Development

Figure 29.—Fuel-injector disassembly. U.S. Navy test, 1931. (Smithsonian photo A48323C.)

A major advantage obtained from combining the fuel pump and injection valve is the ability of an engine so equipped to burn a wide variety of fuels. The elimination of the above-mentioned type of high-pressure tubing reduces the possibility of a vapor lock occurring, thereby permitting more volatile fuels to be burned. This increases the range of hydrocarbon fuels the engine can utilize. It could run on any type of hydrocarbon from gasoline to melted butter.[15]

Another reason for combining the fuel pump and injection valve is given by P. E. Biggar inDiesel Engines(published in 1936 by the Macmillan Company of Canada Ltd., Toronto): “In the Dorner pump, for example, the stroke of the plunger is changed by using a lever-type lifter and moving the push-rod along the lever to vary its movement. Unfortunately, in all arrangements of this sort, the plunger comes to a reluctant and weary stop, as the roller of the lifter rounds the nose of the cam. When the movement does finally end, the injection does not necessarily stop, as the compressed fuel in the injection pipe is still left to dribble miserably into the combustionchamber. To minimize this defect, the designer has placed the pump and injector together in a single unit.”

Starting System: On November 1, 1961, C. H. Wiegman, vice president of engineering of the Lycoming Division of Avco Corporation wrote to the Museum in part as follows:

Early in the development it became quite evident that cold starting was a problem. This was finally worked out by Packard through the use of glow plugs and speeding up the injectors during the cranking period. It had beenfelt that during the slow cranking process we were not vaporizing the fuel through the nozzles and that if we could speed up the injection pumps during this period of cranking a better vaporization could be obtained. Our tests showed that we were right, and that the engine could be started quite easily at minus 10° F through the use of glow plugs. The method used for speeding up the injection pumps was accomplished by utilizing a crankshaft cam during the cranking period. The starter would shift the running cam out of position allowing the crankshaft cam to take over. After the engine fired, the starter was disengaged and the running injector pump cam would assume its original position. The starting cam would be run at engine speed during cranking, and the running cam at ⅛ reverse engine speed during engine operation. The shifting was accomplished by a pin-in-slot and spring arrangement to change the indexing of the cams to starting position and return.An Eclipse electric starter with an oversized flywheel was used.... This was powered by a double-sized battery.

An Eclipse electric starter with an oversized flywheel was used.... This was powered by a double-sized battery.

Air Shutters: The first engines had no provision for throttling the intake air. This allowed the engine to run on its own lubricating oil when the throttle was in idle position. As a result the engine idled too fast, thereby causing either excessive taxiing speeds or rapid brake wear. This inability to idle slowly also caused high landing speeds since the propeller did not turn slowly enough to act as an airbrake. Figure 1 shows the first model. Note that the tubular air intakes on top of the cylinders have no valves. Figure 32 shows a later model. Note the butterfly valves in the ∪-shaped air intakes. Here they are shown fully opened. When the throttle was placed in idle position these valves automatically closed and prevented air from flowing past them. Air could then only enter from the back of the intakes. Since less air could flow into the cylinders, the force of their explosions was reduced, which, in turn, lowered the idling revolutions per minute. Figure 28 shows a cylinder from a more advanced model. Note the circular opening between the air intake and the intake/exhaust housing. A barrel type of valve fitted into this opening. One of these valves can be seen just below and to the left of the cylinder. When the throttle was placed in idle position this valve rotated to a position which cut off almost all of the airflow into its cylinder. This increased the vacuum formed toward the end of the intake stroke, thereby causing more resistance, which reduced the idling rpm to that of a gasoline engine.[16]

Crankcase: It was strengthened by having external ribs added. Note the contrast between the first engine, figure 2, and a later model, figure 32.

Oil Cooler: The drum-shaped honeycombed cooler was replaced by a spiral pipe type located between the engine cowl and the crankcase. Figure 3 shows an example of the former type of cooler located at the top of the engine between two of the cylinders. Figure 33 illustrates the latter type located between the cowling and the crankcase.

Cylinder Fastening: Early models had their cylinders strapped and bolted to the crankcase. Later ones had them only strapped. Figure 2 shows a bolt-fastened clamp between two of the cylinders on the first engine. Figure 19 shows a later model without any bolts holding down the cylinders.

Pistons: The pistons used in the 1929 engine had one compression ring and one oil scraper ring above the piston pin, and one oil scraper ringbelow it. There were three grooves, two above the piston pin, and one below it.[17]Pistons used in 1930 had two compression rings, one oil scraper ring above the piston pin, and one oil scraper ring below it. There were four grooves, three above the piston pin, and one below it.[18]The 1931 pistons had one compression ring above the piston pin, and one compression ring and four oil scraper rings below it. There were four grooves, one above the piston pin, and three below it.[19]

Figure 34.—Modified pistons after endurance run. U.S. Navy test, 1931. (Smithsonian photo A48325D.)

