Solar Aircraft Company, San Diego, California

To expedite the program and test the controls, the first unit would be accepted without changes 2 and 5. The Solar four-strut exhaust collector was needed to run tests until a Westinghouse collector of increased strength could be made available. The ABs would be delivered without fuel control components. In the interim, the fuel control would have to deal with a very narrow temperature control band which would have limited ability to deal with malfunctioning of the Manning, Maxwell & Moore (MM&M) electronic equipment.

30 June 1948: Experimental engine serial WE002035 was diverted from the CV XF6U-1 program for testing required by Contract NOa(s) 9602. The contract showed the Government Furnished Equipment (GFE) Solar test ABs would cost $7,908 without their controls.

7 July 1948: CV AB Testing Initial Progress Report for May-early June 1948 The ground test stand was complete. Due to the fact that the Solar ABs would not be available until sometime between 15-30 July, a Ryan AB was installed on the X24C-4B engine. The rationale used was it would be advantageous to the general AB development program to further evaluate the Ryan AB in addition to the testing being done at NACA. (This testing was covered in the Ryan article.) On 7 June, the Solar AB installation had begun along with its MM&M automatic control.

9 July 1948: The Navy Bureau of Aeronautics Representative (BARR) notified BuAer that they were unable to comply with paragraph 4 of BuAer’s 25 June 1948 letter. Paragraph 4 “recommended that Solar continue to investigate the cause of sudden combustion roughness before undertaking the 70 hour endurance program." All present funds were allocated for Items 8, 9, 10, 11, and 12. They requested $20,588.40 in additional funds and five (5) additional months to fully comply with BuAer recommendation.

9 July 1948: CV requested Westinghouse J34-WE-30A engines for the XF7U-1 as they were the only 24C engines with the flyball governors needed to operate with an afterburner. Currently, four J34-WE-22 engines (of 6 requested) had been allocated to the contract. The two J34-WE-30A engines were to be delivered before 1 October 1948.

Fig. 1. Chance Vought AB Ground Test Stand with Initial Ryan AB Installed. June 1948.

16 July 1948: The BARR notified BuAer that investigation and elimination of the combustion roughness in the AB was a necessity. As noted earlier, funds needed to be allocated for this unexpected phase of development in order not to jeopardize funds available for other contract phases under Amendments No. 8 and 9. Solar’s estimated amount for the study was known to be imprecise due to the indefiniteness of the amount of further testing and experimentation that would be required. It was pointed out that in the BARR’s opinion, the 40‑hour normal rated phase of the endurance test could be eliminated without any detrimental effect on the AB endurance evaluation. A saving of time and funds could be realized in that manner. He recommended approval of the additional requested funds.

16 July 1948: The BARR was instructed by wire to have Solar conduct the roughness investigation under Item 10 of Amendment 9 to the contract. In addition, they requested the completion date of the investigation be expedited as much as possible since delay under the present circumstances was most undesirable. If J34-WE-30A engines would not be available, BuAer was requested to procure six flyball governors to be used on the J34-WE-22 engines. Written notes at BuAer state that -30A engines would not be available on time and that the flyball governors would have to be procured. Further notes state that “X" engines were supposed to be used in “X" airframes and the “X Programs" department was responsible. Production engines, if used in “X" airframes would mean less engines available to support the production program. The budget did not allow for GFE equipment requests.

19 July 1948: Chance Vought (CV) wrote to BuAer asking for a copy of the Westinghouse Engine Bulletin No. 29. This bulletin had cleared production J34-WE-22 engines to be run at 12,500 rpm if the conditions in the bulletin were confirmed on an engine-by-engine basis. CV asked for specific approval to be granted for five production engines listed by serial so that the flight engine running in the XF6U-1 and four other engines scheduled to be ground tested in the XF7U-1 in the near future could proceed on schedule. BuAer permission was granted on 29 July 1948. (Note: At this point, no production version of the J34 had run with an afterburner attached or operated.)

28 July 1948: Solar wrote to BuAer informing them that the vendor making a large part of the AB controls was extending their delivery schedule from June to September for Item 9. An extensive development program being conducted with CV had uncovered many desirable changes that would improve function over that originally contemplated for the automatic control. They asked for consideration to approve this extension of time.

