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Thursday, January 22 2015 00:00

Apache: Piper’s First Indian

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March 2005-

In the years immediately after World War II, General Aviation was growing—but not very predictably. Manufacturers were constantly going from feast to famine, and several old, venerable airplane companies had gone broke when they found they couldn't survive the market fluctuations.
There was one emerging market, however, in which a few of the more far-seeing planemakers were interested—Business Aviation—bigger, faster, more sophisticated (and profitable) equipment that was flown for commerce instead of for enjoyment.

Monday, September 08 2014 00:00

A total renovation of the PA-31

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In 1967, Piper Aircraft began marketing a six- to eight-seat cabin-class twin known as the PA-31 Navajo. Several variants were produced, including a T1000 series aimed at the commuter airline marketplace.
Production of the Navajo ended in 1984 with 3,942 built. Piper had—and still has—the Seneca and Seminole light twins in the lineup, but its cabin-class aircraft offerings thereafter have been limited to single engine models.
The Chieftain version of the Navajo proved popular with regional airlines, tour and sightseeing operations, plus some corporations—but most independent businessmen and small companies purchased a smaller version of the Navajo, or a variant called the Navajo C/R which had safety enhancing counter-rotating props that eliminated the critical engine problem present with most cabin-class twins.

Colemill Panther conversion
After Piper's departure from the piston engine cabin-class twin market, a Nashville, Tenn. company by the name of Colemill Enterprises began marketing an upgraded version of the Navajo.
The Colemill conversion came with 350 hp engines, four-blade Q-Tip propellers, winglets, and redesigned nosebowl cowlings. The Panther conversion established Colemill Enterprises as the source for an improved and very capable Navajo until several unfortunate events, including a flood, combined to drive the company out of business.
With Colemill's exit, access to the Panther conversion STC vanished as well and other than a new coat of paint and spiffy interior, there was little to do with a Navajo other than fix and fly it.

Lock & Key Navajo
At the start of the millennium, Mike Jones was flying turboprops for a small regional airline. After spending a long time in corporate aviation, Jones had heard the siren song of the airlines, got his ATP rating—and soon found himself hand-flying the formidable Jetstream airliner for hours and hours each day. (Back then, shoestring operations like the one that employed Jones figured that they had to have two pilots sitting up front anyway, so why spend the stockholders' money for autopilots?)
Relatively quickly, Jones rose through the ranks to the point where he could bid and hold a two-and-a-half day line between trips, and that situation gave him time to do what many airline pilots do: start a sideline business.
Jones started selling General Aviation airplanes on the side, and once that business was established, he decided that he could take a Colemill Panther conversion aircraft to the next level.
He created what became known as the "Lock & Key Navajo," a total renovation of the Piper Navajo from nosecone to tailcone—and including the Panther modification. It's an airplane that's aimed squarely at the successful businessman who wants the best cabin-class piston twin available.
Jones bought a used Navajo, sunk $350,000 into refurbishing it (including the Panther conversion), and sold it for $675,000 back in 2003. At that time, there was not another Navajo listed with an asking price of more than $350,000. Jones' airplane became the prototype for those that followed.
Providence then took control and forced Jones into a new path. His employer went broke and Jones found himself running a small business as his only source of income.
From Jones' vantage point, he had been given an opportunity. When Colemill Enterprises went out of business soon after the 2010 Tennessee flood, Jones came up with the money to buy the rights to its STCs.
Today, Mike Jones Aircraft Sales, Inc. has become a one-stop shop for renovated Navajos. CEO, CFO, Plant Manager, Advertising Manager, Demo Pilot, Test Pilot, Sales Manager, Supervisor of 15-plus technicians, and Chief Cook & Bottle Washer, Jones has his hands full—but maintains he can best supervise each and every conversion and ensure that the finished product meets his standards only if he oversees everything.
Considering the quality of each Lock & Key Navajo, it would be hard to argue the point.

