Solar Aircraft Company, San Diego, California

Westinghouse’s latest report (A-312) indicated a thrust of the 24C-4B of 2,870 lb at 12,000 rpm using a 176 in² exhaust nozzle and BuAer thought the data were now obsolete.

31 July 1947: In his role as cognizant control officer for the NOa(s) 8203 contract, the BARR added his comments to the prior Calculations and Summary reports. He noted that Solar intended to file a report upon completion of the 24C engine test program. Additionally, he observed that the maximum thrust value Solar had reported on Figure 17 of the Summary Report was less than the 150% desired by Section C, Item 2 of the contract. The achieved thrust of 143.5% at Military corresponded to a very low combustion section friction loss in the dry condition. Overall, his opinion was that the contractor had exercised care and thoroughness in the execution of that contract phase and recommended that the combined reports be accepted as completing Contract Item 2.

Fig. 1. U.S. Navy F46 Torpedo Camera

31 July 1947: Solar reported that currently they were using two film cameras owned by the company to photograph performance data, a necessity in obtaining all the performance data in a test from remote instruments used to record the testing performance. Such an approach also protected the test cell personnel. Delays were sometimes experienced in changing camera setups, replacing film, etc. Also, functional difficulties occasioned a resulting loss of test data.

It was observed that F46 aircraft torpedo cameras were available, which were ideally suited for semi-automatic data recording. Solar requested that four of these cameras along with two standard magazines for each be made available to expedite test work on this and any other experimental Navy projects Solar might undertake.

22 August 1947: Solar responded that in order to obtain the most conclusive data for the final 24C afterburner design consideration, the latest model of the 24C should be used in testing. Since the 24C-4A and 24C-4B only differed in small mechanical aspects, they requested that the 24C-4A engine be sent to them as soon as possible. The 24C-2 they currently had on hand differed considerably from the latest models.

9 September 1947: BuAer ordered XJ34-WE-4A Serial WE002025 be shipped to the Ryan BARR to be used on the Solar contract NOa(s) 8203.

16 September 1947: Contract Amendment 5 was processed. This changed the delivery schedule for the Item 3 design data and drawings from 12 to 16 months from the date of the contract. The delivery schedule on the Item 7 final summary report was also changed from 12 to 16 months from the date of the contract.

22 September 1947: The BARR concurred with and forwarded a report from Solar reporting on the failure of 24C-2 WE002005 after only four hours of total operation during an AB run. The loss was not attributed to the AB operation (its compressor suffered a blade fatigue failure). The time lost due to the failure would prevent Solar from meeting the contract date of October 22, 1947. A delivery of an X24C-4A was expected shortly. A one month contract extension was likely needed. The overall contract was estimated to be 70% complete at the time of the engine failure.

6 October 1947: Progress Report for September 1947

(No progress reports for July and August were found in the files. Given the engine failure, actual date unknown, the work of installing and starting testing on the 24C-4A likely occurred during much of that time.)

Fig. 2. X24C-4A with AB tailpipe using 15" nozzle mounted on test carriage.

Construction of the first AB for the 24C was underway and was about 50% complete. Limited testing was accomplished using the X24C-4A and the results largely verified the results obtained using the X24C-2 earlier. A boost of 45% was attained with smooth combustion on the X24C-4A, which had been previously calibrated in normal tailpipe tests using the X24C-2. Thrust loss dry on the X24C-4A was about 4.5%. This loss was expected to drop to about 3.5% with development.

7 October 1947: CV proposed an improved version of the F6U-1 that would use the Solar AB for improved performance. This was their model V-359. Various charts were included in their brochure, but the improvement in high altitude speed and a good balance trade-off for combat radius was exhibited. AB boost of 30% was assumed and the Solar AB chosen as it took up the most space in the airframe, meaning the Westinghouse and Ryan units under development would both fit as fallback options. First flight was estimated to be 1 March 1948 if authorization for the airframe changes was made immediately. On 3 November 1947 BuAer responded saying the adding of the AB to offset the acknowledged poor thrust loading of the XF6U-1 appeared to be a good idea, but the quoted price to design and construct the modified airframe was too high at the quoted $485,132.00. Annotations on the memo recommended proceeding if a $300,000.00 price could be agreed. Permission must have been granted as on 17 November 1947 a Consolidated Vultee (CV) request of GFE for the afterburner project was approved. This was all proceeding under contract NOa(s) 5312. Installation completion was scheduled for 7 January 1948.

BuAer issued a change order to Contract NOa(s) 5312 on 22 June 1948 for $485,132.00 to modify BuNo 33532 with an afterburner. Empty weight increase was 1,103.2 lb which included 494.7 lb of ballast for balance.

13 October 1947: The BARR recommended to BuAer that, due to unavailability of special high-temperature materials, the delays caused by equipment failures, unavailability of test engine replacement with the latest versions, and the changes required by the latest engine version to be tested, that the Item 5 delivery date of the four (4) 24C tailpipes be extended to December 28, 1947.

Fig. 6. Solar automatic AB control schematic taken from Patent 2,737,015 filed 15 September 1950. It was likely a development of the first version referenced in the memo below.

22 October 1947: Another BARR memo pointed out to BuAer that Ryan was working to a delivery date for their single tailpipe delivery of 8 January 1948 not in November as referenced in an earlier BuAer memo.  Also, the contract with Solar did not require Solar to furnish all necessary component parts for their AB on delivery, but Ryan was required to do so. Solar was planning to recommend changing the Item 5 language to be the same as Ryan’s contract regarding “necessary component parts”.

