When you think of working airplanes, a bush operation probably comes first to mind. But in the lower 48, working airplanes are more likely to be ag aircraft and tugs, in that order. Fortunately, ag airplanes can do double duty as applicators and tugs.
But for banner towing and glider operations, there are a surprising number of choices. Whether setting up or continuing an existing towing operation, a reliable towplane with plenty of power tops the list of must-have equipment, especially if the operation is expected to turn a profit.
A good towplane should have a comfortable cockpit for those long hours spent towing, it should be easy to maintain with spare parts readily at hand and, above all, it should have a reliable towline-release mechanism thats easy to reach in an emergency, not something cobbled up from scrap shop parts. The variety of available tugs covers a wide range of aircraft; you can make your head spin just winnowing down the choices. For instance, theres Pipers Pawnee and Super Cub, the Boeing/Stearman PT-17, WACOs UPF-7, Cessnas 150 (with the 150 HP engine), 180, 182, 185, 188 and the L-19 Bird Dog, Aviats Husky, American Champions Citabria Explorer and Scout, Maules M-5 and Grumman/American AgaVtions Ag-Cat. All can and have done tug duty.
Thats obviously too many to cover in a single article so well concentrate on five of the aforementioned models, aircraft that are relatively easy to obtain at competitive prices. These are the Piper Pawnee, Super Cub, Citabria Explorer, Cessna 180 and the Grumman/ American Ag-Cat.
Pawnee
The tube-and-rag Pawnee was one of the first light single-seaters specifically designed for agricultural spraying and dusting. It first flew in 1957 and entered service in 1959. A Lycoming O-540-B2B5 235 HP engine provides the power and upgrades have included oleo struts on the C model and a 260 HP engine for the D model. From 1971 to 1982, the PA-36 Pawnee Brave became available; its a similar configuration but its larger overall.
At some point, the idea to turn the Pawnee into a towplane was born and one of the most reliable glider tugs in the world came into being. With its 235 HP engine and gentle flying characteristics, the airplane makes towing gliders-especially the two-place fiberglass ships-quite easy.
It has a spacious cockpit with plenty of leg and headroom, but the view over the nose when taxiing-for shorter pilots, in particular-can be limited. An additional seat cushion can alleviate this problem as well as provide some cushioning for your bottom when operating from grass fields.
The Pawnees towline-release lever is on the cockpit floors left side near the seat, and its close to the flap handle in both appearance and proximity. Some operators rig a rope to the handle or tie a bungee just aft of the throttle quadrant; this arrangement allows them to grab the tow-release mechanism instead of inadvertently lowering the flaps.
New Pawnees are still being manufactured in Argentina but a quick search on the Web (330 pages available on Pawnees) revealed several used models for sale. Prices range from $33,000 for a 1970 C-model airframe to $42,000 for a 1975 Pawnee 260D with 2818 hours. A few Braves were found with a ballpark price of $28,500.
As plenty of Pawnees are still flying, spare parts are plentiful, too. Several ADs on the Pawnee models include corrosion in the wings lift struts and forward spars and problems with the fuselage tubing cluster and the elevator control system. For more information on AD 95-12-01 that affects the main wing-spar attach points and their costly and repetitive requirements, go to: www.harrishillsoaring.org. This is a reprint on the subject from Soaring Magazine by Stephen Garner.
Operators seem to agree that the Pawnee is easy and fairly inexpensive to maintain, but as with all rag airplanes, it should be hangared when not in use. One glider club is looking at a $15,000 recovering bill for its Pawnee-kept outside during the season-and its A&P recommended a total airframe refurbishment before recovering. This will cost $30,000-almost the price of a used Pawnee.
Pawnee Performance
With 235 horses spinning a fixed-pitch prop at 2750 RPM max, the Pawnee is a powerhouse. On a standard day at an airport elevation of 500 feet with full fuel (40 gallons), a 195-pound pilot and sans glider, the Pawnee can reach pattern altitude just as it passes the halfway point of the takeoff runway.
The type and weight of the towed glider, elevation and the days conditions will affect the Pawnees climb out-800 to 1000 FPM with a heavy, two-place Grob and 1500 FPM or better with a single-place Schweizer 1-26.
An airspeed of 80 to 85 MPH is usually indicated for the heavier ships and 65 to 70 MPH for the lighter ships. The lower speeds place the Pawnee at a fairly high angle of attack during the climb out, thus making it difficult to see below.
The Pawnees controls are fairly light, with the elevator input being the most sensitive. Its elevator trim is effective and is usually in the full-up position for a glider tow. This helps to alleviate most of the constant pull on the stick during the climb out. With lots of power and a glider yawing you around, your feet get a good workout. This usually translates to sore knees by the end of the day-especially the right one. Without the glider attached, rudder forces are normal.
