diving onto the step
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diving onto the step
i was just wondering what diving onto the step meant. ive heard alot of older pilots use this old school term and was wondering if it is the way the aircraft sits in the air like a boat plaining on the step or if it was diving onto the level.
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"Diving onto the step" is a term used for a tecnique whereby an a/c climbs a little above the required altitude, accelerated to cruise speed and then descends to the required level. I believe the idea originated way back when many a/c were underpowered and if simply levelled out at altitude, would "wallow" along at a lower IAS and higher drag (higher A of A) configuration than if it could accelerate and thereby increase airspeed and lower A of A.
There has been much argument about whether it actually is true or not. It was a commonly used tecnique in WW 2 I believe especially for bombers and heavy transports. Don't really think it has much application in transport a/c today though. Given the excess of power available in transport a/c I doubt there is any advantage today. Maybe some types of larger g/a types might benefit. I recall in a heavily loaded Queenair, it did seem to add a few knots of IAS, and the attitude of the a/c in cruise was noticeably different if carried out. But as far as empirical evidence is concerned I have none. Maybe some of the other contributors can help.
There has been much argument about whether it actually is true or not. It was a commonly used tecnique in WW 2 I believe especially for bombers and heavy transports. Don't really think it has much application in transport a/c today though. Given the excess of power available in transport a/c I doubt there is any advantage today. Maybe some types of larger g/a types might benefit. I recall in a heavily loaded Queenair, it did seem to add a few knots of IAS, and the attitude of the a/c in cruise was noticeably different if carried out. But as far as empirical evidence is concerned I have none. Maybe some of the other contributors can help.
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Yes your right teapoo, diving onto 'the step' is in reference to an aircraft being able to gain velocity and efficiency by climbing slightly above your cruise altitude and then diving down again to level off at the intended altitude, which in basic terms, is supposed to set the aircraft up in a manner similar to a boat planing along the water.
Here is just one article I found doing a quick search that reasons that there is indeed such a thing as getting onto the step.
Is There a Step?
I don't know enough to say myself wether or not there is such a thing as getting onto the step, some people say its a load of rubbish, others swear by it.
Here is just one article I found doing a quick search that reasons that there is indeed such a thing as getting onto the step.
Is There a Step?
I don't know enough to say myself wether or not there is such a thing as getting onto the step, some people say its a load of rubbish, others swear by it.
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Had to use this technique on several aircraft when it was warm outside and heavy inside.
Coastwatch configured Shrike, Jetstream
and BAe 146
It allows you to jump from from left side of the drag curve to the right side, if you know what l mean, and there is decernable increase in speed and a reduction in AoA for the same drag(?)
Worked for me anyway when l used to fly!
Coastwatch configured Shrike, Jetstream
and BAe 146 It allows you to jump from from left side of the drag curve to the right side, if you know what l mean, and there is decernable increase in speed and a reduction in AoA for the same drag(?)
Worked for me anyway when l used to fly!
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A very good example of an airplane that this procedure will work with is the PBY.
Due to its power to weight and high drag it may not accelerate to best attitude, dag configurayion. By leveling off a couple of hundred feet above your desired altitude you can accelerate to the best attitude / speed by using the extra height to gain A.S.
( Five or ten knots make a real difference if you are airborne for fifteen or so hours. )
It is also useful to regain speed lost due to turbulence degrading your speed / attitude.
So yes there are aircraft that this procerure will work with.
Cat Driver:
.....................
The hardest thing about flying is knowing when to say no.
Due to its power to weight and high drag it may not accelerate to best attitude, dag configurayion. By leveling off a couple of hundred feet above your desired altitude you can accelerate to the best attitude / speed by using the extra height to gain A.S.
( Five or ten knots make a real difference if you are airborne for fifteen or so hours. )
It is also useful to regain speed lost due to turbulence degrading your speed / attitude.
So yes there are aircraft that this procerure will work with.
Cat Driver:
.....................
The hardest thing about flying is knowing when to say no.
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I seem to recall through foggy memory that the technique works well for a very small gain (as professionals , aren't we always trying to do our best), on anything with a cruise speed determined by a engine power output (piston, some turbo props), rather than a speed schedule, as in heavy jet transports. Another technique I've seen used to achieve the same outcome was to engage the altitude hold on the autopilot, then gently pull BACK on the column, which causes the trim input to unload the main tailplane (elevator trim under more stress though) the aircraft then accelerates slightly, and the column pressure is slowly released. Not advocating this process though as I am least likely to be voted as 'top test pilot of the year'. (see results of last licence renewal sim check )
)
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It's IMHO pure physics, aerodynamics and that curve folks.
