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Performance exam help

  • rchaps201
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rchaps201 created the topic: Performance exam help

Just came out of performance with 60% :(. if I could just get some help clarifying some things that would be much appreciated.

When the question stated part 91 operations, I applied 30 minute final reserve with no contingency fuel. and when part 135 was stated, I applied 45 minute final reserve and 10% contingency fuel. Was that correct?

With all data entry questions, which included min fuel calculations and pnr/etp distances, I avoided rounding until the last stage of the calculation and then rounded as requested by the question. I don't remember what the exact data was in the min fuel question, but I calculated trip fuel to be 19.18181usg and I then multiplied that by 1.1 and added the allowances/reserves which gave me a figure like 29.6093usg and converted that to kilograms as the answer specified in kilograms. I did the same thing when calculating safe endurance for a point of no return question. I calculated the trip fuel to 20 gallons followed by 5 or 6 decimal places and converted the whole figure to minutes for safe endurance. Is this overkill by me? I always thought that avoiding rounding at the intermediate stage would give best accuracy. I used the calculator for all entry questions and the whiz wheel for the multi choice ones as the answers were far enough apart.

Ultimately the exam was lost for me in the p charts. All of them were fill in (cessna and echo) and I just need someone to tell me if I was doing them correctly. All the questions except one said "given the following" so I used the wind provided, the other was a landing chart that gave me an AWIS and I applied it. (Never seen AWIS given before). The questions wanted max weight or min distance. The winds were usually 40 degrees off the runway so I used the wind component chart in the AIP to find headwind which would give me figures such as 12 or 14 knots which I factored in. I usually use both ends of the runway when doing these questions but if I were to take off/land with a tailwind that strong it would exceed 5 knots so ignored it. If this is correct, was I just not being accurate enough with my lines? or if a tailwind exceeds 5 knots on a cessna chart, do I just factor in a maximum of 5 knots?

the other questions were silly mistakes in 1 markers that I wouldn't get wrong again. I got the classic question I've seen so many posts about: TORA: 1350, displaced threshold: 50m, ASDA: 1400 and clearway: 80m find TODA. I got this wrong, but I think the answer should've been 1480m.

any help would be much appreciated, I found the exam similar to Bob's online exam 4 which I got 84 percent on, but the data entry questions are brutal.
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Gflightyt replied the topic: Performance exam help

Hey mate just want to see why you didn’t calc USG to KILOs before doing the sums?
#2

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  • rchaps201
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rchaps201 replied the topic: Performance exam help

I have no idea why I didn't do that honestly. I'd be working with less decimal places and the intermediate calcs would be easier to keep track of, especially when the questions aren't multi choice.
Cheers
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  • John.Heddles
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  • ATPL/consulting aero engineer
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John.Heddles replied the topic: Performance exam help

(a) I'll leave Bob/Stuart to relate the standard tale so that I don't confuse the issues with practical thoughts.

(b) rounding - perhaps not all that necessary to go overboard with the decimals. That is "precision" but not "accuracy". The usual technique in techo things is to run the intermediate calculations to one (or perhaps, two) more decimals than the final precision you are after. Rounding off to the final required precision has to be done at the final step to avoid an accumulation of error adding up to give undesired poor accuracy, both for exams and in the cockpit. Keep in mind that the good old slide rule is more than accurate enough for this stuff but can't get to anything like the precision you are advocating.

(c) P charts - there are numerous things which can go wrong and result in an answer which is a bit far off the mark. Suggest that you do 2-3 sample questions and then post scans of the working so that we can offer useful comment.

If the tailwind exceeds the maximum included in the POH charts, you can't use that runway on the day. If the headwind exceeds the maximum included in the POH charts, you can only use that maximum figure but accrue a benefit from the actual stronger wind.
was I just not being accurate enough with my lines? Probably, but we need to see the stuff to comment.

(d) why you didn’t calc USG to KILOs before doing the sums Doesn't matter - personal preference considering what the data units are and what units the answer is required in.

Engineering specialist in aircraft performance and weight control.
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