July 2015

The “modern classic” Comanche is perhaps one of the most modified airframes in GA today!

So you are looking for a Comanche. This advertised airplane looks good, but it’s way overpriced when you check the Aircraft Bluebook… or is it? In the world of used aircraft, especially models more than 50 years old, it is hard to establish what an “average” aircraft really is.

The fact is, there are no stock Comanches in today’s world! In order to make sure you are comparing apples to apples, let’s take a look at what might make one particular Comanche more desirable than another.

Comanches were built from 1957-1972 and came in many flavors: 180 hp, 250 hp, 260 hp, 400 hp and twins in both conventional and counter rotating models.* The Comanche airframe is perhaps one of the most modified of the “modern classic” GA airframes.

The zinc chromated airframe is solid, but had some areas that could be improved relatively easily, thus giving advent to the myriad of modifications that are available for them. These aftermarket changes can be broken down into three basic areas: speed mods, product improvements and gadgets.

Speed Mods
Speed mods could be an article all unto themselves. Let’s face it: if the claims of all of the kit manufacturers were truly additive, some aircraft out there should be supersonic at this point. Given that, they are not all snake oil either. They do work, but in order to get the maximum bang for the buck, you need to know how they work.

Under wing mods
For our discussion I’ll start by looking at the under wing modifications. These primarily consist of aileron and flap gap seals, gear spats/lobes and flap track fairings for the electric flap-equipped birds. All of these are designed to smooth airflow, thus reducing drag and enabling a higher airspeed.

Gap seals are probably the best bang for the buck, but they don’t do much at sea level max power. (If this is the flying you do, save your money for Avgas!) However, if you climb high and go a fair distance on every flight, gap seals can work wonders.

The slower the indicated speed, the more effective gap seals are. They increase the effective wing area, reduce drag at higher angles of attack and keep the high pressure air under the wing where it belongs, instead of shooting up between the ailerons and flaps causing a wind curtain spoiler effect right in front of the control surfaces.
Net result here is significantly increased climb rates, and essentially a raising of the optimum altitude for speed by about 1,500 feet. Subsequent to the altitude comes a resultant efficiency gain in not using as much horsepower (fuel) to go the same speed.

Next up are the gear lobes or speed spats. Like most retractable Pipers, the main gear wheel well is open and plugged with the main tire when the gear is up. Because of the shape of the wing and the retract geometry, the trailing edge of the tire protrudes significantly out of the wing creating significant drag.

The gear lobe fits behind the wheel, smoothing the airflow and reducing drag. This works great if the gear is rigged correctly and the wheel has a hubcap. Unfortunately, all Comanches prior to 1965 models had dual-fork gear legs and brakes that were on the outboard side and were exposed when retracted. The air reaching the spats on these aircraft is already severely disturbed and thus no gain will be realized unless the air is smoothed prior to the fairing.

Several methods have been approved to fix this issue—including reversing the brakes so they are retracted into the well, and even replacing the main gear legs with the later single-fork gear legs. The short story here is this: get rid of the drag in front of the wheel before you invest in the spats. Of course if the spats are already installed, it is relatively inexpensive to realize significant aerodynamic gains.

Flap track fairings are a bit of a conundrum. They seem to help on some airplanes but not on others. They do straighten the flow but add significant whetted area. The big benefit is they keep foreign objects and dirt from being thrown up into the flap tracks if the aircraft is operated into unimproved environments.

Overall, many of the aircraft in the Comanche fleet have been modified with at least one of these under wing modifications.

Cowling and cooling mods
The other significant source of drag on any airplane (and a particularly draggy portion of the Comanche airframe) is the cowling and its resultant cooling drag.

Twin Comanches had a fairly efficient cowling from the onset, but the singles did not get a more efficient cowl until the C model came out in 1969. Two primary cowling and cooling modifications for singles are the Aviation Performance Products (APP) Eagle cowl and the LoPresti Wow Cowl. Both of these do what they are designed to do.

The LoPresti cowl is only available for the 260, and the APP cowl is available for the 180-260B. Both products specify removal of the original metal cowling in favor of a composite unit, significantly reducing cooling drag through new baffling and cleaner design, and add a full-length nosegear door, further reducing drag.
The major difference in the cowlings—besides looks—is in the execution. The LoPresti cowl is much more involved, adding a cowl flap and an additional actuator for the gear doors. The Eagle cowl uses augmenter ramps to help the cooling and uses a piggyback design (much like the Twin Comanche uses) to close the nosegear doors.

