The Over-Banking Tendency

Courtesy Retroyou.org

Several Sport Aviation magazine readers commented on the “What Went Wrong” article in the October issue. The article is a review of the NTSB accident report of a Lancair ES pilot who lost control of his airplane while flying in the clouds downwind of Mount Rainier.

The accident itself – a loss of control in IMC – was not, unfortunately, a rare occurrence for general aviation pilots, but what was unusual is that the airplane had a recording system embedded in its flat glass avionics system the preserved key parameters of the flight. What got readers’ attention was that a descent rate of 10,500 fpm  was recorded after the Lancair pilot lost control. How can an airplane descend that fast? 

The answer is the natural over-banking tendency of an airplane that leads to a spiral dive.

All airplanes that exhibit normal stability have an over-banking tendency that most of us don’t think about much, if at all. The tendency is always there in a steep turn, but we subconsciously correct for it unless we are disoriented.

The over-banking tendency usually begins to show itself in a bank angle of 40 degrees or more. That’s one of the reasons in normal flying the standard is to limit maximum bank to 30 degrees.

Courtesy danlj.org

As you know, as bank angle increases, lift in the up direction decreases, so you must pull back on the controls to hold altitude. In a bank of 30 degrees or less, pulling up elevator will raise the nose. In a steep bank, pulling back on the controls will steepen the bank. That’s the over-banking tendency.

The reason we don’t worry much about the over-banking tendency in normal flying is that we subconsciously add opposite aileron to defeat the over-bank. For example, when you are flying steep turns for a practice or a checkride you will pull back to hold altitude, but also, at some point, roll in opposite aileron to keep the bank angle from increasing. It is a very natural control input to make.

If you want to see the over-banking tendency in your airplane, roll it into a steep bank of 45 degrees or more and freeze the aileron position while pulling back. The more you pull, the more the bank steepens until you add aileron opposite the bank.

Now imagine that you are in the clouds and are disoriented. You are unsure of the bank angle, or overall attitude of the airplane, but you see the airspeed increasing. The natural reaction is to pull back to raise the nose and slow the airplane. But if the airplane is already in a steep bank and you pull back, the over-banking tendency takes over and the bank angle steepens.

If you’re disoriented you won’t add opposite aileron to keep the bank angle from increasing as you pull. The over-banking tendency will steepen the bank, the nose will go lower, the airspeed will increase, and you will pull harder trying to slow down. The vicious – and typically fatal – cycle of the spiral dive has developed.

Also known as “the leans,” flying in IMC in a steep bank is disorienting and can lead to improper control inputs without using a proper instrument scan. Courtesy Atlasaviation.com

In a spiral dive the bank angle increases to, or even beyond, the vertical and the nose keeps dropping. Because the up elevator is steepening the dive instead of pulling the nose up, the g-load does not increase. The NTSB reported that in the Lancair spiral dive loss of control the g-load remained constant at about 1.1 g’s. This rolling dive can lead to the amazing vertical speeds that are observed when pilots lose control in the clouds.

A spiral dive won’t damage or break an airplane because the g-loading is low, but if the pilot emerges from the clouds, regains orientation, and levels the wings, the mere act of leveling the wings can be enough to overload the airframe as the airplane noses up seeking its trimmed airspeed. Add the stick pull of a panicked pilot seeing the ground rush up and the loading will almost certainly be too much for the airframe to tolerate.

That’s why so many eyewitness accounts of loss of control accidents over the years include reports that “the airplane came out of the clouds and then I saw parts breaking off.”

Beech was a pioneer in attempting to explain the over-banking tendency, and resulting spiral dive, in the early days of the Bonanza. When pilots lost control of the slick Bonanza in the clouds Beech calculated that the resulting spiral dive would hit more than 300 mph in very few seconds.

Courtesy Airportjournals.com

Beech’s advice if you became disoriented in the clouds was to take your hands of the wheel and attempt to hold heading with your feet. The stability of the airplane would keep airspeed in check if the wings were anywhere close to level, and the rudder could do that. Keeping your hands off the controls helped to fight the urge to pull if airspeed was too high. Lowering the landing gear would add drag and help control airspeed.

If the air is turbulent, steering with your feet is going to be tough, but the advice is still pretty solid if you ever lose orientation in the clouds. If a steep bank is allowed to develop, recovery is darn close to impossible. But if you can keep the wings approximately level, the airspeed will behave as you expect it to.

