May 1, 1996
A good-looking, four- to six-place light twin that goes 170 knots on 17 gph and costs a relatively modest $45,000 to $80,000? Such objectives may seem incompatible in the same airplane, but the truth is that from 1963 to 1972 Piper built about 2,200 airplanes with those characteristics. We're talking about the Twin Comanches, possibly the best-looking, best- performing light twins ever built — and certainly one of the best airplanes for the money. For all its performance, it may be hard for some to believe that Twin Comanches use fuel injected variants of the venerable — and nearly bulletproof — 160-horsepower Lycoming O- 320 engine. That's right, the same engine used in the Cessna Skyhawk, Piper Super Cub, and Piper Tri-Pacer, among other plodding, mundane airplanes.
Early model Twin Comanches, designated PA-30s, came out between 1963 and 1965. A bare-bones, single-vacuum-pump, day-VFR-equipped, four-seat PA-30 (brochures called it the "Sportsman" version) would have cost just $33,900 or so in those days. For a top-of- the-line "Professional" Twin Comanche, you paid about $41,200.
In 1965, the PA-30B was introduced. You can tell a B model by its six seats and third side windows. The options list was expanded to include wingtip fuel tanks, a heated windshield, propeller anti-ice, and an oxygen system. (NB: The Twin Comanche is not certified for flight in known icing conditions.) The tip tanks, which carry an extra 30 gallons of fuel, proved a very popular option, and by the late 1960s most Twin Comanches had either been ordered with them or outfitted with aftermarket tip tanks then manufactured by Brittain Industries. Today, J.L. Osborne of Oro Grande, California (619/245-8477), holds that tip tank STC.
The Turbo Twin Comanche B also made its debut in 1965. These came with Rajay turbochargers, which utilized manually operated wastegates. Optimum cruise speeds of the turbocharged Twin Comanches were advertised as hovering around 200 knots at 12,000 feet, or 214 knots at 24,000 feet. The turbo models' empty weight is almost 200 pounds more than their standard-equipped, normally aspirated brethren, so all-engine and single- engine rates of climb are lower (but single-engine service ceiling rises to 8,800 feet), and the useful load of an average-equipped airplane — at 1,341 pounds — is some 50 pounds lighter. Add the tip tanks and top off the other four wing fuel tanks and payload drops to 650 pounds or so.
Operating the Rajays requires a deft touch. Early Turbo models used two (one for each engine) vernier-type, push-pull controls for adjusting the wastegates. The drill was to make an initial power setting with the throttles, then screw in the wastegate controls to close the wastegates and raise the manifold pressures to a desired level. You have to do this s-l-o-w-l-y or risk overboosting an engine's manifold pressure limits. Ham-fist a manually controlled wastegate and you're asking for an early engine overhaul at best, and a catastrophic failure if you're unlucky.
Manually controlled turbochargers are obsolete now, having been replaced by more goof-proof designs. Those tempted to buy Rajay-boosted Twin Comanches ought to know that these turbochargers have been linked to corrosion of engine mounts. A 1982 airworthiness directive (AD) requires that the Rajays' turbine housings be inspected or replaced, if necessary, every 200 hours. Another AD mandates inspection of the turbines at 100-hour intervals.
Age belies the instrument panels of the straight PA-30s and the -B models. By now, many have been heavily modified and improved with the latest avionics, but an original-condition airplane will have a non-standard instrument configuration. Old- fashioned, black-background attitude indicators and backwards-turning, drum-type heading indicators were used. The heading indicator is where the attitude indicator ought to be, and the altimeter is over at the lower left, where we've come to expect to see the turn coordinator. Narco Mark 12s were de rigueur in the early 1960s, so don't expect too much in the way of avionics sophistication from a standard-issue early Twin Comanche. Also, human factors was still an infant science in those days, and old Twin Comanches show it. For example, all the electrical switches were identical toggle switches, making them easy to misidentify, and circuit breakers were kept beneath a trap door below the power quadrant.
The -C and Turbo C models came out in 1968 and brought with them instrument panels laid out in the modern, standard T-configuration for the flight instruments. Magneto and starter switches were moved to a side panel, electrical switches were converted to internally-lighted rocker switches, and the circuit breakers were moved to the lower right subpanel. The C models also earned a few knots' worth of extra cruise speed, thanks to engine beef-ups that included better valves and valve guides, and sturdier and better- lubricated crankshafts and camshafts.
