Dry Operating Index 737

[WLM]

Hi All
I have been studying the CAA UK Flight Planning Mass n Balance with a correspondance manual, but seem to be missing how to draw the line from the DOI down via respective masses to the TOM. I'm a fling wing flyer having to sit a 737 loading to convert a foreign licence. The local authority base the exam on fixed wing regardless of rotary requirement only.
Can anybody help please
Also how do you calculate the square root of a number?
Thanks

[Send Clowns]

Use figure 4.14 of CAP 696 (get this in front of you, preferably with an example question). First work out the all-up mass, using the left-hand side of the form if necessary, but effectively just adding everything that the aircraft has on board at the time to the aircraft itself, often in practice by adding fuel and traffic load to DOM. Then enter the table on the right-hand side of the form, entering at the top with the DOI as given in the question.

Follow down onto the next line, which is for the forward baggage hold, and labelled "1" at the left. For each 1000 kg in this hold move left as shown by the arrow; this means that each block is 1000 kg, and each small mark is for 100 kg. Move from this point straight down to the next line, labelled "4" and repeat the exercise for the aft baggage compartment, except now the arrow points the other way, and therefore change index to the right.

The next 7 lines are for different areas of the passenger compartment, 0a to 0g. Move straight down each time to the line, then follow the arrow either left or right, each time a full block represents 10 people in that section of the cabin, the index change getting smaller of course towards the centre of the cabin, near to the aircraft's C of G. The centre-most section has no significant effect.

After 0g there is a line for the Fuel index. The fuel index can be found from Figure 4.13. The line is used in the same manner, each small mark representing a fuel index of 1.

From this point follow straight down to intersect with a horizontal line at the aircraft mass, the intersection giving the aircraft C of G as % MAC.

Hope this helps.

Send Clowns
Flight Planning instructor (and sometime flingwing driver, although flying planks at the moment)
BCFT

[WLM]

Thank you so much Send Clown. Now it makes sense and I can get on with the anwers. I was getting pretty irritated trust me. Why the notes did not explain it in the first place is a mystery. Good to see a fellow fling winger helping out ;)
Cheers
WLM

[cumulus]

Other than the lower numbers, square roots are not that readily derived, though I am ready to be proved wrong. Even in the pre-caculator era, people usually derived square roots from tables.

As even the simplest of calculators carry a root function, I cannot see any need to derive roots from scratch, especially not in Aviation.

If I remember correctly, higher value roots are derived using a form of iteration; ie a posh form of trial and error..:ok:

[WLM]

Thanks Cumulus. I think my calculator was very simple, never mind sat the exam today and guess waht, no square root question....Murphy at it again....
Cheers

[Send Clowns]

My pleasure.

Remember that you, as a superior race of people who can actually stop and admire the scenery at will, have to learn the theory to fly both a plank and an egg whisk. That shows the CAA can see the superior capacity inherent in one who flies rotary; in other words, think of it as a compliment :p

On the square roots, if manually calculating, splitting the number into prime factors can help find the answer, as a mathematical aside that need not concern you if you have a good calculator. On that score, find one with a degree, minute and second button (marked [° ' "]) for general navigation and [EXP] and [ENG] buttons to help in radio navigation. Your instructor should be able to show you how these help; if not, ask me.

[WLM]

Send Clown, I detect a bit of humour there :D I don't know if I can fit my head in my current helmet now
Thanks for the help to all
WLM:p