Combustion Chamber: In 1931 the contour of the cylinder head was changed slightly. This improved the combustion efficiency to the extent that the stroke of the fuel pumps could be decreased about 15 percent. The specific fuel consumption then decreased about 10 percent. In addition the compression ratio was reduced from 16:1 to 14:1.[20]

These changes were designed to eliminate smoke from the exhaust at cruising speed, and to reduce it at wide-open throttle.

Valves: A two-valve-per-cylinder model was built, but not put into production. It featured more horsepower (300), a higher rate of revolutions per minute (2000), and a better specific fuel consumption (about .35 lb/hp/hr).[21]

Capt. Woolson designed the production model with a single large valve for each cylinder. This was done in order to shorten the development period, for it is easier to design a single valve which serves both the intake and exhaust functions than one valve for each function. Not only are there fewer parts, but more important, there are no heat-dissipating problems. Although the single valve is heated when it releases the exhaust gases, it is immediately cooled by the incoming air of the next cycle. This cooling advantage is not shared by a valve which only passes exhaust gases.[22]

Cylinder Head: Ribs were added to increase its rigidity (compare fig. 32 with fig. 33).

Engine Size: A 400-hp model was developed in 1930. It was not put into production.[23]

Comments of Aeronautical Engineers: These comments appeared inAviationfor February 15, 1930, just a month before the Packard diesel received its approved-type certificate. They were in answer to the question, “What is your opinion of the probable early future of the compression ignition type of engine in aircraft powerplants?” Most of the engineers were enthusiastic about the diesel engine’s future in aviation; however, neither George J. Mead nor C. Fayette Taylor shared their colleagues’ opinions. Mead’s prophesy was accurate except for his discounting the diesel’s role in lighter-than-air craft. Taylor was correct in implying that there was a future for the diesel in powering airships.

George J. Mead (vice president and technical director, Pratt & Whitney Aircraft Company):

Compared with the present Otto cycle engine, the Diesel powerplant weight, including fuel for a long-distance flight, would apparently be less. It is doubtful whether there would be any saving if the orthodox engine were operated on a more suitable fuel. Inherently the Diesel engine must stand higher pressures and therefore is heavier per horsepower. A partial solution of this difficulty is the two-cycle operation, which seems almost a requirement if the Diesel cycle is to be considered at all for aircraft. For any normal commercial operation in the United States there seems to be little or no improvement to be had from the Diesel. After all, it is not entirely a question of fuel cost but payloads carried for a given horsepower. It seemed at one time as though the Diesel was particularly desirable for Zeppelin work. Now that blau gas has been introduced, which obviates the need of valving precious lifting gas, the Diesel cycle seems much less interesting for this purpose. There may be a reduction in fire hazard and radio interference with the Diesel cycle, but it is doubtful whether it will be used in view of these considerations alone.

C. Fayette Taylor (professor of aeronautical engineering, Massachusetts Institute of Technology): “I believe that the compression ignition engine will continue to remain in the experimental stage during the year 1930. I should expect its first really practical installation to be in lighter-than-air craft.”

P. B. Taylor (acting chief engineer, Wright Aeronautical Corporation): “I believe the compression ignition engine is probably the type which will eventually supersede the present electric ignition units. This development will come slowly and will not be a solid injection engine.”

Henry M. Mullinnix (former chief of powerplant section, Navy Bureau of Aeronautics):

The advantages of compression-ignition, including reduced fire hazard, more efficient cycle, elimination of electrical apparatus and hence of radio interference, elimination of carburetion problems, and other benefits less evident, would seem to outweigh the difficulties encountered in metering and injecting minute quantities of fuel at the proper instant. Although the Diesel engine suffers upon comparison with the Otto cycle engine in flexibility there seems to be a definite field for employment of Diesels and a gradual extension of their use may be predicted.

John H. Geisse (chief engineer, Comet Engine Corporation): “I am firmly convinced that the Diesel engine in the future will not only maintain the advantages of Diesel engines as they are now known, but will also be lighter in pounds per horsepower than the present Otto engines.”

Lt. Cdr. C. G. McCord (U.S. Navy, Naval Aircraft Factory): “The use of compression ignition in due time appears to be assured; but increase in weights above those of present Otto cycle engines, to insure reliability, must be expected.”

L. M. Woolson (aeronautical engineer, Packard Motor Car Company): “There is no question that the compression ignition aircraft engine will in time offer severe competition to the gasoline engine. There are, however, many basic problems to be solved for the solution of which there exists no precedent.”