The last of the Twin Comanches were the PA-39s, which were rolled out in early 1970. The big improvement here was the introduction of counter-rotating propellers. Even though Orville and Wilbur employed this concept, Piper hawked the PA-39s as revolutionary design breakthroughs. PA-39 C/Rs (for counter-rotating), as they were called, had the advantage of vastly reducing the adverse effects of asymmetric thrust in engine-out situations where the critical engine failed. The critical engine is the engine that, if it failed, would create the worst deterioration of performance and handling. In conventional American light twins, the critical engine is the left engine. That's because both propellers rotate to the right, and the right propeller develops more thrust than the left, owing to its comparative surplus of thrust at an arm farther from the center of gravity than the left engine's. Lose the left engine and that extra thrust can make the airplane yaw uncontrollably and, if the airspeed is low enough, cause the airplane to roll inverted.
By having the left propeller turn to the right and the right propeller turn to the left, the C/R models eliminate the critical engine. Yawing moments in engine-out situations are reduced, and low speed handling is greatly improved.
It's only natural to wonder why Piper made the C/R switch. Which lets us segue into an explanation of a major-league skeleton in the Twin Comanche's closet.
Part of the Twin Comanche's appeal was its low cost of operation. As part of its sales pitch, Piper claimed that a Twin Comanche could be operated for $17 an hour. For this reason, many flight schools in the 1960s bought Twin Comanches for use as multiengine trainers. But as it turned out, many unlucky — or unwise — students and instructors learned that Twin Comanches could bite back. The airplane's laminar flow airfoils shed lift quickly and are more suited for high-speed cruising than exploring the slowest end of the flight envelope. Couple this with the regulatory requirement for multiengine rating applicants to demonstrate competence in flying at VMC (the minimum control airspeed with the critical engine inoperative) and you have the makings of a safety problem.
Multiengine students in the 1960s usually followed a curriculum that would scare the daylights out of today's multiengine instructors. Then, the student was made to practice VMC demonstrations and engine-out maneuvering at 500 feet agl — or less. Instructors routinely pulled an engine just after takeoff. Single-engine stall practice was another ordeal that many students were made to endure.
While the denser air near the surface made for a maximum of thrust asymmetry, and therefore an excellent demonstration of control problems, some Twin Comanche students and instructors found the experience far too realistic. By 1967, 13 fatal training accidents had occurred in Twin Comanches. By 1971, 40 fatal accidents had taken place. Many of them involved stall/spin situations, and crash investigations indicated that the airplane had an unusually strong inclination to enter an unrecoverable flat spin after slowing below VMC with an inoperative engine.
After an investigation by the National Transportation Safety Board, the FAA put out an advisory circular banning single-engine stalls (except when performed by qualified test pilots), discouraging VMC demonstrations in density altitude conditions where VMC is close to stall speed, and requiring that stall demonstrations be done at altitudes high enough to permit spin recovery — and in no case lower than 1,500 feet agl. So in large part, we can thank the Twin Comanche for today's saner multiengine training guidelines.
Piper put out two service bulletins aimed at taming the Twin Comanche's engine- out and stall behavior. One recommended the installation of wing leading edge stall strips, a rudder gap seal, and an aileron/rudder interconnect system. The other offered a new right engine with a counterclockwise-rotating propeller, a modification that would in essence transform a PA-30 into a PA-39.
In another safety move, a 1969 AD required a 9-knot hike in the airplane's VMC (from 80 mph/69 knots, to 90 mph/78 knots) and a new red radial line on the airplane's airspeed indicator to correspond with the new value.
Is the Twin Comanche a dangerous airplane? No more so than any other light twin. Flown properly by adequately-trained and current pilots, the airplane behaves quite predictably.
There is definitely no shortage of yarns about the Twin Comanche's alleged behavior problems. Some of them are shared with its single-engine counterparts, the PA-24 Comanches, which antedate the twins by six years.
One quirk has to do with takeoffs. Seems that the Twin Comanche has earned a reputation for lifting off before reaching VMC. This puts the airplane in the air at an airspeed that denies the pilot sufficient rudder authority should an engine fail. In effect, the pilot who lets his Twin Comanche — or any other multiengine airplane, for that matter — lift off before reaching VMC (plus five or so knots) bets his life that an engine won't fail. So the temptation is to hold the airplane on the runway as speed builds to the magic number. This can involve a lot of skittering and hopping, particularly in windy conditions.
One accepted technique for coping with this eagerness to fly is to lift off anyway, then fly in ground effect until airspeed rises above the customary VMC-plus-five target. Another is to install Harlan Associates' 15-inch diameter nosewheel. This smaller-than- stock nosewheel lowers the airplane's angle of attack, which helps the airplane stay on the ground during the takeoff run and helps to prevent nosewheel-first arrivals on landing. You can obtain more information about this STC from Harlan at 904/767-5564.
