Airplane's black boxes are crash-resistant but not indestructible. The black box is designed to withstand extreme conditions like high temperatures, impacts and water immersion. The black boxes for the two airliners that hit the World Trade Center on 9-11 were destroyed and never recovered. The recorder's memory module is now required to withstand a penetration force produced by a 227 kilograms weight dropped from 3 metres, a static crush force of 22.25 kN applied for five minutes, and an impact producing a 3,400-g deceleration for 6.5 milliseconds.
Expert behind this article
Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
Are airplane black boxes indestructible?
No, black boxes are crash-resistant but not indestructible. Flight data recorders and cockpit voice recorders are designed by GE Aerospace and Honeywell to be nearly indestructible, yet they are destroyed by impact beyond design strength, by concentrated fire beyond design strength, or by high-pressure water at depth. The units installed in the two airliners that hit the World Trade Center on 9-11 were destroyed and never recovered, and some units have been crushed into unreadable pieces or lost in deep water.
A plane's black box may be destroyed under certain conditions. Although International Civil Aviation Organization regulations require the recorders to survive severe aircraft accident conditions, black boxes are sometimes destroyed by impact higher than design limits, by fire, or by water immersion. Even though Hamilton notes that both recorders have rarely been damaged to the point of yielding no useful data, cases exist where only the flight data recorder was found while the cockpit voice recorder was not, or where neither was ever recovered.
How are airplane black boxes so strong?
Black boxes are strong because they are double wrapped in strong corrosion-resistant stainless steel or titanium, and the outer casing is itself corrosion-resistant. This shell encloses a 1-inch layer of high-temperature insulation made of dry-silica material, while the memory boards storing the data are wrapped in a thin layer of aluminum. To earn certification, the recorder's memory module must withstand a static crush force of 22.25 kN (5,000 lbf) applied continuously for five minutes, an impact producing 3,400-g deceleration for 6.5 milliseconds, and penetration by a 227 kg (500 lb) weight dropped from 3 m (9.8 ft). It must survive fire at 1,100°C (2,012°F) for 60 minutes, float on water, and allow an underwater locator beacon to transmit an ultrasonic ping for 90 days.
