Performance Data for the Piper PA-39 Twin Comanche C/R

The PA-3D is remarkable: 17D-knot cruise speeds while burning only 17 gph. "landing problem." Legend has it that no one can land a Twin Comanche the same way twice. There is something about its behavior in the flare that makes it difficult to land well. That is, gently, mains first. The airplane has a tendency to drop in-kerthump!-on all three wheels, as though it has let go of its lift suddenly, prematurely and without warning. Even if you do man- age to get the mains to touch down first, the nosewheel will follow a mi- crosecond later. But remember that you are flying with the wings of a single and the weight of a light twin. The laminar- flow Comanche wing, designed for speed, not slow flight, can release all its lift suddenly when near the stall. It is a wing that does not stall as pro- gressively as fatter, more docile ones do. That is to say, the outboard sections can stall at the same time the inboard ones do. And with a wing-mounted en- gine, the lift-producing area of the wing is reduced. In short, you have more weight for a lesser amount of lift. Of course, there also is its nose-high deck angle. Designed to give the pro- pellers adequate ground clearance, what this attitude really means is that unless you raise the nose to what might seem an unusually high angle in the moments before touchdown, you will land with all three wheels striking the runway at once. Or maybe even nosewheel-first, if it is one of your first few times out. Another part of the problem might be the way the nacelles blanket the rearward airflow. By the time the rel- ative wind strikes the stabilator, this theory goes, its force has been de- creased. The stabilator can lose lift or even stall as you attempt a flare. This is aggravated when you select full flaps and have a forward center of gravity (CG). All twins, you may hasten to say, have nacelles that could create the same behavior. Or landing any air- plane with full flaps and a forward CG makes it difficult to achieve a proper landing attitude. But the Twin Comanche is not just any airplane, and therein lies its ul- timate appeal. Unlike most airplanes around these days, the Twin Comanche takes. some skill, hard practice and fi- nesse to land properly. If you are the kind of pilot who wants a forgiving airplane, then this is not the one for you. You have to love it and deal with it to earn your place as a bona fide, competent Twin Comanche pilot. On the subject of landings, it seems that every Twin Comanche pilot has a method of his own; but certain com- mon elements emerge when you in- ventory all of them. First of all, a fur- ther aft CG helps. (One owner puts 100 pounds of ballast in the aft baggage compartment when he flies alone or with just one other person in the co- pilot position.) The airspeed should be kept constant on final, pegged at blueline (Vyse, 91 knots). Use half, not full, flaps. On short final, with the field made, power should be reduced gradually to 13 or so inches of mani- fold pressure (mp), and over the threshold the airspeed should be bled off to about 70 knots. Now keep some power in as you raise the nose to an attitude that is higher than you ordi- narily might be comfortable with in a light twin. Above all, keep the control column back and hold it there through the touchdown, which should come mains-first at a speed just above stall. But then again, it may not. There are good days and bad days. The stories go on and on. But the point is, landing a Twin Comanche is never a dull experience. If you own one, you, too, will be entitled to your own per- sonal theory of how to land it. Other endearing quirks that Twin Comanche pilots take pride in coping with are a shudder that passes through the airplane when cruising at 2,100 or BY GUERNSEY LE PELLEY A PLOT EXPOSED cont;nm'd 2,200 rpm, and pitch oscillations, usu- ally discovered while trimming for cruise flight. The stabilator is very ef- fective at high airspeeds, and this makes the airplane very sensitive in the pitch axis. The technique to use here, experts say, is to trim, then wait, then trim some more. It takes time for this airplane to settle down at cruise. It is anybody's guess as to what causes the shudder. The propeller shaft extensions? The engine mounts? No one seems to know, or care; but it is there, all right. While cruising you no- tice that from time to time vibrations pass through the control column or that the instrument panel shakes slight- ly. Oh, well, it is just another Twin Comanche idiosyncrasy. You can try to eliminate it by changing the rpm, but this probably will not do any good. Most choose to ignore it and fly on. However irritating th~se traits may be, they are of relatively minor con- sequence, causing little more than em- barrassment or hurt pride in the case of the landing behavior or annoyance in the case of the pitch oscillations. There are other traits of the Twin Co- manche that pass beyond the bounds of quaint eccentricity and bring into question what may be this airplane's darker