Talk:Basic fighter maneuvers
![]() | This article is rated C-class on Wikipedia's content assessment scale. It is of interest to the following WikiProjects: | |||||||||||||||||||||||||||||||||||||||||||||||
|
Info on individual maneuvers
[edit]I have added some info on some of the more basic maneuvers to this article, with plans to expand this article even more as my time permits. I welcome any comment, so please feel free to make a suggestion here.Zaereth (talk) 00:06, 17 March 2009 (UTC)
This is my first post on Wki, so bear with me if it's in the wrong place. I don't want to make any changes to any pages, but I will add a couple of comments.
High Yo-Yo
The purpose of a high yo-yo is prevent an overshoot when you are attacking and cannot beat your opponent's turn rate. Since roll rates are many times faster than turn rates, you go vertical, perpendicular to your opponent's turn circle, where you can beat your opponent's turn rate with your roll rate. After you've rolled to a more advantagous position, you can pull over and dive into a kill position at their 6 o'clock. Additionally, by going vertical into a perpendicular plane you prevent overshoot without slowing down, and conserve ennergy by converting airspeed to altitutude. You regain your speed in the dive onto their 6 o'clock. Of course, the primary counter to an attacker who is using a high yo-yo is to unload and extend downwards when the attacker gets nose high.
Unload and Extend
This is another defensive maneuver that you might want to include. It is basically running away. It is best performed when the airframes are pointed in opposite directions. As a defender, you can accelerate rapidly away from your opponent by leveling the wings and pushing over into a zero G dive at full military power. By going to zero G ("unloading") you eliminate the drag caused by lift. This, combined with military power and gravity, causes very rapid acceleration away from your opponent ("extending"). If your opponent's nose is pointed in the opposite direction when you do this, he will have to turn back towards you, limited by his turn rate, and hopefully by the time he gets his nose on you the range is too great for an effective attack.Hmarin (talk) 06:06, 12 February 2010 (UTC)
- First, I'd like to welcome you to Wikipedia. You're partially correct, but not exactly. Many of these maneuvers are far more complex that I've summarized here. Each one could use its own article so we can link to them.
- The High Yo-Yo was named after a Chinese pilot named Yo-Yo Noritake. First you have to consider that the primary purpose is to provide a reduction in speed. In the air, you can't just hit the brakes, at least, not the way you would in a car. By moving up into the vertical plane without increasing thrust, gravity will slow the aircraft's approach, thereby reducing its turn radius, this allows you to quickly out turn your opponent. From the US Navy's flight instruction manual:
- A high yo yo is an offensive lag pursuit maneuver designed to prevent an overshoot by controlling excessive closure while preserving range. A high yo yo is an outof-plane maneuver designed to control excessive down range travel so the fighter does not overshoot his intended target. As a fighter sees an overshoot developing, he will quarter roll away and raise the nose to slow the closure on the bogey's flight path. The out-of-plane maneuvering will place the nose of the fighter above the plane of attack and exchange airspeed for altitude. The combination of the out-of-plane maneuvering and the slower airspeed will allow the fighter to turn with a smaller radius while aligning fuselages. The fighter's slower airspeed will also reduce the closure rate allowing you to maintain or increase range. An alternative to the high yo yo would be to pull power and pop the speedbrakes. Although a viable alternative, this will deplete your energy package and may reduce or eliminate your offensive advantage.
- During such an out-of-plane maneuver, you set your lead, pure, or lag by aligning your lift vector either ahead, at, or behind the opponent. Unlike the animation in the article, a high Yo-Yo doesnt use such a high vertical climb and is often followed on by a wingover, bringing the fighter back into the plane of attack. This why we need a section about out-of-plane maneuvers.
