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I'm currently studying my BAK exam. I'm pretty right will all topics but the loading chapter. Does anyone know any 'good' (internet) links on specific, alpha, bravo, charlie loading systems?

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I'm sorry, I don't know of any links. Do you have a BAK theory book? They usually have good information on the systems. Is there anything specific you need to find out?

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I reckon I know a bit about loading aircraft, but have never heard of alpha, bravo and charlie systems.

Hopefully someone will be able to enlighten us.

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OK.

Loading System Alpha uses a graphical type of approach. You enter the BEW, Row 1, 2, 3, baggage weights, fuel etc in boxes on the load data sheet and trace a line left and right for each line, with sections indicating weight in kgs. The line then goes straight down into the W & B envelope. There are different graphs for normal seating and club seating. MTOW is 1633 kg.

Loading system Bravo has weight in pounds, arm in inches, moment is weight x arm in index units. It can be worked out mathematically just by calculating the numbers, or graphically by plotting the weight and moment/1000 inch pounds for lines drawn on a graph for pilot and copilot, fuel, rear seat pax, baggage etc. Then the info is plotted in the centre of gravity envelope at ZFW and TOW. It is a normal and utility aircraft. MTOW is 2200 pounds.

Loading system Charlie is in KG and mm. It is a normal and utility aircraft. It is calculated mathematically, then the ZFW and TOW are plotted on the centre of gravity envelope graph. MTOW is 1115 kg.

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Yes, i have heard lots of 'nice' things about the echo system.:yuk:

Um... how do i explain this? i_dunno I had a theory sesion on the 3 systems, but i didnt get the 'concrete' rules for each system, cos my instructor was re-reading them from a book from when he did them.

The explanations u gave me, are these the ground rules for the 3 loading systems? I was ok with alpha systems, but are weight and moment/1000 inch or weight times moment divided by 1000 always & only used in the Bravo system?

In the Charlie system u said MTOW is 1115 kg, Is this a figure always used in this system, for max take off weight?

Thanks again for this!

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The aircraft are "standard" types so the MTOW, baggage limitations etc will always be the same. Remember the utility category and stay within that if required.

In Bravo the weight is in pounds. If given weight in kg you have to convert it to pounds (and they will almost always give you the wrong type of weight). The Moment arm is in inches, and the moment (weight x arm) is in index units so the numbers are not so big. Index units equal weight x arm divided by 1000. That's it!

MTOW is 2200 lbs (Utility 1850 pounds), max baggage 120 pounds. Empty weight and moment, and oil weight and moment should be given.

A Charlie aircraft is in kg, the arm is in mm, and the moment is in index units which are weight x arm divided by 100. Note that is 100, not 1000. There is no graph to work out the moment (as you can with Bravo), it must be done mathematically.

MTOW 1115 kg (Utility 925), max baggage 122kg.

Yes, Echo. You start of thinking A, B, and C are tricky, until you start doing Echo and long to go back to A, B and C! :hittinghead:

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I did the commercial theory years ago and never heard of A,B and C, but the idea I can understand. It is just a case of re naming something to make it un-intelligible to us old timers.

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• 7 months later...

I'm going through this stuff now and I'm stuck on Charlie. If anyone has the ATC BAK book, it'll allow you to follow along with my confusion easier, hopefully.

Ok, for those playing along at home, page 329 is the question "Load System Charlie - Working".

Basically, it's given me all the info except the load in Row 2. The question it asks is, what is the maximum passenger weight, in kg, that may be carried in row 2 at take off?

The current data, with 0 at row 2 is:

ZFW = 75kg, Arm: 2,927mm, Index units: 25,790

Fuel = 99kg, Arm: 2,950, IU: 2920

TOW = 980kg, Arm: 2,930, IU: 28,710

And they've given a "Ballast to add" formula:

[GW (kg) x distance to move CG (mm)] / [new STA - current STA]

GW = 980

Distance to move = AFT limit - current STA = 3,004 - 2,930 = 74mm

New STA = 3600

Current STA = 2930

Therefore ballast to add = 108 kg = max passenger weight in row 2.

My question is....how did they arrive at the new STA value?

I can't seem to work it out... :confused:

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The "new STA" value is simply the arm of row 2. (see page 332)

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Hey Bas, I'm still a bit lost. You're referring to the tables on the right hand side?

How did they get 3600 using the row 2 table?

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Just a quick note the MTOW weight is not always the same for loading system Alpha or the same for Bravo and or Charlie.

A,B and C are just loading systems that different aircraft will use. So all cessna's use the same system (Alpha) and a Cessna 150 doesn't have the same MTOW as Citation X! Or you can have your own system created by a certified aircraft weigher just to add a few more in there!

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Haha, oh dear, I'm blind. Thanks Bas, I see it now

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If you understand what a moment is and how to find the CG (of anything, not just planes) using just that, any system is easy to understand - just a different (shortcut) way to do the same thing.

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Just when I thought I had it nailed, my instructor tells me that these b'stards are in the PPL exam.... :broken_heart:

Oh well.....

Ben

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Just when I thought I had it nailed, my instructor tells me that these b'stards are in the PPL exam...

But I assume that they won't be blind questions and that you would simply get the charts and a problem you need to solve using the charts, right?

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The loading systems in the exams DO have a constant MTOW etc. They are based on a fictitious aircraft type using systems that are similar to those found in real aircraft. So for your real aircraft, do use the proper charts for that aircraft, and once you have mastered the theoretical loading systems you should be able to do it for the real aircraft.

However for the purpose of the exams, they are standard "types" with standard MTOWs for each loading system. Yes, there will be questions on A, B and C in the PPL exam, no doubt about that. Yes, all the charts/graphs, and necessary arms/moments are provided, you just need to know how to use each system.

(And if you decide to go on to CPL theory one day, just wait until you have to learn loading system Echo!)

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Just a quick note the MTOW weight is not always the same for loading system Alpha or the same for Bravo and or Charlie. A,B and C are just loading systems that different aircraft will use. So all cessna's use the same system (Alpha) and a Cessna 150 doesn't have the same MTOW as Citation X! Or you can have your own system created by a certified aircraft weigher just to add a few more in there!

Whilst the exams may use the "standard" systems and so might some manufacturers, they are simply systems for arriving at an outcome.

Manufacturers can and _do_ use alternative but related systems. What is common to all the systems is that they use a datum point, arms and weights and arrive at moments which move the CG. The allowable CG in turn is almost always expressed as a set of limits which are a percentage of MAC and this percentage obviously can be and is converted to a measurement from the leading edge (generally).

The manufacturer will set an envelope for weight and moment that the aircraft must fall within and if a GA aircraft that envelope will be split into at least normal and utility categories.

The bottom line is that you should be able to work this out from first principles. The loading systems are just ways of getting to an answer.

Interestingly some RA aircraft do not provide detailed CG guidance, instead relying on limiting MTOW and limiting baggage weight - due mainly to the baggage having the greatest arm and fuel, pilot and pax being very close to CG. However other RA aircraft offer good CG guidance, particularly those with generous baggage allowances. If your POH offers CG guidance for RA aircraft you should use that guidance - there's a reason they provide it.

Sorry for the rant - this is a subject near to my heart at the moment.

Regards

Mike