28 July 1948: Solar asked that summary reports and progress reports of other agencies engaged in similar (AB) work under Navy contract be made available to Solar for information, specifically that of Westinghouse, McDonnell and Chance Vought.

29 July 1948: BuAer agreed with a CV suggestion to eliminate the simulated altitude AB testing of the Solar AB but added seven more weeks of ground testing at no increase to the cost of the contract.

30 July 1948: By memo, the BARR was encouraged to expedite the roughness elimination program as a production AB was needed at an early date. The BARR’s suggestion of minimizing the endurance testing Normal running was rejected. It was believed that the Normal running would duplicate the conditions encountered by the AB while installed in an aircraft and help indicate the reliability and serviceability of the Solar “device".

30 July 1948: The BARR was instructed to use pecification 24C4C-2 in Specification Specification WAGT-24C4C-2B dated 24 February 1948 for AB performance calculations.

4 August 1948: BuAer reviewed the acceptances of the Item 5 ABs in regard to the acceptance augmentation levels for each and stated that they were interested in attaining the maximum thrust for the XF7U-1 AB. It was requested that Solar demonstrate that the ABs were capable of at least 35% augmentation before acceptance by the BARR.

Fig. 2. Solar A-103 Model AB Installed in CV Test Stand for June Period Testing.

12 August 1948: The BARR at CV requested permission from BuAer to overhaul the turbine section of the test engine WE002035 using parts available under spares contract NOa(s) 3962. This would allow the engine to continue to be used for ground testing only. Two overhauled experimental engines, WE002065 and WE002066, would be available in three to six weeks. One of these engines was requested to be assigned to the test program so WE002025 could be returned for full overhaul.

13 August 1948: BuAer confirmed to CV that the ABs for the three XF7U-1 airframes would be delivered on the following schedule: 2 in October, 4 in November, and 6 in December 1948. The ABs would be redesigned to attach to the J34-WE-22 engines with 48 bolts. The exhaust nozzle casings would include a provision for 9 thermocouples. CV was authorized to convert the standard 48 bolt flange to a quick disconnect flange type attachment.

16 August 1948: CV Progress Report for July 1948
The Solar AB used was unchanged from the June activities except for the burner ring, which had been used in the XF6U-1 testing program; it had been sent to Solar for repair and returned. The floating eyelid position had been determined by disconnecting the actuating push rods and running the engine. The eyelids opened gradually as rpm was increased to 12,000 rpm and remained in that position as the rpm was reduced to any lower rpm. The gross thrust obtained at 12,000 rpm (dry) was 1,750 lb.

The blow-out switch was tested with the AB running and the eyelids open. It was determined that without a blow-out switch protection in the automatic control system, the AB would continue to burn at any rpm at fuel flows less than 500 lb/hr. The modified CECO AB fuel control valve was rechecked for schedule fuel flows to determine minimum and maximum flows. The relief valve on the Pesco electric driven pump had to be set almost to its maximum setting to obtain the desired fuel flows at 12,000 rpm.

The Aerotec pressure surge switch that triggered the opening of the eyelids was tested. Normal operation was obtained during tests at 9,000, 10,000 and 12,000 rpm. However, on a simulated carrier wave off acceleration from 9,000 to 12,000 rpm, the pressure switch opened the eyelids before the AB was started. The AB refused to start. A needle valve in the pressure line of the switch was readjusted and the AB was able to start during the repeated test. The automatic fuel control worked satisfactorily during the testing.

Using experimental data a pressure ratio switch was designed and constructed by the Aerotec Company. Checks of this switch were made during AB starts and simulated blow-outs at rpms from 7,500 to 12,000 with minimum and maximum AB fuel flow available from the automatic fuel system. With the maximum fuel flow available, the AB would start and stay on, and the eyelids would open automatically at any rpm. At minimum fuel flows, the blow-out switch would shut the AB off inconsistently at 7,500 rpm, but consistently at 8,500, 9,500 and 10,500 rpm. Further tests were run with constrictors in the P2 line to delay the eyelid open signal so that AB combustion could progress further and become more stable before the eyelids opened. Various constrictors from 0.013" - 0.025" were used and either the eyelids did not open soon enough or the eyelids did not close soon enough after a blow-out occurred. Further testing of a restrictor in the eyelid actuating air cylinder supply line was planned.

