Here is another question on black (CVR/FDR) boxes?

Question

I have read several NTSB reports where the Black box had "no data" recorded. In two cases the FDR did have information, but the CVR box was relatively undamaged, yet the tape was blank, in one case the CVR has (had) a switch that was acutally open, and had erased ALL the recordings on the tape. Is the tape checked daily, monthly during 100/300 annual MX checks? Or are there special tech's that remove and goes over the CVR/FDR to ensure functionality?. I know that they are well protected, but is there easy access to them? I would assume this would be, in some cases, the only way to see what happened to the aircraft that crashes with no last radio call, or over the ocean etc.. (I am speaking here of Commerical/Military aircraft, that by FAA regulations, require such recorders). Thanks,

Answer 1

The CVR and FDR aren't considered essential for operating the aircraft, or at least they didn't used to be, so taking off on the final flight with a broken one was quite common. The old devices used a wire, not tape, and after years and years of opperation the wire would often break and it would go unnoticed for a while. Then there's the problem that incidents which don't end in a crash often go out of the recording frame of older FDRs and especially CVRs, so by the time the crew landed the aircraft the data had all been recorded over on the loop tapes.

Normally you don't remove them, they just sit there recording endlessly until something goes wrong.

The FAA does not regulate military aircraft and in any case can't mandate what they must do. In the UK it's a bit different because the AAIB, which makes the recomendations on air safety, is/was actually part of the MoD (AAIB was at RAE Farnborough). Older military aicraft had no recording equipment, in the UK that just started coming in with the Tornado. The military doesn't really like the idea of anything useful to an enemy surviving the loss of an aircraft, but they got over it with the help of cryptography and the necessity of knowing what their aircraft had been up to. On the video recordings we made in Tornado cockpits they noticed that the pilots were strapping in wrong and would have prevented the ejector seats functioning properly, that probably saved a few lives.

Modern digital recorders use solid state devices, Flash memory or EEPROM as we used to call it (Flash is an Intel trademark), so there's no tape to break, or inspect. But the box would tell the aircraft systems if it weren't able to record the data properly and that would be flagged on the maintenance systems and the flight systems. The memory devices are encased in resilient and fire resistant material within the recorder casing, so even if the casing is trashed the devices usually survive. In extreme situations the individual devices can be read when the board they were on was trashed.

The boxes are usually in an equipment rack near the tail of the aircraft so that they get a soft landing in a crash, the rest of the plane provides them with a crumple zone. They are easily accessible during maintenance. Unless something has changed they are what's known as ARINC-404 "ATR" boxes, they have a couple of catches at the front and can be swapped out in minutes.

If they fall in the ocean they have a beacon which allows them to be found with listening devices, but the deep ocean is very large and very deep and these things don't float, so if a 747 turns up missing in New York one day it's going to be difficult to know where to start looking for the black boxes.

Answer 2

There are different types of FDR/CVR's, newer ones are digital. The older CVR's had a looped 30 minute tape.

There is a switch in the cockpit to erase the whole tape. There is also a circuit breaker that can be pulled to stop the CVR from recording. At one place I worked, the policy was to pull the circuit breaker when the flight crew left the flight deck. It's possible for the next crew forget to reset the breaker.

It's up to the airline as to the checks. There is a "test" button on the CVR panel in the cockpit. Some require it be tested every flight, some don't. All are required to test/inspect the CVR and FDR annually and calibrate if necessary every 5 years.

They aren't difficult to access and remove but they do need special tech's and equipment to read, decode and inspect them, some airlines contract another company to do this.

There is also the QAR quick access recorder that records several parameters of the planes flight. It's used for maintenance but can be used to find out what happened in a crash. But it records to a tape or disc in an unprotected box that's actually black.

These are actually better maintained and checked than the FDR/CVR's because the airline can look through the info for any anomalies and prevent potential problems or what caused a current problem.

Answer 3

In major airlines, flight crews don't pull circuit breakers unless it is part of an emergency procedure. A broken CVR does not ground the airplane. It is on what is called a minimum equipment list (MEL) that allows the airplane to take off on revenue flights with certain items inoperable. Th CVR can be inoperable provided th FDR is working and the CVR is repaired within 3 flight days.

All systems are checked within FAA prescribed periodicity. That's how most inoperative or degraded systems are found.

It is also possible for the cockpit crew to erase the CVR tape. The cabin door must be open, the parking brake set and you push and hold the erase button on the overhead panel.

Answer 4

Dunno about all A/c but some CVR's record the past 30 mins in a continous loop. So, if nothing was said for 30 mins, then the tape would be empty. But that's got to be rare, such as a mid-air collision without any warning.

Answer 5

ok claims they do no longer collide - curiously she did no longer examine the articles she provided. unusual. -=- it may be pronounced that maximum "collisions" between products that are gravitationally sure would be misses, no longer hits. Misses effect in orbits. of course, the two products orbit the barycenter (center of mass) of the mixed device. In different words, except you hit the bull's eye you get a binary device. And provided that one mass is plenty bigger that the different will you get one seeming to orbit around the different, otherwise they the two orbit their trouble-free center. besides, all orbiting products provide off gravitational waves (so the belief is going, alongside with some info that seems to substantiate it). meaning that they lose potential and so their orbits will finally merge (to no longer say this is going to happen each time quickly, it ought to take trillions of years). Black holes provide off different gravitational potential (lower back in accordance to thought) so 2 black holes in a binary orbit will merge faster extremely than later. There are no longer any good orbits for them (good = on the order of billions of years). So, maximum collisions would be close to misses which except their velocities are extremely severe will effect in a binary device which will finally merge. -=- it extremely is hypothesized that different the Gold interior the Universe is from the merger of black holes or neutron stars. (unlike maximum factors with atomic selection greater desirable than iron which come from supernovae.) (see Nucleosynthesis.)

Answer 6

pilots have erased them or they are faulty??? the next great american conspiracy??? lol