What's in a name?
To sell a used airplane, dealers and brokers know they need to give it the illusion of youth. Fresh paint; a new interior; avionics that are still factory-supported; no accident history; mid-time or better engines; no fluid leaks; and no corrosion—these items are key to getting the highest price for a used airplane. If an airplane has these attributes and has relatively low time on the airframe, its condition can truthfully be called "above average" in advertisements.
Vref and Bluebook publish price guidance for "below average," "average" and "above average" examples of the various makes and models, but they have a special category for Lock & Key Navajos.
In recognition of the extra steps taken during renovation and the high quality work done by Jones' company, his aircraft have a separate listing that's higher than "above average." Consequently, they bring a premium price—plus, these aircraft appraise, finance and insure in a much different category than regular Navajos.

The process
Jones starts with a good pedigree aircraft with complete logbooks, an accident-free history and an airframe with less than 7,500 hours total time. Over the next six months, zero-time SMOH engines are installed (factory overhauled or brand-new engines are options). Zero-time SPOH four-blade Q-Tip props are coupled to the engines, and around $90,000 is spent for much-above-average paint and interior work. A new avionics package is also included.
Lock & Key Navajo does everything in-house with the exception of painting the airframe. They refurbish all interior parts, including new instrument panels and new overhead switch panels with etched identification labels. Even the throttle Go Around labels are etched into the handles.
To illustrate the attention to detail, the engine firewalls are removed and the surfaces are polished to a high gloss. They are then re-riveted and placed back in the nacelle.
New seals and windlace are installed on all doors. The wing lockers are carpeted to match the interior and resealed as well. All bright work throughout the airplane (interior and exterior) is polished to a high gloss and clear coated to protect it from the elements.
All hoses and belts are replaced; all wear-prone items like the airstair door are renovated and strengthened where necessary. Known problem areas, like the gear doors, are restored to factory-new specifications and the landing gear itself is restored to factory-specification cycle times. Everything is meticulously reviewed during the Lock & Key Navajo restoration process.
Jones then operates the airplane for 15 to 20 hours after the technicians release it. He takes it on cross-country flights to replicate the environment it will be in when turned over to the owner, and checks every system and every component's operation himself. Everything—down to the smallest light bulb—has to work to factory specifications or better, or Jones will not deliver the airplane to the buyer.
The airplane comes with a fresh annual and warranties; plus, Jones promises in writing that his shop will do the first annual after the owner takes delivery and it will cost no more than $5,000.

Is there no downside?
Well, yes, there is. Mike Jones himself admits that the cost of a Lock & Key Navajo is out of reach for many people. At $795,000 for the standard Lock & Key Navajo package, a potential customer will likely end up paying about what a new Seneca would cost once some of the popular options are added. Jones says he has sold as many as three Lock & Key Navajos in one year, but typically sells one a year.
Jones believes in the uniqueness and quality of his product, but don't just take his word for it. Owners of Lock & Key Navajos give the product glowing reviews, calling their aircraft "a fantastic traveling machine" and saying, "We could not have made a better purchase even if we bought a brand-new airplane," and "The plane is superb!"
If you're in the market for a cabin-class twin, you should check out the Lock & Key Navajo. Mike Jones and his customers have dubbed it "The Best Navajo Money Can Buy."

John Loughmiller is a 4,700-hour commercial pilot and CFII MEI-A. He lives in Kentucky with Donna, his wife of 40 years, and often commits random acts of aviation. Send questions or comments to This email address is being protected from spambots. You need JavaScript enabled to view it..

Lock & Key Navajo Renovation Program

Instrument Panel Example

May 2014- Last month, I discussed the history and maintenance of the PA-23 Apache. But as a longtime owner, I have some insights about flying and owning an Apache, too. This month I’ll focus on specific flying tips and the practical aspects of ownership of Piper’s original twin.

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.

Wednesday, April 23 2014 03:15

The PA-31 and Its Kinfolk

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November 2005- In October of 1958, Piper proposed a twin-engine version of the successful Comanche single. This was not the PA-30 Twin Comanche, planning of which had begun two years earlier but development and production of which would be several years hence (thus the skip in numeric order).

Piper initially planned for the model to be developed in California by Bill Lear, and would furnish a PA-24 Comanche airframe and two 200 hp IO-360 engines. Whether this actually ever happened is not recorded, but in 1962 the PA-30 project was given to San Antonio designer Ed Swearingen.

