A Little Gem from CASA Experts
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LB
You said the engine is certified to run at max rated power continuously to TBO. Again, no it isn’t. It seems you didn’t read my post. The information is freely available from the FAA. A TBO in terms of the certification process, is a recommendation for private pilots and a limit for commercial ops. Either way the engine is not ‘certified’ to make the TBO at rated power or any other power. It is implied that the engine will make TBO if run at the “recommended power setting for maximum service life” - eg 65% for Lycoming.
Your point that “all mixtures are lean”: go on then, explain why in your opinion a full rich mixture is lean, or for that matter why any mixture richer than stoichiometric is ‘lean’.....
I could, if I were stupid enough, drag more than the maximum rated power out of my engine by leaning the mixture to around 25C rich of peak after take off at sea level on an ISA day with full throttle and maximum RPM. However, I’m not that stupid.
Your point that “all mixtures are lean”: go on then, explain why in your opinion a full rich mixture is lean, or for that matter why any mixture richer than stoichiometric is ‘lean’.....
A Squared:
Yes, but....., there are second order effects due to control loads and out of balance forces that need to be trimmed out, and the control reactions vary with speed. These can, in my opinion, even be felt on the humble C172.
To put that another way, the elevator and trim tabs have their own L/D curves which are independent of the wing. It is not inconceivable, at least to me, that at some points there is a mismatch and also a "sweet spot" where you are at maximum L/D and get a few extra knots or whatever its called that is termed being "on the step" because it cannot be achieved below a certain speed.
There is no equivalent effect with an airplane in flight. The airplane is moving through a single fluid medium, air. It is not lifted out of anything as a boat is when planing, the entire aircraft remains submerged completely in that single medium.
To put that another way, the elevator and trim tabs have their own L/D curves which are independent of the wing. It is not inconceivable, at least to me, that at some points there is a mismatch and also a "sweet spot" where you are at maximum L/D and get a few extra knots or whatever its called that is termed being "on the step" because it cannot be achieved below a certain speed.
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A Squared:
Yes, but....., there are second order effects due to control loads and out of balance forces that need to be trimmed out, and the control reactions vary with speed. These can, in my opinion, even be felt on the humble C172.
To put that another way, the elevator and trim tabs have their own L/D curves which are independent of the wing. It is not inconceivable, at least to me, that at some points there is a mismatch and also a "sweet spot" where you are at maximum L/D and get a few extra knots or whatever its called that is termed being "on the step" because it cannot be achieved below a certain speed.
Yes, but....., there are second order effects due to control loads and out of balance forces that need to be trimmed out, and the control reactions vary with speed. These can, in my opinion, even be felt on the humble C172.
To put that another way, the elevator and trim tabs have their own L/D curves which are independent of the wing. It is not inconceivable, at least to me, that at some points there is a mismatch and also a "sweet spot" where you are at maximum L/D and get a few extra knots or whatever its called that is termed being "on the step" because it cannot be achieved below a certain speed.
Well, yes. if you're holding a lot of control force against a lot of trim force you may be adding extra drag. That isn't what is being claimed by the "on the step" advocates.
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The fuel mixture is set to a rich setting by the manufacturer settings at the idle position. Its different for the two manufacturers this places the engine fuel system to a rich mixture in all modes of operations unless the mixture is controled via the mixture lever or an automatic belows.
The step on a float plane is this. The float in the sitting position will take the full weight of the aircraft across the whole of the hull. The step approx 2/3 down the hull is waisted toward the rear. When the airspeed is great enough the rear 1/3 is free of the water surface thus reducing drag. Thats the only step other than thoose used to enter or exit the aircraft.
For thoose that think i and others are agaist running lop consider why that is. We have absolutely nothing to gain. We not trying to sell you a thing. The advice giving is what we see.
The step on a float plane is this. The float in the sitting position will take the full weight of the aircraft across the whole of the hull. The step approx 2/3 down the hull is waisted toward the rear. When the airspeed is great enough the rear 1/3 is free of the water surface thus reducing drag. Thats the only step other than thoose used to enter or exit the aircraft.