side. While the Twin Comanche was a brilliant composite in terms of performance and economy, it may be that if anything was sacrificed in the bargain it was safety. No discussion of the Twin Coman- che would be, complete without ad- dressing the subject of this airplane's alleged killer Vmc stall characteristics. We have seen how the Twin Coman- che was the least expensive of all the light twins of its day. This, and its low fuel consumption and overhead (the engines are very durable and uncom- plaining) made Twin Comanches very popular with flight schools as multi- engine trainers. The Federal Aviation Administration before the late 1960s was not as clear in its guidelines for stall training as it is today. A multi- engine student in those days could ex- pect to practice his Vmc demonstra- tions within 500 feet of the ground. There, in the denser layers of the at- mosphere, asymmetric power is maxi- mized. While this provides a convinc- ing presentation of the control problems a pilot can expect to encoun- ter in the takeoff configuration with an inoperative, windmilling engine and an airspeed close to the single-engine minimum control airspeed, some of 72 • SEPTEMBER 1980 At long last I have decided to sit down and write the truth about Twin Coman- ches. This either will make me a hero or brand me as a traitor by the Secret Order of Twin Comanche Owners. But somebody has to sacrifice himself for the betterment of mankind, if not simply for truth in advertising. For more than a decade, buyers have been sneaking into dark alleys and knocking at an unlabeled door (two long, one short) to get the awful word- of-mouth low-down on this airplane's characteristics. A pair of cracked, swollen lips appear as the peephole in the portal opens. Then they whisper, "Hey, man, the Comanche brand is hard to land." By peeling another sawbuck off your roll of bills you can hear more. The lips say, "Hey, Jake, the engines shake." If you come up with enough bread you can get some further hair-raising facts: "It won't stay level, Neville" or "It won't fly even, Stephen." What no one knows, and what I am herewith exposing for the first time, is This was all that was fOillid after the smoke cleared ill Gllemsey Le PelIcy's offia, believed to have been bombed by the Comallche Nostra. Le Pelley, AOPA 165412, all editorial cartoollist alld a commercial pilot with mlllti-ellgille alld illstrumellt ratillgs, is believed to be litlillg 1111- der all assllmed Ilame ill IIpper Saskatchewall. that Twin Comanche owners have been spreading all this propaganda them- selves to keep undesirables out of the neighborhood. Some Twin Comanche owners will not even paint their air- planes, just to perpetuate the impression they are so dangerous to fly no owner wants to put too much money into one. Naturally, being a Twin Comanche owner myself, I knew what was going on. It is only now, after years of anguish, that my conscience has caught up with me. It is not easy being a snitch. But I have decided. I'm going to sing. Just call me the Comanche Canary. For instance, did you know that many test flights of Twin Comanches are made by writer I pilots who previously had never flown one? Comanche owners lie in wait for these innocent test pilots just to be able to misinform them. An innocent test pilot is easy to spot. Usually he frequents well equipped air- ports only on rainy afternoons. He ap- pears with styled hair, oversize, gold- rimmed sunglasses, a briefcase made of real leather and a sharp sport jacket. The jacket he removes and folds neatly on a back seat, revealing a casual powder- blue shirt with a large, loosely knotted, but very sincere, tie. Mostly he is a capable pilot, but gul- lible. Carefully planted suggestions by nefarious Comanche people make him PLOT EXPOSED cmrtinut'd Based on manufacturer's figures; fuel flow data for both engines; all V -speeds indicated airspeed. 1972 Piper Turbo Twin Comanche C/R (PA-39) Basic price new $57,490 Current markl't value 556,000 1966 Piper Twin Comanche B (PA-30B) Basic priet, new $35.990 Current market valul' $34.000 these demonstrations in Twin Coman- ches ended in fatal stall/spin accidents. Crash investigations suggested that the airplane easily entered a flat spin. By 1967, 30 persons had died in 13 training accidents involving Twin Co- manches, and the debate had begun. A large part of the problem, of course, was that the Vmc maneuvers were per- formed so close to the ground, making a recovery from the stall nearly impos- sible. Then it was learned that some of the accidents involved passengers in the rear seats, which would move the CG aft and enhance the probability of a flat spin or, at least, make stall re- covery much more doubtful. In some accidents low-time instructors may have failed to recognize a stall in time to effect a recovery, or, if a stall/spin had been entered, failed to stop the condition in time to prevent impact. More puzzling was the involvement of many experienced instructors in these accidents, pilots who should have been able to recognize and control an