Question: Behaviour of Laminar Flow Wings
Thread Starter
Question: Behaviour of Laminar Flow Wings
About 3.00am this morning I woke up thinking once again about the slightly curious behaviour of the Piper Lance, an aircraft I have recently become aquainted with.
The one I was endorsed on has an interesting characteristic on take off, it sort of "porpoises" a little and does not really want to climb for a second or two after breaking ground - until it accelerates a little. It also glides like the proverbial brick.
I have also recently been taught by a highly experienced and respected instructor to land it from a much faster, shallower and more stable high speed approach (just below the flap extension max. speed), smoothly bringing the power back much later in the approach than I am used to and then making use of the aircrafts ability to generate huge amounts of drag very quickly as the speed washes off. The steep "Truck falling off a cliff" approaches I've used in other aircraft are a definite no no because the drag builds up very fast in the Lance as speed washes off, and trying to flare from such a steep approach is not a good idea.
The aircraft has always seemed slightly strange to me with its big fat wings, yet it slips along nicely at 160 KIAS seemingly effortlessly.
So anyway at 3.00am the words "Laminar flow wing" appear with a question mark. A quick perusal of the web this afternoon appears to show this is indeed the case. Everything else I've flown has conventional shapes as far as I know. The POH neglects to mention this difference, which at least on the surface appears to my engineers mind to be fundamental to the care and feeding of this aircraft.
Questions:
1. Does the apparent "porpoising" and unwillingness to climb immediately suggest either a dodgy oleos or am I lifting off too soon?
2. The landing technique I've recently been taught seems to work well because of the fast build up of drag on the back of the speed/drag curve of a laminar flow wing. Is this true?
The web is rather silent as far as I can tell about handling differences on aircraft with laminar flow wings. All advice would be gratefully appreciated.
The one I was endorsed on has an interesting characteristic on take off, it sort of "porpoises" a little and does not really want to climb for a second or two after breaking ground - until it accelerates a little. It also glides like the proverbial brick.
I have also recently been taught by a highly experienced and respected instructor to land it from a much faster, shallower and more stable high speed approach (just below the flap extension max. speed), smoothly bringing the power back much later in the approach than I am used to and then making use of the aircrafts ability to generate huge amounts of drag very quickly as the speed washes off. The steep "Truck falling off a cliff" approaches I've used in other aircraft are a definite no no because the drag builds up very fast in the Lance as speed washes off, and trying to flare from such a steep approach is not a good idea.
The aircraft has always seemed slightly strange to me with its big fat wings, yet it slips along nicely at 160 KIAS seemingly effortlessly.
So anyway at 3.00am the words "Laminar flow wing" appear with a question mark. A quick perusal of the web this afternoon appears to show this is indeed the case. Everything else I've flown has conventional shapes as far as I know. The POH neglects to mention this difference, which at least on the surface appears to my engineers mind to be fundamental to the care and feeding of this aircraft.
Questions:
1. Does the apparent "porpoising" and unwillingness to climb immediately suggest either a dodgy oleos or am I lifting off too soon?
2. The landing technique I've recently been taught seems to work well because of the fast build up of drag on the back of the speed/drag curve of a laminar flow wing. Is this true?
The web is rather silent as far as I can tell about handling differences on aircraft with laminar flow wings. All advice would be gratefully appreciated.
Last edited by Sunfish; 30th Nov 2006 at 05:21.
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Sunfish
There are lots of people on here with more experience than I have (and I have no idea of your experience level) but I do have a few hours and I have flown most of the common singles (35+types) in a variety of circumstances across two very different countries. Fat wings, skinny wings, laminar flow, non-laminar flow, piddly little (or no) flaps and bloody big barn doors.
In my time I have heard a whole bunch of stories about how to approach and land in particular aeroplanes and I have seen a number of people come unstuck in a big way with a lot of bent metal the result.
I think that my basic training (in a C150) was very good in the aeroplane control/approach/flare and land area (or maybe I just have an extremely good "touch", or a lot of very good luck .......
..... because .....
I fly them all pretty much the same way. If they are big and/or heavy I maybe keep a bit more power on until coming over the fence. Have yet to bend one (yeah and I know "there's them that haven't and them that's going to").
