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UPRT 13: The Flight Envelope
UPRT 13: The Flight Envelope
Published: 2016/09/03
Channel: WingPro
The Flight Envelope
The Flight Envelope
Published: 2015/10/08
Channel: Diegogol7
FSX A320 Flight Envelope Protection
FSX A320 Flight Envelope Protection
Published: 2013/11/08
Channel: Fangzahn Aviation Studios
V-G diagram. Flying envelope
V-G diagram. Flying envelope
Published: 2016/09/24
Channel: Douglas Bournigal
Aircraft Flight Envelope Vn Diagram Introduction
Aircraft Flight Envelope Vn Diagram Introduction
Published: 2017/06/16
Channel: Tamarack Aerospace Group
FSLabs A320-X Basics: Normal Law Flight Envelope Protection
FSLabs A320-X Basics: Normal Law Flight Envelope Protection
Published: 2017/01/10
Channel: Blackbox711
Shaft 400 Flight Envelope
Shaft 400 Flight Envelope
Published: 2009/09/25
Channel: Atlantahobby
1 21 Introduction to Aerospace Engineering I  21 Flight mechanics lectues 5 Flight envelope & practi
1 21 Introduction to Aerospace Engineering I 21 Flight mechanics lectues 5 Flight envelope & practi
Published: 2014/06/10
Channel: tawkaw OpenCourseWare
Velocity-RC Mirage - Exploring the Flight Envelope.
Velocity-RC Mirage - Exploring the Flight Envelope.
Published: 2011/05/11
Channel: Brian's R/C Corner
[Thingkung Machine] Flight Envelope -  Basic Course Aerospace Engineering - Lesson 21/21
[Thingkung Machine] Flight Envelope - Basic Course Aerospace Engineering - Lesson 21/21
Published: 2017/08/22
Channel: Thinking Machine
Flight Envelope -  Basic Course Aerospace Engineering - Lesson 21/21
Flight Envelope - Basic Course Aerospace Engineering - Lesson 21/21
Published: 2017/05/30
Channel: The King
Manned multicopter Episode 11  Expanding the flight envelope -Yaw
Manned multicopter Episode 11 Expanding the flight envelope -Yaw
Published: 2016/07/19
Channel: amazingdiyprojects
Flight Envelope -  Basic Course Aerospace Engineering - Lesson 21/21
Flight Envelope - Basic Course Aerospace Engineering - Lesson 21/21
Published: 2017/07/05
Channel: Snow Star
Aircraft Flight Envelope Gust & Maneuver in the  Vn Diagram
Aircraft Flight Envelope Gust & Maneuver in the Vn Diagram
Published: 2017/06/22
Channel: Tamarack Aerospace Group
Pushing the Envelope of Hypersonic Flight
Pushing the Envelope of Hypersonic Flight
Published: 2016/11/15
Channel: Smithsonian National Air and Space Museum
Documentary TV- Flight Envelope -  Basic Course Aerospace Engineering - Lesson 21/21
Documentary TV- Flight Envelope - Basic Course Aerospace Engineering - Lesson 21/21
Published: 2017/09/02
Channel: Documentary TV
SAFE™ Technology: Flight Envelope Protection
SAFE™ Technology: Flight Envelope Protection
Published: 2013/05/29
Channel: flysaferc
68 thrust vector tail sitter, extra power, flight envelope
68 thrust vector tail sitter, extra power, flight envelope
Published: 2017/04/12
Channel: research air
Flight Envelope -  Basic Course Aerospace Engineering - Lesson 21/21
Flight Envelope - Basic Course Aerospace Engineering - Lesson 21/21
Published: 2017/07/13
Channel: ✱ Hight light
Flight Three: Pushing the Envelope
Flight Three: Pushing the Envelope
Published: 2016/04/03
Channel: Blue Origin
Flight Envelope -  Basic Course Aerospace Engineering - Lesson 2121- Documentary 2017
Flight Envelope - Basic Course Aerospace Engineering - Lesson 2121- Documentary 2017
Published: 2017/05/28
Channel: Top Documentary HD
Prime Jet8 flight envelope
Prime Jet8 flight envelope
Published: 2010/09/02
Channel: kronikpilot
Flight Envelope -  Basic Course Aerospace Engineering - Lesson 21/21
Flight Envelope - Basic Course Aerospace Engineering - Lesson 21/21
Published: 2017/06/01
Channel: Rudy Jimenez
RCDOX 2012 FA 18 EXCEED Learning flight envelope RC plane
RCDOX 2012 FA 18 EXCEED Learning flight envelope RC plane
Published: 2013/07/04
Channel: rcdox
Hayabusa flight envelope.
Hayabusa flight envelope.
Published: 2011/05/09
Channel: kronikpilot
