Kc-135 pilot reported while attempting to refuel another aircraft; turbulence made their aircraft go...

Narrative:

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

Original NASA ASRS Text

Title: 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.

Narrative: 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

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1597941
Time
Date	201811
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	Mixed
Light	Night
Aircraft 1
Make Model Name	Stratotanker 135
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Flight Plan	IFR
Aircraft 2
Make Model Name	Military
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Flight Plan	IFR
Person 1
Function	Pilot Flying Captain
Qualification	Flight Crew Multiengine Flight Crew Flight Instructor Flight Crew Instrument Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 53 Flight Crew Total 4500 Flight Crew Type 662
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Altitude Excursion From Assigned Altitude Ground Event / Encounter Loss Of Aircraft Control Inflight Event / Encounter Weather / Turbulence

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.