This entry was posted in Airmanship, Safety, Technology. Bookmark the permalink.

27 Responses to The Over-Banking Tendency

  1. Alain ADAM says:

    I am a flight instructor and I teach steep turns in descent to my students because it can be useful to fly under the clouds if there is only a small hole to descend.

  2. larry Rachlin says:

    The problem as I see it is in the explanation. There is no such thing as a “bank” What it is, is a loop in a different plane When you pull back on the stick you are tightening the loop There is only two things an aircraft can do Go straight ahead or make a loop In an ordinary loop the aircraft “thinks” it is going up hill That is why you need more power to maintain a constant angle of bank The “turn” is accomplished by rolling the aircraft over to the desired angle and continuing the loop

    • Ross youngblood says:

      I have to disagree, as one of the forces acting on the aircraft is gravity, and generally that force is downward towards the earth. In sailplanes, gravity IS your engine, and generally the only thing a sailplane can do is fly downhill. To gain altitude, sailplanes bank to center in a rising package of air that is rising faster than the L/D ratio. Sailplanes can perform loops as well, using gravity to create kinetic energy (high airspeed) such that the airfoil is moving faster than the stall speed at the top of the loop. Banking (left or right) is the case where there is a non zero component of gravity to the pilots left or right. Looping is the case where the components of gravity are forward (increasing airspeed) and aft (decreasing airspeed). The reason more power is needed in a turn is that some of the wings lift is being diverted to change direction, and that portion of lift is no longer opposing gravity, so the plane will loose altitude. In zero gravity, there probably is no such thing as bank…relative to what. But in our gravity field, bank angle is a relationship of the angles with respect to a vector towards the earths center. At least that’s how my troubled mind thinks of it.

  3. Bill Berson says:

    Mac said:
    “As you know, as bank angle increases, lift in the up direction decreases, so you must pull back on the controls to hold altitude. In a bank of 30 degrees or less, pulling up elevator will raise the nose. In a steep bank, pulling back on the controls will steepen the bank. That’s the over-banking tendency.”

    I could not find any source that defines over-banking tendency as Mac did here.
    Usually, and especially with long winged gliders, the explanation has to do with the outside going faster. Another explanation, from the book ‘Stick and Rudder’ talks about the interaction between dihedral and the vertical tail and how the vertical tail can cause this over-banking tendency.
    In my experience, pulling up the elevator will tighten the turn radius and increase the g- loading but has no effect on the bank angle.

    Also Mac said:
    “In a spiral dive the bank angle increases to, or even beyond, the vertical and the nose keeps dropping. Because the up elevator is steepening the dive instead of pulling the nose up, the g-load does not increase.”
    Again, I think up elevator would actually result in high g-loading, so this comment could use some further clarification, I feel.
    Bill

    • Thomas Boyle says:

      Bill,

      It’s very easy to see elevator steepen the bank – just go out and do some Lazy 8s. Bank 25 to 30 degrees in level flight, then center the stick and start pulling the nose up smoothly. You can readily get to quite a steep bank angle in the middle of the maneuver. This isn’t solely due to the outside wing moving faster, nor to the turning climb effect (a side-effect of the outside wing moving faster, and not usually seen in gliders). If you imagine the circle an airplane flies around in a loop, and then tilt that circle over to the side a bit, you’ll see that at the steepest part of the climb the aircraft is effectively “vertically” banked, i.e., the wings produce lift parallel to the ground, and one wingtip is closer to the ground than the other. In this configuration the aircraft will slide toward the lower wing, because of gravity, which will induce yaw. In practice the aircraft won’t get all that nose-high (unless it’s going very fast) because of the yaw, but it will still get quite banked over. The Lazy 8 is a nice demonstration of that – as is the spiral dive.

      I agree, hauling back on the stick should produce more g, even in a turn. I could be persuaded, but the idea that more pull would only result in the nose falling isn’t obvious to me either.

  4. Pingback: The Over-Banking Tendency | Left Seat | Share My Aircraft News

  5. Cary Alburn says:

    I think you have to try it as Mac described to believe it. One of the problems is that in today’s training environment, we are told that a 45 degree bank is a steep bank–so for some folk, that’s all they’ve ever done in training. The overbanking tendency is just about nil at 45 degrees, but it increases substantially at 60 degrees. So go out (with a competent instructor if necessary) and do a series of 60 degree banks but do not use the ailerons to prevent overbanking. Very quickly, the airplane will go past 60 degrees, and if all you do is pull back, it will fall off to the downside wing into a very steep spiral. If you pull back hard enough, it may stall, but if it’s a coordinated stall, it will still fall to the downside wing.

    Unless you have some aerobatic experience, going past 60 degrees bank will be very disconcerting, as will the steep spiral which results. Most pilots think they are at 90 degrees when they’re just barely past 60, and most pilots in a steep spiral think that they are pointed straight down, when in reality they are probably only around 45 -50 degrees down.

    But going downhill at 120 mph (that’s all the Lancair was doing) and popping out of the clouds to see the earth rushing up can certainly lead a pilot to over controlling and airframe break-up. If the pilot could have resisted that excessive pull, he might have survived–just like anyone who does a loop survives coming down the back side.

  6. Dave says:

    Having lived in the Tacoma area, I would not infrequently observe that Mt. Rainier would develop these lenticular shaped clouds that would hover over the top or to the sides of it indicating extremely high winds. I would not be surprised if some wind shear / powerful down drafts may have been involved.

    Interesting discussion which addresses the aerodynamics and recovery but not the cause. The illustration showing the “Pressure nerve sensors” is misleading and incorrect. No “pressure nerves” (or more correctly “proprioceptive” sensors) are involved. The Graveyard spiral (also known as the Somatogyral illusion) is caused by the vestibular system’s semicircular canals. The vestibular system is designed to sense angular and linear acceleration. There are minimum’s and maximum’s it can sense. Typically what happens is a pilot enters into a “sub-threshold” turn in the weather that is not sensed by his vestibular system initially and then when it comes to his attention that he is in a bank, he corrects it…but now he feels like he’s in a turn in the opposite direction because he corrected it at “supra-threshold” rates resulting in strong stimulation of his vestibular system…his brain now tells him to that he is not level but in a turn in the opposite direction which then causes him to turn back into the original turn to get a wings level sensation. However this conflicts with what his instruments are telling him, which with an inexperienced pilot, results in further over corrections. With training in spatial disorientation devices or with instrument and unusual attitude training under the hood, one can learn to suppress the powerful urge to believe your body over the instruments. Seat of the pants flying will kill you. The first illustration which above, is one of my drawings from a government publication USAFSAM-TR-85-31, Dec 1986 by Dr. Kent Gillingham, titled “Spatial Disorientation in Flight”

  7. Roger says:

    There are a number of statements I take issue with when it comes to over banking and up elevator although I do agree with most of the article.

    In all the years I’ve been flying I was never taught to keep bank angle to 30 degrees or less except for passenger comfort and instrument flight. Steep turns were 60 degree bank angle.

    I agree Increasing bank angle does not increase G load, BUT up elevator does be it in a spiral dive or any other time that I can think off. Yes, the speed in a dive or spiral dive and easily exceed Vne and you an start shedding parts and stating it won’t might give inexperienced pilots the idea that all they have to do is shove the nose down in an emergency. Leveling the wings does not add G Forces, but leveling out the flight does. When I refer to leveling the wings it’s like angle of attack or in reference to the direction of flight, not the ground. IOW leveling the wings, or neutralizing the bank angle still leaves you in a dive. Coming out of the bottom of the clouds at or above Vne usually results in a LOT of up elevator where even a little would exceed the aircraft’s limits.

    It depends a lot of what you are flying and its limitations. I’ve had a Glasair III at a rate of descent close to 30,000 fpm, although it was as I passed through vertical on a split S. In the Debonair regardless of configuration the best rate of descent I can make is around 2300 fpm and that is with everything hanging out. Clean I can not come anywhere near that figure without reaching Vne. Maneuvering at or close to Vne is not normally recommended.

    • Mac says:

      Hi Roger,

      I am really convinced that pilots understand that leveling the wings is a reference to the horizon. Using that understanding, if you level the wings while diving at high speed, the g-loading will go way up. Airplanes don’t break from high indicated airspeed, but from over loading. Flutter is, of course, a different matter and it may be possible to exceed flutter margins without overloading the airframe in which case divergent flutter could break the airplane. But that is not the usual sequence of events during a loss of control in IMC.

