Welcome to the CPL Performance question and answer forum. Please feel free to post your questions but more importantly also suggest answers for your forum colleagues. Bob himself or one of the other tutors will get to your question as soon as we can.
This post came from Andrew as an e-mail and has been posted in the forums for the benefit of other students.
Just have a quick query regarding one of your questions in the CPL performance book. Exercise 5.10 on page 5.40 regarding using fuel as a ballast. The question i want to ask about is the second question. My worked answer was exactly the same as you had in the worked answers, however its the limitation of the main fuel tanks in the echo that i'm wondering about.
If we have to add 68kg of ballast fuel, to the 224 kg of minimum fuel at T/O, this equals 292 kg. However, the max load of the main fuel tanks in Echo is 272kg (100 Gals x 2.72= 272kg)? So we have an extra 20kg of fuel that we can't put anywhere without changing the load once again? Am i missing something here. Thanks for your time.
No you're not missing anything. The first 68kg is ballast so that fixes the balance problem at Zero Fuel Weight by putting the CofG right on the aft limit with the ballast fuel in the mains. When you fill the main tanks the CofG will move well forward into the envelope. The extra 20kg of fuel can now be put into the Auxillary tanks which will move the CofG back but since it is now well inside the envelope that is no problem - you are still safe. Bob