Cessna Skyhawk C-172, by Textron Aviation

Introducing the Cessna Skyhawk C172 by Textron Aviation.

This is part of a S. C I 309 aerodynamics with Butch Bennett for the March 2022 term.

This particular module will look at the aircraft selection, airfoils,

research and the physical laws associated with computing.

Airfoil performance. Let's introduce the C 1 72 Skyhawk.

This is a four seat single engine aircraft traditionally used for training here

in the United States and has been in continuous production since 1948.

This particular Skyhawk offers a very simplistic fight flight characteristics

including now updated avionics, including the G 1000 series,

lower landing speeds,

lenient stall speeds,

which will address through some performance calculations later and

they're the ideal aerodynamics for a training aircraft.

Today.

The general aircraft characteristics are very basic. It is a four seat aircraft.

One crew required.

The length is relatively small at 27 ft two inches

with a wingspan of 174 square feet for the wing area

aspect ratio is 732. Very important to this research is the airfoil type.

The knack of 24 12 with our empty weight being £1680 although in

most of our calculations will be using a max gross weight of £2550.

Making this our Maxwell useful load

of £878 and a max payload of £870.

The performance of the aircraft is relatively straightforward maximum cruise.

About a 124 max cruise speed in a trainer.

Let's go ahead now and jump into some of

the resource requirements for airfoil and the behavior.

The main airfoil data shows this to

be a relatively straightforward training aircraft.

The airfoil tools were used to be able to define the cord,

the camera and the upper and lower surfaces of the 24-12 airfoil service.

Let's look into the angle of attack.

Now we selected to generate a data model.

We used Microsoft sequel server to go ahead and

load in all the naka data across all aircraft

types so that we could look at the stall AOA A the CL levels by Naca type.

When we looked at the max C. L. And the C. L.

For minimum here to evaluate the AOA and Cl for the Skyhawk.

We came out with the stall A. O. A at 16.5 degrees.

This would be the critical angle of attack in which an aircraft

would stall again and will reference this in our performance calculations later.

This is a respective of weight

in speed

and altitude

on the critical angle of attack which is at the C. L.

Max of 1.582 and r zero lift A OA is roughly a negative 2.250 degrees.

Now let's look at some airfoil comparisons.

Not part of the assignment but I thought this might be keen

to look at in terms of assessment products as a whole.

As we start to define.

Looking at the airfoils and the AOA

characteristics around the airfoils for Cessna products.

But I wanted to bring this one up relatively quick to show the difference between

transitioning pilots for a jet versus those who come from the piston 1 72 world.

You can see the overlay of that airfoil with respect to chord line.

In Canberra is almost identical.

We went ahead and used the data model

that we had selected previously which the knack to type here for

the citation one Cessna product is the 2301 to knock a type

but you'll see that the stall, the C. L.

Max and the zero lip Aowei characteristics are almost identical to a Cessna 1

72 with remarkably small differences noted in red between the stall the C.

L. Max and the zero lift a away.

This provides trainers the ability to

move from training aircraft within the Cessna

suite of products to aerodynamically similar aircraft

here represented in their jet sweets.

Now,

as the requirements of this assignment requires

us to look at the symmetrical airfoil,

I went ahead and loaded a data model again for the 24 12 Naca type on the Cessna 1 72

and the very first Naca type for a symmetrical airfoil,

you'll see the airfoil down there below in red which is the 24 12 Cessna 1

72 and the purple which is the F 1 11 or 006 symmetrical airfoil type.

You can see in the data model that the stall AOA A. The C. L.

Max and men are very different based on the type

of naka selected in the data model.

There are some rough differences in terms

of the symmetrical airfoil which distinguishes itself different

from what we see in the 24-12 with the identical upper and lower services.

You can notice that here in the lower. Reference in purple

there is no zero lift a away due to the

cord line and the mean camera line being identical.

If you look at the data model to the left and reference the blue,

excuse me, the purple arrows, you'll see the very bottom one where the zero A.

Oa indicates zero lift.

Now the non symmetrical to 4 12 naka provides

greater lift efficiency at any given a o.

A.

With a better lift to drag ratio,

with improved stall characteristics for a non symmetrical

airfoil wing.

Alright, let's continue on and look at some of the calculated behaviors

that we have for the Cessna 1 72 aircraft.

Many of the performance and limitations of the

skyhawk are provided within the flight operations,

manual of the pilot operating handbook but we're going to confirm

some of those performance factors by

looking at specific calculations that address

speed,

wait altitude and temperature to arrive at calculated stall

speeds and lift deficiencies for the Cessna 1 72

here in the calculated stall speed.

We're gonna go ahead and address this from a gross weight perspective of £2550.

The wing area. The Cessna 1 72 is 174 square feet.

And in this demonstration we're going to look at the calculated stall speed

At c. l.

max at 1.58 To this would be the 16.5 critical angle of attack for this aircraft.

We're going to do this at an altitude of

5000 MSL which gives us a density ratio of 50000.8617

And the stadium.

The standard data points here used at 2992.

We use the calculated stall stall speed equation here which then gives

us a stall speed of 56.32 indicated on our air speed indicator.

Now we're going to reference the calculated stall speed later when we start to look

at the cl differences between cl cl max and how those might exceed C.

