Talk:Slip (aerodynamics)

The 2nd paragraph under "Sideslip angle" needs support, either by explanation or citation. The first sentence could be describing angle of attack as well as sideslip angle. As for the second and third sentences, I don't understand why these would be true, or why turning is relevant to the sideslip angle; this should be explained. — Preceding unsigned comment added by BobSundquist (talk • contribs) 14:08, 2 August 2013 (UTC)

Direction of positive sideslip angle beta

The graphic that is currently used gives a false impression of the definition of beta: for positive angles beta, the relative velocity vector points to the right of the nose, not to the left as currently shown. When looking from the top on an aircraft flying horizontally, the angle of sideslip is defined positive clockwise. Refer to the first page of this for details: [1] Hopefully somebody can adjust the graphic to show this. — Preceding unsigned comment added by 2A01:C22:7A3F:4D01:DDB5:8516:4405:DD0 (talk) 07:53, 18 January 2022 (UTC)

Merge?

I think that the page sideslip angle should be merged into this article, seeing as it is a part of the sideslip itself and the sideslip angle page provides information on calculations that I think should be included in this page. Ekkoria (talk) 04:06, 17 December 2009 (UTC)

• Agree .--Reinstall (talk) 16:12, 2 November 2011 (UTC)

Older talk comments

Whoever wrote this page, you are confused between sideslip and forward-slip. Definitions are correct though, it is just the names. If you think I am wrong, do some research or leave a message and I will quote you the definition form a book. En51cm 02:12, 7 November 2006 (UTC)

Deathpoo, do you think I am wrong, or are you trying to sabotage the page? Please comment on why you swap the definition of Forward-slip and Sideslip back to the old ones(perharps the wrong ones)? For reliabilty of the information, it was from the a "The Air Pilot's Manual" a JAR-FCL PPL recomended book. Other wiki user please comment on this as well. (see history for detail) En51cm 17:41, 9 November 2006 (UTC)

Removed warning, added introductory text for clarification, useage, and cautions. Use in landing was moved to slideslip section, since the heading is maintained while adusting the track with the ailerons. (Perhaps this may have been the point of confusion between En51cm and Deathpoo?- Leonard G. 03:27, 20 November 2006 (UTC)

Nice photo of a glider (especially since I got permission for it), but it does not really illustrate the article. It needs a photo showing a runway and a plane pointing somewhere else. JMcC 08:52, 3 January 2007 (UTC)

Leonard G, thanks for the correct forward/side slip definitions. It would be nice if someone can add the method entering both manoeuvres from the pilot point of view. En51cm 02:53, 9 February 2007 (UTC)

Forward or Side

This reader also confused .. the first sentences of Forward-slip and Sideslip appear to describe exactly the same procedure. Track and Heading are surely the same thing, in this context, both being relative to the ground? That is, the track is the vector over the ground that the aircraft is following, and the heading is the bearing (direction) component of that track (as opposed to where the nose of the aircraft is pointing).

Some clarification is needed, one way or another... quota (talk) 17:39, 2 December 2008 (UTC)

Under normal flight conditions and with zero wind (or direct headwind or tailwind) heading and track will be identical, heading being the direction the nose is pointing and track being the direction the airplane flying. It is possible to set up the aircraft so that it will not fly in the same direction in which the nose is pointing. For example, if the pilot applied right rudder (while countering the effects of roll produced by the rudder) the aircraft will have the tendency to remain on its original track even though the direction of the nose has been yawed to the right. The aircraft is indeed turning, but only slightly. It is essentially flying somewhat sideways and its track is largely unchanged by the yaw. When the rudder is released, the aircraft will have the tendency to have its nose swing back to the direction of its track. Another example of this is the forward slip. On final approach, the pilot may judge that the aircraft is too high and may want to bleed some altitude. The pilot will yaw to the right and maintain right rudder throughout, and then roll to the left (in that order) while pitching down slightly. The pilot is now in a forward slip and will notice that although the longitudinal axis of the aircraft is not inline with the runway, the direction in which the aircraft is flying is still parallel to it. Hope that clarifies things a little. Perwisky (talk) 21:14, 4 June 2009 (UTC)

Written from a Pilot POV

I've noticed this is written from a "pilot" point of view (mostly). That's okay, even good, because a "slip" is more pilot language while "sideslip" (see Sideslip angle) is more aeronautical engineer language, and the name of the article is "Slip" after all.  :-).

I would like to make it more explicit about what is "pilot speak" and add a little "engineer speak" with references to the Sideslip angle article. That way we can clarify things like:

• In the pilot world a slip and a skid are different, but they are the same to an engineer.
• etc.

I'll take care of those changes "sometime soon". :-).

--Gummer85 (talk) 19:46, 4 April 2009 (UTC)

Needs major reorganization.

