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 Post subject: Definition of Mach-drag regions
PostPosted: Mon Feb 27, 2012 6:47 pm 
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Joined: Tue Mar 10, 2009 6:40 pm
Posts: 67
From the rules I gathered that the player first determines the Mach using the nomograph following the normal output rounding to the nearest value. So, for example, if the value is the line extended from the altitude and KEAS passes closer to 0.90 than 0.85, the Mach is 0.90.

From the written rule on page 5 of the V1.0.00 rulebook I gathered the following:
Quote:
Mach numbers below 0.90 in the game are called Slow.
Mach numbers between 0.9 and 1.0 are called LTD
while those between between 1.0 and 1.1 are called HTD.


While there is no overlap between Slow and LTD, LTD and HTD overlap at Mach 1.0, so I assumed that 1.0 should have the higher drag value (HTD) given that in reality wave drag peaks at Mach 1.

The supersonic values starting at 1.2 and ending at 2.6 appear to cover the specified number and higher, such that if an aircraft exceeds Mach 2.6, it uses the 2.6 drag value, whereas 2.4 covers 2.4 and 2.5... until 1.2 covers 1.2 and 1.3.
By the rules, 1.15 rounds to 1.2 (round all values above Mach 1.1 to the nearest 0.1).

So, given the above, I play using the following:
Mach 0.85 and less are Slow
Mach 0.9 and Mach 0.95 are LTD
Mach 1.0, Mach 1.05, and Mach 1.1 are HTD
Mach number 1.2 and greater is per Mach number on chart or rounded down to Mach number on chart.

So my question: is this correct? If not, what is the correct way to determine Mach and form drag as I need to amend my spreadsheets if the above is not true.


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 Post subject: Re: Definition of Mach-drag regions
PostPosted: Mon Feb 27, 2012 6:59 pm 
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Based on a reply at the airbattle Yahoo! Group, I see the directions in the tutorial supercede the rule on page 5 of the main rulebook:

Quote:
When the nomograph line intersects the colored regions indicating "Slow", "LTD" and "HTD", a player need only record that region name. The numeric values in those regions are unimportant to game play.


While this makes sense, it poses two more questions to me:
1) if the mark falls exactly on the border, which way do you round?
2) is this not an important exception to the Nomograph Outputs rounding rule (which is not noted on the nomograph card)?

I will correct my spreadsheets when I find out the definitions of Mach 0.9, Mach 1.0, and Mach 1.1 as Murphy's law ensures some combination altitude and KEAS will fall on at least one of those exact points, even using floating point numbers :P

It would also be nice to have a finished rule book with no errata that is more complete and correct than the tutorial. i.e. the tutorial should be an example that clarifies rules rather than contradicts them!

Here is the quote from Yahoo!:
Quote:
It is interpreted otherwise.

The color region denotes the separation between Slow and LTD, and the color does not change until it crosses 0.90. See message # 11248. Been that way since the nomograph was designed for Mach; the rule was misrepresented in the book.


This means for game purposes the spreadsheet will use:
Slow = Mach <= 0.90
LTD = Mach <= 1.0
HTD = Mach <= 1.1


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