# Aircraft turns from headwind to tailwind - loss of IAS? **URL:** \ **Category:** Factual Questions\ **Created:** [December 23, 2009, 10:59pm UTC](https://boards.straightdope.com/t/aircraft-turns-from-headwind-to-tailwind-loss-of-ias/522386 "2009-12-23T22:59:27Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Magiver](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Magiver](https://boards.straightdope.com/u/Magiver)\ **Post date:** [December 25, 2009, 4:56am UTC](https://boards.straightdope.com/t/aircraft-turns-from-headwind-to-tailwind-loss-of-ias/522386/21 "2009-12-25T04:56:27Z")
[quote=“1920s Style “Death Ray”, post:14, topic:522386”] I spend most of my working life flying at low level in strong steady winds over water and have never had any loss of airspeed turning downwind that was any different from the loss of airspeed in a turn in nil wind [/QUOTE] If you’re flying close to stall speed and the headwind is substantial than you can get into trouble turning into a tailwind. Consider a small plane flying at 60 knots into a 60 knot head wind. The plane is virtually a helicopter at this point with no forward momentum and can almost rotate on it’s axis. There is no aircraft enertia involved if the groundspeed is reduced to almost nothing. Do this in a mountainous region where the wind whips all around and you could find yourself turning into a continuous headwind and then blam, it’s a tailwind. It’s a variation of a micro-burst. We know it’s possible for an airliner to fall out of the sky in a micro-burst because it’s happened. I can see this happening in mountains because you’re flying a corkscrew pattern trying to get down to the runway. Mountain flying has it’s own set of skills that need to be learned. ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [December 25, 2009, 5:19am UTC](https://boards.straightdope.com/t/aircraft-turns-from-headwind-to-tailwind-loss-of-ias/522386/22 "2009-12-25T05:19:44Z")
Something is slouching towards Betheleham as we speak… ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [December 25, 2009, 5:23am UTC](https://boards.straightdope.com/t/aircraft-turns-from-headwind-to-tailwind-loss-of-ias/522386/23 "2009-12-25T05:23:01Z")
> [@Magiver](#): > > Consider a small plane flying at 60 knots into a 60 knot head wind. The plane is virtually a helicopter at this point with no forward momentum and can almost rotate on it’s axis. There is no aircraft enertia involved if the groundspeed is reduced to almost nothing. This would be valid if there were something special about the earth-based frame of reference. But there isn’t - all inertial frames of reference are equivalent. ---
**Author:** ![Magiver](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Magiver](https://boards.straightdope.com/u/Magiver)\ **Post date:** [December 25, 2009, 6:32am UTC](https://boards.straightdope.com/t/aircraft-turns-from-headwind-to-tailwind-loss-of-ias/522386/24 "2009-12-25T06:32:19Z")
> [@Xema](#): > > This would be valid if there were something special about the earth-based frame of reference. But there isn’t - all inertial frames of reference are equivalent. there’s no inertia associated with a plane flying at 60 knots into a 60 knot headwind. The plane has no forward momentum. It is very possible to get into trouble flying in mountains because you’re restricted by terrain from wandering about. You are also subject to winds that change direction. To fly into an airport like Middlesboro KY it is a virtual fishbowl requiring a corkscrew approach or an extraordinarily steep descent. It doesn’t take much to get into trouble in this situation. Combine a slow forward speed due to headwinds and a higher stall speed from cross-controlling and a shallow turn becomes an unrecoverable stall. ---
**Author:** ![Anne\_Elk](https://avatars.discourse-cdn.com/v4/letter/a/22d042/32.png) [@Anne\_Elk](https://boards.straightdope.com/u/Anne_Elk)\ **Post date:** [December 25, 2009, 12:52pm UTC](https://boards.straightdope.com/t/aircraft-turns-from-headwind-to-tailwind-loss-of-ias/522386/25 "2009-12-25T12:52:25Z")
Xema has it right. It’s the frame of reference. I have some gps tracks taken during a xc flight on a breezy day. While I was circling at a steady speed and bank angle during the flight, the track shows a corkscrew pattern as I drifted with the wind. The ground-speed increased and decreased the amount of the wind speed each time I turned 360 degrees. To a witness on the ground it would have looked like I was almost motionless heading into the wind and going very fast down-wind. The folks that think an aircraft’s airspeed is determined by which way the wind is blowing are still flying kites and are dangerous pilots. ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [December 25, 2009, 2:10pm UTC](https://boards.straightdope.com/t/aircraft-turns-from-headwind-to-tailwind-loss-of-ias/522386/26 "2009-12-25T14:10:59Z")
