B. Forward fuselage rake was installed on aircraft at Sta. 50.

C. University of Wisconsin photometer installed in upper bug eye camera position.

D. Specially assembled and "broken-in" APU's, S/N 7 AN and 20 AN. Description of procedures for preparation in Section IV.

B. Low range transducers were installed to record data from the fuselage rake.

C. Installation and checkout of the University of Wisconsin photometer was accomplished.

B. #1 and #2 APU's were removed due to excessive wearing of pinion gears. These failures and previous failures of the APU pinion gear precipitated a meeting at General Electric, Lynn, Massachusetts facility during the week of December 30th. At this meeting representatives of the Air Force, NASA and GE reviewed previous failures and design criteria. At this meeting it was determined that the failure could be caused by a combination of three items: gear-tooth finish, break-in procedure, and lubrication.

General Electric built up APU S/N 7 AN using a pinion with an improved surface finish, and AFFTC built up APU S/N 20 AN. Extreme care was taken in aligning the gears and in balancing the complete units. A break-in procedure in which the units were started under no load and increased to full-load over a 2 hour period was used. The gear cases were then separated and inspection of the pinion gear confirmed that a suitable finish had been obtained on the pinion gears of both APUs.

In the mean time other tests were being conducted on a ground test APU to obtain a suitable oil. These tests used an evacuated gear case to evaluate the efficiency of the oil at an altitude of about 85,00 feet. A pinion gear failure was obtained using oil commonly used at NASA (Mil-L-7808D) manufactured by Bray Oil Company. Similar tests using Texaco Mil-C-7808D produced no failures. APU S/N 7 AN was then installed in the #1 hydraulic system and APU S/N 20 AN was installed in the #2 hydraulic system.

During the flight, APU S/N 7 AN which was installed in the #1 hydraulic system during preflight, experienced an alternator dropout at approximately 4 minutes after launch followed by complete hydraulic pressure loss at approximately 8 minutes after launch. Post flight investigation of the APUs revealed a completely failed pinion gear in the #1 APU and a badly worn pinion gear in the #2 APU.