During testing the burner ring was found to be cracked and two cracks were found in the ring tubes, which were located between the gutters. The cracks were welded and the burner ring reinstalled. The burner ring had 69 minutes of AB time and 561 minutes of total time before failure. Since the welding repair, 111 minutes AB and 336 minutes total time had been accumulated without a failure.

Fig. 3. MM&M and CECO Fuel Control Schematics Drawn by CV in June 1948.

July 31, 1948: Engine WE002035 was found to have an excessively warped first-stage turbine. An engine overhaul was required.

XF6U-1 Flight 193 BuNo 33532: After diving from 15,000 to 12,000 ft at 12,000 rpm, “the AB was turned on with the fuel control in MANUAL (preset to 4,700 lb/hr) and the eyelids opened by the pilot after the AB ignited. The AB fuel control was then switched to automatic and the throttle adjusted to give 12,000 rpm. Although the engine speed decreases when the afterburner fuel flow is switched to automatic, the loss can be checked by the pilot easily. When the afterburner is turned off the pilot must immediately cut back on the throttle or the engine will rapidly overspeed beyond 12,500 rpm.’

30 August 1948: Solar quoted BuAer $384.73 each for 12 H070000000 tailpipes for the XF7U-1 program. (Note: These were tailpipes, not afterburners.)

2 September 1948: BuAer notified the BARR that three additional engines were being made available to the afterburner program.

2 September 1948: Separately, BuAer finally responded to the CV request for J34-WE-30A engines with flyball governors stating it would be impractical to do so. Additional J34-WE-22 engines were being evaluated. Holley had been contacted to determine if it was possible to procure flyball governors for the XF7U-1 program separately. No assurance had yet been received.

8 September 1948: At Patuxent River Naval Air Station (PaxRiver) where all XF6U-1 flying was being done, the MM&M fuel amplifier was found to have an electrical fault. MM&M representatives worked a full day determining the reason for the fault and were making the necessary changes. The engine and AB were removed for replacement of the burner ring and installation of a flyball governor.

9 September 1948: The PaxRiver station was canvassed to locate hydraulic fittings required for the piping changes on the flyball governor on the XF6U-1. After governor installation, a discrepancy in the ground run data caused a fuel flow check to be made. It was found the engine fuel flow meter had a 50-70 lb/hr lower flow than the AB fuel flow meter for corresponding fuel flows.

10 September 1948: Ground testing (no number) – Engine starts resulted in the second having exhibited a very rapid acceleration with rapid rpm surges accompanied with a roaring sound. A strong smell like burning rubber was observed after engine shutdown along with smoke from the engine compartment. Not conclusively identified as the cause, it was surmised that it was caused by the oil placed on the burner ring bolts prior to removal and the installation of new gaskets. The following runs did not exhibit smoke or abnormal odors.

The following start also exhibited surge and engine noises but of a less violent nature. Acceleration in stages showed rpm hunting that lessened as the rpm rose. Stable runs were made at 11,000, 11,500, and 12,500 rpm. An acceleration run from idle to 11,000 rpm was attempted but compressor stall was so violent the engine was shut off. A governor acceleration speed adjustment was made. On restart, the engine exhibited the same behavior. The lack of emergency fuel pump pressure had been noticed during the engine runs. The EMP pressure lines and the pressure line to the cross-over valve were found to be reversed. This was corrected and the next run exhibited improved acceleration characteristics. The idle stop was tried and did not correspond to the flat spot on the governor. Testing was stopped.

11 September 1948: The XF6U-1 had its throttle linkage and movable throttle stop adjusted with the engine running. These were made to coincide with the flat spot in the governor and the quadrant idle stop. The governor factory setting for the flat spot was 4,500 rpm and this was not changed for fear of damaging the governor. Eyelid opening checks were made at various speeds, these initially found to be causing an immediate overshoot of engine speed of 200 rpm, decreasing to 75 rpm over original setting. At 12,000 rpm, the overshoot was 500 rpm, considered to be too high. Ground run 271 – After a leak check, an automatic AB start was attempted but the eyelids opened immediately after placing the switch to the “ON”; position. The pressure lines to the switch were found connected backwards and were corrected. The next two automatic starts were unsuccessful, blow-out occurring immediately after lighting off. The next eight AB starts were made at speeds between 11,500 and 12,300 rpm. All were good starts and the amplifier held the turbine out temperature very well at differing throttle settings. The 500 rpm overshoot on light-off was a concern. A check of the blow-out circuit while in manual was successful.