air- plane's adverse behavior. The National Transportation Safety Board and the FAA became very in- terested in the Twin Comanche's spin characteristics, and a chain of events began that ultimately led to changes in the airplane's airfoil and powerplant designs and its operating limitations. Other changes affected recommenda- tions on the performance of stalls and single-engine training maneuvers that are still in effect today. First came ~ July 27,1967, letter from the NTSB to the FAA describing the pattern of accidents and noting a co- incidence of impacts in a flat attitude. While the report noted that spin tests had been conducted during flight tests in 1964 and that no flat-spin charac- teristics were detected, it also was men- tioned that there were no deliberate at- tempts to induce a flat spin. Therefore, there was no factual evidence concern- ing the Twin Comanche's control char- acteristics while actually in a flat spin. What really concerned the NTSB was that there was no assurance that nor- mal spin recovery techniques would bring a Twin Comanche out of a fully developed flat spin. The NTSB's recommendations were to find out what configuration and pi- lot input it would take to precipitate a flat spin, if there was adequate con- trol available to check an inadvertent entry or if a special procedure was nec- essary to effect a recovery. In September 1967 wind tunnel and 2 Lycoming 10-320B. 160 hp @ 2,700 rpm 2,000 hr 2 Hartzell HC-E2YL-2, 72 in 35 ft 11.7 in 36 ft 9.5 in 25 ft 2 in 8 it 3 in 178 sq ft 20.22 Ib/sq ft 11.25 Ib/hp 4/6 2,207 Ib 1,393 Ib 853 Ib 798 Ib 3,600 Ib 3,725 Ib 90/84 gal 120/114 gal 8 qt 250 Ib (20 cu ft) 950 ft 1.750 ft 1.530 ft 1,460 fpm 260 f pm 178 kt 168 kt/l7.2 gph 161 kt/l5.2 gph 144 kt/l3.4 gph 695 nm 986 nm 768 nm 1.087 n m 18,600 ft 5,800 ft 1,215 ft 1,875 ft 66 ki 60 kt 78 kt 78 kt 97 kt 9] kt 130 kt 108 kt ]41 kt Specifications Engines Recommendl'd TBO Propellers Wingspan with tip tanks Length Height \\'ing area \Ving loading Power loading Passengers and cn'w Empty weight Useful load (basic aircraft) Payload with full fuel (basic aircraft) with tip tanks Gross weight with tip tanks Fuel capacity, standard/usable with tip tanks Oil capacity each engine Baggage ca paci ty Performance Takeoff distance (ground roll) Accelerate/stop distance Takeoff over 50 ft Rate of climb (gross wl'ight) Single-engine rate of climb (gross weight) Maximum level speed, sea level ]2,000 ft 24,000 ft Cruise speed, 75% power, 8,000 ft Cruise speed, 65% power, 12,000 ft Cruise speed, 55% power, 10,000 ft Turbo Cruise 12,000 ft 24,000 ft Intt.·rmediate Cruise 12,000 ft 24,000 ft Economy Cruise 12,000 ft 24,000 ft Range, 75% cruise (45-min reserve) 8,000 ft with tip tanks Range, 65% cruise (45-min fl'serve) 12,000 ft with tip tanks Range @ Turbo Cruise (no reserve) 12,000 ft 24,000 ft Range @ Economy cruise (no reserve) 12,000 ft 24,000 ft Service ceiling Single-engine servicl' ceiling L.1I1ding distance-ground roll Landing over 50 ft Vsi (Stall speed cll'an) Vso (Stall speed with gear and flaps down) Vmc (Minimum control speed with critical engine inoperative) Vx (llest angle-of-climb speed) Vy (llest rate-of-climb speed) Vyse (Best single-engine rate-of-climb speed) Vie (Maximum landing-gear-extended speed) Vfe (Maximum flap-extended speed) Va (Design maneuvering speed) 2 Lycoming 10-320-C1A, 160 hp @ 2,700 rpm ],200 hr 2 Hartzell HC-E2YL-2, 72in 36 ft 9:5 in 25 ft 2 in 8 ft 3 in 178 sq ft 20.9 lb/sq ft 11.64 Ib/hp 6 2,416 Ib 1,309 Ib 589 3,725 Ib 120/114 gal 8 qt 250 Ib (20 cu ft) 990 ft 2,560 ft 1,590 ft 1,290 fpm 225 fpm 198 kt 214 kt 192 kt/22.6 gph 208 kt/22.6 gph 181 kt/l7.2 gph 198 kt/l7.2 gph 168 kt/14.4 gph 180 kt/l4.4 gph 946 nm ],102 nm 1,290 nm ],450 nm 25,000 ft 12,600 ft 725 ft ],900 ft 66 kt 61 kt 78 kt 78 kt 97 kt 91 kt 130 kt 108 kt ]41 kt AOPA PILOT· 73 PLOT EXPOSED nmtirlw'd smile and nod knowingly. He flies with crisp precision, with computer in lap and notebook in shirt pocket. A pencil is held delicately between the teeth. After a test flight he steps out, calm, unflustered, slips into his tailored jacket, puts the notebook, computer and pencil back into the real leather briefcase, shakes hands all around and then speeds off, smoothly, in his secondhand BMW. The words this test pilot writes soon become gospel, appearing as they do in widely read magazines. A sentence may go like this: "One of the first things I noticed about the Twin Comanche, flying solid instruments between Gumburg and Smeltville, is that the en- gines shake." What you do not read is that there was a Twin Comanche guy sitting right beside him who told him that the engines shake. I had a passenger with me recently on the over-water leg of V139 east of New York. He kept looking nervously outside at the engines. "When are they going to shake?" he asked. (It is quiet enough in a T.e. so that you can talk to people.) "Shake?" I asked. "Yeah. I read in a magazine that they shake." I put my ear against the cabin frame. "Maybe they're shaking now," I said. "We're moving close to 200 mph. What