B-737 Loading

[FuelFlow]

I was wondering what a good T/O MAC would be for a 200ADV.

There seems to be some confusion with our operation, with a lot of different ideas coming up. On tech school we were shown a MAC of 21%(5 units) would be ideal.

The problem seems to arrive with the amount of centre tank fuel loaded. I was thinking that with 11.5 tonnes of fuel, and 100 pax, it would be better to get a T/O MAC of 17%(5.8 units). With the burning off of the centre tank fuel, the C of G should move forward, and then reaarwards with the consumption from the wing tanks. If landing with lets say 5 tonnes on board, the landing MAC should be around 21%(5 units)wich I am led to believe is what we are looking for. To achieve this situation, it is required to load the most of the baggage in the forward hold, and the spillover in the rear hold.

Can anyone comment on this please??

The argument that is coming up, is that the heavier the rear of the A/C is, the more fuel efficient it becomes. It seems to me that on the 200, the more weight you put at the rear of the A/C, the closer you get to the forward limit of the envelope.

Any info will be appreciated.

Thanks FF

[Juliet November]

FuelFlow,

Was thought more or less the similar loong tome ago. But in the real world, it is not often that we have the time to aim for the "perfect MAC" if we want to protect turn-around times and load all the freight. So the general rule seems to be (for a computer generated l/s) "If it prints, it flies". But then again, we're only dealing with medium- or shorthaul routes and so cannot save many a penny by a tailheavy load.

However, I'm a bit concerned if your system moves the CG forward as you but weight in the rear of the a/c.

[FuelFlow]

Thanks JN

Sorry for that, I should have put that the more weight in the back, the closer you get to the aft of the envelope. Unfortunately, we are on non-computerised loadsheets, and I agree with you that on these shorthauls there is no saving. Just trying to make a point to Flt ops.

Thanks again FF

[FuelFlow]

Sorry again.

I got a bit mixed up with the original post.

With the burning of the centre tank fuel, the C of G should move rearwards, and then initially forwards with the burning of the wing tanks.

The rest remains unchanged

Cheers FF

[Icarus]

Hmm.
Should not one be (if we are talking about an ideal trim) aiming for a particular STABTO value rather than %MACTO?
For a given Laden Index TOW the %MACTO will vary according to the aircraft weight and therefore would be at different positions under differing weights and therefore affect economic flight.
Isn't the idea to ensure that the C of G is aft of the Centre of Pressure so that less STAB TRIM is used (thus decreasing drag) to stabilise (balance) the aircraft in flight.
The STAB value being determined through %MAC values at the particular weight of the aircraft.
So if a particular STABTO (a constant)induces less drag, then as the weight would also be a constant in one example, the variable is %MACTO.
Therefore as one cannot sensibly aim at a moving target (%MACTO), it would be wise to target a STABTO value instead and not worry about the corresponding %MACTO value.

In my experience most Boeings like a 4.5 STABTO value.