Crash Landing in Cunnamulla - two hurt.
From the performance tables I managed to dig up online 65% best power cruise, fuel consumption is 8.8 US GPH or about 33 l/hr and TAS at 9000 PAlt varies from 110 to 113 KTAS depending on model.
So help me out here.
I've decided I want to cruise at "65% power". Is that a "best power" setting or a "best economy" setting?
How do I set "best power" and what percentages of power can I get there?
How do I set "best economy" and what percentages of power can I get there?
I've decided I want to cruise at "65% power". Is that a "best power" setting or a "best economy" setting?
How do I set "best power" and what percentages of power can I get there?
How do I set "best economy" and what percentages of power can I get there?
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Leafie, Mate I had hoped not to have the smarty posts on this, 
but I guess I am guilty of that too so, touché! I deliberatley wanted folk to think about it, and maybe not so much you but all the lurkers and noobe's out there that could learn from this.
Creamie is on the trail and I feel is holding back, or just lazy.
I was up at 3am, been to Canberra and back and just got home.....so will try to do this justice in the morning some time so that a sensible discussion can be had so we can all learn something. Because from the ATSB report we are learning nothing, well apart from a bunch of things that we should not be learning.
but I guess I am guilty of that too so, touché! I deliberatley wanted folk to think about it, and maybe not so much you but all the lurkers and noobe's out there that could learn from this.Creamie is on the trail and I feel is holding back, or just lazy.
I was up at 3am, been to Canberra and back and just got home.....so will try to do this justice in the morning some time so that a sensible discussion can be had so we can all learn something. Because from the ATSB report we are learning nothing, well apart from a bunch of things that we should not be learning.
Considering these sums;
Aircraft ran out of fuel at 1900, departed at 1420, that's 4 hours 40 minutes flight time.
4.7 hrs burn at 36lph = 170ltrs
Add 5-10lt for additional climb fuel, 5lt for taxi and you have exceeded your 180ltrs available.
180 litres is the maximum usable fuel, 190 litres is the total including unusable fuel.
The aircraft ran out of fuel almost exactly at the point it should having followed the recommended (Piper POH) procedure for leaning for 65%-75% "best power".
If the operator had another way of leaning the aircraft to achieve 25-27lph or even 30lph, was the individual involved advised of this method. These are basically the cruise flows for 55% and 65% "best economy" setting, and I have rarely seen pilots that know how to do this properly.
Was the 30lph figure derived from airswitch, tacho or block time. Using block times for trainers results in very low actual fuel burn on short flights due to .3 spent taxiing around at very low fuel flow.
We never divulged the actual burn rates for our fleet as they were used for financial reasons, not flying maximum range in one day. The averages again depended greatly on what type of flying the aircraft had done. Students were given a conservative block rate at 36lph at 65%, basic leaning technique applied as per the piper manual. This figure being the POH 65% rate (for "best power" with a small margin), this also fitted in conservatively with actual records of usage. Further they should understand that higher power settings will result in more fuel burn, sounds simple.
In any case the report as stated previously does not reference to how the aircraft was leaned (or supposed to be leaned to achieve company stated burn). There is no mention of what instrumentation was available. There was no test done or results of such test published of the aircraft fuel gauges. The only fuel log appears to reflect just writing what was on the indicator.
Aircraft ran out of fuel at 1900, departed at 1420, that's 4 hours 40 minutes flight time.
4.7 hrs burn at 36lph = 170ltrs
Add 5-10lt for additional climb fuel, 5lt for taxi and you have exceeded your 180ltrs available.
180 litres is the maximum usable fuel, 190 litres is the total including unusable fuel.
The aircraft ran out of fuel almost exactly at the point it should having followed the recommended (Piper POH) procedure for leaning for 65%-75% "best power".
If the operator had another way of leaning the aircraft to achieve 25-27lph or even 30lph, was the individual involved advised of this method. These are basically the cruise flows for 55% and 65% "best economy" setting, and I have rarely seen pilots that know how to do this properly.
Was the 30lph figure derived from airswitch, tacho or block time. Using block times for trainers results in very low actual fuel burn on short flights due to .3 spent taxiing around at very low fuel flow.
We never divulged the actual burn rates for our fleet as they were used for financial reasons, not flying maximum range in one day. The averages again depended greatly on what type of flying the aircraft had done. Students were given a conservative block rate at 36lph at 65%, basic leaning technique applied as per the piper manual. This figure being the POH 65% rate (for "best power" with a small margin), this also fitted in conservatively with actual records of usage. Further they should understand that higher power settings will result in more fuel burn, sounds simple.