I cannot imagine routinely approaching at near the top of the white arc apart from when I am rattling down the ILS in the Bo with a "blow torch" up my arse!
The only observation I will make is that when a laminar flow wing stops flying - you need to be in the right place above the runway - cause it is all over red rover.
I will watch with interest, the other responses to your post.
R
There are lots of people on here with more experience than I have (and I have no idea of your experience level) but I do have a few hours and I have flown most of the common singles (35+types) in a variety of circumstances across two very different countries. Fat wings, skinny wings, laminar flow, non-laminar flow, piddly little (or no) flaps and bloody big barn doors.
In my time I have heard a whole bunch of stories about how to approach and land in particular aeroplanes and I have seen a number of people come unstuck in a big way with a lot of bent metal the result.
I think that my basic training (in a C150) was very good in the aeroplane control/approach/flare and land area (or maybe I just have an extremely good "touch", or a lot of very good luck .......
..... because .....
I fly them all pretty much the same way. If they are big and/or heavy I maybe keep a bit more power on until coming over the fence. Have yet to bend one (yeah and I know "there's them that haven't and them that's going to").
I cannot imagine routinely approaching at near the top of the white arc apart from when I am rattling down the ILS in the Bo with a "blow torch" up my arse!
The only observation I will make is that when a laminar flow wing stops flying - you need to be in the right place above the runway - cause it is all over red rover.
I will watch with interest, the other responses to your post.
R
Grandpa Aerotart
Is it a T tail lance?
I think the
needs talking to...if only to clarify if that is what he really intended...if it is I wouldn't fly with him again.
I think the
highly experienced and respected instructor (who taught you) to land it from a much faster, shallower and more stable high speed approach (just below the flap extension max. speed),
Thread Starter
Conventional tail Lance. I've flown the T-tail Arrow. Approach starts at just under Vfe and the idea is to get a constant rate of descent and a smooth profile keeping the speed well up. Avoid getting too slow and avoid getting too steep - well away from coffin corner.
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sounds like a standard piper to me..won't climb until you hit a certain speed, then bobs your uncle..that speed varies from piper to piper of course but you can't just haul them off.
Grandpa Aerotart
coffin corner
What/where is 'coffin corner' as it applies to a Piper Lance?
Honestly Sunfish I have not flown a Lance in well over 20 years but I can gaurantee we didn't fly them this way. I am current in an A36 and they are not too different really and I would never even consider this method of approach....In fact I have never flown any aeroplane this way nor heard it espoused as a valid method.
As for the porpoising I would suggest the most likely reason is the aeroplane is a lot bigger than you're used to and almost certainly at a fairly forward CofG position when you fly it alone or two up...as a result your trim position is probably not correct on takeoff giving you a 'trim speed' that is higher than you want on takeoff...so you get a little PIO after takeoff.
It is the same in my Bo when I fly it without bums in the rear seats. As a result I set the trim just outside the green arc (nose up) when I fly the aeroplane with only me or only the front seats occupied.
On landing you are probably finding it difficult to get the nose up high enough at the slower speed of a normal approach...this is common with all the bigger singles when flown empty, particularly the C210.
On short finals in my Bo (when flown empty/attendant foward CofG) I trim nose up enough to feel like I am applying a slight forward pressure on the control column to maintain the correct approach path. From a normal approach speed around 1.3Vs I then pull the power at 20-30' and the roundout/flare is just like any aeroplane...aiming to touchdown at minimum speed with the nosewheel well off the ground.
This will work just as well in a Lance.
The approach you have been taught is fraught with risk...mostly control problems once on the ground.
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Find yourself a new instructor!
R
The term 'drag bucket' pops into my mind associated with laminar flow wings.
Searching the memory banks here, but I think that such a wing has a pronounced dip in the drag curve around min drag speed, meaning that if you go far either side of that, the power requirement increases more rapidly for a laminar flow aerofoil than for a more standard shape.
Maybe for the takeoff situation you're describing, you start out on the low side of the drag bucket area, then speed up into it and climb away.
Other things that rear their heads in my memory - aerofoil shape is fattest further back than normal, and if they aren't kept nice and clean, the laminar flow gets disturbed and you lose the benefits.
Something like that, anyway!
