- A good introduction to this may be found at:
Back when CASA changed the rules (see my page on the Great Flight Manual Debacle) we had their “P” Charts which were very good and consistent with what pilots were taught in their theory classes. However, problems can arise with deficiencies in document control and attention to detail. When the rules were changed, CASA stated that we could continue to use these “P” Charts however they had withdrawn approval so the Operator/Owner had to take responsibility. If I am going to take responsibility then I want to know more about the source of the charts. CASA declined to give me a copy of the test report and I had some problems as you can see from the document below.
Look at the manufacturer’s data for the Standard Decathlon. Takeoff distances are for the 56″ pitch propeller but my Decathlon had a 60″ pitch propeller, as do others. That would have a significantly longer takeoff distance but there is nil information on the effect of that!
Now look at CASA’s “P” Chart. It simply says it is for 8KCAB. What propeller did the test have aircraft have? Fixed pitch or constant-speed? If fixed pitch, was it 60″? Who knows? The 180 hp variant with a C/S prop came after this.
It is interesting to see how those “P” Charts were produced. We would just do 3 takeoff and landings at a place like Bacchus Marsh airfield. Consider landings. Someone would take a series of photographs from which the distance from 50 ft above the ground to touchdown would be determined. Someone would watch and stand abeam the touchdown point. Another person would be at the point where the aircraft stopped. A distance measuring wheel would give the ground roll. Similar technique for the takeoff distances. Average of the three data points.
The analysis was pretty much per the UK CAA’s Safety Sense Leaflet 07 Aeroplane Performance at https://publicapps.caa.co.uk/modalapplication.aspx?appid=11&mode=detail&id=1913 He uses the Cessna 172 as an example here. I tried it for the Standard Decathlon and it worked out quite well.
Simple software expanded the one average data point into the comprehensive “P” Chart! Press PRINT.
Pilots in the UK do it per the CAA’s CAP 698 Aeroplane Performance Manual at https://publicapps.caa.co.uk/docs/33/CAP698.pdf
There is some more detail in my book “Aerobatics Down Under” – the Kindle version is only US$3 or about A$4 at https://www.amazon.com.au/dp/B07PXY467M
We’re going to get more serious about performance so get up to speed with some homework first. Start with this introduction to The Bootstrap Approach to Aircraft Performance by John Lowry.