X-15 OPERATIONS FLIGHT REPORT

FLIGHT NO: 2-37-64 DATE OF REPORT: May 14, 1965

PILOT: John B. McKay DATE OF FLIGHT: April 28, 1965

CARRIER AIRCRAFT: B-52 #008 LAUNCH LAKE: Hidden Hills

ENGINE: S/N 110

PURPOSE OF FLIGHT: (1) Stability & Control Data

(2) Thermal Loading Effects on Landing Gear

(3) Star Tracker Functional Checkout

(4) Landing Dynamics

I. Discussion of Previous Operations

A. Propellant turbo pump oscillations noted during flight 2-36-63 resulted in rejection and removal of engine S/N 108 which was returned to the AF Facility for metering valve and governor repair. Engine S/N 110 was installed in X-15-2 for flight 2-37-64.

B. Investigation of the RH main gear uplock system failure (reported in the last report for flight 2-36-63) supports the theory that excessive loading of the main uplock hook is caused by thermally induced bowing of the main strut. Ground heating tests made to simulate aerodynamic heating of the main-gear struts for a calculated "hot flight" profile (2-22-40) caused bending of the hook and release of the gear (complete description of these tests and results are contained in separate reports from the Structural Mechanics Section, FRC.)

As a result of these tests the main-gear uplock has been modified to include:

1. Stronger hook

2. Belleville washer mounting system to provide approximately .14 inch "bowing" of the strut (as measured at the uplock roller).

3. Increased strength of back-up structure on bulkhead.

In addition to the above modifications, it was necessary to repair the sheet-metal fuselage longeron structure in the area of the RH main-gear drag-brace anchor fitting. This structure buckled under the severe drag loads imposed by the excessive speed at which the gear deployed. While the repair itself was not complicated, access was extremely difficult necessitating removal of much of the hydraulic plumbing in the lower engine bay. II. Configuration Changes A. Main gear uplock modifications (as outlined in I B above.)

B. Modified differential pulley for landing gear actuating cable system to improve cable alignment.

C. Marotta solenoid valve installed to "lock in" emergency jettison source pressure to permit pilot to maintain tanks in jettison mode down through landing.

D. Incorporated the following EO's to provide additional "hot compensation" in the speed brake system:

878856

878855

E. Incorporated the following miscellaneous EO's:

894466

882590

898262

892602

882445

F. Installed bushing in LH horizontal stabilizer actuator trunnion fitting (salvage for oversize hole.)

G. Installed appropriate instrumentation to record:

l. Main gear uplock hook loads (LH & RH)

2. Belleville washer compression (LH & RH)

3. Hook vs uplock roller position (RH only)

4. Various main gear strut skin temperatures (LH & RH)

5. Strut bowing (RH only)

III. Preflight Events A. On Monday 3/1/65, a heat test with original design main uplock hooks was conducted. Failure was induced by simulating the heat profile of a typical heat flight (2-22-40). (See discussion under item I B.)

B. On Saturday 2/6/65, extensive salvage repair of buckled RH fuselage longeron was started (see discussion under item I B.)

C. On Tuesday, 3/30/65, a heat test with modified main uplock hook design (Belleville washers) was conducted. No permanent deformations or failures were noted. The test was deemed successful and the uplock system was approved for flight test.

D. On Thursday, 4/8/65, the engine ground run was completed. Heavy rain followed and resulted in enforced "down" time for all X-15 aircraft.

E. On Thursday, 4/23/65, the APU ground run was completed.

IV. Flight Events A. Flight 2-37-64 was made on Wednesday, 4/28/65. The landing gear system gave no trouble during this flight. Preflight servicing was normal and without incident. A preflight ground jettison test was made.

B. Flight squawks resulting from this flight were:

1. Unprogrammed roll oscillations.

2. Inertial altitude failure.

3. Startracker system failed to meet test objectives largely due to inadequate switch controls. A modified pilot control system will be incorporated for the next flight

Approve By: Prepared by:

Perry V. Row William P. Albrecht

X-15 Senior Project Engineer X-15 Project Engineer