'Mark II' Twin ComancheRebuilt and refurbished to his own specs, thisloaded lightplane answers one pilot's dream

The Robertson STOL, Miller 200 Jet Profile Twin Comanche gets off over a 50-foot obstaclein 1,120 feet, cruises at 223 mph. Cost of highly modified and "loaded"airplane, which started out as a used 1964 airframe, wassignificantly less than a new twin.

New, white-background panel reflects extensiveaddition of sophisticated flight

instrumentation and nav/com gear.

by JAMES M. PHilLIPS / AOPA 4028

•• "I know it's brand new, but whattype of aircraft are you, November SixYankee Papa?" asks the ground con­troller. For while a PA-30 shows on theflight plan, the craft he sees before hiseyes shows no such resemblance.

1 should say, "This is a Mark II TwinComanche," but 1 answer, "RobertsonSTOL, Miller 200 Jet Profile TwinComanche."

"Maintain 180 knots, Navajo SixYankee Papa," requests approach con­trol, since center has informed him ofan arriving 180-knot blip with encodedaltimeter readout.

To him, 1 merely acknowledge theinstructions, because this versatile MarkII can comply, since it is the mostmodified and updated Twin Comancheflying today. Besides, it loves to be iden·tified by its performance as a "Navajo."

Why such pride in an airplane?Two years ago, my engineering busi­

ness developed the need for a lighttwin to cover the eastern part of theUnited States. Uppermost in my mindwas the challenge not to buy an air-

FEBRUARY 1976 I THE AOPA PILOT 55

500 fpm

11,500 ft be obtained for less than any newfactory product.I selected for my reference and courseguidance the three most recent AOPAPILOT Aircraft Directory Supplements,referring to the listings and specifica­tions of multi-engine, piston.

Since the Piper Twin Comanche hasbeen out of production since 1972, itis not listed as an available aircraft,although it is reviewed in the selectedissues as a conversion, not only as aRobertson STOL but also as a Miller200. Why not have the best of twoworlds and combine both conversionsin one airplane?

With no more complicated engineer­ing than the arithmetic of selecting thebest of the slow-flight performancefigures for the Robertfon conversion andmarrying them to the best of the fast­flight performance numbers for theMiller 200 conversion, a "Mark II" TwinComanche was paper-designed, a designthat ultimately proved feasible within,or in excess of, the performance goals.

First of an, it would be ridiculous tolook for a Twin Comanche with sixseats when, with maximum instrumen­tation and fun tanks of gas, the weightand balance approach a critical condi­tion with only four people. Furthermore,in my travels I never have need to carrymore than three passengers. More oftenI carry only two and frequently butone or none. Therefore, a lower usefulload would be an acceptable specifica­tion.

Since money was at a premium, afour-place 1964 Twin Comanche bestsatisfied the requirements. Behind thismodel search was an initial conversationthat I had had with Jim Miller, of MillerAviation in Texas, who strongly atlvo­cated this early 1964 version becauseit was a strong, lighter-weight aircraft,particularly adaptable to his conversion.

The hunt for the airplane was started.Fortunately, right in my own backyard,my wife found one. Chuck Campbell, of

Lengthened nose addedspeed, stability, looks­

and room for an extra

luggage locker.

and it had many more extraordinaryfeatures than the "store-bought variety."Although I was not qualified to whittleout a light twin by myself, I was deter­mined to call on all my experience andlimited budget to create the best flyingmachine for my needs.

The goal was simple and direct. Thefinished product under no circumstanceswould carry an experimental license.All work would be done by the bestmodification centers with full FAA ap­proval, all equipment would be new andof the best quality-and all this would

As part of STOL conversion, aileronslower along with flaps to providefull-span flap effect. Wing "fence" alsoadds to STOL performance.

