March 2014- Alaska is called The Last Frontier for good reason. The state has over 500,000 acres of uninhabited land (about 94 percent of its total acreage). It’s home to about 30,000 brown bears (grizzlies included), as many as 100,000 black bears and a far smaller number of (estimates say under 5,000) polar bears. Caribou and the largest subspecies of moose (Alces alces gigas) roam across the state. And it’s mountainous. Seventeen of the tallest peaks in the United States are located there.

Then there’s the weather: strong, variable winds and ice. The changeability of the weather makes it particularly dangerous. Notes Peter Grier of The Christian Science Monitor, “Snow, ice, rain, wind—lots of locales in the U.S. experience bad weather. But in Alaska, it can hit you in an instant, due to the meteorological effect of its high mountains, deep gorges and permanent glaciers. Fog often does not creep in on little cat feet in Alaska. It can slam in like a locomotive.”

These are reasons that many owners in the state modify their Pipers for backcountry bush flying. It’s an everyday occurrence to find Cubs outfitted with bush wheels and other modifications, but Cary Foster and his “Monster Cub” are something extraordinary.


Super Cub to Monster Cub transformation

Cary Foster is a bear-hunting guide, and traveling to remote locations over uninhabited land is all in a day’s work for him. It should come as no surprise then that his PA-18 Super Cub is tricked out from nose to tail.

When Foster bought the 1956 Super Cub it was painted an ugly brown, with brownish spots created by years of paint touch-ups. “We called it the brown trout,” Foster remembers.

This past winter, the Brown Trout received a total body makeover when an Airframes Alaska Wide-Body Fuselage was installed. This STC adds four inches to the width of the fuselage, creating 20 percent more internal room that Foster says is a real benefit for Alaska flying.

The Wide-Body comes standard with a reinforced tail, removable crossbar, pilot X brace, extended baggage compartment, floor seatbelt tabs, third-seat X brace and a bigger panel to accommodate modern avionics. These features resolve AD issues and incorporate other common PA-18 modifications.

Foster has this to say about it: “We operate these airplanes year-round and when wintertime comes, our loads increase in size and amount. Our survival gear bags increase in size; we pack our wing covers, engine covers—and usually are wearing bunny boots and parkas.

“I use the Monster Cub for guiding hunters in Alaska and in the standard Cub fuselage I would run out of room for gear and hunter. I can put more stuff inside closer to the CG of the aircraft. With the wide-body, I can pack all of the camp gear and the hunter and still be within the envelope.”

Foster also decided to install a 180 hp O-360 rebuilt by Custom Aircraft Engines in Palmer, Alaska. “Richard Walker and his crew did a top-notch rebuild—and as you can see from the pictures, they put in a lot of time painting the engine and installing a few STCs to the engine that made a huge difference in its performance,” Foster says.

“When I go out for guiding hunters or taking my family out to the Alaskan wilderness, I want an engine that will bring me back home.”

The plane was also fitted with the ThrustLine engine mount extension which modifies the PA-18 thrust line from four degrees downward to zero.

Foster has good things to say about this upgrade, too. “The ThrustLine mod is another great mod for the PA-18. The stock PA-18 has about a four-degree downward angle on the engine from the fuselage,” Foster says. “After installing the kit and flying the airplane I gained four mph!

“In our other testing in stock Cubs it also showed a 30 percent reduction in takeoff roll. This is a short-field, dump-the-flaps, get-off-the-ground takeoff with one person and full fuel,” he explains.

“Everyone wants to take off short,” Foster continues, “but this is not why this mod was developed. It was developed for landing. The pilots who have flown this mod generally don’t even talk about the takeoff performance as the landings are so impressive.”

“I can tell you that we found out that it has never been the weight up front that that spoils the landings on a Cub; it has always been that negative thrust line,” he explains.

“With the new setup, the trim characteristics are much improved. The stock Cub with full flaps could not be trimmed hands-off until about 40 mph indicated. As the airspeed increased above 40, nose-down stick pressure needed to be increased,” he says.

“On the modified Cub I was able to trim at full flaps up to 60 mph—hands-off. The plane used to just run out of nose-down trim in the landing configuration; not with the modified ThrustLine.

“Then we trimmed the aircraft for level flight at a 3,000-foot pressure altitude. At 66 and 70 mph—clean—it took 100 to 150 rpm less in the modified aircraft to perform the maneuver. Other tests in cruise have shown a four to 10 percent increase in cruise speed,” Foster reports.

“Mark [Englerth] with ThrustLine has been flying and working with Super Cubs for a very long time in Alaska and really hit the mark with this STC.”

Another performance modification is the tuned exhaust from Leading Edge Exhaust Systems in Anchorage. Foster reports that “after installing this exhaust system on the Cub, I noticed a definite horsepower increase. After doing [a] pull test with the aircraft I increased my horsepower by 22 hp.”

“After the installation of the new exhaust I noticed 10- to 15-degree lower temperatures, and they stabilized much faster after a steep climbout—which I use in a lot of short ponds and strips throughout Alaska,” Foster tells us.



