QUIT DOING THIS OR DIE!!! (MYTHS of aviation, some of which can kill you)

(Note: Most of these physics issues were made clear to me by Peter Garrison in various articles has published, but I joyfully take full credit for the inflammatory nature of my writing, and any references to actual events or the perceptions of the aviation community or your own perceptions. Peter only clarified the LAWS OF PHYSICS in these areas. I added all the stuff that will piss people off. Some contribution was also made by Flight Instructor Rob Coppock).

MYTH: I CAN FULLY DEFLECT THE CONTROLS BELOW MANEUVERING SPEED!

WRONG! BELIEVE THIS AND DIE!
The wing structure in light planes is usually certified to take +3.8 G's, -1.52 G's (plus a 50% safety factor). Put more load on the wing than that and you should consider yourself dead.
But here is the nice part: Below a certain speed, the wing simply cannot put out a full 3.8 G's of lift! It will STALL first! This speed is called "Maneuvering Speed". "Maneuvering Speed" is defined as the maximum speed the plane can be moving and still STALL before the WING BREAKS no matter how much you pull back on the stick.
If you are going slower than this and you pull all the way back on the stick, the wing will STALL WITHOUT PHYSICALLY BREAKING. If you are going faster than this and you pull all the way back on the stick, the wing can put out so much lift that it can be expected to break. So, as a result of the info above, people think they can deflect the stick as much as they like below maneuvering speed and stay alive. WRONG! The maneuvering speed is based on pulling BACK on the stick, NOT PUSHING FORWARDS!
Note what I said above: The "Maneuvering Speed" is defined as how fast you can go and not be able to put out more than 3.8 G's of lift... but the while the plane is certified for POSITIVE 3.8 G's, it is only certified for a NEGATIVE G-load of 1.52 G's!!!!! In other words, you can fail the wing in the NEGATIVE direction by pushing FORWARDS on the stick well BELOW the maneuvering speed!!!
Nobody knew this. They just think they can fully-deflect the stick below Maneuvering Speed and live but THAT IS ONLY TRUE FOR PULLING THE STICK BACK AND BEING GUARANTEED 3.8 G's OF POSITIVE G-LOAD STRUCTURE, NOT PUSHING FORWARDS, WHERE THE WING CAN FAIL AT A MEASLY 1.52 G's!
Also, for airliners, certification requirements require that the rudder can be fully-deflected below maneuvering speed, BUT ONLY IF THE PLANE IS NOT IN A SIDESLIP OF ANY SORT! WHAT A LOAD CRAP! In a wonderfully-timed accident shortly after Sept 11 2001 that everybody thought might be terrorism, an Airbus pilot stomped the rudder in wake turbulence while the plane was in a considerable sideslip. The COMBINED loads of the sideslip and rudder deflection took the vertical stab to its critical load! A very simple numerical analysis based on the black box confirms this. The airplane lost its vertical stab in flight and you know the rest.
Also, if you are at your maximum allowable G-limit (say 3.8) and you put in some AILERON CONTROL, you are actually asking for MORE LIFT FROM ONE WING THAN THE ALLOWABLE LIMIT! SO COMBINED ELEVATOR AND AILERON CAN BREAK THE PLANE, EVEN IF THE ELEVATOR IS POSITIVE-ONLY!
SO, WHEN YOU THINK THAT YOU CAN DO AS YOU PLEASE WITH THE CONTROLS BELOW MANEUVERING SPEED, YOU ARE WRONG!!!!! You instructor was wrong. The flight training manual was wrong. Your examiner was wrong. The FAA was wrong. I am right. Heed me. (and also look at a V-N diagram and the aircraft certification limits to prove it to yourself).

MYTH: I CAN ALWAYS GO TO 1 KT BELOW VNE IN SMOOTH AIR!