- When you say "unload," what you're referring to is "relaxing the turn." In other words, when you straighten out your flight path you remove the resistance caused by the turn. (See wing loading.) Your kinetic energy (speed) will begin to increase. By combining that with a shallow dive, as you've said, you add the force of gravity to your speed increase to "extend." This refers to a sufficient increase in range to get away. This only works if your energy package is far greater than the attacker's. You need enough of a speed and altitude advantage to pull it off. If the attacker is moving faster, or at a higher altitude, then you won't be able to accelerate fast enough. In that case it's best to try and reduce your energy package, (slow down), by going into a hard break. This will usually cause the faster moving attacker to overshoot, although this is usually a "flightpath overshoot" and not a "3/9 line" (dangerous) overshoot. Zaereth (talk) 17:52, 12 February 2010 (UTC)
- I've added a section about out-of-plane maneuvering, so, hopefully, the maneuvers section will be easier to understand. I'll work on other useful maneuvers within the next few weeks, such as the defensive spiral and the "unload and extend" as described above. these should probably be separated into section labled "offensive maneuvers " and "defensive maneuvers." Thanks for your help Hmarin! Zaereth (talk) 01:48, 17 February 2010 (UTC)
Thanks. I think we're both saying the same thing about the high yo-yo for the most part, but we're using slightly different language. All well and good, I like your terminology better. Except that getting out-of-plane as you say does allow you the additional benefit of using your roll rate to help you beat your opponent's turn rate. I like the background about where the name yo-yo came from. Why isn't all this stuff on the main page where it belongs?
Now about "unloading and extending..." Unloading can be relaxing the turn as you mentioned. However, the "unload and extend" maneuver of which I speak is not relaxing the turn.
The "unload and extend" maneuver of which I speak is used to runaway from an attacker. "Unloading" in this context means pushing over to zero-G, not relaxing the turn. Total drag is the sum of lift-induced drag and parasite (airframe) drag. Depending on the speed, lift-induced drag can be significant. By going to zero-G you are left only with parasite drag.
The "unload and extend" maneuver is performed by leveling the wings and pushing the stick forward to achieve a zero-G dive, while at the same time pushing the throttles to military power. When you go to zero-G you eliminate the drag caused by lift and acceleration is rapid. We used to accelerate to greater than Mach 1.0 in just a few seconds doing this. Leveling the wings also aligns the dive vector with the gravity vector for maximum acceleration.
When you unload and extend, you quickly find yourself going downhill like a bat out of hell, diving at speeds greater than Mach 1.0, you're floating in your harness straps, and everything not tied down in the cockpit is floating all around you.
And that's all I have to say about that ! (: Hmarin (talk) 08:13, 18 February 2010 (UTC)
- Yes, I do believe I'd misunderstood you. While an unloaded extension is a very valuable maneuver which can be used in a variety of situations, I was referring to the maneuver known specificly as a "high Yo-Yo defense." In this maneuver, as soon as the attacker rolls nose off the pilot unloads by relaxing the turn. If the pilot can do this while maintaining the same angle of bank, the maneuver will be very difficult to spot. This will not only cause an increase in speed, but also in turn radius. When the attacker completes the maneuver in a wider circle than expected, he may be surprized when the defender suddenly initiates a hard turn into the attack, and just may overshoot. If not, the defender has at least acquired a better defensive position.
- I'm glad you like the history. According to RAF Squadron Leader K. G. Holland, "The Yo-Yo is very difficult to explain. It was first perfected by the well-known Chinese fighter pilot Yo-Yo Noritake. He also found it very difficult to explain, being quite devoid of English." My plan is to create an entire article about the maneuver, and then provide a link to the section here, like is done with the split-s or scissors. This article here provides just a basic overview, so that when a reader goes to the Scissors or the high Yo-Yo article they will already have the gist of it. There's just too much info to detail in one article.