11.3 mpg21,000 ft223 mph52 mph1,900 fpm

1,250 sm

Specifications and Performance

Gross load 3,800 IbUseful load 1.413 IbRange:

Max fuel,75% power

Miles per gal75% power

Service ceiling75% cruiseStall w/flaps-gearClimb rateSingle-engine climb

rateSingle-engine

service ceilingTakeoff distance

over 50-ft obstacle 1.120 ftLanding distance

over 50-ft obstacle 970 ft

MARK II TWIN COMANCHE

'MARK I/' TWIN COMANCHE continued

craft off the factory shelf, for my spe­cial airplane had to outperform anyavailable equipment including the PiperAztec E, the Beechcraft Baron B55, andthe Cessna 310. Yet it had to have aconsiderably lower initial outlay andoperating costs.

While I have acquired well over adozen singles and twins for personal orbusiness use, my "fun airplane" was anexperimental biplane made by a friend,

56 THE AOPA PILOT I FEBRUARY 1976

Campbell Aviation, a long-time friend,had a 1964 Twin Comanche that heused for his personal transportation ingetting around the country between hisoperations where he sold and servicedMitsubishis and Merlins.

The airplane was fully equipped witha Narco transponder, dual Mark 12Narco transceivers, strobe lights, outsidepower receptacle, EGT gauge, PiperAltimatic II autopilot, glideslope receiver,Bendix ADF, VOA-4 and VOA-5 nav in­dicators.

At first he was reluctant to sell theairplane, because the engines had hightime. I was anxious to get it because itwas my intention to remove the enginesand go with the 200-hp Miller conver­sion.

Accordingly, I bought the airplanefor $24,000 and started with a plan.Chuck Campbell followed through witha lOO-hour check, complied with allADs and bulletins, and corrected any­thing that he thought was not just theway he would want it for himself.

Immediately I wanted to fly in thatexclusive group of people who couldconsistently land a Twin Comanchewith no apologies and to operate it fromthe short airfields in my territory with amargin of safety as promised in theliterature for the Robertson STOL con­version kit. A phone call to Robertsonsoon had the aircraft on, its way toNew Orleans for a newly contouredwing leading edge, ailerons that givean effective 15 degrees of flaps for thefull wingspan, spoilers between the fuse­lage and nacelles for better landings,wing fences to stop spillage of air acrossthe wing and a large dorsal fin. Thepackage came to $5,000.

What a difference. It cut literally20 mph off the low side of the speedspectrum and chopped the stall speed,with gear and flaps down, to 52 mph!The normal approach, prior to this con­version, was 105 mph. By the timeRobertson finished the modification andmy reeducation, approach speed wasdown to 85 mph, over-the-fence at80 mph, and touchdown about 65 mphwith better than average landings. Bythe same virtue, the takeoffs were abso­lutely phenomenal, as Robertson insistedthat the climbout be made with 15degrees of flaps at 85 mph.

Their tests had proved conclusivelythat altitude is one of the safest attri­butes in an engine failure, provided theairplane is flown above the Vmc of80 mph. This is another justification forthe trip to New Orleans, for my Vmcwas dropped 10 mph to 80 without thecostly conversion to counter-rotatingpropellers. Simultaneousiy the gross andpayload were increased 200 pounds to3,800 pounds, making it a much moreusable aircraft for operations in and outof small fields of only 2,000 feet in West

Virginia, Pennsylvania, and Ohio.The next item on the budget was a

new interior, beautifully done in Bata­via, Ohio, by Aircraft Upholstery. Afterremoving all the original insulationand replacing it with extra thick, sound­absorbing material, they installed avery conservative interior in silver-graycorduroy trimmed in alabaster. Thesame fabrics and carpeting were used asin the Lincoln Mark IV automobile, andall had flame-retardant components. Iwanted a quiet interior inducive tomany pleasant hours at the controls andto a restful passenger atmosphere.Further down on the production sched­ule was a flashy paint job for the ex­terior of the aircraft. The interior costwas $1,200.