Cockpit mods

In addition to his guide business, Foster has been developing infrared STCs for the past eight years. He has developed and holds multiple STCs for over 300 different airframes including the entire Cessna fleet, Beechcraft King Air fleet and several different helicopter airframes.

His Super Cub is equipped with a Max-Viz infrared unit that helps him see through that aforementioned fog lest it catch him unawares.

He says it’s just “a great safety device” that helps him to see rocks, trees and even animals. Should you be caught in a situation with minimal visibility and need to scope a landing site or avoid terrain, it can be a lifesaver. Foster thinks it’s a valuable investment for search and rescue missions, emergency crew as well as for bush flying.

After searching for a small MFD that would also display the infrared and work in General Aviation installations, he settled on the AvMap EKP V aeronautical navigator. “It did everything I wanted. Plus, it’s affordable and lightweight!”

The EKP V was designed to be used as either a portable unit or as a cockpit-installed instrument. It has a fully-sunlight-viewable seven-inch display, with built-in battery and GPS—and is only 0.8 in. thick.

AvMap’s add-on Cockpit Docking Station allows the installation of EKP V into the panel and enables the unit to become the hub of an integrated avionic system. When docked, the EKP V is powered and charged by the aircraft electrical system, and it can connect to several onboard devices at the same time, such as A2 ADAHRS; third-party autopilots; XM Weather; Zaon PCAS XRX; a video camera and, in Foster’s Cub, to the infrared system.

The docking station includes four USB ports, two serial ports, audio/video input and audio output. One of the ports is powered by the EKP V internal battery to ensure functionality even in case of aircraft electrical power failure.


Additional mods

Other modifications Foster has made to the Cub include 35-inch Alaska Baby Bushwheel tires from Alaskan Bushwheel, a three-inch extended landing gear from Airframe Alaska, and the new F. Atlee Dodge composite skis, which are straight skis and weigh in at 35 pounds each. Airforms’ baffling provides a tight seal for better engine efficiency.

Foster has also tested an experimental prop from Catto Propellers of California. Weighing in at just 15 pounds, this prop is a big plus for a Cub that does some heavy hauling.

Foster replaced the generator with a Plane-Power alternator. He says, “It was a fast and easy install. I have installed many alternators in the years that I have been maintaining aircraft and it was probably the easiest install ever.”

One improvement he is really glad he made is the addition of the B.A.S. shoulder harnesses. B.A.S. doesn’t have an STC for the PA-18 so the installation was done under a field approval, but the extra work was well worth it.

Before its transformation from Brown Trout to Monster Cub, two of Foster’s closest friends were flying the aircraft and experienced a catastrophic prop failure that sent them and the Cub hurtling to the water shortly after takeoff. Examination of the propeller after the accident revealed a bullet hole in one blade that had been illegally filled in and painted over. The hole caused the stressed blade to crack in half.

The Cub experienced some damage—spars and fours ribs to be replaced—but was repairable. And more importantly, Foster’s two friendswalked (actually, swam) away from the crash. “Those shoulder harnesses saved my friends’ lives,” he says.

Foster feels that an engine monitor is a must-have piece of equipment for keeping an eye on his engine’s health. He has an Electronics International UBG-16 installed and has been very happy with it.

There’s a saying that goes, “if you want to get something done, ask a busy man”—and they must have had Cary Foster in mind when they said it. In addition to all his other projects, Foster has been working on the Approved Model List (AML) for the Whelen LED Nav/Strobe STC and is close to having certification for over 100 airframes; including of course, the PA-18.

These super-bright LED lights are highly visible, thereby providing an extra margin of safety. The LEDs also provide a significant reduction in current draw over conventional position lightbulbs.

Cary Foster has spent years researching, testing and developing STCs for his Cub and other planes. His Monster Cub is a monument to his meticulous approach and his determination to make General Aviation flying—in Alaska and elsewhere—a lot more safe.

Jennifer Dellenbusch is president of the Piper Flyer Association. Send questions or comments to editor [AT] piperflyer [DOT] com.




engine baffles



extended landing gear

Airframes Alaska


wide-body fuselage

Airframes Alaska


rebuilt O-360 engine

BJ Custom Aircraft Engines

(907) 745-6030


tuned exhaust

Leading Edge Exhaust Systems, LLC



Plane-Power Ltd.


engine mount extension

ThrustLine Products of Alaska LLC



infrared unit

Astronics Max-Viz


EKP V aeronautical navigator



field-approved shoulder harnesses

B.A.S., Inc.


UBG-16 bar graph engine monitor

Electronics International Inc.



35-inch Baby Bushwheel tires

Alaskan Bushwheel


lightweight propeller

Catto Propellers


LED Nav/Strobe STC

Whelen Engineering Co., Inc.


composite straight skis

F. Atlee Dodge Aircraft Services LLC


For a link to videos of Cary Foster’s Monster Cub and his STC work, see