Piper PA-31T Cheyenne II Pilot's Operating Handbook

of the Cheyenne's stability.]n 1984, Piper paid $12 million to settle two lawsuits that arose from the Shannon and Harrisburg accidents. These alleged that the Cheyenne was an unsafe design, that Piper knew it before bringing it to market, and that the company lied under oath and destroyed evidence. Though the Nationa] Transporta- tion Safety Board named incorrect loading (i.e., aft of the approved CG range) as the probable cause of the Harrisburg crash and found no unsafe conditions in the design, certification, or manufacture of the Cheyenne, the damage was done. Properly loaded and flown by properly trained pilots, the Cheyenne is a safe airplane. But the SAS and pitch-stability contro- versies still haunt the airplane. For some, the Cheyenne's snappy con- trol responses are something to be feared. For others, they evoke a fighter-like controllability that complements the airplane's aura of high performance. In 1978, Piper came out with another version of the Cheyenne, the Cheyenne I. In acknowledg- ment of the original Cheyenne's ~ faults, the I was given less power- ful, 500-shp PT6A-ll engines, and its aft CG limit was brought 2 inch- es forward. Because of the reduced power, initial climb rate dropped by almost 1,000 fpm compared to the original Cheyenne, and maxi- mum cruise speed fell by 40 knots. However, the Cheyenne I's changes allowed the airplane to be certified without an SAS. To sweet- en the deal, the Cheyenne I average equipped price was about $62 I ,500-some $100,000 less than a 620-shp Cheyenne. A standard Cheyenne I came without wing-tip fuel tanks, but they were available as an $8,600 option, and almost everyone anted up. At the same time, the original Cheyenne was renamed the Cheyenne II. Nothing much changed but the name, though many still think the Cheyenne and the Cheyenne II are two different airplanes. They aren't. The cabin interior was widened by 3 inches (by recessing the sidewalls and armrests), the glareshield was lowered to give better visibility, and other minor changes were implemented over the Cheyenne/Cheyenne II's life- time. But the SAS, the engines, and the CG envelope remained the same. For the 1980 mode], a bobweight was control column to fly slower than trim speed, release the controls, and an air- plane is supposed to nose over and return to trim speed. Push forward and release, and an airplane's nose is supposed to rise until trim speed is regained. The pre-certification Cheyenne did neither. Rather, the airplane didn't seek a trim speed at all in this critical condition. Instead, it was at what aerodynamicists call the stick-free neutral point, which is a dangerous place to be at any time, let alone at high angles of attack, such as during takeoff or go-arounds. Control forces were very light, meaning that if the pilot pulled back and let go, the Cheyenne stayed at the new airspeed without giving the pilot the feeling that he was pulling-or pushing- away from the trim airspeed. Pitch control was still effective, but the con- trol fee] didn't meet the regulatory requirements. Enter the SAS. When this system detects low airspeed and high angle of attack, it activates a variable-pressure elevator downspring to provide the proper control feel. Piper designed the SAS so that when the Cheyenne's air- speed drops below 125 KIAS, the downspring begins applying forward pressure on the control column. At 100 KIAS,the downspring exerts maxi- mum nose-down force. To back up the SAS in case of a failure, an emer- gency system is provided. To activate AOPA PILOT· T-3 added to the elevator control linkage, which improved pitch control feel and allowed Piper engineers to reduce ele- vator area and the size of the SAS's downspring. In 1981, auto-ignition was first offered as an option. Operationally, two revealing changes were made to the Cheyenne II's pilot's operating handbook: a climb power limitation of 500 shp and a minimum climb speed of 120 KIAS. The 500-shp rating is the maximum power of the SAS-Iess Cheyenne I; 120 KIASmarks the entry-should the SAS fail-into the dangerous stick-free neutral zone of the flight envelope. Cheyennes I and II were manufac- tured from 1978 to 1983. The Chey- enne I, with 189 sales, formed a solid niche but was no match for the II's impressive sales record of 343 air- planes. Apparently. the doomsayers T-4 • JUNE 1993 •For an aging airplane, the Cheyennes have rem£lrkably few m£ljor m£lintenance problems or airworthiness directives. had little effect on the II's popularity. The Cheyenne IIXL, manufactured from 1981 to 1984, is