) have a record ofsupporting homebuilders. Many Century au-

topilots were developed by the legendaryJim Younkin, whose Stearman and TravelAir regularly wow the antique crowd, whiletheir longtime shop foreman Charlie Hoefel-man's cute little "Schatzie" biplane resem-bles nothing so much as a transistorizedStaggerwing Beech. Across the field, S-Tecis alleged to sell just about as many systemsto the homebuilders as they do to the man-ufacturers of "real airplanes." Stoddard-Hamilton Aircraft, for example, has a dealwith S-Tec to get autopilots at good pricesfor Glasair builders - and S-Tec has enoughexperience with Glasairs to provide systemspreconfigured for that aircraft's flying qual-ities.

RAZZLE-DAZZLEBELLS AND WHISTLES

By now we've pretty much covered therange of what you might need for almost anysort of flight operation, from "around thepatch on nice days" to "across the continentin any weather." Of course, there's still lotsof other stuff in the "gee, I'd love to have oneof those" category, as well as new equipmentjust starting to show up on the horizon; I'lljust hit a few of the high points:

INTERCOMS - Actually, almost any air-craft (except maybe balloons or gliders) canbenefit from a good intercom system; thereare many on the market, including homebuiltkit versions from RST and others. As ScaledComposites test pilot Doug Shane puts it,"Life's too short to fly without tunes"; manyintercoms will now interface with portablecassette or CD players to help pass thosecross-country hours.

THUNDERSTORM DETECTION EQUIP-MENT - Personally, I'm a devout coward; ifAM Weather shows cumulus boomboomuswhere I'm headed, I'm happy to wait on theground. For you "gotta go regardless" types,both 3M Stormscope and Insight Electronicsoffer passive (i.e. nonradar) lightning detec-tion systems. The Stormscope has proveditself well over the past 8 years or so, theInsight "Strikefinder" is too new to judge, al-though preliminary reports are very promis-ing.

SPORT AVIATION 27

GPS - This satellite-based navigation sys-tem is the newest thing on (or rather above)the horizon; its advantages over LORAN in-clude the fact that it works anywhere in theworld and its relative imperviousness toweather factors (T-storms, precipitation sta-tic, etc.) that degrade LORAN performance.At present, dedicated panel-mount systemssuch as the fabulous database-equippedTrimble LNS-3000 are still in the $8,000class; however, portables and even hand-helds like the Trimble TransPak, the Magel-lan, and the ProNav are hovering around the$2,500 mark.

I've used them overseas (out of LORANcoverage) with excellent success. For themoment, and particularly now that the Northand South Central LORAN chains are com-ing online, the same amount of money getsyou more features with LORAN; as long asI'm going to fly in LORAN coverage, that'swhere I'd put my bucks at present. Keep aneye on developments, though; I think GPSwill get considerably cheaper and more cap-able in the not-too-distant future.

MOVING MAP DISPLAYS - With these,we've come full circle back to the "thumb onthe map" system of navigation - only nowboth thumb and map are electronic, drivenby position inputs from a LORAN or GPSsystem.

Eventide Electronics makes the Argusseries of panel-mounted moving map sys-tems, using a CRT for display and costingfrom $3,000 up depending on size and op-tions. Noted LORAN manufacturer ARNAVSystems makes the NV-1000 and NV-2000systems, providing a highly versatile movingmap and nav management system with aflat display panel in a kneeboard-size unit -for $10,000 to use with an existing LORANreceiver, or $24,500 including its own multi-chain LORAN sensor.

At a more affordable end of the spectrum,Peacock Systems provides software for$695 that allows any IBM compatible laptopcomputer to interface with most LORANs toprovide not only a moving map, but also fulldatabase capability. Since quite a few of usare already schlepping laptops around to useas DUAT terminals or for other purposes - infact, this article was written on one! -Peacock's "LapMap" is quite a bargain. Oneword of caution, though: some laptops, par-ticularly older ones, put out quite a bit of elec-trical noise at a frequency that some LO-RANs - again, generally the older ones - aresensitive to. In my case, for example, I hadto add a couple of ferrite rings to the interfacecable to keep my old Zenith Z-181 laptopfrom bothering an Azure Long Ranger F/PLORAN.

COLLISION AVOIDANCE - Paul Ryan,the developer of the Stormscope, is probablythe leading expert on "pseudo ranging" - thatis, the science of figuring out how far awayan electrical signal is based on its strength.That's how the Stormscope figures out howfar away lighting discharges are: his latestproduct, the TCAD, does the same for trans-ponder signals to help prevent midair colli-sions.

The $7,000 transponder-size panel-mounted system can't determine direction; itcan, however, determine "pseudo range"and, if both your and the "threat" aircraft areMode C equipped, whether you're at or near

the same altitude and whether your altitudesare converging or diverging. After all, as28 MAY 1991

The author, Peter Lert.

Ryan points out, to collide two airplaneshave to be not only at the same place, butthe same altitude as well.

The TCAD isn't intended to replace "see

and avoid", but if you have room in yourpanel and your pocket, and plan to fly in con-gested areas, you may decide it's moneywell spent.

SUMMING UP

Avionics development is one of the fewfields in which development is even fasterand more frantic than that of homebuilt air-craft, so we're likely to see a whole raft ofinteresting new products in the future - aswell as interesting new aircraft to install them

in. For the moment, though, this may serveas a broad overview of what's available andwhere you might want to use it; I'll try to sumit up in the following table, divided not byaircraft type but according to the plannedmission:

MISSION(Primary)

"rock bottom" VFRUltralights, gliders,balloons, etc.; localflights only

Basic VFR; some X-C(rural areas only)

"Standard" VFR incl.cross-country intoor near TCAs/ARSAs;occasional "light" IFR

"Standard" IFR

"Full House IFR"

"Dream Panel" -or-"everything you alwayswanted . . . except nowyou can only carry enoughfuel for 85 nm ..."

EQUIPMENT(Typical)

handheld comm(possibly includingVOR)

handheld commbasic or handheldLORANpanel-mounted navcommtransponder withalt. encoder; optionalLORAN with or withoutdatabase

2 navcommstransponder/encoderglideslope/markers

2 navcommsglideslope/markersADF, DMELORAN (optional)wing leveler (opt.)

2 navcomms/ILS/GSplus ADF/DME/RNAVplus super LORANplus autopilot, TCADplus whatever elsestrikes your fancy

COST(new eqpt.)$250-500

$600-1,000

$2,000-6,000depending onLORAN

$5,000-8,000depending on newor used eqpt.

$10,000-updepending onnew or used eqpt.

$15,000 - up to"if you have to ask,you couldn't affordit anyway ..."