N. N. Tilley (chief engineer, Kinner Airplane and Motor Corp.):

Considerable development of the compression ignition type of engine for aircraft will be required before it is commonly available. It is believed that the weight per horsepower must be equal to, or less than, that of the present type of engines, in order to interest the public, since rapid take-off, rate of climb, and speed are desired, rather than low fuel consumption or high mileage. Most flights are of few hours duration. It is believed that flights must be of over five or six hours duration in order to show any advantage of Diesel engines (with low fuel consumption) if appreciably heavier than present engines. Also the difference between Otto cycle and Diesel becomes slight as the compression ratios come closer together.

Comments of Flight Crews: The preceding comments were made by engineers thinking primarily of the commercial possibilities of the diesel. Following are comments by flight crewmembers about the operatingcharacteristics of the Packard diesel. The former were largely optimistic. Most of them were only familiar with the aeronautical diesel as a design project and therefore did not have the practical experience necessary to understand all of its limitations. The latter were pessimistic, as they knew firsthand various shortcomings of the engine which only became apparent when it was operated.

Clarence D. Chamberlin, pioneer pilot:

My only experience with the Packard diesel was in a Lockheed “Vega” which I owned back about 1932. The Wright J-5 had been replaced with the 225 hp Packard Diesel. My main complaint was the excessive fumes. When I would come home at night my wife would greet me with, “You have been flying that oil burner again.” It was so bad that passengers’ clothing would smell like a smoky oil stove for hours after a flight.Looking backward, it is my guess that the Diesel would have had only a limited period of acceptance even if all mistakes had been avoided. It is easier and cheaper to get performance with lighter and more powerful engines and longer runways than by refining the airplane. Fuel economy of an engine has ceased to be the deciding factor. Higher utilization of a high speed Jet at least in part offsets the inefficient use of fuel. The only time the Diesel had a chance was from the middle 20’s perhaps on thru WW-2 for certain things due to gasoline shortage. To sum it up, the thing that licked them worst was the use of a single valve for inlet and exhaust making it impossible to collect and keep the fumes out of the fuselage.[24]

Looking backward, it is my guess that the Diesel would have had only a limited period of acceptance even if all mistakes had been avoided. It is easier and cheaper to get performance with lighter and more powerful engines and longer runways than by refining the airplane. Fuel economy of an engine has ceased to be the deciding factor. Higher utilization of a high speed Jet at least in part offsets the inefficient use of fuel. The only time the Diesel had a chance was from the middle 20’s perhaps on thru WW-2 for certain things due to gasoline shortage. To sum it up, the thing that licked them worst was the use of a single valve for inlet and exhaust making it impossible to collect and keep the fumes out of the fuselage.[24]

Ruth Nichols, prominent aviatrix:

I was flying Chamberlin’s diesel-powered Lockheed, in which a month before I had made an official altitude record for both men and women in aircraft powered by an engine of that type. The record, I believe, still holds. It was a rugged, dependable plane whose experimental oil-burning engine nevertheless had a number of bugs. For one thing, it was constantly blowing out glow-plugs used for warming the fuel mixture, and when that happened long white plumes of smoke would stream out, giving spectators the impression that the ship was on fire. For another, the vibration was so bad that out of 10 standard instruments on the plane, 7 were broken from the jarring before my return. The diesel fuel also produced a strong odor in the cockpit, the fumes so permeating my luggage and clothes that my public appearances during the tour always were highly and not very agreeably aromatic. Having a strong stomach, I soon became accustomed to the fumes, but another pilot who ferried the plane between cities for me on one occasion ... was almost overcome. On arrival he said, “I wouldn’t fly that oil burner another mile.”[25]

Figure 35.—Ford 11-AT-1 Trimotor, 1930, with 3 Packard 225-hp DR-980 diesel engines, right side view of right engine nacelle. (Smithsonian photo A48311.)

Richard Totten,[26]airplane mechanic:

The Ford Trimotor was the poorest of the lot. It was inherently noisy and slow, and with the Packards installed it was on the point of being underpowered. It was almost impossible to synchronize the three engines, and the beat was almost unbearable. It was not flown much but it made a fine conversation piece standing on the airport apron....The Waco taperwing developed the unnerving habit of breaking flying and landing wires from the vibration, and most of the time sat on the hangar floor with its wings drooping like a sick pigeon. In flight the open cockpit filled with exhaust smoke and unburned fuel and the pilot would land after an hour’s flight looking like an Indianapolis 500 Mile Race driver....The Stinson “Detroiter,” the Bellanca “Pacemaker” and the Buhl-Verville “Airsedan” were the most successful ships and were the most used. The “Airsedan,” in which Woolson was killed, was his favorite ship, and the one I believe that was the most flown.

