Tony Bingelis •

PLANNING YOURINSTRUMENT PANEL

Almost any aircraft panel will haveroom for the few mandatory instrumentsrequired by Federal Aviation Regula-tions, specifically FAR Part 91. Just toshow you how little you really need,here is the complete list of the instru-ments necessary for legal flight:

1. An Airspeed Indicator2. An Altimeter3. A Magnetic Direction Indicator

(compass)4. A Tachometer5. Oil Pressure Gage6. Oil Temperature Gage (air cooled

engine)7. Fuel Quantity Indicator (need not

be an instrument)So, if you are really interested in

keeping your airplane as light andspritely as possible, and intend to useit primarily for daytime VFR sport flying,the minimum instrumentation could fillyour needs adequately.

Naturally, finding space for those fewgages is no problem, even in the skimp-iest single seater instrument panel.

Let's face it, though, most of us wouldnever consider such a Spartan instru-ment installation — and therein lies theproblem. If the minimum instrumenta-tion is not adequate for your needs,what would be? Well, there is nothingreally wrong with wanting to add a fewmore of your favorite instruments tokeep you company, and to help youmonitor the attitude and behavior ofyour aircraft as well as the status of theengine. After all, the more you knowabout both, the safer and more profes-sional your flying can become. Well, somuch for rationalization.

Let's Try Some Logical ReasoningSometimes we find the number and

type of instruments we want to or caninstall will be governed by factors overwhich we have little control. For exam-ple, the aircraft might not be equippedwith either an electrical system or a vac-uum system . . . and then there are al-ways financial considerations.

No electrical system? That meansyou will not need to install either an am-

meter or a voltmeter. Nor should you gation and strobe lights, unless you arecontemplate the idea of installing navi- willing to provide some sort of battery

3 1/8LABEL EACH CARD TOREPRESENT AN INSTRUMENTTO BE INSTALLED.

THIN CARDBOARD

MAKE ONE INSTRUMENT RANEL LAYOUT PLANNINGCARD FOR EACH LARGE INSTRUMENT YOU WOULDLIKE TO INSTALL...

AND.ALSO ONE FOR EACH SMALL AIRCRAFT INSTRUMENT.

FIGURE I.

f

45"

2 1/4"(SQUARE)

INSTRUMENT PANEL PLANNING CARDS

SPORT AVIATION 27

power source to operate them. Also, theengine instruments that will be neededmust be the non-electrical type gages.

No vacuum system? Without an en-gine driven vacuum system on boardyou should not entertain the idea of in-stalling any gyro instruments, not evena turn/bank indicator, unless, of course,you are willing to provide an externalvacuum source. That is, a vacuumsource capable of powering one ormore gyro instruments through a ven-turi affixed to the airplane externally. Todrive all three gyro flight instrumentswould require a large 9 inch super ven-turi stuck to the side of the airplane . . .and most builders don't like that idea.On the other hand, you could but prob-ably wouldn't install a set of those out-rageously priced electrical flight instru-ments in place of the more commonvacuum driven gyro gages.

And there is still another limiting fac-tor — space, or rather the lack of instru-ment panel space.

The lack of instrument panel space isnot, ordinarily, a problem found in theaverage two seater aircraft with side-by-side seating, but it definitely is withsingle seaters and tandem seating twoseaters.

An instrument panel 24 inches wideis hardly large enough to accommodatea complete set of gyro instruments,radios, switches and other controls.

Many builders immediately think ofadding a sub-panel to the bottom of theregular instrument panel. You can't,however, arbitrarily do that in order toaccommodate additional gages,switches and radios. For one thing, yourcontrol stick will probably not clear it...and if it does, there is the risk that youwill occasionally skin your knucklesagainst that sub-panel.

Cutting off some of the control stickmay seem like a clever way to solvethat problem. It ain't. The shorter thecontrol column, the more sensitive thecontrols can become as a little move-ment will then yield amazing responses.Many homebuilts are too sensitive tocontrol stick movements anyway.

There is another reason for limitingthe depth of a sub-panel. In many instal-lations it may restrict knee room to theextent that entry into the cockpit will be-come awkward to accomplish and com-ical to behold.

Logical Reasoning NotwithstandingLike many builders, when it came

time to lay out my own RV-4 panel, Ifound that my "need to have" list of in-struments was dwarfed by my "wouldlike to have" list. So much so that I, too,had to consider the installation of a sub-panel and make use of other strategicareas to cram in everything I thought I"needed".

Since I was obviously going to crammy panel full of instruments regardless28 MAY 1988

TWO - IN - ONEALUMINUM TEMPLATE.

(.040")SCRIBE LINES AS SHOWNAS AN ALIGNMENT AID.