For thoose that think i and others are agaist running lop consider why that is. We have absolutely nothing to gain. We not trying to sell you a thing. The advice giving is what we see.
We all know too much heat is detrimental to the engine. However, we are talking about a heat engine here so the thermodynamic efficiency increases with temperature. If the materials could take it we would run them hotter. It is always a compromise. It is too simplistic to say that colder is better. You could run at rich best power and get the same CHT as if leaned to BSFC but more power and a cooler exhaust valve. There are no free lunches.
You want to run an engine at 74% power. What mixture do you set, by reference to peak EGT?
Real world numbers please.
You said the engine is certified to run at max rated power continuously to TBO. Again, no it isn’t. It seems you didn’t read my post. The information is freely available from the FAA. A TBO in terms of the certification process, is a recommendation for private pilots and a limit for commercial ops. Either way the engine is not ‘certified’ to make the TBO at rated power or any other power. It is implied that the engine will make TBO if run at the “recommended power setting for maximum service life” - eg 65% for Lycoming.
Your point that “all mixtures are lean”: go on then, explain why in your opinion a full rich mixture is lean, or for that matter why any mixture richer than stoichiometric is ‘lean’.....
“Full Rich” isn’t “pure fuel”, is it? Full Rich is just the point on the lean curve that has been chosen as the mixture you get when the control is set there.
To put this another way, “full rich” is still leaner of a mixture that could sustain combustion, albeit very inefficiently.
By the way, at what mixture do you maximise the risk of detonation, all other variables like RPM, timing and manifold pressure being equal? A straight answer please.
And also by the way and as you will know, this has all been discussed before on PPRuNe, many times. For late-comers like Lookleft, here’s one example: Commercial Pilots who don't know about piston engines
It’s a more technically detailed discussion than this thread.
Flying on the step. This article seems to back up what I was told many years ago, a procedure used when power was marginal. The author is David F. Rogers, PhD, ATP, Professor of Aerospace Engineering (Emeritus), and has a page of articles at Prof Rogers
http://www.nar-associates.com/techni...ide_screen.pdf
http://www.nar-associates.com/techni...ide_screen.pdf
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Flying on the step. This article seems to back up what I was told many years ago, a procedure used when power was marginal. The author is David F. Rogers, PhD, ATP, Professor of Aerospace Engineering (Emeritus), and has a page of articles at Prof Rogers
http://www.nar-associates.com/techni...ide_screen.pdf
http://www.nar-associates.com/techni...ide_screen.pdf
And also by the way and as you will know, this has all been discussed before on PPRuNe, many times. For late-comers like Lookleft, here’s one example: https://www.pprune.org/pacific-gener...n-engines.html
I suspect that 'Lead Balloon' may be a rather junior aeromodeller, perhaps flying his first Enya 15 powered model aircraft?
So he'd have no idea of how an IO520 engine in a family owned Bonanza would operate? Things like how to run the engine at its most efficient leisure. And how to keep his life and that of his pax safe?
Clearly, he doesn't have a clue..
So he'd have no idea of how an IO520 engine in a family owned Bonanza would operate? Things like how to run the engine at its most efficient leisure. And how to keep his life and that of his pax safe?
Clearly, he doesn't have a clue..
I reccomend the course, either online or with Jabba. For most pilots, there is heaps to learn.
Like I said I could start a thread about "that Year" and it would have the same stuff. Your 18 page reference is just this thread repeating itself. It once again seems to be those who are pro APS and those who think its rubbish.
Thanks for the reference megan, Not quite an OWT afterall. In the Metro it was as described. Climbing a little bit higher above the required altitude then accelerating before reducing the power. This is what E K Gann was talking about. If you don't want to accept it thats your perogative. It does not mean that your point of view is more relevant and mine is less relevant. A bit like the LOP ROP debate.
Last edited by Lookleft; 9th Apr 2018 at 00:45.
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And he who hesitates is lost and look before you leap. Meanwhile back in the real world..
You want to run an engine at 74% power. What mixture do you set, by reference to peak EGT?
