Talk:Balanced flight

Straight and level?

Is there a difference between balanced flight and 'straight-and-level' flight? If there is the article should state this. If there isn't it should make the distinction (they could be easily confused). Zephyrus67 14:31, 16 November 2007 (UTC)

Hi Zephyrus67. Yes, there is a difference between balanced flight and straight-and-level flight. In straight flight the aircraft flies continually in a particular direction; in level flight the aircraft flies continually at a particular height (or altitude). In straight-and-level flight the aircraft's direction and height remain constant.

My understanding of balanced flight is very different to what is stated in this article. My understanding of balanced flight is that a spirit level or other balance indicator, properly mounted level across the aircraft's instrument panel, shows that the forces on the occupants point straight down (or up) perpendicular to the floor of the aircraft. If the aircraft is not in balanced flight the pilot can restore balanced flight by appropriate use of the rudder or, if it is a multi-engine aircraft, ensuring all engines are developing the same thrust.

I think this article is significantly in error. I am not surprised there are no citations or references. I am unaware of any source that would support the meaning given to balanced flight in this article. I will put it on my list of things to do. Dolphin51 (talk) 13:26, 30 June 2008 (UTC)

The factual accuracy of this article is disputed

I believe Balanced flight is currently significantly in error. No references, sources or citations are quoted to support the current article.

I believe balanced flight exists when the aircraft’s sideslip angle is zero. An alternative way to describe this is to say the aircraft is neither slipping nor skidding. To assist a pilot maintain balanced flight all aircraft are equipped with at least one of the following instruments – turn coordinator, turn and slip indicator, or turn and bank indicator. Most glider pilots equip their gliders with a yaw string – a length of wool or cotton secured to the outside of the canopy so they can directly observe the orientation of the relative wind without having to re-focus inside the cockpit.

The view for the pilot of a Schempp-Hirth Janus-C glider. The yaw string (red wool) on the canopy and the balance indicator (top center of the instrument panel) both show the glider is not in balanced flight. The glider is slipping slightly to the right. Balanced flight can be restored by the pilot applying light pressure to the right rudder pedal.

Do other Wikipedia users agree with my understanding of balanced flight?

Here is my critique on some of the statements currently appearing in Balanced flight:

• Balanced Flight is the state an aircraft is in when it is traveling at a constant heading, with a constant airspeed, and at a constant altitude. In other words, the aircraft is not accelerating.

No, flight with a constant heading is called straight flight. Straight flight with a constant airspeed is called unaccelerated flight. Flight with a constant altitude is called level flight.

• This occurs because all of the four main forces that act on an aircraft in flight are in perfect balance, and they cancel each other out.

When the four forces cancel, the acceleration of the aircraft is zero (Newton’s First Law) and the expression unaccelerated flight is appropriate.

• When either thrust or drag is greater than its counterpart, the aircraft gains or loses airspeed.

Not true. When an aircraft is climbing at constant airspeed the thrust is greater than the drag. When an aircraft is descending at constant airspeed the thrust is less than the drag. It is not true to say that gaining or losing airspeed is the only outcome when there is excess thrust or excess drag.

• When either lift or gravity is greater than its counterpart, the aircraft gains or loses altitude.

Untrue. When an aircraft is climbing or descending the lift is less than the weight. (In straight flight, lift is only equal to weight when the aircraft is flying level. When climbing, some of the weight is supported by thrust, and when descending some of the weight is supported by drag.)

• However, it should be noted that the above explanation is a very simplified one.

Yes! This is something I might agree with. But it does beg the question as to whether such an over-simplified explanation has any place in Wikipedia.

What do other users understand by balanced flight? Dolphin51 (talk) 04:33, 1 July 2008 (UTC)

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Thanks for inviting me to have a look at this issue. To a large extent this seems to be a problem of terminology or semantics. Of course in Wikipedia the arbiter is verifiability rather than opinions! As a result I went looking for references and here is what I found:

• A large number of aviation flight training references that discuss lift, weight, thrust, drag and straight and level flight, turns etc, do not mention the term "balanced flight" at all. These include the fairly reliable US book Crane, Dale: Dictionary of Aeronautical Terms, third edition. Aviation Supplies & Academics, 1997. ISBN 1-56027-287-2

I found two very reliable Canadian references that discuss this subject:

• the Transport Canada Flight Training Manual 4th edition 1994 page 9 ISBN 0-7715-5115-0 says:

"Equilibrium

A body at rest tends to remain at rest and a body in motion tends to remain in motion in a straight line unless an external force is applied. This is Newtons First Law of Motion. A body that is neither accelerating nor decelerating may be said to be in equilibrium. A parked aircraft is in equilibrium; an aircraft in straight-and-level flight at a constant airspeed is in equilibrium; an aircraft in a straight descent or climb at a constant airspeed is also in equilibrium. However, an aircraft in a turn at a constant height and airspeed is not in equilibrium, since during a co-ordinated turn the aircraft is always accelerating toward the centre of the turn."

"A lot of effort is invested in designing aircraft to maintain a state of equilibrium. However, a pilot must be able to disturb this equilibrium to manoeuvre the aircraft. Flight controls allow a pilot to produce forces about the three axes of the aircraft (Fig. l-15). These forces disturb the aircrafts equilibrium and allow the aircraft to be manoeuvred."

and on page 60 of the same government manual:

"The turn is a basic manoeuvre used to change the heading of an aircraft. An accurate level turn may be described as a change of direction, maintaining a desired angle of bank, with no slip or skid, while maintaining a desired altitude. This is also the description of a co-ordinated turn. Aerodynamically the turn is probably the most complex of basic manoeuvres and involves close co-ordination of all controls."

