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Cruise pitch

Messages
15
Country
southafrica
Firstly, I do not know much, if anything, about flight dynamics so please be patient with me!
I need to increase the cruise pitch (very slightly)of the CS 757III WITHOUT affecting its clb and des performance. The power (N1) percentages are all correct at crz and I don't want to upset them. I once read somewhere that making a change in table 404 can increase the pitch attitude without messing up other aspects. What, and how, do I make this change in table 404? Or is there another way. Please answer in English and not in Science ;).
regards
Trevor
 

Roy Holmes

Resource contributor
Messages
1,717
Country
us-virginia
Table 404 shows the lift coefficient against angle of attack. In level flight the airplane's nose is pointed above the horizon by an angle called angle of attack. The wing then produces the same amount of lift as the airplane's weight. The lift comes from the wing area and the lift coefficient for that angle of attack.
If you want to have the cruise pitch higher for the same flight conditions you would have to reduce the lift coefficient at those conditions. The easiest way to do that is to create another Table 404 with the lift coefficients say 90% of your original one.
Flight test your original set up at a particular speed, altitude, and weight and note what the pitch angle is. Change the 404 to your modified one and repeat the test.
If the pitch is too great try setting 404 to 95% of its original values.
This procedure will work with FSX and P3D. MSFS does not have a 404 exactly, but it does have an equivalent.
Hope that was clear
Roy
 
Messages
15
Country
southafrica
Thanks for the response Roy. Could you please explain how I create another table 404. Thanks
Trevor
 

Roy Holmes

Resource contributor
Messages
1,717
Country
us-virginia
Trevor,
Since you mentioned 404 I assumed you were not talking about MSFS which does not have numbered tables. FSXA and P3D have numbered tables. Actually the numbering system was not official but when the tables were finally published by Microsoft there was hardly any difference. 404 was officially called CL vs Alpha and the contents of an air file can be found in the P3D SDK.
MSFS has lift_coef_aoa_table, part of the flight_model.cfg and it is essentially the same as the previous versions except it is a text table.
So if you are using MSFS, find lift_coef_aoa_table. Each entry is like 0.139630:0.950000, where the first number is the aoa in radians (about 8 degrees) and the second is the lift coefficient (0.95). The range of aoa is from minus 180 to plus 180 degrees but the bit you are interested is that from about zero degrees to around 15 degrees. Just edit that range by reducing the CL (second) value by say 0.95.

If you are using FSX or P3d the principle is the same but you will need something like AirWizED to modify the .air file.
Roy
 
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