de Havilland H-1 (USAF)
Case History of the Halford Engine (de Havilland H-1)
Compiled by Kimble D. McCutcheon
Published 6 Nov 2023; Revised 8 Nov 2023
de Havilland H-1 (USAF) |
General of the U.S. Air Force Henry Harley "Hap" Arnold prohibited the major U.S. engine manufacturers (Allison, Pratt & Whitney and Wright Aeronautical) from working on gas turbine development during WWII. As a result, early U.S. gas turbines were built by concerns with experience in steam turbines, Allis-Chalmers, General Electric and Westinghouse. This short case history summary covers the Allis-Chalmers Supercharger Works' abortive attempt to build the 3,000 lbt de Havilland H-1 engine in the United States. |
The Halford H-1 jet-propulsion engine, which was manufactured in the United States by the Allis-Chalmers Manufacturing Company of Milwaukee, Wisconsin (hereinafter Allis-Chalmers), was designed and produced in England by the de Havilland Aircraft Company, Ltd. (hereafter de Havilland). The Materiel Command was interested in the development almost from the start, Major Donald J. Keirn of Power Plant Laboratory, Wright Field, having initiated liaison with the H-1 group in England in September 1941. As early as October 1942, after another trip to England, Mayor Keirn recommended the procurement of several engines from de Havilland if the unit proved to be operationally satisfactory. The H-1 unit were successfully flown in a FP/40 airplane on 5 Mar 1943, and shortly thereafter negotiations were started for the procurement of several engines from England and for the manufacture of similar units in the United States. At the time, the Halford engine was delivering more thrust than was hoped for in the Whittle developments. In England, the Civilian Advisory Committee to the Ministry of Aircraft Production felt that it showed the greatest promise of all the jet engines of getting into operational use in World War II and recommended that the United States undertake its production rather than depend upon the purchase of British engines.
Plans for the Halford program in the United States were formulated at a conference on 14 Apr 1943 at the Bureau of Aeronautics (hereinafter BuAer), Washington, DC, attended by BuAer, Army Air Forces, the British Air Commission and the Bell Aircraft Corporation representatives. The outcome of this meeting was that Allis-Chalmers was selected to produce the engine under a contract with the Navy, with the understanding that Army Air Forces' requirements would be supplied by the Navy. BuAer formally requested British Air Commission to furnish one complete H-1 unit as soon as possible, in addition to the unit for which the Army Air Forces had already completed negotiations, and ten units as soon as convenient, and complete working drawings and data. On 7 May 1943, the British Air Commission replied that information concerning the engine would be released to BuAer upon compliance with the interchange agreement between the United States and Great Britain, and at the same time the British Air Commission stipulated that the American-made units be called the Halford Jet Propelled Unit, Type H-1.
The Navy had submitted its plans for production of the H-1 engines to the Army Air Forces by 27 May 1943. and on that date Brig General B. W. Chidlaw, Chief of the Materiel Division, Washington, stated that BuAer proposals were satisfactory, provided that the Army Air Forces were allotted four of the 10 units to be received from the British. Fifty per cent of the initial Allis-Chalmers order, and the same percentage of all subsequent orders. On 2 Jul 1943, BuAer advised that these conditions were acceptable to the Navy but that the British Air Commission had informed them that the H-1 unit was not quite ready for production. A short time later, Mr. Robert A. Lovett, Assistant Secretary of War for Air, who had seen the Halford engine in operation in England and had recommended that the Army Air Forces get it into operation and use at the earliest possible moment, verbally expressed to Gen Chidlaw his concern that the Army Air Forces had permitted another organisation to sponsor its development.
By 2 Jul 1943, Allis-Chalmers had agreed to manufacture the Halford engine, provided that it was satisfactory from a technical standpoint. Subsequently. several Allis-Chalmers officials went to England to investigate the general status of the H-1 program and became interested in immediately entering into the manufacture of the engine. On 26 Oct 1943, Allis-Chalmers submitted to BuAer a proposal containing the following principal points: (a) an estimated unit cost of $81,198.33 for an initial order of 30 engines; (b) additional equipment in the amount of $250,000.00, to be supplied by the Government; (c) a delivery schedule providing for the delivery of the first unit eight months after the receipt of authority to proceed; (d) use of space and equipment in the existing supercharger plant; and (e) the right to purchase as many rough or partially machined parts from de Havilland as the Ministry of Aircraft Production world permit. The proposal was later adjusted became of increased Army Air Forces' requirements. The number of units was creased to 40, 25 for the Army and 15 for the Navy; the facility request was raised to $545,000.00 and a delivery schedule of the first unit in November 1944, four in December, and six a month thereafter, was given. Allis-Chalmers specified as a condition of attaining this schedule that the prototype and the parts for the 40 units must be received from de Havilland by 1 Apr 1944. On 21 Jan 1944, it was reported that BuAer had given Allis-Chalmers a letter of intent. By 19 Apr 1944, Allis-Chalmer had received Navy Contrast NOa(s) 2593 for 40 H-1 units.