- The above quote by Holland from the book Fighter Combat was, I believe, meant as a joke. There was no Chinese fighter pilot named "Yo-Yo Noritake." The term "yo-yo" merely describes the "up-down" nature of these maneuvers. Aerocapture (talk) 15:38, 29 March 2014 (UTC)
- It is quite possible that RAF Squadron Leader K G Holland was making a joke, but I have no way to determine that for sure. That's why I changed the words "created by" to "credited to." Zaereth (talk) 18:07, 29 March 2014 (UTC)
- My time is very limited, so if you'd like to start an article yourself it'd be appreciated. Most Wikipedia articles could use a little expert attention. Just click on the red link above and have at it. I just wanted to be careful when talking about "defeating turn rate with roll rate" that we make it clear that the aircraft is still limited by its tactical egg. Again, thanks for your help, for this kind of discussion is very useful in helping to craft clear language. Zaereth (talk) 18:10, 18 February 2010 (UTC)
- Per your suggestion, I think I've helped clarify the out-of-plane section by by simply changing it to read: "using roll rate instead of turn rate to set the proper pursuit curve." Does that seem to read better? Zaereth (talk) 19:59, 18 February 2010 (UTC)
Dive and zoom
[edit]...also known as boom and zoom, or zoom and boom. The article needs to discuss this tactic, wherein the fighter trades altitude for speed to attack a lower-altitude enemy, and immediately after contact climbs once again to regain altitude. Make one pass, do as much damage as possible, and get away. Repeat as necessary. Binksternet (talk) 00:46, 10 February 2010 (UTC)
- Absolutely. I'm still working on expanding this article, and my time is very limited, but any help is appreciated. I'll go through my sources as soon as I can. So far I've been working on the basics. Many maneuvers are used more in training than in combat, but there are many useful maneuvers still not listed her and a dive attack followed by a zoom climb is definitely one. Others include spiral dives, sandwich turns, wingovers, etc ... Zaereth (talk) 02:01, 10 February 2010 (UTC)
- I've added this info. Since positioning is improtant for setting up such an attack, I've expanded, and corrected that section as well. I've also expanded the Immelmann and split-s sections, since this is the type of attack which those are used to set up. I'll try to get a few more maneuvers listed, and maybe a section on out-of-plane maneuvers before I'll consider myself finished here. Hope that helped. Zaereth (talk) 21:08, 11 February 2010 (UTC)
Article problems with time frame and history
[edit]This article should be divided into fighter maneuvers per era, as speed and weaponry were vastly different in WWI, WWII, Korea, Vietnam and beyond. What was "basic" in 1918 was outdated by 1940, and what was basic by 1945 was nonsense in terms of jet fighters. During modern times when gunfighter jets were absent from air battles, missile attack and defense maneuvers dominated, and the dogfight was not relevant. The article says nothing of this! Just about all of it is based on 1985 thought, but this fact is not stated at the outset. Significant historical originators of fighter tactics such as Oswald Boelcke, Max Immelmann, Mick Mannock, Jimmy Thach, Eddie Rickenbacker, Raoul Lufbery, Claire Chennault, Erich Hartmann and John Boyd (military strategist) are not mentioned at all. The current relationship to fighter maneuverability and late model fighters is not touched upon—for instance, the continued emphasis that Russian Sukhoi airplane designers give to superagility in dogfights is absent. If no improvement to the article is considered, it should be moved to Basic fighter maneuvers of the 1980s. Binksternet (talk) 21:46, 19 February 2010 (UTC)
- That doesn't make much sense to me, since the article seems to convey no specifics. Concepts such as pursuit curves are basic to the very geometry of BFM. Consider that BFM refers to dogfighting maneuvers specificlly, regardless of era or plane type. The possible variations are impossible to cover in one article without turning it into an entire book. I'm no historian, but I personally see this as a strictly technical article. So I'll just leave the technical stuff and let others do what they want with it. Zaereth (talk) 22:44, 19 February 2010 (UTC)
- By the way. If you're interested in historical context, check out the book, Fighter combat: tactics and maneuvering. Its full of lots of wonderful quotes, like the one about WWII pilot Yo-Yo Noritake or this one: "The Immelmann Turn was very successful ... But later, when more powerful engines became available, it was a dangerous move, for the lower pilot could climb after the Fokker and attack when it hung almost motionless in the vertical position, not under full controll, and presented an easy shot." --Air Vice Marshal J.E. "Johnnie" Johnson, RAF.
- Or this one: "Habit brought my head swiveling around to look behind me. I was just in time to see a Fokke-Wulf bouncing, nose twinkling from the .30 calibers. My left hand slammed forward on the throttle, my right hand hauled back on the stick, my heart went to the top of my head and the Thunderbolt leapt upward. I racked the Jug into a tight left climbing turn, staying just above and in front of the pursuing Fokke-Wulf.... To get any strikes on me, the [German] had to turn inside me, and then haul his nose up steeply to place the bullets ahead of me. The Fokke-Wulf just didn't have it. At 8,000 feet he stalled out while the Thunderbolt roared smoothly; I kicked over into a roll and locked onto his tail." -- Major Robert S. Johnson.