do you think?" He put his head against the panel, roll- ing his eyes thoughtfully. "Could be. I feel a vibration. Maybe it comes from the propeller going around and all that." Another time I had a schoolteacher with me. He said, "I wanted to buy a Twin Comanche, but someone told me they were underpowered and they could be overloaded easily." Underpowered? Overloaded? Ah, some sly T~in Comanche owner did his work well. As yet I have not strapped any excess baggage out on the wings; but the airplane performs with beautiful normality with anything you can stuff inside it. You have to be able to shut the doors, of course. Then there was the day I had a friend with me on a rainy, instrument flight from Jacksonville,. Florida, to Norfolk, Virginia. We were level at 7,000 feet, and an Aztec was being handled above us at 9,000. Center talked with us alter- nately as we went along. After half an hour my friend, a heavy twin man, said, "Don't you have itsy-bitsy 160-hp en- gines on this box kite?" "Affirmative," I said. "Well, when is the Aztec going to pass us?" he asked. "Oh, maybe around Kinston someplace. North Carolina," I replied. "Not until Kinston?" He looked incredulous. "Maybe Kinston." But alas. the Aztec never passed and was in the landing vectors with us at Norfolk. My friend, not quite believing 74 • SEPTEMBER 1980 it was the same airplane above us all the way, went out to watch while they took on fue!. He joined me at the counter in the flight office, looking worried. "You know, that really is the same air- plane. They filed on to Boston with the same ETA as we have." "Shhhh," I whispered, pulling him into a corner. "Sometimes a Twin Co- manche goes right along with bigger twins. Please keep quiet." "We took on only half as much. fuel-" I held up a warning hand so he lowered his voice. "We took on only half as much fue/!" "Okay, okay," I said, looking around to see if anyone was listening. The urge He had read that the engines shake. I put my ear to the cabin frame. "Maybe they're shaking now ... we're going almost 200 mph." to come clean overpowered me. I blurted it out: "We're burning 14 gallons an hour." "Jeeze, that's not bad, each engine." "No-tota!." I began to sweat. I felt purged. No more lying. Well, maybe just a small lie, because I was new at this. We were actually burning a total of 13.7, and I let him think it was 14.5. The way the Twin Comanche sips' gas can be em- barrassing. To keep from being too self- conscious, some guilty Twin Comanche owners say 16. Some even say 17. The die-hard owners won't answer. Almost every Twin Comanche owner knows what makes a test pilot say the twin will not fly leve!. lt is mostly the fault of those "itsy-bitsy" little Lycoming 160s, which not only run on forever, but even pulled back, deliver very exotic speeds. Twin Comanche owners remain mum about this. They do not mention that it is no sweat to climb out at more than 1,400 fpm. There is silence about the fact that they really dig in after you level off and that the gradually increas- ing speed is sneaky and almost imper- ceptible. The airplane becomes gleeful, feeling the speed, and wants to climb. The uninitiated test pilot thinks he is trimmed out and shoves the nose down. This only encourages those itsy-bitsy 160s further when they find the going so easy, so they start to climb again. The secret, of course, is that one of the things you do with a leveling-off. Twin Comanche is concentrate on trim- ming gently-gently by hand. Close the cowl flaps, then trim a little more. Lean the mixture, trim a little, check a little, then trim a little more. "Think of it as kissing the hand of a beautiful woman," as one Comanche Cowboy commented. Once an expose like this gets started, there seems to be no end to the perfidy. When an earnest young man, weaned on Cessna Skyhawks, came to me with trembling questions, my betrayal was complete. What about stalls? Uncontrol- lable spins? Single-engine terror? There was a time when I would have rubbed my hands in villainous glee at the chance to scare the hell out of a novice. I was within earshot of other Coman- che owners when I said, "Don't make me laugh, I have a cracked lip!" I could see them exchanging glances, but I went on to explain that anyone flying a Twin Comanche according to the standard twin-engine rules would reveal this air- plane as an everloving pussycat. There were even some weirdos, I told him, who took off on one engine when they were sure no "outsiders" were watching. I knew then I was a marked man. Now comes the diabolical part of this Comanche-owner subversion. One of the confidential whisperings heard back of the fence is that Twin Comanches are hard to land. Ah, what satanic cunning. This bit of propaganda was included with all the other gibberish because it is the only thing that is true. Well, almost true. Maybe true on Mondays, Wednesdays and Fridays. It evolves from the fact that you have to fly a Twin Comanche. The minute you let it run around loose, the airplane reminds you with its frisky free- dom. It is what makes