April 2014- The PA-23 Apache was Piper’s first twin engine aircraft. In 1952 Piper began construction and testing of a prototype, but the original design—with 125 hp engines, a twin tail arrangement and fabric covering—was unsuccessful.
The aircraft was tweaked and the new design included 150 hp Lycoming engines, retractable landing gear, constant speed full feathering Hartzell propellers, all metal construction and a more conventional single tail.
Now called the Apache, the 150 hp prototype flew in 1953. The design received its FAA type certificate on Jan. 29, 1954. There were 2,047 Apaches and 4,930 Aztec models produced from 1954 to 1982, including a few U.S. Navy models.
One certificate, many airframes
Many changes and improvements were made to the Apache/Aztec line, some of which include engine size, seating capacity, gross weight, turbocharged engines (on some Aztec models), redesigned tail and wingtips (also on the Aztec), increased fuselage length (again, for the Aztec), a different nose on the Aztec than the original Apaches, as well as various fuel tank configurations. Apaches/Aztecs and Geronimos all have the same wing, and it’s similar in basic airfoil design to that of the Piper J-3 with high lift and associated drag.
While all of the aircraft share FAA Type Certificate 1A10, they do not fly exactly the same and have different limitations and operational requirements that must be thoroughly understood prior to flying any of these aircraft or transitioning from one PA-23 model to another.
In addition to changes made to the PA-23 design at the Piper factory in Lock Haven during its 28-year production run, there were many STCs and modifications by aftermarket suppliers. Rocket motors, multiple fuel tanks, floats, a cargo door, auto fuel… just about anything that can be done with or to an aircraft, the PA-23 has seen it.
The most famous conversion for the Apache was Seguin Aviation’s Geronimo conversion. The full conversion included larger 180 hp engines, a sleeker nose, enclosed wheel doors, changes to the tail, heavier brakes, a single-piece windshield, a redesigned instrument panel and increased gross weight. There were other changes, but these were the major items offered in the complete conversion; they could also be installed as individual conversions.
The complete Geronimo conversion (now available from Montana Diamond Aire Inc.) made a very respectable, sleek looking, good performing twin out of the original “sweet potato” Apache. The Geronimo conversion almost doubles the single engine climb rate to just less than 500 fpm and increases the cruise speed by 15 to 20 knots.
The Geronimo is a much different airplane than the Apache, and in my opinion all of the good things about the Apache were retained and the undesirable aspects were engineered out in the conversion process.
Development
Design considerations
When the Apache was designed in the early 1950s, General Aviation as we know it was in its beginnings and World War II was recent history. Businesses were taking to the skies and people needed faster, more modern aircraft than what Piper Aircraft was offering.
Utility was very important in the design of the Apache; it had to be able to operate safely out of existing airfields and airports (2,000-foot grass airstrips were typical of that era) and go just about anywhere while carrying a good load at a reasonable speed and range. Realistically, what benefit does higher cruise speed mean if you can’t land at an airport close to where you want to go? The Apache could access most all airports and airfields in small communities across the country and the world.
This entry-level twin sold for $32,500 new, much less than the Cessna 310 and Beech Model 50. At that time, fuel economy wasn’t much of a design consideration other than the aircraft’s range of operation (over 1,000 miles with optional 18-gallon fuel tanks) as fuel was relatively cheap.
The Apache is truly a classic. If you have ever ridden in a 1950s Cadillac, the Apache is of similar vintage with large overstuffed seats and a very comfortable “Cadillac” ride even in light turbulence. Piper’s emphasis was on quality of construction, comfort and overall utility, not speed or fuel economy.
Construction
The Apache was constructed using the material, labor and technology that was available at the time. The postwar labor force was familiar with aircraft construction and aircraft design, and engineers and company executives had an interest in incorporating the latest techniques, including all-aluminum construction.
The original PA-23 design specified a steel tube fuselage and fabric covering, except for the wing leading edge, nacelles, fuel tank covers and nose. Piper changed the fabric covering to aluminum, but retained the steel tube fuselage structure in the cabin with all-aluminum rear fuselages. The Apache is built like a tank and for that reason many people involved in serious accidents in these aircraft have survived, especially when shoulder harnesses were used.
The wing of the Apache and Aztec is all-aluminum and no different in construction than modern metal aircraft of today. I once talked to an aviation scrapyard worker who told me he’d wanted to dispose of a damaged Apache wing and he tried to crush the wing by driving over it with a truck. The Apache wing retained its original shape!
There have been few if any problems with the design of the Apache and Aztec, with the majority of accidents the result of either pilot error or poor maintenance.
Maintenance and operation
Cost considerations
In my experience I’ve noticed that many twin-engine aircraft including the Apache have not been maintained to the same level as singles. This may be due in part to an owner’s notion that “I have two engines and props; I’ll just let it go for now and save some money.” Many years of deferred maintenance can turn a good aircraft into an economic nightmare.
Older aircraft can be very costly to repair and maintain depending on what previous owners either did or did not do. An Apache can be purchased for the price of an older 172 but this is just the entry ticket, with annual inspections (assuming some repairs and AD compliance) costing $10,000 or more.
One reason for the cost is that the high number of screws, nuts and bolts used to assemble the Apache can be difficult to remove. Just to take the plane apart and reassemble it after an annual inspection—the engine cowlings alone can take about eight hours to remove and replace—can easily take 40 man-hours, with another eight hours for routine servicing and lubrication. At $100 an hour, that’s $4,800 before any squawks, ADs or other maintenance issues have been addresssed.