Landings are another source of conversational fodder. The Twin Comanche's wing is set low to the ground, which makes it very efficient in ground effect and has earned the airplane recognition as a floater. The lore is that Howard T. (Pug) Piper, the company's director of engineering in the Comanche days, wanted the airplane to be easy to step up to — literally. He didn't want the drag of a step, and he wanted to make stepping up to the wing as easy as possible.
Die-hard Twin Comanche aficionados will tell you that the secret to a good landing is maintaining the proper airspeed at the runway threshold (about 90 mph/78 knots). But airspeed control can pose a challenge. Because the airplane is so clean, it is reluctant to dissipate airspeed. The key is to manage both power and configuration well in advance of a descent or landing and to plan each approach as though you were flying a high- performance airplane — which the Twin Comanche definitely is.
Now that the Twin Comanche is well into its third decade, corrosion and other airframe wear and tear is beginning to take its toll. Other service items of concern focus on the landing gear, fuel system, and ailerons.
Bungee cords are used to assist the landing gear in the retraction cycle, and these must be replaced every 500 hours per a 1977 AD. Worn-out bungees can cause the gear to hang up and have been linked in the past to several gear-up landings, of which there have been many, many, many cases. The bungees also keep the gear from collapsing after a manual gear extension, so it pays to replace them more often than the mandatory interval.
The fuel system's woes center mainly on corrosion and contamination of the fuel drains and filters, which have to be checked every 50 hours according to the terms of a 1982 AD. Because of the drains' design, trapped water can cause the strainer bowls and filters to corrode and clog the system.
A fuel tank sump quick drain lever is located under a floor panel aft of the fuel selectors. To drain, you use the fuel selectors to choose the tank to be drained, then pull on the quick-drain knob. Because the fuel drains away from the pilot's view, it can be difficult to detect any water or contaminants. The whole idea was to let pilots sump their tanks without having to wreck their suits by crawling beneath the wings. Nice thought, but nothing beats an up-close inspection of the drained fuel, even if it means getting down on all fours.
A clear plastic tube located near the drain knob lets the pilot observe any particulates as they're drained from the sumps and confirm that the flow of fuel has stopped when the drain knob is pushed back in. However, it's difficult to detect water as it flows by. And in any event, many pilots let those tubes grow old and discolored (even though they're inexpensive and easy to replace), preventing a view of anything in the fuel.
Aileron spars and aileron hinge attach brackets are other sore spots in the Twin Comanche's design. A 1977 AD calls for inspection or replacement of the aileron hinge brackets every 100 hours. A 1979 AD requires an inspection or replacement of aileron nose ribs every 100 hours. In that same year, 100-hour inspections of the aileron spar doublers were also put in effect through an AD, although installation of a Piper modification kit obviates this rule.
There are a bewildering number of modifications for the Twin Comanche. If you installed all the speed mods, it appears the added speed benefit would give you an airplane with 300- knot cruise speeds — if the claims are to be believed.
Knots 2 U, Inc. (616/526-9646) leads the pack, with no fewer than 10 speed mods. These include a 1/4-inch-thick, one-piece windshield (add 1 to 4 mph to cruise): a windshield cowl (worth an extra 1 to 3 mph); dorsal fin (2 to 4 mph); vertical fin cap (1 to 2 mph); wing root fairings (1 to 2 mph); rudder gap seal (1 to 2 mph); aileron and flap gap seals (6 to 7 mph); gear lobe fairings (5 to 9 mph); and nacelle exhaust fairings (3 to 6 mph). A jazzy, super-sleek cowl, festooned with NACA induction air scoops and slit-like air intakes, is also available.
Lopresti Speed Merchants (800/859-4757) sells its low-drag Wow Cowls (add 8 mph) for the Twin Comanche, along with its pointy Winner Spinners. Lopresti claims that the Wow Cowls provide a greater volume of cooling air to the engines than the stock cowls, in spite of the small circular inlets. These cowls also allow easier access to the starters and alternator belt.
Lopresti's Speed Splitters (flap track fairings — add 4 mph), Speed Spats (main gear fairings — add 5 mph), and Speed Seals (flap gap seals — add 2 mph) are other popular items with Twin Comanche owners.