the love affair so real and rewarding. Since my hair is down (what there is of it) I am not going to suggest the fun- loving T.e. is easy to land. It is always an interesting challenge. As when walk- ing a slack wire over the Grand Canyon, you have to pay attention. For instance, you cannot land this air- plane if you are distracted by anything, such as chewing a stick of gum. Or breathing. Or the tower saying, "Cleared to land." Or if the windshield gets too close to your eyeballs. Each time, you have to take the trouble to sweet-talk this flying wonder off its wings and onto its wheels. All this romancing is because the Twin Comanche is built exactly as an airplane should be. As long as it has flying speed, it flies. When it does not have flying speed, it quits. The solution is quite sim- ple. You arrange for the flying speed to end about 12 inches off the ground and at the same time lift the nose a lot higher than you think it should be. Then, honest to goodness, you get noth- ing but kiss-kiss landings. Kiss-kiss land- ings. Kiss-kiss landings .... 0 continued flight tests were begun under National Aeronautics and Space Administration auspices at the Langley Research Cen- ter in Hampton, Virginia. That same month Piper began printing spin re- covery procedures in Twin Comanche flight manuals, noting that intentional spins were prohibited. On September 14, the FAA issued Advisory Circular 61-40, which carried recommendations on the performance of stalls. No longer, it declared, would single-engine stalls be demo~strated on multi-engine flight tests. Though they never were required in the past, this entry is significant because it clari- Rill COIAIICHE For the money, you'd have a hard time finding a better light twin. fied an FAA position that was ambigu- ous until the Twin Comanche issue arose. "Single-engine stalls should not be practiced ip. high performance air- planes by other than qualified engi- neering tes~ pilots," the phrasing went. The bulletin also brought up engine~ out minimum control speed demon- strations, stressing that Vmc demon- strations should not be attempted when it is known that the density al- titude is such that Vmc is close to the stalling speed. "Loss of directional or lateral control just a!, a stall occurs is hazardou.s," the AC read, " ... but such loss of control when the airspeed is five knots or more above stalling, how- ever, need not be serious." Stall demonstrations, the AC contin- ued, were from then on to be per- formed at a high enough altitude to permit recovery from an inadvertent spin, in no case below 1,500 feet above ground level. Delays occurred on the wind tunnel testing program, but by mid-1969 NASA's Bureau of Aviation Safety had assembled the data. The final report would not be delivered until July, 1971. In the meantime,. the number of Twin Comanche stall/spin accidents climbed to 40, with 73 persons losing their lives. The bureau eventually reached three conclusions: • At the stall, large rolling and yawing fa P"'SI'lltillg thc ail-lieII' Pipl'r Twill Comanche! Well, it was lieII' Will' II this pllOto was takc" ill 1964. Note thc Palm Bcech paillt schcmc alld tllC Ia/ldillg lights IIcar thc Willgtips. FfATURES AID MILESTOIlES continued moments occur as a result of asymmet- ric wing stall; i.e., a large part of the left wing outboard of the nacelle stalls at an angle of attack about two degrees lower than the right wing. • The rolling and yawing moments generated by the asymmetric wing stall are larger than the corrective moments produced by aileron and rudder con- trols, respectively. • The airplane exhibits a flat spin un- der certain conditions involving the use of asymmetric power. Piper had been kept advised of the progress on the aerodynamic tests and moved on its own initiative to develop a modification kit for all Twin Coman- ches and Turbo Twin Comanches. The first kit was described in Service Letter 552, dated May 1, 1970. This entailed the installation of a new right engine with a counterclockwise-rotating (viewed from the cabin) propeller, an aileron / rudder in tercon nect system and wing leading-edge stall strips. In this configuration the left propel- ler rotates to the right and the right propeller rotates to the left. This elimi- nates the so-called critical engine, the one that most adversely would affect the performance or handling qualities of an aircraft if it failed. In con- ventional American airplanes with clockwise-rotating propellers, the criti- cal engine is the left engine because of the different thrust vector dynamics exhibited by the left and right engines. This modification could run any- where from $\,900 for a normally as- pirated Twin Comanche to $2,600 for a Rajay turbocharged model. In spite of the advantages of a balanced air- flow, more dociie stall characteristics and the absence of a critical engine, the high cost must have discouraged owners. Only 60 of these modifications were performed. Another kit that Piper offered begin- ning in July 1970, was made available to Twin Comanche owners free of