For your answer:

Provide data for the Tomahawk.
1) planform
2) airfoil (or airfoil distribution)
3) incidence and twist distribution


BTW, a Tomahawk has a thrust/weight in the 1/4 category. Nowhere near 1/1. It is a "cruise" missile. As per Wikipedia, the Tomahawk weight = 2900 lb, with a Williams F107 engine that has a Sea Level Static (SLS) thrust of 670 lbs (BTW, the installed thrust available at cruise is very likely a bit less than the 670 lb SLS value). A Tomahawk has a lower T/W than your garden variety Boeing 737 (or Air France flight 447 Airbus). Something about no take-off distance constraints... Ya know, a quick google will help your education on the subject.

add: I have a little bit of knowledge on this particular subject (cruise missiles). My name is on the patent for one of the current inventory cruise missiles... although the bulk of my aircraft design experience is on more traditional aircraft.

One example of a T/W>1 aircraft exceeding stall alpha:
(I cannot paste the Wikipedia link, google "Pugachev's_Cobra" and select the wikipedia entry, for some reason the system bounces the link due to "bad link")

Note carefully the comment

Quote:

In case of the Su-27, initially the pilot disengages the angle of attack limiter of the plane, normally set at 26°.[1] This action also disengages the g limiter. After that the pilot pulls back on the stick hard. The aircraft reaches 90–120° angle of attack with a slight gain of altitude and a significant loss of speed. When the elevator is centered, the drag at the rear of the plane causes torque, thus making the aircraft pitch forward. At that time the pilot adds power to compensate for the lift loss. In a properly performed Pugachev's Cobra, the plane maintains almost straight flight throughout the manoeuvre; the plane does not roll or yaw in either direction. Proper entry speed is significant because, if entering at too low a speed, the pilot might not be able to accomplish the manoeuvre; entering at too high a speed might result in the g-force sufficient[clarification needed] for the airframe to be damaged, or for the pilot to lose consciousness.

That post-stall drag is pretty annoying to a pilot that thinks "speed is life". Cool for airshows though.

If your goal is to hover, or to decelerate, then post stall maneuvers are appropriate. Having a T/W > 1 has zero bearing on whether the aircraft exceeds the stall angle of attack (AOA is AKA alpha).

Christ, his statement was perfect for the situation he described, is there any need for this witch hunt **** which usually leads to wasting everyone's time.

Actually it's not.

An aerodynamic stall has nothing to do with the thrust capability of the engine(s) involved.

Very cool! Angle of attack looks to be ~90°, at least momentarily, with no loss of altitude.



Don't try this in an airliner, or a Cessna!

-Uwe-

NZ wrote..

BTW, a Tomahawk has a thrust/weight in the 1/4 category.

(Yeah, that occurred to me about 1:05 after posting last night; Tomahawk was just the first missile that popped into my head while writing that.)

So, make it a Saturn V; and apply my question to its control fins: Self-evidently, maintaining efficient laminar airflow across them is not a necessary component in keeping the rocket aloft by the generation of lift. The control fins are only there to aid in pointing the rocket; they have no other purpose.

Genesis wrote..

An aerodynamic stall has nothing to do with the thrust capability of the engine(s) involved.

Stall is rendered moot with sufficient thrust (i.e., Saturn V).

Bonin was seemingly under the mistaken impression he was piloting a machine with thrust in excess of weight; alas, while the theory was sound (i.e., Saturn V), his equipment was inappropriate to the task.

Thecat wrote..

Christ, his statement was perfect for the situation he described, is there any need for this witch hunt **** which usually leads to wasting everyone's time.

This.

What we have here is a grand convergence of at least a quarter-century's worth of unchecked mediocrity worming its way throughout all facets of an industry: pilots who don't know how to fly; instructors who apparently don't know what to teach or lend greatest emphasis to, flight schools concerned with quantity over quality (and part of a political culture which increasingly forbids telling anyone they're a failure, or permitting the smart to be seen as "better"), aircraft design engineers making an idiotic flight control system which manages to become implemented after presumably at least a decade of various and sundry hundreds of others in varying official capacities all being aware of it without anyone going, "Hey, wait a minute; gobs of people are going to die as soon as two incompetents have their hands on it at the same time...."