There's even a Robertson STOL modification for the Twin Comanche. This and all the other Robertson STOL STCs are now owned by Sierra Industries of Uvalde, Texas (210/278-4381). The Robertson mod promises a 10-mph reduction in VMC and stall speed, and provides an increase in gross weight (3,800 pounds, compared to the standard PA-30's 3,600 pounds). Takeoff and landing distances over the FAA's mythical 50-foot obstacle are slashed by half, compared to an unmodified airplane. On top of this, approach speeds are cut by 15 mph, or 13 knots, a side benefit of the kit's high-lift devices.
J.W. Miller Aviation of Horseshoe Bay, Texas, used to hold the STCs for a number of interesting Twin Comanche mods. Among them was a 200-hp conversion that used Lycoming IO-360 engines, deice boots, wing locker tanks, and a stretched nose. At this time, however, the STCs seem to be in a state of transfer, and no orders are being taken. Bidders for the STCs may restart production of the Miller mods after negotiations are finalized.
Perhaps the highest expression of a modified Twin Comanche is the Bailey Bullet. The Bullet, a project initiated by attorney F. Lee Bailey and his son Scott, incorporates just about every modification you could ever hope for in a Twin Comanche. It has the Lopresti cowls and spinners; the last of the Miller nose and wing locker mods; Osborne tip tanks; and an upgraded electrical system and avionics, including an electronic horizontal situation indicator, Stormscope, and weather radar. STC applications for vortex generators and a TKS weeping wing ice protection system are now on hold. Currently there is only one Bailey Bullet in existence, and last word was that the Baileys were asking $450,000 for this beauty. Though certain legal problems may prevail, the Baileys' company — Palm Beach Roamer (407/966-4277) — is more than willing to build you a Bullet of your own. Just be prepared to drop $500,000 or so for a Bullet with all the trimmings.
The airplane photographed for this article, a 1969 PA-30C owned by Tom Snow of Chattanooga, Tennessee, is a more typical example of a Twin Comanche modification. It has the Lopresti cowls, spinners, gap seals, spats, and splitters, plus the Miller nose and a Robertson STOL kit. Snow, who owns a company that manufactures and maintains welding machinery, uses his Twin Comanche to reach distant customers who need urgent repairs. Snow claims that the Lopresti mods gave him an extra nine to 10 knots in high- speed cruise, but that that advantage went away when the Robertson kit was added. Even so, Snow is pleased with his airplane's performance and says the STOL kit has lived up to every promise.
Alas, Snow sold his Twin Comanche shortly after the photographs were taken. In a quest for more speed, he bought a Beech Baron. "But with the way that thing eats gas, I sure wish I had my Twin Comanche back," he said in a recent conversation.
Anyone contemplating the purchase of a Twin Comanche — or a single-engine Comanche — owes it to him- or herself to join the 4,000-member International Comanche Society (Hangar 3, Wiley Post Airport, Bethany, Oklahoma 73008; 405/491-0321). The ICS is an invaluable source of information about any and everything having to do with Comanche singles or twins. The ICS' technical director, Maurice Taylor, has forgotten more than anyone else could ever know about the Comanche brand, and he is a walking encyclopedia. The ICS sells a great book on Comanche maintenance, and Taylor also stars in a videotape about Comanche technical tips.
The Society serves as a vehicle for Comanche-specific training programs offered by instructors completely familiar with these airplanes and sponsors regular fly-ins of the Comanche faithful. Devotees are organized in groups according to geographic region as well as specific airplane types. The groups, called "tribes," come together annually to share information and just plain have a good time. Membership in the ICS is $40 per year, and this includes a subscription to the monthly Comanche Flyer, a magazine that does a great job of filling you in on routine maintenance topics, as well as techniques for coping with various ADs and service bulletins, and also providing stories about members' flying experiences.
The Twin Comanche is an excellent airplane, and its value in the used market continues to rise. The airplane is well supported, thanks to a well-organized owners group and a plentiful supply of parts and modifications. The pilot new to the breed should seek out qualified instruction, maintain a high level of proficiency, and be well aware of the airplane's maintenance requirements. The airplane's age should be a warning flag to prospective buyers. Expect a continuation of the Twin Comanche's airframe problems and go into ownership with the understanding that considerable investments in airframe fixes and additional inspections may be necessary down the road.
That aside, the Twin Comanche will serve you as no other light twin can. It's arguably the best light twin available, and its bang for the buck is exceeded only by its classy looks.
Aircraft Power and Fuel,
Safety and Education,
Engine overhauler Penn Yan Aero announced that it is extending the warranties on overhauled and experimental aircraft engines, effective immediately.
The NTSB has organized a safety seminar May 10 to focus on aerodynamic stalls and loss of control, a leading cause of general aviation fatalities.
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