User talk:Mbcannell

Welcome!

Hello Mbcannell, and welcome to Wikipedia! Thank you for your contributions. I hope you like the place and decide to stay.

In Wikipedia, new Users do not automatically receive a welcome; not even a machine-generated welcome. Welcome messages come from other Users. They are personal and genuine. They contain an offer of assistance if such assistance is ever desired.

I suggest to everyone I welcome that they may find some of the following helpful — there’s nothing personal in my suggestion and you may not need any of them:

I hope you enjoy editing here and being a Wikipedian! Please sign your name on Talk pages (ie discussion pages) using four tildes (~~~~); this will automatically produce your name and the date. If you need help, check out Wikipedia:Questions, ask me on my talk page, or place {{helpme}} on your talk page and ask your question there. Again, welcome! Dolphin51 (talk) 04:03, 23 April 2009 (UTC)[reply]

Verifiability

Hi Mark. I see you are doing a lot of good work to add extra content to Wikipedia articles related to aviation. I also notice that most of your additions are not supported by references or in-line citations to enable independent verification. (Your in-line citation of the www.dfrc.nasa.gov site to support your comment about the X-31 is good.)

Many of the technical articles in Wikipedia, and certainly those in the aviation field, are not well supported by references and in-line citations. That is why those articles usually have a headline banner calling for extra references and in-line citations. (Some Wikipedia editors focus most of their efforts on finding references and citations to support existing text, rather than focussing on writing extra text.) Detailed information about how to provide in-line citations is available at WP:CIT.

As well as writing extra text, please take the time to provide in-line citations to support your work, and to enable independent verification. Information that is not supported by one or more citations is likely to be original research and is not acceptable in Wikipedia, so it is likely to be deleted. See WP:NOR.

WP:Verifiability contains the advice that The threshhold for inclusion in Wikipedia is verifiability, not truth.

Happy editing. Dolphin51 (talk) 00:56, 25 April 2009 (UTC)[reply]

Signing your posts

Hello. In case you didn't know, when you add content to talk pages and Wikipedia pages that have open discussion, you should sign your posts by typing four tildes ( ~~~~ ) at the end of your comment. You may also click on the signature button located above the edit window. This will automatically insert a signature with your username or IP address and the time you posted the comment. This information is useful because other editors will be able to tell who said what, and when. Thank you. -- Crowsnest (talk) 09:32, 25 April 2009 (UTC)[reply]

Aerobatics article change

Hi Mark. Just a friendly note to let you know that I've undone your change to the Aerobatics article because of inaccuracy. (Hard and actually a bit uncomfortable to believe, but people regularly pull +10 and push up to -10 g's.) See the article's talk page for more. Best regards, Jim Ward ^{(talk·stalk)} 19:32, 26 April 2009 (UTC)[reply]

Four tildes

Hi Mark. I'm not sure what the problem is with the four tildes, but here are some suggestions.