charge. Described in Service Letter 558, this "airflow kit" included the instal- lation of wing leading-edge stall strips, a rudder seal strip and' the aileron / rudder inter-connect system and a re- rigging of the rudder and the stabila- tor. Piper distributors received 1,303 of these kits by May 1971, but only 843 Twin Comanches actually were outfit- ted with this kit. NASA's final report recommended that FAA issue an air- worthiness directive requiring all Twin Comanches to have the installation made. The recommendation never 76 • SEPTEMBER 1980 reached AD status, however, and the installation of these kits remains com- pletely voluntary. The only airworthiness directive to come out of the great Twin Comanche Flat-Spin Controversy was AD 69-24- 4, which required a change in the Vmc from 69 knots (80 mph) to 78 knots (90 mph). Perhaps it is a credit to the airplane The original PA-30s came in several dif- ferent variations. The Standard was just that. Bare-bones day VFR with only one generator and one vacuum pump. The Custom was a lot better: dual generators and vacuum pumps, an automatic direc- tion finder, a Narco Mark 12 nav/com with an instrument landing system in- dicator and a two-axis autopilot. If you wanted dual VORs, the ILS, marker bea- cons and an ADF. then it was the Ex- ecutive. Next came the Sportsman, which had as its big feature the all-new Palm Beach interiors and exteriors, de- signed especially for the Twin Coman- che. The top of the line was the Pro- fessional. with all the above plus DME and a transponder. You can tell the Palm Beach paint jobs by the solid-colored fu- selages and nacelles and the triangular trim. You rarely see a Twin Comanche nowadays with an original paint job. Palm Beach interiors meant leather seats. The rear seats were bench-style, and curtains were on the side windows. The PA-30B, the first model change for the Twin Comanche, came out begin- ning in 1965. The B had a wider range of options, including fifth and sixth seats and extra side windows. Tip tanks could be ordered, as well as an oxygen system, heated windshield and wing deicing and propeller anti-icing equipment. The first Turbo Twin Comanche Bs also came out with the 1965 model year. that so few of the modifications were made. Pilots by and large saw no rea- son to change an airplane that already handled so well. The only constructive emphasis to be derived from all this concentration of anxiety about the Twin Comanche's stall/spin tendencies is to fly the airplane precisely and never at airspeeds slower than Vmc- plus-five knots, unless you are in the The tip. tanks and a six-outlet, 67-cubic- foot oxygen bottle came with all turbo- charged Twin Comanches. Turbocharg- ing is accomplished by using a Rayjay manually operatep wastegate unit. To control the wastegates you use two push/pull controls located under the power quadrant. Using a vernier adjust- er, screw the wastegate controls in to close the wastegate and redirect air from the turbocharger into the engine's intake manifold. Slowly, please, or .you will overboost the engines. A glance at the manifold pressure (mp) gauges· will tell you how much power you are develop- ing as you continue to advance the turbo controls. Turbocharging permits you to develop more manifold pressure at al- titude, in effect "fooling" the engine into thinking it is operating at a lower altitude. lt also comes in handy for take- offs where density altitude is a factor. Both the PA-30 and the I'A-30B have instrument panels that leavl' something to be desired. Flight instruments are not in the standard T configuration. A drum- type directional gyro is directly above the control column and to its right is an old-fashioned black-background atti- tude gyro. The altimeter is on the left, below the airspeed indicator. Electrical switches are lined up together. all of them, and each toggle switch is identical to the other. This makes it l'asy to turn on the right boost pump instead of the - landing flare. This is an airplane that will not tolerate sloppy flying and is not forgiving once it has entered a stall with asymmetric power. While it is useful to know that the Twin Comanche has certain bad ten- dencies, it is not altogether fair to blame an airplane for accidents that were caused by questionable pilot tech- nique or training practices. It should rotating beacon or shut off the left gen- erator instead of the pitot heat, especially at night when the cabin is dark and il- lumination of this area is inadequate. It is also necessary to cock your head over to read the labels. Circuit breakers can be found under a trap door on the floor beneath the power quadrant. Aft of the circuit breaker compartment is the manual gear-extension system. To extend the gear, you put the handle (stowed separately in the compartment) alternately into each of the two sockets, pushing forward until you get a green (all gear down) light. Fuel can be drawn from either tank to either engine using the floor-mounted fuel selectors between the front seats. If the left engine is inoperative