14 September 1948: Ground run 272 – Engine run at 12,000 rpm for fuel amplifier setting and turbine out temperature. Two AB starts were made at 10,500 rpm and one each at 7,500 and 11,000 rpm. All starts were satisfactory.

Ground run 273 – The fuel amplifier was reset for the minimum value to investigate the effect of low turbine temperature settings on AB starting. AB starts were attempted at 10,500 and 11,000 rpm, but the fire blew out as soon as the eyelids opened. After a reset of the amplifier to the turbine outlet temperature (TOT) at 10,500 rpm, another AB start failed. It failed again at 11,000 rpm. The amplifier was reset to 12,000 rpm and good AB starts were made at 9,500, 11,500 and 12,000 rpm. With the amplifier set to 12,500 rpm TOT, successful starts were made at 9,500, 12,000, 12,200, 12,300, and 12,400 rpm.

15 September 1948: Ground run 275 – A new MM&M amplifier was installed for an operational check. Ground run 276 - Checked the microsen amplifier and it was found to be satisfactory. The governor was found to be sticking very slightly. This was resolved by using lapping compound on the parts and on reassembly was found to now have freer motion. On the next engine run, the eyelids were opened at 11,500, 11,800, 11,900 and 12,000 rpm to check engine overspeed. No improvement could be discerned after having cleaned the pilot valve in the governor. The restrictor was removed from the eyelid cylinder air line on the assumption that if the eyelids were permitted to open more quickly the rpm would return to its original value more readily on the AB start. The governor acceleration rate was also increased to check its effect on engine overspeed on AB shutdown. These changes resulted in decreased overspeed characteristics but little change in the under-speed on AB starting.

15 September 1948: CV NOa(s) 9602 contract Amendment 1 was processed. This removed the requirement for simulated altitude testing of the AB from Section C, Phase I.

16 September 1948: CV notified BuAer that both engines (WE020067 and WE020069) were over the two hour limit of AB operation time. The first had 2.82 hours and the second 2.16 hours operation time. Engine disposition instructions were requested.

16 September 1948: Ground Test – The thrust stand, a Franklin cell and Cox & Stevens thrust devices were installed in series. In runs, the overspeed characteristics of the flyball governor were found not to have improved by its recent cleaning. The governor and emergency fuel pump were sent back to Westinghouse. The Cox & Stevens and Franklin thrust measuring units were returned to CV for recalibration with dead loads.

17 September 1948: Ground Test - XF6U-1 had a new governor and emergency fuel pump installed in place of the flyball governor. On the thrust stand, the first AB start was unsuccessful. A second start was made at 11,500 rpm, but the eyelid light did not illuminate so the engine was stopped. A shorted microswitch on the air cylinder was found. It did not interfere with testing and testing was resumed. The next AB start was attempted at 11,400 rpm. The AB lit off, but the eyelids did not open. Another start was made at 10,500 rpm with no difficulty. With the AB running, the throttle was advanced and AB runs made at 11,300, 11,600, 11,800, 12,000, 12,200, 12,400 and 12,500 rpm.

18 September 1948: Ground Test – XF6U-1. A preload mechanism was installed on the thrust stand to eliminate the error induced into the thrust meter readings due to deflection of the thrust stand under load. The eyelid open microswitch was repaired (broken electrical connection soldered). Faulty ignition checked. Coil from Westinghouse engine replaced the Scintilla coil and ample spark was observed. Ground run 279 in thrust stand. An AB start was attempted but the AB did not ignite. Ignition was again found inoperative. The coil input voltage was incorrect, coil reset and ignition occurred on next attempt. AB starts were made at 10,500, 11,000, and 11,500 rpm. Starts had a delay of 3 to 5 seconds after the switch was turned to the “ON" position. On shutdown, a sudden lurch was felt, very similar to the one experienced on the AB start.

20 September 1948: Contract Amendment 11 was processed. It moved the Item 9 Delivery date from being “three months after date of this amendment" to “on or before 1 February 1949."