The Waco taperwing developed the unnerving habit of breaking flying and landing wires from the vibration, and most of the time sat on the hangar floor with its wings drooping like a sick pigeon. In flight the open cockpit filled with exhaust smoke and unburned fuel and the pilot would land after an hour’s flight looking like an Indianapolis 500 Mile Race driver....

The Stinson “Detroiter,” the Bellanca “Pacemaker” and the Buhl-Verville “Airsedan” were the most successful ships and were the most used. The “Airsedan,” in which Woolson was killed, was his favorite ship, and the one I believe that was the most flown.

The Towle TA-3 amphibian flew beautifully, but not for long. It never got a chance to do much as it was a victim of the depression. The Towle was powered by 2 Packard diesels on loan from the Packard Motor Car Company. It was built of corrugated aluminum exactly like the Ford Trimotor. As a matter of fact, Towle had been employed by Ford until Ford cancelled airplane building. Towle got his airplane built at the hangar on Grosse Isle in Detroit, and ran out of money during the flight testing program. He now looked for money to continue with and found a backer in the person of one Doctor Adams, a widely advertised “Painless Dentist” of Detroit. Adams wanted a quicker return on his money than the average backer and he insisted that Towle put the airplane in service so it could start earning some money. At this time the amphibian was beginning to become popular for intercity flying, especially around the Great Lakes region as all of the major cities were located on the waterfront. What was more natural than an airline flying passengers right into the downtown area of a city? Thompson was doing it between Detroit and Cleveland, Marquette was doing it between Detroit and Milwaukee, so Adams applied for permission to operate an airplane between Detroit and Cleveland and other cities on the lakes. In those days it was necessary to prove an airplane’s reliability by flying a certain number of trips over the proposed route with a simulated payload. This payload was supposed to consist of sand bags, but usually consisted of any mechanic or pilot who happened to be loose at the moment, and who had nerve enough to go along. Mechanics were easier to load and unload than sand bags.

The Towle was in the middle of the qualification flights, and the publicity began to appear about the new airline. Much newsprint was devoted to the fact that the Towle was powered by the new Packard diesel engine, and this, of course, made it the only safe airline since all its competitors were using the old-fashioned dangerous gasoline. On the last payload trip of the Towle the pilot asked me if I wanted to go along, and of course I was delighted. I neglected to mention that I had been hired by the Adams airline as a mechanic because of my experience in repairing the corrugated skin of the Ford Trimotor owned by my employer, the Knowles Flying Service. The mere fact that I did many repairs to the airframe did not preclude me from getting my share of the engine work too, and since I was already familiar with the Packard diesel, I was quickly hired by Dr. Adams.

The last flight was indeed the last flight. We took off from the Detroit City Airport and when we crossed the Detroit river the pilot decided to land at the Solvay Coal Company docks and fuel up for the opening of the airline the next day. The Solvay Coal Company was the only place in Detroit where diesel fuel was obtainable at the time and all of the diesel powered yachts got fuel there. The pilot was not too experienced in the operation of amphibians, and he put the wheels down as we approached the river. When we hit the water the airplane went over on its back and sunk to the bottom. Itcame up to the surface again, and we all climbed out onto the keel, and waited for rescue. A police boat came over and took us to the dock. The police sent us to the hospital and then went back and towed the airplane over to the shipyard next door to Solvay. While we were at the hospital, the crane man hooked onto the Towle and lifted it out of the water and gently set it down on the dock. He was only trying to help, but he inadvertently set it down on its back instead of its wheels. That was the end of the Adams airline. The Packard Company took back their engines. I helped remove them the next day. We dismantled the airplane and trucked it back to the airport where it sat in a state of neglect for some time. The pilot was fired, I lost my job, and Towle lost his airplane.

A Packard diesel advertisement which appeared inAero Digestfor June 1930 stated that this engine had three major advantages over its gasoline rivals: Greater reliability because of extreme simplicity of design; greater economy because of lower fuel cost plus lower fuel consumption, permitting greater payloads with longer range of flight; and greater safety because of removal of the fire hazard through the use of fire-safe fuel and absence of electrical ignition equipment.

These were the engine’s principal advantages. Others are analyzed here by the author in order of their importance. At low altitudes the diesel uses an excess of air to eliminate a smoking exhaust; consequently at high altitudes, where the air is less dense, the diesel is still able to maintain much of its power. In contrast, the carburetored gasoline engine is sensitive to the fuel-air ratio and thus has no surplus air available at higher altitudes. A malfunctioning carburetor could cause a gasoline engine to cease operating, but an inoperative fuel injector would cause the Packard diesel to lose one ninth of its power, since each cylinder had its own independently operating injector. In practice, however, because of the excessive vibration, the engine was generally shut off immediately after a cylinder cut out.[27]Shielding was unnecessary because the diesel had no electrical ignition system. Carburetor icing was an impossibility because there was no carburetor.

