McDonnell Aircraft, St. Louis, Missouri

20 December 1948: Afterburner Development for Westinghouse J34 Engine,
Progress Report 10, 15 August to 15 October 1948. (Report not found, but salient content likely included in the Summary Report up to November 1 that was discussed in Part 3b.)

21 January 1949: McDonnell Aircraft Corporation Report No. 1062, Proposal for Further Development of McDonnell Short Afterburner. This and the specification were forwarded to the Navy Bureau of Aeronautics (BuAer) on 28 January 1949. McDonnell (McD) now suggested to BuAer that their earlier proposal to continue development should be revised. They now wished to continue the development of an AB suitable for installation in an F2H type aircraft and conduct preliminary evaluation flight tests. They would use the J34‑WE‑38 engine under a new contract or amendments to NOa(s) 9022 (F2H‑1) and NOa(s) 9768 (F2H‑2) at no increase in the price of either contract. The estimated cost was included. The costs incurred prior to delivery of the last F2H‑1 would be charged to NOa(s) 9022 and subsequent costs to NOa(s) 6798. The completion of development and early flight work could be accomplished by June 1950.

Fig. 1. McD AB Design Schematic as of 21 January 1949

It was expected that the result of this and other additional development work would deliver an AB with multi-position, variable area nozzle and nozzle control for the Westinghouse J34‑WE‑38 engine and would be installed in F2H type airplanes when the engine became available. All work would be coordinated fully with Westinghouse. The specification for the developed AB was attached as McD Report S‑239 (below).

As a preface to a further description of the work to be undertaken, an outline drawing of the current design was provided.

 

 

Multi-position, Variable-Area and Nozzle Control – Development

Fig. 2. McD AB with its Fixed Nozzle Installed on a J34

The design had to provide an exit nozzle that could open and close continuously and symmetrically, prevent gas leakage, and that would be relatively immune to the extreme temperatures it would experience. McD felt they had made great strides in achieving the design requirements, having tested several such nozzles. Additional work was still needed to achieve an adequate service life, ease of fabrication, freedom from maintenance difficulties, and a minimum of complexity and weight. McD proposed that the current nozzle as modified be tested in conjunction with a McD short AB under static, sea level condition and under speed/altitude conditions to obtain performance data including thrust, fuel consumption, non-AB operation thrust loss, SFC increase due to the non-AB thrust loss, fuel metering, and nozzle control characteristics. It was anticipated this would require 40 hours of testing at a suitable sea level, static test facility. It was expected that the tests would indicate a suitable AB configuration (or configurations) and provide a basis for determining the probable service life of the complete AB. The speed/altitude tests were anticipated to require 30 hours of testing using the most suitable AB configuration (or configurations) obtained from the static test program and be conducted at NACA Cleveland or some other suitable government facility. Along with the other performance data, it was anticipated the testing would provide the ignition and blowout characteristics of the complete AB up to the maximum altitudes that could be simulated. McD would develop a suitable linkage connecting the multi-position nozzle to the actuator that would be furnished with the engine-control system. Automatic control systems necessary to adjust the nozzle area and meter fuel to the AB already being developed by the engine and other manufacturers would be adapted for use on the McD AB. (Such a system was under contract with Westinghouse for the J34‑WE‑32. The -38 would not have the AB components for fuel delivery or control. Perhaps McD was not aware of that? – Auth.)

Flight Tests
As soon as status and speed/altitude tests indicated a reasonably satisfactory AB performance and life, flight tests with an F2H type aircraft would be made using one complete AB that included a multi-position, variable area nozzle and an AB control system. These tests would require approximately 20 hours of flight testing. The results would provide data and prove the operational performance characteristics of the AB and AB control system when subjected to maneuvering conditions. Service life and maintenance requirements information would be provided. The initial testing would have the nozzle used in two positions. The program would work toward a fully automatic nozzle control system. During testing, a manual control would be available to the pilot to trim the nozzle during non-AB operation in order to obtain the maximum engine performance at all altitudes. The collected data would be used for programming the automatic control.

