I made the same error when doing quickly for the first time.

However, after doing slowly, I found an error at the very beginning, between 1st press.height/temp chart and 2nd toda chart. In first chart 4.5mm is the distance from 2nd vertical line in press.height/temp chart and intersecting 25C diagonal line. The same 4.5mm is the distance between 2nd vertical line in toda chart above and intersecting 900m diagonal. The resulting line overlaps the 3rd horizontal line from the bottom of toda chart, then goes straight from the 2nd (long dry grass) onto the level slope chart which intersect level diagonal at the 2nd vertical line from right. Then going down overlapping the 2nd vertical from the right and goes down and intersect 4th horizontal line from the bottom of the tow chart which is actually 1000kg.

To summarize, if you try going from 1000kg backward, you will find the error you made at the first attempt.

As many things in aviation, a small mistake at the beginning, can have serious consequences at the distance..

Hope I help.

G'day Bosi72. Thanks for your reply! I've done this on the computer now and I still get the same number... Can you take a look when you get a minute?

Meade
[attachment=1574]towc.jpg[/attachment]

What was your climb weight limit, again ? I don't recall seeing it mentioned in your first post .....

The correct answer is 1000kg, I can only seem to get 1030kg. I can only work off the info given in that question.

I'm giving you a hint but you are not seeing it ....

1030kg is fine but it is only half of the answer to be considered. You must ALWAYS check for a climb-limited takeoff weight for this aircraft. All the information is there.

Looking at the sample use of the chart -

(a) the runway-limited weight is around 1010kg shown as A

(b) the climb-limited weight is around 1085kg shown as B

The lesser of the two (in this case runway-limited takeoff weight) is the answer required.

Now, again, what was the climb-limited weight for your exercise ?

If you can't quite see it, we will work it through step by step so that it all becomes clear ...

In essence, you are not using the chart correctly. Perhaps a quick review of the notes in Bob's book would assist ?

Thanks John
Explanation is on page 205. I thought the line follows the climb weight limit at the end, but it actually goes from intersection of cwl and "our" line.
Cheers
Stjepan

Ah John! You have all those titles in your name for a reason! I have been neglecting that side of the chart completely! Thank you for pointing that out, much appreciated (with only days to go I might add)

Meade

Good to see it's now under control.

Stjepan - glad we have that minor point of confusion resolved, now.

Meade - for this aircraft and this question, you are climb-weight limited. That is to say, it doesn't matter how long the runway is, you can't use the runway limit weight because the aircraft will be staggering once you get off the ground ...

It can be a bit confusing when you are starting out due to the fact that the old DCA-style P-chart combines two totally separate performance charts as overlays (solely for real estate convenience - ie to use less area on the bit of paper so that the chart detail can be made larger). It is easier if you start out with the charts presented separately so that there is no confusion. However, you need to run BOTH sets of calculations EVERY time for this aircraft and then see which gives the lower weight which then becomes the limiting weight for the occasion.

As a sideline note, Bob refers to the DCA format as "Cessna" charts for administrative convenience. It doesn't really matter what one calls them. There is a range of styles used in presenting takeoff and landing data, including the two typical sorts of presentation you see in this training arena.

All you needed to do in your (very nicely done) example is run up the density height line to the climb weight limit overlay line (at around the intersection of 6000 ft Hp and 10 deg OAT) and then run across to the right to read off the climb weight limit at around 1000 kg (similar to the example line at B in the base chart).

Keep in mind that some aircraft are NEVER climb limited while some are climb limited some of the time (generally for hot and high conditions).

On another point, you will occasionally be asked what the climb capability is. Such questions generally are unanswerable unless you are right on the climb weight limit (in which case you can assume a climb capability of 6% gross) or qualify your answer along the lines of "greater than xx%" where xx% (or whatever equivalent value is sought) relates to the underlying basic 6% requirement.

The climb requirement thing is made a little more obscure as it was specified in the old (and post-Yates Report binned) CAO (ANO) 101.22 certification requirements. All that remains is the CAO 20.7 operational requirements which often (but incorrectly) are assigned certification significance.

