August 2013
“There are two Diwys in my life,” said Barry Colvin with a wry grin, “but only one of them is temperamental.”
He didn’t volunteer any further information, and since I had just flown his Piper PA-32-300 Cherokee Six G-DIWY (named after his Dutch wife) without encountering any problems, I didn’t inquire further into the subject!
Development
The Cherokee Six story really begins in 1957, when Piper hired leading designer John Thorp (of Sky Scooter and T-11 fame) to conduct a preliminary design study for an all-metal airplane to replace the Tri-Pacer.
At that time Piper was committed—philosophically, at least—to metal monocoque airframes, and was already building the Apache and about to introduce the Comanche.
Fred Weick, the Ercoupe designer who had joined Piper that spring, assigned engineer Karl Bergey to the project, and with input from Howard “Pug” Piper they turned Thorp’s design study into the PA-28 Cherokee, a slab-winged fixed-gear four-seat single with (on its original 160 hp engine) no more than adequate performance at maximum weights. The Cherokee was, however, unarguably the most successful postwar aircraft Piper ever built, with almost 30,000 of its many variants being produced.
Latter among these was the PA-28-235, basically a PA-28-180 with longer wings, bigger fuel tanks and a 235 hp Lycoming O-540 inside more streamlined engine cowlings. The MTOW was upped to 2,900 pounds, later increased to 3,000 pounds on the final PA-28-235 versions, but it was still a four-seater, and the market was demanding something bigger.
So the PA-28-235’s fuselage was stretched by means of two “plugs,” one 30 inches long in the cabin area to accommodate three pairs of seats. A further 18-inch section was inserted between cockpit and firewall and provides an eight cubic foot baggage compartment capable of swallowing 100 pounds of baggage or freight, with a second, larger baggage area (also capable of carrying 100 pounds) behind the rear seats.
The prototype retained the PA-28-235’s cabin cross-section, but all production versions were to have a cabin widened by seven inches; the PA-28-235’s wings and stabilator were retained unaltered.
Certification and design changes
Now a full six-seater, the prototype PA-32 N9999W first flew in 1963 with a normally-aspirated 250 hp version of the ubiquitous Lycoming O-540. It received type certification in November 1965 and immediately entered production, fitted with an uprated 260 hp “E” version of the same engine. With an original 3,200 pounds, the Cherokee Six and Cessna’s Model 206 competed head-to-head as the only six-seat fixed-gear singles on the market.
The Six found almost instant acceptance among small commercial freight haulers and air taxi firms in the United States as well as parachute clubs. It remains especially popular with funeral businesses, since it can transport a coffin with ease; it’s the only U.S.-produced single able to do so. (Piper’s print advertising even showed a Cherokee Six accommodating a piano!)
A 300 hp version, the PA-32-300, was introduced in 1966 with a fuel-injected IO-540K powerplant and an MTOW of 3,400 pounds (which was also applied to the PA-32-260 model). Over its production life about 75 percent of PA-32s built were the -300 version.
Both variants received a number of design improvements and model iterations throughout the manufacturing run. These included a redesigned instrument panel on the “B” model, featuring levers instead of push-pull engine controls. Air conditioning became an option, and an extra window aft of the third main one was added in 1974, mainly for styling reasons. The 1975 models had the fin stretched by six inches.
The 260 hp version went out of production in 1978 and the 300 hp version was discontinued a year later. The latter was superseded by the PA-32-301 Saratoga and the retractable PA-32R-300 Cherokee Lance, though the Cherokee designation was soon dropped to differentiate the two—now quite different—product lines. In 1980 the tapered outer wing panels which had been added to the entire Cherokee series also found their way onto the Saratoga and Lance.
Early in its production run the Cherokee Six was certified for floatplane operations using Edo-Aire 3430 floats and redesignated PA-32S-300. The original development aircraft, N3214W, was damaged in an accident and replaced by N3218W. The floatplane version was not particularly successful, however. It was difficult to operate with just a single door at the front, especially if conditions demanded an approach to the dock on the pilot’s side.
Once floatplane certification had been achieved, Piper used that same aircraft (now converted back to a landplane) to produce a single prototype PA-32-300 COIN (counterinsurgency) derivative, with four hardpoints under the wings for guns or bombs.