A thread detailing the litany immediately devolves into ankle-nipping.

Endarkenment.

Is urine in the stall condition when it passes the apogee?

Utter crap.

There's a misnomer in there that is highly dangerous -- that this was a conscious choice by the pilot who pulled the stick back.

That's nonsense.

A "zero-hour" trainee knows he is not piloting a rocket before he ever turns the switch on his first aircraft. He is well-aware that the only reason said device remains in the air is because the more-or-less laminar flow of air over the wing results in a lower pressure on top than on bottom, and thus lift is produced. He also knows that if that stops he either fixes that before his velocity vector toward the ground intercepts the surface of the earth or he dies.

However, this is intellectual knowledge gained in the first minutes of one's pilot training (and even before, if you've made the most-casual of study of such phenomena.) At a much-more primal level there is simply this: When one is falling uncontrollably the unconscious, animal brain attempts to go UP.

In other words your primal instincts are backwards.

Flying is not the only endeavor where this is true. It is also true when diving. In both cases if your "animal" takes over from the conscious, you will die. It is not a matter of probability, it is a matter of certainty.

Training is what everyone "sells" to avoid this outcome, but training is not particularly effective as the problem in these cases is NOT intellectual or technical knowledge of the correct solution. Training only works within certain confines; it is quite effective at providing technical knowledge of various decision paths and their consequences, but that's where the proven benefits end.

Nearly all of us have a threshold of panic where our instinctual animal takes over. Once it is crossed mental faculty and learned response no longer exists. I have never seen any objective evidence that supports a claim that once the threshold of panic is breached training or (as is said in the diving world) "muscle memory" is worth anything -- your conscious mind at that point is simply switched off and non-functional.

There are also those who believe that training and experience can eradicate the potential of panic. I do not believe this is true and have plenty of life experience that says I'm right (some of it gained by hard experience.) I also believe that it is very difficult if not impossible to test in a realistic sense one's propensity to panic under extreme circumstances which makes identifying that demon before it arises nearly impossible. Most people have that demon, incidentally, while only a few do not. Those who have it are further divided into two groups -- those who know they have it and those who do not. The latter group is very dangerous under a stress situation and are often the ones who appear to be the most-cool at the outset as they don't know the demon is there. If you have a demon but always embrace and know he's there it's much harder for him to surprise you, which means you have a better shot at keeping your intellectual capacity operative.

The few who do not have a demon, or who successfully control it, we sometimes hear about in various roles -- the soldier or pilot who is faced with what appears to be certain death and manages to cheat it. There are the stone-cold examples like our Hudson River pilot and a handful of others who had decision paths available in a situation that appeared to be one of certain death -- and yet there was one path out, the conscious mind remained in control and it found and executed upon that path.

Those who do panic (and that's most people) have different thresholds, and only the ones at a low threshold are easily detected through things like simulators because no matter how rigorous the person inside knows it's a simulation when they enter, and thus so does their subconscious.

But this comes back to the essence of this accident -- if you're in the "animal space" the only way you're getting out is if you're jolted out -- if SOMETHING breaks your animal focus.

And in this case, nothing did.

Beck, quoted in the OP, wrote..

Pointing the nose down must -- early in any flight training -- become virtually instinctive. It must be the first idea to be considered in any attitude-recovery crisis, and will almost always be the solution. It has to crawl up the pilot's spine like the instinct of a dirt-track racer to kick the ass of the car out into the turn without even thinking about it.

Breezing through the Popular Mechanics write up again, one thing is fairly clear to me: Bonin was not in "panic mode" (well, at least not initially, at any rate). He made the wrong decisions all the way down.

Entirely disagree at the point that the initial action (pulling the stick back) did not produce the expected response.

Before that point it was immaterial. After that point only exiting the animal mode mattered and system design hindered rather than assisted in that regard.

I simply do not accept that any pilot with any amount of experience does not intellectually know that in an aerodynamic stall in virtually every instance pulling back on the stick is wrong.

KD wrote..

The few who do not have a demon, or who successfully control it, we sometimes hear about in various roles -- the soldier or pilot who is faced with what appears to be certain death and manages to cheat it.