basically a Cheyenne II with a 2-foot stretch-all of it forward of the main spar. This for- ward movement of the airplane's empty-weight CG, along with a climb power limitation of 500 shp, allowed the IIXL to be certified without the SAS. The IIXL is also the most versatile load-hauler of all the early Cheyennes. It's possible to fill up all eight of the IIXL's seats (with 170-pounders, that is), put 200 pounds each in the nose and aft baggage areas, still be within the loading envelope, and be just 20 gallons shy of full fuel. In this condi- tion, you could take off, climb to 29,000 feet, cruise at 250 KTAS or so, and have an 1FR range of about 1,170 nautical miles and an endurance of 4 hours 30 minutes. A total of 81 IIXLs were sold. The Cheyenne lA, a slightly modi- fied version of the Cheyenne I, came along in 1984. Wing-tip fuel tanks were standard with this airplane. and so were redesigned engine air intakes . and elongated exhaust stacks. Com- ~ pared to the I, these engine improve- ments gave the IA up to 12 more knots at the lA's service ceiling of 29,000 feet and about 6 more knots at maximum I cruise power and 12,000 feet. As with the Cheyenne I, there is no SAS. The lA's intakes were tailored for better recovery of ram air and, there- fore, greater propeller efficiency. Part of the redesign involved reshaping the intakes for better air velocity; another change gave the oil cooler its own airscoop. In the I, intake air from a single scoop is shared by hoth the engine and oil cooler, which deprives the engines of the full benefit of the incoming ram air. With just 20 sales, the IA is the rarest Cheyenne. Production was halt- ed after just one year of production. Thanks in large part to the SAS con- troversy, today's price for an early Cheyenne is approximately half the new price, making it affordable to more shoppers and even more com- petitive with the C90-series King Airs of the same age. The C90s of 1974 to 1985 now sell, on average, for about $100,000 more than the Cheyennes of that era. The 450-shp, PT6-powered Model 425 Cessna Conquests (built from 198 I to 1986) sell for about the same as a Cheyenne of comparable age but cruise up to 20 knots slower. The 635-shp, Garrett-powered Model 441 Conquest (built from 1978 to 1986) can go for up to $500,000 more than a Cheyenne. The Commanders-with the excep- tion of the Modell OOO-are also com- parable in price to the Cheyennes. The 1000 still fetches about $1.2 million, but with its 820-shp engines, it's really not in the same league as the early Cheyennes. MU-2s, on the other hand, go for anywhere from $100,000 to $200,000 less. That's because safety has been an issue with these airplanes, too-but that's another story. Take a high-performance turbo- prop twin at a bargain-basement price, add a macho pilot with limited experience and training, then toss in an engine failure, IFR weather, or any kind of distraction. That's a recipe for a bad accident rate and a scenario that closely matches the accident history of the Cheyenne-the MU-2 as well, for that matter. The record shows that. when it comes to safely stepping up to turboprops, there is simply no substi- tute for a regimen of structured recur- rent training. The courses offered by outfits such as FlightSafety Interna- tional and SimCom, which include AOPA PILOT· T·5 extensive classroom and simulator time, are excellent for obtaining and maintaining Cheyenne proficiency. A look at the AOPA Air Safety Foun- dation's general aviation accident data- base for the years 1982 through 1990 shows a total of 27 Cheyenne acci- dents. Eleven of them involved fatali- ties, and all but one (a Cheyenne I that had a midair collision) of these crashes were of Cheyenne/Cheyenne lis. Six of the II fatal crashes occurred during instrument approaches, all of them associated with a loss of control or a failure to follow published procedures; two happened during or after missed approaches. Engine failures preceded two of the loss-of-control accidents. In one case, a pilot shut down the good engine prior to crashing. Two fatal accidents were of the classic stall/ spin variety during turns from base to final. Another was a night VFR-into-IFR situ- ation where the pilot flew into a fog bank on short final. The remainder of the Cheyenne fatals were controlled descents into terrain, also at night. Among the remaining 16, nonfatal Cheyenne accidents, there were three gear-up landings, a landing-gear col- lapse, a landing short of the runway, a decompression caused by a failed window, a ditching due to fuel starva- tion, a hard landing aggravated by an open nose baggage