20 September 1948: Ground Test - Full examination of the AB was made, particularly of the fuel and AB ignition. Several partially plugged fuel holes in the burner ring were found and cleared. Ignition timing of valves in the automatic control sequence was found to be correct and as designed.

22 September 1948: Ground Test. With the AB installed in the XF6U-1 the ignition of the AB was tested twenty times with the fuel shut off and ignition spark was observed to be almost instantaneous to the “ON" switch being thrown. With engine and AB removed, the rear burner ring was found to have several plugged fuel holes. Not considered enough to cause the delay in starting. The eyelid cylinder pistons were found to be sticking badly in the end fittings. The eyelids and mechanism were found to work freely. A crack was found in the nozzle ring about two inches long running circumferentially just forward of the aft nozzle section spotweld seam. Part was sent out for repair.

A general notation stated the progress of the XF6U-1 AB program was being severely hampered by a shortage of manpower due to allocation of most of the crew to the XF7U-1 project. Frequent interruptions of the balance of the crew to unload trucks and airplanes added to the delays.

29 September 1948: The first XF7U-1 airframe was flown for the first time using tailpipes on the engines instead of ABs. The flight was successful. The landing gear was left down and the cockpit canopy open during the entire flight. The maximum speed attained was approximately 210 mph IAS.

30 September 1948: The BARR reported that both WE002025 (with 25.72 AB hrs) and WE002028 (with 10.51 AB hrs) were over the 2-hr AB time for overhaul required by Experimental Engine Notice 142.

1 October 1948: CV Contract NOa(s) 9602 Amendment 2 was processed. This required all contract items to be completed by October 1948.

1 October 1948: The Ryan BARR received an order for: Twelve Solar four-strut exhaust collectors for XF7U-1; Eight thermocouples spaced 45° apart straddling the struts were required per collector (The fore and aft location was to be the same as the Westinghouse drawing); Twelve Westinghouse standard nine-thermocouple harnesses; Ninety-six thermocouples to be supplied by Solar. Pertinent drawings would be forwarded by Westinghouse. It was requested to advise if the Solar quotation was hereby changed.

2 October 1948: XF6U-1 Flight 194, Afterburner check to obtain performance and powerplant data during AB operation in automatic. At 18,000 feet at 12,000 rpm, a dive was held until 450 mph was obtained just below 13,000 feet. This was accomplished to stabilize for an AB run at 12,000 rpm at 12,000 ft. The AB was turned ON. Fuel flow increased but the AB did not light and the eyelids remained closed. Engine speed remained the same. After 10 seconds the AB was switched to OFF and the manual fuel and eyelid controls were secured. After the flight a large discrepancy in the actual amount of fuel in the tanks vs that shown on the cockpit gauges was observed. This had to be addressed to ensure the optimum amount of data would be obtained in later flights.

6 October 1948: BuAer clarified to CV that the inverters needed for the AB automatic controls incorporating the MM&M amplifier would be supplied by the Bureau.

7 October 1948: Westinghouse Experimental Engine Notice 42 required an engine overhaul after 2 hours of AB time. BuAer clarified to the BARR that the AB operating time limit on engines applied to flight engines only, not to the ground test experimental 24C engines in use at Solar. The previous allowance given to Solar of 100 hrs remained effective.

9 October 1948: XF6U-1 Flight 195, Check of AB automatic control. An AB start was attempted at 10,000 ft at 12,000 rpm and 280 mph. The electrical system failed and the start was unsuccessful. Inadequate power for radio operation indicated this failure was an airframe electrical type and the flight was discontinued.

9 October 1948: XF6U-1 Flight 196, AB starts in flight using automatic control. Six attempts all failed. Fuel flowed but AB ignition did not occur and the eyelids remained closed.

9 October 1948: XF6U-1 Flight 197, attempted AB starts at the lowest airspeed considered feasible by the pilot at this point of AB development. Attempts at 8,000 ft; engine speed 12,000, 11,000, 10,000 rpm; and airspeeds of 170 to 150 mph were unsuccessful. After landing, successful starts were obtained on the ground.

9 October 1948: The BARR notified BuAer by wire that the Solar quotation would be revised to increase cost due to increased number of thermocouples. The revised quotation would be sent when the actual costs were known.