In any case the report as stated previously does not reference to how the aircraft was leaned (or supposed to be leaned to achieve company stated burn). There is no mention of what instrumentation was available. There was no test done or results of such test published of the aircraft fuel gauges. The only fuel log appears to reflect just writing what was on the indicator.
Last edited by 43Inches; 25th Mar 2014 at 22:40.
Awwww, OK Jabba
From the inestimable John Deakin (here: Pelican's Perch #65<br>Where Should I Run My Engine?<br>(Part 3 -- Cruise) - AVweb Features Article)
[Bolding added]
From the inestimable John Deakin (here: Pelican's Perch #65<br>Where Should I Run My Engine?<br>(Part 3 -- Cruise) - AVweb Features Article)
The first consideration for cruise has nothing to do with engine management at all, but "airplane management." Specifically, the speed you use to get the job done. This is, by far, the most dominant effect for range and efficiency. Everything else pales by comparison.
So many pilots always seem to use 65% or 75% power, because that may be the only power setting shown in the POH, or because "everyone uses 65%." Some actually believe that since the factory only shows certain power settings, those are the only "approved" settings! …
…
Some say, "Just set 23 inches and 2300, and forget the mixture."
Sorry if I offend, but that's unspeakable, a complete cop-out, and a lousy way to operate these engines.
"When all the fools in town are on your side, that's majority enough." – Anon
Folks, there's NO reason (except laziness) to fix on just one power setting, and no reason at all to even think in terms of "percent of power." Especially that 65%, that was a CRUTCH, invented by marketing departments and magazines, who wanted a common number for easy airplane comparison. It can be handy to use percentage as a reference tool when talking about engine management, as we do here.
…
Truly, your first job is to determine what your mission calls for. Most of the time, I just want to get there as fast as I can (oh, for a BD-10), regardless of using a few extra gallons of fuel. That's easy, I just set the most power I can get without hurting or overheating the engine, and go. I call this "Go Fast Mode." …
…
For extreme long-range work, it becomes necessary for me to slow WAY down, with about 120 knots being the MAXIMUM indicated at gross weights, and perhaps as low as 105 knots when very light [in my Bonanza].
So many pilots always seem to use 65% or 75% power, because that may be the only power setting shown in the POH, or because "everyone uses 65%." Some actually believe that since the factory only shows certain power settings, those are the only "approved" settings! …
…
Some say, "Just set 23 inches and 2300, and forget the mixture."
Sorry if I offend, but that's unspeakable, a complete cop-out, and a lousy way to operate these engines.
"When all the fools in town are on your side, that's majority enough." – Anon
Folks, there's NO reason (except laziness) to fix on just one power setting, and no reason at all to even think in terms of "percent of power." Especially that 65%, that was a CRUTCH, invented by marketing departments and magazines, who wanted a common number for easy airplane comparison. It can be handy to use percentage as a reference tool when talking about engine management, as we do here.
…
Truly, your first job is to determine what your mission calls for. Most of the time, I just want to get there as fast as I can (oh, for a BD-10), regardless of using a few extra gallons of fuel. That's easy, I just set the most power I can get without hurting or overheating the engine, and go. I call this "Go Fast Mode." …
…
For extreme long-range work, it becomes necessary for me to slow WAY down, with about 120 knots being the MAXIMUM indicated at gross weights, and perhaps as low as 105 knots when very light [in my Bonanza].
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I think that this is all bollocks.
I did a 100km round trip to the airfield last night to sit in the piper warrior I did my cross country navs in.
we flew at 2500rpm leaned to peak rpm then tweaked back rich a turn or two.
straight forward physics says that this rpm for endurance is nonsense.
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.
the only difference is that you burn the fuel at different rates.
if you set out to fly somewhere with insufficient fuel; changing your rpm settings will get you the same result just at a different time.
all sensible flying is done at best cruise speed which is usually the 2500rpm speed. the only time you need to be concerned to achieve the slowest fuel burn rate is when your destination airfield is socked in by some weather moving through and you need to loiter in the air to wait for clear landing conditions.
gods there is some dribble that passes for expertise these days. anyone would think you all worked for CASA.
I did a 100km round trip to the airfield last night to sit in the piper warrior I did my cross country navs in.
we flew at 2500rpm leaned to peak rpm then tweaked back rich a turn or two.
straight forward physics says that this rpm for endurance is nonsense.
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.
the only difference is that you burn the fuel at different rates.
if you set out to fly somewhere with insufficient fuel; changing your rpm settings will get you the same result just at a different time.
all sensible flying is done at best cruise speed which is usually the 2500rpm speed. the only time you need to be concerned to achieve the slowest fuel burn rate is when your destination airfield is socked in by some weather moving through and you need to loiter in the air to wait for clear landing conditions.
gods there is some dribble that passes for expertise these days. anyone would think you all worked for CASA.
