7 May 1948: McDonnell Contract NOa(s) 6130 Progress Report 863, 15 February to 15 April 1948
Summary of Work Completed:

1. Further static performance and cooling tests were made.
2. Authorization was obtained to run AB altitude and speed performance tests at NACA laboratory in Cleveland, Ohio.
3. The AB design was improved.
4. Design and procurement of AB accessories for flight testing was continued.
5. Fabrication of redesigned AB and cooling shroud was completed.

Experimental Work:

1. AB Performance Tests: The AB used was described in the last report. The installation included a shroud and removable cold flow calibration nozzle.

Fig. 1. Modified A1-5000 AB in March 1948 with Cooling Shroud Installed and a Plain Nozzle for Testing	Fig. 2. Modified A1-5000 AB in March 1948 with Cooling Shroud Standoff Hat Sections Visible Prior to Installing Shroud

2. During testing, a part of the shroud was shielded from radiation by a 10" x 12" sheet in order to determine the possibility of using a radiation shield for additional cooling. The following data were obtained:

Component	Without Radiation Shield	With Radiation Shield
Without Afterburning (at Military Thrust)
Afterburner Skin	1,055°F	1,050°F
Radiation Shield	---	610°F
Shroud	365°F	230°F
Cooling Flow	No Measurable Flow
With Afterburning (at Approximately 30% Augmentation)
Afterburner Skin	1,835°F	1,550°F
Radiation Shield	---	610°F
Shroud	585°F	190°F
Cooling Flow	Approximately 1.5% of Turbojet Airflow

The tests indicated that the shroud temperature could be held under the required maximum of 250°F at any operating condition if a radiation shield was added and a cooling airflow of approximately 2% of turbojet airflow was available during operation.

1. A maximum thrust augmentation of 38% with an overall SFC of 2.54 lb/hr/lb was obtained at turbojet military rpm with AB wet.
2. The previous data on low non-AB thrust loss was confirmed. The loss for the model was 3.0% with an increase of 3.2% in specific fuel consumption.
3. The ignition characteristics were better. Smooth ignition was obtained at military rpm and approximately 50% of maximum AB fuel flow.
4. The surface type fuel injectors were not successful. The AB would not ignite at turbine speeds over 9,000 rpm and burning was unstable and sensitive to fuel flow changes.
5. Test time was cut short by structural failure of the AB forward section. The sheet thickness of this section had been reduced to 0.043" from 0.062" thickness of the initial AB. This had been done to see if weight could be reduced. The thinner sheet cracked at several spots near the shear bold bosses and along the diffuser divider welds. The islands cracked at several spots near the shear bolt bosses and along the diffuser divider welds.
6. The hat-section shroud supports were not satisfactory. When the AB expanded during operation, some of the supports were bent down and others dented the combustion chamber wall. A modified support consisting of a ring fastened to the AB by a series of metal strips welded in at an angle was tested and proved satisfactory.

Performance Tests of AB Under Speed and Altitude Conditions:

1. Authorization was obtained to test the McDonnell AB in the NACA Flight Propulsion Laboratory in Cleveland, Ohio under speed and altitude conditions.
2. The NACA tests were scheduled to begin 24 May 1948.
3. As the two-position exit nozzle would not be completed and tested by 24 May, fixed area nozzles would be used.

Afterburner Design Improvements:

1. Several improvements were completed and released for fabrication of the NACA test models.

a. A bellows type alignment joint was added. By adding the bellows at the junction of the outer step and the combustion chamber, the usual extra stops and bearing rings proved to be unnecessary.
b. A long electrode spark plug was substituted for the formerly inaccessible inner ignitor.
c. The fuel manifolds were welded directly to the AB skin to prevent vibrations and the resulting fatigue failures of the previous separate manifold.
d. The shear bolts and bosses were removed from the cone support structure. By using formed flanges and spotwelds at all island junctions, fabrication was simplified and structural strength increased.
e. The unsatisfactory hat section shroud supports were replaced by rings rigidly connected to the combustion chamber by a series of supports welded on at an angle.
f. A full length radiation shield was added between the shroud and the AB body. The radiation shield and shroud were connected by corrugated bands and spotwelded together.

Design and Procurement of Flight Test Accessories:

1. The design of the flap type two position exit nozzle was completed and released to the shop for fabrication.
2. Negotiations for the purchase of an AB automatic control system were completed. (Who with was not mentioned.)