L. Max

and what contributions they have to stall speed.

In a later slide

Let's go ahead and jump into the lift efficiency.

We have four conditions in which were required to examine lift deficiency

for this particular aircraft and demonstrate the capabilities of the Cessna 172.

Condition one looks at how lift changes with their speed.

You have a constant AO AO AO and altitude

are held condition to how lift changes with altitude.

If the constant AOA and airspeed are held.

Whereas condition three is,

how do the required cln ao a for the Skyhawk change with changes in air speed.

And finally what happens if the required cl is larger than the C. L.

Max of the Skyhawk airfoil which we referenced just a

minute ago as we looked at the stall speed.

Let's look at condition one here.

Condition one requires us to look at the change with their speed.

If a constant AOA announced that are held with respect to lift

here,

we're going to have the skyhawk traveling initially at 55

knots and then have its speed up to 110 knots.

For this particular example,

I am using max cl cl max at the 1.582 which would be that 16.5 degree angle of attack.

The critical angle of attack.

I'm doing this for two purposes to demonstrate here uh that the aircraft is

pretty much at its full weight value at the 55 knots at £2432.29.

But when we take that aircraft still at 5000 ft to 110 indicated knots,

it's 9720 nine's of pressure to try to hold that aircraft at 110 knots

at 16.5 degrees which this aircraft won't be able to do.

So this begs the question, can this aircraft handle that?

Certainly at the 55 knots at 5000 ft,

the pounds of lift is appropriate for this airfoil.

However, when you look at this type of category of an aircraft,

being a normal category rather than a utility

category of the aircraft,

we have a part 23 limitation to 3.8 Gs load limit on the airframe,

which would bring this aircraft's weight load limit at 3.8 to £9690

in which the 110 knots at 5000 MSL would exceed that. So, with £39 over,

this shows us that we need to keep

this aircraft within a limited speed factor to avoid

structural damage but to stay inside the stall envelope for this given airframe,

let's look at condition number two,

condition number two is how does lift change with altitude? If a constant A. O.

A and airspeeder Hill.

So similar to condition one will test

the relationship between lift as altitude increases.

We should note that there is a direct relationship

between altitude and density ratio lift will decrease,

the pounds of lift will decrease as altitude increases.

So you can see first

At 100 knots,

this aircraft will be at 1000 ft MSL and will then

climb this aircraft to 5000 ft. MSL and you can see that the £2131

will be at the 1000 MSL rate, but as we increase altitude,

the lift will decrease and the formula here for that proves as we've

seen about a £200 decrease between the 404,000 ft that we increased in.

MSL

finally, let's look at number three.

Number three is, how do the required cl in the airway for the sky up,

Change with changes in air speed.

And we've done this several ways in which the sky hop will initially travel

at 100 K. I. S indicated air speed and then reduce the speed to 75 knots

At the gross weight of 2550 pounds.

Again using the same given parameters 174 square feet,

it will then travel at 3000 ft. MSL with the appropriate density ratio.

So you can see with the formula that we've used here

that the 30000.472 demonstrated at full weight at 100 knots,

But in order to achieve the same altitude at a lower air speed.

In the second formula at 75 knots, it's 0.839,

we would have to increase the back pressure and increase

our angle of attack to maintain that same altitude.

So, at a lower airspeed,

you're required to increase the AOA to maintain that same altitude.

The cl must increase at the lower speed to maintain the same altitude as well.

Some AOA and clb match there.

Mhm.

Now the example that we give at the bottom is cautionary as you increase the weight,

you will stall at a higher indicated airspeed,

the stall at the speed of which an

aircraft stalls is not influenced directly by speed,

weight or temperature.

In terms of the

angle in which the aircraft stalls. A critical angle of attack is the only component

in terms of the

lift or the airfoil losing all lifting properties.

But you will arrive at that critical angle of

attack at different speeds based on your weight.

And we're looking at the differences here between

the £1900 aircraft and a 25 £150 aircraft.

You can see it increases by seven knots.

You will arrive at the stall speed at the max cl at a higher airspeed

than you would at a lower airspeed at a lower weight of the aircraft.

And finally what happens if the required cl is larger than the C. L.

Max of your of your airfoil and what

speed regime is usually associated with that condition.

And again what we're doing here is demonstrating the

maximum performance of the aircraft in terms of C.

L. Max and the 16.5

degree A. O. A. The critical angle of attack

and what speed you would arrive at that at max gross weight which here is 56.32 knots.

So in this example if the aircraft CLS assumed it's a 1.61

that would exceed that which is of 1.58 to the C.

L. Max of this aircraft here demonstrated at 5000 ft. MSL

which would mean that the airfoil would be stalled.

The equation above demonstrate that the skyhawk at gross weight at 5000 MSL

would reach the critical angle attack at that indicated air speed at 56.32.

So based on the condition that we used in three

pilots must fly with a higher AOA at lower speeds to maintain the same altitude

or to hire a away at lower speeds to avoid a stall but not to the point in

which they reached the critical angle of attack during

the increased a a way to maintain altitude.

I hope you've enjoyed this presentation.

This has been my approach to aircraft selection and the airfoils,

research and physical laws associated with calculating

behaviors of the Cessna 1 72.

Thank you.

Cessna Skyhawk C-172, by Textron Aviation

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