Monday, February 10, 2020

Flying? What's that?

So...There I was *... enjoying a cup of coffee on a cold Saturday morning pondering how I was going to vote in the current election.  Would I vote for this one, or that one, or another?  What's it to be?  Why would I chose this one?   Questions,  but no answers.

No, Beans, it's not the 2020 Presidential Election!  The only way a democrat is going to get my vote is if I'm dead.  Voting democrat seems to be a frequent occurrence among the post-living voters.

Just sayin'.

No, I was pondering the critical voting on the background photo for the Chant's new header.  In the commentary, Brother Tuna, our Naval representative (No, Beans, not Belly Button representative!  Although....He does sometimes ponder the world in relation to that.) had asked a question about this picture.


Specifically, he posted: "I like #3, but I'm not sure why the Canuck is Strike Lead. Haha."

I had responded that he was flying the slowest airplane.  Which is true.  But it took me a minute to figure out why I knew that instantly on seeing the picture.  The thing that cued me was #3 the F-16.  I started to peck out an explanation, but quickly ran afoul of blogger's comment limitations.

So....Because, Sarge said "You see, we are a blog about flying.", we're going to talk aboot flying. (My best Canuckistanian accent in that last sentence.


Yes, Beans, this is an actual picture of me in flight!
Source
 

The thrust vector (without moveable nozzles) is along the longitudinal access of the aircraft as is, in the opposite direction, Drag.  Weight always points at the center of the earth.  Lift is always applied at a 90o angle to the longitudinal axis.  Rolling the aircraft around that axis is how you change where you're going.  

Flying occurs by managing the force differential of those vectors, constantly.  Indeed, from Engine Start to Shutdown, it's all about managing force differential.  

Adding thrust (aka pushing up the throttles) gets you out of the chocks in the morning.  Reducing thrust and adding drag gets you back in the chocks when the mission is done.  Similarly, weight pulls you towards the center of the earth, generally stopping you approximately 4000 miles short of that goal.  (Some folks have tried to break the low altitude flying record.  Most of them have only tied it.)  Lift is what changes your direction in all three planes of motion.

But...juvat...how do you create lift?

Excellent question!  And one that took me quite a bit of time in Pilot training to get beyond the 3 step understanding of flight I started with.  That would be:

1) Pull stick back...Rocks get smaller
2) Push stick forward....Rocks get bigger
3) Pull stick back hard.. Rocks get bigger again

But, I finally did.  (I mean, they wouldn't have let me graduate otherwise.)

So, how does lift occur.  Well, the way I remembered it is air molecules are like running buddies.  They have to stay together, but the evil wing comes along and splits them apart one on the top of the wing and the other underneath.  The one on the top of the wing has to run further because the top of the wing is curved and therefore longer.  The molecule on the bottom has a shorter distance to run, so he's got more energy when he gets to the back side of the wing and is therefore able to "lift" the wing.

Trust me, when you get asked a question on how an airplane flies at 3AM in the morning while standing at attention in front of the assembled Instructors and fellow Students, something simple to jog your brain is essential.

But it's also partially true.

So, back to our potential masthead picture.  Look at the right side of the picture.  Notice the smoke trails.  The F-16's is at a different angle than the others, it's pointed down.  Which means that the jet is pointed slightly higher up than the others.    He has to do that because of the airspeed.  If he were to match the other's pitch angle (actually known as angle of attack or AOA), he would not be able to maintain altitude.

AOA is the angle between the longitudinal axis of the aircraft and the forward vector of the aircraft.  (In English, the difference between where it's pointed versus when it's traveling.)  The Canadian jet (CT-114 Tutor, although according to this article, the Snow Birds may change this year) has a relatively straight wing which produces a lot of lift, but also drag, so is a slow speed aircraft.  The F-16's wing is fairly small, 300 square feet, but is built for speed which generates the lift for it.  The only way he can generate sufficient lift to maintain altitude while maintaining a constant speed is to increase the AOA.  Thus, his nose is above the others.

But, juvat, isn't the F/A-18 a high speed airplane also.

Yes. Yes it is.  However, it's got two things going for it.  Much like the F-15 it has a cambered airfoil.  Which means the underside is curved and the shape of the wing is different as moves from the fuselage to the wing tip.  Additionally, the F/A-18's wing area is 500 square feet, so it generates more lift at slower speed.
Found this document when looking for description of "Camber", you should read it when needed to remedy a sleepless night
Source
That camber and wing size (the Eagle's wing area is 608 square feet), give both exceptional maneuverability at low speed.

So,  if you're going to fly level, but at a slow speed, you've got to point the nose high in the air?

Yes.






But...
Cool site to fool around on at this Source

You don't want the airflow to do what is happening in this picture.  Separating from the wing.

That is called Stall.  Stall is bad.  Stall is what causes "Rocks to get bigger" (#3 above).  The best way to recover from a stall is relaxing back pressure on the stick.  Which is fine if you've got altitude to recover.  If not,  you become one of the many who have tied the low altitude flying record, or hopefully, just the airplane does.