Searching the memory banks here, but I think that such a wing has a pronounced dip in the drag curve around min drag speed, meaning that if you go far either side of that, the power requirement increases more rapidly for a laminar flow aerofoil than for a more standard shape.
Maybe for the takeoff situation you're describing, you start out on the low side of the drag bucket area, then speed up into it and climb away.
Other things that rear their heads in my memory - aerofoil shape is fattest further back than normal, and if they aren't kept nice and clean, the laminar flow gets disturbed and you lose the benefits.
Something like that, anyway!
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Speaking of Laminar flow wings, this guy thinks his laminar flow wings give him a cruise of 120-130knots but a VNE of 200+ !! That's quite a difference and implies that you could simply keep throwing horsepower into this aircraft and going faster and faster until you are cruising close to vne...
http://www.tomair.com.au/html/our_aircraft.php
http://www.tomair.com.au/html/our_aircraft.php
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if she doesnt want to fly you are rotating to early. keep it on the ground a tad longer, raise the nose to the end of the runway, and let her lift herself off the ground. Note the speed as she flys and use this as your VREF.....remember aircraft also behave very differently in a wide variety of conditions, but the above method works everytime no matter what you fly (sweepback wings a differant story)
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Coffin corner refers to an altitude limit for safe operation. As altitude increases, air density, and thus lift, decreases. It follows that stall speed increases. This defines the lower speed limit at which an aircraft can operate. As altitude increases, mach speed decreases. The speed at which mach buffet sets on defines the upper speed limit at which a subsonic aircraft can operate. So at a certain altitude stall speed and mach buffet speed meet. The area just under that altitude is coffin corner, in which the operating margin is very small. The altitude in question varies depending on the aircraft and atmospheric conditions.
In the case of the Lance, you are referring to the former rather than the latter - although I think the use of the overly dramatic "coffin corner" language is part of the problem.
I don't have any time in the Lance but have plenty in the Cherokee 6 (a Lance with welded wheels).
Its all about establishing a stabilised and properly trimmed approach on final at 1.3 x Vso (80 kts (?) for the Lance?). Then do it like Chuckles says and it should work out fine - but you gotta get that big snout up!
If you can't find an instructor who can handle the Lance properly - find one who can handle a Cherokee 6.
Took me a while to do a decent landing in the stubby winged Cherokee 140 after learning in a C150.
R
Hi Sunfish,
Kinetic energy at touchdown is a function of mass x velocity squared
Be very careful attempting to land with speed in excess of minimum required as it will have an exponential effect on LDR due to increased kinetic energy over the threshold and in addition will prolong the flare and delay braking action.
Runway excursions and overruns are one of the most common ways to bend an aeroplane especially as they get heavier and faster.
Kinetic energy at touchdown is a function of mass x velocity squared
Be very careful attempting to land with speed in excess of minimum required as it will have an exponential effect on LDR due to increased kinetic energy over the threshold and in addition will prolong the flare and delay braking action.
Runway excursions and overruns are one of the most common ways to bend an aeroplane especially as they get heavier and faster.
Last edited by desmotronic; 30th Nov 2006 at 20:21. Reason: edited for spelling typo
Thread Starter
Thank you all for your comments. For those casting aspersions on my instructor, I'm obviously not explaining myself very well because I assure you he knows exactly what he is doing and has the wisdom of great age. However your comments are helping me clarify my thoughts as to what I actually think I'm doing and why.
Desmo and others, I don't actually land the Lance fast at all, I still aim to cross the threshold at Vref. The drag build up as the aircraft begins to slow sees to that. The trick appears to be to fly a relatively fast approach and final and rely on the drag build up to deacclerate much later in the approach than I am used to - quite close to the threshold.
Chimbu, thanks for your comment on trim. Two up it is nose heavy and just inside C of G. It has to be hauled off. I'll experiment with trim and see if that helps shortly.
As for landing, the method I'm trying to perfect is about flying a stable approach and avoiding the need for large changes in power settings which is both disconcerting to passengers and not particularly good for larger engines.
The chief characteristic of the Lance is the very fast build up of drag as it slows.
