Hey guys what's up it's Jon from Fly8ma.com and today we're going to be
talking about a really interesting topic. A lot of people have questions about
this one. It's what's the difference between a high wing aircraft and a low
wing aircraft. So how does moving a wing like three feet lower to the ground
really change how the aircraft flies and you might be kind of interested to hear
what the answer really is because a lot of people think that just by moving the
wing down makes a huge difference it kind of does and kind of doesn't so we're going
to walk you through all the characteristics of how that really
affects how the airplane flies. We're going to look at a couple different airplanes
like Moonies Cherokees Sierra's Cessna 172s and kind of walk you through each
one. The different characteristics of how they fly and the different
characteristics of how the wings are built. That's what really affects how
these airplanes fly more so than just the location of the wing on the actual
aircraft structure.
Okay so the first thing I want you to notice is we walk up to this regular old
172 is how flat the wing is. Basically how little dihedral there is knowing
it's relatively even all the way across. It's not tilted up or tilted down. Next
thing is we walk around the side here. Take a look at the width of the wing
relative to the length of the wing. So basically the aspect ratio of the wing.
Is it really long and skinny or is it really short and fat and then we're
going to go ahead and walk into the wing root here and look out down the wing and
notice how the wing root is angled up more in the wing tips. The wing tip is
tilted down a little bit with a lower angle of attack. Lower angle of incidence
and the wing root has a higher angle of incidence so it's a higher angle of
attack as the aircraft's flying along so those things all couple together really
determine the differences in how the aircraft's going to fly camber dihedral
ratio and the angle of attack are our main things that we're going to be
talking about today so hopefully you know the definition of those four terms
but if you don't we'll do a quick review here. So first thing dihedral we've got a
nice flat wing here in our Cessna 172 and if this wing happened to be tilted
up a little bit more we would say it had a lot of dihedral. And what the dihedral
does is ultimately when the aircraft's in a bank it's going to make it want to
write itself and go back to wings level. We have all that vertical lift trying to
tilt the aircraft back and this horizontal lift contributing to the
turning of the aircraft but as the aircraft skids to the side it wants to
level itself out just because the air is pushing down on the high wing and not so
much on the lower wing so that dihedral contributes to stability in making the
aircraft want to be wings level. So when people think that oh it's a high wing
therefore it's more stable because there's all that weight underneath it,
well it just doesn't need as much dihedral compared to a lowing aircraft.
So it's top-heavy. It's going to tip over no simply by adding dihedral to the
wings we can add a lot of stability and make your craft fly straight and level.
Just the same as a high wing aircraft with all that weight slung underneath
the wing. Now our next two key terms camber and ratio can be really how thick
the wing is. Thicker wings can develop more
lift at slower speeds but also generate more drags. They're better for slower
aircraft. Thinner wings develop less lift at low speed but they still develop lots
of lift at high speed so they're better for faster aircraft. So you can still get
lots of lift out of a thin wing just have to go a lot faster to do so. Now in
terms of ratio, ratio is really going to be the width compared to the length of
the wing. So when we have like a glider with really long thin wings that can fly
very high angles of attack and have a very low stall speed shorter wings are
good because there's less drag because they're just pure less wing out there
but they need much faster air speeds to develop much lift and get above their
stall speed. You'll typically find short wings will really sink at low speeds
like a rock and an long thin wings will tend to float a long ways float down the
runway just a glider might where it can just float in ground effect forever now
angle of attack we've covered before in previous videos but remember it's the
angle between the cordon line and the relative wind so the angle at which the
wing is meeting the air around it not the pitch angle the aircraft but the
pitch angle that the air is actually meeting the wing at as it's flying
through the air so the difference between the cord line and the relative
wind so now let's go ahead and take a look at a lowing airplane so we're going
to walk over this Piper Cherokee over here and take a look at how that wing is
shaped different than our 172 so the first thing to notice as we walk up here
is how wide this wing is and it's not tapered at all it's very short and very
wide it's very deep it it's about probably 4 feet deep and only a 30 foot
wingspan compared to the 182 about a 36 foot wingspan also we've got a very
thick wing all the way out to the tip so the camber is the same from the wing
root to the wing tip compared to 172 where it tapers off and the camber gets
a little thinner towards the tip as we walk out to the frontier you'll notice
there's a lot of dihedral in the wing the wings are tilted up much more
compared to the 172 where it has much Flattr wing so that he drools
contributing to the stability it's going to require more aileron use in a
crosswind compared to a 172 it has this Hershey bar wing this other Piper
challenger here to the right also has I'd say Hershey bar wing where it
maintains I camber all the way out to the tips so the tip is trying to
generate just as much lift as the wing root and it's not going to stall first
there's certain devices on here to prevent that a it's a short wing so
there's a lot of washout basically high pressure coming from the bottom going to
the top to lower the angle attack on the wing tip there's a wing fence on this
airplane that helps stop lateral flow or span-wise flow and that ensures that you
have good aileron control all the way through our stall or as your approaches
stall rather than having to make changes like twisting the wing like I do on the
172 we can look at this lowing airplane a cirrus here and you'll notice there's
still dihedral there for stability but a little less so because they're less