Real world numbers please.
It “is implied”? Such an important concept is “implied”? I think not. We’ll have to agree to disagree on this point until I track down the primary certification materials.
”Full rich” is just where the mixture is adjusted. It could be adjusted even richer, although it would eventually get to the point it would be too rich to sustain combustion.
“Full Rich” isn’t “pure fuel”, is it? Full Rich is just the point on the lean curve that has been chosen as the mixture you get when the control is set there.
To put this another way, “full rich” is still leaner of a mixture that could sustain combustion, albeit very inefficiently.
By the way, at what mixture do you maximise the risk of detonation, all other variables like RPM, timing and manifold pressure being equal? A straight answer please.
And also by the way and as you will know, this has all been discussed before on PPRuNe, many times. For late-comers like Lookleft, here’s one example: Commercial Pilots who don't know about piston engines
It’s a more technically detailed discussion than this thread.
You want to run an engine at 74% power. What mixture do you set, by reference to peak EGT?
Real world numbers please.
It “is implied”? Such an important concept is “implied”? I think not. We’ll have to agree to disagree on this point until I track down the primary certification materials.
”Full rich” is just where the mixture is adjusted. It could be adjusted even richer, although it would eventually get to the point it would be too rich to sustain combustion.
“Full Rich” isn’t “pure fuel”, is it? Full Rich is just the point on the lean curve that has been chosen as the mixture you get when the control is set there.
To put this another way, “full rich” is still leaner of a mixture that could sustain combustion, albeit very inefficiently.
By the way, at what mixture do you maximise the risk of detonation, all other variables like RPM, timing and manifold pressure being equal? A straight answer please.
And also by the way and as you will know, this has all been discussed before on PPRuNe, many times. For late-comers like Lookleft, here’s one example: Commercial Pilots who don't know about piston engines
It’s a more technically detailed discussion than this thread.
Damp test required.
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I would hope for your own sake that when flying your metro, that you weren't climbing slower than best climb and then further slowing up so much that you were finding yourself wallowing on the back side of the power curve. That would be some pretty poor airmanship.
Edit: the author of megan's article has a very poor understanding of what's going on. he refers to the U-2's operational limits as being the same as the minimum and maximum airspeed on the power required curve. It was nothing of the sort. The so called "Coffin Corner" of the U-2 was because the stall speed and the critical mach number (above whcih the airplane might tuck into an unrecoverable dive) came together as altitude increased. It had absolutely nothing to do with minimum and maximum air speeds on a power required curve.
Last edited by A Squared; 9th Apr 2018 at 02:01.
Thread Starter
On the step
A bit off thread, but some large aircraft, particularly early model B747, exhibited a marked "on the step" characteristic.
It was finally tracked down the boundary layer adhesion characteristics.
In short, in decreasing speed to a steady Mach No., the boundary layer produced less drag than accelerating to the same Mach No. The difference in power settings and fuel flow was quite measurable.
As for the case with very sub-sonic light aircraft, I am not getting unto the argument, other than to say that an aerodynamic explanation was given in the text books most of use used in the '50's/60's, and some types certainly exhibited the characteristics as described.
Tootle pip!!
other than to say that an aerodynamic explanation was given in the text books most of use used in the '50's/60's, and some types certainly exhibited the characteristics as described.
Tootle pip!!
Tootle pip!!
Hi again, oggers.
On the certification issue, FAR 33:19, headed “Durability”, said this in 1965:
(I think the current FAR 33:19 still starts with that sentence.)
FAR 33.7 deals with engine operating limitations.
I’ve always interpreted these provisions, and their predecessors prior to the advent of the FARs, as having the effect that the durability standard required the engine to make it to TBO, provided the engine was operated within the established limitations, which limitations end up in the “Limitations” section of the AFM.
Otherwise, the standard and the certification are a bit of a nonsense.
It just so happens that there is no limitation in my AFM as to how long the engine may be operated at maximum rated power, and it just so happens that I can operate the engine at maximum rated power without exceeding any of the limitations such as CHT, oil temperature etc.
