Aircraft Black Boxes: Flight and Cockpit Recorders

UPSC tested black boxes in Civil Services Prelims 2026. Statement 1 was a trap about light. Statement 2 fits the facts below. Statement 3 is covered in the answer section.

What was the question?

The paper was General Studies Paper I, Series A, Question 44. It was held on 24 May 2026. The question read: “Which of the following statements with regard to Black Boxes used in modern aircrafts is/are correct ?” The three statements were:

• They carry a beacon emitting red light pulses to facilitate underwater detection.
• They record both the cockpit voice and flight data.
• Their memory units are made using either stainless steel or titanium.

The options were: (a) 1 only; (b) 2 and 3 only; (c) 1 and 2 only; (d) 1, 2 and 3.

What is the answer?

Statement 1 is wrong. Statement 2 fits the facts. Option (b), 2 and 3 only, is the only one that holds statement 1 wrong and statement 2 right. So the answer follows by elimination. UPSC’s official key is not cited here. The sources below show only titanium for the memory unit, so they do not prove statement 3 by themselves.

Why is statement 1 wrong?

The beacon sends out a sound pulse, not light. SKYbrary describes it as an ultrasonic pulse at 37.5 kHz every second.

“Black box” is a nickname. It covers the recorders that investigators need after a crash.

Which two devices does the name cover?

• The Flight Data Recorder (FDR) stores flight data such as altitude, thrust and flap settings.
• The Cockpit Voice Recorder (CVR) stores audio from the cockpit.

India’s PIB used both terms when it described the recovery of the Air India Flight 171 recorders.

Can one unit do both jobs?

Yes. The Boeing 787 carries an enhanced airborne flight recorder, or EAFR. The AAIB report says it records a combined stream of flight data and cockpit voice. Both are stored on the same device. This fits statement 2 in the UPSC question.

What colour is it?

Its container is orange. US rules say a recorder container must be bright orange or bright yellow. CNN notes that the bright orange colour of the container and the locator beacon help searchers find it.

How much does it record?

• The CVR on the AI171 aircraft kept two hours of audio.
• A 2008 Flight Safety Foundation paper said the 787’s recorder, as then set up, could record about 2,000 parameters over 50 hours.
• The same paper said the rules of that time asked for up to 88 parameters over 25 hours.
• CNN, in 2024, said recorder data totals “more than a thousand parameters”.

A parameter is one measured item, such as altitude. Sources give different counts, so no single number is fixed.

How many microphones does the CVR use?

More than one. A Curtiss-Wright recorder sheet lists four CVR channels. Three are for the crew. One is for a microphone that listens to the whole cockpit.

A recorder that falls into the sea is invisible and silent. A small beacon fixes that.

What is the underwater locator beacon?

The Underwater Locator Beacon (ULB) switches on when it touches water. It is an acoustic beacon. SKYbrary says it emits an ultrasonic pulse at 37.5 kHz every second. A maker sheet lists the frequency as 37.5 kHz, give or take 1 kHz.

How long does it last?

The old minimum was 30 days. The current standard is 90 days. EASA says the beacon must be able to transmit for at least 90 days. A maker sheet also lists an operating life of 90 days.

How far can it be heard?

The same maker sheet says the signal can be detected at 2,000 to 4,000 yards. That is 1.8 to 3.6 kilometres, based on environmental factors.

Is there a longer-range beacon?

Yes. SKYbrary describes a low-frequency unit at 8.8 kHz. It runs for at least 90 days. Its range is 13 to 22 km. EASA asked large transoceanic aeroplanes to add a long-range device by January 2019.

The memory chips sit inside a tough case. The case is tested hard.

What protects the memory?

The memory sits in a Crash-Survivable Memory Unit (CSMU). UPSC statement 3 says the memory units are made using either stainless steel or titanium. A Honeywell patent is titled “Titanium crash survivable memory unit” and describes a titanium housing. The sources here show titanium only.

What tests must it pass?

Makers say their units meet the EUROCAE ED-112A standard. The makers also give the fire and impact figures below. Honeywell and Curtiss-Wright list the same main numbers.

What is the common mistake?

Both figures need their time. The impact lasts 6.5 milliseconds. The fire lasts 60 minutes at 1,100 °C.

Where do ICAO CVR rules sit?

The FAA notes that updated ICAO CVR requirements are in Annex 6, section 6.3.2.3.

Two names matter: François Hussenot and David Warren. Both worked on early flight recorders.

What did Hussenot build?

Hussenot was a French engineer. He designed recorders that worked on photographs. He joined the Marignane Flight Test Center in 1936. That is where he made his first flight recorder tests. Unlike modern boxes, his recorders were based on photographs.

What did David Warren build?