Both of these mods are highly sought after, as they really modernize the look of the airplane and significantly increase overall performance.

For twins, there are new nosebowls available that help speed and cooling to some degree, but the rest of the cowling remains stock.

Product improvements
Product improvement modifications can range from the mundane to the truly cool. Among these are changes to windscreens, wingtips, fuel tanks, lights, props, doors and safety equipment.

Replacement windows are popular mods for Comanches (and other airframes, too). Several options exist for a single-piece windscreen. You can choose to keep the original profile, or you can modify the roof line to extend the pilot viewing port up over your head with an “Arapaho” style windscreen.

There are pros and cons to either style. Any increase in window area increases the visibility, but it also increases the solar heating potential. Replacement for the original glass for all of the windows is available up to one-quarter inch thick, and in various tints including auto-darkening.

Several versions of mods exist to replace the stock round wingtips that look a little dated by today’s standards and probably are a little worse for wear. Most of these use a Hoerner profile and vary based upon the location of the nav and strobe light installations. Others have downturned wingtips, or upturned “finlets.”

All of these do great things for aesthetics and may contribute to overall performance, but on their own, you would probably be hard-pressed to see any performance improvements. That’s why I didn’t include them in the speed mod category.

One very big mod for the wingtips that does provide some measurable performance improvement is tiptanks. These add 15 gallons per side, and are available for singles and twins.

As well as significantly increasing the range of the aircraft, they add to the max gross weight of the aircraft to varying degrees based on model and year. The early 60-gallon capacity PA-24-250s benefit greatest from the tiptanks as they get a 200-pound gross increase and 30 extra gallons of fuel.

Fuel tanks
Over the years many different fuel tank modifications have been installed. There is a baggage compartment tank that was available for any pre-1966 aircraft; the twins have a couple of different nacelle fuel options as well as the Miller wet wing.

All of these add greatly to the utility of the Comanche line.

Moving inboard on the wing, all Comanches come stock with two wing landing lights. Popular upgrades here have been HID lighting as well as LED, and both are huge improvements in lighting over the stock GE 4309 bulbs.

In fact, LED lighting is available from many different manufacturers today. LED beacons and nav lights really enhance the “see and be seen” ability of any aircraft they are installed on.

Wing root fairings
The wing root has always been an issue with the gap between the fuselage and the wing being sealed by a rubber seal. It has a tendency to tuck under or blow out (depending on the location), and one of the best mods to fix this is the wing root fairing.

This mod was first engineered at Piper with the installation of the three-blade prop on the 400. Piper engineers found it decreased the vibration in the cabin as well as the noise, so it should be considered very important to anyone who has installed a three-blade prop.
The wing fillets on the trailing edge do some amazing things to the airflow in the landing configuration and make the Comanche almost land like a 172.

I touched briefly on three-blade propellers; all Comanches except for the 400 came stock from the factory with two-blade props.

Today, every Comanche model has at least one additional STC’d prop option, and most singles have a replacement prop option from every major manufacturer, including Hartzell, McCauley and MT.

Props are available in two-blade, three-blade, straight and scimitar. All are a huge improvement over what was originally installed.

Alternators and electronic ignition
Under the cowl, options exist to replace the old generators with alternators that have additional output up to 70 amps. Options exist to replace the old Prestolite starter with a myriad of lightweight starters.

Dual exhaust is a very worthwhile mod on all of the 180s and 250s, as it does away with a troublesome stock system that was the subject of several ADs. (Comanche 260s had dual exhaust as a stock feature.)

Recently, electronic ignition has become available, too. Because of its high altitude wing, the Comanche benefits more than most from this great leap into the 21st century.

Moving back to the cabin door, there are several mods that have been fitted in this area. Many doors have suffered severe damage after being slammed open in the wind. This gave rise to several door reinforcement schemes, especially in the front lower corner. If you’re inspecting a Comanche, you can look for a triangular reinforcement panel or additional rivets along the door leading edge.
Also recently a gas strut door opener/retainer has become available that is a great improvement over the stock door stop/retainer.

