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August 1998

Reliable Flyer
The predictable Cessna Conquest I
eases the step-up from piston twins.

By Phil Boyer

When Pilot magazine Editor in Chief Tom Haines asked if I would write an article on the Cessna Conquest I for the "Turbine Pilot" edition of your magazine, I instantly responded in the affirmative. How could I turn down a chance to share with others the hours upon hours of dependable transportation this aircraft has provided AOPA - not to mention the love affair that seems to develop between a pilot and the airplane he or she flies some 400 hours annually? This assignment is like having to write about that comfortable pair of sneakers all of us own. We know that they have been through a lot, yet we always choose to wear them, and would find it hard to describe to others why. Let me make an attempt.
AOPA has owned a Conquest I since 1983 - well before I came aboard as president in 1991. The association leased the Model 425 new from Cessna for business travel and later acquired it outright. Cessna built 234 of the sturdy turboprops, with limited production spread over the first half of the 1980's. The original base price in 1979 was $825,000, and today a used airplane sells for between $1 million and $1.25 million, depending upon its condition and engine times. The Corsair, as it was originally named, came out in late 1979 and can be best described as a turboprop version of the popular Cessna 421C Golden Eagle.
AOPA had been operating piston twins in the Cessna 300/400 family, from a 310 to the 414. The association's reasons for acquiring the 425 mirrored those of other organizations making the transition from piston twins to turboprops: the need for better reliability. Flight departments and airlines call it "dispatch rate," but as one who travels on your behalf to fulfill speech and meeting obligations, I can assure you that it boils down to the airplane's being flight-ready when you need it.   Moving up from a piston twin to this turboprop takes less time than one ,might anticipate, and it took me no more time than the easy, 30-second start sequence to recognize the convenience of not having to deal with spark plugs and magnetos. In the almost eight years and nearly 3,000 hours that I have flown this airplane, only one trip was delayed - by only two hours - because of a mechanical problem. Such was not the case when I personally owned a Cessna 340 and could almost predict a fouled-plug every 60 days.
In 1983 the Corsair became the Conquest I, with a modification that increased maximum gross weigh from 8,200 pounds to 8,600 pounds. An unfortunate series of tail problems gave the 400 series, including the 425, a bad reputation, grounding the airplane at one point early in its history. Cessna provided a robust fix that was mandated for the entire fleet, and pilots today can rest assured that this early negative has probably provided them the security of one of the strongest and most tested stabilizer and rudder systems on this type of aircraft today. Double pushrods to operate the elevator trim tab are one of those fixes - a system required only on transport category aircraft.   The increased maximum gross weight greatly reduces the need to leave fuel behind in order to carry passengers. With four adults and luggage, the aircraft can still be topped off, allowing longer - distance trips. While the airplane was delivered with eight seats, including crew and potty seats, many owners remove the fifth seat that partially blocks cabin entry. Because the belted toilet seat is far aft and would be uncomfortable for an adult on a long trip, the 425 is basically a six seat airplane. In addition, loading six or seven people places the center of gravity too far aft, so weight has to be added to the nose baggage compartment. The 200 pounds needed up front obviously comes by lessening the fuel load.
One of the Conquest's real assets for AOPA has been the huge nose baggage compartment, which is accessible through three doors. My speaking trips require carrying around 200 pounds of audio/visual equipment, which is no problem for the Pinocchio nose on the Conquest. Actually, unless you're carrying anvils it is hard to reach the 600 - pound allowable limit in the nose compartment. In most cases you will fill the space before you hit the load limit. In addition, the rear of the cabin has two small baggage areas, which will handle an additional 500 pounds.   