Any excess lubricating oil in a diesel engine’s cylinder is consumed cleanly to produce power. By contrast, such oil in a gasoline engine’s cylinder is only partly burned. As a result carbon deposits form that eventually cause malfunctioning of the spark plugs, valves, and combustion chambers. This advantage accrued to the diesel because it utilized an excess of air, and in addition its cylinder walls were hotter. The engine was very clean-running from the standpoint of oil leakage. This was a safety factor since it eliminated the possibility of a fire starting on the outside surfaces of the engine, and in addition it saved the time and money that was normally spent cleaning engines.[28]Since the diesel utilized its heat of combustion more efficiently than the gasoline engine, its cooling fin area could be reduced by 35 percent. This permitted better streamlining. Having less cooling fin area, it warmed up more rapidly than a gasoline engine.

Figure 36.—Advertisement emphasizing the advantages of fire-safe fuel. (Smithsonian photo A48848.)

Due to the greater simplicity, it was more practical to build a large diesel than a large gasoline engine. Large airplanes would therefore need fewer engines if diesel powered. Smaller fuel tanks could be used because of the greater fuel economy of the diesel, and also because of the high specific gravity of fuel oil as compared to gasoline. Furthermore, these smaller tanks could be placed in more convenient locations. Not having a carburetor the engine could not backfire, further reducing the fire hazard. The exhaust note was lower because of the diesel’s higher expansion ratio. The absence of an ignition system permitted the diesel to operate in the heaviest types of precipitation. Such conditions might cause the ignition system of a gasoline engine to malfunction. The Packard diesel was flown at times without exhaust stacks or manifolds; this was practical from a safety standpoint because of the diesel’s lower exhaust temperature due to its higher expansion ratio. Elimination of these parts reduced the weight and cost of the engine installation. Finally, the engine was ideal for aerobatics, since the injectors, unlike carburetors, would work equally well whether right side up or upside down.

An advantage peculiar to the Packard among aeronautical diesels was its light weight. The English Beardmore “Tornado III” weighed 6.9 lb/hp, and the German Junkers SL-1 (FO-4) weighed 3.1 lb/hp, while the Packard weighed but 2.3 lb/hp. In fairness to the Beardmore, it was the only one of the three engines designed for airship use, and part of its heaviness was due to the special requirements of lighter-than-air craft. A contemporary and comparable American gasoline engine, the Lycoming R-680, weighed 2.2 lb/hp. To have designed a diesel aircraft engine as light as a gasoline one was a remarkable achievement.

There are four main reasons why the Packard diesel was not successful. First the Packard Motor Car Company put the engine into production a brief three years after it was created. The only successful airplane diesel, the German Junkers “Jumo,” was in development more than three timesas long (1912-1929). The following tests indicate that the Packard diesel was not ready for production, and hence was unreliable.

Packard Motor Car Company 50-Hour Test (Feb. 15-18, 1930): This test was identical to the standard Army 50-hour test which was used for the granting of the Approved Type Certificate. The engine tested was numbered 100, and was the first to be made with production tools (approximately half a dozen engines had been handmade previously). It had to be stopped three times, twice due to failure of the fuel pump plunger springs and once due to the loosening of the oil connection ring. These failures were attributed to manufacturing discrepancies. In addition, 4 out of a total of 103 valve springs broke.[29]

U.S. Navy 50-Hour Test (Jan. 22, 1931, to March 15, 1931): The engine used in the Navy test was numbered 120. (Apparently only 20 production engines had been built during the preceding 12 months; Dorner in a letter of March 3, 1962, states that the total number of Packard diesels produced was approximately 25.) The engine had to be stopped three times, twice due to valve-spring collar failures and once due to a valve head breaking. Because of these failures this test was not completed. The following significant quotations have been extracted from the test: “The engine is not recommended for service use.... Flight tests, until the durability of the engine is improved, be limited to a determination of the critical engine speeds, and to short hops in seaplanes.... It is believed that this size engine should be made suitable for service use before this type in a larger class is attempted.” This latter statement probably refers to the 400-hp model.

A year had passed between the making of engine 100 and 120, yet the reliability had not improved. Although unreliability was the immediate cause of failure, there were two design defects which would have doomed the engine even if it had been reliable. All the Packard diesels were of the 4-stroke cycle unblown type, yet the most successful airplane diesels were of the 2-stroke cycle blown type.[30]The advantages of the latter type for aeronautical use are thatitis of a more compact engine, of lowerweight and greater efficiency.[31]The engine was therefore built around the wrong cycle.

The Packard diesel of 1928 was designed to compete with the Wright J-5 “Whirlwind” which powered Lindbergh’s “Spirit of St. Louis” in 1927.[32]The specifications were within two percent of each other. The diesel engine’s fuel consumption was far less although its price was considerably higher.