WRONG! BELIEVE THIS AND DIE IN SOME HOME-BUILTS!
Vne is 'Velocity Never-Exceed'. It is the fastest you can go without breaking stuff, as indicated on the airspeed indictor. Let's say that Vne for your airplane is 200 knots. That means that at sea-level, you better stay below 200 knots or the air pressure can pull the plane apart. Now, let's say you go to 20,000 feet and (with a turbocharger, pushing the nose down, or just having a huge engine) you manage to get the airplane up to 200 knots indicated airspeed. The airplane is ACTUALLY going about 275 knots. This is because the air is thinner, so it does not push against the wings as hard, and it does not push against the pitot-tube as hard. Because the air is thinner, you are really going 275 knots, even though you are only seeing 200 knots on the airspeed indicator due to the thinner air and resultant lower pressure on the airplane. Now, most pilots will read the sentence above, already know what I just said, and think that they must be OK going 200 knots indicated at 20,000 feet, since they are still below Vne. Possibly WRONG!!! The airplane may be over it's maximum FLUTTER SPEED. The FLUTTER speed is the speed above which the structure of the airplane will oscillate and then disintegrate. The flutter speed is NOT an INDICATED airspeed. It is a TRUE airspeed. In other words, if the flutter speed of the airplane is 200 knots at sea level, then it is 200 knots at 20,000 feet as well... which is only 145 knots ON THE AIRSPEED INDICATOR! In other words, your REAL Vne will come DOWN from 200 knots at sea level to 145 knots indictaed at 20,000 feet IF the speed-limit on the airframe is dictated by FLUTTER (which is a constant TRUE airspeed) vs pressure loads (which are a constant INDICATED airspeed). In other words, if your airplane has it's Vne determined by flutter, not pressure loads, then you need to never exceed that TRUE airspeed, which means that you need to go to a LOWER INDICATED airspeed as you climb to keep from exceeding that TRUE airspeed. So, at high altitudes, be ware! Just because the air is thinner does not always mean that you can push higher speeds... the FLUTTER speed does not increase as you climb, yet your TRUE speed does... at some point, if those speeds converge, then your next convergence will be with the Earth... in whatever pieces are left of your airplane!

MYTH: AT POSITIVE ANGLE OF ATTACK, THE DESCENDING PROP BLADE IS AT A HIGHER ANGLE OF ATTACK, SO IT PUTS OUT MORE LIFT, PULLING THE PLANE LEFT.

NOT THE WHOLE PICTURE!!! You only THINK this because you stand on the ramp beside your airplane on the ground, looking at the prop hub, imagining the nose pointing up and therefore the right-hand blade seeming to take a greater "bite" out of the air. Here is where your visualization is WRONG: If the nose is pointed up with respect to the air stream, then that right-hand prop blade is actually NOT DESCENDING STRAIGHT DOWN LIKE YOU ARE VISUALIZING, BUT IS INSTEAD MOVING FORWARDS A BIT AS IT DESCENDS, SO THE ANGLE OF ATTACK IS NOT INCREASED LIKE YOU THINK ON THE DESCENDING BLADE!! So why DOES the plane pull left in a climb even though the descending blade is NOT at a higher angle of attack? Look to helicopters for the answer. Their ADVANCING blade (the main rotor blade that is coming FORWARD) wants to put out a LOT more lift since it is moving at its rotational speed PLUS the speed of the aircraft. The RETREATING rotor is traveling a lot SLOWER!! It is traveling at its rotation speed MINUS the speed of the craft. So there tries to be a lot more lift on the right side of the rotor system, and the pilot has to enter a lot of correction in blade pitch to fly straight! A climbing airplane is the same: The DESCENDING blade is actually ADVANCING INTO THE AIR A LITTLE BIT (THUS MOVING FASTER) SINCE THE PLANE IS TILTED UP! The CLIMBING blade is retreating away from the onrushing air a bit for the same reason! Thus, the DESCENDING blade puts out more lift from its HIGHER SPEED when the airplane is at high angle of attack.
I have to admit that it will not kill you not to know this (;-)) but the aviation MYTH says otherwise so I want to correct it... also the angle of attack does change a bit as well since the air is not rushing head-on into the prop but instead coming up from underneath a bit, but it is the "advancing/retreating" speed change that you do not know about.

MYTH: I MIGHT STALL IF I TURN DOWNWIND!

WRONG! The myth is that if you are flying into a headwind (of say 20 knots, and you are indicating 100 knots airspeed, thus covering ground at 80 knots) then if you turn 180 degrees, the headwind will become a tailwind and you will find yourself with only 60 knots of indicated airspeed after the turn! (80 knots groundspeed with a 20 knot tailwinds leaves you with only 60 knots) WRONG!! MYTH! Of course you have a headwind before the turn, and a tailwind after, but this has no aerodynamic impact on your whatsoever. You can forget about the ground when doing (non ground-effect) aerodynamics. It means nothing. It is nothing but dirt underneath you that is not touching you, and that you tend to use as a reference since most places you go are conveniently located on it. You might as well use the moon as your reference, or the sun, or maybe the center of the Milky Way Galaxy. These are nothing but reference points, and have no impact on the nature of the flying machine. The aircraft is borne by the wind, and reference to GROUND SPEED has no impact at all on aerodynamics.
So, you might be saying: Wait a minute! If you have 100 knots of airspeed for the whole turn, then you must have come into the turn with 80 knots of ground speed, and come out of it with 120 knots of ground speed! You just got 40 knots of speed for free! IMPOSSIBLE!
No, you did NOT get 40 knots of speed for free. You simply aimed your plane in a different direction where its true reference-system (the moving air) HAPPENS to be going in the same direction as the reference-system you keep using (the ground). Just think of the air as being still and the earth moving underneath it at 20 mph. Now imagine the airplane making a 180-degree turn through the nonmoving air. Nothing special, right? But your speed over the EARTH was different before and after the turn, because of the movement of the EARTH happening to be in the direction as the plane or not. Now you should see that the downwind turn has no impact on speed at all since you are moving with the AIR. The Earth can rotate underneath you however it likes... it makes no difference to you. You only THINK it does because the millions of years of evolution that caused our brains to turn out the way they did has us thinking about things in reference to the GROUND because that is how we evolved to move: With our LEGS over the GROUND. It is not natural for you to quit thinking about the EARTH reference and use the AIR as a reference instead, so we (sometimes) INCORRECTLY think of the ground as a reference... even when flying!