The fuel system is simple compared to the 300/400 series piston airplanes with tip tanks, auxiliary tanks, and optional locker tanks. In the 425, a total of 2,441 pounds (366 gallons) is held in left and right wing tanks. Fueling is done at the top of the engine nacelle and goes into a nacelle holding tank. The one disadvantage created by the nacelle tank is that with high - pressure fueling hoses, a line person will see fuel at the filler opening and consider the tank full. In reality, the small nacelle tank has been filled so fast that it can't drain into the wing. As a result, I have been short as much as 150 pounds on one side because of this design. My common phrase on the fuel order is, "top-off let it settle and refill." This gets around the problem. Also, Cessna designed a unique fuel pump system that uses motive flow once the engine has been started. Therefore, electric boost pumps are required only for crossfeed and start. In the case of a double alternator failure there are no electric pumps draining valuable minutes from the battery, as happens with other aircraft designs. Unlike that of many turboprops, the Conquest I fuel control is either on or off, not low and high idle common to may Pratt & Whitney engines.  Flying the airplane is very straight-forward, and with IFR proficiency in any of the popular piston twins, a pilot can quickly become proficient in the Conquest I. It is very stable across the CG envelope and in all speed configurations. FlightSafety International offers both initial and recurrent training in the 425, which is strongly recommended. The wide cockpit is extremely comfortable, and affords plenty of space. There is no center pedestal blocking entry to either seat. Most jets are far more cramped up front.
"Bulletproof" is the way everyone refers to the Pratt & Whitney PT6A-112 engines, flat - rated in this installation to 450 shaft horsepower. In our almost 5,000 hours of operating this airplane, with two hot sections and one full overhaul on each engine, I can attest to the phrase. They are just trouble-free. Hot sections surprised us at only $8,000 each, and originally were required at 1,250 and 2,500 hours. Recently they were extended to 1,750 and 3,500 hours. The complete overhauls are due at 3,500 hour intervals and cost about $100,000 to $117,000 each.
The flat rating gives full power up to almost 18,000 feet on a standard day and means that tail and rudder size can be kept reasonably small, while still allowing adequate control in an engine-out situation. The Pratts use a two-shaft, free - turbine design. They are slower to respond to large, quick power applications than a single-shaft design directly coupled to the propeller.
Several years back we installed the McCauley four-blade Blackmac propellers, replacing the standard Hartzell three - blade props. Although noise is not a problem in the Conquest, it was noticeably quieter after the conversion. From actual operational experience, we have seen a 300- to 400-fpm climb rate increase and a three- to four-knot cruise speed increase with this modification. The fourth blade introduces significant drag when powering back to flight idle on final. This requires holding a bit more power on the approach with the Blackmacs than on three-blade 425s.   Starting power comes from a nickel-cadmium battery that supplies sufficient power on the hottest or coldest days. A power chart is recommended below 10 degrees Farenheit, and I have used one only once in my experience with the airplane. Never leave the battery switch on, since nicads can be recharged only with special deep-cycle machines, which aren't available at all airports. And the airplane can be operated only with a battery that is within limits.
Taxiing is conventional, and you can reverse the props to help slow you down or even stop, reducing the need for normal braking. This is a real boon when operating in the winter on icy runways and taxiways. There is a go/no-go item that is required during preflight check: auto feather. It automatically handles feathering the prop during an engine failure, freeing the pilot to control the airplane.
While the pilot's operating handbook indicates better runway performance, I have limited my takeoffs to runways of at least 2,400 feet, and this is at 600 pounds below the max gross weight. Even with this self-imposed limitation you will not give up many airports if transitioning from a piston twin. On any runway shorter than 4,000 feet, I hold the brakes at takeoff until the engines run up to 900 foot-pounds of torque (1,244 is max) and then begin the roll. At a cruise-climb speed of 145 to 150 knots, initial climb rates of 1,500 to 2,000 fpm are standard, assuming average temperature and max gross weight. 