This article is all over the place. It covers things that are off-topic. It covers things that are covered elsewhere in Wikipedia. It is incorrect on many points. It is haphazard in organization.

I'm warning anyone who cares that I'm gonna tear it up and put it back together right.  :-).

I'll try to "be nice" and post big changes for comment.

It might end up much smaller than you're used to.

It'll be MUCH BETTER. Trust me.  :-).

Anyone got any problem widat?

Anyone wanna help?

Speak up!  :-)

--Gummer85 (talk) 21:00, 4 April 2009 (UTC)

Actually, I'm starting right away with "low hanging fruit". That is, small changes that are unlikely to be objectionable that make big improvements.

--Gummer85 (talk) 21:03, 4 April 2009 (UTC)

I did indeed take care of "low hanging fruit" - in just 8 steps. It's readily undoable if there are major objections. I moved things around while deleting very little. I think the organization is vastly improved (but still imperfect!). There is still a lot of correcting needed, but at least it's much easier to know where to hang new info, etc. I got the TOC to the top! Woo Hoo!  :-)

--Gummer85 (talk) 22:16, 4 April 2009 (UTC)

Forward Slip and Side Slip - Hard to figure out.

I am a pilot as well as an aeronautical engineer. I know that often "pilot speak" is different than "engineer speak". It is frustrating sometimes to see something so gosh darned simple as Angle of sideslip be made so complicated when put in the required language of traditional pilotspeak. Even so, I do understand the "pilot's eye" differences between:

• Forward Slip
• Side Slip
• A turning slip
• A turning skid, and
• An uncoordinated "turn" (or better, "uncoordinated roll")

Even though these are all almost exactly the same gat-danged things, the differing contexts make them different things to a pilot (or to an easily confused layperson). It shouldn't, but it does. Pilots are taught wrong about this in my opinion. For historical reasons, they're taught that way and I can't change it until I start a flying school and write a great book like Langewiesche or Kershner[2].

Anyway, I know what all those things are even in pilotspeak, but I don't know what the current Forward Slip and Side Slip text is really trying to say. It's written like a Pilot "How-To" manual, but I don't think that's what we need. I think it has the hand of many authors trying to fix it little by little. It darts about , changing subjects quickly while it tries to talk about everything. I'll fix it up better. "Trust me."  :-)

Hmmm... It seems that a FS, and a SS, and a turning slip, and a turning skid are pilot maneuvers where a pilot gives the plane some amount of sideslip angle in one direction or the other either by mistake or for some operational purpose. Hmmm... maybe I'll put things in that context.

--Gummer85 (talk) 07:28, 5 April 2009 (UTC)

How about describing Slip first, very plainly, then go on to how the other variations of the term have different nuances/meanings to different users of the term? And don't forget you can always do this as a side copy of the page (or here in Talk) for comment if you are worried about major edits on the current article. quota (talk) 20:04, 7 April 2009 (UTC)

I am also a pilot (private and glider) as well as a mechanical engineer and I have to disagree with you about all these types of slips being "almost exactly the same gat-danged things." They are only slightly similar in that the aircraft in all these scenarios is "slipping" to one side (ie. the velocity of the aircraft has a component in the direction of the lateral axis). However, forward slips and side slips are initiated differently and are used for different purposes. Moreover, they are essential in the pilot's arsenal of maneuvers. I've heard many people (including some pilots) refer to both maneuvers as side slips, much to my dismay. I am happy to see an article on the net that differentiates the two. I agree however that it is somewhat lacking in certain areas, but wikipedia is an encyclopedia, not a flight manual. Perwisky (talk) 22:10, 4 June 2009 (UTC)

Removed erroneous and unneccesary information

Removed part of sideslip section due to incorrect information regarding side-slip for altitude bleed in sailplanes... A forward-slip is much more common. —Preceding unsigned comment added by 76.64.125.111 (talk) 02:49, 4 April 2010 (UTC)

Diagrams

It would be nice if there were some diagrams to accompany the descriptions. Kevink707 (talk) 16:03, 8 October 2012 (UTC)

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Forward Slip Required for Solo?

Over 50 years around and in aviation, and I've never known the mastering of slips being required before a student solos. Perhaps this is something new, or something required in countries other the U.S.

