No useful pogo data was obtained due to the early termination of the flight, and the accident was traced to a stress corrosion of the aluminum fuel valve, which resulted in a propellant leak that caught fire from contacting hot engine parts. The next flight was Missile N-22, a silo test from Vandenberg Air Force Base on 20 June, but once again the second stage lost thrust due to a gas generator restriction. At this point, BSD suspended further flights. Of the 20 Titan launches, seven would have required the abort of a crewed launch, and General McCoy had to make good 12 of the 13 remaining scheduled tests. Since the ICBM program came first, pogo suppression had to be shelved. On the other hand, only Missile N-11 suffered a malfunction due to pogo and the combustion instability issue had occurred in static firings, but not any actual flights. All Titan II failures save for N-11 were caused by gas generator restrictions, broken plumbing, or faulty welds. The trouble appeared to be with Aerojet, and a visit of MSC officials to their Sacramento, California, plant in July revealed a number of extremely careless handling and manufacturing processes. A systematic effort to improve the quality control of the LR-87 engines was launched, which included extensive redesigns of components to improve reliability as well as fixes to the gas generator restriction issue. Service history The Titan II was in service from 1963 to 1987. There were originally 54 Titan II Strategic Air Command missiles. The 54 Titan II missiles were on 24-hour continuous alert with 18 missiles each surrounding three bases: Davis–Monthan Air Force Base near Tucson, Arizona, Little Rock Air Force Base in Arkansas, and McConnell Air Force Base in Wichita, Kansas. Mishaps On 9 August 1965, a fire and resultant loss of oxygen when a high-pressure hydraulic line was cut with an oxyacetylene torch in a missile silo (Site 373–4) near Searcy, Arkansas, killed 53 people, mostly civilian repairmen doing The fire occurred while the 750-ton silo lid was closed, which contributed to a reduced oxygen level for the men who survived the initial fire. Two men escaped alive, both with injuries due to the fire and smoke, one by groping in complete darkness for the exit. The missile survived and was undamaged. On 20 June 1974, one of two engines failed to ignite on a Titan II launch from