This thread has ended up on one of my favourite subjects - flight manuals. Last August I put the following to CASA:
The issue is that the Australian P-chart gives significantly shorter distances than the Bellanca Pilot's Operating Manual for the same set of conditions. To do the comparison required consideration of the differences between the two sets of data:
- operation from a sealed surface vs short, dry grass for the Australian P-chart;
- acceleration to the higher take-off safety speed required by the Australian P-chart;
- lower climb gradient of the Australian P-chart resulting from climb at airspeed higher than speed for best angle of climb.
The discrepancy is not covered by the 1.15 factor on the Australian P-chart and is significantly greater than the margin offered by this extra 15% of distance.
If the Bellanca POM provides unfactored, reasonably accurate data then the Australian P-chart, even with that 1.15 factor, represents unsafe data. At I.S.A., S.L. with take-off distance available as per the Australian P-chart, the manufacturer's data indicates that the aircraft will hit the "15.2m high screen" at about 3 m below the top. The reason an accident has not occurred may be that no pilot has attempted a take-off in such limiting conditions. It may never happen but ....
Just recently CASA responded with
The AFM consistent with the airplane and any manufacturer's data should be used. There is a proviso as discussed. If one had perf data more conservative than the manufacturers then it would be possible to use that. At all times the AFM must reflect the aircraft configuration i.e Manufacturers AFM + FMS for changes.
It was disappointing that there was no interest in resolving the technical query and no interest in advising other Decathlon operators of the issue. The clear message I got was that CASA will not stand behind those P Charts - they are now obsolete. I'm not happy that I'm taking sole responsibility for providing adequate perfomance data to pilots. Firstly, I'm not going to let pilots fly per the POM with an approach speed only 13% above stall. I'm not going to let them fly into strips as short as that given by the old P Charts. I wonder why the P Chart has a 10% higher take-off safety speed than the manufacturer's data, which is 1.2 times stall speed.
The good news for other aircraft types is that the P Charts are generally more conservative and more appropriate but it is the operator's decision and the operator takes responsibility for it.
Referring to an earlier post here - I have seen examples of the P Charts being inserted
into AFM's, reportedly per CASA advice.
The W&B aspects of the new AFM's often do not hang together too well as another noted previously. There is a regulation somewhere to the effect that we must follow the procedures in the AFM. i.e. the old loading system from the superseded Australian manual must not be used. The actual empty weight is required of course, then we must use the loading system from the "new" official AFM which generally means converting to lbs and ins.
So, having got my "new" AFM I'm still trying to sort out all the information and this is probably the most simple airplane in the country. The next thing I've just noticed is that an Australian AD was issued back in 1973 which conflicts with information in the new AFM. Please be patient with me, I'll research it a bit more and suggest an appropriate course of action.