When towing, a Pawnee will conservatively burn 14 GPH, which gives you a safe flying time of 2 1/2 hours. A placard warns pilots who weigh 220 pounds or more to land with at least 10 gallons of fuel for weight and balance purposes.
Plan to approach the runway at 80 MPH for a wheel landing and at about 75 MPH for a three-pointer. During the wheel landing, because the Pawnees nose slopes down, it looks as though youre going to fly the airplane right into the ground. Amazingly, theres still ground clearance for the propeller and the aircraft literally flies itself onto the runway.
When flaring for the three-point attempt, try not to touch the tailwheel first, and watch the airspeed, as the Pawnee will drop in like a ton of bricks, if you let it.
Piper Super Cub
Developed in 1948, the PA-18 Super Cub is basically a more powerful, beefed-up J-3 with flaps. Through the years, a variety of Continental and Lycoming engines ranging from 90 to 180 HP have powered it, with the 150 HP to the upgraded 160 HP version being the most popular for towing.
As one of the main aviation workhorses, the Super Cub is used in a variety of roles. As a towplane, its well suited to drag the single-place gliders aloft, but on hot days with short runways, its best to avoid pulling a two-place ship with two pilots aboard. The GIBs (guys in back) become unnerved when climbing out close to the treetops-if in fact, your runway has them at the end. On a cold day, this isnt a problem.
For a tall pilot, the tandem cockpit is cramped, but the seat can be moved rearward to accommodate long legs. Steel tube rudder pedals and heel brakes are standard, and there isnt much room for the big shoes of a pilot with large feet.
When the full-flap position is used, the flap handle-near the left cockpit wall-is perpendicular to the cockpit floor. During a left, front-quartering crosswind, this can create a problem because the pilots leg cant move far enough to the left to allow adequate stick input to counteract drift. The long-legged pilot will find himself raising his leg a bit to allow more aileron control to be added. Apart from this, the cockpit is comfortable and your knees wont be nearly as sore as when towing in the Pawnee.
The towline-release mechanism is on the cockpit under the pilots left leg. Its a short piece of tube with a ball handle at the end. If you have to drop the rope when landing, it can be tricky to reach for this because you have to take your eyes away from the forward view to find it. Once found, a firm pull easily drops the line.
With thousands of Super Cubs around, finding spare parts-or someone who can work on the airplane-isnt a problem. For more info, contact Cub Crafters, Inc. http://cubcrafters.com/cc/; they rebuild Super Cubs to like-new specifications, as well as custom build brand-new, fully certified 180 HP models. They also have parts available.
Some of the ADs out on the Super Cub include: wing lift-struts or forks, control-cable replacement, failure of engine mount and rudder-cable attachment lug.
For a complete listing of Super Cub ADs, go to AD site mentioned above for the Pawnee. Another good website on the Super Cub is by Steve Johnson. The address is www.supercub.org.
There are PA-18s for sale and a quick search turned up some mid- to high-five-figure prices with a variety of total times. A random sampling: PA-18 with 150 HP for $67,000; a completely rebuilt 150 HP Super Cub by Cub Crafters, Inc. for $79,900.
The base price for a new one from Cub Crafters is $135,975. As an aside, if youre looking for a super cheap tug, the Super Cub probably wont be it.
Cub Handling
The Super Cub is a dream to fly, but with a glider attached, it feels as if youre pulling a house into the air. Airspeed-especially if towing a heavier, single-place glider-is critical. The airplane usually indicates 60 to 65 MPH for the heavy ships and 50 MPH for the lighter gliders. Depending on the conditions and glider weight, climb outs can range from 500 to 1,000+ FPM.
During a tow, the controls are responsive; full up-trim on the climb out can eliminate the force required for stick pull. Visibility during the climb out is quite good and theres a skylight for that Whats above me? view. With two 18-gallon tanks and a conservative fuel-burn estimate of 9 GPH, a safe flying time of 3 1/2 hours is practical.
An approach of 70 MPH for a wheel landing and 60 MPH for a three-pointer will gently groove the Super Cub into a grass strip. With a strong wind, forget the flaps and use the wind to your advantage.
A rollout of about 300 feet (885 feet over a 50-foot obstacle) is quite doable for a quick turn glider pick-up, something glider pilots like if conditions are good and the field is busy.
Champions Citabria
Essentially, the Citabria and its variants are Bellancas advanced developments of the Aeronca Champion series airframes that were so popular after World War II. Originally built as trainers and limited aerobatic aircraft, they have served in a variety of roles, one of which is towing. Today, theyre made by American Champion Aircraft (ACA), of Rochester, Wisconsin, www.amerchampionaircraft.com. American Champion has owned the type certificate to the Champs for more than 12 years and has supplied parts from the beginning.
