Service Testing & Compressibility

Air Classics, Apr 2005

AS THE GLEANING YP-38s TOOK TO THE SKY, NEW AND DEADLY PROBLEMS WERE UNCOVERED IN THE BASIC DESIGN

A beautiful blue sky covered the Burbank area on 5 November 1941, as over 25,000 Lockheed workers gathered during their lunch break to listen to Maj. Gen. Henry "Hap" Arnold, head of the Air Corps, to give a pep talk on how America was becoming the "Arsenal of Democracy" by producing a vast variety of weapons to ship to the Allies fighting the Axis. Little did anyone realize that America would be at war in less than a month. For now, life was good in Burbank. Lockheed was hiring at an unprecedented rate and for the hordes of new well-paid workers, it appeared that the dark days of the Great Depression might well be at an end.

To high-light the speech, Hudsons and Venturas in Royal Air Force markings flew overhead accompanied by a few Lightnings. However, the specter of compressibility had not been solved and was posing a major threat for the sophisticated design.

As the workers filed back into the hangars, test pilot Ralph Virden was strapping into a gleaming YP-38 prior to taking the aircraft aloft for a series of power dives as part of a typical day's work for a factory pilot.

Ground checks over, Virden started the Allisons, taxied to the active and took off. He was soon climbing out to the west from the Lockheed Air Terminal for a series of test dives and these were apparently completed successfully, for the YP was back over the Burbank area some 15 minutes later. Numerous eye-witnesses on the ground saw what happened over the next few minutes. The YP was seen in a dive, making an unearthly shriek, followed by its fluttering tail assembly which had separated from the airframe. Even Kelly Johnson heard the YP's fatal dive from his office, recalling later that the sound probably came from the propellers hitting the air at angles outside the "realm of a normal flight path."

The YP crashed into a house at 1147 Elm Street in neighboring Glendale, literally blowing the dwelling in half, and killing the pilot on impact. Fire and police officials reacted quickly and, once at the burning house, they expected to find fatalities only. However, owner Jack Jensen was discovered asleep in his bed - completely unaware that the Air Corps' latest fighter had destroyed his house!

Why had the YP crashed? First, we must go back to the wreck which destroyed the XP-38. That plane had gone down essentially unproven, but Hap Arnold and other influential officers lobbied long and hard for the new design and this resulted in a contract issued on 27 April 1939 for 13 YP-38s. The "Y" in the designation denoted that the new aircraft would be for service test and evaluation in preparation for production aircraft entering operational squadrons.

Contract 12523 spelled out the terms for the production of the YPs, but the YP was to be vastly different from the XP and problems were to develop accordingly. Lockheed gave the YP- 38 the new company designation Model 122 and the engineering team went to work refining and developing the basic design, which would need extended development to make it a real fighter.

Among many changes were the installation of the latest variants of the Allison V-1710 engine, namely the F series -27(F2R) and -29(F2L), which had both propellers turning out-board in an effort to reduce airflow turbulence over the tail surfaces. If both engines were operating correctly, then the effect of torque would be effectively counteracted. The management at Lockheed could sense that massive aircraft orders were in the very near future but, oddly, this optimism did not extend to the P-38.

Management thought that the Air Corps would not order more than 80 P-38s and this reasoning would lead to later problems in adapting the design for mass production. The company made plans to rapidly expand, and nearby buildings (including a distillery) were purchased while construction, was started on new facilities. An intensive drive was also undertaken to hire and train new workers (up to 500 workers a day were being hired during 1941).

The distillery was converted to handle the production of P-38 sub-assemblies and the building of the YPs, but the expansion proved to be so rapid that work began to flag on the YPs and even though initial drawings had been approved and released by mid-1939, actual fabrication work did not begin until early 1940. As the plant expanded in a rather disjointed manner, delivery clerks had to resort to the use of roller skates to deliver blue prints and documents between the diverse hodgepodge of buildings.

Robert Gross, president of Lockheed, began acquiring farm land around the airport and he even purchased the field outright from United Air Lines. The latter acquisition also included several hundred acres of land and resulted in changing names from Union Air Terminal to Lockheed Air Terminal. As more orders poured in from the British for additional Hudsons and follow-on Veiituras, Gross and his staff knew that the distillery would not be adequate for fighter production so other plans were made.