B. Excessive leakage through the NH3 regulator in the unpressurized mode occurred during the last flight. The regulator was replaced.

B. The helium #2 high pressure manifold, containing threaded fittings and seals, was replaced with a welded assembly which eliminates the seals.

C. Installed RAS system.

D. Installed lower ventral probe transducer.

B. The X-15 was mated on Thursday, June 3, 1965, for planned flight 2-39-67 on Friday, June 4, 1965. The flight was aborted (2-A-67) during captive climbout when the cabin pressure regulator locked closed. Subsequent inspection of the regulator produced a significant quantity of condensed moisture in the regulator sense line. Blockage of this 1/4" diameter line will cause the regulator to lock closed. It was concluded that ice formation in the line caused the malfunction. A new line of 1/2" diameter and shorter length was installed to minimize the possibility of this situation repeating. The system was also purged with dry nitrogen. The X-15 remained mated through this period.

C. A second attempt to fly ended in abort (2-A-68) on Tuesday, June 9, 1965, when excessive leakage of helium from the engine #2 source occurred during climbout. A post flight leak check revealed a blown seal at the high pressure manifold. A welded manifold was installed in place of the existing threaded fitting and 0-ring assembly and this leak was eliminated. However, the system again failed to hold pressure at altitude resulting in another abort (2-A-69) on Friday, June 11, 1965. The X-15 was demated for further examination. No significant leaks were found when helium #2 source was serviced with chilled gas; however when various components of the system were sprayed with gas chilled to approximately -70°F, (roughly simulating conditions encountered at altitude) it was discovered that the Firex valve began to leak through internally, allowing the source to deplete. Upon returning to room temperature, the leakage would stop. The valve was replaced and again the chilled gas spray was applied. The new valve did not leak through, however, on the next day an ambient leak caused rejection of this second valve. A third Firex valve was installed and successfully held pressure at both chilled and ambient conditions.

D. The X-15 was recycled through preflight functional tests and ground run of the APU/BCS system was made on Wednesday, June 16, 1965. The vehicle was closed out for flight on Monday, June 21, 1965. In order to update basic weight figures, the X-15 was weighed by the Air Force Weight & Balance Branch in basic empty condition (with Star Tracker and Hycon cameras installed). After weighing the X-15, it was mated to the B-52.

E. Flight 2-39-70 was successfully flown from Delamar Lake launch area on Tuesday, June 22, 1965. Thundershower activity in the Mud Lake area had caused the change in launch area as of Thursday, June 10.

B. No major malfunctions occurred during this flight, although the following "squawks" were noted: