Crash Landing in Cunnamulla - two hurt.

[Creampuff]

And how do you know your engine is delivering "65% power"?

[ForkTailedDrKiller]

Jaba, I think you are over-complicating this!

Lilydale to Charleville (680 nm) NVFR non-stop in a Warrior was never safely do-able for the average Joe Blow pilot in an aeroplane he was not familiar with, and even then its marginal IMO.

I would consider it marginal for me in the Bo until I was able to compare time-to-run on the GPS with endurance on the Shadin digital fuel flow as I approached Bourke.

What are the three most significant advances in GA aeroplanes in the 40+ yrs I have been flying? 1) GPS, 2) digital fuel flow, 3) all cylinder engine monitors!

Any leg over 640 nm has me thinking carefully about my options.

688 nm (Tennant Ck - Broome) is the longest non-stop leg I have flown in the Bo.

Dr

[ForkTailedDrKiller]

And how do you know your engine is delivering "65% power"?

Cause TCM say their IO520BA engine running ROP at 2400 rpm and 21" MP = 64.5% power!

So I rounded it up to 65%!

Dr

[Brian Abraham]

Crunched the numbers from the flight manual for a 207 to fly a 500 mile segment, no wind.

Power %xxTASxxxGPHxxxTimexxxxFuel Required
xxxx75xxxx139xxx15.6xxxx3.6xxxxxxx56.12
xxxx69xxxx135xxx14.5xxxx3.7xxxxxxx53.7
xxxx61xxxx128xxx12.9xxxx3.91xxxxxx50.39
xxxx50xxxx115xxx10.7xxxx4.35xxxxxx46.52
xxxx43xxxx106xxxx9.5xxxx4.72xxxxxx44.81

25% more at 75% than 43%.

flying my aircraft between forest and ceduna at 120knots in still air then back the other way at 65 to 70 knots as safety for a warbird cub saw exactly the same fuel burn

Does not compute, and is against all the physics of aviation.

gods there is some dribble that passes for expertise these days

I'm afraid that you've contributed your share on this thread. But then we all have from time to time.

[Jabawocky]

Lilydale to Charleville (680 nm) NVFR non-stop in a Warrior was never safely do-able for the average Joe Blow pilot in an aeroplane he was not familiar with, and even then its marginal IMO.

Yep...and I agree. But theoretically you or I could do it with the right tools. He had none of them.

[ForkTailedDrKiller]

Second longest leg I have flown in the Bo is Ayres Rock to Lenora (660 nm) - I am sure you remember that one Jaba!

Would have been a bit of a worry without the GPS and the Shadin - especially as I seem to recall we were down to 110 kts GS (ie 50 kt headwind) at one stage.

Dr

PS: The PA28-161 manual that I have says, "Fuel consumption for flight planning purposes:- 31.5 L per hour".

[djpil]

Quote:
flying my aircraft between forest and ceduna at 120knots in still air then back the other way at 65 to 70 knots as safety for a warbird cub saw exactly the same fuel burn
Does not compute, and is against all the physics of aviation.

Fuel burn in my Pitts, over the same distance, at 65 kts is the same as at 115 kts (per my cruise performance charts only, I haven't done it to verify it) but seems like basic aircraft physics to me.

Lean for best economy/best power - per Lycoming Operator's Manual, pretty standard stuff taught in theory class as I recall.

Lycoming defines the term best economy, it is not up to Piper to state something different as the engine has a Type Certificate itself.

I have often wondered about the HP figures in that Warrior POH associated with % powers for best economy vs best power but it doesn't really matter.

[VH-XXX]

When I fly the Cirrus it actually tells me on the Avidyne how many percent power I am developing. Very handy for answering pprune questions.

From memory, 68% was the max it was capable of at 9,500ft but it's been a while since I've been that high, don't want nose bleeds (non turbo of course).

[Jabawocky]

djpil,

lets look at this;

Lean for best economy/best power - per Lycoming Operator's Manual, pretty standard stuff taught in theory class as I recall.

Most likely taught wrong...almost guaranteed Not your fault, you were not to know.

Lycoming defines the term best economy,No they do not it is not up to Piper to state something different as the engine has a Type Certificate itself.And you trust that??? Ohhhh Nooooo

Lycoming defines the term best economy, it is not up to Piper to state something different as the engine has a Type Certificate itself.

Trust me.......Do not trust this stuff, on any day I can demonstrate the errors, and you can too if you actually realise what they are. Data has no opinion. It is what it is.