and you want to use fuel from the left wing's tanks to power the right engine, put the left fuel selector to either the Main or the Auxiliary (level flight only) position, depending on which tank you want to use, and the right fuel selector to Cross- feed. To move the selector into the Crossfeed position, you will have to push a spring-loaded guarding mechanism out of the way of the selector's travel. The panef was redesigned in 1968 when the PA-30C and Turbo Cs came out. Flight instruments went to the T, the magneto and starter switches went to a side panel of their own, the circuit breakers went to the lower right and toggle switches were replaced by inte- grally lighted rocker switches. The 10-320 was beefed up for the C models. Heavy duty Inconel alloy valves are used, and the valve guides are strengthened. Cylinder heads are heav- ier; longer-reach, cooler-running spark plugs are used; and the crankshaft and camshaft are also sturdier and better lu- bricated. Time between overhaul for the normally aspirated Twin Comanche is 2,000 hours, for the turbocharged mod- els, 1,200 hours. Another big operational improvement be remembered that flying any twin near Vmc with asymmetric power is courting disaster and that any airplane spun with an aft-located CG will ex- hibit flat-spin characteristics of one in- tensity or another. At any rate, all this bad publicity drove down sales of the Twin Coman- che. In the used airplane market, they began to sell for $15,000 or less. Piper was the introduction of simplified power settings. Only four cruise settings were recommended for each Twin Comanche model. In the C, they were Normal (26 inches/2,400 rpm), Intermediate (24 inches/2.400 rpm), Economy (24 inch- es/2,200 rpm) and Long Range (20 inch- es/2,200 rpm). The Turbo C had Turbo Cruise (28 inches/2.400 rpm), Interme- diate (26 inches/2.400 rpm), Economy (24 inches/2,200 rpm) and Long Range (22 inches/2,200 rpm). No longer was it necessary to refer to a power chart to determine settings as altitude varied. Cruise speeds went from 168 knots up to 172 knots for the normally aspirated C and from 193 knots to 208 knots for the turbos, as a result of the improved engines and the new crusie settings. In February 1970 the PA-39 C/ Rs were announced. (From this model on, all Piper light twins would have counter- rotating propellers.) Except for the coun- terclockwise rotation of the right engine, some C/R decals on the nacelles and a new paint job (bold vertical stripes on the tail section) there was no difference between the appearance of a PA-39 and earlier Twin Comanches. Service ceiling for the -39, though, went up to 20,000 feet, and single-engine service ceiling rose to 7,100 feet. In the C they stood at 18,600 and 5,800 feet, respectively. Takeoff distance over 50 foot obstacles went down, and so did the landing run for the PA-39 and the -39 Turbo. When the end came for the Twin Co- manche, Piper had been doing prototype work on an airplane they called the PA- 40 Arapaho. Intended as a replacement for the Twin Comanche, the Arapaho had dropped leading edges, longer landing gear, flaperons and other hi-lift and safety features seen in the Robertson conversions. But because it was too work intensive and expensive to manufacture, the Arapaho never made it, the Twin Co- manche slid into the past, and we got the Seneca instead. -TAH Twin Comanche Sales Deliveries PA-30 PA-39 Total 1963 64 234 438 65 66 67 259 437 259 68 69 124 230 70 15 80 71 2 43 72 21 73 o 74 1,998 ~ 2,143 continued responded by coming out with a new, improved Twin Comanche, the PA-39. These models came with counter-rotat- ing propellers and all the airflow modifications described above as stan- dard equipment. But it was too late. The Twin Comanche's negative image had dealt the airplane irreparable harm. In 1970 only 15 PA-30s were de- livered; then their production was dis- continued. That same year, the first for the PA-39 (Piper called them PA-39 CjRs-for counter-rotating-in its sales literature), only 80 of the new Twin Comanches were sold. In 1971 the sit- uation worsened: only 43 sales. By this time, work had begun on the Seneca series of light twins. With counter-ro- tating props and a large cargo-carrying capability, Piper saw the Seneca as a more utilitarian replacement for the Twin Comanche and drew attention to the safety features drawn from the Twin Comanche experience. The coup de grace came with Hurri- cane Agnes in June 1972. Both the twin- and single-engine Comanche production lines were flooded when the Susquehanna River rose, destroy- ing the jigs and tooling used to con- struct the Comanches. By the fall of 1972, rumors began to spread that Piper wanted to end production of all Comanches, and by early 1973 the final decision was made. While the Piper management no doubt felt that it was taking the right action at the time, it is interesting that Piper tantalized the flying public for a while by holding out the prospect that the company would, maybe, resume production of the entire Comanche line. But this was