digplanet beta 1: Athena
Share digplanet:

Agriculture

Applied sciences

Arts

Belief

Chronology

Culture

Education

Environment

Geography

Health

History

Humanities

Language

Law

Life

Mathematics

Nature

People

Politics

Science

Society

Technology

Pitching moment changes pitch angle
A graph showing coefficient of pitching moment with respect to angle of attack. The negative slope for positive α indicates stability in pitching.

In aerodynamics, the pitching moment on an airfoil is the moment (or torque) produced by the aerodynamic force on the airfoil if that aerodynamic force is considered to be applied, not at the center of pressure, but at the aerodynamic center of the airfoil. The pitching moment on the wing of an airplane is part of the total moment that must be balanced using the lift on the horizontal stabilizer.[1] More generally, a pitching moment is any moment acting on the pitch axis of a moving body.

The lift on an airfoil is a distributed force that can be said to act at a point called the center of pressure. However, as angle of attack changes on a cambered airfoil, there is movement of the center of pressure forward and aft. This makes analysis difficult when attempting to use the concept of the center of pressure. One of the remarkable properties of a cambered airfoil is that, even though the center of pressure moves forward and aft, if the lift is imagined to act at a point called the aerodynamic center the moment of the lift force changes in proportion to the square of the airspeed. If the moment is divided by the dynamic pressure, the area and chord of the airfoil, to compute a pitching moment coefficient, this coefficient changes only a little over the operating range of angle of attack of the airfoil. The combination of the two concepts of aerodynamic center and pitching moment coefficient make it relatively simple to analyse some of the flight characteristics of an aircraft.[2]

## Measurement

The aerodynamic center of an airfoil is usually close to 25% of the chord behind the leading edge of the airfoil. When making tests on a model airfoil, such as in a wind-tunnel, if the force sensor is not aligned with the quarter-chord of the airfoil, but offset by a distance x, the pitching moment about the quarter-chord point, $M_{c/4}$ is given by

$M_{c/4} = M_\text{indicated} + \mathbf{x}\times (D_\text{indicated}, L_\text{indicated})$

where the indicated values of D and L are the drag and lift on the model, as measured by the force sensor.

## Coefficient

The pitching moment coefficient is important in the study of the longitudinal static stability of aircraft and missiles.

The pitching moment coefficient $C_m$ is defined as follows[3]

$C_m=\frac{M}{qSc}$

where M is the pitching moment, q is the dynamic pressure, S is the wing area, and c is the length of the chord of the airfoil. $C_m$ is a dimensionless coefficient so consistent units must be used for M, q, S and c.

Pitching moment coefficient is fundamental to the definition of aerodynamic center of an airfoil. The aerodynamic center is defined to be the point on the chord line of the airfoil at which the pitching moment coefficient does not vary with angle of attack,[2] or at least does not vary significantly over the operating range of angle of attack of the airfoil.

In the case of a symmetric airfoil, the lift force acts through one point for all angles of attack, and the center of pressure does not move as it does in a cambered airfoil. Consequently the pitching moment coefficient for a symmetric airfoil is zero.

The pitching moment is, by convention, considered to be positive when it acts to pitch the airfoil in the nose-up direction. Conventional cambered airfoils supported at the aerodynamic center pitch nose-down so the pitching moment coefficient of these airfoils is negative.[4]

## References

• Clancy, L.J. (1975), Aerodynamics, Pitman Publishing Limited, London, ISBN 0-273-01120-0
• Piercy, N.A.V, Aerodynamics, pp384–386, English Universities Press. London (1943)
• Low-Speed Stability Retrieved on 2008-07-18

### Notes

1. ^ Clancy, L.J., Aerodynamics, Section 5.3
2. ^ a b Clancy, L.J., Aerodynamics, Section 5.10
3. ^ Clancy, L.J., Aerodynamics, Section 5.4
4. ^ Ira H. Abbott, and Albert E. Von Doenhoff (1959), Theory of Wing Sections, Dover Publications Inc., New York SBN 486-60586-8

Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Pitching_moment — Please support Wikipedia.
 190493 videos foundNext >
 Aerodynamics: Forces Acting on an Airfoil 1941 US Army Air Forces Training Film TF1-161more at http://scitech.quickfound.net/aviation_news_and_search.html "DEPICTS THE AERODYNAMIC THEORY AND PRINCIPLES OF FORCES ACTING ON ... Lift drag pitching momentLab video. Gyro Effect - Effect of Pitching Moment of Yawing MomentThe purpose of this experiment was to demonstrate the gyro effect, and the effect of pitch on yawing moment. It was constructed out of poplar wood for the frames ... #etfasa7: Pitching MomentMustafa was inroducing the idea of #etfasa7 in just a minute :) Coefficient of Moment for a Pitching AirfoilThe Time-Spectral method (a.k.a. Fourier collocation method) is used to compute the unsetady aerodynamics associated with a pitching airfoil in a freestream. XoptFoil airfoil optimization with pitching moment constraintXoptFoil uses the XFoil aerodynamics engine to optimize airfoils. You can get the code here: https://sourceforge.net/projects/xoptfoil/ This example shows the ... BAL@BOS: Davis earns win in first pitching appearance5/6/12: Infielder Chris Davis pitches two shutout innings and strikes out two in his first Major League outing to earn his first win Check out http://MLB.com/video ... The Last Pitch Of The Last 25 MLB World SeriesPLEASE READ*** I'm sorry for not including the 1995 WS that the Braves won and the 2005 WS that the White Sox won. I couldn't get those clips. I make all the ... Fans on Pitch ✪ Football (Soccer) Funny & Crazy MomentsGet Up to \$1000 Bonus. US Friendly Sportsbook http://goo.gl/7ohIeq Fans on Pitch. Funny and Crazy Football Moments. Felix UK compilation. Check out his ... Sharks Get Emotional During Pitch - Shark TankThis entrepreneur moved the Sharks when he explained what motivates him. Subscribe: http://goo.gl/mo7HqT Follow Shark Tank: ...
 190493 videos foundNext >
 67 news items
 FlightGear Space Shuttle Project FlightSim.com (press release) Thu, 28 Apr 2016 10:26:15 -0700 For a similar reason, at high Mach numbers the response to the craft to elevon movement is strongly asymmetric: Upward deflection causes much less pitching moment than downward deflection by the same angle. Only at lower airspeed and smaller AoA, the ... Houston Chronicle Jason Castro's insight proves valuable to fellow Astros catchers Houston Chronicle Fri, 18 Mar 2016 18:41:15 -0700 It was the Astros' signature pitching moment in a year defined by brilliant pitching. Mike Fiers completed his no-hitter, buckled in excitement, shot back up and tossed his glove high in the air. Then he took two steps toward the unsung hero, Jason Castro. The Register NASA charges up 18-prop electric X-plane The Register Tue, 09 Feb 2016 07:59:34 -0800 NASA explains that scientists "used the testbed to measure lift, drag, pitching moment and rolling moment that can validate research tools". The space agency adds: "Tests so far show the distribution of power among the 18 motors creates more than ... RT NASA tests experimental 18-propeller wing in step towards new electric aircraft RT Wed, 10 Feb 2016 16:22:30 -0800 “Researchers have used the testbed to measure lift, drag, pitching moment and rolling moment that can validate research tools,” Sean Clarke, Sceptor's co-principal investigator at NASA's Armstrong Flight Research Center in California, said in a statement. PilotWeb Flight Test: B&F FK9 ELA-SW PilotWeb Fri, 27 Nov 2015 06:45:46 -0800 As the flaps went down they produced a slight nose-down pitching moment that was easily trimmed out. However, care must be taken to avoid exceeding Vfe, which at only 62kt is somewhat on the low side. A great all rounder Photo: Jim Lawrence. Very ... Eureka passenger plane of the future Eureka Fri, 15 Jan 2016 07:00:00 -0800 This gives the aircraft a nose-up pitching moment. The aircraft's Mach number – the speed at which it travels, compared to the speed of sound – is also reduced from 0.72 to 0.80, giving it a gentler, more-effective low-sweep wing. Another feature of ... The Aviation Herald National Air Cargo B744 at Bagram on Apr 29th 2013, lost height shortly after ... The Aviation Herald Mon, 14 Sep 2015 07:48:45 -0700 1, 2, and 3) were assumed, a shift of the horizontal stabilizer from the set takeoff position to a 5° leading-edge-down position resulted in an inability of the available flight control surfaces to counter the resulting nose-up pitching moment. Study ... Racer MILLER: Barnum & Bailey spotted at IMS Racer Sun, 17 May 2015 20:24:13 -0700 Robin portrait It wasn't as big a circus as 1997, when every bit of integrity and competition got kicked to the curb so the Indy Racing League could avoid the public relations nightmare of not starting the fastest 33 qualifiers. But Sunday's sideshow ...
 Limit to books that you can completely read online Include partial books (book previews) .gsc-branding { display:block; }

Oops, we seem to be having trouble contacting Twitter