One of the other weak points of the door—especially those with the older two-latch systems—has been solved by installing a Cherokee-style upper door latch.

Electrical system
Electrical system upgrades are another hidden but very important product improvement. All legacy Comanche aircraft should have copper cable throughout to replace the original aluminum cable between the battery and starter and generator/alternator. This was a subject of a Piper Service Bulletin, but should be considered mandatory for all as it eliminates so many issues.

Batteries and battery boxes have come a long way since 1958. New stainless battery boxes are available, as well as non-spillable RG batteries that reduce the battery maintenance to next to nothing. The stock location for the circuit breakers is not ideal on Comanches, and many have been relocated to a visible and accessible location.

In keeping with the ongoing modernizations of the airframes, most have gotten some sort of an instrument panel refit. This can range from a simple overlay, to a complete rebuild of the structure of the panel utilizing one of the STC’d kits or a field approval.

Safety equipment
In the cabin, shoulder harness kits are available and should be considered mandatory minimum safety equipment, in my opinion.

As an additional measure, AmSafe airbag seatbelts are approved and have been installed in many airframes. This serves as a great safety enhancement that everyone hopes they never have to use.

There are two other areas that have gotten significant attention lately, and our Comanche brethren from Australia have provided solutions.

One is a modification that replaces the upper portion of the main gear leg and significantly strengthens it. The main gear trunnion has been known to crack—especially on the heavier weight models (singles and twins). This mod not only provides a source for new parts at a reasonable cost, but also improves the design.

Another issue is what’s known as the “horn AD” (AD 2012-17-06). It affects all of the singles except the 400 and requires the repetitive disassembly and inspection of the tail pitch horn. Again, the Aussies have stepped up with a new design and an AMOC that allows for replacement of the Piper part and a simple external inspection every 100 hours.

As you can see by this list, the aircraft continues to get great support, and both manufacturers and owners alike see the Comanche series as a worthwhile investment.

In the current IFR environment, it is almost an imperative to have a WAAS enabled GPS in the panel. What passed for good IFR equipment just 10 years ago will make it very difficult to go where you want, when you want, today.
Onboard weather (either satellite or ADS-B uplinked) is a nice-to-have option, but know its limitations. A good Stormscope or Strikefinder is still very desirable in thunderstorm season.

Graphic engine monitors, fuel flow, glass, glass, glass… I could go on for days on the virtues of each. Suffice it to say, especially when it comes to a primary flight instrument display, make sure you like what you are looking at and are comfortable with the information presented.

More information is not necessarily better. A cluttered display, no matter how cutting-edge the avionics are, is not an improvement. Look for the important stuff to be clearly presented.

Traffic boxes, auto pilots, HSIs, solid-state dimmers, backlit instruments, in-flight entertainment and lots more can be had for a price.

The upcoming ADS-B mandate is starting to bring some very interesting options to market. Some aircraft have been modified, but the majority are waiting for further options to present themselves.

Too much to list here
While this article points to an almost head-spinning number of potential modifications and improvements for the Comanche series, it is in no way comprehensive—to do that would far exceed the space available for this article. Consider this a good overview of the types of things that have changed the average Comanche.

If you are looking for a new-to-you bird, or you currently have one that might be ready for an upgrade, maybe you now have a little inspiration as to what your next airplane or project might look like.

Remember, when getting involved with legacy airframes, there is usually no singular source for support. While the Comanche series is well supported, much of it comes from third parties. A membership in the International Comanche Society is a great way to enhance your Comanche ownership experience.

Comanches come in models from the 180 to the 400, twin and single and can be equipped with everything from day VFR with one navcom to the very latest in complete glass nav packages.

They can have new paint or old paint and experience varying degrees of love or neglect, but all Piper Comanches, with enough time, money and effort, can be improved. They can be reliable, efficient traveling aircraft, or they can be made to win any award at Oshkosh—and they have!

Zach Grant is a longtime professional pilot and is currently a pilot for a major U.S. airline. He is the owner of a 1958 PA-24-180. Grant is a Technical Resource Advisor for the International Comanche Society (ICS) as well as past president of the organization. He serves on the ICS board of directors. Send questions or
comments to editor [AT] piperflyer [DOT] com.

*Source: http://en.wikipedia.org/wiki/Piper_PA-24_Comanche


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