Questions were raised in recent press conferences with the NTSB concerning the lack of a so-called "black box" in the de Havilland Otter that crashed July 7 in Soldotna, Alaska, killing the pilot and all nine passengers. The black box has attained an almost mythic quality in aircraft crash investigation, but the truth -- and why so few of them are used in Alaska -- is far more mundane.
In fact, there are two boxes for investigators. The Flight Data Recorder (FDR) is generally located in an aircraft's tail section and collects instructions sent to any electronic systems onboard. (Usually for 17-25 hours in a continuous loop.) It records aircraft performance parameters such as the airspeed, flight control positions, elevator and rudder inputs, etc. For example, the Asiana Airlines Flight 214 FDR included more than 1,400 parameters, collected over the length of the entire flight, according to the NTSB.
The Cockpit Voice Recorder (CVR) is the second box and it records the audio environment within the flight deck (or cockpit). It covers four channels and depending on the model, holds as much as two hours of transmissions. The CVR is how investigators know what the flight crew members have said to each other as well as other aircraft and controlling authorities whom they may have communicated with prior to a an accident.
In the U.S. there are different federal regulations governing the requirements for FDRs and CVRs. Determining if an aircraft must carry them is based on on such factors as:
- Aircraft weight
- Engine type
- Number of passenger seats
- Requirement of a two-person flight crew
- Year an aircraft was manufactured
Further, while CVRs are required on some aircraft, FDRs might not be (thus an aircraft could have one type of device but not another). Older or so-called "legacy" aircraft, common in Alaska, are generally exempt from the regulations due to date of manufacture.
A new type of data recording technology, which is an affordable possibility for air carriers or manufacturers that seek to utilize monitoring equipment for their own analysis and safety purposes, is the Flight Data Monitoring device (FDM). This equipment not only monitors basic aircraft information such as attitude and airspeed but also captures images of the instrument panel and audio in the cockpit.
One such FDM device jointly developed between Appareo and Eurocopter is now installed in all new Eurocopter B2 and B3 helicopters, such as the American Eurocopter A-Star 350B3e unveiled recently by Alaska State Troopers. It also was on-board the AS-350 B3 that crashed in March near Talkeetna killing two Alaska State Troopers and their passenger.
According to NTSB principle investigator Clint Johnson, the Talkeetna crash is the first in the country to be "image captured" with this equipment and the data is proving to be "considerably useful" in the accident investigation.
The first prototype of a FDR/CVR was developed by Australian David Warren in 1956. His father was killed in a plane crash in 1934 over Bass Strait leaving only an oil slick and no clues as to its cause. Warren developed a passion for electronics and a desire to uncover the secrets of aircraft accidents in the wake of his father's death.
Australia was the first country to make cockpit voice recording required. Read more about him here.
The term "black box" is used as a metaphor in science and technology for a device whose inner workings are generally a mystery but output is extremely important.
Contact Colleen Mondor at colleen(at)alaskadispatch.com