The request for additional facilities proved to be a major hindrance to early production of the engine, with clearance not being accomplished until 13 Jun 1944. On 1 December 1943, BuAer informed the Army Air Forces that Allis-Chalmers had given definite assurance that the H-1 project would in no way interfere with Army Air Forces' supercharger production. Because the supercharger plant was a Defense Plant Corporation facility sponsored by the Army Air Forces, BuAer requested the Army Air Forces sponsor an amendment to the Plancor (a contraction of Defense Plant Corporation) agreement to cover the additional facilities. On 20 Jan 1944, the Army Air Forces completed its investigation and agreed to the expansion. The final obstacle to the clearance of the amendment had to do with War Production Board's approval of the manpower requirements. Labor market conditions in Milwaukee were critical, and the company found that it could not sign the statement that no additional manpower would be required in connection with the expansion. The War Production Board went so far as to suggest the cancellation of the H-1 contract for manpower considerations. It became necessary eventually to reduce the supercharger schedule from 4,500 to 3,800 units a month for eight months in order to release enough labor to perform the H-1 work without adding to the labor force. After this had been done, the War Production Board on 13 Jun 1944 approval the request for additional facilities. The amount required had been reduced to $469,977.00, and sufficient funds were said to exist in Plancor 185 to cover the estimated project cost.
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| Lockheed XP-80 | de Havilland H-1 Under Test (USAF) | ||
de Havilland-built Halford engines we tested by The Army Air Forces long before Allis-Chalmers engines became available. The Lockheed Aircraft Corporation (hereinafter Lockheed) designed the XP-80 around the H-1 engine, and the first unit to received from England was to be sent directly to Lockheed. It had been estimated that a flight engine would be shipped by 1 Sep 1943, but numerous difficulties encountered in England with the engines delayed its arrival. On 15 Oct 1943, Gen Chidlaw advised the British Air Oommission that the non-arrival of the first unit was seriously jeopardizing the XP-80 project. The unit was finally delivered to Lockheed on 2 Nov 1943, and installation and tests proceeded immediately. However, a collapse of the inlet duct necessitated its return to England for repair, and by 9 Dec 1943 it had been returned. Shipment of a replacement unit was expected on about 11 Dec 1943 The second engine had been received by Lockheed by 8 Jan 1944, and on that date the XP-80 made Its first flight at the Muroc Flight Test Base, Muroc, California (hereinafter Muroc). A modified unit, the third to be received and the second flyable engine was received by 16 May 1944.
The delays encountered in getting engines from England and in getting production started at Allis-Chalmers caused the Engineering Division, Wright Field, to recommend. on 9 Feb 1944, that General Electric Company's jet unit be used in the 13 YP-80A airplanes instead of H-1 units. Because of increased thrust, the I-40 had more possibilities than the Halford, and Lockheed could build the airplanes long before any promise could be secured from the Navy about the Halford engines. After this substitution, the Halford became a replacement for the jet engines developed by General Electric. Although no application existed for the H-1 units, it was believed advisable to have another manufacturer of jet engines, and Allis-Chalmers was the logical selection. The approval of additional facilities for Allis-Chalmers in June 1944 was followed by an agreement that an effort would be made to maintain the previous delivery schedule of one engine in November 1944, four in December, and six a month thereafter.
H-1 production at Allis-Chalmers proceeded slowly even alter War Production Board's approval for the expansion was secured, and on 26 Jun 1944, Allis-Chalmers submitted a detailed report on the reasonings: drawings were constantly being changed by de Havilland; no production parts, other them a shipment received on 13 May 1944, had been received from de Havilland, although notice had been received that five partial parts sets were in New York and many rough and semi-finished parts which de Havilland had Agreed to furnish had not been included in those shipments. The situation was critical because a large percentage of the work had been subcontracted. Since Allis-Chalmers could not furnish them with the necessary parts, the subcontractors were scheduling work from other manufacturers ahead of H-11 work.