13 October 1948: XF6U-1 Flight 198, Obtain one or more AB starts in flight. Eight were attempted, none successful. Two successful starts on the ground at 10,000 and 12,000 rpm after flight before shutting down the engine.

13 October 1948: Solar acknowledged receipt of Amendment No. 11 and pointed out that delivery of the Items for Item 9 (automatic controls) could not be met because the few controls systems available had been diverted to other Navy AB contracts where delivery was urgently required in order to complete flight test programs. Solar anticipated the four (4) Item 9 control systems would be available about January 1, 1949 and an amendment to supersede the current Amendment 11 Item 9 delivery date was requested.

14 October 1948: XF6U-1 Flight 199, Test AB with automatic control in flight. Five starts were attempted and one was successful. The first three attempts were made at 10,000 ft at 12,000, 11,000, and 10,000 rpm. The speed ranged from 305 to 322 mph. All three failed. The fourth attempt, which was successful, was made at 7,800 ft, 12,000 rpm and 350 mph. The engine speed dropped briefly to 10,650 rpm and then stabilized at 11,500 rpm. The throttle was advanced to 12,000 rpm and a climb commenced. The airspeed being maintained at 350 mph. After approximately 35 seconds the turbine out temperature reached 670-680°C (the limit being 660°C) and was still increasing at an appreciable rate. The AB was shut off with the ON/OFF switch. The engine then oversped to 13,000 rpm for approximately five seconds before the throttle was retarded. The altitude was approximately 10,300 ft. The aircraft limbed to 12,000 ft and another AB start was attempted at 12,000 rpm and 350 mph. This was unsuccessful.

15 October 1948: BuAer notified the BARR that a replacement Holley Automatic Control (governor) was not available for WE002028. The control was directed to be shipped back to the BARR at Westinghouse in Essington, PA. BuAer suggested the BARR direct that the control units on the test engines at Solar be used interchangeably to extend the engine operating time before overhaul. (This was officially authorizing cannibalization of engines for parts as needed.)

16 October 1948: XF6U-1 Flight 200, Automatic Operation of AB. The AB spark plug was reconnected after being found disconnected after last flight. Compressor inspected after overspeed on last flight. An AB start was made successfully at 7,500 ft, 350 mph and 12,000 rpm. Engine speed stabilized at 11,500 rpm and then was advanced with the throttle to 12,000 rpm. After two and a half minutes of AB operation the aircraft had climbed to 20,000 ft. Intermittent grinding noises were heard during the latter part of the climb and vibration was felt through the rudder pedals. Bearing temperatures were normal and within the limits. The aircraft was turned back to the field direction for a level run. (The balance of the flight report is missing.)

16 October 1948: XF6U-1 Flight 201, Automatic Operation of AB. The AB was successfully started at 8,000 ft, 350 mph and 12,000 rpm and a climb commenced. A cyclic (two per second) variation in thrust was noted as the climb progressed. Engine speed, turbine out temperatures, engine fuel flow and AB fuel flow all appeared to be normal. The fuel warning light (93 gal remaining) blinked intermittently and the two fuel level indicators fluctuated considerably. A climb to 14,000 ft was made to eliminate the effect of the somewhat larger elevations of the thrust line above the horizontal. The fuel warning light continued to blink intermittently. The AB was shut down and the flight ended.

20 October 1948: BuAer ordered The Solar ABs at NACA, Cleveland to be shipped back to Solar, along with their control accessories, for inspection and possible use. These were the H049000000 and H085000000 units.

21 October 1948: CV asked BuAer to authorize Solar and/or vendors to ship four sets of AB accessories in advance of delivery of the ABs. This was to permit early installation in the 1st and 3rd XF7U-1 aircraft scheduled to fly with ABs. BuAer authorized such shipments after the accessories became available after the AB acceptance testing on the two burners to be delivered on 5 November 1948 AB was completed.

29 October 1948: XF6U-1 Flight 202 – AB Climb to 30,000 ft. Before flight, a patched old-type diffuser section was installed in the AB, cracks were repaired in the airframe tail section, cracks in the shroud welded, and four MM&M thermocouples replaced. A successful AB start was made at 7,850 ft and 12,000 rpm. A combat power climb was made to 30,300 ft where the AB was shut down at the 5-minute limit of AB operation. Mild thrust fluctuations occurred during the climb. Engine operation was satisfactory. The grinding noise and/or vibration noted in the previous flight were not present.