Those who cannot successfully control that demon should not hold ATP ratings. It may not be possible to train everyone who wants an ATP rating to the point where they can control their natural tendency to panic when faced with a bad situation, but training could (and should!) be designed to test for that, and fail those candidates who are likely to panic instead of pulling themselves together and doing their job, which is to fly the damn airplane.

Scuba divers and private pilots don't need to be held to this kind of standard because it's highly unlikely they'll kill a few hundred people if they do panic.

-Uwe-

So how do you test for that accurately?

That's the problem - simulated emergencies and real ones aren't the same thing, because the trainee knows when he goes into the simulation that it's a simulation.

That he performs well during the simulation cannot thus be taken as an assurance that performance will similarly be proper during a real emergency.

Certainly if the trainee fails the simulation you have to wash him out but if he passes it is not a reasonable assurance of good performance when the "real thing" happens.

Quote:

I simply do not accept that any pilot with any amount of experience does not intellectually know that in an aerodynamic stall in virtually every instance pulling back on the stick is wrong.

Look around you: manifest incompetents have managed to claw their way to the top of almost every imaginable avocation. -- The detractor of such a jaundiced viewpoint would argue that planes would be falling out of the sky if that were true. ...to which I would respond: one did.

The piloting incompetence aboard AF447 was evident long before the crash: they blithely flew right into the core of an ITCZ thunderhead complex when it was easily avoidable. During the stall-descent, flight-recorder data indicate both co-pilots yanked the stick back.

= = = =

Interesting analysis of screw-ups on the design side: http://boards.straightdope.com/sdmb/show....

Basically, the flight-control system tricked a couple of inept pilots into dipping their bird. That said; they are not absolved from blame: they permitted themselves to become detached from reality, and had no idea what their plane was doing. In short, they trusted a computer to do their thinking for them; and it worked until it didn't.

http://forums.theregister.co.uk/forum/3/....

Pilot LarsG wrote..

As technology advances it takes responsibility away from the pilots, the computer flies 98% of the route because it is more fuel efficient and cost effective. As a result pilot skills decline.

There are some advocates of pilotless airliners. Computers cannot think outside the box.

Remember, some pilots are naturals and others have to work to their limits to fly; they are not all equals.

I prefer to fly with the naturals; they make it look easy, not the adequate.

This.

Quote:

So how do you test for that accurately?

My friend Billy would maintain that nobody should be flying a big plane until they've considerable time at the stick of a tail-dragger.

Bonin was 32 years-old. -- Now, it's certainly possible to be a brilliant pilot at the age of 32 or even a lot younger if you have a lot of experience and went through a no-bull**** training regime tailored to ruthlessly weeded out misfits. But I sincerely doubt Bonin, et al, went through any "Hard Knocks" flight school.

= = = = =

http://www.nationalmuseum.af.mil/factshe....

Quote:

Flight Training Aircraft

At the beginning of the war, flight training lasted nine months, with three months of primary, three months of basic, and three months of advanced training. ....Primary training was accomplished in aircraft such as the PT-17, PT-19, PT-22 and PT-23 while basic training took place in mostly in the BT-9, BT-13, BT-14 and BT-15. Advanced training for fighter pilots took place in the AT-6, and training for multi-engine aircraft occurred in the AT-9 and AT-10 aircraft. The AT-11 was used to train bombardiers and navigators.

Ryan PT-22 Recruit, "primary" trainer for US Army Air Corps in WWII


Vultee BT-13 Valiant, "basic" trainer


Beech AT-10 Wichita, "advanced" trainer


= = = =

Today, if you flunk your school tests, you can take the course again. If your crash your plane on a simulator, you get to try again.

Back then, if you flunked your tests, you were transferred to somewhere else the military thought it could make use of you. If you crashed your trainer, a nice young chaplain delivered the bad news to your mother.

Quote:

A stall-warning means your ****ing plane is stalling; and that happens for exactly one of two reasons: not enough throttle, or too steep of angle-of-attack.

Quote:

If an airliner had a thrust-to-weight ratio in excess of 1:1, it could not stall (because it'd be a missile at that point).

Quote:

Stall is rendered moot with sufficient thrust (i.e., Saturn V).

As you would say, don't move the goalposts.

Moved, why doesn't a Saturn V need wings at all?

STFUAGTFO.

