I.R.PIRATE
27th Mar 2005, 11:57
I have come across a verly interesting article, debunking some of the myths pilots believe and operate under each day. It was written by a chap called Austin who is a guru on laminar research, in conjunction with aerodynamicist and physics professor Peter Garrison, and well known flight instructor Rob Coppock. Makes for an interesting read. Enjoy. I'll post one each day.
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 know 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 it's critical load! A very simple numerical analysis based on the black box confirms this. The airplane lost it's 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).
:ok:
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 know 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 it's critical load! A very simple numerical analysis based on the black box confirms this. The airplane lost it's 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).
:ok: