November 6, 1959

From NASA Flight Research Center

To NASA Headquarters RA

Subject: Summary of flight No. 3 of the No. 2 X-15 airplane (S/N 671)

1. The third flight of the No. 2 X-15 (S/N 671) occurred on Thursday, November 5, 1959. Because an explosion occurred in the engine compartment as the engines were being started, the pilot shut down the engines and jettisoned the propellants. As planned in case an emergency landing was required, the pilot glided to Rosamond Dry Lake and accomplished a landing. Fuselage structural damage was sustained on the landing and will be described in detail in the following paragraphs. Total flight time was about five minutes.

2. The launch was made from 45,000 feet at M = 0.82. Although the pilot reported the loss of roll damper at launch, the rolling was less severe than on the previous launch. The engine starting sequence was accomplished in a matter of seconds and appeared normal until the upper chamber on the lower engine was started. An explosion occurred in this chamber blowing off the last few inches of the chamber, including the nozzle extension. There was external damage around the engine baseplate and considerable damage within the engine compartment, particularly from the resultant fire. The explosion doors located on the aft end of the fuselage tunnels were also blown off. The extent of this damage will be assessed with disassembly of the airplane.

3. The pilot headed for Rosamond Dry Lake and planned for an approximate 270° overhead approach. The ventral was jettisoned and the flap and gear were lowered at similar conditions to the previous landings. Touchdown was accomplished near the center of the lake. A review of movies taken from one of the chase planes showed that the left main landing gear skid was in the nose down attitude after the gear was lowered but was in the correct attitude before touchdown. Touchdown occurred at a speed of about 150 to 155 knots at an angle of attack of about 11°. Rate of sink at touchdown is not presently known, however, there are indications from available data that it may have been 8 feet per second or higher. At initial main gear contact the main gear shock struts compressed about 60 percent, then extended to about 23 percent. This was followed by nose gear contact and bottoming of the nose gear oleo. Failure of the fuselage occurred when the nose gear oleo bottomed. At fuselage station 226.8, which is a production joint just forward of the liquid oxygen tank, severe buckling occurred along the top of the fuselage for about ten inches forward, and at the bottom of the fuselage the joint opened and sheared about 70 percent of the bolts. The fuselage contacted the ground and dragged for the remainder of the ground runout which covered a total distance of about 1500 feet. There appears to be minor bending of the liquid oxygen tank skin for a few inches aft of station 226.8, and there are at least two indentations in the forward bulkhead of the liquid oxygen tank.

4. The airplane is being trucked to North American Aviation, Inglewood, for complete damage assessment and repair. There are as yet no indications of how long will be required to repair the damage and/or modify the airplane.

Paul F. Bikle Director,

NASA Flight Research Center