The advantages of lower fuel cost and greater cruising range offered by the diesel engine would be relatively unimportant to a private pilot flying for pleasure, but would be vital to the commercial operator using airplanes powered by engines having several times the horsepower of the Packard diesel. Its size, moreover, was too small for the technology of fuel injectors.[33]The Packard Company realized that the production engine was too small.[34]In 1930 a 400-hp version was built but was not put into production, probably because of the unreliability of the 225-hp model.

The fourth principal reason why the engine failed is explained by the following quotation fromThe Propulsion of Aircraft, by M. J. B. Davy (published in 1936 by His Majesty’s Stationery Office, London):

Although the development and adoption for transport purposes of the relatively high-speed compression ignition engine has been rapid during the last few years, there has been no corresponding advance in its adoption for aircraft propulsion. A reason for this is the recent great advance in “take-off” power in the petrol (gasoline) engine due to the introduction of 87 octane fuel (which permits higher compression ratios) and the strong probability of 100 octane fuels in the near future, still further increasing this power. The need for increased take-off power results from the higher wing loading necessitated by the modern demand for commercial aircraft with higher cruising speeds with reasonable power expenditure.

Production of the Packard diesel ceased in 1933. During that same year the Pratt & Whitney Aircraft Company and the Wright Aeronautical Corporation specified 87-octane fuel for certain of their engines. Less than 10 years later octane ratings had increased to over 100, putting the diesel at a further disadvantage.[35]

Although the above disadvantages sealed the Packard diesel’s fate, there were other minor reasons for its failure. The Packard diesel had the highest maximum cylinder pressure (up to 1500 psi at peak rpm) of any proven contemporary aircraft diesel engine. Leigh M. Griffith, vice president and general manager, Emsco Aero Engine Company, had this to say about the Packard diesel’s high maximum cylinder pressure in the September 1930S.A.E. Journal:

The designers considered it necessary to adopt unusual but admittedly clever expedients to counteract the great torque irregularity caused by the excessive maximum pressure. The adoption of the lower pressure of 800 lbs. would have eliminated the necessity for the pivoted spring-mounted counterweights and the shock-absorbing rubber propeller-drive.... The use of such high pressures is in reality the quick and easy way to secure high-speed operation and can be justified only from this standpoint, although the resulting increased difficulty in keeping the engine light enough was a strong offsetting factor.[36]Insofar as the engine life was concerned it is true that 1,500-psi peak pressures were observed but the engine was so developed to withstand these pressures.... One of the most severe problems connected with the development of this engine was the piston ring sealing. Special compression rings were made with no gaps and further work in this respect could have been used to advantage had the engine been kept in production.[37]

Insofar as the engine life was concerned it is true that 1,500-psi peak pressures were observed but the engine was so developed to withstand these pressures.... One of the most severe problems connected with the development of this engine was the piston ring sealing. Special compression rings were made with no gaps and further work in this respect could have been used to advantage had the engine been kept in production.[37]

It is significant that in 1930 the Packard diesel had a compression ratio of 16:1, whereas in 1931 it has been reduced to 14:1. This was probably done to reduce vibration and the problem of piston-ring sealing.[38]The exhaust products had an unpleasant odor which was particularly objectionable during taxiing. Professor C. Fayette Taylor, writing in the January 1931 issue ofAviation, remarked about this fault: “One is inclined to question whether the disagreeable escaping of exhaust gas from the intake ports can be overcome, while still retaining the obvious advantages in weight and simplicity of the single valve.” The engine exhaust deposited a black oily film. In fact some airplanes fitted with the Packard diesel engine were painted black, so that soot deposits from the exhaust would not be noticed.[39]Since the passengers’ and pilots’ compartments were generally located behind the engines, and were not airtight, damage to clothing resulted. This fault could have been eliminated by the use of separate valves for the intake and exhaust systems.

It was not possible to start the engine when the temperature dropped much below 32° F unless glow plugs were used. These spark-plug-like devices, which were only used for starting, had resistance windings which glowed continuously when turned on. The additional heat glow plugs provided made starting an easy matter in the coldest weather; however, they complicated the design of an engine noted for its simplicity, and they used so much electricity that only a long flight would allow the generator to fully recharge the battery.

H. R. Ricardo, writing in the June 4, 1930, issue ofThe Aeroplanesaid: “Referring to the very fine achievement of the Packard Company of America in producing a small radial air-cooled heavy-oil engine, a petrol engine of similar design and with the same margin of safety would weigh less than 1½ lbs. per hp.” The important point made is that a gasoline engine designed along the same lines as the Packard diesel would weigh considerably less, but would then suffer from the Packard’s reduced structural safety factor. It is significant that as the Packard developed, it became heavier.[40]

Like other diesels, the Packard cost more to build than a comparable gasoline engine, because of the type of construction required for the diesel’s higher maximum cylinder pressures and the difficulty of machining the fuel injectors. Having fuel injectors, the engine was more sensitive todirt in the fuel system than a carburetor-equipped gasoline engine.[41]The fuel injectors were “a crude and deficient mechanism” subject to rapid wear, and often these injectors caused smoking exhausts and high fuel consumptions.[42]In the event of battery or starter failure, a comparable gasoline engine could be started by swinging the propeller. Because of the engine’s high compression, it would have been impossible to have hand-started a Packard diesel this way.