Wednesday, April 23 2014 03:13

Flying the PA-31

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November 2005- Our charter company operated a 1970 model PA-31-310 Navajo for several years. We purchased it out in California, took the insurance-required flight training and flew it home to Florida, making a stop in Vegas for the night, and another at the Grand Canyon, just to sightsee.

After the 15-hour ride home we thought we knew her pretty well. Six months later we had put about 75 hours on the old girl and had grown to know her even better.

Friday, April 18 2014 04:11

Piper Seneca III-V

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July 2005- One time-tested way to create a light twin is to take a single, remove the engine, and replace it with two engines on the wings. Sometimes the engines are smaller than those on the single—as in Piper’s Twin Comanche. Sometimes the engines are as powerful as that on the single—as in the Beech Baron.

Piper took the first approach with the PA-34 Seneca: it’s basically a Saratoga airframe with the 300 hp single engine replaced by two 200 (later 220) hp wing engines. The result is one of the longest-running twins in General Aviation.

The original Seneca was introduced in 1972, and you can still buy a brand-new Seneca V from Piper today. The original PA-34-200 Seneca had some problems, notably a low single-engine service ceiling.

Tuesday, December 31 2013 07:14

Seneca Chronicle Part 02

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August 2013

Piper had success with its twin-engine Seneca, but complaints of poor handling had plagued the early models and Piper had been on a quest for more power and better handling for the Seneca nearly from the outset.

Seneca II

To gain more power for the 4,200-pound (gross weight) Seneca, Piper engineers looked at the possibility of adding a supercharger. They tried out the 220 hp Franklin 6A-350-C1 as well as turbocharged engines from Lycoming and Continental. In tests the 200 hp turbocharged Continental L/TSIO-360-E performed well and was eventually chosen for the powerplant.

In-flight handling was improved by adding aerodynamically balanced ailerons, an anti-servo tab for increased rudder effectiveness and a redesigned stabilator, while ground handling received enhancements in the form of a reworked nosegear steering linkage. To keep things simple engineers chose a fixed wastegate.

Monday, December 30 2013 07:39

Seneca Chronicle Part 01

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July 2013

If at first you don’t succeed, don’t “tri” again. But Piper’s trimotor testing wasn’t all for naught.

What do you do when you’ve completed initial testing of a new version of your wildly popular single-engine aircraft? If you’re Piper Aircraft in the 1960s, you slap a couple more engines on it and try it out as a trimotor.

That’s just what happened in 1964. Piper had completed initial tests on its PA-32-260 Cherokee Six and used that airframe to attach two more engines to the wings (in this case using the 115 hp Lycoming O-235) while retaining the 250 hp Lycoming O-540 of the “Six” for the center engine.

Sunday, February 17 2013 12:25

The Smart (and Sexy!) Seneca

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July 2012

A flood at the Piper’s Lock Haven facility destroyed the tooling for the Comanche, and Piper Aircraft developed the Seneca as a replacement aircraft for its popular Twin Comanche. Employing “parts bin” engineering and following the marketing strategy of the time, the Seneca is probably most accurately described as a twin-engine Cherokee Six.

The original Seneca, however, was not regarded as a success. Handling problems and poor performance plagued the initial design.

Seneca “2.0”

In 1975, Piper introduced the Seneca II. With this aircraft Piper addressed the handling issues found in the original design, but the biggest improvement came from the incorporation of the Continental TSIO-360 engine.

This engine featured a fixed wastegate turbocharger and made the same 200 hp at sea level as the engines on its predecessor, but made 220 hp at 12,000 feet, and maintained 75 percent power all the way to 18,000 feet. The change to a turbocharged engine gave the Seneca II the performance advantage it needed to compete against Cessna and Beech.

The model further evolved as Piper introduced the Seneca III, IV and V. The Seneca V is still in production today, and still uses a variant of the Continental TSIO-360, though now it incorporates a sophisticated absolute pressure controller to manage turbo boost (as opposed to the fixed wastegate on the Seneca II).

The Seneca features aluminum construction and utilizes an electrohydraulic power pack to operate the landing gear.