Today, the pricing and availability of the Apache seems to go in cycles according to the costs associated with the latest ADs and major inspections, required replacements, and the cost of fuel. I haven’t seen an airworthy Apache for less than $25,000 in 2014. I did see one listed for $16,000, but it requires a propeller inspection (and is likely to need prop replacement). Propellers cost about $20,000 (new) and $10,000 (used) for the pair.
Systems and particulars
This is a twin engine aircraft with retractable landing gear and associated hydraulic system, two feathering propellers and two engines to maintain—as well as a gas-operated heater and at least two rubber fuel bladders. Most aircraft are also equipped with two auxiliary fuel bladders.
The engines used in the Apache are the early-style four-cylinder Lycomings that seem to last forever with little unscheduled maintenance, but when it comes time for overhaul, plan on a double whammy if both engines need major overhaul or maintenance at the same time.
The landing gear system and flaps are operated by a hydraulic system that is equipped with only one mechanical pump driven by the left engine, one manual hand pump for backup use, and a CO2 blow down bottle for alternate emergency extension of the landing gear only, not the flaps. Optionally equipped Apaches had an electric hydraulic pump as a third method of retracting (and extending) the landing gear.
Propeller issues
Probably the most significant problem for PA-23s over the years has been neglect of the propellers. The Hartzell props that all Apaches and some Aztecs were equipped with had steel hubs and aluminum blades. These propellers (as well as any other controllable pitch propeller) require regular maintenance and inspection which only can be done when the props are completely disassembled. Water can get into the hubs and cause internal corrosion which if left uncorrected will eventually cause the propeller to fail.
Propeller failures, although uncommon, did happen—and more than a few aircraft were lost when blades came off in flight. These failures were investigated and in many cases no internal maintenance or inspection had been done for at least 10 years, with some props never having any maintenance or internal inspection for 20 years or more.
A separate yet related issue includes tachometers that were out of calibration and exceeding the limitation of 2,700 rpm on takeoff. This alone would contribute to propeller metal fatigue and failure with repeated overspeed events.
In order to prevent further propeller failures, the FAA and Hartzell Propeller stepped in to mandate inspections of all of the steel hub propellers. Many of the propellers failed inspection and aircraft owners could buy new propellers and matching spinners. Back in 1997, these were offered by Hartzell at a special price of $14,995 for the pair.
The cost of new propellers was as much as the aircraft was worth (or more) and owners had little choice but spend the money or be forced to part out the aircraft for salvage value. These two major propeller ADs, 85-14-10 R2 and 97-18-02 R1, sent many Apaches and some early Aztecs to the graveyard.
While the newest styles of replacement propellers by Hartzell are AD-free at this time, do not expect to fly indefinitely without some type of inspection on these propellers.
Airworthiness Directives
Even after six decades, a third of these Piper twins are still flying. Of 2,165 Apaches built, 670 remain on the FAA registry as of February 2014. The fact that so many of these aircraft are still flying is a tribute to the excellent design of the aircraft.
There is a rather lengthy list of ADs on the Apache but nearly all of them can be traced to neglect, poor maintenance/poor operating practices, or just plain old age.
The most significant AD that has been recently issued requires inspection of the flap actuating tube for corrosion and damage. A replacement part was offered by Piper to end repetitive inspections required by the ADs.
There also have been ADs issued in regard to the fuel tanks, vents and caps. There is a problem with the fuel tanks collecting water behind wrinkles and aft corners of the fuel tanks and not being able to be drained away with the fuel tank gascolator. There were no individual drains for the fuel bladders with the original fuel tanks supplied by Piper.
At least one supplier of aftermarket fuel tanks does install an STC-approved fuel tank drain in each bladder which requires a hole to be cut into the wing. An AD was issued regarding a draining procedure for the fuel tanks which must be followed to be certain water is drained away prior to flight.
The fuel caps are vented and similar to the thermos bottle caps used on the Comanche but are not the same and are not interchangeable. Since the fuel caps are vented, any water that gets into the fuel cap and tank access area can enter the fuel system. The fuel tank door seals must be kept intact to prevent water from entering and are the subject of a recurring AD.
The gas heater installed in the nose compartment also has at least one recurring AD and possibly more depending on the model of heater installed and when the last maintenance was done to the heater.
Heaters can become damaged if not operated correctly. Always allow the heater to cool down after use by running the fan with no heat for two minutes prior to shutting down the engines and turning off the master switch.
If you don’t allow for sufficient cool down (i.e., you turn off the master switch before the heater cools), the combustion chamber may crack, and operation with cracks will allow carbon monoxide to enter the cabin heating system.
The tail section of the aircraft is another area of several ADs, one addressing the rudder trim rod. Excessive play between the rod that connects the trim jack screw and rudder trim tab can cause failure of the rod or extreme vibration, rapid uncontrolled movement of the rudder, or possibly even flutter and failure of the flight control and tail section of the aircraft. The rudder trim rod must meet minimum specifications; the trim attachment arm must not be loose; and the rudder trim hinges must not have excessive play.
In all, I counted 17 repetitive inspections, many of which have options of terminating actions with the installation of a kit or replacement part. If you can find an Apache with a clean history and most of this AD work accomplished, it might be worth investigating if you’re in the market.
The Apache is a true American classic. It offers exceptional construction quality along with comfort and utility. Its reputation is mixed, but as an Apache owner, I’m a fan. Next month, I’ll discuss flying and owning an Apache.
Michael Berry, a former aircraft repair shop owner, is a multi-engine rated ATP (757/727). In addition, he’s a turbo jet flight engineer, an A&P/IA mechanic, airplane owner and 121 air carrier captain. Berry has 15,000-plus pilot hours. Send questions or comments to editor@www.piperflyer.com.