In a letter to the Air Museum, January 15, 1962, Dorner commented: “During my first demonstration (of high-speed diesel engines) in 1926 in California and later in Detroit I learned from Capt. Woolson that the large transport airlines were controlled by oil companies which were not interested in (supplying) two different kinds of aircraft fuel, and in savings of fuel.” The May issue ofAero Digesthad a full-page illustrated advertisement titled “Announcing National Distribution for Texaco Aerodiesel Fuel.” Although distribution was limited, the American oil industry did not prevent the airplane diesel from becoming a success in the civil market. However, it is significant that the advertisement was placed by Frank Hawks of the Texas Company largely as a gesture of friendship to Woolson.[43]

The situation in the military market was different, however, as testified by this quotation from the same letter. “The military administration, having paid all of the expenses for the testing period to that date (1931), came after the tests to the conclusion that the advantages of the diesel as compared to its disadvantages did not justify the great risk to procure and distribute two different kinds of fuel in case of war.”

Two accidents, which received wide publicity and no doubt did considerable harm to the entire project, occurred to Packard diesel-powered airplanes. The following quotation is from theHerald Tribunefor April 23, 1930: “Attica, New York—Losing their bearings in a blinding snowstorm and mistaking the side of a snow-covered hill for a suitable landing place, three men, one of them Capt. Lionel M. Woolson, aeronautical engineer for the Packard Motor Company and adapter of the diesel engine to airplanes, were killed here today.”

Figure 37.—Interior of Bellanca, showing Parker D. Cramer, pilot (left), and Oliver L. Paquette, radio operator, just before taking off from Detroit, Michigan, on July 28, 1931. (Smithsonian photo A202.)

The second of these accidents is described in the September 1931 issue ofU.S. Air Services:

Columbus wanted to sail west beyond the limits set by the learned navigators of his time, and in much the same consuming fashion Parker D. Cramer wanted to show his generation and posterity that a subarctic air route to Europe via Canada, Greenland, Iceland, Norway, and Denmark was feasible.... On July 27, without any preliminary announcement, Cramer left Detroit in a Diesel-engined Bellanca, and following the course he took with Bert Hassel three years ago, he flew first to Cochrane, on Hudson Bay. His next stop was Great Whales and then Wakeham Bay. From there he flew to Pangnirtum, Baffin Land, and across the Hudson Straits to Holsteinborg, Greenland. He crossed the icecap at a point farther north than the routes that have been discussed heretofore, but almost on the most direct or Great Circle route from Detroit to Copenhagen. He was accompanied by Oliver Paquette, radio operator. They were on their way more than a week before they were discovered. To Iceland, to the Faroe Islands, to the Shetlands.They were taxiing across the little harbor of Lerwick, Shetland Islands, when a messenger from the bank waved a yellow paper. It was a warning of gales on the coast east to Copenhagen. Cramer apparently thought it was an enthusiastic bon voyage, and, after circling the town, flew away. A Swedish radio station reported a faint “Hello, Hello, Hello” in English, but the plane was not seen again.

They were taxiing across the little harbor of Lerwick, Shetland Islands, when a messenger from the bank waved a yellow paper. It was a warning of gales on the coast east to Copenhagen. Cramer apparently thought it was an enthusiastic bon voyage, and, after circling the town, flew away. A Swedish radio station reported a faint “Hello, Hello, Hello” in English, but the plane was not seen again.

As the result of a personal conversation with his brother, William A. Cramer, in 1964, the author learned that the fuselage and floats of the airplane were found six weeks later. Since there was no indication of a heavy impact (not a single glass dial on the instrument panel was broken), a successful landing must have been made. Several weeks later, a package was found wrapped in a torn oilskin containing instruments, maps, and a personal letter, all substantiating the evidence that the landing was successful. It can only be surmised that there was engine failure, probably due to a clogged oil filter.[44]

Once before during the trip a forced landing had been made due to engine malfunctioning, and a successful takeoff was accomplished in spite of a moderately rough sea. This time, however, storm conditions probably made the takeoff impossible.

