Talk:Takeoff

Limited to fixed-wing aircraft?

This article only deals with fixed wing takeoffs. If it isn't limited in the tile it should cover all forms of flight including helicopters, birds,aircraft carrier takeoffs (steam catapult and skijump), V/STOL... balloons and carrier takeoffs are illustrated but not covered inthe text. Cyclopaedic 19:26, 28 April 2007 (UTC)

Rotation

When rotated, an aircraft will NOT "continue to rotate" unti it stalls. Rotation is typically applied until the nose is at a specified position. Mike Stramba 16:43, 1 Nov 2003 (UTC)

Also, rotation does not take place "about the aircraft's centre of gravity" - it rotates around the axles of its main wheels! Think about it. These are behind the centre of gravity (unless it's a taildragger), otherwise the plane would tip over on the ground. Once actually flying, then things are different, but rotation is something that occurs below flying speed. GRAHAMUK 11:31, 8 Nov 2003 (UTC)

Graham, hmm interesting thought about c.g. vs wheels. I don't have the technical answer, but I think I'll look into it. I disagree that it occurs "below flying speed". Ok, I guess you mean the speed neccessary to get the plane off the ground, but *some* speed is neccesary over the wings to generate enough force to get the plane to rotate. So since it *is* in fact the lift of the wings that is causing the plane to rotate, I would (guess ??) that the plane is actually rotating about the c.g. This is more or less a trivia question anyway <g>, but I guess it *is* important for anyone designing an aircraft !

I know this is a very old discussion now - one I haven't come back to until now. Yes, there is lift, probably not enough to fully support the aircraft's weight at this stage however. But rotation is definitely about the wheel axle, not c.g. - if it were about the c.g. it would require that the wheels sank some distance into the concrete, which can't happen. Thus the aircraft nose is actually levered upwards by the lift force acting against the fulcrum of the main wheels. But yes, you're right that really it's a small point. Graham 22:31, 8 December 2005 (UTC)

Two items... It's a common misinterpretation of the equations of motion that all objects rotate about their center of mass. We typically write those equations for the mass center because it allows us to decouple the translational and rotational equations. It's just a mathematical convenience, and shouldn't be interpreted as anything else. Think of any pendulum you've ever seen. It's rotational center is about as far from the mass center as you can get. Also, takeoff rotation for a fixed-wing transport category aircraft is calculated to occur such that three seconds after rotation is initiated the airplane is in the liftoff attitude and at the liftoff speed. (Take a stopwatch on your next commercial flight if you don't believe me.) So the whole question of whether or not the airplane is at 'flying speed' is irrelevant as well as poorly stated.

Removed text

In cost controls a take-off is the action of counting and measuring from drawings or specifications key words: estimating, construction, building, civil engineering, architecture, engineering Ref: Jose R. Teres 26/Oct/2005 http://www.mikeholt.com/news/archive/html/master/electricalestimatingandpm4.htm

- Ste|vertigo 19:36, 8 December 2005 (UTC)

"Autorotation is where an aircraft will do this by itself when it reaches some speed." I think you have this confused with autorotation of a helicopter. An autorotation is used when the engine fails, or when a tail rotor failure requires the pilot to effectively shut down the engine. It is very similar to gliding in an airplane. I know of no aircraft that will make an automatic takeoff.

removing reference to autorotation, as not relevant Cyclopaedic 19:26, 28 April 2007 (UTC)

take-off, take off, or takeoff

article mentiones takeoff but also take-off . Is it takeoff, take off, or take-off? i need this for an article. thank you.

Take off when a verb. Takeoff or take-off when a noun. Cyclopaedic 19:02, 28 April 2007 (UTC)

Take off speed versus weight

"The take off speed is directly proportional to the aircraft weight; the heavier the weight, the greater the speed needed."

this seems rather misleading and perhaps outright wrong. ive always been under the impression that take off speed is proportional to the effectiveness of the aircrafts wings, the effectiveness itself being determined by the wing surface area primarily, and also by left-generating devices, geometry, etc. this is why planes as varied as a 737 and a 747 and an antonov 124 all have comparable take off speeds, but a concorde has a much higher take off speed.

at best, this statement would need to be amended to say that take off speed is directly proportional to aircraft weight and inversely proportional to the effectivensss of its wings. but arguably, the wing configuration is the overwhelmingly important criterion. Downward machine 18:45, 24 December 2006 (UTC)

For any given aircraft, the quote from the article is 100% true. Comparing unlike aircraft is not the intention of this statement, so perhaps it should be written more clearly ;)--chris.lawson 00:39, 26 December 2006 (UTC)

I think the term "directly proportional" is wrong in this case. Direct proportion is the kind of relation that is expressed as Y = aX. In this case when you multiply the value X with 2,you also multiply the value of Y with two. Now think about boeing 777 - 200 LR. When it performs a takeoff with no payload and just 10 tonnes of fuel, its weight would be 158121 kg. And if it performs a takeoff with MTOW, the wieght would be 347550 kg. The proportion between them is 2.198. The term "directly proportional" implies that the takeoff speed in the latter case will be 2.198 times as much as the takeoff speed in the former case. This doesn't seem to be quite possible. Gokaydince (talk) 16:41, 1 October 2008 (UTC)