> [@Magiver](#): > > there’s no inertia associated with a plane flying at 60 knots into a 60 knot headwind. The plane has no forward momentum. Sure it does, relative to the medium it’s flying through. But you’re largely talk about windshear, visual illusions, and pilot incompetence. The downwind turn itself does not cause any loss of airspeed. You are correct that mountain flying needs to be taken seriously (in New Zealand you generally won’t get a job in the mountains without having done a specific mountain flying course) but all you do by focusing on the bogus downwind turn is to divert attention away from the real dangers and give pilots a false confidence when turning into wind even though the same weather conditions can catch you out in both cases. > [@yoyodyne](#): > > A plane is flying North at 200 kts IAS. There is no wind. The plane does a practically instantaneous course reversal. > > I believe the plane will continue moving North, slowing as the engines accelerate the plane Southward. It will pass through 0 kts IAS on its way to 200 kts South, losing altitude in the process. I will humour you and **ElvisL1ves** for a minute. Consider three cases, in all three an aircraft travels north at 200 KIAS and in a blinding failure of physics conducts an instantaneous 180 degree turn. In each case we will apply different wind conditions, a turn from a strong headwind to a strong tailwind, a turn in nil wind, and a turn from a strong tailwind to a strong headwind. **Case 1, turn from strong headwind to tailwind of 100 knots.** The aircraft is initially flying into a steady 100 knot wind. It has an airspeed of 200 KIAS and a ground speed of 100 knots. It instantaneously turns through 180 degrees and then has a ground speed of negative 100 knots (backward) and an airspeed of negative 200 knots (also backward). **It then has to increase airspeed by 400 knots to regain its initial airspeed of 200 KIAS, this results in a final ground speed of 300 knots (also a change of 400 knots.)** **Case 2, nil wind.** The aircraft starts with an airspeed of 200 KIAS and a ground speed of 200 knots. It instantaneously turns through 180 degrees and then has a ground speed of negative 200 knots (backward) and an airspeed of negative 200 knots (also backward). **It then has to increase airspeed by 400 knots to regain its initial airspeed of 200 KIAS, this results in a final ground speed of 200 knots (also a change of 400 knots.)** **Case 3, turn from strong tail wind to head wind of 100 knots.** The aircraft starts flying with a steady 100 knot tailwind, it has an airspeed of 200 KIAS and a ground speed of 300 knots. It instantaneously turns through 180 degrees and then has a ground speed of negative 300 knots (backward) and an airspeed of negative 200 knots (also backward). **It then has to increase airspeed by 400 knots to maintain its initial airspeed of 200 KIAS, this results in a final ground speed of 100 knots (also a change of 400 knots.)** In all three of these cases the aircraft must accelerate the exact same amount in the new direction to achieve the initial conditions. The movement of the wind over the ground has absolutely no effect on the requirement for the aircraft to find 400 knots from somewhere. The change of 400 knots is required in both airspeed and ground speed in all cases. **If the pilot couldn’t see the ground in each of these cases they’d have no idea which of the scenarios they were in.** Conclusion, although the experiment itself is not valid because it violates the way aircraft fly, it still proves my point, not yours. ---
**Author:** ![Hi\_Medlo](https://avatars.discourse-cdn.com/v4/letter/h/a183cd/32.png) [@Hi\_Medlo](https://boards.straightdope.com/u/Hi_Medlo)\ **Post date:** [December 25, 2009, 3:36pm UTC](https://boards.straightdope.com/t/aircraft-turns-from-headwind-to-tailwind-loss-of-ias/522386/27 "2009-12-25T15:36:33Z")
I warned you guys… ---
**Author:** ![yoyodyne](https://avatars.discourse-cdn.com/v4/letter/y/a9a28c/32.png) [@yoyodyne](https://boards.straightdope.com/u/yoyodyne)\ **Post date:** [December 25, 2009, 6:37pm UTC](https://boards.straightdope.com/t/aircraft-turns-from-headwind-to-tailwind-loss-of-ias/522386/28 "2009-12-25T18:37:43Z")
[quote=“1920s Style “Death Ray”, post:26, topic:522386”] **Case 2, nil wind.** The aircraft starts with an airspeed of 200 KIAS and a ground speed of 200 knots. It instantaneously turns through 180 degrees and then has a ground speed of negative 200 knots (backward) and an airspeed of negative 200 knots (also backward). **It then has to increase airspeed by 400 knots to regain its initial airspeed of 200 KIAS, this results in a final ground speed of 200 knots (also a change of 400 knots.)** [/QUOTE] I didn’t say a thing about wind or ground speed, I know a plane can’t instantly reverse course, and I wasn’t trying to prove a point. Considering just this case, how long might it take for the plane to go from negative 200 KIAS to 200 KIAS and what would be happening to it while it did so. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [December 26, 2009, 1:09am UTC](https://boards.straightdope.com/t/aircraft-turns-from-headwind-to-tailwind-loss-of-ias/522386/29 "2009-12-26T01:09:57Z")