[Fusion Power] Flight Envelope -  Basic Course Aerospace Engineering - Lesson 21/21
[Fusion Power] Flight Envelope - Basic Course Aerospace Engineering - Lesson 21/21
Published: 2017/08/23
Channel: Fusion Power
Habu32 flight envelope
Habu32 flight envelope
Published: 2012/12/23
Channel: mjnco1
H32 flight envelope
H32 flight envelope
Published: 2012/12/22
Channel: mjnco1
Two Motor Armin Wing FPV Plane Testing (pushing) the Flight Envelope #3
Two Motor Armin Wing FPV Plane Testing (pushing) the Flight Envelope #3
Published: 2012/09/26
Channel: goodkebo
Victor flies the Hanger 9 F22 past it
Victor flies the Hanger 9 F22 past it's Vne flight envelope
Published: 2010/09/13
Channel: Eric Jaakkola
Flight Envelope -  Basic Course Aerospace Engineering - Lesson 21/21
Flight Envelope - Basic Course Aerospace Engineering - Lesson 21/21
Published: 2017/08/20
Channel: Documentary Network
Mini TD close flight envelope!
Mini TD close flight envelope!
Published: 2011/04/03
Channel: kronikpilot
Vampire HK ChangeSun flight envelope on 3s
Vampire HK ChangeSun flight envelope on 3s
Published: 2012/05/11
Channel: mopetista
RcPowers X-31 Redonkulous flight envelope.
RcPowers X-31 Redonkulous flight envelope.
Published: 2009/12/31
Channel: kronikpilot
Solar Impulse -  Flight Envelope Test
Solar Impulse - Flight Envelope Test
Published: 2009/03/20
Channel: SOLAR IMPULSE
Flight Envelope Basic Course Aerospace Engineering Lesson 21/21
Flight Envelope Basic Course Aerospace Engineering Lesson 21/21
Published: 2017/06/23
Channel: Marco George
Blade 350QX with AP Mode. Exploring the flight envelope
Blade 350QX with AP Mode. Exploring the flight envelope
Published: 2014/05/09
Channel: Randall Huston
Airbus A320 flight controls protections - Baltic Aviation Academy
Airbus A320 flight controls protections - Baltic Aviation Academy
Published: 2013/11/08
Channel: BAA Training
Expanding the Flight Envelope Innovative Aeronautical Technology Developed at Dryden Flight Research
Expanding the Flight Envelope Innovative Aeronautical Technology Developed at Dryden Flight Research
Published: 2016/07/14
Channel: Serena L.
Dan
Dan's VTOL Ver. 5 - Exploring the Flight Envelope
Published: 2015/11/15
Channel: 3dfoamies
(DCS) Straight Out of Flight Envelope
(DCS) Straight Out of Flight Envelope
Published: 2016/11/22
Channel: KrazySwede
Flight Envelope - Basic Course Aerospace Engineering - Lesson 21/21
Flight Envelope - Basic Course Aerospace Engineering - Lesson 21/21
Published: 2017/05/30
Channel: Bob Thomas
Pushing the Flight Envelope The X Vehicle Program
Pushing the Flight Envelope The X Vehicle Program
Published: 2016/03/03
Channel: Lawrence
Establishing the X650 Quad Flight Envelope
Establishing the X650 Quad Flight Envelope
Published: 2012/02/25
Channel: Whisperjet123
Documentary on Flight Envelope || Cruise Missile||  Climate as an Emerging 1990 by Carl Sagan
Documentary on Flight Envelope || Cruise Missile|| Climate as an Emerging 1990 by Carl Sagan
Published: 2017/08/16
Channel: PRS Entertainment
Flight Envelope |  Basic Course Aerospace Engineering | Lesson 21/21
Flight Envelope | Basic Course Aerospace Engineering | Lesson 21/21
Published: 2017/05/11
Channel: Toi Doi
Maverick-Models Delro Raven V1 - "Exploring the flight envelope" [Extreme 3D]
Maverick-Models Delro Raven V1 - "Exploring the flight envelope" [Extreme 3D]
Published: 2013/09/22
Channel: Maverick - Models
Pushing the Flight Envelope The X Vehicle Program
Pushing the Flight Envelope The X Vehicle Program
Published: 2016/03/19
Channel: Wanda. A
Super Alula 1.4 flight envelope testing part. 1
Super Alula 1.4 flight envelope testing part. 1
Published: 2014/10/18
Channel: javor36
Testing of the F-35A Lightning at Edge of the Flight Envelope in Military Hub
Testing of the F-35A Lightning at Edge of the Flight Envelope in Military Hub
Published: 2015/07/16
Channel: Wars in the World
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WIKIPEDIA ARTICLE