Indeed, I anticipate that my engine would last longer if it were operated continuously, rather than started and stopped every few hours. Cold starts are when most engine wear and tear is inflicted.
On the mixture front, I note TCM SID97-3E. It deals with fuel adjustment procedures for TCM engines. It provides for, among other things, fuel system adjustment values.
For e.g an IO-520-B the SID specifies full power fuel flows of 23.2 to 24.9 US gallons per hour. That’s a range of 1.7 US gallons per hour.
I note this because one engine adjusted in accordance with the SID can have a full power fuel flow of 24.9 US gallons per hour, another can have a full power fuel flow of 23.2 US gallons per hour, yet both have mixtures set to “full rich”. The “full rich” setting on the second engine is leaner than the “full rich” setting on the first engine.
Both engines could be set up to have full power fuel flow of 25 US gallons per hour - out of specification - but that would still be a leaner “full rich” mixture than if the full power fuel flow was set out of spec to 25.1 US gallons per hour.
When convenient:
You’re the one flying all the precious passengers around each day. You must be setting the mixture somewhere, and doing so to avoid detonation?
On the certification issue, FAR 33:19, headed “Durability”, said this in 1965:
Engine design and construction must minimise the development of an unsafe condition of the engine between overhaul periods.
FAR 33.7 deals with engine operating limitations.
I’ve always interpreted these provisions, and their predecessors prior to the advent of the FARs, as having the effect that the durability standard required the engine to make it to TBO, provided the engine was operated within the established limitations, which limitations end up in the “Limitations” section of the AFM.
Otherwise, the standard and the certification are a bit of a nonsense.
It just so happens that there is no limitation in my AFM as to how long the engine may be operated at maximum rated power, and it just so happens that I can operate the engine at maximum rated power without exceeding any of the limitations such as CHT, oil temperature etc.
Indeed, I anticipate that my engine would last longer if it were operated continuously, rather than started and stopped every few hours. Cold starts are when most engine wear and tear is inflicted.
On the mixture front, I note TCM SID97-3E. It deals with fuel adjustment procedures for TCM engines. It provides for, among other things, fuel system adjustment values.
For e.g an IO-520-B the SID specifies full power fuel flows of 23.2 to 24.9 US gallons per hour. That’s a range of 1.7 US gallons per hour.
I note this because one engine adjusted in accordance with the SID can have a full power fuel flow of 24.9 US gallons per hour, another can have a full power fuel flow of 23.2 US gallons per hour, yet both have mixtures set to “full rich”. The “full rich” setting on the second engine is leaner than the “full rich” setting on the first engine.
Both engines could be set up to have full power fuel flow of 25 US gallons per hour - out of specification - but that would still be a leaner “full rich” mixture than if the full power fuel flow was set out of spec to 25.1 US gallons per hour.
When convenient:
You want to run an engine at 74% power. What mixture do you set, by reference to peak EGT?
Real world numbers please.
[A]t what mixture do you maximise the risk of detonation, all other variables like RPM, timing and manifold pressure being equal? A straight answer please.
Real world numbers please.
[A]t what mixture do you maximise the risk of detonation, all other variables like RPM, timing and manifold pressure being equal? A straight answer please.
Last edited by Lead Balloon; 9th Apr 2018 at 21:41. Reason: Fix error: “Latter” changed to “first”.
Opinion ping pong sounds like fun, LL...out of curiosity I had a search through the ebook of Fate Is The Hunter to find the exact phrase and see how he described getting "onto the step". It turns out to be very similar to the way my training captains described and demonstrated it to me, and how I've seen it done many times (aircraft type - larger than Metro, smaller than 747). Maybe some aircraft don't do it, maybe some do but to a degree that it isn't evident or a worthwhile technique, but there's definitely one or two types out there that is is a usable technique worth knowing about. Nothing to do with floatplanes though!