> [@yoyodyne](#): > > how long might it take for the plane to go from negative 200 KIAS to 200 KIAS and what would be happening to it while it did so. It would take a minimum of about 10 to 15 seconds; the plane would be in a steeply banked turn, every part of which would feel the same regardless of what wind was (or wasn’t) blowing. ---
**Author:** ![GusNSpot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gusnspot/32/436_2.png) [@GusNSpot](https://boards.straightdope.com/u/GusNSpot)\ **Post date:** [December 26, 2009, 1:35am UTC](https://boards.straightdope.com/t/aircraft-turns-from-headwind-to-tailwind-loss-of-ias/522386/30 "2009-12-26T01:35:22Z")
Mass. gentlemen, never forget the mass. Middle to big airplanes over open water, cool. (how much time less than 3 wingspans from the surface?) Little planes and **helicopopters** in hills and varying wind conditions, good, how much? Fly instruments with no ground track sight or information and then see the track later and learn. “good” Points to remember: Object in motion tends to stay in same motion. ( More mass = more the mass wants to do this.) Ground reference needs to be learned and we all were taught it to a **small** degree. Now go fly total ground reference with no flight instrumentation. In a 700 Lbs, light aircraft. Then in a Cessna 310 . (remember, no flight instruments, only ground reference.) Do this at 500 feet and at 5000 feet. Now, if some fool will let you do this, do it in an airliner class aircraft. Survive all this? Now you know a little bit. Now go fly in the mountains in the spring. Survive that? Now you know more but not enough. Now go get taught how to fly pipeline patrol in underpowered small aircraft. ( 1- to 7 wingspans above the ground all day in all Wx and terrain.)Then go fly a C-182 on the same routes and field systems. Then a C-310. Do not do it on your own, Get an old pelican who has done it for thousands of hours to teach you. After 3-4 thousand hours of this in all weather and wind conditions you will know just enough to laugh at most of this physics and tech talk in this thread about this accident and the simplistic question from a questionable government source. Human pilots, even the best trained airline pilots can’t fly perfect. Not even the auto pilots when within 2 wing spans of the ground other than in a straight line. Remember the mass. > [@](#): > > The aircraft was on a private flight from Gloucestershire Airport in the UK, to Kilrush Airfield, Co. Kildare, Ireland. The last radar contact was observed at 11.26 hrs with the aircraft on a westerly heading at an altitude of 3,300 ft in the vicinity of Glenmacnass Waterfall, northeast of Tonelagee Mt, Co. Wicklow. Weather conditions at the time were difficult, with strong winds, low cloud and poor visibility. The aircraft was found, impacted into boggy terrain, near the summit of Corriebracks Mt. in Co. Wicklow. The four occupants were fatally injured. > ::: snippy::: > the Pilot was the victim of a personal assault by a group of five youths in an unprovoked attack. The Police report indicated that during the attack he received a blow to the back of his head and another to the middle of his back. There were no visible injuries, and as far as they were aware, medical attention was not sought by the Pilot. The Avon and Somerset Constabulary report states that he was suffering from shock. > Another pilot of the syndicate refuelled G-BGTJ to capacity with 143 > :::: snippy ::: > The last radar contact was observed at 11.26 hrs with the aircraft on a westerly heading at an altitude of 3,300 ft in the vicinity of Glenmacnass Waterfall, Northeast of Tonelagee Mt, Co Wicklow. Weather conditions at the time of the accident were poor, with strong winds gusting in excess of 50 kts, poor visibility and rain. The aircraft impacted into boggy terrain southeast of the summit of Corriebracks Mt at an altitude of 1,500 ft AMSL5 ( > ::: snippy :::: > Witness A (a pilot himself) recalls hearing a single-engine aircraft ‘going over his house on an easterly direction under considerable power’. The witness’s house was situated at Boleybeg, near Brannockstown, Co. Kildare, 8 miles northeast of Kilrush, and 3 miles North of the direct track the aircraft would have taken to Kilrush. He could not see the aircraft due to the low cloud, and he estimated the cloudbase to be approximately 500 ft above the ground. He heard no other aircraft in the area that day. > A second witness, Witness B, located at her house 1 mile to the east of Corriebracks Mt. stated she saw the aircraft ‘at low level, in and out of cloud’ heading in a southerly direction to the east of the summit. Neither