Flight Characteristics

The stock Seneca II is a really good airplane. Like its Cherokee siblings, the Seneca II is somewhat nose-heavy, and with two on board in the front seats, a full-flap landing results in a very flat landing attitude. It is very stable in both pitch and roll, and it is an excellent instrument platform.

The nose baggage compartment is quite large, but limited to only 100 pounds. However, loading the plane inside the requisite CG range is not a challenge, as the CG range is nearly 12 inches at maximum gross weight. The Seneca II and later models feature a nearly 1,700-pound useful load.

The Seneca II is actually a little faster than the normally aspirated Aztec at altitudes where the turbo doesn’t present an advantage. My Seneca turned in 172 knots at 10,000 feet on 26 gallons gph (13 gallons per side) at a power setting of 30.5 inches of manifold pressure and 2,300 rpm. That translates into 70.5 percent power. Of course, go high, and you would go faster—about three knots per thousand feet faster—all the way up to about 18,000 feet.

The turbochargers do create some engine temperature management issues, and do require a deft hand to manipulate the throttles as your right hand is essentially the absolute pressure controller. It is possible to over-boost the engine, despite the automotive-type, pop off over-boost valve.

The original engines were prone to case cracking, but have been replaced by what is referred to as “heavy case” variants of the Continental TSIO-360 engine.

Details and Mods

Where the Seneca shines in my opinion is in ease of entry and exit for the passengers. The Seneca retains the huge left-side cargo door from the Cherokee Six, making access to the aft seats and cargo area—most of which are club-style (though early Seneca IIs featured all forward facing seats)—a breeze. There is no wing to climb over, no great height to heave your cargo through.

The aft seats are held in with ¼-turn fasteners, making removal a snap and creating a nearly six-foot-long cargo bay. I actually hauled a refrigerator down to a friend’s home in the Bahamas using my Seneca. Getting the refrigerator in and out of the aircraft was no problem.

Air conditioning was a factory option on the Seneca II, and was something you could not get on an Aztec.

But like the Aztec, there are all kinds of STCs available for the Seneca, from one-piece windshields and axial flow cowls, to gap seals, recognition light wingtips and three-blade propellers. Parts are not a problem, and it is no challenge to find a mechanic who knows how to work on one.

The popularity of the design is proven by the fact that it is still in production some 37 years after its introduction.

 Michael Leighton is a 7,200-plus-hour, three-time Master CFII MEI-ATP, as well as an A&P mechanic and former FAA Accident Prevention Counselor. He operates an aircraft management, maintenance and Part 135 air charter company in South Florida. You can find him online at web.mac.com/mkleighton. Send questions or comments to This email address is being protected from spambots. You need JavaScript enabled to view it..



Seneca II Buyer’s Guide 
by John Loughmiller

The Seneca II is probably the biggest bang for the buck there is in light twins right now. Not only are parts available from Piper, it has several design features that help keep the complexity (and therefore, maintenance costs) to a manageable level.


For instance, there are no up-locks to worry about for the landing gear—the retraction system is an electrically operated hydraulic pump that holds the gear in the retract position with pressure alone. This means you don’t have to crank the gear down; just release the pressure and the gear will fall down due to gravity.

The flaps are actuated by a simple Johnson Bar lever, as opposed to an electrical system with position sensors. The turbos’ fixed wastegates require pilot management rather than using an automatic controller; while some may find this feature a hassle, it’s definitely cheaper to maintain.


Seneca IIs have a recurrent AD for the nosegear. Every 100 hours, the actuator attachment mounting as well as the actual gear casting must be inspected—which takes about eight hours when done correctly. There is a second part to the AD that requires a stack up assembly to be replaced every 500 hours at a parts cost of around $150 and another five hours or so of labor.

A second recurrent AD involves the Janitrol heater which must have a leak down test done every 24 months. The usual cost is $300 to $500 for the inspection, more if anything is found to be wrong.

There’s also a 100-hour inspection of the heater required by another AD for the fuel shutoff switch.

All the other ADs should have been done some time ago and are not recurrent if done—and logged—properly.


Operationally, flight plan for 23.5 gph fuel burn at 65 percent power and 160 KIAS (at 10,000 feet). Although the airplane has a service ceiling of 25,000 feet, most operations take place below 12,500 feet.

