Performance Charts

[TwinOtterFan]

Hey all,

thank you for all the input on manifold pressure, much appreciated as always. I was hoping that in between all the Covid charts we could bring up a few Performance charts?

Lets go with a Cessna 172P take off distance chart for example. and use CZVL as the airport with a Alt of 28.57 and a temp of plus 7c CZVL is 2256' elev.

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in particular I was wondering what everybody does for interpolation of data? I am told that the linear interpolation formula is the way to go but I find it overly complex, is there a better way?

If I am understanding it correctly it would be something like this?

PA 29.92 - 28.57 = 1.35*1000 = 1350 + 2256 = 3606

So is this what you all use? I'm not going to lie it seems really overly complicated for what I am after.

Y = Y1+(X-X1)*(Y2-Y1)
(X2-X1)

Sometimes I feel like the reason the average flight hours to PPL are so much higher is because they have overly complicated a lot of this....

[Big Pistons Forever]

Round up to the next line, ie the next higher temp and altitude.

[TwinOtterFan]

Round up to the next line, ie the next higher temp and altitude.

Agree completely, especially since the Cessna chart was made on a brand new airplane in perfect conditions with a certified test pilot, but that doesn't help me with the written exam.

[TwinOtterFan]

Okay so not sure if this is right or not, and yes I understand that normally you just round up but the written exam answers to choose from are all very close together.....

So I think if I use the 3606' and get a length for 0 degrees and 10 degrees and then use those two lengths to then figure out 7 degrees? does that make sense?

My math (sorry it is messy, I'm holding a new born while a 6 year old pesters me......)

273203057_1297834130692865_1269889171227250277_n.jpg

273181632_2152256374931229_7736319965078193926_n.jpg

[Colonel]

My experience in a quarter century of recommending candidates for
TC pilot written exams, was that triple interpolation was an essential
technique to obtain the correct answer.

Yes, this is significantly divorced from reality, esp for a 50 year old
airplane.

Written by salesmen for bureaucrats, reviewed by howling lawyers,
to be considered as the God's Truth by impressionable young pilots.

Keep in mind that the same document says that an average pilot
can land a 172 with 15 knots of direct crosswind. Uh huh. A new
Canadian CPL might struggle with 5 knots of crosswind.



That guy is probably right seat on an RJ now.

[Big Pistons Forever]

2 Otter

The PPL exam has a best a very tenuous connection to what actually matters as a pilot. The objective is to pass the exam. What mark you get above the minimum required is of absolutely no consequence.

Interpolation is negative training as the rigour of the charts do not support that level of precision for the reasons stated above.

So my recommendation and it is worth exactly what you paid for it is to calculate the actual DA which is a simple addition and subtraction and then write down the 4 takeoff run numbers. That is for the altitude above and below your calculated DA and the temp above and below the given value. Estimate the difference and then compare the answer choices. Pick the one that looks the best. If you spend more than one minute on this you are wasting your time.

[Colonel]

This is just my opinion, but ...

Having written more than a few TC pilot exams - and recommended a few
others to do the same ...

My observation is that for some odd historical reason, TC pilot written exams
are more of a test of reading comprehension and language knowledge. When
I wrote my FAA ATP, it was hard to stop laughing. Three answers - not four - and
really simply worded compared to the pedantry of the TC writtens.

FAA written exams are much more of a test of your aviation knowledge. Done
in 20 minutes, I think I got 80% on the FAA ATP? Oh yeah, back in the 90's I wrote
the FAA IFP so I could get an FAA COMM-SMEL-IA. Meme chose.

What really frosted my cookies was the foreign pilot puppy mills that were
popular a few years back in Ontario. Those pilots couldn't speak a word of
English on the radio, but their mastery of the English language far exceeded
ours - they always aced the writtens. Why was that?

It was nice when TC stopped expiring the instrument rating. I think I wrote
the INRAT three times, over and over again over the decades, because I would
let it lapse, and then get it back again. Doesn't matter much now, of course.

[Squaretail]

2 Otter

Pick the one that looks the best. If you spend more than one minute on this you are wasting your time.

Also keep in mind that with these tests of the four answers, two will be really out. Of the remaining two answers, if you are pressed for time remember you got a 50/50 chance. The answers will also be concocted to catch the most obvious errors. For example two of the wrong answers in this question will probably be if one didn't interpolate and took the worst or best figures. TC also likes to play the units game, so if you see two answers with the same number, but different units -one in feet the other in meters for example - the correct answer is one of those two.

If you have to guess, remember the pilot is always responsible, the minister can approve anything, and when in doubt pick the longest answer.

[Slick Goodlin]

Sometimes when studying I come across a topic where all I can do is try my best and accept that if this question comes up I’ll probably get it wrong. I’ll just try harder on the other 79.

[Colonel]

One thing that's nice about the FAA writtens is that the questions are all
public knowledge, and you can buy these nice books with the answers.

So if you want to, you can memorize the test.