In cruise, our aircraft's air data computer consistently indicates 250 to 260 knots true airspeed, depending on temperature and altitude. While almost 10 knots better than book values, I attribute this to the Blackmacs and American Aviation's Speed Stacks. These reshaped and recontoured exhaust stacks solve a problem faced by Conquest owners and other using PT-6-equipped airplanes: messy and dirty exhaust deposits on the upper surface of the wings. To reduce the regular maintenance costs necessary to remove this unsightly and corrosive residue and in an attempt to achieve an advertised performance increase, we exchanged the stock exhaust stacks for the Speed Stacks. As with many other so-called "performance" mods, I was skeptical of the claimed speed increase, but I am now convinced that they have given us three to four more knots in cruise. They look good, keep the aircraft much cleaner, and do add speed, which can be translated to a payback of the investment in less than two years.  

The Conquest's one big advantage to those of us who have grown up in the low-altitude piston environment is that VFR flights at 16,500 and 17,500 feet are efficient and economical in this turboprop. Like any turboprop in this class, the 425 is at its best cruise speed in the high teens and low twenties. There it will burn somewhere between 420 and 480 pounds per hour. While the service ceiling is 30,000 feet, and I have had it mushing around up there a few times for weather, it can consistently cruise at FL250 and FL270 with fuel burns in the 400-pph range. Up high it is a five-hour airplane with reserves. Down in the high teens, I figure four hours, with reserves. Cabin pressure differential is 5.0 psi, which creates a comfortable 5,000- to 6,000- foot cabin in normal cruise, but a 10,000 foot cabin when you are up at FL260 stretching fuel or getting around weather. This high cabin altitude can be fatiguing on the pilots, especially after a long day. Up high, cabin heat can come from the engine bleed-air system, but this is pretty weak. So, Cessna augmented that with an electric heater and fan system. It does a pretty good job at normal altitudes, but in cold weather up high, it's just not sufficient. The Freon air conditioner, on the other hand, is excellent and can quickly cool the aircraft on all but the hottest of days.
The airplane handles ice well, shed by the pneumatic boots; and perhaps due to conventional tail, I have never had a problem with tail ice. Engine inlets are heated by bleed air, which does not rob power. In icing conditions, the only power loss comes by activating the inertial separators, which prevent any ice chunks from being ingested by the engine but also rob some of the ram air from the engine itself.   Rapid descents are not problem in a turboprop, particularly with those four blades out there. And, no piston-engine cooling problems are encountered when you pull off the power. With the efficient pressurization system, no one in the cabin can tell that you may be descending at 3,000 fpm or more, if that rapid a rate is deemed necessary. A standard three-degree descent yields about 1,250 fpm. In the terminal area 210 KIAS can be achieved, so you will rarely be asked to speed up at air-carrier airports. Earlier this year I was maintaining 180 knots in string of arrivals into Atlanta and was asked to slow down. The landing gear and 15 degrees of flaps can be deployed at 175 knots, providing a great deal of flexibility and allowing an easy fit into the traffic flow. Set up for 110 to 120 knots on final and 98 to 100 knots over the fence to assure a smooth landing. With those slow approach speeds, the Conquest I feels more like a light-plane on landing than a 2.5-ton turboprop. The prop reverse comes in real handy when you need to make short turnoffs on rollout. The 425 can be brought to a full stop in 700 feet, if necessary. You can land almost anywhere, but think about the takeoff before you use a short runway.   In service with AOPA the airplane has been flown from grass strips, snow-laden runways (actually a combination of both on one Canadian trip-look that one up in the POH), off gravel in Alaska, and on solid-ice-covered runways. The utility of the cabin baggage compartments offers a variety of loading options, important to any operator with requirements such as ours. Service is available almost anywhere for those infrequent small things that occur during trips. The 100-hour progressive inspections have been performed for us by Miller Aviation in Binghamton, New York, and I personally believe that their fine work has been responsible for our superb operating history.
One should choose an aircraft suited for the average trip length and standard missions you intend to fly- the mission profile. Obviously, my Cessna 172 has a mission profile perfect for those short trips to visit relatives and friends or for the weekend $100 hamburger. But, for flying with employees on long trips, hauling heavy equipment, and needing a 100-percent dispatch rate, the Cessna Conquest I has served our needs for more than 15 years. During my relatively recent experience in business flying, I have learned a lot about the term "mission profile." The greatest compliment I can give this fine airplane is that it has consistently exceeded its mission profile with 10 to 20 trips to the West Coast each year, Alaska every other year, small and large airports, low- and high- level operations, and more. In this regime, Conquest N39A has met and beaten our wildest expectations and served us well.  AOPA PILOT, AUGUST 1998