Flight test operations were continuing, meanwhile, at Muroc, with the engines received from England. Flight tests between 26 and 30 May 1944, with the modified engine, indicated that the XP-80 was the fastest America airplane and possibly the world's fastest, at altitudes up to 40,000 feet, although some difficulty was experienced with the engine. The XP-80 had been accepted by the Army Air Forces by 16 Nov 1944 and was to be flown by a tactical group for several months for evaluation. The group, the 412th fighter Group, experienced serious difficulty with the airplane because of fuel leakage into the aft fuselage and had returned it to Muroc for a performance check by 5 Jun 1945. On 6 Jun 1945, Muroc stated that information had been received that the XP-80 had been assigned to the Army Air Forces Training Commend at Chanute Field, Illinois, for training. Since this was the only engine in the U.S. for testing H-1, Muroc believed it more valuable for test purposes than for training. Aircraft Projects Section, Engineering Division , Wright Field, supported Muroc's position and requested that the XP-80 be assigned to Muroc for 365 its for tasting H-1 engines. By 25 Jun 1945, the XP-80had been made available for flight tests at Muroc until 10 Jun 1946.
Allis-Chalmers' production of the Halford engine never reached the contemplated amount. On 20 Jul 1945, BuAer advised the Army Air Forces that only 8 of the 40 engines on contract could be completed. The reduction was a result of the executive action that had cancelled lend-lease, and, therefore, made it impossible for Allis-Chalmers to obtain the necessary parts from England under reverse lend-lease. Four of those engines would be required by the Navy. On 1 Sep 1945, it was apparent that
seven complete engines and one incomplete engines were all that Allis-Chalmers could finish, and the Army Air Forces requested the three complete engines not needed by the Navy. The first of these engines was delivered to Muroc in August 1945, the second was delivered to Muroc in September 1945, and the third was delivered to Wright Field in October 1945.
Flight tests of the Allis-Chalmers-built H-1 unit rated at 3,000 pounds thrust and of a sde Havilland-built engine re-rated at 2,700 pounds thrust were discussed at a conference in Fighter Branch, Engineering Division, Wright Field, in June 1945, and it was agreed that speed performance tests of the XP-80 with these engines would be desirable. By 13 Dec 1945, flight tests were being conducted at Muroc on the XP-80 equipped with an Allis-Chalmers engine, at an altitude of 20,000 feet. However, Aircraft Projects Section, Engineering Division, Wright Field, requested that these tests be terminated because of difficulties encountered with engine maintenance.
A similar request was made on 21 February 1946 by Aircraft Projects Section, Engineering Division, Wright Field, in regard to the de Havilland engine. It was not believed advisable to continue with work to modify the XP-80 for further tests, since sufficient information bad been submitted to the British to satisfy the original request for information concerning the operation of the Halford engine. On 10 May 1946, the Wright Field Plant Liaison Engineer at Muroc recommended that no more flying be done by the XP-80 with de Havilland-built engines because of excessive aft fuselage temperatures. At the same time he summarized the operation of the engines received from England as much an was possible in view of the fact that the XP-80 had been grounded for most of the preceding nine months. Three flyable engines tad been received from England, the third having been sent as a replacement for the second, which had been returned to England for overhaul. The greatest mechanical disadvantage of the de Havilland engine had been the non-uniform distribution of air at compressor discharge, which had resulted in unequal temperature distribution in the combustion system.
Army Air Forces' participation in the Halford program ended in Jeaurary 1947 with the shipment of the three Allis-Chalmers-built engines to the Navy. On 30 Oct 1946, the BuAer representative at Wright field had asked that two of the units, believed to be unused, be shipped to the Navy without a transfer of funds. On 12 Nov 1946, Power Plant Laboratory, Wright Field stated that the three engines, all of which were slightly used, could be shipped but that they were unassembled and would require overhauling. BuAer advised on 2 Dec 1946 that the engines were wanted, nevertheless, on a no-accountability basis. and specified that one engine be shipped to the Naval Air Material Center, Philadelphia, Pennsylvania, for use as spare parts in support of qualification tests of H-1 units, and two engines be shipped to the Naval Air Station, Patuxent River, Maryland, for use as spare parts to maintain H-1 units installed in XF15C aircraft. On 4 Feb 1947, Wright Field was informed that the three engines had been shipped as directed, on 9 Jan 1947.
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