Aerodynamics thread

[Air Force Brat]

Regarding that aero package you already brought up in the J-20 thread, by now there's really not much more I can say about it.
Apparently those ILS covers beneath the canopy are now delta shaped with a 70° sweep. I've read somewhere their main purpose is to optimize airflow eventually reaching the vert stab. Those LERXs are for the main wing.

The Typhoon, from the beginning, was designed for superior kinematic / maneuver performance in the transsonic regime. And also efficiency when supersonic. That comes at a price in the slow speed / high AoA region. Something these things are ment to correct. So that it may break in the last area where F-18 / F-16 type aircraft may still hold a slight advantage.
Nevertheless, these high AoA maneuvers of course come at the expanse of drag. And the Typhoon, being an energy fighter, will likely alway choose a rate fight over a radius fight.

Very fine report master Scratch, in fact grade A work, but engineers, Air Forces do not spend money unless they need to, that the basic design of the Euro-Fighter is being enhanced tell us there is a NEED, if the F-18 and F-16 are challenging??? imagine the T-50 and J-20 or even Su-30 or Su-35 with thrust vectoring??

No doubt the Typhoon is fast, and a very happy airplane at "altitude", all outstanding qualities, now it will have that mid altitude turning performance that is so necessary if the proverbial furball does develop?

oh and very nice picture

 

[Pmichael]

LOL, of course you don't, because that is NOT what the Brat said, I said that "AIR-FLOW" is linear, high lift devices disrupt that linear airflow momentarily to achieve the objective of creating MORE lift, slats or flaps increase the camber of the wing.

Engineers are not designing aircraft to be highly unstable in all possible situations, they are designing aircraft with "relaxed" stability in certain regimes in order to increase "agility", the ability of the pilot to quickly change direction, heading, energy levels, in order to gain a firing solution/escape vector.

Air-Flow is indeed "linear" as the aircraft is "moving through" the air in a generally forward direction, air does indeed flow from the front to the back of the aircraft, that's why the pitot tube is on the front of the aircraft, facing forward, not on the back facing aft??

The very nature of air flow is nonlinear - see the navier-stokes equations we are using for air flow. Even ignoring when we are dealing with turbulences in our air flow model.

And modern aircraft are indeed unstable in all parts of the flight - they are inherent unstable. Digital fly by wire systems exist for a reason.

 

[Air Force Brat]

The very nature of air flow is nonlinear - see the navier-stokes equations we are using for air flow. Even ignoring when we are dealing with turbulences in our air flow model.

And modern aircraft are indeed unstable in all parts of the flight - they are inherent unstable. Digital fly by wire systems exist for a reason.

My statement is accurate, the airflow over every fixed wing aircraft is linear front to back, helicopters, and VTOL aircraft excepted during take-off and landing, and I did make exceptions for lift enhancement devices "momentarily disrupting that linear airflow, in order to achieve greater lift, it is very simple physics. That's why we have a "leading" and a "trailing" edge.

I am very well aware of aircraft design and FCS, aircraft are designed to be stable in take-off, cruise, and landing configurations, in fact if you lose control, SOP is to lower gear and flaps, that does stabilize the aircraft. Fighter aircraft are designed with "relaxed stability" to enhance agility and maneuverability when engaging in ACM with an OP-FOR aircraft, the F-15 was the last fighter aircraft without demanding FCS, but FCS does stabilize aircraft that do have relaxed stability, in fact flying characteristics can be tailored by reprogramming the FCS for the flying qualities you want?

 

[Scratch]

Very fine report master Scratch, in fact grade A work, but engineers, Air Forces do not spend money unless they need to, that the basic design of the Euro-Fighter is being enhanced tell us there is a NEED, if the F-18 and F-16 are challenging??? imagine the T-50 and J-20 or even Su-30 or Su-35 with thrust vectoring??

Well, I guess there's always a need to enhance, like everyone does, otherwise we would have stopped progressing before ever reaching the jet age.

For energy fighters like the EF, I guess avoiding the furball in the first place is the way to choose. Just shoot those suckers before that.
If the opponent is trying to force exessive closure / overshoot, just use the vertical to stiff-arm the guy, keep up your speed to help evade his missiles and set up again. (Super)Hornets, due to their carrier environment induced aero layout, and those TVC birds in particular have the nasty capability to quickly bring their nose to bear on you. You'll have to be aware of that. If you are, you will do fine.