Warren was an Australian scientist. By 1956 he had built a prototype called the ARL Flight Memory Unit. It stored up to four hours of voice and flight-instrument data. He joined the team that studied two fatal De Havilland Comet crashes. The Comet was the first jet airliner.

What is known about Warren’s family?

Warren’s father died in 1934 in one of Australia’s earliest air disasters.

Was it adopted at once?

No. Australia’s Department of Civil Aviation first said the instrument had “little immediate direct use in civil aviation”. Use came later.

Where does the name come from?

This lesson does not give a source for the name. Do not state any single story as a fact.

The AI171 recorders gave investigators key data.

What happened?

On 12 June 2025 a Boeing 787-8, registration VT-ANB, crashed after take-off from Ahmedabad. The AAIB report lists 230 passengers, 10 cabin crew and 2 flight crew on board. That is 242 people.

How many people died?

The AAIB table shows 12 crew, 229 passengers and 19 “others” on the ground died. That makes 260 deaths. One person on board survived, so 241 of 242 on board died. The 19 on the ground are part of the 260.

How were the recorders found?

There were two combined recorders, one at the front and one at the rear. The rear unit was found on a rooftop at the crash site on 13 June 2025. The front unit was found in the debris on 16 June 2025.

How was the data read?

• Both units were flown to Delhi on an Indian Air Force aircraft on 24 June 2025.
• The AAIB mounted it on an identical chassis, sourced from the NTSB, with cables.
• The rear unit was too damaged for a normal download.

The AAIB did the read-out at its own lab in New Delhi. Reports differ by a day on the exact date of download, so no date is given here.

What did the data show?

The front unit’s ULB was still connected to its housing. The report says the engine fuel switches moved from RUN to CUTOFF one after another, one second apart. This was within seconds of lift-off. The engine speeds then began to fall as the fuel supply was cut off. Lift-off was at 08:08:39 UTC. The aircraft reached about 180 knots around 08:08:42.

Does the report say why?

No. On the cockpit audio, one pilot asks the other why he did the cutoff. The other says he did not. The preliminary report, released on 12 July 2025, gave no reason. PIB said in February 2026 that no final conclusions had been reached.

Who investigated?

The AAIB led, under ICAO Annex 13. The AAIB report calls the US NTSB an accredited representative. The PIB said the aim is safety, not to assign blame.

Where is the final report?

The AAIB told the Supreme Court that a draft final report would be ready around October 2026. The Solicitor General said it would be filed in a sealed cover. The public final report comes only after the international review and consultation under Annex 13. The next hearing was set for 13 October 2026.

Rules are changing because old recorders overwrite too soon. India has also built its own lab.

Why is a longer CVR needed?

Old CVRs keep only the last two hours. The FAA says the NTSB has investigated many accidents where CVR data was overwritten. A longer recording keeps the start of the trouble.

What is the new standard?

• EASA asks for a 25-hour CVR on large new aeroplanes, above 27,000 kg maximum take-off mass.
• EASA gives January 2021 for new aeroplanes.
• The FAA final rule of 2 February 2026 raises the time from 2 hours to 25 hours.
• It applies to future manufactured aircraft in the affected group.

Makers already sell such units. Honeywell lists a 25-hour recorder with a 90-day ULB.

What is India’s own recorder?

HAL makes recorders at Korwa. The DGCA gave it ITSO authorisation for its CVR and FDR in February 2023. The HAL data sheet lists 25 hours of data recording, 2 hours of audio recording and ED-112A compliance.

Where does India read recorders?

The AAIB opened a DFDR and CVR lab at Udaan Bhawan, New Delhi, on 9 April 2025. It cost Rs 9 crore. PIB says it lets the AAIB repair damaged black boxes and retrieve data. It lets the team compare CVR, radar and FDR data. For AI171, the read-out was done in India.

Did other countries help read the AI171 recorders?

Yes, in one way. The AAIB mounted the front recorder’s memory on an identical chassis sourced from the US NTSB.

Exams reuse the same pairs. Then they swap one word.

Which facts should you hold?

• A black box is two recorders: FDR and CVR. Some aircraft combine them.
• The beacon is acoustic: 37.5 kHz, about once a second, with a 90-day standard today.
• UPSC statement 3: stainless steel or titanium. Cited sources mention titanium alone.
• Fire and impact figures need their times: 1,100 °C for 60 minutes, 3,400 g for 6.5 milliseconds.
• AAIB investigates. The AAIB report calls the NTSB an accredited representative.

Who investigates a foreign-built aircraft?

The State where the accident happened leads. The State of Design and the State of Manufacture also take part. For AI171, India led and the NTSB represented the US.

What are the common traps?

• Light versus sound for the beacon.
• FDR versus CVR.
• Warren (modern recorder, 1956) versus Hussenot (photographic recorder).