door, a midair in which there were no injuries, and some directional control problems during takeoff or landing. For an aging airplane, the Chey- ennes have remarkably few major maintenance problems or airworthi- ness directives. According to Jim Salentano, chief of maintenance at Columbia Air Services in Groton, Con- necticut (a Piper distributor and Cheyenne service center), "The biggest maintenance problem for the older Cheyennes is 110 maintenance. "A lot of owners take their airplanes to shops unfamiliar with the Cheyenne, so many items on the rec- ommended maintenance schedule get neglected," Salentano said. "Then, by the time a Cheyenne service center sees it, the airplane needs a whole lot of corrective work." Citing one common example, Sal- entano mentions the Piper-recom- mended special inspection procedure for the fuel bladders. Every two years or 2,000 hours, the bladders are sup- posed to be opened and cleaned, but apparently, it's a procedure that's T-6 • JUNE 1993 rarely done. "I've seen everything in those fuel cells," Salentano says. "Jelly-like masses of microbial gunk 4 inches deep, packs of cigarettes, ball point pens, even a newspaper." Other recommended procedures include starter-generator overhauls every 1,000 hours and replacement of the SAS downspring pivot points every 2,000 hours. Other SASmaintenance is also very common. The angle-of- attack vane's potentiometer often fails. ("I replace about one a week, on average," says Salentano.) Periodic adjustments of the elevator down- spring pressure are also required. The SAS's angle-oj-attack vane. •For both individual and corporate owners, the early Cheyennes make sense as step-up purchases. A repetitive AD on the Cheyenne's Janitrol heater can be a real headache. To check for cracks in the burner cans, the heaters must undergo a leakdown test every 100 hours. After being pres- surized, the cans can't leak more than I psi per minute. If they fail this pres- sure decay test, the heater must be replaced, at about $2,000 a pop. Contamination of the air condition- ing system can be yet another prob- lem. Over the years, contaminants enter the system, causing corrosion and damage to components. Structurally, the Cheyennes have weathered well over the years. Corro- sion of the airframe has been rare, thanks to Piper's use of extensive anti- corrosion treatments and epoxy primers. There are reports of wear at the elevator hinge points, which require affected elevators to be removed and their hinge bearings be replaced. Cracks in the landing-gear doors are also common. So are failed inertial separator transmission jackscrews in the PT6 engine's air intake system. The most serious service bulletin concerning the airframe asks that Cheyenne elevator butt ribs (those at the inboard end of the elevator) be inspected for cracks every 500 hours, unless four external reinforcement patches are installed. Parts availability for older Chey- ennes hasn't been a problem. Piper still stocks a large number of parts, but if a Cheyenne part is unavailable, Piper will still make you one. Howev- er, you'll wait two to four weeks to receive it. A healthy salvage network can provide customers with all man- ner of non-life-limited parts. So when looking for an early Cheyenne, look for one that's been maintained by one of the 21 Piper dis- tributors (in the Cheyenne's salad days, there were more than 200 Piper- approved service centers), and one that has the paperwork to prove that the maintenance was thorough . The search shouldn't be too diffi- cult, and now is a good time to buy. The recession has driven prices down, and availability is generally very good. From November 1992 through March 1993, some 55 Cheyenne/Cheyenne lis were up for sale; 26 went for an average price of $425,000. There were 21 Cheyenne IlIAs on the market; 15 sold at an average of $440,000. At the same time, there were 10 IIXLs for sale, and three went for an average of $700,000. Those are average prices. For a beat-up Cheyenne with run-out engines, prices will naturally be lower-as low as $270,000 for a 1974 Cheyenne and about $585,000 for a I1XL, according to the latest Aircraft Bluebook-Price Digest. For both individual and corporate owners, the early Cheyennes make sense as step-up purchases, as long as the combination of low price, low maintenance, and high performance remains in vogue. If you train for and respect the airplane's high perfor- . mance, understand the II's loading ~ limitations, and look beyond the SAS brouhaha, the Cheyenne will reward you with pleasant handling, great capa- bility, and classy ramp presence. 0