Editing Maximum takeoff weight

{{short description|Maximum weight of a craft at which takeoff is permitted}}
{{Use dmy dates|date=September 2021}}
[[File:Takeoff weight diagram.svg|thumb|upright=1.35|Takeoff weight components]]

The '''maximum takeoff weight''' ('''MTOW''') or '''maximum gross takeoff weight''' ('''MGTOW''') or '''maximum takeoff mass''' ('''MTOM''') of an [[aircraft]], also known as the '''maximum structural takeoff weight''' or '''maximum structural takeoff mass''',<ref name="JAR OPS">{{cite web |title=JAR-OPS 1.607 (d) |url=https://www.caa.gov.om/upload/files/regulations/civil-aviation-regulation/commercial-air-transportation-aeroplanes.pdf |access-date=28 October 2024}}</ref> is the maximum weight at which the pilot is allowed to attempt to [[takeoff|take off]], due to structural or other limits. The analogous term for rockets is '''gross lift-off mass''', or '''GLOW'''. MTOW is usually specified in units of kilograms or pounds.

MTOW is the heaviest weight at which the aircraft has been shown to meet all the [[airworthiness]] requirements applicable to it. It refers to the maximum permissible aircraft weight at the start of the takeoff run.<ref name="JAR OPS"/> MTOW of an aircraft is fixed and does not vary with altitude, air temperature, or the length of the runway to be used for takeoff or landing.

'''Maximum permissible takeoff weight''' or "regulated takeoff weight", varies according to flap setting, altitude, air temperature, length of runway and other factors. It is different from one takeoff to the next, but can never be higher than the MTOW.

==Certification standards==
Certification standards applicable to the airworthiness of an aircraft contain many requirements. Some of these requirements can only be met by specifying a maximum weight for the aircraft, and demonstrating that the aircraft can meet the requirement at all weights up to, and including, the specified maximum.  This limit is typically driven by structural requirements – to ensure the aircraft structure is capable of withstanding all the loads likely to be imposed on it during the takeoff,<ref>{{cite book | last=Torenbeek | first=E. | title=Synthesis of Subsonic Airplane Design: An introduction to the preliminary design of subsonic general aviation and transport aircraft, with emphasis on layout, aerodynamic design, propulsion and performance | publisher=Springer Netherlands | year=2013 | isbn=978-94-017-3202-4 | url=https://books.google.com/books?id=6nX7CAAAQBAJ&pg=PA272 | access-date=2023-10-22 | page=272}}</ref> and occasionally by the [[maximum flight weight]].<ref>{{cite book | last=Niu | first=C. | title=Airframe Structural Design: Practical Design Information and Data on Aircraft Structures | publisher=Conmilit Press | year=1988 | isbn=978-962-7128-04-5 | url=https://books.google.com/books?id=EHdGAAAAYAAJ&pg=PA585 | access-date=2023-10-22 | page=585 }}</ref>

==Multiple MTOW==
It is possible to have an aircraft certified with a reduced MTOW, lower than the structural maximum, to take advantage of lower MTOW-based fees, such as insurance premiums, landing fees and air traffic control fees are MTOW based.<ref name="CAA"/><ref>{{cite web |url=http://www.icao.int/publications/Documents/9082_cons_en.pdf|access-date=15 September 2013|title=ICAO's Policies on Charges for Airports and Air Navigation Services }}</ref> This is considered a permanent modification.<ref name="CAA"/>

Alternatively, holders of an Air Operator Certificate (AOC) may vary the Maximum Declared Take-Off Weight (MDTOW) for their aircraft. They can subscribe to a scheme, and then vary the weight for each aircraft without further charge.<ref name="FODCOM">{{cite web | url=https://publicapps.caa.co.uk/modalapplication.aspx?appid=11&mode=detail&id=3583 | title=Fodcom 20/09 }}</ref><ref name="CAA">{{cite web | url=https://www.caa.co.uk/commercial-industry/aircraft/operations/aircraft-insurance/ | title=Aircraft insurance &#124; Civil Aviation Authority }}</ref>