Fig. 3. Constant Diameter and Tapering Combustion Chambers for Reference

23 February 1949: A conference was held on 28 January regarding the McD proposal (minutes not found.) BuAer asked the Air Force if they were interested in continued development of the McD AB and were awaiting a reply. BuAer asked the Piloted Aircraft Division if they would arrange the required GFE or could make sufficient funds available to purchase such GFE in the event it appeared desirable to continue the proposed program. The proposal had stated that one (1) F2H type aircraft; two (2) J34‑WE‑22, two (2) J34‑WE‑38 engines and two (2) Westinghouse AB control systems would be required. The Power Plant Division (PPD) was unable to furnish any of those items. Unless such equipment could be made available, further consideration could not be given to the Air Force proposal.

BuAer requested a more detailed development plan. The test facility(ies) required availability had to be determined by the contractor and present a reasonable assurance that the proposed sequence of development tests could be carried out. A guarantee could not be made by the Bureau that suitable afterburner altitude test facilities could be made available at a government installation in time to obtain usable results before completion of the proposed program. The proposal stated that four (4) complete ABs would be built and that the cost also included use of a wind tunnel, use of a test cell, and construction of a sample burner. It made no mention of the quantity of ABs that would be produced for flight and ground test purposes, but stated that the cost breakdown included still applied. Delivery of one AB of final configuration, in addition to the test units, appeared desirable. Final action on the subject proposal was being withheld pending receipt of such information.

23 February 1949: Afterburner Development for Westinghouse J-34 Engine,
Progress Report 11, 16 October to 15 December 1948.

The McD cover letter again reviewed the results of the simulated altitude and high-speed tests with the AB with a fixed nozzle which had begun at the Lewis Flight Laboratory, NACA, Cleveland, Ohio on 8 October 1948 with testing continuing through October. (Also review the additional related data included in the 1 November 1948 memo to BuAer above.) Tests at Mach numbers from 0 to 1.01 and simulated density altitudes from 5,100 to 42,000 ft were conducted. Engine running operation with the AB attached for 22 hr had been conducted. Of those, 4 hr had been with the AB operating. Satisfactory ignition and blowout characteristics were observed. Ignition was smooth and consistent up to 30,000 ft. The high-altitude tests at altitudes up to 42,000 ft indicated the existence of a blowout range above 40,000 ft for high Mach numbers in flight. Blowout was characterized by gradual extinction of the flame, rather than a sudden blowout. The NACA report was expected to be released in February 1949. (The report would not be released until 2 June 1949).

Results of Testing: Development and redesign of the AB for flight tests was continued. The diffuser divider wall thickness (Fig. 9)was increased from 0.049" to 0.062" to eliminate flutter and fatigue failures. The divider was shortened from 17" to 13" for the same reason. Rigidity was increased with channel-shaped longitudinal beads. A flame shield (Fig. 10) was built into the turbine end of the diffuser cone to protect the turbine bolts from the damaging effects of a direct flame should the inner fuel manifold leak or in any way allow combustion inside the diffuser cone. The closely grouped fuel, ignition and control connections (Fig. 11) were altered and designed to be able to be located in any one of nine equally spaced locations on the AB circumference. With only minor changes the AB assembly could be adapted to a variety of single and multi-engine installations. segments when the nozzle was in the open position. The flaps were now ceramic coated to reduce the metal operating temperature. Super-fixed fiberglass wool was packed into the expanders and held in position by means of end plates to block the flow of gases through the expander sections and thereby protect the thin metal of the expanders from the intense heat of the combustion gases.

Fig. 13. “Breadboard” Solar Automatic AB Fuel Control Used for Testing	Fig. 14. Probable JA34‑MD AB Ignition Limit on J34‑WE‑38 at 12,500 rpm

A flight test AB incorporating the changes above was constructed and tested during the period of the report at the Westinghouse static-test facility. The operational characteristics were found to be similar to the prior AB and were found to be satisfactory. One variable nozzle failure occurred after 50 seconds of operation when one expander section burned out. The metal of the other expanders did not get heated enough to cause discoloration. The failure was traced to the loss of the fiberglass packing through a short, narrow gap at the hinge end of the nozzle, a gap that was unprotected by the flap. All such gaps were then covered by a welded extension of the protective flaps and no further failures occurred. After three 5-minute periods of afterburning and 11 hours of engine operation at Military and Normal rpm, two expander sections failed beam-wise. The nozzle was to be redesigned during the next reporting period to reduce the pressure load on the segments and increase their beam strength. Another nozzle with the changes would be constructed. An automatic AB fuel control was procured from the Solar Aircraft Corporation for use with the AB and a preliminary operational test of the control made. Approximately 80% of the required AB fuel was metered mechanically, the remaining fuel required to keep the TOT at a constant value during operation was metered electronically. Control bench tests were in progress. During the next period the control would be tested with one engine and AB under static conditions to establish its operating characteristics.