- And: "Everything in the air beneath me, especially the one seater ... is lost, for it can not shoot to the rear." --Baron Manfred von Richthoven
- As for me though, I'd rather see the High Yo-Yo article expanded to include the history, it's use in modern combat, etc. The same with the Immelmann, etc... But I don't think an article with such a broad overview is the place for it. Zaereth (talk) 02:18, 20 February 2010 (UTC)
- Also, if it's more modern concepts you're looking for, the U.S Navy's flight instruction manual is from 2006. I don't think that the physics has changed much in the last 100 years. If, however, you do want to classify these maneuvers as stricly "1980s," then I'd ask you to provide sources to back up your theory, so as to avoid any synthesis. Zaereth (talk) 20:15, 20 February 2010 (UTC)
- It might be worth mentioning here also that once a pilot finishes BFM training, if lucky, they'll move on to ACM training, or specificly, DACT (dissimilar air combat training). This is where pilots learn to put their new found skills to use. This includes things such as one against one, one against two, one against many, two against one, two against many, etc... This is where BFM are used to construct section (two plane) and division (four plane) maneuvers, such as the Thatch weave, loose deuce, finger four, and others. I think a whole separate article could easily be constructed about that. Zaereth (talk) 04:50, 22 February 2010 (UTC)
Wow, I must've been in a bad mood the day I wrote the above. My apologies if I sounded gruff. I have added what historicsl context I could find, but also tried to keep it specific to not only the basic stuff, but to the maneuvers themselves. I can't say I'm ever really done with an article, but much of the advanced stuff, I believe, belongs in the ACM article, which I will probably start expanding within the next year. (I work slowly and sporadically, whenever the fancy hits me.) Zaereth (talk) 19:42, 7 August 2012 (UTC)
New tags
[edit]The single-source tag added today seems a little wrong. I used three different sources when working on this article; not just one. Zaereth (talk) 16:20, 18 June 2010 (UTC)
- On reflection, that was the wrong tag. Now I look at the references - I have my concerns over the tpub.com one. Is there an author for it. It looks like it was lifted form some other publication. GraemeLeggett (talk) 18:01, 18 June 2010 (UTC)
- If you click on the link that says "up," it'll take you to the table of contents. The author is the United States Navy. It's their flight instruction manual, which is public domain.
- These are the best sources that I have on the subject, although I'm always open for more. Zaereth (talk) 18:12, 18 June 2010 (UTC)
- All the citations on different manoevres from the tpub.com reference go to the same page. They need to go to the page where the content is. GraemeLeggett (talk) 21:37, 18 June 2010 (UTC)
- Certainly. I can reference each one to the page it came from, but won't have the time until next week. I'm rather busy in real life right now. I guess I was a bit lazy in that dept. I'll put some page numbers on the ones from Shaw's book as well. Hope it can wait a few days. Have a good weekend. Zaereth (talk) 22:31, 18 June 2010 (UTC)
Combat Spread is a formation, not a maneuver.
[edit]As titled (153.219.41.227 (talk) 14:30, 15 January 2015 (UTC))
- The combat spread begins as a formation, but is quite a bit more dynamic than that during an engagement. It provides the basic building block for loose-deuce maneuvering or finger-four maneuvers, and is typically the first maneuver taught to pilots. Zaereth (talk) 21:00, 15 January 2015 (UTC)
External links modified
[edit]Hello fellow Wikipedians,
I have just modified 19 external links on Basic fighter maneuvers. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:
- Added archive https://web.archive.org/web/20120913130302/http://navyflightmanuals.tpub.com/P-1222/P-12220043.htm to http://navyflightmanuals.tpub.com/P-1222/P-12220043.htm
- Added archive https://web.archive.org/web/20131229023902/http://navyflightmanuals.tpub.com:80/P-1222/P-12220012.htm to http://navyflightmanuals.tpub.com/P-1222/P-12220012.htm
- Added archive https://web.archive.org/web/20140318134651/http://navyflightmanuals.tpub.com/P-821/P-8210201.htm to http://navyflightmanuals.tpub.com/P-821/P-8210201.htm