I tried playing around using the sandbox. I typed one tilde on a line, then a couple of lines below I typed two tildes (no space in between). A couple of lines below that I typed three tildes, then four, then five. It looked like this:
~
~~
~~~
~~~~
~~~~~

Then I selected Show preview. One and two tildes produce nothing unusual. Three tildes produces my User name and link to my User talk page, but no date or time.

Four tildes produces User name, link to my User talk page, plus date and time.

Five tildes produces date and time, but no User name or link to User talk page.

I suggest you use the sandbox or your User page or this Talk page to experiment, as I described above. (You don't need to Save page - just Show preview is sufficient.) I'm sure you will quickly see what works and what doesn't. Don't hesitate to get back to me if you continue to strike a problem. Cheers. Dolphin51 (talk) 05:21, 29 April 2009 (UTC)[reply]

Hello Mark. If you click "my preferences" on top, in the tab "User profile" there is the box where you can put your signature. Right below is the checkbox "raw signature"; make sure that is unchecked, and save. See: Wikipedia:Help desk/Archives/2008 October 25#Signature problems, Wikipedia:How to fix your signature and WP:Signatures. -- Crowsnest (talk) 09:27, 29 April 2009 (UTC)[reply]

Stall (flight)

Hi Mark. On 1 May you edited Stall (flight) to add a comment about the commonality of stalls after takeoff. You called these stalls departure stalls and you cited the FAA Airplane Flying Handbook, Chap 4, pp.11-12. In the context of the stall, departure usually refers simply to a departure from controlled flight at any height, and any phase of flight. The notion of departure from controlled flight is even mentioned explicitly on Wikipedia at Departure.

I haven't been able to find mention of departure stalls after takeoff at pages 11-12 of Chap 4. Could you check your edit on this subject to ensure that all you have written is covered by your cited sources? Thanks. Dolphin51 (talk) 11:36, 3 May 2009 (UTC)[reply]

That's not my terminology. I just moved the whole paragraph. Please check. Thanks MarkC (talk) 09:00, 4 May 2009 (UTC)[reply]

Thanks Mark. I now see what has happened. Cheers. Dolphin51 (talk) 12:13, 4 May 2009 (UTC)[reply]

Flap (aircraft)

Hi Mark. On 1 May you edited Flap (aircraft) in the area of the lift equation. Prior to your edit, the term V was explained as the velocity of the aircraft (airspeed). You changed it to velocity of the airflow.

I have now amended it to explain V as the true airspeed of the airplane. Let me explain why I changed your recent edit.

In the lift equation, rho (density) is usually either ambient density, or standard sea-level air density. If it is ambient density, V must be the true airspeed of the airplane or its reciprocal, the freestream velocity of the atmosphere. The prefix freestream is essential to indicate that it is velocity of the atmosphere relative to the airplane, a great distance from the airplane where the relative velocity is uniform and unaffected by the presence of the airplane. True airspeed of the airplane, and freestream velocity are numerically equal but opposite in direction.

Close to the airplane, the velocity of the airflow is not uniform. On the upper surface of the wing, close to the leading edge, the airflow has a relatively high velocity; while near the lower surface of the wing there is no localised region of high velocity flow.

If rho is standard sea-level air density, V must be the equivalent airspeed of the airplane.

I trust this explains why I changed your recent edit. Best regards. Dolphin51 (talk) 11:51, 9 May 2009 (UTC)[reply]

I think I see where you are coming from. But maybe I'm confused, the lift equation is based on the airstreem velocity in front of the aircraft before it hits the wing? This not the aircraft velocity is it (there's the pitch angle relative to airsream)?

Cheers MarkC (talk) 03:19, 10 May 2009 (UTC)[reply]

The lift equation, and its partner the drag equation, are not vector equations - they don't take account of angle of attack or specify the direction of the lift force or the drag force. These two equations are scalar equations - they only give the magnitude of the lift and drag forces. (Lift is defined to be perpendicular to the vector representing the relative velocity of body and atmosphere; and drag is defined to be parallel to this vector.)

The lift and drag equations are based on V, the relative speed of the body and the atmosphere. The speed of an airplane through a stationary atmosphere is equal in magnitude to the speed of the freestream relative to a stationary aircraft. (However, as vectors they are opposite in direction.)

Look at it this way - when applying the lift and drag equations it is equally correct to say the atmosphere is stationary and the airplane is moving at speed V; or the airplane is stationary and the atmosphere is moving at speed V. It is the freestream (a great distance from the airplane) that is moving at speed V. (The atmosphere close to the airplane is moving at a variety of speeds; sometimes faster than V, and sometimes slower than V, as the air diverts, speeds up and slows down as it flows around the airplane. There is no single value of V to represent the airstream close to, or in front of, the aircraft.) Dolphin51 (talk) 06:51, 10 May 2009 (UTC)[reply]

