OK, this took 25 minutes (perp notes and calculations) while having breakky and a phone call interruption.
My point here is, and I am formally addressing this with ATSB is that with a little specialist knowledge these things can be given a much higher quality safety message. The current report is a lowly level 5, so it does not get any serious analysis and its nothing more than a rporting of information sent in.
My thought is that is a waste of time unless the report spells out the flaws or the reasons in what led to the accident so others can learn from it.
The ATSB is under financial pressure to reduce expenses, and they do not have any piston specialists anyway, so a priority is applied, and these reports get done as simple as they are. My frustration is it would not be hard to gain some knowledge in house or at least seek out where that specialist help is externally.
So lets begin with my back of beer coaster study (no beer was consumed with my muesli )
Departure was from Lilydale at 2.20pm and the exhaustion occured at 7pm abeam Cunnamulla some 580 miles north. The average speed was around 124 knots, and safe to assume a bit of tail wind was enjoyed.
Using fuel flows as a prudent well educated pilot would I believe the following would be a fair assessment. Take off flow Approx 59LPH and using a target EGT leaning in the climb a final flow rate would be around 40LPH. If left alone the volumetric flow rate change during the climb would have the FCU delivering maybe 10% more as the DA increased, so the effect of not leaning very well in the climb Vs doing it well is only going to be a few litres. Note this is for a Lycoming and a TCM is different.
With a climb of around 90 knots TAS average and say 20 minutes approximately this would yield a climb stage of 30 miles and 17 litres. Again subtle changes would have little affect. This means 550 to run from TOC to abeam CMU.
Guesstimate of TAS at the claimed 65% power and with know spats, based on POH performance data would yield about 115 plus or minus for spats etc. or lets say 110. Not that it matters much as GS is the critical key here, which was in the early 120's.
Using a best range fuel flow for the selected power/speed required, the engine would be set to 10dF LOP and burning 26-26.5 LPH. This is pretty much what the pilot claims he was told when he rented it. I believe the value to be correct advice, provided you knew how to operate the engine.
The range then would be calculated roughly as 30 miles for climb and a further 6.33 hours at 124kts GS as 790NM. YBCV is 678NM so this was achievable with a bit over over 55 min. reserve. But it had to be done right.
However, 65% power with Poor mixture control could be anything at that height ranging from say 33LPH at 75dF ROP to around 45LPH. I do not have the actual data but I do not think you can get any more than that into the engine at that height.
Based on 45LPH the range would be down to 480 miles or even at 33LPH around 660 miles. The pilot managed a distance of 580 miles so less the climb, that was 550 miles of cruise in 4.34 hrs (4.67-0.33 hrs), for an average of 38.7LPH.
The pilot seemed to be a Jabiru flyer so perhaps not much mixture knob experience and that would explain a lot when he claimed he leaned it, but who knows how much. And with so many pilots afraid of the red knob I can believe it. Heck I think back to when I was learning to fly.....nothing of value in the red knob education at all.
So it is all very believable how he got to where he was, and without an accurate fuel flow gauge or a very good margin for error, this was a bad decision passing Bourke.
Important to note that no pilot can trust the POH of any aircraft manufacturer when it comes to engine matters. Seriously they can't be trusted. So many are found to be either contradictory from one page to another or completely wrong. There is nothing to argue here, this is fact. The problem is which ones can you trust? And which parts can you trust, and the only safe assumption is trust none. They may well be accurate for take off charts and other procedures, and I am not in a position to critique them there, but in engine performance related sections you are foolish to believe everything you read. The secret here is to know how to critically appraise them. About 1-2% of pilots are. That leaves 98%, and very few instructors if any are in the 1-2%.
Case in pont in the Piper Warrior POH there are graphs that show performance for 55/65/75% Best Power Mixture, and for this example lets say the 75%
power as shown in the example. There are 75% best power and 75% Best Economy with two different TAS (122 & 118).......WTF?? 75% of 160HP is 120HP and iff you apply 120HP to that plane with the same prop, you get XXX.X knots TAS. How is it possible to get two different numbers? Simple answer it is not.
What is more they supply two different fuel flows to achieve each of these power settings, and that is fine but if you take the 65% power setting the Best Power which one can only assume means around 75dF ROP is 8.8GPH or 33.3LPH. They also show a 65% power Best Economy flow of 7.5GPH or 28.4LPH. Well the best BSFC for the engine will be slightly LOP, and at these powers around 10-20dF LOP which typically on the O-320 is found at 6.98 GPH or 26.4LPH.
Is it any wonder pilots have no idea? Given all the expertise has long gone from most organisations and it is all turbine/jet focussed is it any wonder ATSB are no better when it comes to good reports.
Last of all, and this pilot did not have the luxury of time to do this, but how often is the usable quantity IN FLIGHT tested? How do you know that the supposed 185 litres claimed to be usable is actually usable. The POH suggests 181-182 litres, but even then how can you trust this. The only way to know is at least once a year just prior to its annual is run a tank dry and refill. Best not to do both during the same flight if you only have two .
None of this is taught for PPL or CPL at any school I am aware of and it is certainly not in any texts.
The reason we do not have more of these problems is possibly through good luck than good training.
The Safety messages that should come out of the ATSB report are;
1. The importance of having accurately and regularly proven usable in flight fuel checks.
2. Having a decent engine monitor fitted and fuel flow with totalisation.
3. Pilots educated in proper engine management techniques and to be able to critically think when reading a POH. Having the understanding of engine fuel requirements and what the real leaning techniques are and how they should be applied.
Happy to take questions. Disclaimer: The above calculations are based on a very quick study over brekky and using my iphone calculator. I have not allowed for known weather, descent and any other small impact factors as they probably have no significant effect on the outcome. I could have made mistakes too as I have not double checked anything.
I'll continue the appreciation trend. I never really have much to weigh in on these discussions but I read everything you post very carefully and enjoy taking on the knowledge. Thanks Jaba, keep it up.