Smaller Flight Data Recorders
Journal of Aviation Technology and Engineering
Smaller Flight Data Recorders{
Yair Wiseman 0 1
Alon Barkai 0 1
Bar-Ilan University
0 Mr. Alon Barkai completed an MSc of Computer Science at Bar-Ilan University. Mr. Barkai is the Founder and CEO of Ziroon Ltd
1 Dr. Yair Wiseman was a postdoctoral scholar at the Georgia Institute of Technology in conjunction with Delta Air Lines, Inc. He is now with Bar-Ilan , USA
Data captured by flight data recorders are generally stored on the system's embedded hard disk. A common problem is the lack of storage space on the disk. This lack of space for data storage leads to either a constant effort to reduce the space used by data, or to increased costs due to acquisition of additional space, which is not always possible. File compression can solve the problem, but carries with it the potential drawback of the increased overhead required when writing the data to the disk, putting an excessive load on the system and degrading system performance. The author suggests the use of an efficient compressed file system that both compresses data in real time and ensures that there will be minimal impact on the performance of other tasks.
flight data recorder; data compression; file system
Introduction
About the Author
record thousands of parameters for hundreds of flight hours
in flight data recorders or quick access recorders is now
possible. Compression algorithms are used by the
manufacturers and may become even more prevalent with the
introduction of video recorders. New video compression
schemes have a significant compression factor which is
usually some hundreds of times; that is, the compressed file
will be less than 1% of the size of original file
(Horowitz
et al., 2012)
. This means that the compression is still useful,
even though the memory capacity is much larger. This
work has been done relative to hard disks of flight data
recorders, but flash memory developers can utilize the
results, as well.
An ordinary difficulty is that flight data recorders run out
of space on hard disks. The concern of encountering this
difficulty leads one to act cautiously, constantly attempting
to reduce the used data space
(Wu, Banachowski, & Brandt,
2005)
. In addition, working with nearly full disks causes the
allocation of new file blocks to be distributed across multiple
platters. Working with files scattered around the hard disk
drive is slow and very demanding on the read/write head,
with unnecessary overhead
(Ng, 1998)
. However, unlike
flight data recorders, in regular desktops the vast majority of
disks are not overloaded and so it is better to keep old
versions of important files on the disk even though, in most
cases, one will not use the old versions
(Muniswamy-Reddy,
Wright, Himmer, & Zadok, 2004)
.
Data are often processed by embedded systems. In the
embedded computing world and especially in flight data
recorders, it is clear that the storage problem is significant, as
the storage area is hundreds of times less than the storage
space available on desktop computers. In a common
embedded computer system there is an electronic card with
a simple processor that supports a small solid state device
which provides barely 1 to 4 GB of space for the system
files. Usually it is not possible to add additional storage
space such as a hard disk drive or even SD reader because of
hardware constraints, system constraints, size constraints,
and power consumption constraints
(Yaghmour, Masters,
Gerum, & Ben-Yossef, 2008)
. A photograph of a flight data
recorder’s storage device can be seen in Figure 2.
It is difficult to install a full operating system
environment which includes a compilation chain (Tool Chain) and
GUI (X Server) in such a small storage space. For the
purpose of illustration, a basic installation of a Gentoo
Linux distribution with a command line user interface, a
stage-3 compilation tool chain, and its Portage package
manager, without any graphical interface or other packages,
occupies 1.5 GB.
The easiest solution to this problem is removing features,
installing only the essentials, and developing lighter
applications for the embedded cards of flight data recorders.
More profitable solutions include the use of disk data
compression
(Benini, Bruni, Macii, & Macii., 2002; Roy,
Kumar, & Prvulovic, 2001)
. Other devices can use
compression of rarely-used data, or compression of all
data, and expansion only of data needed in run time; but
flight data recorders can assume all the data is rarely-used.
Compressing the data will directly yield more storage space
without losing any information. However, this has a serious
impact on system performance, especially when a relatively
small process is located on the same electronic card that
needs to simultaneously compress the file being written to
the disk while continuing running the other applications
without compromising them. For this reason, embedded
developers usually do not use file system compression in
orde (...truncated)