Witness could recall the time the aircraft passed their location. The exact time of impact could not be established. However considering the last recorded radar contact, position of witnesses, and the location of the accident site, it is probable that the aircraft was airborne for at least 20 minutes after the last recorded radar contact at 11.26 hrs. > ::: snippy :::: > Witness A (a pilot himself) recalls hearing a single-engine aircraft ‘going over his house on an easterly direction under considerable power’. The witness’s house was situated at Boleybeg, near Brannockstown, Co. Kildare, 8 miles northeast of Kilrush, and 3 miles North of the direct track the aircraft would have taken to Kilrush. He could not see the aircraft due to the low cloud, and he estimated the cloudbase to be approximately 500 ft above the ground. He heard no other aircraft in the area that day. > A second witness, Witness B, located at her house 1 mile to the east of Corriebracks Mt. stated she saw the aircraft ‘at low level, in and out of cloud’ heading in a southerly direction to the east of the summit. Neither Witness could recall the time the aircraft passed their location. The exact time of impact could not be established. However considering the last recorded radar contact, position of witnesses, and the location of the accident site, it is probable that the aircraft was airborne for at least 20 minutes after the last recorded radar contact at 11.26 hrs. > ::: snippy :::: > As far as I am concerned [the Pilot] held a PPL (A) with a night and an IMC Rating. I would describe him as a competent pilot, he was not afraid of flying in bad weather and I have flown with him in some pretty poor conditions. He was current with his instrument flying and he flew about 100 hours a year. He quite often flew to Kilrush. My opinion of the aircraft, which I have known at this airfield for about 30 years, is that the equipment it had was old and I suspect [the Pilot] was using a hand-held GPS.’ > ::: snippy ::: At this point I am laughing out loud. All this and less than 800 "hrs TT.. !!! Bawahahaha, physics need not be considered. He was running as fast as he could to his ‘crash and die’ location… ::: Sheesh ::: Okay, back to the facts ma’am !!! :::: ‘snerk’ > [@](#): > > The aircraft was fuelled to capacity the evening before the accident flight. The Pilot’s flight plan indicated that he estimated an endurance of 5 hours, which equates to full fuel tanks. This was confirmed by the pilot who refuelled the aircraft on the evening of 24 October 2008, the day before the accident flight. The fuel tank capacity is 50 US Gallons, which equates to 299 lbs of AVGAS 100LL (at a Specific Gravity of 0.718). An allowance of 5 lbs was made for taxi-out and run up of the engine. Calculation indicates a take-off weight of 2,447 lbs; the maximum take-off weight is 2,450 lbs. > > phenomenon is found when strong winds pass over mountainous terrain, producing strong up and down currents, the effect of which may extend well above ground level and many miles downwind of the range. Also, on the lee side of the mountain, rotor cloud may form producing severe turbulence (Figure No. 2). The area of downdraught can be quite extensive and vertical air movements exceeding **1,000 ft/min have been encountered by glider pilots in this mountain range**. (Bolding mine)(b) Probable Cause > That the aircraft entered an aerodynamic stall, close to terrain, recovery from which was not possible in the height available. > (c) Contributory Factors > > 1. The aircraft probably turned downwind prior to impact, which led to a significant loss of airspeed. > 2. The aircraft was operating in turbulent, windy, and gusty conditions with significant downdraughts. > 3. The aircraft was manoeuvring at low level with a low margin of terrain clearance. > 4. A probable loss of situational awareness in the final stage of the flight, and flew towards high ground. > 5. Inadequate flight planning contributed to the eventual loss of situational awareness. Item #1 is the only thing that even raises my eyebrows at all in the report. I really wonder how much flying experience the guberment person who made the statement in item # 1 has. Would be needed to know before I would even think his comment was to be considered. Everything else says the pilot was in way over his head and just looking to die that day. Back to flying pipeline patrol. Until you have done violent acrobatics, flown pipe or something very similar, all your opinions and facts about airplanes, moving air and coordinated turns and mass in same; without being distracted by really strange and scary visuals flooding your mind from what you see the ground doing, well no matter your understand of physics and aircraft flight, you are going to die betting your life on the math to save your ass. Altitude, airspeed and usually fuel, are your friends. Don’t come play down low and slow and mean until you give up on what you think you know and have someone teach you what really happens down there. 