The other way is to power your way out, as the Lawn Dart above does.  He's not actually stalled, but is on the verge of it, and his engine is what is keeping him flying.


This next video describes the actual scientific version of how a wing flies if you're interested.  More precise than my 3AM brain trigger, it is the vector of the air flowing over and under the wing that provides the lift.

But....Lift is Life!














*Standard juvat caveat

35 comments:

  1. Well there you have it, in a nut shell so to speak.

    We are an aviation blog at heart.

    Well explained!

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  2. Or the example of aerobatic airplanes with symmetrical cross-section wings, that generate lift only via AoA. Helps with inverted flight... (Yay airshows?)

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    1. Ahhh, the power of negative G's. Never liked them. Stuff flying around in the cockpit. You can never strap in hard enough to keep your butt in the seat, and if you try, you lose feeling in your legs. No matter how hard the crew chief tries (and they try hard) all the dust and other trash magically learns to fly right into your face.

      However, it is fairly effective when someone's saddled up for a gun shot.

      Not that that ever happened to me, nor that I had to resort to that type of maneuver. Nope Never!

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    2. Negative G’s? Neeeurgh, I think maybe I’ll keep my desk job.

      https://youtu.be/AtpUhKSFcnc

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    3. Great video! Felt myself unconsciously performing the anti-gloc straining maneuver. (He wasn't doing it the way I was taught. It's more of a forced exhale and quick inhale rather than yelling, but hey whatever works. Besides, he's flying....I'm not.)

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  3. I sorta knew the four factors of flying, but now I actually understand them. Thank you.

    During my fifteen minutes of flying the Cessna, the pilot talked about renting an aircraft that could do aerobatics and doing some loops and rolls. Sadly that never happened.

    I think I mentioned this before but it bears repeating.
    I have a tremendous respect (near awe) for those who pilot these aircraft.

    Good post.

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    1. Thanks, John. We live about 5 miles from the town's airport. There's a Pitts Special hangared there. He comes out quite regularly and does acro over my house. Bastige! I know he's doing it deliberately to make me jealous, I can see him smiling.

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    2. Oddly, my brain immediately popped up a mental image of a biplane when I read Pitts Special.
      I visited YouTube to check out some Pitts Special flying and as much as I would like to be a passenger during aerobatics, I'm concerned that my behavior might result in my callsign being, John Who Screams Like A Little Girl.But it would be simply awesome.


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    3. Evidently, one can be yours for the low, low price of $46K.

      Sarge? About that raise you've been promising....

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    4. Damn, that's practically giving them away!

      No way I'll get that past the Appropriations Committee, aka The Missus Herself.

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    5. But Sarge, as soon as your post retirement career as a world famous writer takes off, (takes off, I did that on purpose) you will need a corporate aircraft to travel to book signings.
      And I know there is a guy in Texas who just might be able to find room to stow the aircraft for you.

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    6. I like where you're going with this John.

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    7. Rent free! (with appropriate usage rights)

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    8. John, re: being a passenger in a plane doing aerobatics. I'm right there with you. I would love being a pilot flying aerobatics, but being a passenger? Nope, nope, nopity nope.

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    9. Being the pilot gives you a bit of warning not available to other, non-pilots, on board. I learned to watch my student’s heads from the back seat to get a quarter second warning of what the planned to do next in a defensive air to air ride. Course it was also wise to keep track of the guy behind you also. Perhaps that’s why my neck hurts nowadays.

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  4. Fantastic stuff & awesome picture!
    I'm not smart enough to understand all that esoteric jargon, but I know someone who will.
    Sharing the link.

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  5. I kinda knew that, too.
    Your explanation and graphics make it simple.
    Too bad it isn’t easy.

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    1. Well, the first time I was asked to explain how an aircraft is able to fly, my answer of "Pure F'in Magic", got a laugh all round and a request to report to my Flight Commander for further discussion.

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  6. Very good class on lift and Angle of Attack (AOA)and how they are life.

    Then there's the low-speed yaw due to not enough thrust and not enough control over the vertical stabilizer. Seen that a few times at Patrick when the F-16s first started showing up. Asked my dad why he went white watching them, and he said they were about to slip and fall. Then he explained how he lost one of his pilot buddies in Korea from him going too slow and just yawing down (flameout on landing approach.) He said the plane just slid left from 500 feet and that was that. He was quiet for the rest of the day. Weird, as an ex-pilot, he didn't like watching planes. I guess too many bad memories or something.

    Never saw the A-7s do that. Those beefy little runts just looked too pissed off to ever fall out of the sky. Heck, they looked angry enough to fly without fuel, though I know that was an impossibility, just looked it.

    As to the picture of you, well, I know why your left hand isn't showing.






