February 2016 Mystery Airplane – the Towle TA-3
The first correct response received for the April 2016 Mystery Plane was submitted by Wayne Muxlow. He identified the amphibian as the Towle TA-3 which was built during 1930 in Detroit, Michigan by the Towle Aircraft Comany under Group 2 approval #2.291. The 8-place TA-3 was powered with two 225 hp Packard DR-980 diesel engines.
Others who sent correct answers were Arthur Schwedler, Ulrich Rist, Pit Ross, Jim Grant, Thomas Lymburn, Robert Bailey, Dan Shumaker, Bruce Hinds, Dave Austin and Brian Baker. A number of respondents identified the amphibian as a Douglas Dolphin and admittedly the TA-3 does appear somewhat similar to the Douglas design.
Thomas Towle in 1928 founded the Towle Marine Aircraft Engineering Company, (later changed to Towle Aircraft Company), in Detroit, Michigan. He had previously been involved in the design of the Eastman E-2 Sea Rover and was at one time an engineer employed by the former Stout Metal Airplane Division of the Ford Motor Company.
Towle designed three aircraft, the first being the Towle WC (TA-1) completed in 1928. It was a 4-place amphibian with a wingspan of 52 ft. and powered with two Comet 150 hp R-612 engines. The WC was custom built for a planned round the world flight that in 1929 got as far as Brazil where the attempt was terminated because of repeated engine problems.
His second design was the 5-place Towle TA-2 completed and test flown in late fall 1929. The fuselage of the TA-2 featured corrugated aluminum, similar to the Ford Tri-Motors that Towle had previously worked on. Two Wright R-540 engines of 165 hp were mounted on pylons above the 47 ft. 9 in. wing of the aircraft. Unfortunately the aircraft crashed and sank on its initial test flight which took place on Lake St. Clair. Parts of the TA-2 were salvaged, some reportedly surfacing in England in 1930. The wing which was a scaled down version of a Ford Tri-Motor wing, however, remained in the United States, in fact it became part of Towle’s next amphibian, the TA-3.
The 8-place Towle TA-3 was built at Grosse Ile Municipal an airport situated near Detroit. First flight was made in May 1930 by test pilot George Pond. (See article that follows which appeared in the February 1931 issue of AERO DIGEST for more information about the design and construction of the Towle TA-3).
The TA-3 had an interesting life. Robert F. Pauley wrote about some of them in his excellent book, “Images of Aviation MICHIGAN AIRCRAFT MANUFACTURERS”. He states the aircraft was at one time leased to Kohler Airlines, apparently anticipating a possible sales transaction. Kohler Airlines had started service on September 1, 1929 flying two flights daily from Milwaukee’s lakefront Maitland field across Lake Michigan to Grand Rapids, Michigan. Eventually the route was expanded to Detroit with four round trip flights daily. Kohler used single engine Leoning C-2C “Air Yacht” amphibians powered with 425 hp Wright Cyclones. They carried 6 to 7 passengers in a heated cabin plus the pilot, and co-pilot who flew in an open cockpit, a rather uncomfortable ride during winter months.
Kohler was offered the use of a TA-3 to evaluate this aircraft for their over the lake operations and apparently the aircraft performed satisfactorily until one day in May 1932 when a Kohler pilot forgot to retract the wheels when attempting a water landing. As is inevitable the amphibian flipped over and sank, fortunately in shallow water.
In July of that year the aircraft was retrieved and repaired, then sold to a flying service in West Palm Beach Florida. Prohibition was the law of the land at the time but the TA-3 was utilized to haul bootleg liquor from the Bahamas to Florida. Unfortunately the aircraft was destroyed later when a severe tropical storm battered Bimini Island and put an end to the Towle amphibian era.
Towle was employed by several aircraft companies until the start of World War II when he became chief engineer of the Hudson Car Company’s aircraft division.
He retired in 1967 and died in Miami in 1983.
TOWLE ALL—METAL AMPHIBIAN FLYING BOAT
The Towle Model TA-3 amphibion is powered by the Diesel engines of 225 horse power each as standard equipment, but it is adaptable to either Wasp Juniors or J-6 Wright 300’s. The first ship was flown on May 9, 1930, and since that time it has undergone the process of development based on hundreds of flights from rough water and bad landing fields. As a result of these tests, the company believes that all service “bugs” have been corrected and that the ship is now ready to be put in the hands of the commercial operator.