More or less significant as the folks here say, depending on the available grunt. and how hard you are pushing the envelope.
The manufacturer has set up or rigged the aircraft to have all of the angles of incidence, attack, drag and thrust vectors summing to the best result, at the recommended cruise speeds and power settings in the book usually the top line. Any other configuration is just costing you money. I'll deal with the "thrashing it" at those settings later if you wish.
In general terms and I dont know how the big kids operate the big kids aircraft but the principle has to be the same.
If you are say, turbocharged or have the luxury of being able to accelerate to CRZ after levelling off before reducing to a CRZ power then it's probably not necessary although a bit of extra height and dive might speed up the process.
If you aren't or your CRZ power settings are the climb power settings then pushing over at or approaching your assigned altitude and waiting may/will get you there eventually, but as mentioned above you may spend some time hanging off the back of that curve while you struggle to climb over it.
For example in a heavy normally aspirated single past full throttle height.
I know it worked for me, if only to get going a bit quicker sooner and a few knots over 3 or 4 hours can add up to around 5 minutes.
Just depends on how accurately and economically you want to operate. the aircraft. For me apart from that, the sheer fun of the intelectual exercise of getting everything spot on and striving for nav to +- 500 metres track and +- 10 seconds on time was worth it for the result.
But then I'm a Virgo and we do tend to be a bit anal.
BSD
Correct, the A/P, apart from being your best friend unless you know how it thinks and the logic it uses to operates the aircraft it can be a false one too. You will know you've got it right when there are no pitch or heading surprises on connect or disconnect.
I've sat there ( for a little while anyway) watching poor autopilots work themselves to death or disconnect trying to overcome the way the pilot has set up the aircraft. And he is sitting there complaining that the A/P is no damn good and wanders around etc blah blah.
More or less significant as the folks here say, depending on the available grunt. and how hard you are pushing the envelope.
The manufacturer has set up or rigged the aircraft to have all of the angles of incidence, attack, drag and thrust vectors summing to the best result, at the recommended cruise speeds and power settings in the book usually the top line. Any other configuration is just costing you money. I'll deal with the "thrashing it" at those settings later if you wish.
In general terms and I dont know how the big kids operate the big kids aircraft but the principle has to be the same.
If you are say, turbocharged or have the luxury of being able to accelerate to CRZ after levelling off before reducing to a CRZ power then it's probably not necessary although a bit of extra height and dive might speed up the process.
If you aren't or your CRZ power settings are the climb power settings then pushing over at or approaching your assigned altitude and waiting may/will get you there eventually, but as mentioned above you may spend some time hanging off the back of that curve while you struggle to climb over it.
For example in a heavy normally aspirated single past full throttle height.
I know it worked for me, if only to get going a bit quicker sooner and a few knots over 3 or 4 hours can add up to around 5 minutes.
Just depends on how accurately and economically you want to operate. the aircraft. For me apart from that, the sheer fun of the intelectual exercise of getting everything spot on and striving for nav to +- 500 metres track and +- 10 seconds on time was worth it for the result.
But then I'm a Virgo and we do tend to be a bit anal.
BSD
Correct, the A/P, apart from being your best friend unless you know how it thinks and the logic it uses to operates the aircraft it can be a false one too. You will know you've got it right when there are no pitch or heading surprises on connect or disconnect.
I've sat there ( for a little while anyway) watching poor autopilots work themselves to death or disconnect trying to overcome the way the pilot has set up the aircraft. And he is sitting there complaining that the A/P is no damn good and wanders around etc blah blah.
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Hi,
What an interesting read!
I was wondering if one of the more experienced drivers could expand on the actual technique used for this, especially with regards to a light piston-twin (eg Baron, Duchess)
For example, at TOC do you leave climb-power set when initiating the descent back to cruise altitude (in order to make the most of available engine power, especially above FT height)? Or would you set up cruise attitude/power first, and then let her drift down to your nominated cruise altitude?
Also, how high would you go above cruise altitude initially before commencing the "dive onto step"? I ask this because I know ATC gets the $h!ts if you go more than 250 -300 feet above your cleared level in Class C or E, at least on the East Coast anyway.