As a final summary of the author’s analysis of the Packard diesel engine, it must be emphasized that although the engine burned a much cheaper and safer fuel more efficiently than any of its gasoline rivals, it was too unreliable to compete with them. Even if it had been reliable, it was too small to be useful to the large transport operators, to whom its fuel economy would have appealed. In addition, this mechanism operated on the wrong cycle: 4-stroke, rather than the lighter, more compact, and more efficient blown 2-stroke cycle. Lastly, it was doomed by the advent of high octane gasolines, first used while it was still in the development stage. These new fuels reduced the diesel’s advantage resulting from low fuel consumption, and, in addition, gave the gasoline engine a definite advantage from the standpoint of performance. The Packard diesel was a daring design but, for the reasons analyzed in this chapter, it could not meet this competition, and therefore failed to survive.

this agreementmade this 18th day of August 1927, by and betweenhermann dorner, of Hanover, Germany, hereinafter referred to as “Licensor”, andpackard motor car company, a Corporation of the State of Michigan, United States of America, of Detroit, Michigan, hereinafter referred to as “Licensee”;

witnesseth, that

whereas, Licensor owns certain Letters Patent of the United States and other countries relating to oil burning engines under which he desires to license the Licensee;

whereas, Licensee desires rights under said Letters Patent;

now, therefore, for the mutual considerations hereinafter set forth, the parties have agreed as follows:

1. Licensor warrants that he is the inventor of an oil burning engine, is the sole owner of United States patent Number 1,628,657, dated May 17, 1927, and United States patent applications, Serial Numbers 46,383 filed July 27, 1925, and 88,409 and 88,411, filed February 15, 1926, relating to such engines and is joint or sole owner of patents or patent rights relating to said engines in England, Germany and Sweden.

2. Licensor agrees to furnish the Licensee at cost price but not exceeding Thirty Dollars ($30.00) cash, as many pump and nozzle units as are needed for use in building one or more experimental engines.

3. Licensor hereby gives and grants unto Licensee an exclusive license for the manufacture, within the United States and its dependencies, and a non-exclusive license for the use and sale, of engines for aircraft, and a non-exclusive license for the manufacture, use, and sale of engines for motor vehicles and motor boats, under said United States patent Number 1,628,657, under all after-acquired patents and under all patents that may result from said patent applications, and from all other patent applications pertaining to his present oil burning engine or reasonable variations thereof, such licenses to extend for the full life and term of all such patents, provided however, that there is specially excepted from this grant—stationary engines, tractor engines, and engines for agricultural purposes.

4. Licensor further hereby permits said Licensee to export to all other countries and sell and use there, without further royalty, all engines made by Licensee in the United States under this license.

5. Licensor acknowledges receipt of One Thousand Dollars ($1,000.00) inpayment of a portion of the expenses heretofore incurred by him and as one of the considerations for this agreement.

6. Licensor agrees to devote all time necessary from this date to November 1, 1928 to supervision of the design of an engine and construction thereof at the plant of the Licensee and will in his absence furnish the services of a competent assistant, the expenses of Licensor and assistant to be paid for by Licensee at the rate of One Thousand Dollars ($1,000.00) per month for the first three (3) months, and Five Hundred Dollars ($500.00) per month thereafter until the decision in paragraph eight has been made by Licensee.

7. Licensee agrees to build and test at least one experimental aircraft engine with special Dorner features, and to take all reasonable measures to reach the stage of final test. All Dorner feature engines made by Licensee will be marked “Licensed Under Dorner Patents.”

8. Within one year after the completion of tests of the aircraft engine built by Licensee hereunder, or in any event not later than November 1, 1928, Licensee will decide whether it will proceed with the manufacture of engines hereunder, or not. If Licensee decides in the affirmative then it will pay Licensor forthwith the sum of Five Thousand Dollars ($5,000.00) as advance on royalties and as minimum royalty for the first production year. If Licensee decides in the negative for reasons which are under the influence of Licensor, then Licensee will give Licensor notice and sufficient time to try to correct possible imperfections, and the time for final decision will be correspondingly extended. If the reasons for the negative decision are under the influence of Licensee, then Licensee will grant to Licensor an oral conference at Detroit and explain the reasons in detail. In event a negative decision is finally rendered by Licensee this agreement may be terminated at any time thereafter upon sixty (60) days’ notice in writing to Licensee and both parties released from all further obligations hereunder.

9. Licensee agrees that if after three (3) years from the date hereof Licensee is not manufacturing and does not contemplate the manufacture of, a certain size and type of aircraft engine which Licensor would like to grant another manufacturer the right to build and which would not reasonably compete with anything manufactured by Licensee, Licensee will release such size and type aircraft engine from the exclusiveness of this license and thereby permit Licensor to grant a license to such other manufacturer to make, use and sell such engine and such engine only.

10. Licensee agrees to pay royalty on all engines manufactured and sold or used under this agreement, based on effective brake horsepower under normal load, as follows:

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