concerned with stability on this airplane compared to speed they want a
little bit more speed so they have less tae-hee drool there it's a tapered wing
so they have a nice thin wingtip out there so it's designed to go a little
faster and to ensure that you have a lure on control through a stall er as
your approaches stall they go ahead and they actually almost cut this wing in a2
and they have the wing tip at a much lower angle of incidence so a lower
angle attack as you're flying along and the wing roots and you'll also notice
these little silver triangle shaped pieces of metal on the leading edge of
the wing roots and that actually will induce a stall at a lowering of a
taxable force the wing or just stall at a lower angle attack so you'll get a
buff it and you'll feel the controls and will also create a nose down pitching
moment at the wing root before the tip stalls so the idea is of the airplane
approaches a stall you'll still have a lure on control you will be likely to go
into a spin but the nose will drop down and you'll get the shaking in the
airframe but you know hey let the controls forward and let the nose drop
to recover and lower the angle so let's just go ahead and talk about
these different wing shapes for a moment here between our series and our cherokee
so the charity is got these short fat wings that aspect ratio that the idea is
it's good for when you're cruising at high speed but it's not going to want to
fly at a super high angle attack does you're going to need a little bit more
airspeed to get the thing flying now the other caveat here is it's a Hershey bar
wing the same camber from the wing root all the way up to the wing tip that
means we're calling for the same amount of lift proportionally from the wing
root as the wing tip so as we're flying along at a thousand feet we have high
pressure air coming from the bottom of the wing onto the top of the wing
causing wingtip vortices we effectively lose the last little bit of our wing tip
let's just say we lose a foot of that wing well it's a short wing it's only a
thirty foot wingspan so when we lose that last foot of the wing
proportionately we're losing more lift leaving ground effect in flying you know
a twenty thirty fifty a thousand feet on a Cherokee then the amount of lift we
lose and leaving ground effect on something like a cirrus with longer
wings and a tapered wing so we're calling for less lift at the wingtip so
when we leave ground effect in the Cirrus and we have the high pressure air
start to seek the low-pressure on the top and effectively cut off that last
little bit of our wingtip we're not losing as much lift so there's not going
to be as much of a noticeable difference on a cirrus leaving ground effect as
there is own Cherokee Cherokees can carry a lot of weight and can take off
and flying ground effect but a lot of people have put four people on these
little Cherokees that just can't really handle it and get out of ground effect
lose that last foot of the wing so to speak and have to pitch up to maintain
more lift from the rest of the wing increasing the angle of attack
increasing drag and then they start to slow down settle and they want up
hitting the trees at the end of the runway because they were able to get up
flying in ground effect as soon as they left ground effect the airplane simply
couldn't provide enough lift because of that shorter wing so is one better than
the other not really it's just important to realize that if you're coming into
and say like in a cherokee knee chopped power and flair 20 feet it's going to
bleed off speed pretty quickly and drop like a rock compared to if you fly that
same cherokee down to a foot or two in chopped power and flair well let's get
up float and flare much more like a normal airplane much more like a cirrus
or a 172 would because the Searson wants them need to have that tapered wing
where they're not calling for as much lift from the wingtip so the difference
in the gain and loss of lift entering your leaving ground effect just isn't
quite as noticeable as it is with something like a Piper Cherokee so
what's a little takeaway here well if you happen to be flying a Cherokee or
short winged airplane at gross weight maybe before you leave ground effects
make sure you pick up an extra few knots and accelerate the airplane to be wide
before you climb out leave ground effect so you know you're on the front side of
the power curve rather than getting on the back side where you're going to
induce a lot of drag leaving ground effect other things to look at here in
our Cirrus is we have these fancy leading-edge devices the idea is they're
going to keep us more safe by having a lower angle of incidence with that split
wing at our wingtip giving the aileron authority throughout you know the
approach to stall obviously if you stall the entire wing you lose a luron
Authority but the idea is that the wing route could stall without the wing tips
tolling and the pilot would still have a lure on authority to keep the wings
level and not hopefully not roll into a spin although these airplanes do have a
tendency to wind up in spins um couldn t enough they have a parachute
mounted to them so hopefully that can help yeah there's also these little
fancy leading-edge devices here those little silver triangle shapes things on
the leading edge of the wing root and the idea behind these aren't actually
induce a stall they actually cause flow separation at a lower angle attack from
the top of the wing to create buffeting sooner so that the pilot will hopefully
realize oh man I can feel buffeting through the control sticking through the
airframe I'm about to stall and recover but throughout that whole time period
hopefully he still has a laronne Authority it also can cause a loss of
lift from the wing route which would hopefully cause a nose down pitching
moment lowering the angle attack on the airplane continuing to give you a lure
on Authority with the low angle to tack up the wing tips and hopefully
recovering from the stall they're helping you recover from the
stall by allowing the notes to drop down on its own so that's the idea with those
little triangles on the leading edge of the wing
they don't decrease your stall speed sound like a stole kit it's actually
increasing the stall speed or lowering the angle of attack at which the
aircraft will stall or that part of the wing will stall for as a safety measure
now lastly the series has less dihedral why do they choose this you know if it's
less stable why not bend those wings way up well obviously when you bend the