- Added archive https://web.archive.org/web/20110605043651/http://www.tpub.com/content/aviation2/P-821/P-8210199.htm to http://www.tpub.com/content/aviation2/P-821/P-8210199.htm
- Added archive https://web.archive.org/web/20110605022122/http://www.tpub.com/content/aviation2/P-821/P-8210200.htm to http://www.tpub.com/content/aviation2/P-821/P-8210200.htm
- Added archive https://web.archive.org/web/20131229023953/http://navyflightmanuals.tpub.com:80/P-1222/P-12220018.htm to http://navyflightmanuals.tpub.com/P-1222/P-12220018.htm
- Added archive https://web.archive.org/web/20110605055455/http://www.tpub.com/content/aviation2/P-821/P-8210205.htm to http://www.tpub.com/content/aviation2/P-821/P-8210205.htm
- Added archive https://web.archive.org/web/20111003154857/http://www.tpub.com:80/content/aviation2/P-821/P-8210207.htm to http://www.tpub.com/content/aviation2/P-821/P-8210207.htm
- Added archive https://web.archive.org/web/20110605061327/http://www.tpub.com/content/aviation2/P-821/P-8210196.htm to http://www.tpub.com/content/aviation2/P-821/P-8210196.htm
- Added archive https://web.archive.org/web/20101223220947/http://www.tpub.com:80/content/aviation2/P-821/P-8210247.htm to http://www.tpub.com/content/aviation2/P-821/P-8210247.htm
- Added archive https://web.archive.org/web/20110605014133/http://www.tpub.com/content/aviation2/P-821/P-8210249.htm to http://www.tpub.com/content/aviation2/P-821/P-8210249.htm
- Added archive https://web.archive.org/web/20111003154902/http://www.tpub.com:80/content/aviation2/P-821/P-8210210.htm to http://www.tpub.com/content/aviation2/P-821/P-8210210.htm
- Added archive https://web.archive.org/web/20111003154748/http://www.tpub.com:80/content/aviation2/P-821/P-8210212.htm to http://www.tpub.com/content/aviation2/P-821/P-8210212.htm
- Added
{{dead link}}
tag to http://www.tpub.com/content/aviation2/P-821/P-8210257.htm - Added archive https://web.archive.org/web/20160304041247/http://navyflightmanuals.tpub.com/P-1222/P-12220049.htm to http://navyflightmanuals.tpub.com/P-1222/P-12220049.htm
- Added
{{dead link}}
tag to http://www.tpub.com/content/aviation2/P-821/P-8210258.htm - Added
{{dead link}}
tag to http://www.tpub.com/content/aviation2/P-821/P-8210226.htm - Added archive https://web.archive.org/web/20110605033214/http://www.tpub.com/content/aviation2/P-821/P-8210248.htm to http://www.tpub.com/content/aviation2/P-821/P-8210248.htm
- Added
{{dead link}}
tag to http://www.tpub.com/content/aviation2/P-821/P-8210262.htm - Added archive https://web.archive.org/web/20110605055428/http://www.tpub.com/content/aviation2/P-821/P-8210251.htm to http://www.tpub.com/content/aviation2/P-821/P-8210251.htm
- Added
{{dead link}}
tag to http://www.tpub.com/content/aviation2/P-821/P-8210252.htm - Added
{{dead link}}
tag to http://www.tpub.com/content/aviation2/P-821/P-8210253.htm - Added
{{dead link}}
tag to http://www.tpub.com/content/aviation2/P-821/P-8210264.htm - Added archive https://web.archive.org/web/20090827001743/http://www.tpub.com:80/content/aviation2/P-1222/P-12220045.htm to http://www.tpub.com/content/aviation2/P-1222/P-12220045.htm
- Added archive https://web.archive.org/web/20090828025049/http://www.tpub.com:80/content/aviation2/P-1222/P-12220044.htm to http://www.tpub.com/content/aviation2/P-1222/P-12220044.htm
- Added archive https://web.archive.org/web/20100515103959/http://www.tpub.com:80/content/aviation2/P-821/index.htm to http://www.tpub.com/content/aviation2/P-821/index.htm
When you have finished reviewing my changes, please set the checked parameter below to true or failed to let others know (documentation at {{Sourcecheck}}
).
This message was posted before February 2018. After February 2018, "External links modified" talk page sections are no longer generated or monitored by InternetArchiveBot. No special action is required regarding these talk page notices, other than regular verification using the archive tool instructions below. Editors have permission to delete these "External links modified" talk page sections if they want to de-clutter talk pages, but see the RfC before doing mass systematic removals. This message is updated dynamically through the template {{source check}}
(last update: 5 June 2024).