An airfoil (wing) stalls (loses lift) when it exceeds it's critical angle of attack. Period. Angle of attack is measured as the angle between the chord line of the wing (defined by drawing an imaginary line between the leading edge and trailing edge of the wing) and the relative wind (relative wind being equal in velocity and opposite in direction to the flight path of the airplane).

Even current jet fighters with a thrust to weight ratio of greater than one can stall. Ever been to an airshow and watched something like a F-18 Hornet making a "high alpha" pass? For its steady state condition, that jet is very near the critical angle of attack. A further increase in pitch without a commensurate increase in thrust (which changes the relative wind) would result in a stall and a likely crash at that low altitude. Many modern fighter jets also have computers that limit the "alpha" to less than critical.

It is important to remember that an aircraft's ATTITUDE does not necessarily reflect it's angle of attack. A fighter jet with a thrust to weight ratio greater than one CAN fly straight up and accelerate doing so, but the angle of attack stays well below the critical alpha.

As for the events leading to the Air France crash, I agree with Bezzle. The pilots either forgot basic airmanship skills, or never learned them. They failed to fly the airplane (the most important priority) with tragic results. And I can see how it happened...

When I learned to fly, there were very few automated systems, no HSI slaved gyros, no GPS, no flight directors with command bars, and no glass cockpits, Multi Function Displays, or inflight computers or data links. For navigation, we had ground based VOR, ADF, and ILS systems. Pilots HAD to have very good basic airmanship skills, and had to stay situationally aware in three dimensions. Even when flying turbine powered corporate aircraft, I made it a policy to only use the autopilot for straight and level enroute flight, and for the occasional enroute descent. All other descents, transitions, maneuvering, visual and instrument approaches I chose to hand fly, and encouraged my captains to do the same. Keeping up and being very good at those necessary basic skills, and planning and mentally staying well ahead of the aircraft were very important to me.

During the years I taught flying I remember giving checkouts to airline pilots in our Cessna aircraft at a flight school, and some of those pilots were very rusty on basic skills. Those skills had atrophied during years of programming flight computers and being only cockpit managers and observers. Today's airline pilot rarely gets any "stick time" except at takeoff and landing. So yes, I can see these guys (with contributions from a non-linked set of sidestick controllers) allowing this Airbus to maintain a nose up stalled condition all the way to impact with the ocean.

Bez,

I have to state that your inability to admit when you make a mistake can be entertaining. Rather than admit that you made an error, you attempted to change the subject (your typical phrase is "don't move the goalposts"), and then go ad hominem, then throw a childish tantrum. Did you also toss the game board as a child when you were losing?

Another aside for your aerodynamic understanding. There is little laminar flow on an airliner (or Saturn V).

As to your postulation for a missile or Saturn V as being an appropriate analogy to an airliner. You might as well postulate levitation or anti-gravity. Apples ain't oranges. A competent engineer works with factual reality, not silly extrapolations. It would be an appropriate task for you to analyze just what sea level static thrust/weight is required to get a T/W that is greater than 1 at cruise altitude. (A hint, if you get <5, you have some math errors in your analysis.)

Xoxo,
"Ankle Nipper" as you call me.

Quote:

Rather than admit that you made an error, you attempted to change the subject....

What's the subject, per the thread-founding post?

<cricket.wav>

Your motivation here is to troll and sling ad homina.

Quote:

Another aside for your aerodynamic understanding. There is little laminar flow on an airliner (or Saturn V).

"little laminar flow on an airliner"?

Wikiedpia article 'Wingtip device' wrote..

Winglets and wing fences also increase efficiency by reducing vortex interference with laminar airflow near the tips of the wing, by 'moving' the confluence of low-pressure (over wing) and high-pressure (under wing) air away from the surface of the wing. Wingtip vortices create turbulence, originating at the leading edge of the wingtip and propagating backwards and inboard. This turbulence 'delaminates' the airflow over a small triangular section of the outboard wing, which destroys lift in that area.

Laminar airflow must be important to airliners if doohickeys are attached to the ends of the wings to increase it, no?



Endarkenment

Bez,

You made a claim in a succeeding post on the thread about two methods for preventing a stall, and that is what I responded to. I have no issues with the concept that the AF 447 "pilots" demonstrated incompetence and noted that some time ago. As you are well aware, this is not what we have been discussing.