The ship was designed by Tom Towle, and all parts (except instruments, wheels and engines) are manufactured by the Towle Aircraft Company, Inc., of Detroit. The design of this model is based on two preceding models of 1928 and 1929: the Model WC, a twin-Comet-engined design, and the TA-2 with two J-6 Wright 165-horsepower engines.
The Packard Diesel powerplants have proved themselves ideal for this ship, giving quick take-off, elimination of fire hazard, 80 per cent decrease in fuel cost, absence of radio interference and cleanliness of operation. The ease of obtaining fuel for these powerplants became apparent last summer during tours through Ohio, Michigan, Indiana, Illinois and Wisconsin, where ordinary furnace oil was found to be readily obtainable.
The all-metal wing has no conventional spars, ribs or bays. The internal structure is of corrugated Alclad zigzagging fore-and-aft through the wing section and extending from one wing tip to the other. The corrugated sheet is flattened and bent at the points where it is sandwiched between the stringers.
The whole unit, the outer skin, the stringers, and the sheet forming the trussing are riveted together in one operation. The outer skin is of corrugated Alclad and is so connected as to take a portion of the wing torsion.
The wing is resistant to torsion since it is virtually made up of nine triangular tubes, each in itself resistant to torsion. Furthermore, it may be considered that these nine tubes are made even more resistant to torsion by being enveloped in another metal tube or skin which has the cross-section area equal to the sum of these nine internal tubes. All of these triangular tubes are so well tied together that the problem of torsion is eliminated, as proved by the torsional wing test to destruction made upon a complete wing, by the Airplane Structures Section of the Army Air Corps at Wright Field.
Wing stress analyses do not require provision for any center of pressure movement on the Towle wing. The design was based upon the worst condition asked for; namely, high incidence load factors. Low incidence, inverted flight and diving are taken care of. The actual method of calculating wing stresses consisted in obtaining the moment of inertia of wing sections at several stations, about their neutral axes and injecting them into the bending moment stress formulas.
The airfoil section is that developed originally by Tom Towle in 1925. It is tapered in both plan form and thickness and has a lift-drift ratio of 16:2 and a high maximum lift coefficient of .00375, Army units. With the limited horsepower the top speed and landing speed are obtained by lesser wing area and a high lift coefficient, rather than the usual low drag and low lift wing section with its accompanying greater wing area. The maximum lift has the happy faculty of “hanging on” at high angles of attack. This effect is attributable to the washin of the wing tips. In this way the burble point of the center section, which contains the greatest percentage of wing area, is considerably delayed.
Particular attention is given to the prevention of salt water corrosion in the wing. All surfaces, both inside and out, are coated with a zinc chromate and aluminum pigment. All laps where it is possible for water and moisture to collect are coated with an asphalt paint. As a further precaution, the wing, hull and tail surfaces are provided with openings to force ventilation to all parts, a necessary feature often overlooked in combating corrosion.
In working up the hull lines, particular attention was given to seaworthiness. The high bow and concave V bottom permit it to be handled on rough water in an easy manner. The concave V bottom reduces pounding.
The hull and all parts of the ship are made of Alclad. All seams in the hull are of the lapped type. The lapped sheets have between them tape soaked in marine glue, and are riveted together with heat treated duralumin rivets spaced fiveeights of an inch between the double rows and one-half-inch pitch between the rivets. The keel lap is treble riveted. With this method of riveting, local denting will not open up such a seam, a highly important item if such a condition involves the loss of a ship. Denting of this nature may happen quickly and without warning, sometimes under conditions that are far from ideal. The hull is divided into five water-tight compartments. Two steps are provided on the hull bottom. The second step far aft prevents porpoising on the water and shields, the amphibion tail skid directly behind and adjacent thereto. Rubber discs are provided in the tail skid shock absorber. All internal parts are sprayed with a coating of bitumastic paint before assembly. The outside surface of the hull and pontoons are finished with aluminum pigmented lacquer. The cabin interior is finished in a cream color tone.
Control surfaces include ailerons, three rudders, three fins, one stabilizer and one large elevator. These are all covered with corrugated Alclad. The fin and stabilizer are braced by streamline struts. The main center fin supports all of the tail surfaces and is built into the hull. All movable surfaces are hinged on self-aligning ball bearings packed in oil soaked felt retainers. The retractable landing gear has been simplified to operate in 20 seconds up or down. The operation is accomplished entirely by steel cables over ball bearing pulleys. The wheels are located 15 degrees ahead of the center of gravity. The wheel tread is 13 feet. The axle V is hinged to the hull by machined steel fittings directly above the sponson clamp. The vertical struts telescope and are positively locked by 3/4-inch heat-treated square steel pins which are visible to the pilot at all times. Bendix wheels with new water-resisting brakes are used in combination with 36-by-8 inch tires.