Forward slips are usually used in aircraft that don't have flaps, and have little practical application in modern aircraft. Some pilots like to do them to impress observers. There's always been too much similarity between forward slips and cross control stalls to suit me. Something you don't want a 10 hour student pilot messing around with, especially on final at low altitude. ~eelb53

I removed the offending paragraph. It had been marked “Dubious–discuss” since May 2016. Dolphin (t) 22:38, 22 August 2021 (UTC)

Notable employment of the slip

For many years the Section titled “Notable employment of the slip” has included the example of TACA Flight 110, claiming the Captain employed a slip to correct the course of a Boeing 737 prior to making a forced landing after a double engine failure. This information challenges all credibility! Pilots do not use the slip manoeuvre to change heading or correct the course of a fixed-wing aircraft because they have ailerons for that purpose! The sources cited to support this claim regarding TACA Flight 110 consist of a YouTube video or a television documentary. These do not qualify as reliable published sources, especially for the purpose of supporting such an unbelievable claim as this one regarding TACA Flight 110 using the slip to change course in order to land on a grass levee.

In April 2022 I removed all mention of this flight - see my diff. It was restored by Brycehughes on 12 May - see the diff. I have removed it again today. I’m happy to discuss this further. Dolphin (t) 06:42, 12 May 2022 (UTC)

I agree. It's ludicrous. You can put the aircraft into a slip with the rudder, but all this changes is the direction the nose is pointed in. It's doesn't alter the velocity vector enough to really even be noticeable. It's a common tactic employed in guns defense maneuvering to make the attacker think you're moving in a different direction than you really are. The only type of maneuvers in which the rudder is truly effective in altering course are things like wingovers, stall turns, and rudder rolls. Zaereth (talk) 07:07, 12 May 2022 (UTC)

@Dolphin51 and Zaereth: Fair enough. I do have one question for you both. There's a copy of the Air Crash Investigation episode here: [3]. If you jump to about the 20:45 mark, you hear the "sideslip"/"course correction" claim from the narrator. Are you saying this is BS? It very well might be; I'm sincerely curious. I would have assumed Air Crash Investigation was documentary-level quality, but perhaps it's not! Thanks, Brycehughes (talk) 12:21, 12 May 2022 (UTC)

Surprisingly, the standard for information to be included in an encyclopaedia is not truth! It is verifiability - see Wikipedia:Verifiability, not truth.

It is likely that the narrator of the TV documentary is speaking the text written by a professional screenwriter. Alternatively it is possible that the narrator has some knowledge of aeronautics and feels sufficiently confident to speak his own thoughts. None of these considerations is sufficient to give confidence to pilots and others who have a good understanding of how airplanes operate. Pilots of light aircraft sometimes employ crossed controls to increase drag or cause the aircraft to slip sideways in unbalanced flight, but crossing controls would not cause a turn or a change of course, and should not be used in a passenger-carrying airplane such as a Boeing 737. So the claim is unbelievable, and the fact that it was spoken by someone on television doesn’t make it any more believable.

I had a quick look at our article on TACA Flight 110 and it appears to say nothing about this non-standard manoeuvre prior to touch-down. Dolphin (t) 12:36, 12 May 2022 (UTC)

Yeah, like I said, I was just curious. I suppose I would quibble with your claim that the type of medium (in this case television) is a direct indictment of source quality, although I would agree that there is a correlation of sorts (a lot of crap on TV). It might be the case that the pilot performed a slip, but then the narrator's "course correction" claim was incorrect, and that in itself is an indictment of the source here. I'll note, for what it's worth, that the 737 was gliding at the time, much like Gimli. Brycehughes (talk) 12:43, 12 May 2022 (UTC)

I agree that both engines had failed so the airplane was gliding. I also accept that the pilot may have deliberately crossed controls briefly before touchdown, but why he did so, and whether it achieved the desired effect has not been clarified. The fact that the pilot crossed the controls is of little significance in the account of the forced landing of this airplane. Much can be written to do justice to a description of this forced landing but I would ask why any words need to be devoted to the fact that controls were crossed for a few seconds.

The pilot of the Gimli Glider appears to have been troubled by significantly excess height so resorted to crossed controls for many seconds, perhaps a significant fraction of a minute, in order to lose a lot of height, but I also suspect that the slip manoeuvre is of only minor relevance in any account of the forced landing of the 767. Dolphin (t) 13:21, 12 May 2022 (UTC)

Fair points. It might be worth removing the "Notable employment of the slip" section altogether, since there is only one entry and per your explanation it seems to border on trivia (as would my entry, were it true). Brycehughes (talk) 13:29, 12 May 2022 (UTC)

Your suggestion regarding removing the Section is a valid one. Let’s see what comments are made by Zaereth and others. Dolphin (t) 13:44, 12 May 2022 (UTC)

There are so many variables at play, and unless you're the pilot flying the plane, it's almost impossible to play arm-chair quarterback and try to guess what was happening to the plane in that particular moment. In general, anytime you change a control surface it will have an effect on the direction the aircraft wants to go. At normal flying speeds, the rudder has very little authority to change the aircraft's direction of travel. It will try to turn the plane like a boat, but it is extremely slow going and will tend to impart more roll on the plane than turning motion, which you'll need to compensate for with aileron. You can use this on approach if you're still a few miles out and need to make the most minute corrections to get the craft lined up with the runway, where using the ailerons would more likely produce an over-correction. However, the larger the plane and the higher the speed makes this far less effective.

