MD81, vicinity Chicago Midway, IL USA, 2008

Summary: 

On 7 July 2008, a Mc Donnell Douglas MD81 being operated by Midwest Airlines, Inc. had just taken off in day visual flight conditions when increasing pitch could initially not be controlled. Later, control was regained but with “higher than normal” pitch control pressure required to control the aircraft - after en-route diversion the aircraft landed uneventfully.

Event Details
When: 
07/07/2008
Event Type: 
Day/Night: 
Day
Flight Conditions: 
VMC

18822

Flight Details
Operator: 
Type of Flight: 
Public Transport (Passenger)
Intended Destination: 
Take-off Commenced: 
Yes
Flight Airborne: 
Yes
Flight Completed: 
Yes
Phase of Flight: 
Climb
Location
Location - Airport
Airport: 
LOC
Tag(s): 
Temporary Control Loss, Extreme Pitch
AW
System(s): 
Equipment / Furnishings
Contributor(s): 
Contributing ADD, Component Fault in service
Outcome
Damage or injury: 
Yes
Aircraft damage: 
Minor
Non-aircraft damage: 
No
Non-occupant Casualties: 
No
Occupant Injuries: 
None
Occupant Fatalities: 
None
Off Airport Landing: 
No
Ditching: 
No
Causal Factor Group(s)
Group(s): 
Aircraft Operation
Safety Recommendation(s)
Group(s): 
None Made
Investigation Type
Type: 
Independent

Description

On 7 July 2008, a Mc Donnell Douglas MD81 being operated on a US domestic ad hoc passenger charter by Midwest Airlines had just taken off from Chicago Midway Airport in day visual flight conditions when increasing pitch could initially not be controlled. As pitch was approaching 30 degrees nose up, flight crew control column and stabiliser pitch trim inputs resulted in control being regained but with “higher than normal” pitch control pressure required to control the aircraft thereafter. Since this condition could not be resolved by flight crew action using available drills or after consultation with the operator’s ground maintenance staff, an en route diversion to St Louis MO was initiated and completed uneventfully.

The Investigation

The Investigation was carried out by the National Transportation Safety Board (USA) (NTSB). Their Report attributed the control difficulty to an inflation of the tailcone evacuation slide which had occurred during aircraft rotation at take off when the unsecured slide cover had moved and initiated slide inflation. No airworthiness explanation for the unsecured status of the slide container could be established, nor any previous history of related tailcone slide problems on this or any of the Operator’s other similar aircraft. It was noted that the area containing the slide container is a rear emergency cabin exit which can be accessed “from the passenger compartment through the aft bulkhead pressure door and aft accessory compartment”

It also noted that the passengers on the flight had included US Secret Service Personnel on duty because of the identity of the primary passenger and stated that:

“The results of an internal USSS investigation relating to security sweeps of the incident aircraft revealed that no USSS personnel or USSS support personnel interfered with or altered the aircraft’s hardware or systems relating to the tailcone evacuation slide.”

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