A few years ago, some german EF were in India training against MKIs. While they reported those Flanker to be serious opponents, they once more stated those TVC pugachev stunts to be overhyped. If unprepared, you could be in for a very nasty suprise. However, if you anticipated these moves, you'd just do what I described above to stay safe.

While those jets, even in the thick low-altitude air of an airshow need serious time to recover to proper forward motion, in the mid 20k' engine performance apparently was reduced to a point were the MKIs only exit from such a stunt was down. So now you're slow and predictable, no place to be in a fight.

With the Typhoons having hold themselves well even against latest competitors like MKIs and Raptors in the maneuvering arena, I'm pretty confident.

Now if only some proper enhancements in the avionic, sensor and signature reduction area were to follow ...

 

[no_name]

The very nature of air flow is nonlinear - see the navier-stokes equations we are using for air flow.

My statement is accurate, the airflow over every fixed wing aircraft is linear front to back, helicopters, and VTOL aircraft excepted during take-off and landing, and I did make exceptions for lift enhancement devices "momentarily disrupting that linear airflow, in order to achieve greater lift, it is very simple physics. That's why we have a "leading" and a "trailing" edge.

Think you guys are talking about different defs of linear. Maths/physics use linearity to refer to a class of differential equations that are straightforward to solve (like transverse EM wave), as compared to non-linear ones (like sound/large movement water wave & fluid flow).

 

[Air Force Brat]

Think you guys are talking about different defs of linear. Maths/physics use linearity to refer to a class of differential equations that are straightforward to solve (like transverse EM wave), as compared to non-linear ones (like sound/large movement water wave & fluid flow).

Actually, it seems to me that you "equation" boys, (sorry Equation, not You bruda), are missing the very clear science of "observation/experimentation", that is abundantly clear to those who are astutely observing the physical properties of the air-flow over the AIR-CRAFT.

You are counting your in-adequate equations as the end all, be all, when all real aerodynamicists, model/wind-tunnel, and ultimately build and fly to "PROVE" the theory of your concept?? that's why we build "proof of concept" models? then we have master scratch who not only does the math, he is able to apply it and to hypothesize from the math and his model, an accurate "picture" in his minds eye, of how that all plays out, and to "actualize" that concept?

I am completely inadequate in the math dept., but I have enough experience/experimentation under my belt to "visualize" airflow, as the aircraft passes "through" the air.

 

[delft]

Actually, it seems to me that you "equation" boys, (sorry Equation, not You bruda), are missing the very clear science of "observation/experimentation", that is abundantly clear to those who are astutely observing the physical properties of the air-flow over the AIR-CRAFT.

You are counting your in-adequate equations as the end all, be all, when all real aerodynamicists, model/wind-tunnel, and ultimately build and fly to "PROVE" the theory of your concept?? that's why we build "proof of concept" models? then we have master scratch who not only does the math, he is able to apply it and to hypothesize from the math and his model, an accurate "picture" in his minds eye, of how that all plays out, and to "actualize" that concept?

I am completely inadequate in the math dept., but I have enough experience/experimentation under my belt to "visualize" airflow, as the aircraft passes "through" the air.

We need equations to calculate things but you need observations to know which equations to use. There are reports with pictures to show what other people have seen, with smoke over shapes, with tufts glued to wings to see how those wings stall and many other pictures. Many of these are old and it seems modern students don't look further back than five years ....

 

[Air Force Brat]

We need equations to calculate things but you need observations to know which equations to use. There are reports with pictures to show what other people have seen, with smoke over shapes, with tufts glued to wings to see how those wings stall and many other pictures. Many of these are old and it seems modern students don't look further back than five years ....

You're so right, computers and cad/cam are wonderful, wonderful tools, and were we designing/building an aircraft, we definitely need those tools. We need to achieve whatever our design objectives may be, and we need the equations to determine wing area, load, thrust required, ad infinitum, but then its time to build/model/wind-tunnel and flight test to prove those theories.