not to be. Though Twin Comanche owners are inclined to hold on to their airplanes, you still can find many on the market today. Depending on the model in which you are interested, you can ex- pect to pay anywhere from $21,000 for an early PA-30 with no tip tanks, tur- bocharging or counter-rotating conver- sion, to $55,000 for a 1972 PA-39 Turbo CjR. It all depends on the options. The counter-rotating conversion will add $1,500 to the airplane's average retail price; propeller de-icing, $500; and tur- bocharging, tip tanks and oxygen, an- other $700. Distance measuring equip- ment and area navigation are worth another $500 each. Recurrent airworthiness directives for the Twin Comanche center on the landing gear, aileron spars and stabilator attach bolts. The landing gear AD (77-13-21) requires a complete in- spection every 1,000 hours time in ser- vice and replacement of the bungee cords every 500 hours or three years, whichever comes first. Unless a modi- fication has been made to the aileron spars at the outboard hinge brackets, AD 77-8-1, calling for an inspection of this area every 100 hours, must be com- plied with. The stabilator attach bolts, by order of AD 74-13-3, must be in- spected for corrosion every 500 hours or three years, unless corrosion-resis- tant AN bolts have been installed. An- other aileron AD, 79-20-10, requires a 100-hour inspection of the aileron spar twill COMAIICHE Flown properly, it is no more dangerous than any other airplane. doublers, unless Piper modification kit #763893 has been installed. One AD concerns the propeller shafts and power-on stalls. AD 65-3-3 requires that the airplane be placarded not to exceed 2,100 rpm when prac- ticing power-on stalls and to have the engine inspected following any aero- batic maneuvers (including spins). Ap- parently, the gyroscopic stability of the propeller disc in high rpm ranges can cause stress on the propeller shafts when the airplane goes through sud- den G-Ioadings or abrupt maneuvers. For a complete listing of all ADs ap- plying to the Twin Comanche, write Aero-Tech Publications, P.O. Box 528, Old Bridge, New Jersey 08857 and buy a copy of their "ad List." Maintenance on Twin Comanches is best left to shops who specialize in them. Two that do are Hill Aviation in Lancaster, Pennsylvania, and Mid- west Piper in Wichita. If you really are interested in buying a Twin Coman- che, contact the International Coman- che Society (4140 Manson Avenue, S.E., Smyrna, Georgia 30080), which can provide you with more names of main- tenance facilities in your area. The so- ciety's monthly magazine, the Comanche Flyer, contains maintenance tips and personal experiences from its many members. If safety considerations are prevent- ing you from buying a Twin Coman- c y v s che and you have the money ($7,600), you can always have a Robertson con- version made. By redesigning the leading edge, in- stalling a larger dorsal fin, stall fences ~ and ailerons that droop when the flaps are extended, you can enjoy several ad- vantages. The gross weight goes up by I200 pounds to 3,800 pounds (this is one of the few Robertson conversions that result in a higher gross weight); Vmc goes back down to 69 knots; the single- engine climb rate rises from 260 fpm to 305; and takeoff, landing and accel- erate / stop distances are reduced sig- nificantly. To date, llO Twin Coman- ches have had this modification made. Want more power? Go to J.W. Miller Aviation in Marble Falls, Texas, and have the Miller Twin Comanche 200 conversion. For $56,500 you will get two 200-hp Lycoming engines, an ex- tended nose with 130-pound capacity baggage compartment, 38-gallon auxil- iary tanks, a Vmc-Iowering dorsal fin, dual brake system, 3,780-pound gross weight and a one-piece windshield. Whew! This modification boosts cruise speeds by a claimed 13 percent, and the twin-engine rate of climb goes up from 1,450 fpm to 1,900 fpm. Single- engine rate of climb jumps by almost 100 percent, from 260 to 500 fpm. Not enough? Tryon the Miller Turbo Twin Comanche 200. $73,335 gets you a near-structural-limits cruise machine with airspeeds of 225 knots. Did I hear you say you wanted the ultimate Twin Comanche rocket sled, with JATO (-jet assisted takeoff)? Then it would have to be the Miller Turbo 200 with a Robertson STOL (short take- off and landing) conversion. Think of it! Near-vertical climbs out of small grass strips to level off in a 225-knot cruise. And this is not just fantasy. The Miller and Robertson conversions com- plement each other well, though a con- firmed sighting would have to be a rare event indeed. But the Twin Comanche really does not need all this adornment to achieve above-average performance. For the money, it is the best buy in light twins today. Flown properly and with re- spect, it is no more dangerous than any other airplane. But let's face it. The hint of danger surrounding the Twin Comanche is a big part of its snob appeal, and it is probably the only airplane that can boost your macho image at the same time that you save on both gas and maintenance. 0