The phrase "directly proportional" is 100% false and Chris Lawson is 100% wrong, as Gokaydince correctly intuits. In fact, for a fixed-wing (non-Short TakeOff) plane, the lift must exceed the weight, and lift equals a constant (wing planform area), times the "wing effectiveness" (we call it lift coefficient), times the dynamic pressure, which equals one-half the air density times velocity squared. Thus the ratio of takeoff speeds at two conditions is roughly proportional to the square root of the weight ratio, which in Gokaydince's example would be 1.4826. ("Roughly" because there might be a difference in angle at liftoff, which changes the lift coefficient.) JustinTime55 (talk) 21:32, 25 July 2013 (UTC)

The statement in the article is currently: For a given aircraft, the takeoff speed is usually dependant on the aircraft weight; the heavier the weight, the greater the speed needed. The only situation where takeoff speed is not dependent on weight is in a multi-engine aircraft when the weight is so low that the takeoff speed is equal to minimum control speed Vmc, or perhaps 110% of Vmc. (Vmc is not affected by aircraft weight.) Dolphin (t) 23:50, 25 July 2013 (UTC)

Thanks for the clarification. The article doesn't seem to mention the minimum control speed. I was planning to put the lift equation in the article, and invert it to explain the square-root relationship to weight. We should then explain Vmc, and say something like "The takeoff speed can't be lower than the minimum control speed, therefore in some cases where the takeoff weight is sufficiently low, the takeoff speed becomes invariant with weight." I see the article V speeds mentions Vmc, and there are several versions of it, and it's dependent on the assumption of one engine out for multi-engine aircraft. (I assume it must still exist for single-engine aircraft?) JustinTime55 (talk) 15:57, 26 July 2013 (UTC)

No, single-engine aircraft don't have a minimum control speed because there is no asymmetric thrust when that one engine fails. Centerline thrust aircraft like the Cessna 337 don't have a minimum control speed, even though they have more than one engine. Dolphin (t) 13:15, 31 July 2013 (UTC)

fuel consumption during take off

I have heard that airplanes consume 50% of the fuel during take off. Is that a myth? Or is it real?

59.93.41.59 08:03, 26 April 2007 (UTC)mohan (mohans@msn.com)

Myth, for anything resembling a normal flight. A perversely clever performance engineer might be able to construct a flight plan for which this statistic is true, but you would have a very hard time selling tickets for that flight.

In a normal flight the engines are at the highest power setting during takeoff. So while it's true that the rate of fuel burn is highest at takeoff, the total fuel consumed getting to your initial climb altitude isn't even remotely half of the total fuel load.

Pictures - too many?

Having four pictures of mid-sized Boeing and Airbus passenger jets taking off seems a bit excessive. Can we perhaps have some pictures of some smaller, non-military, planes taking off - maybe a microlight? 217.155.20.163 19:53, 5 June 2007 (UTC)

Speed required

On 14 May 2012 User:Henrsail added the following text to the article Takeoff. It is not yet suitably encyclopedic so I am removing it from the article and transferring it here on the Talk page. Dolphin (t) 23:15, 14 May 2012 (UTC)

From the article on takeoff.

Takeoff is define as the F(thrurst) required with one engine and Vr ,V1 to used TOFL and clear obstacle. This is taking into account flap setting and field density.

Formula: comes from F=ma but is a liniar ,we to take into account some aerodynamic effects in the moving aircraft at differen configurations anf conditions.like rain ,snow ,wind ,runway slope and flap settings,obstacle.

F(thrust)-Drag=Weight(takeoff W)*acceleration+L/.5*v*v*& + v1+vr+ angle of attack

this is my own definition and is not accurate .It gives an overall different variables in takeoff.

The books definition gives as thurst dependent of groun roll

Sg=1.44(W/S)to/&ș*Cl max[T/W-D/W-u(1-L/W)] where lift,drag,and thrust terms are evaluated at a speed of .7Vto. — Preceding unsigned comment added by Henrsail (talk • contribs) 16:18, 14 May 2012‎

Restore section on take-off optimization

Just about a week ago, user Dolphin51 removed a whole section on take-off optimization, saying that the material was unsourced and made by a new user. After looking at the section, I found that it contained a great quantity of more detailed information about the mechanics of takeoff. It definitely is not original research, and the writing is not inherently bad because an inexperienced user created it (possibly not knowing about the Wikipedia sourcing requirements). Because the content is good enough to contribute significantly to this article's coverage of the subject, I think that the section should be restored once reliable sources are found for the information. It would be a shame to exclude this type of information, which might only come from an expert on the subject. Mooseandbruce1 (talk) 04:54, 4 September 2016 (UTC)

Would it be acceptable if I restored the content and put a Refimprove tag at the top of the section? Mooseandbruce1 (talk) 05:00, 4 September 2016 (UTC)

I think it would. Template:Unreferenced section is what you want here. In my experience, reference-improve tags result in mostly nothing when applied to “expert” content. May be we can give JustinTime55 (who added the content) a month or so before Dolphin51 or myself removes unreferenced content again. Ariadacapo (talk) 06:35, 4 September 2016 (UTC)

If the material in question can be presented in a style appropriate to an encyclopedia, and if there is good prospects of someone supplying reliable published sources, I will have no objection to it being restored.

The material in question wasn't added by JustinTime55. It was added by Baliga0411 on 26 November 2015 - see the diff.

The material in question contains many elements of truth but it is compiled and presented in a very amateurish manner. Some of it duplicates statements that exist in the original paragraphs in the Section. Most of it appears to be about half true. Dolphin (t) 07:22, 4 September 2016 (UTC)