    Your watch is weighing it down.... :)

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    1. Ah yes, the dreaded Stall + Yaw = Spin. I never liked spins. We practiced them quite a bit in the T-37 phase of UPT. We practiced Hi-AOA rolls in the F-4 which because of the aircraft's airflow characteristics, (at High AOA, the ailerons are not very effective and are more prone to yaw the aircraft rather than roll and Hi AOA is by definition close to a stall. Refer to the formula above. I can (and do) still recite the boldface procedures for Out of Control and Spin in the F-4.

      The Eagle? No problema. She would stall, but generated so much lift (even the fuselage generates lift) that easing off the back pressure slightly would recover it.

      Well, since my right hand is waving at you (all fingers, not just one), my left hand must be flying the airplane.

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    2. What? You can' work the stick with your knees? Slacker.

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  7. Fun stuff juvat! Little bits of understanding make watching airshows much more funner. Clean/dirty passes are a fun lesson to watch. And dissimilar form as you've illustrated so well. It's interesting that the Legacy Bug has such a fearsome rep as a low speed/high alpha gunfighter, yet the Blues jet it replaced -- The A-4 Super Fox -- is even better in that arena. Particularly in cold air and at very low weight, when J52-P408 delivers 1:1 thrust to weight. Of course you can't fight a war with a slick bomber flying on fumes...

    And it is magic, the magic just comes with rules.

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    1. As I heard over and over in my flying career, "The only time you can have too much fuel...is when you're on fire." I think that goes double when you're on a carrier.

      Yep flying by the rules = magic.

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  8. Yerp... Aerodynamics and airflow... And it's FUN to stall out a MIG 25 below 10000 feet, then get a 'bit' unhappy...

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  9. Years ago I saw an amazing demonstration of an F 14 at the Reno Air races. The pilot was demonstrating how slow he could go.

    The wings of course were fully extended and at a very high angle of attack

    he just seemed to walk across the runway.

    Juvat obviously as an F-15 pilot your experience is far greater than my 200 hours of Cessnas and Pipers.

    But I was taught if you are in a stall you have to drop the nose not just released back pressure but move that stick forward.

    And I had another instructor that demonstrated at least with the Piper did if you were constantly on with the rudders and keeping it coordinated your plane will not stall. Is this true for all of them?

    It doesn’t matter how high you are because if you stall low enough you’re going to hit nose first anyway

    At least that’s what I was taught

    Now if you really want to have some fun get into a spin when you have a about eight hours and wasn’t expecting it

    On the way to getting my license I screwed up every which way

    That episode did teach me that failure to fly the plane and be aware of what it is telling you that things can happen in an instant

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  10. William, I could be mistaken, but i believe all planes will stall at some airspeed. The STOL airplanes in Alaska might stall at single digits. And VTOL planes can hover, but their engines are what keeps them airborne not lift on the wings. Your comment about lowering the nose vs releasing back pressure is probably valid for the type of aircraft you fly. The goal is to get air flowing properly over the wings. Releasing back pressure (aka stop doing what you did to make the plane stall). The second step is to get it flying. Bold face for the F-4 Out of Control procedure demonstrates this:
    1) Stick-Forword
    2) Ailerons and rudder - neutral
    3) If not recovered- Maintain Full forward stick and deploy drag chute.

    #1 is the “release back pressure”. #2 helps avoid adverse yaw. “Stall +yaw = spin” #3 would force the nose of the aircraft down helping to break the stall.

    I used #1 and 2 many times in the F-4 (air to air fighting requires flying on the edge of the envelope) but never had to use the drag chute for anything other than landing.

    Thankfully.

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    1. I'm a day late and a dollar short, but I suspect, Juvat, that your crew chief would have not appreciated you deploying said screw-up stopper 'chute like that.

      I love the vid on what makes wings fly. Over on the AOPA boards and others, there are essentially wild west shootouts on Bernie v. Isaac making the planes go up in the air. (Personally, I say they usually work together, and share the load--with Bernie working harder the faster ya go, and Isaac working harder the slower ya go, until finally, both turn in their resignations. That said, it's all AoA, anyway. But most little aluminum planes, if that Critical AoA is exceeded at high G-loads enough, will also eventually shed their wings. They don't seem to fly well without said appendages.

      All that, and I'll say this: All the scientists and even that video is wrong. The only physical law that makes an airplane fly--especially little put-put planes--is one written by Benjamin Franklin. If you don't have Benjamin in your pocket, that plane ain't flyin'! :D This I've attested to all too often. Grrr. I need more Benjamins! :P

      Love the comments love the explanations.

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  11. (Don McCollor) (a belated quote from Bert Stiles' "Serenade to the Big Bird" [B17, WW2])..."The air speed indicator froze up and we stalled out...It isn't a very bright play to stall out with a maximum [bomb] load"...

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    1. Yes, that is generally considered a "Bad Thing". But, since he used past tense in the sentence describing it, one would assume that it wasn't an "Extremely Bad Thing".

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    2. (Don McCollor) (they had been assigned a dog of a B17-24 missions without an engine change). Omitted from the quote was: "Sam [the pilot -Bert was copilot] punched the nose down and we came out five hundred feet below the rest of the formation. 'That was close,' was all he said".

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