Trend written by Graham Linsky

Trend is a program that is used to collect and reduce Pratt & Whitney PT6
engine operating parameters. The normalised data is stored as "Deltas" of
ITT, Ng (Engine Compressor Speed), and Wf (Fuel Flow). The program is written
from the "Basic" program offered by P & W some years ago. The original basic
program just determined engine type from ser. No and normalised for cruise
conditions. I have added to this the storing and plotting capability of the
Psion 3a.

INSTALLATION
		The program consist of three files:
				Trend.opa........the only file needed to run program
				41451.odb........a sample of collected data
				Trend.txt........this file
The program is installed as an opa by copying to a \APP\ directory on any
drive and pressing [psion] + [I]. The Twin Otter icon will appear on the
system screen with the word Trend under it. Highlight Trend and press Enter.
The Program will create an \ENGINES\ directory and a file for each serial No
of engine that is processed. If you want to view the graphing capability
to evaluate before entering your own data, you will have to create an 
\ENGINES\ directory manually and place 41451.odb in it.

OVERVIEW
		The basic program was written before the -67(AR) engine used on the
SD-360 300 series aircraft was in service so this type is not covered.
		To make full use of the graphs, the data is automatically scaled. Because
of this if you attempt to view a graph with only one input you will get a
divide by zero error. If you view a two input graph the lines will be just be
full scale diagonals. Of course as the word Trend suggests a large data base
is needed to be useful (see P & W AGTOIL No. 23).

USING TREND
		I anticipated the program being used on twin engined aircraft and since
most PT-6 are on twins it is "twin friendly". That is it takes cruise
conditions once then takes in two sets of engine parameters. the serial No.
input as left engine will be offered as left engine each time more data is
input using the [more] option. The same applies to the right engine.
The DATE is input as a "string" so can be input in any form. There is room
to include information such as compressor wash or component change that may
affect engine performance.
PRESSURE ALTITUDE can be input in short forms 4.5 or 45  will give 4500 feet
a spin off of this is that altitudes below 1400 can not be input. During 
testing of the program, I had a print of interpreted altitude at the top left
of the screen and decided to leave it there as a confidence booster. If this
does not show intended altitude in full press [esc] and try again.
TREND GRAPHS These are scaled to use fully the Y axis so each graph will have
a max and min reading at the limits of the graph. The max, min, and mid
values are shown to three decimal points on the left. There is no need to
attempt to interpolate individual values since placing the cursor on any
part of the graph and pressing either [I] or [A] will give individual
readings of the three "deltas" or an average of the preceding 15 entries.
To DELETE a rogue entry, an obvious misreading of instruments, or an
inputting error, place the cursor over that part of the graph and press
Delete. A Warning dialog will give you a chance to change your mind.

If you are wanting to chart a Dash 7 or, is there another four PT-6 engined
aircraft? just press the more button the cruise conditions will be in the
dialog and not need to be altered just change the serial numbers. If you are
catching up on several days data it might be quicker to go through twice, once
for each wing.
For single engined aircraft (Caravan maybe) exit the program when asked for
the right engine ser No. If catching up on several days data put a fictitious
number for the right engine and press enter for right engine each time it
comes up. This will save you having to input serial number each time. Delete
the fictitious file name from the Psions screen facility.