With constrained funding and personnel resources, the Federal Aviation Administration had to find a way to quickly identify emerging safety issues, implement intervention strategies, and investigate methods for improving the use of aviation safety data and information. To do this, Abacus Technology created a simulation model of the FAA's Aviation Safety Hotline.

Aviation Safety Hotline Operations
The Aviation Safety Hotline is a voluntary, confidential reporting system which was initiated in 1985 to provide a means for persons having knowledge of alleged FAA regulation violations or unsafe aviation practices to report these without fear of recrimination. Safety concerns reported to the Safety Hotline include maintenance problems, crew flight and duty-time issues, and aviation security matters.

The FAA has received over 12,000 calls to the Safety Hotline since its inception and currently receives about 100 calls per month.

Reports to the Aviation Safety Hotline are received over the telephone and entered into the Aviation Safety Hotline Information System (ASHIS) database by Hotline operators.

Urgent calls are treated with the utmost priority and are investigated as soon as possible to resolve any unsafe situations. Non-urgent reports received the previous business day are processed daily by Hotline Program Managers in the FAA's Office of System Safety.

Program Managers screen out reports which have insufficient information for investigation or do not relate to a safety issue. Technical specialists of various aviation disciplines then evaluate the reported information and assign action to the appropriate FAA headquarters or regional office for investigation.

Reports assigned to an FAA regional office may be investigated by the regional office or further assigned to an appropriate field office for investigation. All Safety Hotline reports sent for action require a close-out report in writing sent from the investigating office to the Program Managers in the Office of System Safety to update the central database.

Our Approach
In modeling the FAA's Safety Hotline, we first defined the project objectives, level of detail, and expected results in conjunction with FAA personnel. Abacus staff developed a preliminary flow diagram of the Safety Hotline analytical process based on interviews with Safety Hotline Program Managers.

We then conducted a stakeholders meeting in which individuals from around the country that are involved in all aspects of Aviation Safety Hotline operations participated. The flow diagram was used as starting point to verify and build on our understanding of Safety Hotline operations and was modified through stakeholder comments at the meeting.

The revised flow diagram was used conceptually to develop a complete model of Safety Hotline operations using ServiceModel. The model was built incrementally, starting with a simplified representation of Hotline activity and progressively adding in complexity. At each step the model was tested and verified before adding a new level of detail.

At the same time, we documented modeling assumptions and determined more detailed data requirements for the model. Abacus then designed and distributed data collection instruments to Safety Hotline stakeholders. Hotline stakeholders were interviewed to obtain additional data or to round out the data provided through the collection instruments.

The complete model was tested to ensure an accurate representation of the system and validated using the actual data collected for reasonableness of output results. Once the model was completed to FAA's satisfaction, we developed an Experimental Plan and conducted experiments to measure the effects of process changes.

The Results
We ran experiments for up to five times the normal Hotline volume to determine the impact it would have on the system. We found with a constant increase in reports to the Hotline, the system could handle up to another 50% of its normal volume, with the Program Managers in the FAA Office of System Safety being the most constrained resources.

However, the volume of reports to the Hotline fluctuates with events in thenational airspace system. During the course of the Aviation Safety Hotline Simulation Project, the Hotline was inundated with calls for several weeks following each of two major air carrier accidents: the ValuJet accident in Florida in April 1996 and the TWA Flight 800 accident in July 1996. We used data from these two cases to simulate changes in Safety Hotline capacity resulting from an increase in Hotline reports. We found that, operating at normal volume with an influx of calls at four times the normal volume for one month (the average number received after the ValuJet accident), it would take the Safety Hotline system about the same amount of time, one month, to recover and clear out the backlog.

If the average number of reports received daily was set at one and a half times the normal volume, and the same one-month increase was added, it took four months for the system to recover. At twice the normal report volume, the system would not ever recover following an influx of calls to the Hotline.

The project allowed the FAA Office of System Safety to justify creating another position and maintain a full-time, dedicated Safety Hotline Program Manager position.