With standard fuel tanks, you’ll be just shy of four hours to tanks dry, and five hours to tanks dry if the long-range tanks are installed.

My Seneca II has long-range tanks and the unbreakable rule I use is to always be on the ground at the four-hour point (when starting with full tanks), so there’s never a chance of running out of fuel due to overly-optimistic flight planning.

There is a Zero Fuel Restriction, so payload calculations require both a standard weight and balance plot, plus a check to make sure you haven’t violated the placarded limit that shows the weight above which the rest of the load has to be fuel.

Speaking of weight and balance, you’ll often see Senecas with a case of oil riding around in the rear baggage compartment. This is because you can go right through the forward balance limit if you have a heavy pilot or two average-weight people up front and no one seated in the cabin. Without some weight in the rear baggage compartment, you can run out of elevator in the flare and land nosegear-first. This is one reason for the nosegear AD.


Most Seneca IIs with no avionics upgrades will have a Century IIIC two-axis autopilot with altitude hold and either King or Collins Nav/Coms. If you can find one with a brace of Garmins, so much the better—but the standard IIIC autopilot is still a good one, although parts are getting tough to find. Because it’s not a rate-based system, it will handle turbulence quite well and can easily handle turns at the marker without overshoot.

The engines on the Seneca II are counter-rotating Continental TSIO-360 and LTSIO-360 models. For 1978 Seneca IIs, you will almost certainly have “EB” series engines installed which have an 1,800-hour TBO (but check anyway, since “E” suffix models have a significantly shorter TBO).


Adhere to the two-minute cooldown guidance for the turbos after landing before shutting the engines down if you want the turbos to make TBO. Also, reduce power two inches of manifold pressure at a time, and wait at least a full minute before you make the next two-inch power reduction in the descent. Cracked cylinders from shock cooling can be the result of disregarding this advice.

Patterns are generally flown at 102 KIAS downwind, 92 KIAS base, and across the fence at 80-82 KIAS with full flaps unless the wind suggests otherwise. Gear speeds and flap extension speeds are reasonable but require planning ahead—just as the gradual power reduction requires planning ahead.    


Seneca IIs are a bargain right now due to the economy. Search for an airplane with less than 4,000 hours on the airframe, less than 750 hours on the engines, and props that have been overhauled relatively recently. Have a reputable A&P do a pre-purchase inspection for you, and plan on spending around $5,000 to $8,000 for things that were not caught in the inspection.

Finally, you’ll need minimums of 250 hours total time, 100 hours multi-engine time and 25 hours in Senecas to get a reasonable rate on insurance.


John Loughmiller is a frequent contributor to Piper Flyer and has over 750 hours in Seneca airplanes. He has owned a 1980 Seneca II for the past nine years. Send questions or comments to This email address is being protected from spambots. You need JavaScript enabled to view it..


Seneca II PA-34T-200


Powerplant: Continental L/TSIO-360-E/200

Recommended TBO:


Height: 9.92

Wingspan: 38.92 ft

Seats: 6/7

Empty weight: 2,770-2,848 lb

Gross weight: 4,570 lb

Useful load: 1,722-1,800

Max takeoff weight: 4,570 lbs

Fuel capacity: 93 gal usable

Fuel capacity, w/ opt tanks: 123 gal usable

Oil capacity, ea engine: 8 qt

Baggage capacity: 200 lb



Takeoff distance ground roll: 900 ft

Takeoff distance over 50-ft obstacle: 1,240 ft

Rate of climb, sea level: 1,340 fpm

Single-engine ROC, sea level: 225 fpm

Max level speed: 198 kt

Normal cruise, 75%: 191 kt

Economy cruise 55%: 164 kt

Service ceiling: 25,000 ft

Single-engine service ceiling: 13,400 ft

Landing distance over 50-ft obstacle: 1,760-2,090

Landing distance, ground roll: 1,050-1,380


Limiting & Recommended Airspeeds

      VMC (min control with critical engine inoperative: 66 KIAS

      VX (best angle of climb): 76 KIAS

      VY (best rate of climb): 89 KIAS

      VNE (never exceed): 195 KIAS

      VS1 (stall, clean): 63 KIAS

      VSO (stall, in landing configuration): 61 KIAS