In early September 1965, N3218W was flown to Eglin AFB for the live firing of the 2.75-inch folding fin unguided rockets, 7.62 mm six-barrel machine guns, 272-pound general purpose bombs and 250-pound napalm bombs. Unfortunately, no contract was forthcoming from the USAF and the quasi-military Cherokee was never put into production.
Mirroring the Twin Comanche’s development from the single-engine model, Bill Piper’s son Howard’s intention was to produce a six-seat, multi-engine version of the Cherokee Six.
As soon as it was released from development and certification work, the first prototype N9999W was converted into a trimotor by grafting two 115 hp Lycomings onto the wings, Twin Comanche-style, while retaining the original 250 hp engine in the nose. It first flew in this form in May 1965 but with the center engine shut down, the two outboard engines proved not sufficiently powerful enough.
All three engines were subsequently replaced by 150 hp Lycomings driving fixed-pitch propellers—but again the concept was abandoned as, with one engine shut down, the drag of the unfeathered prop made performance unacceptable. The cost and complication of three variable-pitch, feathering propellers was also unacceptable.
Piper reverted to a conventional twin-engine 180 hp Lycoming arrangement while retaining several Cherokee components and designated the resulting type the PA-34 Twin Six. Subsequent development models were powered by a pair of 200 hp Lycomings and, with a retractable undercarriage replacing the prototype’s fixed version, this Cherokee Six derivative finally entered production as the PA-34-200 Seneca in 1971.
Thus the Cherokee Six has played quite a pivotal role in the Piper lineage; as a genuine workhorse in its own right it has also deservedly acquired a loyal following. It is one of very few single-engine aircraft capable of lifting its own empty weight in fuel, freight and bodies. With five seats removed to convert it into a mini-freighter, the flight manual quotes an empty weight of 1,707 pounds, leaving a useful load of 1,693 pounds—almost parity. I have heard of several occasions where a Cherokee Six has been flown with somewhat more than its “official” usable load without detriment to either performance or handling.
DIWY’s features
The subject of this flight test, G-DIWY, began life as an N-registered PA-32-300B (N8931N) before being exported to Germany (D-EHMW), then Denmark (OY-DLW) from where its owner Barry Colvin acquired it in 1993. It was then treated to a bare metal strip-down and respray along with a total interior refurbishment by Scanrho Aviation based at the East Winch airstrip in Norfolk, England, where Colvin keeps his aircraft. The resulting immaculate condition of the whole aircraft belies the fact that it first rolled off the Vero Beach production line as long ago as 1969.
On first encounter, the almost 28-foot-long Cherokee Six appears quite a substantial aircraft for a single, and looks almost too long for the relatively stubby 32.8-foot slab wings. These are twin-sparred, and attached to the fuselage through an integral carry-through box spar, with further attachment points for the rear spar and an auxiliary front spar. The airfoil section is a laminar flow NACA 654-415, with its maximum thickness 40 percent aft of the leading edge.
The wings contain four fuel tanks with a total capacity of around 84 U.S. gallons, divided between two main (and easily removable) wing tanks and two resin-impregnated fiberglass tiptanks, each containing 25 and 17 U.S. gallons respectively. The tiptanks aren’t like those of a Cessna 310 or 340; rather, they form part of an ordinary-looking rounded wingtip.
The manual gives the interesting (and reassuring) information that the fuel in each tank is useable down to the last pint. It is fed through a large and clearly-marked five-position (four tanks, plus “off”) fuel selector mounted below the power quadrant in the cockpit, then routed through a Bendix RSA-5 fuel injection device that supplies the Lycoming via a clever system which measures airflow, and uses the resulting information to operate a servo valve and accurately regulate fuel flow.
This makes it possible to maintain metering pressure above vapor-forming altitudes, at the same time requiring a fuel inlet pressure sufficiently low that a normal diaphragm fuel pump can be used. All this means that cockpit workload is simplified, leaving the pilot only to regularly monitor and select the appropriate fuel tank to keep the aircraft in lateral trim during long flights.