Now if you're flying in a crosswind, then you're probably already in a slip, or what's called crabbing. It's not unusual for planes (or boats) to be moving in a different direction than the nose is pointing. So if you're crabbing up to a runway or landing site, you have to use the rudder at the last second the to line the fuselage up with the runway so you don't skid the wheels or flip the plane. I would imagine something like that would be more the case here, which is like putting the plane into a slip, except in reverse. Your actually using rudder to get the plane out of a slip so it can land properly, but not changing the actual course. Zaereth (talk) 18:08, 12 May 2022 (UTC)

@Zaereth: That's really interesting... thanks for the explanation. While you're here, do you have an opinion on removing the "Notable employment of the slip" section altogether? If I am interpreting you and Dolphin51 correctly, it sounds like the most "notable incidents" are actually some of the least notable (i.e. least effective) and most dubious usages of a slip. Brycehughes (talk) 18:38, 12 May 2022 (UTC)

No need to ping. I have this on my watchlist. What the source is describing there is really a form of aerodynamic braking, that is, increasing the surface area of the plane in the direction of the relative wind to slow it down. Good thinking, but this is not a reliable secondary-source. I would equate it to a book like Chuck Yeager wrote about his experiences. We have no secondary-source analysis to tell us why he did this or how exactly it worked, so we're relying on our own interpretations of the story. I would simply remove it with the section heading as well.

Now, this article could use some expansion to show various uses. Crabbing is a good example. When you approach an aircraft carrier to land, they don't stop the boat and wait for you. A carrier landing is more of a controlled crash than a true landing which is why Navy planes have such beefy landing gear. Try that with an Air Force plane and you'll crumple your main mounts. Upon approach, your trying to hit this runway that is moving away from you, on what amounts to a postage stamp floating in the ocean. This runway is at an angle to the line of approach, so to land you have to crab the plane on in there. Another example of a slip is described here:

Pulling up into his blind spot I watched his plane grow larger and larger in my sight. But this German pilot was not content to fly straight and level. Before I could open fire his plane slewed to the right, and seeing me on his tail, he jerked back on the stick into the only defensive maneuver his plane could make. I banked my 47 over to the right and pulled back on the stick, striving to get him once more into my ring sight. The violent maneuver applied terrific G’s to my body, and I started to black out as the blood rushed from my head. Fighting every second to overcome this blackness about me, I pulled back on the stick, further and further, so that the enemy would just show at the bottom of my ring sight to allow for the correct deflection.

We were both flying in a tight circle. Just a little more and I’ll have him. Pressing the [trigger] I waited expectantly for the 109 to explode. I’ve hit his wing. A section two-feet long broke loose from the right wing as the machine gun cut like a machete through it. Too low, a little more rudder and the bullets will find his cockpit. I could see occasional strikes further up the wing, but it was too late. The 109, sensing that I was inside him on the turn, slunk into a nearby cloud. Straightening my plane, I climbed over the top of the bank, and poised on the other side, waiting for him to appear. But the 109 did not appear, and not wishing to tempt the gods of fate further, I pushed my stick forward, entered the protective cover of the clouds, and headed home.

As you can see, the pilot is using a slip to get his cannons aimed at the enemy aircraft. Now this is an example of an account taken from a book written by a fighter pilot, yet this account was used as an example by a secondary source (Fighter Combat: Tactics and Maneuvering by Robert Shaw) which gave their own analysis of the account. Whatever, we add, we need good sources. Zaereth (talk) 20:15, 12 May 2022 (UTC)

.

Sounds like a vote to ditch the section to me. I'll let this steep a bit and then remove the section if no further comment. Agree that article could use (well-sourced) examples, and I don't think notable events is what we want to use for this, for the reasons stated above. Brycehughes (talk) 20:29, 12 May 2022 (UTC)

I’m in favour of the Section, title and contents, being removed. Go for it! Dolphin (t) 23:06, 12 May 2022 (UTC)

Done. Cheers all. Brycehughes (talk) 00:55, 13 May 2022 (UTC)

Looks good. Thanks. By the way, I have to admit, it was an interesting source. Very ballsy move and quick thinking, but not only did he have to put the plane into a really deep slip, but also roll opposite of the direction the slip was trying to roll the plane, to give added surface area from the wings too, and yet still be able to recover before touchdown. In the air, though, you don't have time to consciously think about these things. You just make that plane do what it's gotta do. But it's not a great example of anything here, so thanks for the discussion. Zaereth (talk) 02:08, 13 May 2022 (UTC)