In other words, It has been pointed out to me that therefore flying a "steep" approach at a relatively slow speed is asking for trouble with this aircraft because when as someone put it, the wing stops flying it does so completely and you had better have airstrip underneath. You are at best risking landing gear damage and at worst copping a stall when you begin to flair and keep going down.
The other usual alternative is to hang everything out and drag the aircraft in with power - this leaves you vulnerable to engine failure, is unkind to the engine, and is disconcerting to passengers if you are constantly varying the power setting.
What has been demonstrated to me is a stable descent with two stages of flap at 20 in MAP at about 90 knots, followed by the third stage of flap on final and a gentle continuous reduction in power. The drag builds up very quickly and if you get it right, you arrive at the threshold very quietly at Vref.
To put it another way, if I did this in a C172, I would float the whole length of the airstrip.
I have a lot to learn.
Desmo and others, I don't actually land the Lance fast at all, I still aim to cross the threshold at Vref. The drag build up as the aircraft begins to slow sees to that. The trick appears to be to fly a relatively fast approach and final and rely on the drag build up to deacclerate much later in the approach than I am used to - quite close to the threshold.
Chimbu, thanks for your comment on trim. Two up it is nose heavy and just inside C of G. It has to be hauled off. I'll experiment with trim and see if that helps shortly.
As for landing, the method I'm trying to perfect is about flying a stable approach and avoiding the need for large changes in power settings which is both disconcerting to passengers and not particularly good for larger engines.
The chief characteristic of the Lance is the very fast build up of drag as it slows.
In other words, It has been pointed out to me that therefore flying a "steep" approach at a relatively slow speed is asking for trouble with this aircraft because when as someone put it, the wing stops flying it does so completely and you had better have airstrip underneath. You are at best risking landing gear damage and at worst copping a stall when you begin to flair and keep going down.
The other usual alternative is to hang everything out and drag the aircraft in with power - this leaves you vulnerable to engine failure, is unkind to the engine, and is disconcerting to passengers if you are constantly varying the power setting.
What has been demonstrated to me is a stable descent with two stages of flap at 20 in MAP at about 90 knots, followed by the third stage of flap on final and a gentle continuous reduction in power. The drag builds up very quickly and if you get it right, you arrive at the threshold very quietly at Vref.
To put it another way, if I did this in a C172, I would float the whole length of the airstrip.
I have a lot to learn.
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I'll experiment with trim and see if that helps shortly.
I know this is a statement of the obvious and you already know this but sometimes it needs repeating.
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Pa32r-300
Sunfish.
I recently sold a Lance, after we had flown about 6000 hours in it.
I would say your instructor has got it right, and the long stable approach is the way to go. This aircraft has a little more weight and inertia than the 172, and likes stable flight.
If you arrive at the threshold at the speed specified in the landing chart it will behave nicely, and the figures in the landing chart will be correct.
Make sure you know everything about the landing gear, and the emergency procedures. There's more to it than just operating a lever. The nosewheel has to go down against the airflow.
Also be aware that if you get hydraulic problems the gear will probably extend by itself, and you will fly much slower, and burn much more fuel. You may need somewhere to go.
I'm sure you will always consult the weight and balance charts, and the take off and landing charts before flight.
And NEVER NEVER leave the nose locker door unlached, unless it is FULLY open and secured, so you can see it. Most PA32's have a repaired nose locker door, because pilots let them hang free, and takeoff with them unlached.
Keep these things in mind and you will love the Lance.
I recently sold a Lance, after we had flown about 6000 hours in it.
I would say your instructor has got it right, and the long stable approach is the way to go. This aircraft has a little more weight and inertia than the 172, and likes stable flight.
If you arrive at the threshold at the speed specified in the landing chart it will behave nicely, and the figures in the landing chart will be correct.
Make sure you know everything about the landing gear, and the emergency procedures. There's more to it than just operating a lever. The nosewheel has to go down against the airflow.
Also be aware that if you get hydraulic problems the gear will probably extend by itself, and you will fly much slower, and burn much more fuel. You may need somewhere to go.
I'm sure you will always consult the weight and balance charts, and the take off and landing charts before flight.
And NEVER NEVER leave the nose locker door unlached, unless it is FULLY open and secured, so you can see it. Most PA32's have a repaired nose locker door, because pilots let them hang free, and takeoff with them unlached.