I see your point, I was thinking about the airspeed as a speed over ground -silly me. I'm puzzled by your statement above, first you say it is scalar and then state it is relative to airflow direction and a vector. I agree, most sources I've seen show lift and drag as orthogonal forces with drag axis in the direction of pre-wing airflow -and I'm sure they are vectors (Lift is a force so it must be a vector or tensor) -is that not right? The geometry can also be set by the AOA (which gives Cl) relative to the airflow? Cheers MarkC (talk) 15:09, 10 May 2009 (UTC)[reply]

Hi Mark. Some of my comments were a bit confusing. Drag, lift and velocity are all vector quantities but the drag equation and lift equation are not vector equations; they are scalar equations because they only give the magnitude of drag and lift. V in the drag and lift equations is the magnitude of the relative velocity so it is a speed rather than a velocity.

The direction of drag is parallel to the vector representing the relative velocity of the body and the fluid, so there is no reliance on the drag equation to find the direction of drag.

The direction of lift is perpendicular to the vector representing the relative velocity of the body and the fluid, so there is no reliance on the lift equation to find the direction of lift.

It is not uncommon in physics to have a scalar equation which contains terms that can be vectors. For example, kinetic energy is half mass times V squared. V is a vector but kinetic energy is a scalar so the equation that defines kinetic energy is a scalar equation and in this equation V represents speed (a scalar) rather than the velocity (a vector).

I guess there we disagree, v in that equation is a scalar... Thanks for the very didactic discussion tho' Cheers MarkCMarkC (talk) 09:12, 11 May 2009 (UTC)[reply]

In the drag and lift equations, what is V? It is the relative speed of the body and the fluid. Consider a body moving at 10 m/s through a fluid. If we are using the reference frame attached to the fluid we say the speed of the fluid is zero and the speed of the body is 10 m/s. Alternatively, if we are using the reference frame attached to the body we say the speed of the body is zero and the speed of the fluid is 10 m/s.

In this latter case we need to be careful in describing the speed of the fluid because the speed of the fluid varies around the body, particularly very close to the body, as the fluid diverts, accelerates and decelerates while it flows around the body. The speed of 10 m/s is not the speed of any fluid close to the body. It is the speed of fluid remote from the body where the presence of the body has not influenced the speed or direction of the fluid. It is common to refer to this speed of 10 m/s as the freestream velocity. Cheers. Dolphin51 (talk) 23:57, 10 May 2009 (UTC)[reply]

Hi there. You left some discussion on my page regarding steeper approach. Please permit me to explain:

1 - Flaps increase both lift and drag. There is no free lunch. 2 - Since flaps do increase lift, assuming all else is equal (see the general lift equation), the pilot would need to pitch down to achieve the steeper approach or to maintain altitude. 3 - Since the pilot has pitched down to accommodate flap deployment, indeed the additional drag from the flap extension prevents the airplane from picking up speed.

Therefore, both lift and drag together allow for the steeper approach. If you do a free-body diagram, you would need components of both forces to achieve your desire approach resultant.

Regards, J Jadias (talk) 05:29, 26 May 2009 (UTC)[reply]

RSS & UAH Data Image

Thank you for your comment. I have reverted Mr. Connolley's rv because in fact it is not a "duplicate image" -- the image I posted contains the links to the actual public domain RSS and UAH satellite data, whereas the Dragons_flight image does not. Also the public domain image I posted contains no processing (e.g. trendlines or any other processing). As the images are not congruent I believe that the apparent RSS and UAH data in the Dragons_flight image must have been processed but there is no reference to this nor to the data sources. If Mr Connolley rv's my image again I will submit this for arbitration. SunSw0rd (talk) 14:05, 5 August 2009 (UTC)[reply]

I think that the addition of raw data as WP:VER is highly desirable. The trend lines that have been added seem to be WP:OR as you note. Unfortunately Atmoz is now removing the figure by reversion and I've asked him/her to stop what seems to be vandalism based on the insulting comments he/she leaves. I am dismayed tho, at the tag team behaviour (to avoid 3RR?) of the 3-4 editors editors who seem to control the AGW topics. It's a pity their agenda has to be pushed at every opportunity rather than follow objective science. Regards 01:14, 6 August 2009 (UTC)