McDonnell Douglas MD-88 N996DL

Summary

On 15 March 2001 at about 19:39 local time, a McDonnell Douglas MD-88 registered N996DL was involved in an incident near Tucson, Arizona, United States. 101 people were on board and nobody was injured. The aircraft was slightly damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

15 March 2001 at 19:39

Classification

Incident

Location

Tucson, Arizona, United States

Nearest airport

Tucson Intl. (TUS)

Coordinates

32.1164, -110.9408

Aircraft

McDonnell Douglas MD-88

Registration

N996DL

Category

Airplane

Engines

2

Operator

Not recorded

Operating rule

Part 121: Air Carrier

Phase of flight

Not recorded

Route

Tucson → Cincinnati

Aircraft damage

Minor

Weather

VMC

Light

Day

NTSB number

LAX01IA118

Nobody was injured.

the failure of 4th stage turbine blades during takeoff roll, which resulted in a dynamic imbalance in the engine.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

The air carrier airplane experienced severe vibrations and a loss of right engine power following a partial loss of 4th stage turbine blades during the takeoff sequence. According to the flight crew's statements, they noticed the vibration and loss of hydraulic fluid quantity and pressure shortly after VR. They then observed a loss of right engine pressure ratio (EPR) and the right engine thrust reverser indication lights. The flight crew reduced right engine power and landed uneventfully at the departure airport. The post-incident examination of the right engine revealed the engine event was caused by the imbalance of the low pressure turbine (LPT) rotor due to a significant loss of the 4th stage blade airfoil and shroud material. This imbalance resulted in rub between the LPT shaft and the high pressure turbine (HPT) shaft. A hole was eventually rubbed through the LPT shaft. Oil in the vicinity of this shaft rub was ignited, giving the LPT shaft the appearance of burn through. The extent of the damage to other systems (hydraulic lines, EPR reference lines, fire warning systems, etc.) was attributed to the duration of excessive vibration experienced until the engine was safely shutdown. Prior to the incident, the right engine was placed on a 50-cycle continue-in-service limitation in accordance with a P&W internal engineering notice for missing 4th stage turbine blade shroud/shrouds. At the time of the event, the right engine had accumulated 13 cycles of the 50-cycle limit. The post-incident blade material loss observed was well above that allowed under the continue-in-service limits, and the imbalance was most likely the result of another event that occurred after the continue-in-service shroud inspection. The cause of the 4th stage material loss could not be conclusively determined.

Quoted verbatim from the NTSB record.