Any advice greatly appreciated, as I'd like to give this a go myself next time.
Cheers
What an interesting read!
I was wondering if one of the more experienced drivers could expand on the actual technique used for this, especially with regards to a light piston-twin (eg Baron, Duchess)
For example, at TOC do you leave climb-power set when initiating the descent back to cruise altitude (in order to make the most of available engine power, especially above FT height)? Or would you set up cruise attitude/power first, and then let her drift down to your nominated cruise altitude?
Also, how high would you go above cruise altitude initially before commencing the "dive onto step"? I ask this because I know ATC gets the $h!ts if you go more than 250 -300 feet above your cleared level in Class C or E, at least on the East Coast anyway.
Any advice greatly appreciated, as I'd like to give this a go myself next time.
Cheers
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Yep the ole dive certainly works. Hot heavy 150 over dive down and bang your at your cruise speed.
Its fun riding the thermals on the AP as the nose goes down as you go up...
AUTO PILOTS...
In my time I have found so many pilots that do not understand the basic concept let alone have been taught correctly on how to use an autopilot. Its amazing - try it grab a pilot throw em in a plane and ask em about the ap - then when you get no correct answer ask em to read the destruction book.
Must say the Bendix, Centuries etc are great when they work. First time I jumped into a plane with a brand new STEC like a true pilot did not read the destructions and took a while to figure it out...
Its fun riding the thermals on the AP as the nose goes down as you go up...
AUTO PILOTS...
In my time I have found so many pilots that do not understand the basic concept let alone have been taught correctly on how to use an autopilot. Its amazing - try it grab a pilot throw em in a plane and ask em about the ap - then when you get no correct answer ask em to read the destruction book.
Must say the Bendix, Centuries etc are great when they work. First time I jumped into a plane with a brand new STEC like a true pilot did not read the destructions and took a while to figure it out...
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Definitely used to work for the C207!
I'd climb 200' above my cruise altitude, level off, let the aeroplane accelerate (often this did not occur) at climb power, set cruise power but with the manifold pressure a smidge below what I wanted, descend down to my desired cruising altitude and presto - on height, cruise power set and usually going five knots faster (105kts instead of 100kts!).
This was all done in class G airspace, so no ATC issues.
Jex
I'd climb 200' above my cruise altitude, level off, let the aeroplane accelerate (often this did not occur) at climb power, set cruise power but with the manifold pressure a smidge below what I wanted, descend down to my desired cruising altitude and presto - on height, cruise power set and usually going five knots faster (105kts instead of 100kts!).
This was all done in class G airspace, so no ATC issues.
Jex
Yes the technique does work and by work I mean get you up to cruising IAS quicker.
The amount of benefit will depend on type.
As to the ATC problem, 100-150' is normally enough but 250' is better. Closing any cowl flaps prior to reaching TOPC assuming T & Ps are okay also helps.
Strangely, this is fundamental CPL training stuff, or at least it was for me and is for my students.
The amount of benefit will depend on type.
As to the ATC problem, 100-150' is normally enough but 250' is better. Closing any cowl flaps prior to reaching TOPC assuming T & Ps are okay also helps.
Strangely, this is fundamental CPL training stuff, or at least it was for me and is for my students.
Yes, a good technique to use above full tx height in pistons...although only in smooth air, as thermal/convective turbulence wipes out or adds to your gains at its will.
As for Autopilots, HA I fully agree with you, but the problem lies in the training. Most pilots may get to use an autopilot on their IFR training, but even then the instruction is nothing short of "push this button, push that button." I for one had that expurgated training.
Then the move to the first job is on C2** somewhere, with no autopilot, and THEN three years later you crack the IFR twin with the fancy stuff...it's little wonder autopilot skills are not up to scratch.
As for Autopilots, HA I fully agree with you, but the problem lies in the training. Most pilots may get to use an autopilot on their IFR training, but even then the instruction is nothing short of "push this button, push that button." I for one had that expurgated training.
Then the move to the first job is on C2** somewhere, with no autopilot, and THEN three years later you crack the IFR twin with the fancy stuff...it's little wonder autopilot skills are not up to scratch.
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How to use the STEP
BC, I have used the step method for a few years in different types from M210 where the TAS improvment was usually 3 to 5 kts and the light & cabin class twins. It works well in this class due to the lack of excess thrust available in CRZ (as pointed out earlier).
