Investigation Summary
The sequence of failure began at 20:21, shortly after departure from Springfield, when the left generator failed due to a sheared spline drive shaft. While attempting to manage the failure, the first officer mistakenly isolated the right generator from the electrical distribution system. Although the right generator remained mechanically functional and was producing voltage, the crew was unable to restore it to the bus. The captain, known for a 'one-man operation' style and a history of prioritizing schedules over safety regulations, decided to press on to Carbondale rather than returning to Springfield, which was significantly closer. As the flight progressed, the crew failed to adequately shed electrical loads, keeping systems like the pitot heat and various cabin lights active. The battery voltage steadily dropped from 27.5V to 13V over approximately 31 minutes. The Cockpit Voice Recorder (CVR) failed as the voltage dropped below its operating threshold, followed by the loss of the flight director, horizon indicators, and radio navigation equipment. In the final minutes, as cockpit lighting failed, the captain requested the first officer to have a flashlight ready to illuminate the instruments while attempting to navigate through rain and fog. The aircraft eventually struck trees and crashed approximately 20 miles north of its destination. Following the accident, the FAA grounded the airline. During this period, only the airline's BAC One-Eleven jets were initially allowed to return to service in December 1983 after an extensive manual rewrite, while the turboprop fleet remained grounded until March 1984.
Final Conclusions
The NTSB determined the probable cause was the captain's decision to continue to a distant destination following the loss of DC electrical power instead of returning to the nearby departure airport. This decision was influenced by self-imposed psychological factors and an inadequate assessment of battery endurance. Contributing factors included Air Illinois' failure to provide adequate recurrent training and the FAA's failure to oversee such programs, which left the crew unable to properly manage the electrical malfunction or understand the limitations of their emergency power supply.
Photographic Evidence (1)
Video Analysis
The Pilot Who Refused to Turn Back | Air Illinois Flight 710 — A detailed look at the 1983 crash of Air Illinois Flight 710, where a series of electrical failures and poor command decisions led to a fatal crash in the Illinois woods.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Crew Experience
Captain
Lester R. Smith, aged 32. Described as having a habit of violating safety regulations to maintain schedules.
First Officer
Frank S. Tudor, aged 28. Failed to successfully challenge the captain's decision to continue the flight.
Systems & Failure Modes
DC Electrical System
Consists of two engine-driven generators and lead-acid batteries. The failure of both generators left the aircraft entirely dependent on battery power for flight instruments, radios, and lighting.
Generator Control Units
The crew attempted to reset the Remote Control Circuit Breakers (RCCBs) but were unable to bring the right generator back online after it was isolated.
Pitot Heat
A high-draw electrical system used to prevent ice buildup on airspeed sensors; the captain's decision to keep this on contributed to faster battery depletion.
Interesting Facts
- 01The left generator failed due to a sheared spline drive shaft.
- 02The right generator was functional but was erroneously isolated by the first officer.
- 03The captain was only 6 minutes from Springfield when the failure occurred but chose to fly 39 minutes to Carbondale.
- 04The aircraft was operated in IMC (Instrument Meteorological Conditions) with rain and fog at the destination.
- 05The airline was grounded by the FAA following the accident due to safety concerns identified during the investigation.
Safety Actions & Advisories
FAA Grounding and Certification
The FAA grounded Air Illinois and required a complete rewrite of the company's operations manual and recurrent training programs before allowing a return to service.
Known Controversies & Unanswered Questions
Dissenting Probable Cause Opinion
Reference ↗NTSB member Patricia A. Goldman filed a concurring statement but dissented on the inclusion of training and FAA surveillance in the probable cause, arguing it obscured the pilot's fundamental decision-making error as the primary reason for the crash.