Piper retained the traditional Cherokee single starboard door for cockpit access, but added a further door on the opposite side just forward of the three pairs of seats. Later models (including the example tested) have an additional 16 x 22-inch baggage hatch installed just behind that rear door, giving a huge access area to the 20 cubic foot baggage area and rear cabin. Both front and rear baggage hatches are secured in the open position for loading by a Dzus fastener-equipped fabric strap.
The sturdy spatted fixed undercarriage uses three identical Cleveland 6.00 x 6 wheels with Cleveland double disc hydraulic brake assemblies on the mains. The brake system is operated by traditional toe brakes on the rudder pedals (pilot’s side only, though dual brakes were an optional extra), with a short, stubby fly-off parking brake emerging from below the instrument panel just by the pilot’s right knee.
To set the parking brake, one simply pulls back and presses the button, when the handle remains as set. A further pull and release without touching the button releases the brakes, which are more than capable of holding the aircraft unassisted against the preflight engine runup. Tire wear is easily checked, as some three to four inches of the lower part of each wheel are visible below its spat.
The flaps are mechanically (hooray!) operated by a long lever mounted centrally on the cockpit floor and have three extended positions: 10, 25 and 40 degrees. These are defined by detents, which to overcome one must press the button at the end of the flap lever, very much as a car hand brake operates.
Also centrally mounted is a large black knurled plastic trim wheel, operating in the logical sense (i.e., roll back for nose-up trim) which operates a long anti-servo/trim tab on the rear all-flying stabilator.
Having flown hundreds of hours ahead of such an arrangement, I much prefer an all-flying tailplane to a fixed version with an elevator. In my humble opinion it gives a better feel, more positive warning of an impending stall, is always at the optimum angle of attack (thus creating less drag), and can cope more effectively with a wide range of CG positions—essential for an aircraft which might be flown solo one day and with seven occupants the next.
“Seven?” I hear you ask. The Cherokee Six can be fitted with a small jump seat between the two rear rows, making it a true seven-seater, though to be fair this seat is only really adequate enough to hold a child. But with a standard (i.e., six seats installed) useful load of 1,623 pounds you can emplane six 168-pound adults into the PA-32 and still have enough margin to uplift over 500 pounds of fuel and baggage (though taking on the maximum 84-gallon fuel load would soak up almost all that amount).
Although a check should be made beforehand to ascertain the correct weight and balance figures, in practice the Six is surprisingly uncritical in this respect, helped by having that 100-pound forward baggage compartment. Make no mistake: the Cherokee Six is a serious load hauler and long-distance touring machine. Some later variants offered optional club seating for the four rear passengers, whose windows are equipped with curtains to block out strong sunlight at the above-cloud altitudes the aircraft might routine attain. Barry Colvin has even provided in-flight video/DVD entertainment to keep his young family occupied during longer trips.
Interior features, startup
The cabin is provided with a simple heating and defrosting system controlled by two sliding levers on the right lower panel. Each seat has its own heater outlet, while individual adjustable fresh air bull’s-eye vents are situated in the cabin roof, one above each occupant, fed by a forward-facing inlet atop the center fuselage.
The instrument panel is pretty much standard, with two rows of main gauges and instruments ahead of the P1 position, radio/avionics including the obligatory GPS positioned just right of center, and two lower subpanels extending the width of the cockpit containing fuel and engine health gauges, circuit breakers and such. The lowest subpanel also carries a combined fuel flow/manifold pressure gauge and a tachometer.
My only criticism of the otherwise well-laid-out panel is that these were just a little too low for comfort, requiring a conscious look downward in the scan to monitor them—not such a good thing during IMC or close formation flying. The autopilot and nav coupler are also mounted on this lower subpanel, but as they are almost a “set and forget” item, their position is not so critical. A further small panel on the left cockpit wall houses switches for the master, fuel pump and landing/strobe lights.
The starting sequence contains nothing unusual, simply requiring the master switch to be turned on, the appropriate fuel tank to be selected, the fuel pump to be activated to build up pressure, and the ignition key to be rotated, remembering to press it in for the last section to activate the starter motor.