wings up you start to develop horizontal lift even when you're in flight than
supposing each other so you're developing lift it's not really
contributing to anything when that lift is just being vectored off the sides and
not contributing to lifting the airplane up so it causes more drag as if you're
causing if you need more lift to keep the airplane in the air then you have
more drag on the overall airframe so a flatter wing is going to be less drag
but you need some dihedral and a lowing airplane just for stability sake so
cherokee being a trainer they put lots dihedral and make it very stable and a
cirrus a little bit more high-performance airplane they put less
dihedral in because they're looking for some more performance out of the
airframe now that we've looked over a few different types of airplanes and
covered the characteristics of what makes them fly the way they do really
based on the wing more than it being a high wing or lowing airplane let's take
a look at a few more airplanes and make some assumptions about the way they're
going to fly so we have a moonie with a little bit dihedral in there for
stability it's a tapered wing so thicker wing
route than wingtip so we have more lift coming from the wing route than from the
tip it's not very twisted there is a slight bit of twist in there to give you
a lower angle attack or lower angle of incidence at the wingtip to help
throughout the approach to a stall we also have a leading inch device there on
the wing route that's going to help the wing root stall first and give you that
buffett and loss a lift to help the nose pitch down or recover from a stall
sooner so you're going to maintain aileron authority throw the stall as we
come over here to a high wing airplane we have another 172 to look at and same
characteristics we have that angle of incidence where the wing tip is tilted
down on the wing Rupe is tilted more up to give you more lift of the wing route
also a higher angle of attack and a stall that's going to happen sooner
there's much less dihedral because they're really relying on the weight of
the cock in the weight of the fuselage to provide
much of that stability to the airplane so less dihedral there and you also have
the tapered wing so you're going to have a little less pronounced difference
between being in ground effect and outer ground effects back over to another
cherokee we have that Hershey bar wing with the camber the same all the way
throughout there's no taper so there's going to be a pretty pronounced
difference between being in ground effect and out of ground effect it's a
shorter wing a thirty foot wingspan compared to some of those longer thinner
wings so it's going to definitely want a higher speed to get up out of ground
effect and maintain a good climb rate it's going to have tendency to plow and
drop at a steep angle at lower speeds and although this one's a little crooked
you can kind of see the dihedral there there's definitely more dihedral net
Cherokee since it's a trainer and they're looking for stability and it
happens to have one strut there that's a little low on the right side coming over
here to our diamond it has wings they're much more like that of a glider that's
going to give you good performance at high angles of attack it's going to
allow the airplane to float and ground effect it's going to take off out a
ground effect very easily and it's going to be able to maneuver at lower speeds
and higher angles of attack so it's going to have a slightly lower stall
speed now it's also a tapered wing with that little winglet there so that should
help with aileron Authority throughout a stall and we can really notice here that
aspect ratio very long wings not very wide so it really performs well at
higher angles of attack and if you come in fast in this thing and get into
ground effect you can expect it to float for a very very long time because
there's very low drag on that shape of a wing when you're just floating along and
ground effect it also has those leading-edge devices that help produce a
stall sooner so that's really selecting how far down span-wise they want that
wing to stall at and also one other important thing to notice here is we
have a t-tail on the airplane so we didn't talk much about that but
obviously with your horizontal stabilizer in a different location where
it's not going to get hit directly by the propwash as much there's going to be
less difference between applying power taking it in or out as far as what kind
of pitching moment you get since it's going to affect the trim tab less and
affect the lift over the horizontal stabilizers or less
so we've looked at a few different airplanes here and hopefully what you
guys are beating to realize is that whether it's a high wing or lowing
airplane it matters much more what shape the wing is and what's where
leading-edge devices they put on there a wing fence things like that really
affect the way it flies far more than just the wing ding three feet lower to
the ground or three feet higher of course the only thing that really
changes when you move a wing high to low or low to high is the altitude that's
going to enter ground effect at so you're going to enter ground effect
slightly sooner in these lowing airplanes but it really matters whether
or not it's tapered or it's a Hershey bar wing or if there's twists in the
wing for a different angle of incidence is going to really affect how it
performs how much aileron you need whether it's a normal landing or a
crosswind landing and whether or not you're landing fast or landing slow how
much control or authority you have and how the airplane is going to respond to
you so ultimately when you're transitioning from a high wing to a
lowing airplane or a lowing to a high wing airplane it really doesn't matter
what matters more is that you're transitioning from one airplane to
another and just find a flight instructor to go up with you explore
those different characteristics before you get into the airplane take a good
look at it on the ground really examine the shape of the wing that the designers
have put in there and then you can begin to make assumptions and expectations
about how that airplane is going to perform you can talk to your CFI about
those before you go up so you really have a better idea of what to expect
from different airplanes when you're transitioning. Hopefully you found that
helpful guys. If you have any questions at all leave them in the comments below.
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