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Flight envelope diagram.

In aerodynamics, the flight envelope, service envelope, or performance envelope of an aircraft refers to the capabilities of a design in terms of airspeed and load factor or altitude.[1][2] The term is somewhat loosely applied, and can also refer to other measurements such as maneuverability. When a plane is pushed, for instance by diving it at high speeds, it is said to be flown "outside the envelope", something considered rather dangerous.

Flight envelope is one of a number of related terms that are all used in a similar fashion. It is perhaps the most common term because it is the oldest, first being used in the early days of test flying. It is closely related to more modern terms known as extra power and a doghouse plot which are different ways of describing a flight envelope. In addition, the term has been widened in scope outside the field of engineering, to refer to the strict limits in which an event will take place or more generally to the predictable behavior of a given phenomenon or situation, and hence, its "flight envelope" .


Extra power[edit]

Extra power, or specific excess power,[3] is a very basic method of determining an aircraft's flight envelope. It is easily calculated, but as a downside does not tell very much about the actual performance of the aircraft at different altitudes.

Choosing any particular set of parameters will generate the needed power for a particular aircraft for those conditions. For instance a Cessna 150 at 2,500 ft (800 m) altitude and 90 mph (140 km/h) speed needs about 60 hp (45 kW) to fly straight and level. The C150 is normally equipped with a 100 hp (75 kW) engine, so in this particular case the plane has 40 hp (30 kW) of extra power. In overall terms this is very little extra power, 60% of the engine's output is already used up just keeping the plane in the air. The leftover 40 hp (30 kW) is all that the aircraft has to maneuver with, meaning it can climb, turn, or speed up only a small amount. To put this in perspective, the C150 could not maintain a 2g (20 m/s²) turn, which would require 120 hp (or somewhat more) under the same conditions.

For the same conditions a fighter aircraft might require considerably more power due to their wings being inefficient at low speeds, for argument's sake it might require 10,000 hp (7.5 MW). However modern jet engines can provide considerable power, the equivalent of 50,000 hp (37 MW) typically. With this amount of extra power the aircraft can achieve very high maximum rate of climb, even climb straight up, make powerful continual maneuvers, or fly at very high speeds.

Doghouse plot[edit]

Altitude envelope
Turn rate envelope

A doghouse plot generally shows the relation between speed at level flight and altitude, although other variables are also possible. It takes more effort to make than an extra power calculation, but in turn provides much more information such as ideal flight altitude. The plot typically looks something like an upside-down U and is commonly referred to as a doghouse plot due to its resemblance to a doghouse. The diagram on the right shows a very simplified plot which shall be used to explain the general shape of the plot.

The outer edges of the diagram, the envelope, show the possible conditions that the aircraft can reach in straight and level flight. For instance, the aircraft described by the black altitude envelope on the right can fly at altitudes up to about 52,000 feet, at which point the thinner air means it can no longer climb. The aircraft can also fly at up to Mach 1.1 at sea level, but no faster. This outer surface of the curve represents the zero-extra-power condition. All of the area under the curve represents conditions that the plane can fly at with power to spare, for instance, this aircraft can fly at Mach 0.5 at 30,000 feet while using less than full power.