- If you have discovered URLs which were erroneously considered dead by the bot, you can report them with this tool.
- If you found an error with any archives or the URLs themselves, you can fix them with this tool.
Cheers.—InternetArchiveBot (Report bug) 01:14, 28 October 2016 (UTC)
External links modified
[edit]Hello fellow Wikipedians,
I have just modified 2 external links on Basic fighter maneuvers. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:
- Added archive https://web.archive.org/web/20110805075929/http://www.tpub.com/content/aviation2/P-821/P-8210193.htm to http://www.tpub.com/content/aviation2/P-821/P-8210193.htm
- Added archive https://web.archive.org/web/20090831125643/http://www.352ndfightergroup.com:80/virtual/protac/acm/maneuver.html to http://www.352ndfightergroup.com/virtual/protac/acm/maneuver.html
When you have finished reviewing my changes, please set the checked parameter below to true or failed to let others know (documentation at {{Sourcecheck}}
).
This message was posted before February 2018. After February 2018, "External links modified" talk page sections are no longer generated or monitored by InternetArchiveBot. No special action is required regarding these talk page notices, other than regular verification using the archive tool instructions below. Editors have permission to delete these "External links modified" talk page sections if they want to de-clutter talk pages, but see the RfC before doing mass systematic removals. This message is updated dynamically through the template {{source check}}
(last update: 5 June 2024).
- If you have discovered URLs which were erroneously considered dead by the bot, you can report them with this tool.
- If you found an error with any archives or the URLs themselves, you can fix them with this tool.
Cheers.—InternetArchiveBot (Report bug) 08:19, 30 November 2016 (UTC)
Symmetry violation
[edit]In both types of flow, the closest possible merge is desirable to keep the enemy at an angular disadvantage.
They can't both be minimizing the same shared parameter, each to their own separate advantage. — MaxEnt 14:52, 6 April 2019 (UTC)
- Hi MaxEnt. Not sure exactly what you're saying. That's found in the source. If I'm flying straight at you, and you try and go wide so you can get around me, you've lost the angular advantage and given it to me. If, however, we both head straight for each other, we're both in a neutral position with neither having the advantage (both at a disadvantage). The closer we merge, the less chance that you will be able to turn at the last second and put a shot into my side. More importantly, if we merge wide, during one-circle flow our fighter's minimum turn-radius won't count for much (the wider your merge; the more the advantage goes to the plane on the outside of the turn), while in two-circle flow, the craft's maximum turn-rate won't be of much help either (upon completing your turn, we'll still be too wide and will both have to straighten out to compensate). The idea is to start out with both flight paths as closely in sync as possible. Zaereth (talk) 17:08, 8 April 2019 (UTC)
Specific energy and Lufbery
[edit]The text being added to this article has for the most part been incorrect. There is no need to remove any sourced info, epecially if the source is the US Naval Air Training Command, which by all accounts are experts in this field. "Energy package" is a common term used in this field. It's jargon which is why it's explained to the readers, but it's a term they will encounter when reading the sources and should be explained here.
https://web.archive.org/web/20140318134651/http://navyflightmanuals.tpub.com/P-821/P-8210201.htm
I'll quote the text, in case it's too hard to click the link, "Total Energy (TE) is the combination of the aircraft's Potential Energy (PE)(function of aircraft altitude) and Kinetic Energy (KE)(function of airspeed). TE will be referred to as your "energy package" and will vary according to your situation.... The aircrew that best manages its energy package often gains the tactical advantage. Although determining the total energy advantage for a tactical scenario is difficult because of possible speed differences between aircraft, total energy remains a vital factor for determining relative advantage. As you gain experience in BFM, you will soon learn to judge the energy package of your adversary."
This info is well cited and there for anyone to see. So is the info on the Lufbery. It's right there in the source, and is one of the first things they teach you in flight school. The Lufbery Circle is not a basic fighter maneuver, but rather belongs in the ACM article. It's basically corralling the wagons and hoping the enemy will leave before you run out of fuel. Zaereth (talk) 23:55, 15 March 2020 (UTC)