24 October 1947: A BARR general update on AB development mentioned that Ryan’s engineers were not certain of completing their development by 8 January 1948 and were not certain if additional funds would be needed. The Ryan Director of Engineering believed that BuAer was going to eliminate the requirement for endurance testing. Development was to stop when funds ran out. He asked for BuAer confirmation of Ryan’s information.

28 October 1947: Contract Amendment 7 was put in process by BuAer. In the main, it would extend the delivery date of Item 5’s four 24C tailpipes by two months to December 28, 1947. It did not include any changes related to automatic AB controls.

3 November 1947: BuAer confirmed Ryan’s obligation to provide an example of their tailpipe suitable for XF7U-1 installation including all items.  The production type should be capable of meeting all of the specifications including successfully completing the endurance requirements. Statements regarding the elimination of endurance testing were entirely in error. Such testing was essential in completely evaluating an AB prior to installation in an airframe. A standby 24C engine was being shipped to support testing. Solar’s proposal for conducting the AB endurance test program for $16,495.00 was being processed for contract Amendment on Contract NOa(s) 8203. The amendment backup shows $4,000.00 was included for four electronic controls to be delivered three months from notification of approval to proceed.

5 November 1947: The BARR reported that Ryan had received a Letter of Intent for AB production from CV and had sent a proposal for same to McDonnell Aircraft Corporation. These were considered commercial, not military, contracts. Both Solar and Ryan wished to use the Navy GFE test engines and test facilities then in use on the production contracts. The BARR supported such use as long as all operating expenses of the test facilities were borne by the contractor and that repair and replacement of GFE due to negligence by the contractor were borne by the contractor as well.

7 November 1947: BuAer notified the BARR by wire that action was being taken to extend the contract delivery completion date to 28 December 1947.

12 November 1947: The BARR reported to BuAer that recent enclosures sent indicated the development was approaching a final satisfactory afterburner configuration. Smooth combustion was being obtained and his office regarded rough burning and vibration as one of the most difficult design considerations to overcome. The figures indicated approximately 36% thrust augmentation. The request for photographs of the main exhaust casing inner cone design could not be complied with as it was installed before the photographs could be taken. The design incorporated four supporting struts and was of slightly heavier gauge material and had thus far shown promise of being superior to the Westinghouse design.

14 November 1947: The BARR reported on program progress. He noted that with the Solar proposal for the afterburner endurance test, they had asked for a six week contract extension. His office now estimated 15 February (1948) as the date when both companies should complete tested afterburners.

19 November 1947: The BARR reported that XJ34-WE-16 (an X24C-4) WE002025 used for testing had 14.73 hours on it since last buildup of which 1.46 was at Military speed. If the six week contract extension request was approved it was requested that the current operating limit of 50 total hours be raised to 100 hours for the afterburner endurance testing. This request was identical to the one granted to WE002024 at Ryan for the same purpose.

21 November 1947: The BuAer Power Plant Division asked the Photograph Material Division to expedite delivery of four (4) F46 aircraft torpedo cameras to Solar Aircraft. They were urgently needed to complete the afterburner development program.

28 November 1947: The operating time limit on WE002025 was raised by BuAer to 100 hours.

8 December 1947: The BARR confirmed to BuAer that Solar had indicated they intended to furnish all necessary accessories with afterburners delivered under the contract. Other conversations that had occurred with members of BuAer were concerned with types and/or manufacturers of accessories to be furnished with the afterburner.

9 December 1947: The BARR asked for verification that BuAer desired that two of the four Solar ABs be completed as expeditiously as possible in order that they be ready for wind tunnel tests not later than 15 January, and additionally that in order to expedite delivery, acceptance endurance test requirements may be waived by his office. If the latter was verified, the BARR asked for authority to wave two of the four Solar units and also requested disposition instructions for the first two ABs.

12 December 1947: BuAer authorized the shipment of two different model Pressure Transmitters and one Pressure Indicator to CV for support of the AB program on the XF6U-1.

15 December 1947: In response to BuAer’s request for AB controls data, Solar informed them that all present AB work to date had been done with a manual fuel flow control and a variable nozzle. No automatic systems had been tested. The current engine controls worked well when the AB was manually controlled. They stated they planned to install an electronic temperature limiter system that would regulate afterburner fuel flow in order to maintain turbine discharge conditions while the AB was in operation. The AB was expected to be utilized where emergency power was needed, such as in a carrier wave-off, etc., the AB would be called upon to provide added boost almost immediately. In the contemplated arrangement, engine speed would be controlled by the 24C all-speed governor, which might have excessive time lag in compensating speed with sudden ignition of the afterburner. Such a condition would be aggravated due to the fact that the variable nozzle must be opened prior to ignition. This would cause the engine to overspeed, calling for reduced fuel flow. The instant ignition occurred, tailpipe pressures would rise, tending to suddenly reduce the pressure drop across the turbine, which would then require a sudden increase in fuel flow to offset the drop in turbine speed. Whether such rapid change in events could be adequately compensated by the governor and the rotating inertia of the system could only be left to speculation. The AB control system to be tested would be so arranged that its response and time constants could be easily adjusted in anticipation of stability problems. When sufficient tests were complete and definite conclusions could be made, the requested information would be forwarded to BuAer.

23 December 1947: BuAer reminded the BARR that they had been finalizing NACA testing at the Cleveland wind tunnel to begin 1 February 1948. They desired to get testing underway as soon as the wind tunnel became available. It was requested that the latest specifications and installation drawings on both the Ryan and Solar afterburners scheduled for delivery under the contracts be sent to NACA – Flight Propulsion Research Laboratory, Cleveland, Ohio, attention Mr. A. Silverstein.

