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Aircraft speed: Difference between revisions
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The '''Mach number''' (M) is the ratio of an aircraft's TAS over the local speed of sound. A Mach number below 1 means that the plane moves subsonically, a Mach number above 1 indicates supersonic flight. The Mach number is interesting because a number of phenomena take place just around Mach 1, for example a sudden increase in drag induced by shockwave generation. However, since the speed of sound changes with the compressibility (and hence temperature) of air, the Mach number is dependent on altitude (as the air temperature drops at higher altitudes). This implies that Mach 2 at sea level corresponds to a faster TAS than Mach 2 at 30.000 ft. The precise relations between TAS, Mach number and altitude are rather complicated formulae and depend in essence on the local weather pattern determining the pressure and temperature gradients in the atmosphere. | The '''Mach number''' (M) is the ratio of an aircraft's TAS over the local speed of sound. A Mach number below 1 means that the plane moves subsonically, a Mach number above 1 indicates supersonic flight. The Mach number is interesting because a number of phenomena take place just around Mach 1, for example a sudden increase in drag induced by shockwave generation. However, since the speed of sound changes with the compressibility (and hence temperature) of air, the Mach number is dependent on altitude (as the air temperature drops at higher altitudes). This implies that Mach 2 at sea level corresponds to a faster TAS than Mach 2 at 30.000 ft. The precise relations between TAS, Mach number and altitude are rather complicated formulae and depend in essence on the local weather pattern determining the pressure and temperature gradients in the atmosphere. | ||
==V speeds== | ==V speeds== | ||
For complete V speed "definitions" list please visit [http://en.wikipedia.org/wiki/V_speeds Wikipedia]. Here a small abstract. Note that V speed definitions can depend of local [[Flight rules]]. Most V speeds depend on the aircraft configuration (how much it weights). V speeds are used to compare aircraft performance and will be mentioned in the aircraft flight manual (AFM). | For complete V speed "definitions" list please visit [http://en.wikipedia.org/wiki/V_speeds Wikipedia]. Here a small abstract. Note that V speed definitions can depend of local [[Flight rules]]. Most V speeds depend on the aircraft configuration (how much it weights etc.) so must be calculated forehand and must be included in the flight-plan. V speeds are used to compare aircraft performance and will be mentioned in the aircraft flight manual (AFM). | ||
<!-- please add to this list when needed --> | <!-- please add to this list when needed --> | ||
{| | {| | ||
|- valign="top" | |- valign="top" | ||
|V<sub>1</sub> || | |V<sub>1</sub> || Take-off decision speed & Critical engine failure recognition speed. | ||
During take-off the speed at which the aircraft safely can take-off even when one of more | During take-off the speed at which the aircraft safely can take-off even when one (of more) engine fails ("eats a bird"). The co-pilot (FO) will call out V<sub>1</sub> during take-off. | ||
|- valign="top" | |- valign="top" | ||
|V<sub> | |V<sub>R</sub> ||Nose-wheel take off speed. | ||
The speed at which the | The speed at which the nose-wheel leaves (should leave) the ground. As the speed increases the yokes will be pulled at V<sub>r</sub>. It is also the speed at which the aircraft still can be stopped if there is a critical failure. The co-pilot (FO) will call out "rotate" during take off. V<sub>r</sub> is very similar to V<sub>rot</sub> and V<sub>ref</sub>. | ||
|- | |- | ||
|V<sub>3</sub> || Flap retraction speed. | |V<sub>3</sub> || Flap retraction speed. | ||
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|V<sub>NO</sub> || Maximum structural cruising speed or maximum speed for normal operations. | |V<sub>NO</sub> || Maximum structural cruising speed or maximum speed for normal operations. | ||
|} | |} | ||
*Not knowing the (complete list of) V speeds has caused dramatic accidents. It has occurred that the pilot and co-pilot were not aware of the minimal speed of an aircraft during landing with one engine off causing loss of control just before touch-down. | |||
==Pitot tube== | ==Pitot tube== | ||