An aircraft can have its MTOW increased by reinforcement due to additional or stronger materials. For example, the [[Airbus A330]] 242 tonnes MTOW variant / [[Airbus A330neo|A330neo]] uses [[Aluminium alloy#Aluminium–scandium|Scandium–aluminium]] (scalmalloy) to avoid an [[Operating empty weight|empty weight]] increase.<ref>[http://www.flightglobal.com/news/articles/farnborough-airbus-outlines-a330neo-engineering-demands-401664/ FARNBOROUGH: Airbus outlines A330neo engineering demands]</ref><ref>[http://www.technology-licensing.com/etl/int/en/What-we-offer/Technologies-for-licensing/Metallics-and-related-manufacturing-technologies/Scalmalloy.html Scalmalloy aluminum-magnesium-scandium alloy] {{Webarchive|url=https://web.archive.org/web/20160815181052/http://www.technology-licensing.com/etl/int/en/What-we-offer/Technologies-for-licensing/Metallics-and-related-manufacturing-technologies/Scalmalloy.html |date=15 August 2016 }} Airbus Technology</ref><ref>[https://3dprint.com/220033/scalmalloy-aircraft-material/ Metal 3D Printing Material Scalmalloy Could be the Aircraft Material of the Future.  3DPrint.com,  Sarah Saunders. Jul 20, 2018.]</ref>

==Maximum permissible takeoff weight or maximum allowed takeoff weight==
In many circumstances an aircraft may not be permitted to take off at its MTOW. In these circumstances the maximum weight permitted for takeoff will be determined taking account of the following:
* [[Flap (aircraft)|Wing flap]] setting. See the [[Spanair Flight 5022]] crash
* Airfield altitude (height above sea-level) – This affects air pressure which affects maximum engine power or thrust. 
* Air temperature – This affects air density which affects maximum engine power or thrust.
* Length of runway – A short runway means the aircraft has less distance to accelerate to takeoff speed.  The length for computation of maximum permitted takeoff weight may be adjusted if the runway has clearways and/or stopways.
* Runway wind component – The best condition is a strong headwind straight along the runway.  The worst condition is a tailwind.  If there is a crosswind it is the wind component along the runway which must be taken into account.
* Condition of runway – The best runway for taking off is a dry, paved runway.  An unpaved runway or one with traces of snow will provide more rolling friction which will cause the airplane to accelerate more slowly. See the [[Munich air disaster]].
* Obstacles – An airplane must be able to take off and gain enough height to clear all obstacles and terrain beyond the end of the runway.

The maximum weight at which a takeoff may be attempted, taking into account the above factors, is called the maximum permissible takeoff weight, maximum allowed takeoff weight or regulated takeoff weight.

==Field Limited Weight==
{{See also|Balanced field takeoff}}

The '''Field Limited Weight''' is the lowest of the: 
*Take-Off Distance Limited Weight
*Engine-Out accelerate-stop distance limited weight
*Engine-Out Take-Off Distance Limited Weight

==Runway Limited Weight==
The '''Runway Limited Weight''' is the lowest of the: 
*Field Limited Weight
*VMCG limited weight
*Tyre speed limited weight
*Brake energy limited weight

==Regulated Take-Off Weight==
The '''Regulated Take-Off Weight''' is the lowest of the:
*Runway limited weight
*Obstacle limited weight
*Climb limited weight

==See also==
* [[International Civil Aviation Organization#Use of the International System of Units|ICAO recommendations on use of the International System of Units]]
* [[Aircraft gross weight]]
* [[List of airliners by maximum takeoff weight]]
* [[Maximum zero-fuel weight]]
* [[Operating empty weight]]
* [[Wake turbulence#Wake turbulence categories|Wake turbulence category]]

==References==
{{reflist}}

==External links==
*[http://www.caa.co.uk/default.aspx?catid=60&pagetype=90&pageid=822 CAA data terms definition]

[[Category:Aircraft weight measurements]]