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FWD Limit question

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jkatz098 created the topic: FWD Limit question

Curious about this question.

I understand why it's the answer, however if you're at 2360kg then the FWD limit is 2400mm as stated by casa. Is the idea that this can still move if you burn from aux or do we need to consider this fwd limit unmovable, because if you do the math's and you're at 2360 and burn from aux you will move fwd outside the fwd limit of 2400mm?
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  • John.Heddles
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John.Heddles replied the topic: FWD Limit question

The question is flawed - probably just due to an inadvertent typographic omission.

I will run up a graphic to show what is what and how the answer should be approached and come back with that tomorrow, time permitting.

The flaw is not quite as simple as you have suggested but you have the basic idea - well done for picking it up.

Engineering specialist in aircraft performance and weight control.
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jkatz098 replied the topic: FWD Limit question

Yeah I definitely understand how it will move forward as the weight it reduced, I did graph it but thought it might be some weird trick question on how well you read the Echo specs.

And of course if you picked a weight above 2360kg then you would remain in the envelope to a point.

Thanks for clarifying though!
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John.Heddles replied the topic: FWD Limit question

I just ran a search check in case this had arisen in the past and it has. My previous comments still apply and I guess the question will be amended once either Bob or Stuart review this thread. How they manage to keep track of everything they have on their plates is rather amazing - that the occasional ball goes through to the keeper has to be an accepted reality.

Refer to the earlier thread at bobtait.com.au/forum/performance/6628-au...-burn-and-cofg#12790

Engineering specialist in aircraft performance and weight control.
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jkatz098 replied the topic: FWD Limit question

Ah well there you go, wish I had seen Bob's reply about his thinking.

Thanks for chasing all that up!
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bobtait replied the topic: FWD Limit question

The question assumed that the gross weight at take-off would be well above 2360kg. I have changed the wording to say "the gross weight at take-off is 2900kg and the centre of gravity is exactly on the forward limit".

Then, as weight reduces, the forward limit moves forward faster than the centre of gravity does. That makes the question valid.
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