29 December 1947: Solar was reported as still being in the process of fabricating the four afterburners due to be delivered. The first three were estimated to be ready on or about 15 January. The various amendments still in process for NOa(s) 8203 had not yet been received.

6 January 1948: Solar reported that their best estimate was that the earliest delivery of two tailpipes to the BARR would be January 19, 1948.  The fuel pump and control system valve deliveries were uncertain. It was felt that testing in the wind tunnel did not necessarily require those two parts and the parts could be sent after shipment of the tailpipes. The installation drawings and other specifications were being prepared and would be forwarded to the BARR during the week of January 5.

6 January 1948: BuAer sent a memo stating they were reviewing Solar’s proposals for added AB tests and the furnishing of automatic AB electronic controls.  It was noted the cost breakdown did not include mention of a fee. Was it Solar’s intention to do such additional work on a no-fee basis? In addition, they requested clarification of the unit price per system of the automatic controls of $4,000.00. A standard cost breakdown was requested, or if the system was completely purchased by Solar, any information available including fee consideration, if any.

8 January 1948: A defective governor (cracked case) from WE002025 was ordered returned to Holley and a replacement ordered shipped to the BARR.

9 January 1948: Three prints of Solar drawings of the Model A-104 Afterburner Assembly, Fuel Pump, Ignition Unit and Solenoid Air Valve were sent to the BARR, responding to the request for drawings to be sent to NACA Cleveland. Two additional drawings on the Lead, High Tension and Air Fitting would be sent in another week. The construction and installation work could be almost completed without them.  The BARR forwarded the drawings on 12 January and would forward additional data when received.

15 January 1948: The Barr reported that delay in procuring critical material needed for fabricating the Solar ABs had delayed manufacture by approximately a week.  The first two SOLAR ABs were estimated to be ready for shipment on 26 January by rail express. They could be expected to reach Cleveland on 2 February. The Solar test engine would not have sufficient operating time to complete endurance tests even though the operating time limit had been extended to 100 hours. It was estimated it would be about 10 hours short.

16 January 1948: The BARR confirmed Solar was expected to ship to NACA two ABs on or about 26 January. Current tests were for the purpose of improving operational characteristics such as combustion smoothness, reduction or losses, ease of starting afterburning, etc. The endurance tests were scheduled for February.

21 January 1948: Engine WE002028 was shipped from Douglas to the BARR to support testing. This brought the total number of engines to three for the contracts of Ryan and Solar. No 24C-4B engines were available. Should additional engines be required, AB testing would be considerably delayed.

23 January 1948: The BARR notified BuAer that both Solar and Ryan were producing ABs for CV for engines to be used in Navy aircraft. He asked for authorization to allow both companies to retain present test equipment, including engines at both plants after the completion of their contracts. This was to allow testing other afterburners that might be produced for Navy or Army aircraft.

28 January 1948: The BARR requested BuAer to authorize continuing work under the contract without delays while the amendment covering endurance testing was processed. Solar indicated a work stoppage might be necessary unless amendments covering endurance testing and automatic control systems were received shortly.

228 January 1948: The BARR reported that the first of the four production ABs was not accepted. To provide an AB for the NACA wind tunnel test, the Solar development AB was successfully tested and accepted on 26 January and shipped to NACA 27 January. The AB was almost identical to the final Solar design, and even though it had considerable usage, its performance was good and its expected life still considered to be expensive. No photographic data was available on the acceptance test of the development unit. It was accepted in addition to the four contractual units, in replacement for one of them. The first unit rejection was because of the failure of an attempted improvement over the development unit. Solar was confident the issue could be corrected “in due time”, later expressing confidence the matter would be resolved within the three weeks before the agreed date below. NACA had verbally approved shipment of the second AB up to three weeks from 28 January 1947. The second unit would be retested and shipped ASAP once corrections had been made. Solar requested permission to ship their automatic control unit, if ready, with the second AB unit. The BARR reported his observation of its preliminary operation on the AB and it appeared to function very well.

30 January 1948: Most of the drawings for the Model A-103 AB were sent to CV by Solar. Some drawings were bound to change. Manning, Maxwell, and Moore had not given an up-to-date outline of their amplifier. The fuel control amplifier would have revised wiring to transmit a full-open signal to the valve on shutdown. The Fuel control would change to show a slight space addition and connections for the rate of change feedback potentiometer. The ignitor plug needed to be fully shielded against the temperatures at its installation location but such shielding had not yet been successfully produced. An unshielded design would be provided in the interim. The electrical loads were listed for wiring and accessory selection.

2 February 1948: The British Joint Services Mission in Washington asked that information on the Solar AB be sent to the British Air Ministry, including any development and flight testing that might have taken place on it.

3 February 1948: BuAer granted permission to use the GFE 24C engines at Solar and Ryan for testing a limited number production type ABs which supported a particular Army or Navy engine or airplane program. All operating expenses of the test facilities and the repair and replacement of GFE due to the contractor’s negligence would be born by the respective contractor. Due to availability of the 24C being critical, it would not be possible to allocate any additional 24C engines as test engines. Special care should be exercised during all testing so that the current contracts could be fulfilled. The BARR was to supervise all testing and give approval of planned test programs prior to commencement of testing.