The time came once more to take theairplane to a major modification center,this time to Horseshoe Bay, Tex., whereJ. W. Miller Co. literally rebuilt thewhole airplane. Their 1,000-hour optionliterally rejuvenated the complete air­frame; it was competely stripped downand any part showing wear or anydeficiency was replaced. Both enginemounts were removed, including the160-hp engines with all their acces­sories. The bothersome cast-propellerextensions were scrapped, and thus aconstant source of vibration and apotential area of failure were elimi­nated.

Factory-new engines and all new ac­cessories, including electrically heatedpropellers were installed. Tip tanks wereadded to extend the range. Dual brakes,taxi light, ram's-horn controls withautomatic electric trim, one-piece wind­shield, and extra-thick windows toassure a quiet cabin were also incor­porated. An extra-long nose was addedto enhance the appearance, increase thespeed, stabilize flight characteristics andprovide an additional luggage locker.

Miller Aviation also came up with thebest Alumigrip paint job that I have yetseen, so perfect one pilot said, "Jim, itlooks as if they dipped the whole plane."It had to be painted in bright colors andit is: cranberry and tropical orange onan all-white airplane, set off by whitestrobe lights on the tips and a red strobeon the tail.

With this $25,000 job, the total costof my basic aircraft had come to$55,200. The conversion was complete,and the airplane was fully operational­but there was still one more step Iwanted to take.

For the selection of upgraded instru­mentation, I returned to The AOPAPILOT, first to determine basic require­ments, and second to select by specifica­tion and by cost comparison the specificequipment.

From Texas, the airplane with its new200-hp Lycoming engines went toColumbus, Ohio, for the installation of a

sophisticated and modern, white instru­ment panel. There Capital Aircraft Elec­tronics installed a new Century III auto­pilot with full radio couplers, includinglocalizer and automatically engagingglideslope. A horizontal situation indica­tor, King KI-525 complete with a slavedgyro compass system and a King RMIbeautifully display all information, yetact as the command post for this excel­lent autopilot instaliation. A NarcoDGO-lO with an independent electricgyro provides a back-up system.

The old Bendix ADF was traded fora new digital Bendix T-12D. CollinsMicro Line radios complete with anaudio-control panel were selected; andwe installed dual 720-channel trans­ceivers with select, store, and recallcapability and dual navigation receiverswith to/from digital readouts. With thisinstallation, Capital provided an instru­ment-hole-mounted RNAV, the KingKNC-610, and a digital Davtron clockwith flight-time recorder and elapsed­time meter.

You may think the remaining spaceon the panel would not accommodateanother instrument, but the KingKN65 DME with its remote readoutfit neatly into a small area, as did thethree-light marker beacon and encodingaltimeter, as well as the original altim­eter. Naturally, the small remote-controltransponder by Narco, reworked to TSOacceptance, took up a minimum ofspace, as did the EGT for twin-engineoperation.

Whoops, don't light up that cigarette!What used to be one ashtray now holdsthe clock, while the other contains theammeter. (The switch for the strobelights has replaced the cigarette lighter.)This final $14,000 package brought theprice of my finished airplane to $69,200.

In the execution of this program, theselection of modification and installationcenters justified a thorough evaluation.All participants performed excellentwork at acceptable bid prices, whichheld the price of the Mark II to within50% of a similarly equipped new lighttwin.

My Mark II is loved by all who haveflown it, including airline pilots, instruc­tors and fellow pilots. What aircraftavailable today can meet the basic speci­fications of a cruise speed of 223 mph;a service altitude of 21,000 feet; take­off over a 50-foot obstacle of 1,120 feet;landing distance over a 50-foot obstacleof 970 feet; a useful load of 1,413pounds; and a maximum range of 1,250statute miles at 75% power? The rateof climb for both engines is 1,900 feetper minute; yet with one engine, 500feet per minute-greater than that ofany commercially built reciprocatinglight twin available today.

Radar? Not yet-but we're evaluat-ing it. 0

FEBRUARY 1976 I THE AOPA PILOT 57