I don't think the pilot involved was flying for maximum range in this instance. His original plan was to refuel at Bourke and then continue. When approaching Bourke the use of fuel gauges and an obviously wrong concept of the fuel flow and fuel remaining led him to the decision to continue.
2500rpm will work for best range at 12000ft, if you lean it by opening the throttle wide allow the engine to go past 2500rpm then lean the mixture back to 2500rpm. If you do that you may just make it to 700nm in still air (including descent into where ever you end up). I'm not going to get into where the egt lies relative to peak on this one, and don't forget to take off 7% if your wheel fairings are off for maintenance.
we flew at 2500rpm leaned to peak rpm then tweaked back rich a turn or two.
straight forward physics says that this rpm for endurance is nonsense.
straight forward physics says that this rpm for endurance is nonsense.
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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.
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W8
You are correct in some ways, as far as energy content required however, using ROP powers and pick any number but in this case 65% power you can have a fuel flow of anywhere from around 30LPH to maybe 45LPH just by pushing the mixture knob all the way in.
You are still making the same HP (within a few fractions of a HP albeit slightly less) and wasting a lot of fuel. In other words the BSFC is going up rapidly for no extra torque produced.
The next issue is to go faster you need more and more power, as Brian has just posted.
I have to say this, some of the posts so far have been of very high quality for pprune standards indeed.
Chocky from to 43" and well Creamie....he gets one but I expect him to be on the ball.
I did some notes while I had my muesli this morning, just need a few minutes to turn it into a post. Stand by.
You are correct in some ways, as far as energy content required however, using ROP powers and pick any number but in this case 65% power you can have a fuel flow of anywhere from around 30LPH to maybe 45LPH just by pushing the mixture knob all the way in.
You are still making the same HP (within a few fractions of a HP albeit slightly less) and wasting a lot of fuel. In other words the BSFC is going up rapidly for no extra torque produced.
The next issue is to go faster you need more and more power, as Brian has just posted.
I have to say this, some of the posts so far have been of very high quality for pprune standards indeed.
Chocky from to 43" and well Creamie....he gets one but I expect him to be on the ball.
I did some notes while I had my muesli this morning, just need a few minutes to turn it into a post. Stand by.
[I]f 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.
You need to go back to Basic Aeronautical Knowledge and revise the concepts of maximum range (distance travelled) and maximum endurance (time aloft).
If you want to ‘go far’ without running out of fuel, you have to fly the aircraft in the most aerodynamically efficient condition. That’s about minimising drag, which is (to the extent the pilot is in control of the variables) primarily about controlling airspeed.
Glider pilots are keenly aware of the concepts and the differences. (Why do you learn the glide speed for engine failures?)
Take two aircraft – let’s call them Warriors – and put the same fuel and other loads on board. They take off at the same time, at the same weight, and climb to the same altitude and head to the same destination 500nms away. One is cruising at the highest speed it can achieve, the other is cruising at the speed that minimises drag. Both have leaned the EGT to the same delta from peak.
The ‘fast’ aircraft will run out of fuel before the destination. The other aircraft will make it safely.
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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.
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.
Jaba: 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.
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who the hell ever flies at 65% power on a cross country?
2500 rpm, leaned and know the fuel flow.
back in the old days
it wasn't that hard and no one ran out of fuel.
what is the limit of usable fuel??? who gives a fcuk. ever heard of 45 minutes reserve???
if the last two litres of usable fuel in the tank worry you then sonny jim you are incompetent. you are worrying about all the wrong things.
anyway I won't comment further other than to say that 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.
it was gawd awful slow though.
for the record the computed minimum drag speed for my aircraft is 80 knots.
you guys can be the experts from hell as far as I am concerned.
I fly the way I fly and that is it.
2500 rpm, leaned and know the fuel flow.
back in the old days
it wasn't that hard and no one ran out of fuel.what is the limit of usable fuel??? who gives a fcuk. ever heard of 45 minutes reserve???
if the last two litres of usable fuel in the tank worry you then sonny jim you are incompetent. you are worrying about all the wrong things.
anyway I won't comment further other than to say that 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.
it was gawd awful slow though.
for the record the computed minimum drag speed for my aircraft is 80 knots.
you guys can be the experts from hell as far as I am concerned.
I fly the way I fly and that is it.
Very informative post Jaba.