The method is ;
Usually 200 ft above selected CRZ works well ( and it keeps you in tolerences)
Set the aircraft in CRZ config, PWR, Cowl flaps (least drag config) and trimed. (normal CRZ)
Once the aircraft has accelerated as much as its going to, which in the cabin class twin is after approx 2 to 4 minutes. Lower the nose and descend to the selected crz altitiude.
Several things get working for you on the descent, and by the way I think the word DIVE is not correct, I have always found a slow decent with only minor attitude change works best. Be sure to level off slowly with minimal attitude change just to maintain height. The hope here is that you will have a slightly less AoA and therefore less drag (its really a poofteenth, but it does seem to help)
The effect appears to be :
foward incline of the lift vector reduces induced drag, therefore with set power gives more speed, plus reducing the angles on the THRUST and WEIGHT vectors gives a very small FWD component which seems to help as well.
Problems with the STEP are :
Any turbulance and you can forget it, as the benifit is outweighed by the constant changes required and control (AP) use.
If you need to raise the nose attitude at all you have lost the effect, therfore any climb means loss of step and having to set it up again.
(Note that the same effect can be had from entering rising air, where the aircraft is pitched forward to maintain ALT the speed increases, if you can maintain the slightly lower nose attitude when exiting the rising air you will carry a few extra KTS)
As I said earlier it does seem to work in some types, but I don't belive it works in all ACFT. There are many articles on this technique (lots from the US) with many for and against.
I belive it does work sometimes and does,nt at other times.
Give it a try and find out, I will help improve the piloting skills.
By the way it do'nt work in the Dash.
As for AP use, couldent agree more GAUNTY, and god forbid HA you are so right ( did I say that). If its fitted to the ACFT there must be a operating instruction for it, and you MUST read and know how to operate it including the normal and abnormal operation.
The method is ;
Usually 200 ft above selected CRZ works well ( and it keeps you in tolerences)
Set the aircraft in CRZ config, PWR, Cowl flaps (least drag config) and trimed. (normal CRZ)
Once the aircraft has accelerated as much as its going to, which in the cabin class twin is after approx 2 to 4 minutes. Lower the nose and descend to the selected crz altitiude.
Several things get working for you on the descent, and by the way I think the word DIVE is not correct, I have always found a slow decent with only minor attitude change works best. Be sure to level off slowly with minimal attitude change just to maintain height. The hope here is that you will have a slightly less AoA and therefore less drag (its really a poofteenth, but it does seem to help)
The effect appears to be :
foward incline of the lift vector reduces induced drag, therefore with set power gives more speed, plus reducing the angles on the THRUST and WEIGHT vectors gives a very small FWD component which seems to help as well.
Problems with the STEP are :
Any turbulance and you can forget it, as the benifit is outweighed by the constant changes required and control (AP) use.
If you need to raise the nose attitude at all you have lost the effect, therfore any climb means loss of step and having to set it up again.
(Note that the same effect can be had from entering rising air, where the aircraft is pitched forward to maintain ALT the speed increases, if you can maintain the slightly lower nose attitude when exiting the rising air you will carry a few extra KTS)
As I said earlier it does seem to work in some types, but I don't belive it works in all ACFT. There are many articles on this technique (lots from the US) with many for and against.
I belive it does work sometimes and does,nt at other times.
Give it a try and find out, I will help improve the piloting skills.
By the way it do'nt work in the Dash.
As for AP use, couldent agree more GAUNTY, and god forbid HA you are so right ( did I say that). If its fitted to the ACFT there must be a operating instruction for it, and you MUST read and know how to operate it including the normal and abnormal operation.
Hey HA where you learn all this 5hit brudda,
quote:
In my time I have found so many pilots that do not understand the basic concept let alone have been taught correctly on how to use an autopilot. Its amazing - try it grab a pilot throw em in a plane and ask em about the ap - then when you get no correct answer ask em to read the destruction book.
Dat good 5hit man, I knew a pilut like dat up Darwin way
quote:
In my time I have found so many pilots that do not understand the basic concept let alone have been taught correctly on how to use an autopilot. Its amazing - try it grab a pilot throw em in a plane and ask em about the ap - then when you get no correct answer ask em to read the destruction book.
Dat good 5hit man, I knew a pilut like dat up Darwin way