4 February 1948: The cost justification for Amendment 8 was processed. This covered the 24C tailpipe endurance testing ($16,495.00) and four electronic controls ($16,000.00) for a total of $32,495.00. One key consideration was that this amendment would bring the Ryan and Solar work into close conformity so that the final units delivered could be evaluated on the same terms by BuAer. A components breakdown for the automatic control was included.

5 February 1948: BuAer approved Solar’s automatic fuel controller, if capable of satisfactory operation, on the second Solar AB scheduled for delivery to NACA about 17 February. In addition, BuAer concurred with the BARR’s decision to accept the Solar development AB since no contractual ABs were available. This would allow NACA to commence their investigation as scheduled.

5 February 1948: In response to the BARR’s query, BuAer ordered the BARR to retain the I-16 engine (serial 000247) at his location until the Maintenance Division issued disposition instructions. This was issued as GFE for contract NOa(s) 8216 (unknown) and transferred to NOa(s) 8203 for AB testing work.

6 February 1948: Progress Report for January 1948

(Note: No progress reports for November or December 1947 were found.)

Item 3 for design of 24C tailpipe was 97% complete. Item 4 for development and test of installation on a 24C was 95% complete. Tailpipe H049000000 was shipped to NACA for altitude testing after completion of the required one hour test schedule. The H085000000 afterburner that had been intended to be shipped to NACA was delayed due to difficulties experienced in its acceptance test. (The defects were corrected and the AB, now an H096000000, was shipped to NACA for testing after a one hour acceptance test.)

Further testing on the burner fuel injector was done in an effort to reduce circumferential skin temperature variations and changes were made to increase the design injection pressure with the view toward improving altitude combustion performance. Testing with a 28V vibrator type injection unit produced equally satisfactory ignition to the standard 110 VAC primary transformer ignitor. Tests using fixed throttle settings with a constant AB jet area were done to determine the variation in basic engine conditions with afterburner fuel rate to aid in analyzing the engine-afterburner control problem. Tests required that the AB fuel rate was increased appreciably beyond the normal rate in order to provide sufficient spread in the operating band for control analysis purposes.

Fig. 7. Afterburner Model H085000000 Endurance Test.

The H085000000 AB was installed and given a brief check run. Combustion was smooth and 12,000 rpm ignition improved over the H049000000 burner, a slight periodic tailpipe surge was noted. This was a low frequency surge that grew progressively in amplitude early in the acceptance test. Testing was stopped and tailpipe skin warpage was found of sufficient magnitude to warrant discontinuing the tests until circumferential skin temperature variations could be eliminated. Changes to the clam shell hinge pin support were also to be made based on early test results. The unit would be shipped to NACA if the wind tunnel testing schedule permitted. Correction efforts continued on H085000000.

H049000000 when shipped to NACA had been subjected to over 40 AB cycles and had accumulated approximately 6 hours of burning.

The H049000000 AB mating flange was fabricated to mate with the 24C-4A serial WE002025 engine and when mated to a 24C-4B engine the plane of the trunnion supports would be 3.75° of rotation off the horizontal because the flange had been rotated one half of a hole spacing between the two engine models. The first H085000000 was expected to complete the acceptance test on or before 15 February.

9 February 1948: BuAer notified the BARR that Amendment 8 had been issued to the contract. This covered the cost and fees for the endurance testing and four automatic control systems. The BARR was instructed to tell Solar to keep working.

11 February 1948: Solar provided a full set of drawings for CV’s clearance studies. No interference issued had been identified during a recent review. Parts were being produced to the drawings. Safety ties had been added across the ball joint and the clamp band joint. The eyelid actuating system now had two parallel actuating cables for safety. The load on the ball joint necessary to move the ball joint was determined by running the engine at normal power with the AB not operating. It was found that 110 pounds of force was required. The eyelid activation cylinders of 2” diameter would only provide at 25% margin of safety over the forces required for activation at speed. A safety excess of 100% had been requested and larger cylinders would be provided later, but the initial cylinders would allow initial testing to start. An alternate method of eyelid activation was being studied. This was a scissor type acting across the eyelid hinge point. Such an arrangement would place the force of activation where the eyelids split, preventing the nozzle from gapping due to distortion or warpage dynamic forces. Such distortion was a continuing problem with the current design.

18 February 1948: Solar reported that they planned to use the test facilities to test one of two ABs that were to be delivered to CV. The tests were simple performance calibrations in which the variable nozzle would be trimmed in a non-burning position. Both the non-burning and AB operation performance would be recorded. It was expected the functional operating of the control system and accessories would also be checked provided the equipment was available at that time. Total 24C operation time was estimated at one to two hours. Approval was requested for the tests to be conducted the week of March 1, 1948.

23 February 1948: CV requested procurement information from BuAer on the tailpipes to be supplied for the XF7U-1 airframes in lieu of afterburners. It was becoming urgent for the tailpipes to be delivered for installation into the airframes.

24 February 1948: The BARR reported the acceptance of the second Solar AB on 21 February. The air supply from the engine compressor was found insufficient to operate the variable nozzle and an outside air source was used. Solar stated either the size or number of actuating cylinders would be incorporated to correct the problem. The automatic control system tests indicated the necessity for an over-speed governor for jet engines with ABs to prevent exceeding the maximum allowed rpm during the shutdown phase and in case of blowout.

1 March 1948: Solar notified BuAer that Robert E. Day and Frederick J. Hill had filed a patent application for the Solar designed AB that day. This patent was granted on 6 March 1956 as Patent Number 2,737,016. Patent Number 2,701,444 (Robert E. Day), which covered the location and functions of the ignitor plugs in the AB was referenced, but the patent office shows this as filed on 26 January 1950 as 2,701,444A. Original filing date is unknown.