Couldn't agree more about fuel flowmeters/totalisers. But, they should be crosschecked against actual tank fills every so often. They can be calibrated down to +/- 1%
Another point to watch is the accuracy of tachometers. Running an optical tacho over the panel top every so often might be revealing of errors in the panel tacho.
happy days,
Couldn't agree more about fuel flowmeters/totalisers. But, they should be crosschecked against actual tank fills every so often. They can be calibrated down to +/- 1%
Another point to watch is the accuracy of tachometers. Running an optical tacho over the panel top every so often might be revealing of errors in the panel tacho.
happy days,
you guys can be the experts from hell as far as I am concerned
Seriously, I think you know what you are doing. Fact is as Jabba pointed out, most pilots have very little understanding of the mixture knob and don't know what they are doing (with it). The crap I hear around the traps about mixture use makes me cringe. Jabba seems to have analyzed the event rather well.
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27/09
Thanks for asking.I am not sure your question is making sense, but let me have a go and see if I clear it up for you. 75% power at any point on the graph is meant to be 75% of 160HP. Nothing else.
It is possible to create 75% ROP or LOP. Say you had 24.5" and 2500 RPM as a rough guess, this will be 75% power, and the mixture can be varied a lot while on the rich side of peak (and more the point from 75dF ROP and richer as power drops off once you are less than 75dF ROP) and the power is fundamentally unchanged.
It is also possible to achieve that same 120HP while LOP by having say 26.5" and 2500RPM and a fuel flow of 30.5 LPH which as a guess is going to be around 40dF LOP.
But no matter how you produce the 120HP, the airframe should do the same speed. It can't have two different TAS.
The laws of physics apply equally to all men/women and things!
By the way when you look at these POH graphs for the Piper (most models if not all, and many others, they say Best Economy, well that is completely false they are nowhere near it. And that I guess is determined by what you call close.
We spend an hour Sunday after lunch teaching critical thinking on POH's, as once the bulk of the class is taught, then critical thinking can be applied. You would be surprised if not alarmed at the examples we provide.
Your last question, yes once on the lean side of peak EGT, the fuel flow determines power so yes it is the power lever. The throttle is still throttling the air flow, and it is most efficient WOT. Think of a diesel engine, it operates LOP all the time, and it is fuel flow that determines HP.
Hope that helps.
This graph below details the principals you need to understand to determine most things.
Courtesy of Advanced Pilot Seminars.
Thanks for asking.
I am not sure your question is making sense, but let me have a go and see if I clear it up for you. 75% power at any point on the graph is meant to be 75% of 160HP. Nothing else.It is possible to create 75% ROP or LOP. Say you had 24.5" and 2500 RPM as a rough guess, this will be 75% power, and the mixture can be varied a lot while on the rich side of peak (and more the point from 75dF ROP and richer as power drops off once you are less than 75dF ROP) and the power is fundamentally unchanged.
It is also possible to achieve that same 120HP while LOP by having say 26.5" and 2500RPM and a fuel flow of 30.5 LPH which as a guess is going to be around 40dF LOP.
But no matter how you produce the 120HP, the airframe should do the same speed. It can't have two different TAS.
The laws of physics apply equally to all men/women and things!
By the way when you look at these POH graphs for the Piper (most models if not all, and many others, they say Best Economy, well that is completely false they are nowhere near it. And that I guess is determined by what you call close.
We spend an hour Sunday after lunch teaching critical thinking on POH's, as once the bulk of the class is taught, then critical thinking can be applied. You would be surprised if not alarmed at the examples we provide.
Your last question, yes once on the lean side of peak EGT, the fuel flow determines power so yes it is the power lever. The throttle is still throttling the air flow, and it is most efficient WOT. Think of a diesel engine, it operates LOP all the time, and it is fuel flow that determines HP.
Hope that helps.
This graph below details the principals you need to understand to determine most things.
Courtesy of Advanced Pilot Seminars.
Join Date: Jul 2007
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Another point to watch is the accuracy of tachometers. Running an optical tacho over the panel top every so often might be revealing of errors in the panel tacho.
Plenty of folk, can tell some scary almost fatal experiences about this and LAME's refusing to fix what they think is not broken.
Calling Beach King......Exhibit A. He is lucky to be alive......
who the hell ever flies at 65% power on a cross country?
On cross countries I fly at 78.372% power.
back in the old days it wasn't that hard and no one ran out of fuel.
I fly the way I fly and that is it.
if the last two litres of usable fuel in the tank worry you then sonny jim you are incompetent. you are worrying about all the wrong things.
Your mission is to fly as far as you can and land with 2 litres usable left in your tanks.
It’s an ISA day and there’s nil wind.
How far can you go? Prove it with data to support your choice of altitude, cruise IAS, RPM, throttle and mixture settings.
If you rarely fly ranges at the edge of your aircraft’s performance envelope and your planning and in-flight management capability, not running out of fuel may not be the product of superior knowledge or superior judgment.
