UPSC Prelims 2026 Q44: Aircraft Black Boxes — Explained
Which of the following statements with regard to Black Boxes used in modern aircrafts is/are correct?
1. They carry a beacon emitting red light pulses to facilitate underwater detection.
2. They record both the cockpit voice and flight data.
3. Their memory units are made using either stainless steel or titanium.
- 1 only
- 2 and 3 only
- 1 and 2 only
- 1, 2 and 3
Answer: (b) 2 and 3 only
Statement-wise explanation
- 1: incorrect — The locator fitted to a black box is an Underwater Locator Beacon (ULB). It sends out sound, not light. When it touches water it switches on and emits an ultrasonic 'ping' at about 37.5 kHz, once per second, which ships pick up with sonar or hydrophones. Light carries only a few metres under water, while sound carries much farther, so a red-light beacon would be useless at crash depths of thousands of metres.
- 2: correct — A 'black box' is the common name for the aircraft's flight recorders: the Cockpit Voice Recorder (CVR) and the Flight Data Recorder (FDR). The CVR records pilot speech, radio calls and cockpit sounds. The FDR records parameters such as altitude, airspeed, heading and control inputs. India's AAIB 'Black Box Lab' is formally called the Digital Flight Data Recorder and Cockpit Voice Recorder (DFDR & CVR) Laboratory, and it analysed both kinds of data after the Air India AI-171 crash in 2025.
- 3: correct — The data sits in a Crash-Survivable Memory Unit (CSMU), which is cased in strong, corrosion-resistant stainless steel or titanium with high-temperature insulation inside. This armour lets the unit survive an impact of about 3,400 g, fire at about 1,100 °C, and water pressure at a depth of about 6,000 m.
How to eliminate
You can solve this with basic physics plus one fact. Light fades within a few metres of water, which is why submarines and ships use sonar. Any device built to be found at the bottom of the sea will use sound, so Statement 1 should feel wrong straight away. That rules out every option that contains 1, and only '2 and 3 only' is left. You do not even need to be sure about Statement 3. Fact to remember: the black box beacon is an ultrasonic 'pinger' at 37.5 kHz, and the box itself is painted bright orange.
Know more
Flight recorders ("black boxes") are crash-protected devices that store what happened on board, so that investigators can work out why an accident occurred. Most airliners carry two: the CVR and the FDR. Some newer aircraft, such as the Boeing 787, use combined units that record both.
| Feature | Detail |
|---|---|
| CVR | Cockpit audio: crew speech, radio calls, alarms, engine sounds |
| FDR | Flight parameters: altitude, airspeed, heading, acceleration, control positions |
| CSMU | Crash-Survivable Memory Unit, cased in stainless steel or titanium with insulation |
| Survivability | About 3,400 g impact, about 1,100 °C fire, pressure at about 6,000 m depth |
| Locator | Underwater Locator Beacon: ultrasonic ping at 37.5 kHz, set off by water |
| Beacon life | Older standard 30 days. Raised to 90 days after the Air France 447 search (2009) |
| Colour | Bright 'international orange', not black, so searchers can spot it |
| Location | Usually in the tail, which tends to suffer the least damage in a crash |
Why sound, not light? Water absorbs light within a few metres. Sound travels for kilometres. So the beacon is located with sonar or hydrophones.
India's capacity: In April 2025 the Aircraft Accident Investigation Bureau (AAIB), which works under the Ministry of Civil Aviation, opened a DFDR & CVR Laboratory (the 'Black Box Lab') in Udaan Bhawan, New Delhi, at a cost of ₹9 crore. It can repair damaged recorders and download their data. After the Air India AI-171 crash in Ahmedabad on 12 June 2025, the crash-protection module and memory module of the front recorder were recovered, and the data was downloaded in this lab. Earlier, recorders often had to be sent abroad for decoding. Investigations follow Annex 13 of the ICAO Chicago Convention (1944).
In the news
Air India Flight AI-171, a Boeing 787-8, crashed in Ahmedabad on 12 June 2025. In the following weeks there was heavy news coverage of its two black boxes being recovered and decoded in India for the first time, at AAIB's new Black Box Lab, which opened in April 2025.