[Brian Abraham]

djpil, I must confess to casting some burley upon the waters with my "Does not compute, and is against all the physics of aviation" in an endeavour to draw D8 out. The following diagram shows that you can have two speeds that provide the same specific range. Max range speed is too slow for the average aviator, and if I recall is about 90 knots for a Bonanza class aircraft. I don't recall ever seeing a GA manual which provided max range or max endurance details. They do provide range and endurance tables, but not what to aim for to extract the maximum.



W8's

if you move a mass from point A to point B in a straight line in still air and you repeat the exercise at different speeds, you will use the same fuel in each case.

is only true if you apply the caveat in a very specific manner as per the diagram. Which he has not done, his statement is an all encompassing one, that the total fuel burn will always be the same over a given distance irrespective of power setting.

[peterc005]

The Lycoming engineers know what they are doing and I don't think it is prudent to recommend anything that is inconsistent with the POH.

[gerry111]

With the greatest of respect, peterc005.. I'd suggest that that you keep an open mind to some of the information available on this thread.

[djpil]

I did not say Lycoming was right or wrong, simply that they defined a term which an airframe manufacturer uses. Stuff in Piper's AFM is consistent with what will be achieved (give or take the usual caveats on stuff in good condition etc) doing what is stated in the books.
Stuff taught wrong? Again, I make no comment on what is right or wrong, just what is consistent with the books.

Finally, experience has taught me never to trust people who say "trust me".

Incidentally, I have seen good aircraft performance data with incompetent analysis leading to rubbish information - not saying that applies to anything in this thread.

Brian, I certainly agree wrt your view on W8's statement that you quoted. Never seen a GA manual with max range and endurance information? - I've done some and I've seen others. Of course, some with appropriate gear would lean some more and do better. Doesn't invalidate the info in the manuals that I have.

[LeadSled]

Local rumour tells me he even booked his own wife for driving without a seat belt.

Anybody who lived around Gunnedah years ago will remember a particular member of the NSW Constabulary known as "crazyhorse".

Tootle pip!!

[43Inches]

Stuff in Piper's AFM is consistent with what will be achieved (give or take the usual caveats on stuff in good condition etc) doing what is stated in the books.

Straight from Pipers PA28-161 POH figure 5-25 Best Power Mixture Range;

Still Air Range 65% at 8500ft 590nm without reserves. If you factor in lack of fairings offset by 10kts tailwind, ie drop 7% for fairings then add 7% back due winds the figure remains about 590nm.

So the book says he will run out of fuel using 65% "best power" leaning at around 590nm, how far is it from Lilydale to Cunnamulla?

Forgot to reply to this earlier as well;

we flew at 2500rpm leaned to peak rpm then tweaked back rich a turn or two.

Best power is achieved when you achieve best power, ie, when the rpm peaks, you are confusing using an EGT to lean with rpm technique. To lean best power fuel flow you need to lean to best rpm, the procedure is to set the rpm slightly below desired and lean until rpm peaks, you now have best power mixture. Moving the mixture forward of this position you might as well open a fuel drain tap as well and fly along. The only point to be cautious about is not to lean aggressively above 75% power.

[Jabawocky]

43"

So the book says he will run out of fuel using 65% "best power" leaning at around 590nm, how far is it from Lilydale to Cunnamulla?

Yeah, about says it all, however had he used the red knob as per the best power fuel flow, or 75dF ROP he would have travelled a lot further due to the tail winds. His burn would have been about 33LPH not the 39LPH he seemed to have used (by my calculations). So running much richer than he should have and blissfully unaware.

peterc
I should know better than take your bait, but I will try to respond to this as best I can.

The Lycoming engineers know what they are doing and I don't think it is prudent to recommend anything that is inconsistent with the POH.

Lycoming engineers know what they are doing? Yeah the few they have might. But they do not write the stuff you read. And that is where the problems arise.

Inconsistent with the POH? You are kidding me, the POH's are often inconsistent with the POH.....one page from the next! So what do you do now? What do you do when they are inconsistent with the laws of physics? Maybe in your world you can alter the laws of physics but the rest of us can't, except F22 pilots, I think they can.

Also remember POH's give some data points, usually the extremes of the envelope and you are free to operate anywhere in there, this includes matters not relating to engines too.


Lastly;
It seems this thread has done more for safety than the report did. Thats a plus

[ForkTailedDrKiller]

So the book says he will run out of fuel using 65% "best power" leaning at around 590nm, how far is it from Lilydale to Cunnamulla?

I make it 585 nm!