As to the latest digression on laminar flow, I guess that they shouldn't be spending research on exotic methods to attempt to get laminar flow on commercial airliners as per your expert opinion they already have extensive laminar flow...

http://www.nasa.gov/connect/chat/laminar....

Quote:

For years, people who fly or design or build airplanes have been on a quest for aviation's holy grail – laminar flow.
Laminar flow means the smooth, uninterrupted flow of air over an aircraft's wing. If you can achieve it, wonderful things happen. You become incredibly aerodynamic. You fly farther on less fuel. The really challenging part of this quest is that laminar flow is very hard to do, thanks to seams and rivets and hinges and flaps and anything that sticks out or moves. All those objects break the flow and create tiny pockets of turbulence.

Quote:

Ethan: Our ultimate goal with this project is to determine whether or not the DRE technology works as a method of laminar flow control. If successful, this technology will help to maintain laminar flow over most of a wing's surface and significantly reduce drag. This technology could be applied to a new wing design for either the traditional tube-and-wing aircraft or for a BWB.

Quote:

Ethan: Very good question. It turns out that laminar flow is very sensitive to the roughness of a wing which can depend on the paint scheme. With this experiment, we are going to make the smoothest glove surface possible for the researchers. Then we are going to paint the glove surface and "rough it up" in order to see the DRE technology works with different paint schemes.

If you are really lucky, you get some laminar flow on the the leading edge slat. The little step that is at the juncture of the leading edge slat will transition the flow to turbulent if it hasn't already transitioned due to other mechanisms (airliners have issues with premature transition due to transverse cross-flow at the leading edge due to wing sweep). Just a panel seam just about guarantees a transition, not to mention those rows of fasteners...

To get laminar flow, you need to address the items such as panel breaks, fasteners, movable surface breaks, paint texture, as well as keeping the wing spotlessly clean. Just getting a bug splat on a wing that has laminar flow results in a transition wedge behind the bug splat.

Don't believe everything you read on the 'net. I suspect that the wiki author was attempting to describe flow separation, and used a funky non-aerodynamics word "delaminated" rather than an accurate description.

If you are serious about understanding laminar flow, I'd suggest reading up about sailplanes, as sailplanes are one of the few flying vehicles with significant amounts of laminar flow. They have to work hard to get it. Fortunately, it is easier for them at the lower Reynolds number of sailplanes as opposed to airliners, without accounting for the additional issues due to the wing sweep.

From http://en.wikipedia.org/wiki/Glider_(sai....

Quote:

Due to the critical role that aerodynamic efficiency plays in the performance of a glider, gliders often have aerodynamic features seldom found in other aircraft. The wings of a modern racing glider have a specially designed low-drag laminar flow airfoil. After the wings' surfaces have been shaped by a mold to great accuracy, they are then highly polished. Vertical winglets at the ends of the wings are computer-designed to decrease drag and improve handling performance. Special aerodynamic seals are used at the ailerons, rudder and elevator to prevent the flow of air through control surface gaps. Turbulator devices in the form of a zig-zag tape or multiple blow holes positioned in a span-wise line along the wing are used to trip laminar flow air into turbulent flow at a desired location on the wing. This flow control prevents the formation of laminar flow bubbles and ensures the absolute minimum drag. Bug-wipers may be installed to wipe the wings while in flight and remove insects that are disturbing the smooth flow of air over the wing.

High surface accuracy, and very smooth surfaces are important to obtain laminar flow. The higher the Reynolds number (Re), the more strict the requirements are. Airliners have almost an order of magnitude higher Re than sailplanes, and it is challenging for sailplanes...

I'd recommend sticking to pontificating on subjects that you know and understand.

I bet you had to work really hard with your google search to avoid the various appropriate articles that discuss laminar flow for airliners (and the attendant difficulty in obtaining laminar flow. This is not very objective behavior.

A few tidbits for your education:
http://www.cleansky.eu/content/news/natu....

Quote:

GKN Aerospace has increased its participation with the ‘Clean Sky’ Joint Technology Initiative (JTI), growing involvement with the development of a Natural Laminar Flow (NLF) wing through both ground-based and flight demonstrators.