SCREW HOLES"

-HOLE CUTOUT SIZE FORLARGE INSTRUMENTS.

(3 ^8" PLUS CLEARANCE)

•OUTSIDE DIMENSIONLARGE INSTRUMENTS.

INSTRUMENT SCREW HOLECENTERS DRILL WITH ANO. 40 BIT FOR USE WITHAN AUTOMATICCENTER PUNCH.

——OUTSIDE DIMENSIONSMALL INSTRUMENTS.

HOLE CUTOUT SIZE FORSMALL AIRCRAFTINSTRUMENTS.

FIGURE 2.

INSTRUMENT FftNEL LAYOUT TEMPLATE

9F ^/-^ •

When you have a structural instrument panel as in the composite EZ's and Dragonfly's,the panel layout must be carefully planned before cutting the instrument holes. Sincepanel space is so limited there is space only for the most important instruments. Dualand quad instruments should be considered.

RECOMMEND MINIMUM SmClNGBETWEEN INSTRUMENTS IS 1/4",

A FUEL AHEAD OF THE PANELMAY PREVENT INSTALLATION OFA RADIO AND LONGER INSTRUMENTS

NO INSTRUMENTS CLOSE TOPANEL EDGE DUE TO FLANGE.

SECTION A - A

ADDING A SUB-PANEL MAY-1 LIMITED CONTROL STICK MOVEMENT,]2. RESTRICT COCKPIT ENTRY.3. INTEFER WITH PILOT'S KNEES

FIGURE 3.

INSTRUMENT FttNEL LAYOUT LIMITATIONS

NO LARGE INSTRUMENTSALONG BOTTOM ROW DUETO CROSS MEMBER BEHIND.

L

of logic, the exact positioning of eachgage in that small panel was critical andwould have to be accurately predeter-mined before I dared start cutting theinstrument holes in it. After all, alumi-num panel blanks are quite expensive.

Some Layout Tips and ProceduresThe best way to start, I think, is by

making a numbered list of the instru-

ments you intend to install. Arrangeeach listed instrument according tosome semblance of priority. For exam-ple, an airspeed indicator would behigher on the list than a color radarStormscope — and a tachometer wouldhave priority over a stereo. The primarypurpose of such a list is to help guaran-tee that you don't goof and forget to pro-vide a place for each of the most impor-tant gages before you start cutting out

Minimum instrumentation? Its all here. The Data Plate need not be on the instrumentpanel but Passenger Warning should be and is (even in a single seater). The directreading fuel gage in the panel center is even calibrated. The only deficiency — nocompass correction card.

the panel holes. To overlook one couldruin your day . . . and panel.

Of course, if you can't find room forall the gages, you will already know,from your list, that the one or two instru-ments on the bottom will be the ones toleave out.

The next preparatory step entailsmaking a few small scribbled sketchesto get a rough idea of which instrumentarrangements look promising. I try tokeep in mind the fact that a good instru-ment panel layout will be one that isstandardized to a degree. That is, theflight instruments will be centrally lo-cated in the upper portion of the panel,and the engine and other miscellaneousgages along the bottom or sides of thepanel. Some minor instruments may beeven further removed to adjacent loca-tions.

I always try to group all switches andcircuit breakers together in the samegeneral area in order to simplify the wir-ing job. I also try to make these itemsreasonably accessible from behind orbelow for maintenance and troubleshooting.

To save space and simplify the wiringin my current project, circuit breakerswitches will be installed and all sepa-rate fuses and/or circuit breakers will beeliminated.

Since the loran is becoming thenumber one navigation instrument, I be-lieve that, in the interest of safety, itshould be located as high as possiblein the panel (along with the compass).Then you won't have to be ducking yourhead into the cockpit while fumbling

SPORT AVIATION 29

MINIMUM INSTRUMENTATION

~BASIC VfR FttNEL

DUMMY "INSTRUMENT" CAR(LABEL EACH ONE)

1 1 o o o e e e •"> OO-. / PA*.. "«*

DELUXE VFR PANEL(NO V«CUUM SYSTEM)

SUB-PANEL

DUMMY INSTRUMENT PANEL(CARDBQARO)

COULD SUBSTITUTEA NARCO ESCORT II

THESE SIMPLIFY WIRING VACUUM SYSTEM REQUIRED(ft BASIC IFR PANEL)

FIGURE 4.

MAKING TRIAL PANEL LAYOUTS(FOR A R V - 4 )

with the data input and readouts.Now, with these preliminaries out of

the way, the next step is to make a fullsized cardboard duplicate of the instru-ment panel, a dummy panel, let's call it.This, you will find, is always worth thetime expended unless only a few instru-ments are involved, and you are willing

to risk a random buckshot-like patternfor an instrument arrangement.