• Aviation Publishers Co. Limited, From the Ground Up, page 19 (27th revised edition) ISBN 09690054-9-0 says on this subject:

"Forces Acting on an Airplane in Flight"

"There are four forces acting on an airplane in flight. These are thrust, drag, lift and weight."

"Thrust. The force exerted by the engine and its propeller(s) which pushes air backward with the object of causing a reaction, or thrust, in the forward direction."

"Drag. The resistance to forward motion directly opposed to thrust."

"Lift. The force upward which sustains the airplane in flight."

"Weight. The downward force due to gravity, directly opposed to lift."

"When thrust and drag are equal and opposite, the airplane is said be in a state of equilibrium. That is to say, it will continue to move forward at the same uniform rate of speed. (Equilibrium to steady motion and not to a state of rest.)"

"If either of these forces becomes greater than the force opposing it, the state of equilibrium will be lost. If thrust is greater than drag the airplane will accelerate or gain speed. If drag is greater thrust, the airplane will decelerate or lose speed."

"Similarly, when lift and weight are equal and opposite, the airplane will be in equilibrium. If lift, however, is greater than weight, the airplane will climb. If weight is greater than lift, the airplane will sink."

It would seem from these refs that the Canadian term for "balanced flight" is "equilibrium". The Canadian term for a turn that is neither slipping nor skidding is a "coordinated turn".

I then did a Google search to see if the term "balanced flight" is in use else where. I did find it associated with "carbon-balanced flight", meaning the same as "carbon-neutral flight" or "carbon-offset flight" - not quite the same subject!

The only close-to-reliable reference I could find (i.e., not this actual Wikipedia article, which comes up #1 on Google and other copies and mirrors of it) is in a podcast made by an Australian instructor. He spends the first half of the 8 minute podcast talking about how visiting pilots can get an Australian licence and then moves into basic flight maneuvers. He refers to a state whereby an aircraft has equal lift, weight, thrust and drag as "balanced flight".

This all leads me to believe that while the term "balanced flight" is not used in Canada or the USA (or probably the UK) it maybe used in other places in the world, such as Australia.

This is very similar to other problems found in aviation terminology. For example the line an aircraft traces over the ground while in flight is called "course" in the USA and "track" in Canada.

I don't know if any of this helps or not.

At this point I can only suggest that the article be amended to indicate the different terms used in different places to describe the same "aircraft steady state" and cite the refs I have noted here. That really brings up the greater question, though, about whether this article serves any purpose or whether it should be turned into a redirect somewhere else, although after a preliminary look, I am not sure where.

You may also want to have a look at another related non-sourced article Coordinated flight. - Ahunt (talk) 14:37, 12 September 2008 (UTC)

Thanks for doing that research, and for providing your sage comments. I listened to the podcast - it didn't seem to be particularly authoritative or to add much clarity to the subject of balanced flight. There may be some reference to the term in the syllabus for the Australian Private Pilot Licence. I will check.

I have done all my flying, and all my aeronautical engineering, in Australia but I'm not aware of balanced flight being a regularly-used expression - certainly not with the meaning currently given in Balanced flight. I am aware that many gliders have a flight instrument consisting solely of a spirit level and ball (ie a Turn and bank indicator without the gyro). That instrument is sometimes (often?) called the Balance Indicator. In this context, balanced flight would refer to the ball being centered in the spirit level.

You quote "From the Ground Up" saying Similarly, when lift and weight are equal and opposite, the airplane will be in equilibrium. If lift, however, is greater than weight, the airplane will climb. If weight is greater than lift, the airplane will sink. I wince every time I read this sort of statement because it is mostly untrue. Lift and weight are not equal when an aircraft is turning, nor when it is climbing steadily or descending steadily. If there is a momentary increase in angle of attack, such as when encountering an upward gust or when the pilot pulls backward on the elevator control, the aircraft will climb momentarily due to the sudden increase in lift. When an airplane is in a steady climb it is due to thrust exceeding drag, not due to extra lift. In fact, in a steady climb (and a steady descent) lift is less than weight. (When flying vertically upwards or vertically downwards, lift is zero. In straight flight, the lift on an aircraft is its weight multiplied by the cosine of the angle of climb or descent. Lift is maximum when that angle is zero.)

If we are unable to find any source to link the expression balanced flight to zero sideslip I think the best thing might be to redirect it to Coordinated flight. Dolphin51 (talk) 02:49, 13 September 2008 (UTC)

I do admit that the From the Ground Up quote, even though that is the standard ground school text in Canada, is an over-simplification. I agree that the podcast is not very authoritative. The fact that is was about the only reference to this term indicates that it may just be a colloquialism, or even a personal quirk on the part of that particular instructor.

I agree that, lacking any reliable references for this article Balanced flight, that this really should be made into a redirect to Coordinated flight, although that article needs some work, including some references, too!

After all as Jimmy Wales says:

I can NOT emphasize this enough. There seems to be a terrible bias among some editors that some sort of random speculative 'I heard it somewhere' pseudo information is to be tagged with a 'needs a cite' tag. Wrong. It should be removed, aggressively, unless it can be sourced. This is true of all information, but it is particularly true of negative information about living persons.

–Jimmy Wales

- Ahunt (talk) 13:55, 13 September 2008 (UTC)

Lacking any objections to this proposal I am going to go ahead and make the change. - Ahunt (talk) 11:47, 18 September 2008 (UTC)

Thanks. I agree that re-directing to Coordinated flight is the kindest thing that could be done to this erstwhile article. I have some references and citations for coordinated flight that I will add shortly. Dolphin51 (talk) 23:20, 18 September 2008 (UTC)