Fig. 21. (New) Design Comparison of the Model 3 and Model 4 Nozzle Contours

20 March 1949: The Air Force had agreed to have the second McD XF-88 airframe (No. 46-526) modified to accept McD short ABs after the airframe arrived at Muroc Field in California. The airframe was trucked to the field, arriving on 14 March 1949. Work on airframe reassembly was started immediately with the airframe 15% complete by the end of the 20 March reporting period. The work was being done under Air Force Contract W33-038-ac-14582.

21 March 1949: McD submitted the revised proposal and updated AB specification to BuAer, noting that there were no provisions for actually performing qualification tests in the enclosures. However, the model specification did include the qualification testing procedure for reference purposes. The estimated costs were those McD would incur in the event qualification testing was undertaken by Westinghouse as well as the costs to fabricate an AB and appropriate spares for the qualification testing. It was recommended that BuAer negotiate with Westinghouse for the actual performance of qualification testing. Discussions in regard to the possibilities of such testing had already taken place between McD and Westinghouse. Westinghouse was going to present a proposal to BuAer for such testing in the near future. The F2H-2 line drawing was included to emphasize the need for short ABs in such an airframe, which would allow retention of extreme angle of attack angles during take-off and landings.

21 March 1949: Afterburner Development for Westinghouse J-34 Engine, Progress Report 12, 16 December 1948 to 15 February 1949

The flight test Model 4 variable nozzle was fabricated for testing. The nozzle length was reduced from 10" to 6", reducing the operating loads and actuation force on the nozzle by 50% and was hoped to prevent the structural failures experienced on the Model 3 nozzle. The variable nozzle area was left unchanged in the new design. The nozzle cone and actuation angles used are shown in the Figure 15. The new model was ready for shipment to Westinghouse at the end of the reporting period.

8 April 1949: McD sent BuAer a memo regarding Contracts NOa(s) 9022 and 9768 for the F2H-1 and F2H-2 airplanes and their improvement program status. The main focus of the program was to improve the high Mach number characteristics of both airplane models. Aside from wing profile modifications underway as a result of wind tunnel testing results, a continued push was made for the McD AB.
Memo Item 3 proposed that a set of J34‑WE‑30 or -34 engines be equipped with McD short ABs with fixed exit nozzles and be installed in an airplane at the earliest possible date to obtain performance data as an interceptor when so equipped. McD thought the high rate of climb would likely turn the F2H-1 into an effective interceptor. They recommended the AB program be approved and work proceed with all possible effort including installing engines with ABs on BuNo. 122530. The airplane performance with afterburning would be reviewed at the time of the AB flights of BuNo. 122530.
Memo Item 4 stated that the expected fixed area AB installation could be accomplished by 30 July 1949 to permit BuAer to review the AB situation and determine at that time whether or not the program outlined in McD’s memo of 21 March 1949 should be continued to its conclusion. It was hoped contractual authorization to proceed would be issued at an early date. The estimated cost would be $1,160,100. This covered 30 hours of flight testing, 10 GFE J34‑WE‑34 engines and 3 Westinghouse AB controls, qualification liaison with Westinghouse and 2 J34‑WE‑34 engines. It did not include the basic cost of the GFE F2H type airplane, previous expenditures by McD on the AB, or cost of Westinghouse assistance on a qualification test.

24 April 1945: The XP-88A powerplant adjustments were completed except for final trimming on the left-hand engine. The McD ABs were installed on J34‑WE‑22 engines equipped with a small fixed nozzle designed to allow development of full engine thrust with the ABs inoperative. The AB fuel system and controls were not installed at that point. The AB nozzles were not calibrated for engine operating temperature change accompanying an area change so the trimming operation was being done by trial and error in small increments.