3 March 1948 (approx.): The BARR asked for an acknowledgement of his action request on 6 January 1948 for parts for engine WE002025. None had been received. Written note attached states the BARR was not serializing his Special Action Requests for GFE or putting dates on them, they were being improperly handled and hard to trace. He was requested to begin serializing, dating all requests, and including his position title in the requests.

3 March 1948: BuAer approved the AB installation drawings for the XF6U-1 and noted the approval only applied to the XF6U-1 having an AB installation.

8 March 1948: Engine WE002028, an X24C-4A, was shipped to the BARR.

10 March 1948: BuAer reported the requested parts were found to have been shipped to the Bureau of Aeronautics Representative, San Diego instead of the BARR, Ryan Aeronautical Company, San Diego. BuAer directed that all future spare parts for the experimental engines were to be directed to the Experimental Engine Branch, Power Plant Division of BuAer. The use of the “Special Action Request for GFE” form should be discontinued from use in making XJ34‑WE spare parts requests.

11 March 1948: CV requested flight release authorization of XF6U-1 BuNo 33532 for flight test with an afterburner. All stress calculations and changes made to the airframe for the installation had been complied with and provided to BuAer.

19 March 1948: BuAer asked the BARR to provide four copies of drawing CV6-300002 “Afterburner Assembly – Power Plant – Removable Model J34-WE-30” for use in coordination of F6U AB specification.

22 March 1948: Contract Amendment 8 was issued and accepted. This covered the endurance testing and four electronic control units as Section A Items 8 and 9.

23 March 1948: A request was made for a spare solenoid contactor for the 24C-4A WE002025 engine.

25 March 1948: The first flight of an AB in a Navy aircraft was made. A Solar A-103 AB was installed on Flight 171 of XF6U-1, BuNo 33532 but not operated during the flight. This was a shakedown flight of the modified airframe and various engine control issues were noted, the governor in particular not operating well. Acceleration was very slow over the entire range. A moderate rumbling noise was noted which seemed to come from aft of the engine. The rumbling increased moderately with increase in speed or power. No associated airframe structure vibrated to accompany the noise. The engine was noted to be rougher between 9,000 to 11,500 rpm compared to other 24C-4B engines previously flown.

1 April 1948: BuAer advised the BARR that AB H049000000 was being returned at the completion of testing of the H08500000 at NACA in Cleveland. Until then, it was the backup unit during testing. After its return the desired control accessories could be removed so they could be installed on one of the four (4) afterburners scheduled for delivery under the control. Based on the NACA rate of progress, the unit might be anticipated to be returned to Solar about 1 May.

2 April 1948: Flight 174 of BuNo 33532 occurred and the AB was operated at a low fuel flow for the first time in flight. Combustion appeared to be somewhat irregular, imparting a mild rumbling noise with only slight vibration. Operation was for about 3 minutes in duration before the AB was shut down. Engine speed was 10,500 rpm and a level altitude of 12,000 feet used during the AB operation. The pilot noted the speed increase was quite apparent.

5 April 1948: XF6U-1 Flight 175 was conducted. The AB fuel flow was preset to 3,600 lb/hr. At 12,000 feet, 11,000 rpm was used to establish a turbine out pressure value for balancing the cycle with the AB running. Power was reduced to 10,500 rpm and AB ignition triggered. Start was normal but appeared to take 1-2 seconds longer than on the ground in testing. Engine rpm was increased to 11,000 and AB fuel flow increased in an attempt to balance the cycle. This was not achieved due to constant speed increase during the 4.5 minute AB operation. The AB fuel flow had been increased to 4,000 lb/hr during the run. Combustion had been satisfactory during the run and acceleration was quite smooth. Fuel flow control for the AB was not sufficiently positive for anything other than experimental operation.

10 April 1948: XF6U-1 Flight 178 was conducted. AB fuel flow was 4,100 lb/hr during a four minute level run at 12,000 feet using 11,000 rpm. Throttle adjustments were required to compensate for governor variations due to changes in ram and altitude. Variations of 200 rpm occurred during the first minute of the run and had to be manually adjusted. In the last three minutes a variation of 50 rpm was observed.

16 April 1948: BuAer responded to Solar’s 5 February request for electrical system items for testing and informed them that they were not available from GFE stocks. It was suggested they procure them on the open market as any accessories were needed.

The contract cost would increase by $80,610 including the fixed fee. The amendment would provide for a revised overhead rate of 207% on direct manufacturing labor and 135% on engineering labor both effective from the date of the amendment. The amendment would add the standard Bureau of Aeronautics copyright clause. The amendment would be prepared and mailed shortly. BuAer asked that Solar proceed with the work based on the understanding of the above description of the elements of the planned amendment being prepared. The 70 hour service test was to get underway as soon as test facilities were available for operation. An exhaust muffler was being installed to reduce the noise level in the surrounding residential areas. The muffler was complete except for the concrete hardening sufficiently and was anticipated to be ready by April 12. (Note: The need for Amendment 9 had to have been triggered based on the results of the NACA testing. The early results must have been sent to BuAer and hence to Solar. The full report appeared in July, but we’ll take it up here.)

16 April 1948: Progress Report for March 1948

This reported the construction of the four production ABs that had been delayed by material defects in piping but overall were 90% complete. Final construction of the last two units was underway consisting primarily of converting them to the H096000000. At that point, the altitude testing in Cleveland had not yet begun. The 70 hour endurance test was to get underway as soon as test facilities were available for operation. This was to be conducted as part of contract NOa(s) 10023 (not found) during the combustion roughness investigation.