Keep these things in mind and you will love the Lance.
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part of the definition of a stable approach is to be on speed, if you are slowing, then you are requiring power changes, trim changes, nose attitude changes and are therefore not stable.
Im not knocking this slowing down thingy, as i've done it also for certain aircraft types (rightly or wrongly) but it is certainly not stable.
Im not knocking this slowing down thingy, as i've done it also for certain aircraft types (rightly or wrongly) but it is certainly not stable.
Silly Old Git
Um ..flew a Lance nearly thirty years ago and I cant recall having to think of anything except put the wheels down for landing
How do these instructors get so fc@ked up in a kiddy car aeroplane?
How do these instructors get so fc@ked up in a kiddy car aeroplane?
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Thank you all for your comments. For those casting aspersions on my instructor, I'm obviously not explaining myself very well because I assure you he knows exactly what he is doing and has the wisdom of great age. However your comments are helping me clarify my thoughts as to what I actually think I'm doing and why.
Desmo and others, I don't actually land the Lance fast at all, I still aim to cross the threshold at Vref. The drag build up as the aircraft begins to slow sees to that. The trick appears to be to fly a relatively fast approach and final and rely on the drag build up to deacclerate much later in the approach than I am used to - quite close to the threshold.
Chimbu, thanks for your comment on trim. Two up it is nose heavy and just inside C of G. It has to be hauled off. I'll experiment with trim and see if that helps shortly.
As for landing, the method I'm trying to perfect is about flying a stable approach and avoiding the need for large changes in power settings which is both disconcerting to passengers and not particularly good for larger engines.
The chief characteristic of the Lance is the very fast build up of drag as it slows.
In other words, It has been pointed out to me that therefore flying a "steep" approach at a relatively slow speed is asking for trouble with this aircraft because when as someone put it, the wing stops flying it does so completely and you had better have airstrip underneath. You are at best risking landing gear damage and at worst copping a stall when you begin to flair and keep going down.
The other usual alternative is to hang everything out and drag the aircraft in with power - this leaves you vulnerable to engine failure, is unkind to the engine, and is disconcerting to passengers if you are constantly varying the power setting.
What has been demonstrated to me is a stable descent with two stages of flap at 20 in MAP at about 90 knots, followed by the third stage of flap on final and a gentle continuous reduction in power. The drag builds up very quickly and if you get it right, you arrive at the threshold very quietly at Vref.
To put it another way, if I did this in a C172, I would float the whole length of the airstrip.
I have a lot to learn.
... continuous reduction in power = unstable approach
... hang everything out and drag the aircraft in with power ... is unkind to the engine (??)
large changes in power settings ... not particularly good for larger engines (??)
Sunfish, who has been feeding you all this crap?
I would hate to think that if you needed a large change in power you would be reluctant to stick it to your "large engine" because of some worry in the back of your mind that it might be bad for the motor.
Is a Take-off or Go-round (ie LARGE change in power) bad for an engine?
I don't think so!
R
Grandpa Aerotart
Speeds high you need to revise your definition of 'stable approach'.
Sunfish I gotta agree with rat****...you've been fed some serious bull****. Not your fault...far from it...but BS non the less.
Sunfish I gotta agree with rat****...you've been fed some serious bull****. Not your fault...far from it...but BS non the less.
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Sunfish
This is the biggest load of drivel I have seen! There are a lot of challenges in flying, but landing the PA32 is not one of them.
I had 88 hrs Total Time, when I did my PA32 endorsement (yeah, I am that old) and flew off to Orchard Beach (little sand strip on Frazer Is) with a full load of pax.
The 6 flies like a big snozzled PA28 on steroids! We are not talking the Space Shuttle.
Is there a basic problem with flying training illustrated here?
BC
This is the biggest load of drivel I have seen! There are a lot of challenges in flying, but landing the PA32 is not one of them.
I had 88 hrs Total Time, when I did my PA32 endorsement (yeah, I am that old) and flew off to Orchard Beach (little sand strip on Frazer Is) with a full load of pax.
The 6 flies like a big snozzled PA28 on steroids! We are not talking the Space Shuttle.
Is there a basic problem with flying training illustrated here?
BC