Trans World Airlines Flight 73
Boeing 717-231 · Incident: airframe, component or system failure during takeoff
From General Mitchell International Airport (MKE) to St. Louis Lambert International Airport (STL)
Event
- NTSB case
- CHI01IA124
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Incident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 0 · all aircraft and ground
- Ground fatalities
- Unknown
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- Airline
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
Boeing 717-231
- Aircraft type
- Boeing 717
- Category
- Airplane
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N2410W
- Operator
- Trans World Airlines
- Onboard fatalities
- Unknown
- Route
- From General Mitchell International Airport (MKE), Milwaukee, WITo St. Louis Lambert International Airport (STL), ST LOUIS, MO
- Aircraft age
- Not recorded
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 121: Air Carrier
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- Takeoff
- First occurrenceThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Airframe, component or system failure
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- None
Cause areas
- Thrust reverser, actuator › Failure
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
A Boeing 717 sustained an in-flight thrust reverser deployment following a takeoff. The flight returned without further incident. After the prior flight the reverser was unlocked but not deployed. The flightcrew found the reverser unlock light during preflight. The crew could not clear the indication and contract maintenance was contacted to lock out the reverser. The contractor was not familiar and asked for the procedure to be faxed to him. The contractor used an incomplete set of procedures to lock out the reverser. Post incident inspection revealed the thrust reverser doors had over deployed. Four locking pins and their fork shaped locking triggers showed nicks and gouges on their mating surfaces. Subsequently Boeing revised their dispatch guide to include that maintenance would have to verify that "no more than one Thrust Reverser Proximity Sensor indicates Open" and that operators verify that the thrust reverser unlock indication is not present and red lockout pins are present on the inoperative reverser. Subsequent to the incident the overcenter links were redesigned. Boeing and the thrust reverser manufacturer issued service bulletins (SB) to retrofit the existing engines with the new link's design change, the link's associated hardware, and rub plates. Airplanes in production will incorporate the SB items as a production change. Boeing's SB 717-78-004 stated, "Operators have reported five instances of thrust reversers failing to deploy and ten instances of side beam gouging. Inspections revealed that gouging had occurred between the over center link bolts and side beam assembly. One recent event resulted in a relatively new thrust reverser having side beam gouging so deep, it required a doubler to restore airworthiness. Rohr Incorporated Service Bulletin R715.78-008 provides instructions to modify the thrust reverser actuation system. The purpose of modifying the thrust reverser actuation system is to minimize the possibility of gouging and inadvertent in-flight thrust reverser deployment procedures given in this service bulletin."
Probable cause
The failure of the operator to provide complete and comprehensive thrust reverser lock-out maintenance procedures and guidance to the contract maintenance personnel resulting in a partial and inadequate securing of the faulty thrust reverser and a subsequent inadvertent deployment following takeoff. Contributing to the incident is the failure of the contract maintenance personnel to verify that the maintenance instructions received where complete, accurate, and up to date.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record CHI01IA124
- Event ID
- 20010427X00832
- Case number
- CHI01IA124
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
Source notes (4)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status, damage. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: d982be80bc93fae7f57f88430e73608eada393f763c0e4aedac1651a1ddf4166; retrieved 2026-09-18T16:16:39.581Z.