Most recent conditions on X-15-1 indicate a relatively rapid deterioration in cabin leakage over several flights to approximately 70 CFM with a diminishing rate in the range of 70 to 80 CFM. A summary of cockpit leakage rates is presented below:

Date Event Results

During flight 1-28-49 fuel leakage was noted by the Chase One aircraft. Leakage ceased following tank pressurization. Subsequent operation during the flight was normal; extensive checks on the ground following flight failed to produce a valve leakage. The pneumatic control selector valve was eliminated as the cause of the unscheduled vent valve opening in flight.

Three valve replacements (including the original flight valve) were required to obtain an acceptable overboard helium leakage rate through the vent and sense ports. Large inconsistencies among the original bench qualifications at Airesearch, NASA Rocket Room checks, and aircraft functional tests were evident in regard to acceptable helium leaks from valve external ports. For example, one valve leaked 3600 cc/min through the vent port installed in the aircraft and 190 cc/min on the NASA Rocket Room bench. The final valve leakage installed on the aircraft was 200 cc/min.

C. An historical accounting of engine operation with engine S/N 109 follows:

Two flights have been made to date without prior engine ground operations.

B. Impact pressure probes.

All probes were installed prior to flight 1-28-49 and include:

BCS compartment at 20° right of bottom center.

Station 70 at 20° right of bottom center.

Station 70 at 80° right of bottom center.

C. G. compartment at 13° right of bottom center.

R.H. wing leading edge 3 outer pressure pickups.

Upper ventral L.E. - Two on movable and one on fixed ventral.

Lower ventral L.E. - One pitot static probe on fixed ventral.

Preston tube rake - Movable ventral R.H. rear edge.
In order to provide some clearance between X-15 upper ventral probes and the B-52 pylon, the upper fixed ventral probe was shortened to 1-3/8 inches. Clearances on the upper probes, top to bottom positions, were 14-3/8 in., 4-3/8 in., and 1-7/8 in., respectively.

C. A sensitive airspeed meter (O to 1000 knots) was installed in place of the C-6 standby attitude indicator for q profile evaluation. The "dogleg" total source was used.

B. The LOX topoff probe was inoperative on the fill side following mating to the B-52. The flight was made with partial system operation on the fill end cycle. Following flight the probe was removed and checked on both B-52 #008 and #003 with normal operation.

C. A second repair of a one inch crack in the R.H. side fairing at the wing front spar was accomplished by grinding out the crack to 1/16 inch width and adding a .008 inch thick inconel sheet cover.

D. The R.H. main gear uplock and roller have exhibited an increasing misalignment condition. It is necessary to preload the gear during the securing operation to avoid direct interference. Gear down operation has not been affected and is satisfactory. New parts are in fabrication and will be installed to improve alignment. This problem has occurred sporadically in the past on X-15-1.

E. Leakage from the engine S/N 109 turbine pump gas generator outlet flange has been noted during all post-operation checks with helium in the cold condition. The quantity of leakage produces very fine bubbles and has remained essentially constant (a leak of this quality is designated a foamy leak). Visual checks during pump operation have been made on each of (3) ground runs and indicated no steam leakage at operating temperatures.

B. The No. 1 chase pilot reported a delay in prime flow during the engine start sequence. Normal flow was reported prior to the precool select at minus 40 seconds. Data indicates .normal feed line pressure surges at prime select. Post-flight operation was normal. In sufficient time for line shock down is considered to be the cause of the delay between prime select and visual indications of LOX prime.

C. Smoke in the cockpit was reported by the pilot, originating from the forward cockpit area. Inspection of the nose gear compartment indicated extensive heating of the bulkhead heatshield and the area immediately above. Accumulated deterioration of the nose gear door rear seal has occurred allowing an increasing amount of leakage to impinge against the bulkhead heatshield. Repair of the seal was accomplished following flight.

D. The lower ventral recovery system sustained a malfunction, however, ventral recovery was accomplished. The pilot chute drogue did not fire because of a faulty firing pin-initiator cap operation. Evidence indicated only light contact between firing pin and initiator cap. Physical condition of the firing pin indicated a possible interference with a spacer may have absorbed sufficient energy to prevent proper impact on the cap. Repeated firings were made with parts similar to those used in the flight ventral and produced satisfactory results. Based on previous successful operations this malfunction considered to be an isolated case. However, an investigation is being conducted by NAA to determine if significant variations in pin lengths are being produced by the vendor and more rigid control will be exercised.

E. Delamination of the R.H. windshield inner glass occurred during the flight. The affected area covered approximately 4 square inches in the upper rear corner of the windshield and extending to the edge of the glass. Unlike the outer pane which is one piece, the inner pane is constructed of two optically flat plates with a heater core between the plates. The canopy assembly was sent to NAA for windshield replacement and glass analysis.