*Studying ATPL* MZFM question
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Joined: Oct 2022
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From: Romania
*Studying ATPL* MZFM question
Hello everyone! This is my first time on this forum and I hope I'm posting in the right section.
Currently studying for my ATPL exams and there seems to be a Mass and Balance "situation" that I can't quite understand. If you're willing to help shed some light on the following problem, it would be much appreciated.
According to CAP696 MRJT1 Load and Trim Sheet, upper left section, the Allowed Take-Off Mass has to be calculated by picking the lowest of the 3 values you obtain by making the calculations required. All good until here.
Then there are exam questions that require you to find the extra fuel that can be uplifted by knowing the MZFM, actual ZFM, MTOM, MLM. Example:
MZFM = 2000KG
Actual ZFM = 2000KG
Regulated Take Off Mass = 3000KG
MLM = 2200KG
TRIP FUEL = 190KG
Take Off Fuel = 300KG
The right answer in this case is 90kg.
What first comes to mind is the calculation of the Allowed Take-Off Mass. In this case, the lowest value is limited by the MZFM. MZFM + TOF = 2300 kg. Then, as I see it, by subtracting the ZFM and the TOF from the Allowed Take-Off Mass, there should be NO allowance for any extra fuel. Now comes the part that I can't quite comprehend. They say "MZFM does not limit fuel". Therefore, the calculation that gives the right answer of 90kg would be made by taking into account the LM limited (second lowest) Allowed Take Off Mass of MLM (2200kg) + TRIP FUEL (190kg) = 2390kg. Then, by subtracting the actual take off mass of 2000kg (ZFM) + 300kg (TOM), the answer is indeed 90kg. This really buffles me. Why then is there an "Allowed Take-Off Mass" if I'm not going to consider the ZFM structural limitation and take off 90kg heavier? What does it really mean that MZFM does not limit fuel? By simply subtracting from the given values and leaving ATOM aside, yes, it makes sense. But here it doesn't.
I hope I didn't make it too confusing. And I don't even know if this is the right forum for exam questions.
Feel free to delete it if not allowed here.
Thank you in advance!
Currently studying for my ATPL exams and there seems to be a Mass and Balance "situation" that I can't quite understand. If you're willing to help shed some light on the following problem, it would be much appreciated.
According to CAP696 MRJT1 Load and Trim Sheet, upper left section, the Allowed Take-Off Mass has to be calculated by picking the lowest of the 3 values you obtain by making the calculations required. All good until here.
Then there are exam questions that require you to find the extra fuel that can be uplifted by knowing the MZFM, actual ZFM, MTOM, MLM. Example:
MZFM = 2000KG
Actual ZFM = 2000KG
Regulated Take Off Mass = 3000KG
MLM = 2200KG
TRIP FUEL = 190KG
Take Off Fuel = 300KG
The right answer in this case is 90kg.
What first comes to mind is the calculation of the Allowed Take-Off Mass. In this case, the lowest value is limited by the MZFM. MZFM + TOF = 2300 kg. Then, as I see it, by subtracting the ZFM and the TOF from the Allowed Take-Off Mass, there should be NO allowance for any extra fuel. Now comes the part that I can't quite comprehend. They say "MZFM does not limit fuel". Therefore, the calculation that gives the right answer of 90kg would be made by taking into account the LM limited (second lowest) Allowed Take Off Mass of MLM (2200kg) + TRIP FUEL (190kg) = 2390kg. Then, by subtracting the actual take off mass of 2000kg (ZFM) + 300kg (TOM), the answer is indeed 90kg. This really buffles me. Why then is there an "Allowed Take-Off Mass" if I'm not going to consider the ZFM structural limitation and take off 90kg heavier? What does it really mean that MZFM does not limit fuel? By simply subtracting from the given values and leaving ATOM aside, yes, it makes sense. But here it doesn't.
I hope I didn't make it too confusing. And I don't even know if this is the right forum for exam questions.
Feel free to delete it if not allowed here.
Thank you in advance!
Last edited by Sebastian24; 28th October 2022 at 12:50.
Joined: Jun 2002
Posts: 336
Likes: 15
From: Dubai
The problem is in how you are calculating the Allowed Take Off Mass.
Allowed TOM as limited by MZFM is MZFM + total fuel capacity. In most planes you can't do this because you will bump up against the lower MTOM or MLM limits. In the event that you can then you know you cannot take more weight than you already have on board.
PS the fact that they don't provide total fuel capacity is an indication that MZFM is not a factor.
Allowed TOM as limited by MZFM is MZFM + total fuel capacity. In most planes you can't do this because you will bump up against the lower MTOM or MLM limits. In the event that you can then you know you cannot take more weight than you already have on board.
PS the fact that they don't provide total fuel capacity is an indication that MZFM is not a factor.
Joined: May 2004
Posts: 1
Likes: 0
From: Asia
Start from the MLM ... this is key:
Max fuel you can land with = MLM - Actual ZFM : 200kgs (A)
Extra fuel available with take off fuel of 300kg = 300 - 190 (trip fuel) = 110kgs (B)
Extra fuel that can still be uplifted: (A) - (B) = 90kgs
The above is a matter of logic ... cheers.
Max fuel you can land with = MLM - Actual ZFM : 200kgs (A)
Extra fuel available with take off fuel of 300kg = 300 - 190 (trip fuel) = 110kgs (B)
Extra fuel that can still be uplifted: (A) - (B) = 90kgs
The above is a matter of logic ... cheers.
