Why does an aircraft's underwater locator beacon only last for ~30 days after the plane crashes? How is the beacon's "pinger" powered? What would be the technical difficulties with extending the lifetime of the beacon's pinger?
The Cockpit Voice Recorder and the Flight Data Recorder are fairly simplistic boxes capable of recording essentially all telemetry and voice communications on the aircraft. If the aircraft crashes in water, the underwater locator beacon is activated, and will continually "ping" until its battery dies.You could certainly fit a CVR and a FDR with bigger batteries, but to what end? Do most searches take longer than 30 days? Is this a constant problem (beacons running out before they are found)?The answer is that most searches are very short and are concluded in a much shorter timeframe than 30 days. 30 days is a very generous number for a search.Plus, any change you make to any aircraft system is very heavily regulated, and would be made in an industry which has some of the thinnest profit margins of any industry. In 2012, Forbes published a study that said that airlines make a grand total of $4 in profit per passenger. Any changes that would cut into that profit are going to be very heavily scrutinized.EDIT: Since the late 90s, military aircraft have been fitted with a second set of CVDRs (combined cockpit voice and data recorders) that are "deployable" and "eject" from the aircraft just milliseconds before impact, will float on water, and contain an ELT (electronic locator transmitter) which transmits its location to satellites. Congress has been unable to pass the legislation to implement the new system, which would be covered by taxpayers, into commercial aircraft. The SAFE (Safe Aviation Flight Enhancement) Act was re-introduced in Congress following the MH-370 incident, highlighting the limitations of the current system.
Why do aircraft underwater locator beacons' pinger batteries only last 30 days, and why are the beacons not tested to ocean depths of 16,000 feet?
First part has been answered already:Why does an aircraft's underwater locator beacon only last for ~30 days after the plane crashes? How is the beacon's "pinger" powered? What would be the technical difficulties with extending the lifetime of the beacon's pinger?I am not certain about testing individual beacon brands, but I'm certain that any limitation on testing is due to cost.Based on their specifications, a 37.5 kHz (160.5 dB) ULB can be detectable 1–2 kilometres (0.62–1.24 mi) from the surface in normal conditions and 4–5 kilometres (2.5–3.1 mi) in good conditions. A 37.5 kHz (180 dB) beacon can be detected 4–5 kilometres (2.5–3.1 mi) in normal conditions and 6–7 kilometres (3.7–4.3 mi) in good conditions. A 10 kHz (180 dB) beacon can be detected 7–9 kilometres (4.3–5.6 mi) in normal conditions and 17–22 kilometres (11–14 mi) in good conditions.So even the shortest range beacon can be detected at almost 16,000 feet under good ocean conditions.
Why don't they make "black box" flight recorders so they float?
air france crash - recorder is at bottom of sea <
Why arent black box recorders designed so they float to the surface of water?
For starters, the flight data recorder is securely bolted down so that it does not come lose in flight and bashes itself around, causing damage. Now, assuming that the plane crashed at sea and sank, how would the recorder unfasten itself, and find its way out through whatever part of the airframe that is above it (and that can be the floor, debris can tumble around) to float up? Assuming that it would not have its flotation system damages, or get tangled with debris in the first place. If the recorder was to float away, then it is also likely to drift away. The wreck remains there, and the recorder drifts miles and miles away, making recovery even more difficult? (The little beeper that is supposed to help locate the the recorder will not emit a sound that can be picked up as far if it is on the surface; moreover, the "ping" of the recorder could thus no longer be used to help locate the wreck.) Crashes at see are very rare occurrences, as most crashes happen during the takeoff and landing phases, so above ground, close to the airport. A floating FDR is very unlikely to impact significantly in the resolution of the cause of a crash, and the added complexity and possible failures will make it more likely to cause problem than to solve them.
While looking into Flight Data Recorders, I came across a part that has me very confused.?
The Underwater Locator Beacon operates at a very high frequency of 37.5 KHz, this is confusing for multiple reasons. 1. This is not in the audible range of the Human Ear, meaning it will require special equipment to even detect it even if a vessel or diver is directly over it. This can prevent many additional resources from assisting in finding the Data Recorders, simply because they may not be able to detect it. 2. The higher a frequency, the higher the transmission loss of range (mostly by attenuation, or transfer into heat). This means VERY short detection ranges so short in deep water the transmission may not be detectable unless directly over top the beacon, and in poor acoustic conditions, not even then. 3. The higher the frequency, the more the sound will be refracted, and in many environments in the ocean, this refraction is towards the Deep Sound Channel axis(which is very deep), or towards the bottom, not many environments have acoustic conditions that refract sound upwards. 4. The source level is only about 160 dB//1 micropascal, this is the equivalent of 99 dB in the air, this is not very loud, especially for a source that has to fight through 1-3 above. 5. Modern Submarine distress beacons are low Frequency, audible to the human ear, are battery operated, very compact overall [compact enough to fit into a medium lunch bag if broken down and have long life spans (hundreds of hours).
What kind of equipment is required to detect airplane black boxes underwater?
At the most basic level, you need a passive sonar system (meaning a hydrophone) that listens to the right frequency and is sensitive enough to detect it at a distance. Currently most airline black boxes have a pinger that transmits at 37.5khz so you need a hydrophone in your sonar that is optimized to listen to that frequency.Unfortunately, 37.5khz is really not the ideal frequency as it doesn't propagate over particularly long distances and the largest rapidly deployable acoustic sensors (sonobuoys) are not optimized for that frequency (they are optimized for frequencies put out by submarines). Following the missing Air Malaysia crash, there was some discussion about changing the international standard to a difference frequency and a longer duration pinger but the effort has a lot of detractors pushing against it for various reasons. Bottom line - you need an underwater hydrophone that can pick up a 37.5khz ping....
Why don't they put some tracking device into the black box of the airplane?
Why don't they put some tracking device into the black box of the airplane?There IS a tracking device, the Underwater Locator Beacon (ULB) or underwater acoustic beacon, on the Flight Data Recorder.There also are Emergency Locator Transmitter (ELT) units installed in the tail sections of airplanes, to transmit radio signals that are detected by satellites and then located by aircraft receivers.How is an aircraft's black box constructed to withstand a crash? What materials are used, design principles employed, placement, etc.?
If the plane's black box battery dies, does it mean all the data stored in it vanishes as well?
Thanks for the A2A. The "black box" is actually two boxes known as a Flight Data Recorder and a Cockpit Voice Recorder. Both devices record the information they receive on solid-state storage media, like flash drives. The FDR records "telemetry" information, such as the aircraft's location and "attitude," how it was positioned in the sky, as well as the settings for all the controls and control surfaces (flaps, ailerons, rudder, etc). The CVR records all voice conversations, whether they were broadcast over the radio or not. While the aircrew is not keying a radio, their headsets and mics are always on, and they can talk in a normal tone to each other over the noise of the engines. Those conversations are continually recorded.As you can see, the box has an underwater locator beacon attached to the outside of it, which will ping for as long as its battery still has charge, so that it can be located underwater. When a plane crashes in water, essentially a big microphone is placed in the water, listening for that beacon's "ping".