The fuel-injected Lycoming is usually started with the mixture in “Lean cut-off” and pushed rapidly to “Rich” when it fires up. This normally occurs within a dozen or so rotations of the beefy 80-inch diameter two-blade Hartzell propeller, depending on whether the engine is cold, warm or hot, whereafter the Lycoming settles into a satisfying throaty six-cylinder tickover.
Preflight checks include the usual prop exercising, which brought about a significant drop in rpms, though the mag check only resulted in a maximum reduction of 100 rpms, showing the engine (at least on the tested example) to be in good shape, with good oil pressure and normal temperatures.
Takeoff
Taxiing the PA-32 is straightforward as the nosewheel is directly connected to the rudder pedals and has a 30-degree turning arc either side of center, though initially I found it needed a firm bit of boot to get it all the way round. Maybe this was because we were only two-up; with passengers in the back, it would be less heavily loaded.
Both wingtips are easily visible from either front seat, so clearance while taxiing is no problem. The ride from the wide-track, long-wheelbase undercarriage is comfortable, even over taxiway potholes, and elicited no undue pitching moments. Colvin routinely flies from less-than-smooth grass strips without difficulty.
Takeoff, with one stage of flap selected, requires a fairly hefty initial push on the right rudder to counteract the torque of 300 willing horses. Rotation at 80 mph came in just under 10 seconds. Although the need to maintain visual contact with the photographic Cessna 172 ahead of us restrained our climb rate on this occasion, a fully loaded Cherokee Six will ascend at over 1,000 fpm at its best rate of climb speed of 105 mph (the Piper airspeed indicator is marked in statute miles).
For a maximum climb gradient soft-field short takeoff (e.g., to clear the standard 50-foot tree) the manual recommends the 25 degree flap setting and a climbout at 95 mph, while a more relaxing cruise-climb 115 mph should be pegged. Once past 500 feet the flaps can be retracted and thereafter the electric fuel pump switched off. In the climb the Cherokee Six needs some right rudder all the way up to maintain balance (no rudder trim is fitted), though any pitch forces can be eliminated with the trim wheel.
That big black trim wheel also has to be rolled quite a long way forward once the desired altitude has been reached to achieve a straight-and-level setting in the cruise. It felt somewhat undergeared, but once in balance the Cherokee settles down and can be flown hands-off in calm air.
In any event, it’s got a wing leveler and nav-coupled autopilot, so the proud owner can play airline pilot if he’s so minded, making heading changes using the big bug on the direction indicator and further reducing cockpit workload. Nor does he or she have any added complications such as cowl flaps to worry about; in truth the big stable Cherokee Six is almost as simple to fly and operate as a flying club’s PA-28.
Flight characteristics
On the day of my test flight the air was as smooth as one could wish for, but with its high wing loading and long fuselage the Cherokee Six is renowned for remaining fairly unruffled in turbulence. At optimum altitude the Cherokee Six has a claimed maximum true airspeed of 174 mph, though many owners dispute this figure.
Setting “25-square” (25 inches manifold pressure; 2,500 rpm) at 6,500 feet I got an indicated airspeed—corrected for altitude on the airspeed indicator’s adjustable outer scale—of 158 mph. To save wear and tear on the engine and reduce fuel flow, Colvin routinely operates his Cherokee Six at 23 inches and 2,300 rpm. This showed a cruise just a needle’s width over 150 mph and allows a comfortable with-reserve range (according to the manual) of 1,000 statute miles.
The differential ailerons aren’t the world’s most responsive, giving a roll rate of some 70 degrees per second, but they are perfectly adequate. In a steep turn I was able to reach some 70 degrees of bank before any top rudder was needed to support the nose.
Slowing to investigate the stall, I found it needed a positive firm pull of the yoke to slow the Six down and maintain height. The clean stall occurred just below 70 mph indicated, when the nose fell, somewhat reluctantly, straight down with no wing drop and was preceded by some trembling of the yoke. The stall warner, a red light situated on the panel immediately in front of the pilot, began flashing about 10 mph before the actual stall; no aural horn is fitted.