      Mac Mc

      • Roger says:

        Hi Mac,

        That I agree with. My thinking works in reference to what ever the plane is doing at the time and I agree that instinctively coming out the bottom of the clouds with a windshield full of tree tops or corn stalks the yoke is going to come back and the wings go level with the land. Of course at that point the only distinction is going to be the size hole you make and the area covered with parts.

  8. Ernest MacQuarrie says:

    What happened to needle ball and airspeed. Center the needle and then play around with the airspeed and altiitude to figure which way you are going, up or down. If it goes faster when you pull back, you need to get right side up. At least that is what they taught us in T6′s at Randolph AFB in 1948 to Class 49A.

    .

  9. Mac says:

    Hi Ernest,

    Actually, the needle ball has been replaced by the turn coordinator with its tilted rate gyro in most light airplanes. However, the turn coordinator can provide enough information to stay right side up. But when a pilot loses orientation in the clouds, it can be very difficult–almost impossible–to regain it even with a full set of instruments functioning. No matter how much IFR flying experience you have, once you are confused about the instrument indications you are seeing, it is very, very difficult to figure out what is going on. The key is to remain in control, not try to recover control and orientation after you have lost them.

    Bests,

    Mac Mc

    • I noted a new post on this and it started me thinking.
      The steps are:Power back, stop the turn, level the wings with the horizon, and ease the nose up.

      The POH for the Deb also states if you are having trouble slowing down, lower the gear. It may be expensive, but it just might save your life.

      When I took the practical flight exam for the Private (In a Cherokee 180) it was a beautiful bright sunshiny day with plenty of wind and turbulence. I had a panel full of steam gauges for IFR flight but at my experience level I was going to be happy to be able to fly well VFR. I could see right away the turbulence was going to make that a challenge.

      While making a turn under the hood I hit an updraft that put the aircraft on its side resulting in a spiral dive. Of course at this point the DE gave me a simulated vector from ATC to turn heading 330. I had eased off on the power and at the same time applied plenty of right rudder (to stop the turn), but the Cherokee seemed to be ignoring me. At this point it was strictly “needle, ball, and airspeed” although it was in a turn coordinator. Finally the wings in the TC leveled and I centered the ball with the ailerons, shifted to the AI and slowly brought the horizon back up to level in the AI. Then I made that turn to 330 as I climbed back to altitude.
      All this time the DE kept repeating that “turn heading 330″. I finally told her I was rather busy, but once the airplane was behaving I’d turn to heading 330.

      So it is possible for a low time pilot to stop a spiral dive using needle, ball, and airspeed, *IF* they do not get distracted, a case of vertigo, or confused. I should hasten to add that a good number of experienced pilots have pulled the wings off airplanes in clear VFR weather where they had a clear view outside.

  10. Bill Berson says:

    I just realized that student pilots are not taught or required to perform spiral dives (nor are spins taught).
    My old Kershner pilot manual has only about one sentence to describe the spiral dive.
    On my last flight review the instructor asked me to demonstrate a 60 degree banked steep turn (holding altitude) and stopping exactly on a point.
    The 60 degree turn pulled two g’s.

    I never tried to do a spiral dive (and probably won’t) in my full size motorglider.
    I do teach students to fly RC models. With RC models, the spiral dive is a major problem as it is with IFR pilots because the RC pilot also gets disoriented. The full scale VFR pilot doesn’t get disoriented and the spiral is easily stopped. So I suppose this explains the lack of instruction about spiral dives in flight school.

    I will test this over-banking tendency with my RC model tomorrow.
    Bill

  11. Daniel Wisehart says:

    The explanation of over banking is flawed. In aerobatics a competion turn must be at least 60 degrees of bank. The author would have us believe that as bank angle increases the over banking tendency also increases. But this is not so. As the bank angle increases through 50, 60, 70 and even 80 degrees–if you can take the g-load–the over banking tendency decreases, not increases. The maximum over banking tendency is at 45 degrees.

    In a properly rated airport airplane you can try this for yourself–but make sure to go with someone who is aerobatic current. While you are out, practice some spin recoveries. Every pilot should be comfortable spinning an airplane that is rated for spins.

  12. Mac says:

    Hi Daniel,

    The issue is not VFR flight, even extreme VFR flight such as aerobatics. The problem comes when one is in the clouds, must rely on instruments only, and has only one chance to get it right. Spinning is interesting, but for it to apply in this situation you would need to enter the spin in the clouds and then recover with no visual reference except that gray murk of the inside of a cloud. It can be done. But do you want to count on your ability to do that? Maybe.