In the case of Euro-Fighter Typhoon, we are going "back to the drawing board", in order to open up this aircrafts flight envelope, LERX, Antennae housings of a certain size and shape to manage air-flows, are all tools designed to achieve an end, and that end is to improve/enhance the flight characteristics of the "PHOON" in order to meet the potential challenges of OP-FOR, that has been shown to be a need through Red-Flags and various other excercises, where up close and personal the F-18, F-16 have a performance advantage

 

[Jeff Head]

Brat...the following pictures illustrate why you need lots of math, lots of tests, and lots of practical experience applied.

My Dad was one of the brightest aerodynamics and dynamics engineers during his generation. He worked for Vought and then Ling-Tempco-Vough for about 50 years.

He was a lead aerodynamic or dynamic engineer on multiple projects including the F-7 Cutlass, the F-8 Crusader, the A-7 Corsair and the XC-142A aircraft. He later went into their missiles division and produced a number of very cutting edge and capable designs.

The following pictures show the XC-142A being readied for wind tunnel testing. Early on, despite the very best calculations from vry broight minds like my Dad's...they had some failutres and some real life issues tro address that alluded their calculations (and at the point that the XC-142A wwas being designed, they were not novices)>

But the XC-142A wing and its ability to rotate from Horizontal to vertical, presented unique challenges at the time.

So you would get this:

Technician Sets up XC-142A Model in Wind Tunnel


Lead Engineer puzzles over XC-142A Wind Tunnel Results (That's my Dad)
​

Despite this, they continued on, and ultimately produced five prototypes for actual flight tests.

Even then, one of those crashed and tree good friends of my Dad's were lost.

But they soldiered on and ultimately produced an aircraft that fulfuilled all of the test requirements.

An XC-142A successfully making a vertical take-off


An XC-142A in level flight at altitude.
​

The US Air Force placed a production order for the C-142A Aircraft...only to have the Defense Department Secretary cancel it. (McNamara).

Just the same, NASA got a couple of those aircraft and flew them for some time.

One of NASA's XC-142A Aircraft
​

Lots and lots goes into the production of these aircraft.

Of course, back then they only had relatively simply calculators and slide rules which helped their minds and vision.

With today's 3D modeling software they can do a lot more in terms of computer modeling and tests before they actually build something to test. But in the end...they will still build the test models, the prototypes, the test production aircraft, and then the actual production aircraft.

They just may be able to do so with a lot less chance of loss, and fewer of them...if they do their jobs right.

 

[Air Force Brat]

Brat...the following pictures illustrate why you need lots of math, lots of tests, and lots of practical experience applied.

My Dad was one of the brightest aerodynamics and dynamics engineers during his generation. He worked for Vought and then Ling-Tempco-Vough for about 50 years.

He was a lead aerodynamic or dynamic engineer on multiple projects including the F-7 Cutlass, the F-8 Crusader, the A-7 Corsair and the XC-142A aircraft. He later went into their missiles division and produced a number of very cutting edge and capable designs.

The following pictures show the XC-142A being readied for wind tunnel testing. Early on, despite the very best calculations from vry broight minds like my Dad's...they had some failutres and some real life issues tro address that alluded their calculations (and at the point that the XC-142A wwas being designed, they were not novices)>

But the XC-142A wing and its ability to rotate from Horizontal to vertical, presented unique challenges at the time.

So you would get this:

View attachment 13768
Technician Sets up XC-142A Model in Wind Tunnel

View attachment 13769
Lead Engineer puzzles over XC-142A Wind Tunnel Results (That's my Dad)
​

Despite this, they continued on, and ultimately produced five prototypes for actual flight tests.

Even then, one of those crashed and tree good friends of my Dad's were lost.

But they soldiered on and ultimately produced an aircraft that fulfuilled all of the test requirements.

View attachment 13770
An XC-142A successfully making a vertical take-off

View attachment 13773
An XC-142A in level flight at altitude.​

.

The good old wind-tunnel has left more than one engineer "scratching his head" in this case is it a "double entender"???? Lee Head, scratching his HEAD??? sorry bub, I couldn't resist? and I really don't know what a double entender is, but it sounds good to the Brat, so lets just "Go with what ya Got!."

My Daddy's favorite saying when we had a "steer" rounded up that was trying to jump the chute, and HE EXPECTED ME To "hold what ya got" LOL

As much as he loved flying???? WOW! did he love to FLY, he loved farming just as much, we raised Beef Cattle, Hogs, Corn, Soybeans, and Alfalfa, he was a "Farmer"!