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[[image. caotion: THE GRAPH PICTURED above was plotted from the flight recorder readout of a scheduled Caravelle trip which sustained no structural damage. It illustrates: (1) How flight recorder information in recorded; (2) How rapidly the onset of sever turbulence can occur; and (3) The structural integrity of the aircraft. The recorder readout also indicates that there was continuing turbulence between three and five minutes which didn't produce high values of vertical "G" loads possibly because of the reduction in air speed. ]]

I will go into this calibration chart makeup a little deeper later, since this is one of the most important parts of a readout. It may in some cases be necessary to apply a correction for the reference line. We have noticed on occasion that the reference line did not scribe in a straight line. Sine all traces are measured from it, if it is shifting, then all other traces are shifting with it. This is usually caused by tape shift. So sometimes a readout of the reference line is necessary versus time so we will know at any given second how far the reference line was off so it can be corrected. After all these values have been corrected you will wind up with time in minutes and seconds or seconds only depending on the length of the readout. Opposite those values of time you will have what the various parameters were doing at exactly that second. The time and the parameter values are plotted on a chart showing all values in relation to a given time. These plots are reproduced and as soon as possible sent to the investigators in the field as a guide for areas which may need more concentration.

As you can see it takes considerable time to go through a precision readout. It actually takes about a week with 4 people working. Some delay is caused by pressure from those who want a quick and dirty readout. When this is provided all it does is give you information which may or may not be accurate and could be misleading. This adds another day or two to the readout. We are hoping that in the future the committee can work undisturbed until the readout is finished.

Now to describe the calibration, show how important it is, and suggest recommendations for improvement. Without accurate calibration we cannot get from a recorder the accuracy it is capable of or what investigators require. You can talk all day about improving a recorder, but if you cannot make an accurate readout, the whole thing is lost. This is the weak link in the chain. When a recorder goes through overhaul or is sent in for repair, a re-calibration of the recorder is made. This calibration is done to ascertain that all styli are recording within their tolerance. When this i done, most carriers will record on a card the exact values being recorded in the test.

For instance, you may run a test for one minute each at values of 0 - 1 - 5 - 10 - 20 - 40 and 50 thousand feet. These traces are measured to determined how far above the reference line, in  fractions of an inch, they have been scribed. These measurements are recorded on a calibration data card. If these values are measured accurately a calibration chart can be made to read out any value of altitude against any value of "Y" or vertical distance in inches. Some carriers, when re-calibrating a recorder, find a stylus not within

FEBRUARY, 1964 PAGE 7