    Mac Mc

    • Roger says:

      Don’t forget that vertigo can manifest itself even in VFR conditions. Not as often, but many things can cause vertigo and no one is immune, even aerobatic pilots.

      Outside of flying over a lake with no horizon, a dark night with no ground lights, or accidentally flying into a cloud, something as simple as skipping breakfast, lack of sleep, fatigue, or minor illnesses such as a cold, sinus infection, flu, and many other more serious ailments can at times cause vertigo and that is a real treat be it in the clouds or VFR.

      We casually use the word, disorientation, but it is often vertigo and vertigo can be far more than a simple case of being dizzy or having lost reference to up or down and I can speak with authority on that.

      Many years ago, I had just purchased the Debonair and was bringing it home with an instructor in the right seat. (I had yet to earn the high performance endorsement, or instrument rating) This was my first time in solid IFR and had to hand fly the Deb. We were in building cumulus so it was quite a ride. We called Fort Wayne and told them we were in moderate to severe turbulence and having difficulty maintaining altitude. Their response was, “Yah, we know, the alarms are already turned off” and gave us a block altitude.

      I don’t think I have ever been that miserable. I had to not only point, but put my finger on each gauge in turn to do my scan. The turbulence was so bad I’d miss and then just set there trying to remember which gauge I’d been after. Your mind just goes into overload and shuts down or works like it’s stuck in molasses. The instructor just sat there and would occasionally tap the yoke if I was getting off altitude or course. After about 15 minutes the dizziness and nausea went away to be replaced by one of the worst headaches I’ve ever had.
      Remember, if your minds isn’t working right it doesn’t matter much if you can see the ground or not.

      One hour and 8 minutes later we flew out the side of a cumulus into clear air without a cloud ahead. I looked back…and up, and up, and up. By bending over to look out I could just see the top of the cumulus. It turned into a thunderstorm just after we got out of it.

      I later told the Instructor I had expected him to take over numerous times. His reply?: “What would you have done on your own? You handled it well, if not perfect. BTW that weather was about as bad as you ever want to get in!”

      The thing is that this kind of vertigo can sneak up on a VFR pilot as well. If it does it will be an event you will never forget! <:-)) Note that I still remember to the minute how long we were in that storm!

      Oh! The forecast had been for CAVU.

      • Mac says:

        You bring up a good point, Roger. Can all night flying, no matter how clear the sky is really be IFR? I don’t think so. I grew up in Cleveland and more than one pilot has departed from Burke Lakefront, turned north over the blackness of Lake Erie at night, and kept rolling down into the water. Many other countries do not allow night VFR. I am not suggesting we do that, but it does send the signal that flying at night is very different, and the safety record is much worse for GA pilots–either IFR or VFR–when it’s dark.

        Mac Mc

  13. Roger says:

    I love VFR night flying (in good weather). It’s usually smooth and many areas are like looking at Christmas lights, but as you noted night flight can have its pitfalls.

    Ground lights can create illusions or mirages just like slanting cloud layers in the day time. Areas without lights on a moonless night are pretty much the same as flying into clouds with absolutely no ground reference.. Flint has, or used to have, a warning on the chart for planes on final from the East. Stay on the instruments until the runway is made as there are ground light to the East that look like runway lights.

    I took off from Newberry Michigan after dropping a friend and reporter off on the way home from Oshkosh some years back. As the threshold lights passed under the wing I realized I had no vision outside. Absolutely nothing was visible. I immediately hit the mike button and told Minneapolis Center I’d like to activate my IFR flight plan (which was already on file). They came back with what I love to hear, Cleared as filed, direct KIKW. As I was passing through 5000 I suddenly realized I could see ground lights here and there while off to the South I could see lights on the northern edge of the lower peninsula. I had not flown into clouds as I first thought, rather, I was over a very heavily wooded and sparsely populated area that gave me no ground reference. What had been basically IFR even though visibility was clear and unlimited at low altitude was beautiful VFR at 7000.

  14. Bill Berson says:

    I tested the over-banking tendency of my RC model (high wing trainer) and did not notice any over-banking tendency. A friend tested his 1/4 scale Cub and again no over-banking tendency either. But he said his full size J3 Cub definitely did have an over-banking tendency.
    I think it depends on the amount of dihedral and other design factors.
    The models have more dihedral than full size airplanes and this extra dihedral limits the overbanking tendency.