In the case of high-performance aircraft, including fighters, this "1-g" line showing straight-and-level flight is augmented with additional lines showing the maximum performance at various g loadings. In the diagram at right, the green line represents, 2-g, the blue line 3-g, and so on. The F-16 Fighting Falcon has a very small area just below Mach 1 and close to sea level where it can maintain a 9-g turn.

Flying outside the envelope is possible, since it represents the straight-and-level condition only. For instance diving the aircraft allows higher speeds, using gravity as a source of additional power. Likewise higher altitude can be reached by first speeding up and then going ballistic, a maneuver known as a zoom climb.


Stalling speed[edit]

All fixed-wing aircraft have a minimum speed at which they can maintain level flight, the stall speed (left limit line in the diagram). As the aircraft gains altitude the stall speed increases; since the wing is not growing any larger the only way to support the aircraft's weight with less air is to increase speed. While the exact numbers will vary widely from aircraft to aircraft, the nature of this relationship is typically the same; plotted on a graph of speed (x-axis) vs. altitude (y-axis) it forms a diagonal line.


Service ceiling[edit]

Inefficiencies in the wings also make this line "tilt over" with increased altitude, until it becomes horizontal and no additional speed will result in increased altitude. This maximum altitude is known as the service ceiling (top limit line in the diagram), and is often quoted for aircraft performance. The area where the altitude for a given speed can no longer be increased at level flight is known as zero rate of climb and is caused by the lift of the aircraft getting smaller at higher altitudes, until it no longer exceeds gravity.


Top speed[edit]

The right side of the graph represents the maximum speed of the aircraft. This is typically sloped in the same manner as the stall line due to air resistance getting lower at higher altitudes, up to the point where an increase in altitude no longer increases the maximum speed due to lack of oxygen to feed the engines.

The power needed varies almost linearly with altitude, but the nature of drag means that it varies with the square of speed—in other words it is typically easier to go higher than faster, up to the altitude where lack of oxygen for the engines starts to play a significant role.

Velocity vs. load factor chart[edit]

A V-n diagram showing VS (stall speed at 1G), VC (corner/maneuver speed) and VD (dive speed)

A chart of velocity versus load factor (or V-n diagram) is another way of showing limits of aircraft performance. It shows how much load factor can be safely achieved at different airspeeds.[3]

At higher temperatures, air is less dense and planes must fly faster to generate the same amount of lift. High heat may reduce the amount of cargo a plane can carry, increase the length of runway a plane needs to take off, and make it more difficult to avoid obstacles such as mountains. In unusual weather conditions this may make it unsafe or uneconomical to fly, occasionally resulting in the cancellation of commercial flights.[4][5]

Sidenotes[edit]

Although it is easy to compare aircraft on simple numbers such as maximum speed or service ceiling, an examination of the flight envelope will reveal far more information. Generally a design with a larger area under the curve will have better all-around performance. This is because when the plane is not flying at the edges of the envelope, its extra power will be greater, and that means more power for things like climbing or maneuvering. General aviation aircraft have very small flight envelopes, with speeds ranging from perhaps 50 to 200 mph, whereas the extra power available to modern fighter aircraft result in huge flight envelopes with many times the area. As a tradeoff however, military aircraft often have a higher stalling speed. As a result of this the landing speed is also higher.


"Pushing the envelope"[edit]

This phrase is used to refer to an aircraft being taken to, and perhaps beyond, its designated altitude and speed limits.[6] By extension, this phrase may be used to mean testing other limits, either within aerospace or in other fields e.g. Plus ultra (motto).[7]


See also[edit]


Notes[edit]

  1. ^ §23.333 Flight envelope
  2. ^ Flight envelope - diagram Archived June 1, 2010, at the Wayback Machine.
  3. ^ a b Sinclair, Edward J. "The Army Aviator's Handbook for Maneuvering Flight and Power Management". p. 25. United States Army Aviation Branch, 24 March 2005. Accessed: 6 January 2011.
  4. ^ Why planes can’t fly when it’s too hot, and other ways our civilization can’t take the heat
  5. ^ Why Planes Can't Fly In Extreme Heat
  6. ^ Quinion, Michael. Push the envelope World Wide Words. Accessed: 6 January 2011.
  7. ^ G.W. Poulos & Daniel Lindley. "What Is a Flight Envelope?" WiseGeek, 6 May 2014. Accessed: 16 May 2014.

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