Fabrication of the Redesigned Afterburner:

1. One (1) AB for the NACA tests was completed and delivered to the Westinghouse test laboratory for acceptance tests.
2. An alternate AB for the NACA tests was being constructed and was due to be completed by 1 May 1948.
3. The tooling and fabricated parts of the flap type exit nozzle had been completed.

Planned Work for the Next Period:

1. Complete construction of the flap type nozzle and the alternate AB model for NACA tests.
2. Complete static performance and acceptance tests for NACA model AB.
3. Make operational tests of flap type exit nozzle.
4. Start AB performance tests under speed and altitude conditions at NACA laboratories.
5. Continue design of AB for flight tests.

15 July 1948: McDonnell Contract NOa(s) 6130 Progress Report 925, 15 April to 15 June 1948
Summary of Work Completed:

1. Satisfactory static performance tests on the Model A for NACA tests were limited by structural failures.
2. The models for NACA tests were redesigned and reworked.
3. Experimental proof tests for static performance of the modified Model A ABs were completed with satisfactory performance and endurance.
4. Research tests were run to try the effect on performance with and without a shroud and performance with additional flame-holding steps.
5. Scheduled NACA tests were postponed but negotiations were continuing for the altitude tests.
6. Design and procurement of installation accessories continued.

Fig. 3. Schematic Cross Section of NACA Afterburner Sent for Tests	Fig. 4. Modified A1-5000 AB in March 1948 with Cooling Shroud Installed and Plain Nozzle for NACA Testing	Fig. 5. Modified A1-5000 AB in March 1948 Entrance End for NACA Testing

Experimental Proof Tests of Model A Afterburners:

1. The Model A ABs were redesigned and reworked.
2. In order to ensure reasonable endurance and good performance of the AB scheduled for the altitude tests, a proof test for static performance was set up as follows:

a. Maximum AB operation at 12,500 rpm for 4 periods of 5 minutes each, combined with;
b. No-afterburning operation at 12,000 rpm for 4 periods of 15 minutes each.
c. Satisfactory AB ignition at 12,500 rpm.

3. Tests were started on 4 June 1948. After a check run of 7 minutes of AB operation was completed without failure, the proof test was run as described. The thrust boost was limited to 30% by the exit diameter of the AB. Post operation revealed a failure of an ignition-fuel tube. This tube was in the inner cone, so the resulting internal burning had overheated the turbine disc bolts so that the heads were sheared off by centrifugal forces. The loose bolt heads bent over the trailing edges of most of the turbine blades and made several deep dents in the inner cone skin. A total time of 30 minutes of AB operation was completed before the damage was discovered. The second model with an identical rework gave a satisfactory performance of 21 minutes without any failures.
4. AB shroud temperatures and mounting pad temperatures determined during the above tests showed that additional cooling might be required during the non-burning cycle of operation. The current design allowed for no ejector action during that operation cycle.

Component	Temperatures
Shroud	Burning 250°F	Non-burning 450 – 500°F
Last 3" of Shroud	900 – 1,200°F	300 – 350°F
Mounts	200 – 250°F	300 – 350°F
Bellows	1,200°F	1,200°F

5. It was noteworthy that during both sets of Model A AB tests, spontaneous combustion without spark occurred during fuel manifold calibration with closed exit nozzle flows as low at 1,500 lb/hr.

Additional Research Tests:

To test the effect on performance due to additional flameholders and thrust with and without a cooling shroud, a test vehicle was assembled from parts of previous models. Four tests were completed with shroud, without shroud, with one divider step and with two divider steps. The variation in performance was very small and appeared to be within the limits of experimental error.

NACA Negotiations for Use of the NACA Facilities:

The tests initially scheduled for the first week in May were rescheduled as unforeseen delays in other tests being conducted at NACA caused the test date to be postponed to the third week in June. During the interim between the May and June test dates, the NACA test schedule was altered to include tests having a higher priority and as a result the McDonnell AB tests were postponed indefinitely.

Design and Procurement of Installation Accessories:

1. Space limitations forced a redesign of the ignitor installation. Ignitor manufacturers were requested to submit designs suitable for altitude operation and the space available.
2. The engine driven and electrically driven fuel pumps offered with the automatic AB control purchased were found to be unsuited to the McD AB installation. An air turbine driven pump was then considered. Westinghouse tests showed that bleeding compressor air to power the air driven fuel pump had no detrimental effect on engine operation other than lowering performance by approximately 1 to 2%.
3. Vendors were being consulted concerning component parts required for the McD designed control system.