With full flap the stall was reduced to 63 mph indicated airspeed. After the initial stall I continued to hold the yoke fully aft. The nose came up briefly, nodded, dropped again, and we continued descending in a series of nods and stalls with the yoke still fully aft and with no hint of a wing drop—provided the slip ball was kept in the center.
It’s good to discover that the Cherokee Six retains the lovely docile stalling characteristics of most early Piper singles, right back to the dear old Cub—and that’s impressive for such a big airplane. Correct recovery from a further stall had us back into balanced flight with a loss of less than 100 feet.
At the economy cruise setting the Cherokee Six simply snores along contentedly while covering the ground at a respectable rate. The cockpit is relatively quiet even without headsets, though later models feature thicker windscreens and even better sound deadening. The newly reupholstered seats are very comfortable.
Visibility is perfectly adequate except directly below or upward, though even the latter part of the sky can be examined by craning forward to the steeply raked windscreen. Look backward as you fly along and there seems to be an awful lot of cabin behind you—especially if you’re more used to four-seaters, as behind the rear pair of seats is that further capacious 20-cubic-foot baggage compartment.
Approach and landing
Circuit and landing procedures are dead simple. With no cowl flaps or undercarriage to worry about, the power and prop can be retarded either in the overhead or downwind leg. Flap-limiting speed is a useful high 125 mph, so I deployed the first stage downwind at 110 mph, the intermediate stage on base and full flap on finals, each setting requiring the trim wheel to be rolled back to reduce the yoke pressure. Final approach was flown at 90 mph with just a trickle of power to arrest the sink rate.
I carefully experimented with a couple of seconds of hands- and feet-off flying as we descended toward short final without occasioning any anxiety, further confirming the Six’s splendid stability. The throttle was only finally pulled fully back as we came over the numbers.
The subsequent flare (at least, in the forward CG position in which we were operating) was again a firm and positive affair, but the Six responded by rotating nicely into the landing attitude and meeting the tarmac with little drama and no bounce.
Applying power for a go-around, the advantage of mechanically-operated flaps is apparent, as there is no delay while they motor back to takeoff setting. Essaying a short-field landing for my second (full-stop) touchdown, the Cherokee Six was happy to come down at last, with a touch more power, at 85 mph indicated airspeed. Once down the brakes were applied firmly but without eliciting any squeaky protests from locked wheels.
From touchdown to full stop used up less than half of Bourn Airfield’s 2,000 feet of slightly bumpy tarmac (the manual says it can be accomplished within 650 feet) in almost nil-wind conditions.
In closing
There is no doubt that the Cherokee Six in its 300 hp guise is a very capable and versatile aircraft indeed, and fully deserves the loyalty it has earned from its (mainly small U.S. commercial) owners and pilots. A total of 3,876 were produced at Vero Beach of which almost 2,400 were the 300 hp variant.
The entire Cherokee series has been plagued with ADs over the years. While none have been catastrophic, there are a number of niggling ones on the fuel system, especially relating to fuel tank sealant deterioration, which need to be closely investigated by prospective purchasers. (See Questions & Answers on page 18 for more on the Cherokee Six 300. —Ed.)
Despite that, the Cherokee Six is a relatively cost-efficient machine to operate. At an economy cruise setting and properly leaned out at optimum altitude, DIWY burns around 14.5 U.S. gallons per hour. For a six/seven-seater serious load hauler, I’d say that was a pretty impressive statistic. But not only that: the stable, almost docile Cherokee Six is as simple to fly and operate as its smaller brethren, has excellent short-field performance characteristics and an enviable safety record, including a rate of stall accidents among the lowest of any airplane (hardly surprising, with the Cherokee wing’s notable reluctance to stall).
Okay, so it’s not the quickest 300 hp airplane around, but it’s about the most willing all-round workhorse in its class that I’ve come across so far. I like it.
Peter Underhill was a graduate of the Rolls Royce Engineering Apprentice School and subsequently worked for the company for many years. He loved flying and owned a variety of aircraft. Underhill was an active member of the UK’s homebuilding movement. He went on to become a regular contributor to the UK’s leading General Aviation magazine, Pilot, where he wrote a wide range of flight test articles in his own inimitable style. Send questions or comments to editor@www.piperflyer.com.