I wonder what the fuel guages were showing as he flew past Cunnamulla headed for Charleville?

Dr

[Creampuff]

All this discussion about percentage power cracks me up.

I have no idea what percentage power my engine is producing from time to time, and I don’t care because it wouldn’t make any difference to my flight planning or aircraft/engine management.

All powered aircraft have some kind of fan, somewhere, that produces thrust. It can produce as much thrust as it can produce. The pilot can generally manipulate controls to get the fan to produce as much thrust as it can produce, or less.

I can tell whether the fan on my aircraft is producing the thrust I need, without having a clue what ‘percentage power’ the engine is producing. I can tell that by how fast the aircraft is accelerating down the runway, how fast the aircraft is climbing, and how fast the aircraft is cruising. If I need the aircraft to do something specific, like go a very long way without running out of fuel, I make the fan produce whatever thrust is necessary to produce an IAS that corresponds with the minimum drag speed. I can also make sure the engine is producing that thrust as efficiently as it can, by choice of RPM and mixture settings. If I am in more of a hurry, I will make the fan produce more thrust so that the aircraft goes faster. I will make sure the engine does that at EGT settings that keep the engine and my pocket happy, and a fuel flow that will result in enough reserve at ETA.

Percentage power is just number estimated from a bunch of other numbers. I already know all the other numbers.

I realise the APS amigos (…blessed be the amigos…) use %power as a means to describe the fuzzy boundaries of the ‘red box’ or ‘red fin’ (depending on the axes of the charts). But it’s just as easy to remember some rough altitude and EGT delta figures. In the climb I just remember one number: target EGT on my hottest cylinder.

And by the way, I don’t want the engine to produce as much power as it can possibly produce (would that be 100%?), during the climb…

Quick quiz:

1. Cruising along fat, dumb and happy and the CHT alarm goes off because #5 CHT has reached 200c and is continuing to rise very quickly. What do you do? Would your answer be different if the % power gizmo says the engine is producing 61.87% power? If yes, what would you do instead?

2. Balls to the wall, sea level on an ISA day, and the aircraft trundles along the runway at 40 knots and doesn’t get any faster. What do you do? Would your answer be different if the %power gizmo says the engine is producing 100% power? If yes, what would you do instead?

3. What’s the point of ‘best glide speed’ and how is it determined?

[43Inches]

I agree that a good pilot can get a lot more out of their aircraft if they understands it, including airspeed being the most critical side of performance.

The main issue is that 90% of GA pilots out there just want the thing to get from A to B and not think too hard about it.

If you apply the book figures and techniques for this aircraft, the PA28-161 it will do roughly what it says, enough for you to get from A to B in one piece.

If the pilot had consulted the range charts he would see that a fuel stop was necessary at Bourke. If he had used the Piper recommended fuel burns for his flight log and used the correct leaning technique he would not have ended up where he did. He may have used this information to tell him the fuel gauges don't seem right I'll stick to the original plan and land at Bourke.

Instead it sounds like he relied on information provided from an operator that included fuel flows that are not related to his intended usage (both long range cruising and leaning technique).

If the manufacturer says that an aircraft can only do this, and you find its doing something magically way better, you best ask why that is (it may be true but mostly unlikely). There are many aircraft wrecks from high capacity jets to light trainers that could have been avoided if they understood what the aircraft is capable of. The jets that deep stalled due to blocked pitot tubes comes to mind as a basic example, pilots recorded on CVRs claiming how well their 727 was climbing at 420kts at 8000fpm etc...

The manufacturers book is a fine starting place to understand what it is capable of. After that you can tweak your speeds, leaning, climb and descent profile to beat the book figures with proper knowledge, and testing. For instance if I was told a PA28 would only burn 25lph, I would ask how they achieved this and still land in Bourke and fill it up and test how much it actually burnt.

[Trent 972]

A lot of this recent discussion seems to be based on/taken from the writings of J. Deakin's 'Pelican Perch' articles, and a good discussion it is, but for those not too familiar with those articles, consider this quote from Pelican Perch #64, before you discount the POH numbers.

Oh, you don't have an engine monitor? Sorry pal, I can't help you; you're on your own. I'm really hard-line on engine monitors; I think it's stupid to operate one of these big, expensive, life-supporting engines without one

.

AND
Creampuff,

If I need the aircraft to do something specific, like go a very long way without running out of fuel, I make the fan produce whatever thrust is necessary to produce an IAS that corresponds with the minimum drag speed.

Does that include 'if there is a significant headwind component', or should you just stick to the Law and leave flight training alone?