Work Planned for Next Period:

1. Continue the design, improvement and fabrication of variable exit nozzles.
2. Perform further static test of AB, nozzles, and controls.
3. Continue negotiations for NACA altitude and speed performance tests.
4. Begin construction of AB for flight tests.

3 September 1948: McDonnell Contract NOa(s) 6130 Progress Report 969,
15 June to 15 August 1948:
Summary of Work Completed:

1. The two position exit nozzle was reworked.
2. A variable exit nozzle was designed and constructed.
3. Design of an AB stressed for experimental flight tests was begun.
4. Design of an experimental flight test installation was begun.
5. An AB was delivered to NACA in Cleveland for altitude and speed performance tests.

Design and Fabrication of Variable Exit Nozzles:

1. The prior two-position nozzle was redesigned and reworked. The new design allowed for more complete retraction out of flow of exhaust gases. The flaps were reinforced to prevent warping. The combustion chamber nozzle was reinforced by a half-tube section to hold the nozzle more nearly round and prevent warping.
2. The variable nozzle design was essentially a series of channel-sectioned segments attached to the combustion chamber by means of a sealed hinge with expansion cones to provide for the large change in area. The nozzle was actuated by push-pull cables working on a unison ring moving on cam surfaces on the nozzle segments. The design presented possibilities of decreased nozzle losses, maximum augmentation at all speeds and altitudes (limited only by the practical F/A ratio), more uniform cooling airflow through the ejector cooling shroud during both AB operation and operation of the engine at a constant turbine temperature.

Fig. 14. McD Variable Nozzle in Closed Position	Fig. 15. McD Variable Nozzle in Open Position

Accessories:

Several ignitor manufacturers submitted the requested designs to comply with the revised space limitations of the flight test installation. A choice would be made and tested at the earliest possible date.

Installation Design:

The design of the airframe alternation necessary for an experimental flight test installation of one McD AB on the XF2H-1 was 20% completed. This would allow a safety factor of another unchanged engine installation in flight. Recording of test data, fairing and cooling the AB and the location of fuel lines and control mechanism within the structure would be allowed for in the design.

Afterburner Design:

The designs tested to date had been static test models. A complete flight model redesign had been started and the drawings were now 70% completed as of 15 August 1948. The design had to accommodate the following stress loads:

1. 3g side load
2. 4.8g fore and aft load
3. 16g vertical load

The radiation shield was redesigned with a slight taper to allow for easy installation as it slipped over the combustion chamber. A quick disconnect was designed to facilitate rapid assembly of the AB to the engine.

Simulated Altitude and Speed Tests:

A McD AB with fixed cone exit nozzles was delivered to NACA in Cleveland on 10 August 1948 for simulated altitude and speed tests. The tests were to start during the first week of September 1948. As the special ignitor required for high-altitude ignition could not be obtained in time, an ignitor was fabricated from parts of a standard aircraft spark plug. When tested statically at 12,000 volts, the plug gave a satisfactory spark over a 5/16" gap.

Fig. 16. Bayonet Type Spark Plug. Top – Component Parts. Right – Assembled Unit

Work Planned for the Next Period:

1. Test two position and variable nozzles at Westinghouse.
2. Perform simulated altitude and high-speed tests at NACA Cleveland.
3. Continue procurement of accessories.
4. Complete drawings for flight test AB model and installation.

Three failures occurred during testing, two related to design and one due to instrumentation:

1. Failure of a divider section – This failed after approximately 4 hours engine time dry in the altitude chamber. The failure was attributed to vibration fatigue. A thicker section of 0.062" Iconel was used in the repair along with extra re-enforcements added at the struts. The repair proved to be satisfactory during the balance of the testing.
2. Failure of the flexible coupling – After 2 hours of AB operation in the test chamber and 12 hours of engine time the flexible coupling burned out at one spot. This was caused by extensive warping of the skin at the flame holder and the resulting concentration of flame on the coupling bellows. A welded repair gave satisfactory operating for the remainder of the testing.
3. Failure of the outer skin – An instrumentation hole gasket burned out and permitted flame leakage through the skin.