Early testing experienced great difficulty with afterburner ignition. Starts were attempted at engine speeds from 8,500 to 11,000 rpm and altitudes from 7,000 to 20,000 feet with flight Mach numbers of 0.0 to 0.8. Various combinations were tried without any consistently successful starting technique being established. No starts were obtained at altitudes greater than 8,000 to 9000 feet and only rarely at engine speeds over 9,500 rpm.

A modification was made to the burner that enabled successful ignition on about three of four attempted starts. A clip of about 2" wide was attached to the flame holder and bent around the fuel manifold to form a U-shaped sheltered zone centered about the spark plug between the fuel manifold and the flame holder. Attached to the downstream face of the flame holder was a box about 2" square by 1.5" long closed on the four sides and open on the upstream and downstream ends. This formed a sheltered zone downstream of the flameholders.

The cooling jackets warped and buckled at about 3-4 hours into the investigation. These were straightened and smoothed out and testing continuing until the failure of the flame holder at about 81 hours of engine operation and 12.25 hours of AB operation. Severe cracks were found in the outer flame holder and supporting members with complete separation of the flame holder at three points. A segment of the flameholder was lost and the condition of the metal was such that prevented satisfactory repairs. At the point of shutdown, the cooling jackets were found to be warped and buckled again.

19 April 1948: Engine modification kits needed to comply with Westinghouse Experimental Engine Notice No. 33 (not located) were requested for engines serial WE002017, WE002025, and WE002028.

(NOTE: Since mid-1947, Westinghouse had turned its attention to getting the J34 into production. All 24C engines in use for AB development were experimental in nature and all differed slightly from each other. Obtaining parts for these engines was becoming an ongoing increasingly severe problem. The airframe contractors’ demands for the first production version (J34-WE-22) meant few could be spared for development programs and the experimental versions remained in use far longer than anyone had anticipated or planned. In some cases, BuAer had to instruct the experimental engine users to seek various parts, such as fuel filters, on the open market due to lack of availability in the BuAer inventories.)

21 April 1948: The BARR passed on Solar’s request for an Aircraft Drift Sight No. 88-S-90 as GFE to be used to view AB burning from the rear through a recently installed muffler on the Solar Jet Test Stand. The sight was ordered shipped on 4 May.

22 April 1948: The BARR asked BuAer if the Item 8 statement in the latest Amendment stating the completion date was 18 months from the date of the amendment could be interpreted as an authorization for the Cost Inspector to pay costs subsequent to the original completion data of 28 December 1947? Clarification was requested. BuAer responded on 3 May stating that since Item 8 had expanded the cost of the contract, the Cost Inspector would be authorized to approve costs relating to Item 8 up to the new completion date.

28 April 1948: BuAer notified the BARR that the CV AB was to be at the Cleveland laboratory by May 5 to prevent delay in the testing program. Necessary drawings and specification should be forwarded immediately.

29 April 1948: The Assistant Chief for Design & Engineering sent a memo to the Chief of BuAer regarding the performance characteristics of the current Navy fighters and stated that they appeared to be inferior to the USAF fighters and presumably foreign bombers going into service in 1948. The Soviet “PE6” (believed to be the Ilyushin Il-28. – Author) was faster at altitude and the experimental Boeing XB‑47 was proving to also be much faster at altitude. Foreign fighters might also, by extension, be faster. The performance gap needed to be closed and the phenomenal performance expected from the F7U-1 airplane should fill the need as the contractor’s estimated performance included a maximum speed (Vmax @ S.L.) of 623 knots and a rate of climb at S.L. of 29,900 fpm. The design was the first to include afterburners. First flight was estimated to be 1 September 1948. He suggested the funds that were then set aside for additional F6U-1s be diverted to an early production order for F7U‑1s since this was a far more significant airplane than the additional F6U-1s. The additional F6U-1 order was in place as a stopgap to keep the CV production line busy until the F7U-1 entered production. The effort to get a higher performance airframe into early production was compared to similar actions already taken regarding the early production orders for the F9F-2, F9F-3, B-45, P-86, P-86-C; and AJ-1. (This memo, if acted upon, meant the Navy afterburner development programs would need to deliver an acceptable solution for the F7U-1 to meet its performance estimates. – Author)

4 May 1948: At Solar's request, payment of the full amount of the fixed fee covering the first seven Items on the original contract were approved even though Items 8 and 9 remained to be concluded. The funds for this came from the 1946 appropriation which would expire on 30 June 1948. To accomplish such a payment, an amendment to the contract would be necessary on an expedited basis.

10 May 1948: BuAer extended the allowable operating time limit on engine WE002025 to 100 total hours provided the inspection procedures set forth in a memo “Extension of Overhaul Period to 100 Total Operating Hours, Model XJ34-WE-16 (X24C-4B) Westinghouse Jet Engine” were observed. On 19 April, the BARR had asked for a similar extension on WE002028 as it would be needed for the 70 hour AB endurance test in the near future.

12 May 1948: Progress Report for April 1948

Solar reported that Item 5 was 97% complete except for finishing work required on the burner sections and nozzle actuating systems on tailpipes No. 3 and 4. Both were expected to be ready for acceptance testing in May.

Engine WE002025 failed its 50 hour inspection due to oil leaks in the compressor section that were leaving black streaks on the turbine guide vanes and turbine blades. Due to the difficulty of repairing the oil system, WE002028 was substituted on the test stand for the endurance test program. (Another memo at CV states this test was being charged to a CV contract NOa(s) 9642.)

