beachedwhale1945 t1_its0f4l wrote on October 25, 2022 at 9:37 PM

Reply to comment by Bott in TIL that flight recorders must be able to withstand an acceleration of 3400 g for 6.5 milliseconds and that this is roughly equivalent to an impact velocity of 270 knots (310 mph; 500 km/h). by IchBinKoloss

You’re ignoring any connection issues: if the aircraft cannot transmit the data to a satellite for whatever reason, such as it’s actively crashing, then it doesn’t matter how you are handling the data once it’s at the satellite. Even if you have 90% of coverage during normal operations, when planes start failing and the data is most critical the successful connection rate is going to plummet.

This is especially true once you start recognizing the types of crashes. The types of crashes where you are most likely to have connection all the way to the ground generally have few or no fatalities and the aircraft is recovered largely intact, such as the Miracle on the Hudson. In these cases you easily recover the flight recorder and can compare the data to survivor interviews and the recovered wreckage.

The crashes where you want a satellite connection are those where you cannot recover the flight recorder or the extremely rare cases where it is unreadable. These crashes almost by definition have no survivors and no significant debris recovered. For the crashes where you have to heavily rely on FDR data, the aircraft almost always becomes uncontrollable and any high-gain antenna necessary to transmit the dozens to hundreds of data channels (and many are reaching 1,000) would lose connection with a satellite network. When you need the data most, you don’t have it.

About the only time this would have been useful is MH 370. In this case, however, you don’t need to send all of the flight recorder data to a satellite network, just accurate position data at regular intervals. The problem with MH 370 is the search area was so fast we couldn’t find the recorders before their pinger batteries died, but with position data you would drastically narrow the search area and find the recorders and more importantly wreckage quickly. At that point you can use a low-gain omnidirectional antenna, much more likely to function in case of major maneuvers, and even if you lose that data the search area has shrunk dramatically.

Bott t1_its742q wrote on October 25, 2022 at 10:25 PM

Several things. You assume that as a plane is crashing, the datastream fails. Why? Given such, any data are better than none.

Last point regarding rarity of use: How often do flight data recorders get read? RARE instances.

The title of this thread marvelled at the technology of the hardware devices. I'm sure a fraction of that technology could make online flight recorders happen.

mtled t1_itsuf8i wrote on October 26, 2022 at 1:21 AM

Then get to work designing and certifying it.

In the meantime, the next generation of aircraft tracking and distress alerting is GADSS, and more than a few smart people have been working on it. It'll start to be implemented in some countries in 2025.

Feel free to go to the source material at ICAO, read the EASA rulemaking and means of compliance guidance and tell the industry that you're "sure" they could do better.

beachedwhale1945 t1_itvr7oy wrote on October 26, 2022 at 5:41 PM

>You assume that as a plane is crashing, the datastream fails. Why?

Connection issues are common problems for normal operations and should be expected for any such system.
To communicate the volume of data an FDR captures with satellites you need a high-gain antenna with significant power requirements. To reduce said power requirements a directional antenna is best, such as for Starlink. These will naturally loose connection if a plane is no longer pointed up, such as diving towards the ground and especially diving while inverted. This isn’t GPS where the data transmitted is minimal, there is a massive amount of data in an FDR.

> Given such, any data are better than none.

And the cases of no data are practically unheard of. If you can get to the wreck, you can get to the flight data recorders.

>Last point regarding rarity of use: How often do flight data recorders get read?

Every single time they are recovered, with dozens per year as legal requirements push them to smaller aircraft with lower safer standards compared to airlines. You may not read an FDR in case of a bird strike where the aircraft lands safely, but even then removing them is common.

Name another crash in the last decade besides MH 370 where the black boxes were not recovered.

>The title of this thread marvelled at the technology of the hardware devices. I'm sure a fraction of that technology could make online flight recorders happen.

It is far easier to make anything wired function reliably at high bit rates compared to something wireless. Landlines came a century before wireless phones (satellite or cellular). Wired Internet long predates wireless, and most of the global internet passes along undersea cables rather than satellites. A couple months ago T Mobile and SpaceX announced they were going to used Starlink satellites to end dead zones: these require large version 2 satellites too large to fit on a Falcon 9 and will initially only offer text message support rather than real-time voice calls.

You’re asking for something far more ambitious: real-time communication with thousands of airliners in the air every second with high data output from each. Thus would require massive allocation of radio frequencies (which are already limited) and require thousands of new satellites to function (with cheap launches at about $1 million per satellite using Starlink as an approximation, which is far cheaper than most). All to solve a problem that is so rare it has only been an issue for a handful of crashes over the past several decades (we haven’t even discussed how most crashes are within a few miles of an airport).

This could be solved far more easily by a far simpler solution: every five minutes in the air the aircraft transmits its current GPS coordinates. If it goes down, the search area is now small enough that you can easily find the black boxes.

Your naïvety on such problems shows how little you actually know about the subject and engineering in general. A complicated solution for a niche problem almost never sees the light of day.