So I owned this early model 172, 6 cylinder Continental, 145HP @ 2600 RPM. From the placard on the engine: 145 HP @ 2600 135 HP @ 2500 etc. No rocket science required to work out that 100 RPM = 10 HP
So .... You could easily get 100 knots at 2500 RPM. The problem was if you pitched the nose up slightly the speed would rapidly decay to around 90 - 95. At the same time, the RPM would also drop to around 2450 so the horsepower decayed by about 5. The angle of attack also increased to maintain the same altitude with less speed and less HP.
Some experts here tell me that there is no such thing as a "step". In a perfect world perhaps there isn't but my 172 sure exhibited exactly what Ernie and a heap of others talk about. To get 100 knots it required a bit of finesse, 90 - 95 was easy but I guess in fact it had no "step". You blokes told me so.
So .... You could easily get 100 knots at 2500 RPM. The problem was if you pitched the nose up slightly the speed would rapidly decay to around 90 - 95. At the same time, the RPM would also drop to around 2450 so the horsepower decayed by about 5. The angle of attack also increased to maintain the same altitude with less speed and less HP.
Some experts here tell me that there is no such thing as a "step". In a perfect world perhaps there isn't but my 172 sure exhibited exactly what Ernie and a heap of others talk about. To get 100 knots it required a bit of finesse, 90 - 95 was easy but I guess in fact it had no "step". You blokes told me so.
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So I owned this early model 172, 6 cylinder Continental, 145HP @ 2600 RPM. From the placard on the engine: 145 HP @ 2600 135 HP @ 2500 etc. No rocket science required to work out that 100 RPM = 10 HP
So .... You could easily get 100 knots at 2500 RPM. The problem was if you pitched the nose up slightly the speed would rapidly decay to around 90 - 95. At the same time, the RPM would also drop to around 2450 so the horsepower decayed by about 5. The angle of attack also increased to maintain the same altitude with less speed and less HP.
Some experts here tell me that there is no such thing as a "step". In a perfect world perhaps there isn't but my 172 sure exhibited exactly what Ernie and a heap of others talk about. To get 100 knots it required a bit of finesse, 90 - 95 was easy but I guess in fact it had no "step". You blokes told me so.
So .... You could easily get 100 knots at 2500 RPM. The problem was if you pitched the nose up slightly the speed would rapidly decay to around 90 - 95. At the same time, the RPM would also drop to around 2450 so the horsepower decayed by about 5. The angle of attack also increased to maintain the same altitude with less speed and less HP.
Some experts here tell me that there is no such thing as a "step". In a perfect world perhaps there isn't but my 172 sure exhibited exactly what Ernie and a heap of others talk about. To get 100 knots it required a bit of finesse, 90 - 95 was easy but I guess in fact it had no "step". You blokes told me so.
Would it be fare to say that you have placed the aircraft into the correct trim position ?
Just as a matter of interest what dose the flight manual say inrgrads to the profromance of the aircraft in question ?
What our long departed and much admired 411A had to say.
What Exactly Is, "Flying On The Step"? - Airliners.net
Where does lack of excess power put you on the drag curve?
Talking of the U-2, did you know in the cruise the power was at idle.
Having flown DC-3's, DC-6's and Lockheed Constellations in the past, can say that ALL of these aircraft were climbed slightly high (100-200 feet), then descended slowly to the desired cruise altitude, while maintaining climb power.
Once level at altitude, reduce to cruise power (approximately 50% BHP) and adjust mixture to autolean, close cowl flaps and oil shutters as needed...presto, time for coffee.
ANY other method of level off at the desired cruise altitude took MUCH longer to reach the desired cruise speed, simply because these aircraft, as well as many older turboprops (F.27/FH227's for example) did not have excess power at higher altitudes, unlike many turbofan powered aircraft today.
Once level at altitude, reduce to cruise power (approximately 50% BHP) and adjust mixture to autolean, close cowl flaps and oil shutters as needed...presto, time for coffee.
ANY other method of level off at the desired cruise altitude took MUCH longer to reach the desired cruise speed, simply because these aircraft, as well as many older turboprops (F.27/FH227's for example) did not have excess power at higher altitudes, unlike many turbofan powered aircraft today.
Where does lack of excess power put you on the drag curve?
Talking of the U-2, did you know in the cruise the power was at idle.