The Packard Diesel engines are mounted as tractors, outboard and above the leading edge of the wing. In this position safety is increased, since the engines are not directly above or behind passengers. Objects such as cowlings carelessly placed cannot fall off and foul the propellers. Persons walking about the ship cannot walk into the propellers. The fact that the total horsepower is divided between two propellers offers greater propeller disc area per horsepower, giving unusual take-off. The engine mounts are supported on streamline chrome-molybdenum steel tube members which are sufficiently numerous to distribute the weight of the powerplant over the entire wing instead of concentrating it at only a few fittings.
Fuel and oil tanks are mounted directly behind the engines; these are not interconnected, since it is the aim to have each unit operate entirely independent of the other. The lubricating oil tanks are cylindrical in shape and have a capacity of seven gallons each. The fuel-oil tanks are also cylindrical and have a capacity of 45 gallons each. The latter are not cowled because their shape is such as to streamline the nacelles. Engine mountings are easily detachable by the removal of six bolts at the wing. The gravity fuel system consists of a three-foot Tightflex hose connecting the aluminum fuel tank to the Packard Diesel fuel ring. Since the Packard Diesel has no carburetors or magnetos, a valve is inserted in the fuel lines for emergency stopping of the engines. No fire prevention apparatus is provided since the ship is inherently fire-proof and carries no highly inflammable liquids. The Hamilton Standard propellers are nine feet in diameter and are adjusted to a pitch of 15.5 degrees. The Eclipse starters provided by the Packard Diesels are of the electric inertia type.
Engine controls are located in the center of the dash in the pilots’ compartment, and can be operated individually or together with one hand. An Eclipse electric generator is installed on one engine to provide current for the six-volt Exide storage battery. Cabin, dash and navigation lighting are also operated from the single battery. Exhaust manifolds are made of aluminum sheet welded, since exhaust temperatures do not run high enough to endanger this material. The cabin is comparatively quiet by virtue of its insulation from the engines by the thick wing. The pilot and co-pilot are seated forward and in a roomy compartment which has excellent visibility. The pilots’ seats are of the bucket type, upholstered with leather. They are provided with safety belts, and the co-pilot’s seat can be folded out of the way when so desired. Entrance is made from land by means of a walkway along the afterdeck of the hull to a stairway hatch immediately aft of the wing. On the water, entrance can also be made and moorings caught by passage through the pilots’ compartment and out onto the forward deck, through doors above the pilots’ compartment. Engines can be kept running while catching moorings, since there is no risk of coming in contact with the propellers.
Arrangement is made in the cabin to seat six passengers. The chairs are fixed to the floor and are provided with safety belts. They are made of steel tubing and are upholstered in cream colored Spanish leather. The ceiling has six dome lights. Cabin ventilation is secured by individual scoops placed at each seat. The fixed windows are of Duplate shatter-proof glass. At the rear of and adjacent to the cabin is the lavatory. The baggage compartment is located in the bow. Surface controls are all operated by means of 5/32-inch flexible steel cable, except for the stabilizer adjustment which is actuated through a duralumin crank handle and torque tube. The dual control is of the throw-over type.
Instruments include turn-and-bank indicator, altimeter, rate-of-climb indicator, compass, oil temperature, and air speed indicator, electric tachometers and hydrostatic fuel gauges on the dash.
Span……………………….… 56 feet
Chord at root………….…. 102 inches
Length overall…………… 42 feet
Height overall……………. 14 feet
Tread of wheels……….…. 13 feet
Weight empty…………..….3,943 pounds
Gross weight………………. 6,200 pounds
Total wing area……….….. 406 square feet
Wing loading……………… 15.28 pounds per square foot
Power loading…………..… 13.20 pounds per h.p.
Wing load factor:……….… 5 :45
Absolute ceiling…………… 17,000 feet S
ervice ceiling……………..… 15,000 feet
High speed…………………. 120 miles per hour
Cruising speed…………..… 100 miles per hour
Fuel consumption………….18 galllons per hour
Oil consumption……..……. 1 1/2 gallons per hour
Water take-off………………. 17 seconds
Land take-off…………….…. 12 seconds
Rate of climb………………… 800 feet per minute
Calculated stalling speed…63 miles per hour