Afterburner No. 2 was installed on WE002028 and the engine was recalibrated. Thrust loss over the standard tailpipe was found to be 7.77%. Solar’s thoughts were that “most of the component losses are so low that they fall within the range of best measurement accuracy common to jet engine practice.” Although they were higher than expected, it was believed that they could be reduced substantially through further refinement.

14 May 1948: BuAer had notified CV that the inverter requested by CV for the AB was obsolete and they needed more information to find a suitable substitute. CV responded with the requirements: 115+/-5 VAC; 400+/-10% cycles; 60 watts; single phase; input power to the inverter of 24 VDC.

19 May 1948: With actual fully tested production ABs nowhere on the horizon, CV requested BuAer provide compatible F7U-1 configuration standard tailpipes for the 24C engines to allow early flight testing of the XF7U-1 when the airframe was ready. Solar got drawn into this as the external size and shape of the tailpipe would be identical to the AB under development except for fuel attachment points, electrical connections, the heat shield and AB nozzle lids and controls. (Note: Up until now, BuAer continued to refer confusingly to afterburners as tailpipes interchangeably, sometimes in the same document. To reduce any future confusion, henceforth the use of the word “tailpipe” will refer to a plain (non-AB) exhaust pipe from the turbine nozzle flange to the exit from the airframe with a fixed size nozzle. – Author)

Contract NOa(s) 9642 was put in place with Solar to order tailpipes for the XF7U-1 airframes. The first two were to be built as H044000000 with Change A. The change package included a ball joint, a removable aft end, an increase in length and a change in the trunnion mount location. The first two tailpipes built to the H044000000 design, but not including the ball joint or removable end section called for in Change A, were to be delivered in 30 days. Delays of 60‑90 days occurred due to design changes. CV stated they had to have the ball joint but didn’t need the removal tip nozzle. Two tailpipes would be needed by 1 July 1948 at the latest. CV added that the tooling for the XF6U-1 afterburners could be used. The slight taper in that section and the performance penalty that would be incurred would be acceptable. Solar had agreed with CV that two tailpipes accordingly could be delivered on or before 18 June 1948. CV included a supporting rationale for their insistence on the ball joint, stating that the flexible joint of the bellows type with a ring stop on the standard H044000000 pipe allowed tailpipe tension to be transmitted to the engine at one point, imparting an unsupportable bending moment on the attaching flange. Westinghouse agreed with CV on the matter.

24 May 1948: CV notified BuAer they found it necessary to add insulation to some of the critical frames, bulkheads and fittings in the aft section of the XF7U-1 to prevent high temperatures from the AB.

24 May 1948: The BARR requested Aviation Supply send him one starter motor for a J34-WE engine. The specific engine needing it was not mentioned.

26 May 1948: Solar representatives at NACA Cleveland had only been able to observe the AB testing and did not obtain any actual performance data while there. In view of Solar’s contracts for ABs for the Navy and other aircraft companies, they requested BuAer authorize NACA to furnish Solar with any preliminary performance data as soon as possible. BuAer sent a request to NACA to release the data to Solar on 4 June 1948.

4 June 1948: Contract Amendment 10 was approved. For Items 1 through 7 of the Contract, it raised the total price of these items to $285,318.96. This covered anticipated expenditures and provided for a change in the time of delivery of Item 5. Item 5 was changed to require the four (4) ABs to be delivered not later than twenty-two (22) months from contract date.

10 June 1948: CV urgently needed engines with quick disconnect clamps to complete a tailpipe installation on the XF7U-1. They asked for a change request on their contract to cover fabrication of parts necessary to convert the standard bolted flange to a quick disconnect flange.

22 June 1948: A copy of Maintenance Change Request 36, which covered the installation of the AB in the XF6U-1, listed the following changes to the guaranteed weight and performance of the airframe. Weight +1,103.2 lb (494.7 lb ballast). Vmax decrease of 14 knots at Military thrust and 35 knots at Normal thrust. Service Ceiling decrease of 4,200 feet. Stalling speed, power off, increased by 4.9 knots.

25 June 1948: The BARR was instructed to hold ABs 2 and 3 after acceptance until the conclusion of the 70 hour endurance test. Disposition instructions would be sent at that time. In view of the rough AB operation whenever trying to attain thrust augmentation in the 35-38% range, Solar was planning to conduct the 70 hour endurance test at a reduced value of augmentation. BuAer did not approve of this due to the desire to evaluate the Solar AB at the design conditions. Additional investigations should be done to identify the cause of the sudden roughness before starting the endurance testing. The BuAer was to be kept informed of all testing and results to determine whether the endurance testing should be started.

28 June 1948: More GFE parts were requested to replace worn parts in WE002028. These were to be standby parts to support testing. It was noted that turbine seal strips had rubbed five times so far on the contract and been reported each time. Disposition instructions for the damaged parts were requested.

30 June 1948: A request went to Solar for a proposal and estimated cost for twelve (12) ABs suitable for operation with the J34-WE-22 in the XF7U-1 aircraft. (The first production version of the J34.) The ABs were to be to the same specification as the model for F6U-1 except for two items (not specified). Maximum augmentation had to be at least 40%. Delivery was to be: October – 2; November – 4 and December – 6. A cost breakdown of the first two units was requested to be included.

1 July 1948: Progress Report for June 1948

Contract Items 8, 9 and 10 were about 70% completed with delivery expected in about six weeks.