With a 150-HP Lycoming (160 HP in the newer versions) and a slightly longer wing, the Citabria Explorer Model 7GCBC seems to be the version best-suited to towing.
It has the same weight-towing restrictions as the Super Cub, but its cockpit, which is a little bigger in both length and width, is more comfortable for the taller pilot. The flap handle is in the same area as the Super Cubs, but when the flaps are fully extended, the handle doesnt get in the way, as does the Super Cubs.
Prices for the tube-and-rag Explorer range from around $30,000 for a used one to $78,900 for a factory-new model. A major-and expensive-to-fix-AD exists for all model 7 and two Model 8s that have wooden wing spars. Read it at the following Web address www.bellanca-championclub.com.
There seems to be quite a battle brewing over this AD and it would be wise to thoroughly check it out before you purchase a Citabria as a tow plane. If you have to do the spar fix, its expensive. Other ADs include corrosion of fuselage longerons and rudder and elevator cables, engine-power loss, adjustable front seat and fuel shutoff-valve bracket.
Citabria Handling
Because the Citabria line has a higher gross weight than the older Aeroncas, they have a heavier feel in the air and you wont have the relatively light control forces that youll experience in the Super Cub. They are, however, more stable than the older Champs, they handle the wind better and they dont have the pronounced adverse yaw that was inherent in the older airplanes.
Therefore, its easier to keep the Explorers ball centered, especially when dragging a glider or a banner.
And with the 150-HP engine hanging on the nose, you wont feel like the Little Engine That Could.
Taxiing the Explorer doesnt require S-turns, as the nose is at a lower angle than that of most taildraggers.
Visibility from the cockpit is very good and the skylight over you allows you to see whats above.
As usual, the tail must be brought up during the takeoff roll and once up on the mains, the spring gear reminds us of those from a Cessna 170 or 180. Be prepared to waddle a little on the takeoff roll before you leave the ground.
With a 37-gallon fuel capacity in two wing tanks and a fuel burn roughly the same as the Super Cubs, youll have about 3 1/2 hours of safe towing time before you need to visit the fuel truck. Be aware that these tanks dont have separate feeds and have been known to drain unevenly.
The tow speeds are only slightly higher than the Super Cubs and, again, the type of glider or the size of the banner must be taken into consideration. This is not the airplane for a busy gliderport towing heavy two-place ships all day.
With the spring gear, performing a wheel landing requires a finesse. It seems best to fly the Explorer to the runway and plant it on with a slight hint of power and some forward stick. A power-off three-pointer can be greased on with a flare just before the touchdown and then full back stick once contact is made-nailing the correct touchdown speed helps.
Cessnas 180 Skywagon
Cessnas 180 Skywagon prototype was first flown in January 1952 and it was introduced to the public a year later. It uses the same wing as the 170, which includes the slotted Fowler-type flap and basically the same fuselage.
The two main differences are the squared-off tail surfaces and the installation of a 225-HP Continental O-470-A engine-later models had 230-HP engines. A constant-speed, all-metal propeller is standard equipment.
Although it was designed for the business market, the 180 quickly became a popular bush aircraft because it had a longer range, could carry a larger payload and had a higher cruise speed than others in its class. A variety of minor design changes eventually led to its becoming a six-seat aircraft that evolved into the 185 with a 300-HP Continental.
Besides its bush and military applications, the C-180 has been used as a tow plane. With its reliable engine, it has plenty of power to haul up heavy gliders and moderate-size banners. Its cockpit is comfortable with plenty of legroom for tall pilots and the flaps operate via a handle between the seats, so there isnt a possibility of pulling the wrong lever for the towline release.
Even though it has a yoke, pilots find it easy to fly and many seem to enjoy the side-by-side front-seat arrangement, as opposed to the tandem configurations. Unlike the Pawnee, the seat can slide back far enough and its adjustable, saving the pilot much wear and tear on the knees during those long hours of towing.
More than 6000 C-180s were built and there are still plenty of them around both to purchase and obtain spare parts from. Typically, 180s weve seen listed from $40,000 for a 1955 model to $105,000 for a 180K II model from 1978.
ADs for the various 180 models can be found on the previously mentioned website, pages 41 and 42. Some of these included: defective spar-attach fittings; fuel-tank venting; seat tracks and engine-controls installation. One other great attribute of the C-180 is that its an all-metal airplane, so it can remain outside for the towing season and not be as drastically affected by the elements as a tube-and-rag airframe would be.
Cessna 180 Performance
Like the Pawnee, the 230 HP C-180 is also a powerhouse. In standard conditions and at a low airport elevation, the 180, sans glider or banner, will become skybound quickly. The view over the nose when taxiing is somewhat limited for shorter pilots, but raising the seat and adding a cushion helps. The rudder pedals easily accommodate pilots with big feet, with toe brakes being the normal setup for stopping the aircrafts roll.