You should always verify whether ornot there is anything behind the panelthat would interfere with the placementof any of the instruments anywhere inthe panel. For example, RV-4 buildersknow that they cannot locate any instru-

ment closer than 5/8" from the edges ofthe panel (see Figure 3). Mark and out-line areas such as these right on thedummy cardboard panel (as a remin-der) if they will affect the installation ofsome instruments in your panel.

Drawing in each instrument locationdirectly on that full size dummy panel isnot the easiest way to design or layoutan instrument panel. It can result in alot of false starts and you may evenhave to draw several different layouts,and perhaps spend a lot of time makingerasures as you continuously changeyour mind.

For that reason, I suggest you taketime to cut out separate "playing cards",or cardboard patterns for each instru-ment. Each card should be labeled andnumbered as illustrated in Figure 1. Usethe instrument layout dimensionsshown in Figure 2 for the cards. That is,make one properly dimensioned cardfor each of the large 3-1/8" instruments,and also one for each of the smaller2-1/4" instruments. If you plan to installsome automotive gages (oil pressure,oil temperature, fuel quantity, etc.) bewarned that these gages fit a 2-1/16"diameter hole, and not the standard2-1/4" one required for the small air-craft gages.

The reason I recommend cutting outthe individual instrument patternssquare is so that they will be easier toarrange, space and align on yourdummy cardboard panel.

Before you start laying out the instru-ment cards on the dummy panel, marka space for your radio if you plan tolocate your radio(s) in the instrumentpanel. This means you should haveselected the radio you will be installingbecause you must know the dimensionsfor the panel cutout. This is especiallycritical for those of us with small instru-ment panels that don't have space fora conventional radio "stack".

Radio widths have been standard-ized to the degree that most any makewill fit into a 6-3/8" wide opening, how-ever, their heights do vary somewhatfrom brand to brand. In addition, thereare radios, such as the Narco Escort IIthat are designed to fit into a regular3-1/8" instrument hole. That alternativeshould help matters for some builders.Currently, the loran sets seem to bestandardized to an overall 2" height.However, you really should know be-forehand which radio, or radios, you willinstall and make your panel cutouts tofit them.

Here's the good part . . . designingyour own instrument panel layout.Begin by laying all of those individualcards (templates) that you should havealready cut out and labeled onto the fullsize dummy instrument panel and shuf-fle them around until you arrive at anarrangement that you like. Then stickeach instrument card to the dummy

30 MAY 1988

A gorgeous IFR panel complete with twin Nav/Com radios, transponder, loran, gyro instruments, fuel flow, auto pilot, etc., etc. Butit is not for everyone unless they fly a lot of IFR. That is a big investment and a lot of weight to haul around otherwise.

panel with a small dab of library pasteor with small pieces of masking tape.This should keep the templates fromslipping out of position. NOTE: Be sureto space your large (3-1/8") instrumentsno closer than on 3-1/2" centers. Thiswill provide a 1/4" space between in-strument faces. The smaller 2-1 /16" and2-1/4" instruments should be spaced nocloser than 1 /4" apart, either.

Check your instrument list to be sureyou have included all the gages, andyour layout for a logical arrangement.And then you can stand back for a crit-ical look (you may have to deal yourselftwo or three layouts before you aresatisfied). If it still looks good, place thedummy layout pattern on the aluminuminstrument panel blank and tape itaround the edges enough that it won'tslip out of alignment. Next, with an au-tomatic center punch, make punchmarks to establish the center of eachinstrument and to locate its screw at-tachment holes. At this point you canreally appreciate how quickly and accu-rately you will be able to lay out andalign the square instrument templates.No need to trace each instrument circleonto the aluminum blank although mostbuilders will feel more comfortable indoing so.

Some builders will even prefer to layout the instrument locations directlyonto the aluminum blank, taking the

measurements from the dummy masterlayout, but it will take much longer to doit that way.

After all that is done, cutting out theinstrument holes with a circle cutter willbe anti-climatic. One word of wisdom,though, do not cut the instrument holesso precisely that the instruments are apress fit because, after the panel ispainted, the instrument won't slip in andyou will have to file the hole larger, ruin-ing your paint job.

Other EAA Reading Sources'The Sportplane Builder",

pages 242 through 247."Sportplane Construction Techniques"

pages 267 through 289."Firewall Forward",

pages 216 through 235.If you wish to contact the author

for additional information, pleasewrite to Tony Bingelis, 8509 Green-flint Lane, Austin, TX 78759.

A well equipped VRF panel that makes effective use of the limited space. A sub-panelis used to accommodate the loran and transponder. The scattered switches on the mainpanel complicate the wiring behind the panel.

SPORT AVIATION 31