Thanks again for your help fellas, I sat the exam this morning, 56 out of 56!

Congrats and Well Done Meade !
How close was the Exam prep question bank compared to real CASA exam ?

Also a question for John (or anyone else). I am trying to find a copy of TOW / Landing charts for the Cessna 172N which I am currently flying on as a student pilot and the pdf from the school looks like 10th copy of the copy. The information in Legend box says they were made by Department of Civil Aviation, which was renamed 40+ years ago. No luck with Google.
Thanks&Cheers

The stuff you will do here is way harder then the exam. I studied extensively due to the fear mungering I encountered and I was astonished by the test and how easy (maybe not the correct term) it seemed to be? My advice is to put some effort into knowing your stuff, put more effort into knowing where to find stuff (aip, vfrg etc etc) and don't carry any nerves into the exam, don't rush, it's no different to what you do at home with a bit of music in the background and a coffee in your hand. I really enjoyed it.

John, you really know some good stuff! I'm going straight onto my cpl stuff now and I'll be sure to seek you out when I come up short with errors like this! Thanks again for your time

[color=blue][i][b]I sat the exam this morning, 56 out of 56![/b][/i][/color]

Well done, indeed, Meade

[color=blue][i][b]I am trying to find a copy of TOW / Landing charts for the Cessna 172N[/b][/i][/color]

Stjepan, when you next get the chance and you are at the airport, have a look in the aircraft. The aircraft [b]should[/b] have a copy of the present approved POH which includes the AFM.

The copy in the aircraft probably will be the same as (or similar to) the POH found at https://takewingaviation.com/wp-content/uploads/2017/02/N739EF_172N_POH.pdf.

If you go to Section 5 you will find the current approved takeoff and landing information. If you don't find the charts, ask your instructors where they are - they are required to be carried in the aircraft as part of the POH. I would be surprised if the POH in the aircraft has anything other than the original Cessna data. (Caveat - there is a provision in the Regs for an aircraft not to carry the POH/AFM but this provision would not normally apply to the likes of a Cessna single).

Also, check what the POH has for the loading data (Section 6). There should be a page indentified, probably, as a "Load Data Sheet" and this has to have been approved by a Weight Control Officer holding a Weight Control Authority issued by CASA. A typical example can be found at http://www.redcliffeaeroclub.com.au/files/aircraft/PN68_WB.pdf, albeit for a different make of aircraft. The load data sheet will provide the starting weight and CG data for calculations and will either just refer you to the POH Section 6 loading system or direct to some other loading system (for example, the LDS cited directs the use of Jim Liddle's trimsheet loading system).

Note that if the LDS does direct you to another system, the Regs require that you use that other system in operations. Trap for young players which can provide for some discussion at CASA ramp checks if the CASA folk spot the discrepancy.

As a sideline note, you will observe that Jim's trimsheet uses a non-standard (ie non-OEM) datum so, unless you know what you are doing, you need to be very careful that you use the entry data cited in the LDS. A very common trap/error (especially with such trimsheets that use a datum which can provide entry data able to be confused with OEM datum data) is that use of the OEM datum based data will not be compatible with the trimsheet and will provide incorrect answers which look OK. If you are interested in reading up a bit on loading systems, you might check the thread at https://www.bobtait.com.au/forum/rpl-ppl/5236-aircraft-trim-sheet-loading?limitstart=0

[color=blue][i][b]The information in Legend box says they were made by Department of Civil Aviation, which was renamed 40+ years ago[/b][/i][/color]

Yes, indeed, DCA went through quite a few name changes before finally morphing into CASA.

I am presuming that you have copies of the old P-charts (similar to what Bob refers to as "Cessna" charts for convenience) which featured in the old DCA style Civil Mk1 and Mk2 flight manuals. Unfortuately, when the old flight manuals were thrown out (post Yates Report), those old charts ceased to be valid as such (although they are still useful so I would keep the copies in your bottom drawer someplace).

Do let me know how you go with locating the POH for the aircraft.
[color=blue][i][b]
I'm going straight onto my cpl stuff now[/b][/i][/color]

Only too happy to lend a hand. You will find Bob's books useful for your studies.