A power outage, required to permit maintenance work at the KSC Launch Control Center, was relayed to the pneumatic controls of the S-IC stage of the Apollo 10 launch vehicle, causing the prevalves to open and allowing 5,280 liters of RP-1 fuel to drain from the vehicle.

This, in turn, produced negative pressure in the RP-1 tank, which displaced the upper bulkhead.

After repressurization, the bulkhead apparently returned to its normal shape. An effort was under way to determine the nature of the damage to the bulkhead and the effect on the May 18 Apollo 10 launch readiness date.