Stratotanker 135
Flight Crew Multiengine; Flight Crew Flight Instructor; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 53; Flight Crew Total 4500; Flight Crew Type 662
Situational Awareness; Troubleshooting
Aircraft Equipment Problem Less Severe; Deviation - Altitude Excursion From Assigned Altitude; Ground Event / Encounter Loss Of Aircraft Control; Inflight Event / Encounter Weather / Turbulence
Flight Crew Regained Aircraft Control
Weather; Human Factors
Aircraft X was the tanker conducting Air Refuel Training with Aircraft Y; the receiver. Both aircraft encountered light to moderate turbulence at block altitudes of FL250-FL270 and was unable to attempt air refueling. Aircraft X requested a climb for the formation to the block altitudes FL260-FL290 and was cleared by Center to maintain the blocks FL260-FL290. Once established at FL290; both airplanes encountered light chop and Aircraft Y requested to move into the contact position to simulate receiving fuel. Aircraft X approved the request and Aircraft Y made contact.Fifteen seconds after Aircraft Y made contact; Aircraft X went into several porpoising pitch oscillations of +/- 150 feet; the autopilot on Aircraft X inadvertently disconnected; causing the pilot flying on Aircraft X to call for an emergency 'breakaway.' While Aircraft Y dropped behind Aircraft X; the Pilot Flying Aircraft X experienced full nose up pitch; resulting in an uncontrolled climb of 600 feet above the cleared top of the altitude block. Once the aircraft was under control; Aircraft X descended back to FL290; was unable to reconnect the autopilot and continued the mission with autopilot off.The combination of the turbulence; excessive closure; and the receiver's slow descent during the breakaway contributed to the altitude deviation. The crew on Aircraft X was able to reduce the excessive pitch and determined the autopilot would no longer couple and could not be used to conduct air refueling training.Chain of events (human performance considerations)- How the problem arose- Contributing factors - How it was discovered- Corrective actions - Perceptions; judgements; decisions- Factors affecting the quality of human performance - Actions or inactions
KC-135 Pilot reported while attempting to refuel another aircraft; turbulence made their aircraft go into a full nose-up pitch after an emergency breakaway; resulting in an altitude block deviation.