1 November 1948: XF6U-1 Flight 203 – AB Climb to Blow-out Altitude. Automatic control was used. A successful AB start was made at 12,000 ft, 415 mph, and 12,000 rpm. The aircraft climbed to 32,500 ft where the AB blew out. The automatic controls shut off the fuel and closed the eyelids. The engine did not exceed 12,500 rpm.

1 November 1948: XF6U-1 Flight 204 - General AB test. Stabilized run at 12,000 for 4 minutes with AB operating. Attaining a stabilized run took several attempts. At 12,000 ft, 370 mph and 12,000 the AB control was turned ON. After 1-2 seconds the AB combustion ignited. Acceleration began and pulsing was observed. Engine rpm dropped after ignition below 11,000 rpm immediately after starting, then climbed back to 11,500 rpm. Turbine out temperature remained below the limit. After one minute, a shudder was felt as the aircraft passed 460 mph. This was followed by a violent shock and a nose down change of trim. All engine and AB fuel controls were turned off ASAP. The elevator trim was found to be inoperative. Stick forces could not be trimmed out but were not excessive. A chase pilot reported glide airspeed was 200 which the XF6U-1 pilot interpreted as 200 mph but the other pilot was using knots. This conflict caused the XF6U-1 pilot to overshoot the runway in a gear up landing after a slide of 2,000 ft. The pilot was uninjured.

2 November 1948: XF6U-1 BuNo 33532. Formal Report of turbine wheel failure with AB operating reported on Flight 204 on 1 November 1948. Major structural damage before and during landing. No injuries. No fire.

3 November 1948: CV Contract NOa(s) 8337 F7U-1 ABs Program. Investigation of a Pesco air driven fuel pump for AB (in lieu of electrically driven) was handicapped due to the lack of enough compressor bleed air to drive the pump from the early experimental 24C engine. Limited tests indicated such a pump would be satisfactory for use with an afterburner. An improved pump to be available for use with an AB was expected in approximately five months. Analysis of fuel flow and pressure required for the ABs showed that development and installation of a high-capacity fuel pump and control would be necessary to obtain the AB performance required to realize the performance potential of the XF7U-1 airplane. The wide range of fuel flows along with a fixed orifice type fuel injection system required high fuel pressures for low altitude operation at acceptable boost ratios. Based on that, it was clear the Solar electrical pump would be inadequate. A chart showed the calculated impact on aircraft performance if the Solar electrical pump was used.

CV found the detailed problems encountered were typical of a major power plant component development; continued fuel system improvements, along with other components such as the burner and control system, was required. The reduction of dry losses, the improvement in combustion efficiency and specific fuel consumption would require continued attention. CV strongly recommended that the Bureau establish an afterburner procurement program if it was possible to enable the modernization of the units as development continued.

9 November 1948: BuAer terminated Contract NOa(s) 5312. The damaged airframe of BuNo 33532 was found to be beyond economical repair. The first production F6U-1 under contract NOa(s) 8783 for 30 airframes would be used for further AB testing. The engine of the production F6U-1 would be the J34-WE-30A. (No AB at any test site had been run to date with this engine. It had many differences from the J34-WE-22 engines as a result of a development contract to improve performance and reliability combined with alterations to enable an AB to be attached and operated without damaging the engine.)

22 November 1948: BuAer announced the first production F6U-1 BuNo 122478 would be used for the power plant demonstration of the airframe type. This required that all phases of AB development be completed, including complete instrumentation. CV wrote that due to the earliest delivery date available to CV of a J34-WE-30A being 15 December 1948 and the first Solar ABs not being available until 11 February 1949, CV asked for a slip in production delivery of F6U-1 aircraft to begin in February 1949.

Fig. 12. Combustion Chamber Burner No. 551 Seen From Diffuser Input.	Fig. 13. Burner No. 551 Condition after 3 hr 11 min Operation, Seen From Exit Side.

Solar determined that the three ABs yet to be delivered would need diffuser and combustion section configuration changes in order to achieve maximum boost ratings.