    So the lesson for me is that each airplane is different.
    Thanks Mac, for prodding me to read Stick an Rudder again, I try to reread the book once a year to help understand the physics and keep myself alive.
    Bill

  15. Max Ravazzolo says:

    Regarding the “overbanking” tendency, I am pretty much sure that it depends largely from the single design. I’m a glider pilot, which means I’m *very often* at high bank, and different gliders behave quite differentely. My older bird (AWS 20l) was actually pretty unstable between 30 and 45 degrees, and then as the Gs increased it would become very stable and keep quite nicely the bank. In this case that glider had quite flexible wings, which seemed to be happy only when really engaged.
    One of the tests for the commercial glider license is doing 720 degrees turns with at least 45 degrees bank, without ever losing the “ball” (in our case, the wool yarn) and without accelerating or decelerating more than 5 miles from the entry speed along the whole two turns. I would really suggest this exercise to everybody, its really very instructive…

  16. Gordon Arnaut says:

    Good article, Mac…

    Not sure what the requirements are stateside but here in Canada students are given some basic training in the spiral dive…exercise 14 in the Transport Canada flight manual…

    A high wing trainer will usually spin into a spiral dive after about the first turn…so it is important to recognize the increasing airspeed, wing loading and higher g-force as the plane enters the spiral…the training is quite basic and is really just steep descending turns…although some instructors will let the plane enter a spiral by itself coming out of a spin…

    Also worth noting that Peter Garrison has a good article explaining the aerodynamics of the overbanking tendency in this month’s Flying…the reason is the difference in lift between the inner and outer wing in a turn…which, in turn, is caused by the outer wing have a greater airspeed, owing to the larger diameter of its turn…

    The difference is not great…with a maximum of about 2 percent greater airspeed on the outer wing…but since lift increases with the square of speed we get 4 percent more lift on the outer wing and correspondingly less on the inner wing…

    The result is a rolling moment of significant force that wants to increase the bank angle…Peter’s math shows this moment to be over 2,000 lb for the 80 degree turn and 700 lb for a 60 degree turn on a Cherokee-type airplane of about 2,500 lb weight…

    So the greater the bank angle, the stronger the overbanking tendency becomes…even though the difference in distance between the center of the turn and the respective wing halves decreases as bank angle increases, the speed difference between the respective wing halves increases due to the fact that the radius decreases even more…

    The reason the bank will steepen as you pull back elevator is because of the increase in angle of attack…so the outside wing makes even more lift and the rolling moment increases…so yes pulling back on the stick when the airplane is already in a steep bank will put the plane into a spiral dive…

    That is why it is important to recognize the sensory cues from increasing speed and wing loading as the plane accelerates in the dive…

    Dihedral does not affect the overbanking tendency…the purpose of dihedral is to stabilize the spiral mode, which means a tendency to return the wing to level after a disturbance…dihedral does this because of the presence of sideslip toward the inside of the bank…which results in the inner wing having a greater AOA and the outer wing less…hence the inner wing gets more lift and the plane rolls back opposite the bank…

    But the vertical tail (and especially rudder application by the pilot) will counteract a sideslip so dihedral will not produce a rolling moment if there is no sideslip…

    In a coordinated turn we have no sideslip so dihedral will not provide a rolling moment to counter the overbanking tendency…

  17. Gordon Arnaut says:

    Should also add that the corrective rolling moment from dihedral effect is much smaller in magnitude than the rolling moment due to the over-banking tendency…so once you get past a certain bank angle dihedral effect will have no effect…

    That is why dihedral effect only works at moderate bank angles…and only if there is sideslip…

    Dihedral also works if there is a yaw disturbance that points the nose off the airplane’s track…basically a “flat” sideslip…the inside wing seeing a higher AOA due to the dihedral…so if a gust from starboard blows your nose left, your left wing will see a higher AOA due to dihderal and a corrective roll to the right will result…

    This is also why we can pick up a wing with rudder, which is a certification requirement…

  18. Steve says:

    Great explanations. Thanks.

  19. MMA Strength says:

    MMA Training
    Marijuana vegetation is the true backyard gardeners aspiration.

Leave a Reply

Your email address will not be published. Required fields are marked *

*

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>