26 April 1945: XP-88A No. 46-526 flew for the first time with the inoperative fixed-nozzle McD JA34-MD ABs installed on both engines. The flight was for 15 minutes and the pilot reported a complete absence of the slight aft fuselage shake which was a reported characteristic of the first prototype even in smooth air. The difference between the two aircraft was deemed likely caused by different airflow because of the further aft exhaust exit of the ABs and the re-faired installation around the bottom rear behind the exhaust nozzle. (See Fig. 15)

27-29 April 1945: Further flights of the XP-88A revealed that it was impossible to attain full thrust for take-off due to the limiting TOT being reached at approximately 11,500 rpm instead of 12,500 rpm. Modifying the nozzle size for full thrust would have been impractical, as “the increase in the engine duct efficiency with airspeed would reduce the available thrust in flight to a great extent by reduction of the TOT.”

9 May 1949: Afterburner Development for Westinghouse J-34 Engine, Progress Report 13,
16 February to 15 April 1949 Testing Report
Variable Model 4 Nozzle: The variable nozzle was tested using the manually operated nozzle actuation system while at the Westinghouse facilities. The operating life of the new nozzle was to be determined as well as the performance characteristics. Operation during calibration for 6.7 hr in non-afterburning operation was satisfactory. After 15 seconds of afterburning, the flap sections of the nozzle started to burn out and after 1.5 minutes, 8 flap sections were partially burned away. Partial afterburning using the undamaged inner cone fuel only were undertaken. After 68 minutes, no further deterioration of the nozzle could be noted. During these tests, an unusual high-frequency howl was produced at high fuel/air ratios. A maximum thrust augmentation of 18% with an SFC of 1.85 was obtained. Further complete full AB operation tests were undertaken. The nozzle flap segments burned out one by one and after 4.5 minutes the nozzle and shroud burned out at one place. Apparently, the ceramic coating gave very little thermal protection. Since it coated only the inner side of the flaps, it was believed possible that covering both sides might gain better protection. Considerable large-scale flaking of the ceramic was noted. Future tests would investigate the benefits of coating both sides with ceramic and also discovering improved ceramic attachment methods.

Nozzle Temperature Reduction: The nozzle had been redesigned to provide a better radial distribution of the temperatures in the combustion chamber with lower temperatures in the vicinity of the nozzle segments. The changes were a step type flame holder being installed on the divider within the combustion chamber in lieu of the previously used outer flame holder. The change was to remove the flame from the vicinity of the AB walls and allow for a portion of the engine turbine air to flow outside the flameholder area adjacent to the combustion chamber skin. A second AB was modified to provide for water injection ahead of the nozzle to cool the nozzle directly. The calculations indicated that the temperature adjacent to the nozzle segments could be reduced satisfactorily by the injection of approximately 2,000 lb of water per hour. Both ABs were tested at Westinghouse and about 20 hours of non-AB operation were conducted. The water injection was not used. A determination of performance with and without the AB attached was made. The average thrust loss due to the AB in the range of 11,500-12,500 rpm was 2.1% and the increase in SFC was 2.8%. Tests with the AB operating and the boundary layer cooled unit would be tested during the next reporting period.

Fuel Control System: The complete AB fuel control system mock-up was operated for 2 hr and 20 minutes during which time 24 separate tests of the system were made. The results would be used to determine the fuel-metering schedule to be set on the control. The schedule would include fuel flows, pressures under simulated internal conditions and reaction of the control system to varying compressor discharge pressures and TOT’s.

16 May 1949: BuAer authorized McD to installed fixed area nozzle short ABs on one (1) F2H-1 and ground and flight test as necessary to ascertain performance of the afterburner installed. The work was to be done at no increase in the contract price. A pencil note on the wire copy says “Request proposal be submitted”.

16 May 1949: The St. Louis BARR reported by wire that a proposal was being written as requested for providing flight testing of J34‑WE‑34 engines as installed in the F2H-2. The program would be coordinated with Westinghouse. To save time, McD was recommending the installation of J34‑WE‑34 engines in the first or third F2H-1 (or both) airplanes and reinstallation of J34‑WE‑30 engines at the end of testing. While the installations would not increase the contracts’ prices, the testing called for would, however, require an increase in price. If acceptable to BuAer, McD recommended J34‑WE‑34 engines assigned to contract NOa(s) 9768 be authorized for use in the F2H-1 airplanes and the necessary check flying. Authorization within a few days would permit McD to install the -34 engines during the current layup period to considerably expedite test results.