Expect climb speeds and rates to be close to the Pawnees. The cockpits view both outward and below is exceptional, but theres no skylight, so care must be taken to avoid whats above, a consideration for tow pilots navigating around gliders.
The Skywagons controls are well balanced, with fairly light forces required. The elevator input seems to be the most sensitive, especially in the flare and theres plenty of rudder authority to overcome any yaw problems. Also, as in the Pawnee, the 180s elevator trim is effective in relieving backpressure during a tow climb out. The C-180 has two wing tanks that each hold 30 gallons; with an estimated fuel burn of 12 GPH, a safe towing time of 4 1/2 hours can be expected.
The Skywagons spring gear makes landing interesting. Wheel landings are best accomplished by flying the airplane right to the runway, all while controlling the descent with the power. At the correct touchdown speed, let the mains contact the runway and apply a little forward pressure.
If the speed is off, or you allow it to drop in, the bouncing episode that follows will keep you busy.
For a three-pointer, the attitude should be set up with the flare and the descent rate controlled with power. If you drop it in, the resulting porpoise effect will remind you to practice landings where your friends cant see them.
Ag-Cat
First flown in 1957, the Grumman Ag-Cat was designed to fill a specific agricultural-work need. In April 1958, the biplane (top and bottom rag wings are interchangeable) was introduced to the public with a 220-HP radial engine and has had various engine upgrades that include Pratt & Whitneys R-985 (450 HP) and R-1340 (600 HP). It has a metal fuselage and a constant-speed, metal propeller.
Its cockpit compares in size with the Stearmans, so theres plenty of room for a tall pilot. The comfort level is high because with its 60-gallon top-wing tank and an estimated 30 GPH fuel-burn, youll be towing banners for only about 1 1/2 hours before landing for gas.
The Ag-Cat flies too slowly to tow heavy gliders efficiently, but its perfect for banner work. With an average banner length of 100 feet, you can cruise at about 50 MPH. The towline-release mechanism is on the cockpit floors left side and, if necessary, it can be activated by your left foot.
From its beginning, Ag-Cat production was subcontracted to Schweizer Aircraft and it was eventually sold to Frank Kelly at American AgAviation, P.O. Box 482, Walnut Ridge, Arkansas, 72476; 870-886-2418; www.ag-aviation-online.com. With the name Grumman attached to it, you know it has to be reliable and safe; not one AD could be found. There are plenty of Ag-Cats and parts available for maintenance. Some examples of prices are $49,900 for a 1975 Super A 600 with a 4200 hours; $40,000 for a 1970 G164A 600 with 5200 hours total time and $33,000 for a 1974 G164A with 5065TT. This website had a variety of Ag-Cats for sale: www.skytractor.com.
Ag-Cat Performance
Despite its beefy looks, the Ag-Cat is not difficult to fly. To help alleviate the rudder forces required to keep it straight, the Ag-Cat has a trim tab on the rudder that can be bent. Once the takeoff roll has commenced, the biplane leaves the ground rather quickly, but the forward speed is a bit slow, as is the climb out speed.
Landing an Ag-Cat is similar to landing a Pawnee. The approach speed is about 70 MPH and on touchdown, the airplane will roll about 100 feet and come to a stop. With four ailerons and that large rudder, theres plenty of control authority to handle a crosswind but like any taildragger, attention to rudder is a must.
Which One?
To a large degree, picking a tug may have to do less with having the perfect airplane than selecting a model thats widely available, serviceable and affordable. That may rule against some of the more exotic choices, such as a Stearman, an L-19 Bird Dog and perhaps even the Ag-Cat, with its gas-thirsty radial engine. The venerable Bird Dog is a superb tug but finding parts can be a chore, something that can be ruinous in a commercial operation or even a busy weekend club.
The two best airplanes for glider towing, in our view, are the Pawnee and the Super Cub. Both are readily available and easy to maintain. If you opt for the Super Cub, the 180-HP engine is a must. The Cessna 180 isnt a bad choice; it certainly has the power to tow but keeping the oil temperature within safe limits on a hot summer day takes effort.
Banners are a different game and here, slow is good. Ag-Cat pilots like the slow moving biplane for towing banners-especially the large ones. The Stearman is a favorite for this work, too, for the same reason.
The Citabria actually seems to be better suited for banner towing than glider towing, so long as the banners are kept small. Otherwise, spring for the Cat or Stearman and suffer the gas bill.
Also With This Article
Click here to view “Checklist.”
Click here to view “Select Model Histories.”
Click here to view “Towing: An Endurance Test.”
Click here to view a photo grouping.
-by Roger Post
Roger Post is an instrument-rated commercial pilot and has been towing gliders for seven years.
