FIRST IN FLIGHT
1,100-mile trip that used $8.50 of furnace oil. Packard advertised fuel consumption of 0.40 lbs/hp-hr (about 8.8 gph) for a cruising speed of about 90-100 mph. At full power the DR-980 used 0.46 lbs/hp-hr (about 14.8 gph). Packard stated the Wright J5 gasser delivered 0.60 lbs/hp-hr for (about 15 gph) at cruising.
Packard management was encouraged enough to invest $650,000 in a new aero engine plant, projecting 500 engines a month in production by the end of 1929. Well, the plant got built and tooled up, but it wasn’t cranking out 500 engines per month by the end of 1929. In mid-february 1930 Packard ran a standard 50-hour certification test on engine #100, the first production engine. It passed, and by March 6, 1930, the Department of Commerce issued an approved type certificate, the first ever issued for a diesel aero engine. Packard could begin to sell engines and announced this on April 5 at the Detroit Air Show.
The early production engines differed from the six hand-built prototype engines. The block was improved by adding ribbing and the cylinder head featured butterfly “chokes,” the intakes of each cylinder that activated to slow the engine when the throttle was brought to idle. After 10-15 engines were built that way late in 1930 a barrel valve appeared that restricted the valve port in a more elegant way. The barrel valve also signaled a drop in compression ratio from 16:1 to 14:1 and structural improvements to the head. This ratio drop was part of an effort to reduce vibration and so was a rubber-dampened propeller hub, but neither improvement completely solved the problem.
On May 28, 1931, a DR-980 powered Bellanca Pacemaker set the world’s non-refueling record for fixed-wing aircraft, 84 hours and 33 minutes. Walter Lees, one of the pilots, said they had at least four more hours of fuel in the tank but landed due to approaching stormy weather. For this milestone Packard would win the Collier Trophy, America’s highest aviation award, and the record would stand until 1986 and Dick Rutan’s record nine-day flight.
Packard installed DR-980S into five of its own aircraft: the original Stinson Detroiter, a Waco Taperwing biplane, Buhl Air Sedan, Bellanca Pacemaker and Bird Model F. Several aircraft companies tested Packard diesels. The biggest aircraft to use them was the 184-foot airship Defender, a Goodyear Model PA blimp on which a pair of DR-980S was tested from November 1931 to June 1932. Ford briefly offered them as an option on its Trimotor in 1930. The experimental Towle TA-3 amphibian used a pair of Packard diesels in 1930. Another experimental plane, the twin-engine Stewart M-2, briefly had Packards. The Verville Aircraft Company tested one in an Air Coach. The Army National Guard tested Packards in two planes, the XPT-8A trainer and the XPT-8 observation aircraft. A Packard powered Bellanca Pacemaker on floats, owned by Transamerican Airlines, left Detroit in September of 1931 for the Shetland Islands off the coast of Scotland but disappeared. Weeks later, much of the plane was found afloat and it appeared to have landed intact. Engine failure was the prevailing theory.
Before long, the “whiz bangness” of the engine soon faded in the cold light of reality. The DR-980 garnered a lot of negative comments from test pilots. In one instance, a cylinder hoop broke and the engine launched a jug, barely missing the pilot. Pilots universally complained about the exhaust fumes and more than a few refused to fly Packard diesel-powered aircraft for this reason. The vibration was reported as dastardly, in a few cases resulting in airframe damage. When the Navy took a late production engine, number 120, for a 50-hour durability test in early 1931, it failed three times and the test was terminated. It was not recommended for procurement.
Roller rocker tips! Before you startoooing and ahhing, bear in mind they were common in the era. Metallurgy and lubricants had not advanced far enough to make rocker and valve tips able to withstand that sliding motion so rollers were commonly used. You can’t see it, but instead of a big coil valve spring Packard used 12 smaller ones around the valve stem inside the retainer cup.
This is one of the early production engines with a butterfly in each intake. Note also the lack of extra ribbing on the cylinder head versus the later production engines. This would also be a high-compression engine and is shown with the outer part of the propeller hub installed. Late in 1930 they began building the low-compression barrel-valve engines.
The barrel valve as seen from the inlet side. The barrel rotated to block inlet air to the valve port. No air filters were used, so whatever got past the prop could conceivably get into the engine.