Contract Item 8: The endurance test program was delayed to allow for completion of remaining acceptance tests. Damage to engine found at 18.88 hours since last assembly. Second stage diaphragm and turbine wheel damaged by contact of mating surfaces. The casing assembly was replaced. All the repairs were done by Westinghouse representative. Additional repairs were done to the jet exhaust silencer on the test bed when several sections of the inner wall were replaced by heavier gauge material. The preparation of the test area for the altitude test stand required relocation of the control room. This added to the delays of the start of the 70 hour endurance test.

Contract Item 10: A design study and design drawings of a jet diffuser suitable for simulating altitude pressures at the discharge during afterburning were completed. Fabrication and installation were 50% complete.

6 July 1948: XF6U-1 with AB installed was flown after various modifications to the airframe had been made. The AB was not operated.

8 July 1948: BuAer Power Plant Division notified the Production Division that CV recommended the Solar AB be procured for the F6U-1 and they agreed with the provision that the decision was wholly agreeable to the Fighter Design Branch.

9 July 1948: CV wrote BuAer pointing out that no afterburners had been received for the XF7U‑1. First flights were anticipated to commence on or about 15 August. Flight tests requiring the ABs would commence on or about 1 October 1948. The available data indicated that the Solar unit was superior to the Ryan design. Procurement of Solar ABs for the aircraft was requested. Two ABs should be delivered on or before 1 October 1948 and two per month until a total of 12 had been delivered. For the XF6U-1, it was noted those ABs were being designed to a lower boost level of 30 percent and were expected to perform better than that experienced with the unit sent to NACA for wind tunnel testing. The J34-WE-22 engines specified for the aircraft did not have strong exhaust nozzle casings and quick disconnect flanges for attaching the ABs.  A Solar exhaust nozzle casing H070000000 was requested to be procured for each AB to be used with the -22 engines. The cases should have provisions for nine (9) thermocouples. Other issues were AB failures to date that did not appear to endanger the aircraft, but two diffuser failures had caused the gauge of the skin to be increased and it was hoped this would prevent such failures in the future. CV felt only limited testing could be accomplished using a jet diffuser and strongly encouraged further NACA facilities be engaged for investigation in the 30,000‑50,000 ft range. They suggested a program consisting of a number (possibly 6) of ABs to be designed by Solar with NACA recommendations and then each to be tested at NACA throughout the altitude range. Written notes in the margins at BuAer state that following such an approach would preclude availability of any AB for the XF6U-1 project. Another note states the NACA project on ABs is to follow completion of the (Grumman SSM-N-6) Rigel program. Tests were planned on the Westinghouse and NACA afterburners and then more work would follow on Solar’s AB.

14 July 1948: CV Report 7512 A Preliminary Report on the Testing of Solar Afterburner A-103 in the Model XF6U-1 Airplane

Fig. 19. XF6U-1 aft fuselage drawing showing Solar -103 installation layout.

The preliminary report covered the ground and limited flight testing of a Solar A-103 type AB from time of installation in the experimental XF6U-1 to April 19, 1948. All the cooling data taken was presented in a series of charts. Internal performance of the AB and engine in regard to consideration of thrust gains, combustion efficiencies, pressure drops, etc. was not discussed but would be covered in a subsequent report. The key finding was that preventing air leaks in the AB assembly was very critical in cooling of the compartments and it was necessary to be sure they were kept to an absolute minimum. After early testing had shown the aircraft engine compartment had adequate cooling on the ground, it suddenly began to overheat in later testing. This was eventually traced to air leaks by removing the AB, sealing both ends and pressurizing the AB with one pound of air pressure. The leaks were sealed by various means and when airframe testing resumed the overheating was not longer occurring. All AB airborne starts were done manually via switches in the cockpit. A master switch between the AB controls and the aircraft electrical system protected the aircraft in the event of any system failures. Various changes in the installation and the AB were made during the air leak investigation and some of these were recommended to Solar be made permanent. In particular, the clamp joining the AB to the engine had the number of bolts doubled.

Start attempts with the eyelids open before ignition was initiated and the fuel was turned on failed at any engine speed over 7,500 rpm. The start sequence on the ground and in flight began with the eyelids closed. The AB fuel flow was preset. The ignition was turned on and then the AB fuel flow initiated. As soon as the pilot saw the turbine out pressure began to increase he opened the eyelids fully. The engine throttle and AB fuel flow could be adjusted to give the desired operating conditions. This was found to be difficult in flight. Due to the inter-relationship between the engine rpm and the AB fuel flow, fine adjustments were found to be difficult to accomplish. Ram in flight further complicated things. For high power flights, at 12,000 ft, the fuel control valve was preset to the flow needed in flight at the stabilized airplane speed. The aircraft was glided to a speed 25 to 50 knots below the stabilized value and then the AB started. This gave consistent and smooth starts. Various failures to follow the set sequence of switch operations during starting did not damage the engine or the AB. However, opening the eyelids before a pressure rise was observed caused a blowout of the AB.

Five different Holley all-speed governors had to be used during the testing as their performance ranged from very unsatisfactory to excellent depending on the particular governor. (Note: CV likely included this observation as the basic F6U-1 without the AB were using the same engine and governors and experiencing the same problems with governors.)

[Autor's Note – It is clear that with two different airframe projects depending on afterburners to achieve their performance expectations now proceeding at a rapid pace and with no apparently viable afterburners yet appearing on the horizon, CV was attempting to drive BuAer to get on top of the situation. Anyone who previously thought afterburners would be easy must have been disillusioned by this time.]