Someone emailed me in response to this, respectfully pointing out that if flying North into a 20 kt headwind and then turning to the South, it still seems dangerous to him since how could the airplane pick up that extra 20 knots in the downwind turn to the South to hold his precious airspeed? The answer: IT DID NOT HAVE TO PICK UP 20 KNOTS OF SOUTHERLY SPEED AS IT TURNED... THAT 20 KNOTS OF SOUTHERLY SPEED WAS THERE BEFORE THE TURN EVEN BEGAN, IN THE FORM OF A 20-KNOT LOWER GROUNDSPEED AS HE FLEW NORTH! Again, it is nothing but a change in your reference system.

MYTH: THE OPERATING HANDBOOK TELLS ME WHAT THE PLANE CAN DO!

WRONG! The Pilots Operating Handbook is based on a factory test-pilot tweaking a brand new plane in perfect condition to its absolute limits. You are flying a beat-up 20-year-old airplane that no longer makes rated power and no longer has the original airfoil shapes with its various dents and wrinkles and you have bugs all over the leading edge of the wings while the factory pilot did not. Now you may be thinking that you are as good as any factory test pilot and your engine is fine and that dead bugs make no difference but in fact you often have not practiced the same maneuver over and over in exactly the same conditions until you have squeezed every foot out of the takeoff or landing distance at a given altitude, temperature, and weight, like the test pilot did.

=>You are just arriving somewhere with passengers with 20 other things on your mind and are trying to stay in one piece. That is ENTIRELY DIFFERENT from a test-pilot flying the same routine over and over with sandbags in the plane imitating passengers, with nothing else to do but squeeze every foot of distance out of the plane.

=>The power reduction from your weaker old engine is significant (we all know that out of a fleet of rented Cessna 172's, they all fly differently and have different performance).

=>As far as the dead bugs go, SIMPLY GETTING WET is enough to increase the drag on some airfoils by 50%.

When there is so much variability among airplanes, and test-pilots having nothing else on their minds but to optimize their flight technique while they practice the same maneuver 50 times in the same plane in identical conditions, you would be a fool to think that the Pilots Operating Handbook will actually tell you what your plane can do. There are plenty of cases to document this, but I was once landing a Cessna 172 at high altitude on a windy day with 4 people on board and when the wind proved too strong to land and I tried to go around the plane could barely manage it... it was all I could do to wallow along at minimum controllable airspeed, full flaps, barely able to stay in the air in level flight. This is not by any book. Another person tells me of a Cessna 152 that took OVER TWICE the distance to take off one day because the grass on his field was DAMP and a little LONG and he took off in the other direction from normal with the slightest upslope. Bottom line: Do NOT base your aircraft performance on the POH except to say "OK, this is the limit that I will never be able to break, but I might get about 75% of this performance if I fly the plane right".

austin

PS: For those of you that will email me saying: "Austin, that is great you are shedding some light on this, but you don't have to be so acerbic", here is my reply:
"You are right, I don't have to be so acerbic, but I am feeling grumpy now so I am getting a perverted pleasure from being acerbic anyway".

NOTE: SINCE I HAVE POSTED THIS EMAIL, I HAVE GOTTEN A NUMBER OF REPLIES FROM PEOPLE, AND I HAVE BEEN JOYOUSLY SURPRISED AND ENCOURAGED BY EVERY ONE OF THEM! EVERY SINGLE PERSON ALREADY KNEW ABOUT THESE THINGS, OR WAS HAPPY TO REPORT THAT THEY ARE GLAD TO HAVE BEEN EDUCATED... SOME PEOPLE EVEN SENT ME EMAILS CORRECTING SOME ERRORS THAT I MADE!!!! (WHICH HAVE SINCE BEEN CORRECTED IN THE DRAFT YOU SEE ABOVE) THUS EDUCATING ME FURTHER!!! EXCELLENT!! EXCELLENT!! EXCELLENT!!