GKN Aerospace is now taking NLF wing design and evaluation work, completed in phase one of Clean Sky, into the ‘phase two’ development of a ground-based structural systems demonstrator. The Company is also set to design and manufacture major components of the NLF wing flight demonstrator, providing the metallic leading edge and composite upper cover for this innovative structure. GKN Aerospace engineers will be investigating novel techniques and technologies to achieve a structure with the right tolerances at the right price. The flight demonstrator platform will be an A340 with the outer third of the wing replaced with the NLF wing development sections. Flight tests are scheduled for 2014/2015.

A fully NLF wing is considered to be one of the key developments to reduce drag in the next generation of aircraft and has the potential to provide 3-4% fuel savings, making this a vital technology to meet critical ACARE emissions targets. However an NLF wing is very different from a conventional wing and requires changes to wing architecture, aerofoil definition and detailed design and manufacturing concepts. The more slender sections and very high tolerance surface finishes and joints also present the industry with new challenges.

http://www.flightglobal.com/news/article....

Quote:

Laminar smart wing could reduce drag by 10%
Goran Bengtsson, Clean Sky programme manager at Saab and co-leader of the technology demonstrator, adds: "It is not easy to design such a wing because the requirements on it are at levels we have not seen before in aviation."

The wing must be lighter and smoother than current designs, he says, "to enable the flow to stay laminar on a bigger portion of the wing. This creates extra complexity and we need to design and build the wing in a new way".

Saab is working on the cover and leading edge of the wing and has already made the first samples of wing section, "showing that we have the tooling technology to produce such a wing part", says Bengtsson.

The laminar wing will look different to current designs, with much less sweep, a thinner and shorter leading edge and a smaller radius to its curvature. The new wing could reduce drag by 10%, Bengtsson adds.

The flying demonstrator is due in 2014, says Bengtsson, "so, by then, this wing must be ready for flight tests. In aviation terms, that is not long."

I kinda like this one, it is a bit more near-term and achievable reality based. They are just extending the leading edge laminar flow on the tail by a little bit. Most of the flow will still be turbulent.:
http://www.flightglobal.com/news/article....

Movetonz wrote..

You made a claim in a succeeding post on the thread about two methods for preventing a stall, and that is what I responded to.

By glomming onto a fallacy of the excluded middle with the tenacity of a pit-bull in order to stroke your agenda of introducing ad homina.



Endarkenment.

You appear to redirect the discussion whenever you fall short in the logic/truth department, without addressing when the shortfalls in your claims have been appropriately refuted.

Quote:

fallacy of the excluded middle

Cite, and show the logical path to which this is applicable. I would recommend using your post declaration

Quote:

A stall-warning means your ****ing plane is stalling; and that happens for exactly one of two reasons: not enough throttle, or too steep of angle-of-attack.

as the basis for discussion rather than your succeeding posts which have the goalposts moved. My claim was that only the latter was applicable, especially as this is what is important for the case of a typical airliner and extremely important for the circomstances that AF447 found itself in due to inept pilotage.

Even Gen agreed with the refutation of the thrust component of your statement.

BTW, what say you now about your airliner laminar flow claim? Still consider that airliners have significant laminar flow? With what basis do you make this claim?

Bez wrote..

A stall-warning means your ****ing plane is stalling; and that happens for exactly one of two reasons: not enough throttle, or too steep of angle-of-attack.

Fallacy of the excluded middle, eh?

The way I read this sentence is that the very first thing you'd do to try to get get out of a stall is to increase throttle.

This is why I said:

Uwe wrote..

Remind me not to fly with you, Bez.

I'm sticking by it.

-Uwe-

Quote:

The way I read this sentence is that the very first thing you'd do to try to get get out of a stall is to increase throttle.

Why would you conclude that? What I wrote clearly didn't imply favoring one over the other.

I should think it's apparent that if you're at 37,000ft in an airliner with your nose pointed toward the moon and reading an airspeed of 90kts while the engines are screaming full-blast, then lack of throttle isn't the problem in that situation.

But put yourself in a Harrier transitioning VTOL over a cratered site with the ground coming up a little too fast for your comfort, and it's a different matter.

Uh….Guys….. I don’t want to interrupt the discussion but we’re down to 1500 feet and all the screens just went dark ….. I keep trying to pull the nose up but it’s not working…. any suggestions?