95% is you and your willingness to believe what you are taught. I have buried so many that thought the math and theory and laws of physics would keep them alive when they flouted the wisdom of the old pelicans… Do not let statements about impossible wind and aircraft abilities and maneuvers get you to thinking it has anything to do with the real world.. Some new pilot may read them and bet his life on your ill conceived arguments … Oh, sorry, forgot, this was SDMB and the real world never applies in here. No matter who it might hurt. :rolleyes: ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [December 26, 2009, 8:58am UTC](https://boards.straightdope.com/t/aircraft-turns-from-headwind-to-tailwind-loss-of-ias/522386/31 "2009-12-26T08:58:26Z")
> [@yoyodyne](#): > > I didn’t say a thing about wind or ground speed, I know a plane can’t instantly reverse course, and I wasn’t trying to prove a point. > > Considering just this case, how long might it take for the plane to go from negative 200 KIAS to 200 KIAS and what would be happening to it while it did so. It wouldn’t be flying, what’s your point? ---
**Author:** ![Anne\_Elk](https://avatars.discourse-cdn.com/v4/letter/a/22d042/32.png) [@Anne\_Elk](https://boards.straightdope.com/u/Anne_Elk)\ **Post date:** [December 26, 2009, 1:04pm UTC](https://boards.straightdope.com/t/aircraft-turns-from-headwind-to-tailwind-loss-of-ias/522386/32 "2009-12-26T13:04:12Z")
Thanks GusNSpot. Great post. I like reading these accident reports to learn from them, rather then the ground reach me and teach me. It’s a shame the writer of the report had to insert that glaring misconception. If only the crash pilot had checked the weather the day of the flight, he would have not flown into that scenario, (I would have been hiding under my bed) then he was basically flying low level IFR using a hand-held GPS, in severe mechanical turbulence. A Goggle Earth view of the crash site and surrounding terrain suggests that the aircraft was flown into a lee side rotor and virtually “slapped” to the ground. I hope I can learn enough from these reports, other pilots, and safe flying that I can evolve into a pelican like GusNSpot. ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [December 26, 2009, 2:28pm UTC](https://boards.straightdope.com/t/aircraft-turns-from-headwind-to-tailwind-loss-of-ias/522386/33 "2009-12-26T14:28:57Z")
> [@Anne\_Elk](#): > > Thanks GusNSpot. Great post. I like reading these accident reports to learn from them, rather then the ground reach me and teach me. But it’s so much more exciting to learn the lessons first hand! 😉 Seriously if more pilots _really_ learned something from these reports there’d be a lot more pilots, and a lot fewer reports. Unfortunately many, and I include myself, never really have the lessons drilled into their brain until they scare themselves doing something a bit silly. When I look back it’s remarkable how the rate at which I do silly things is inversely proportional to the number of hours in my log book. **GusNSpot** , you are correct, we learn a little bit about ground reference, but well, I don’t know about the training syllabus over there but ours (NZ) was pretty basic for that stuff, a bit of lowish flying (200’) and some constant radius turns around a point in a bit of wind, follow some paddock fences that sort of thing. But it’s just enough to learn that there is something to learn, not enough to learn how to do it properly. At the moment I’m a three-wingspan guy, the thing is, the bigger they make my wings, the higher they want me to fly them! I think you’d probably laugh if you ever saw how, for the want of a better term, _airline-like_ our low flying is. Anyway, I think there is one philosophy that should serve _any_ pilot well no matter what they do. Always ALWAYS have a plan B, and don’t hesitate to use it if you need to. ---
**Author:** ![GusNSpot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gusnspot/32/436_2.png) [@GusNSpot](https://boards.straightdope.com/u/GusNSpot)\ **Post date:** [December 26, 2009, 11:50pm UTC](https://boards.straightdope.com/t/aircraft-turns-from-headwind-to-tailwind-loss-of-ias/522386/34 "2009-12-26T23:50:25Z")
[quote=“1920s Style “Death Ray”, post:33, topic:522386”] But it’s so much more exciting to learn the lessons first hand! 😉 Seriously if more pilots _really_ learned something from these reports there’d be a lot more pilots, and a lot fewer reports. ::: snip ::: Anyway, I think there is one philosophy that should serve _any_ pilot well no matter what they do. Always ALWAYS have a plan B, and don’t hesitate to use it if you need to. [/QUOTE] Best said: This is correct. Just make sure it is a good plan… 😉 ---
**Author:** ![ElvisL1ves](https://avatars.discourse-cdn.com/v4/letter/e/5daacb/32.png) [@ElvisL1ves](https://boards.straightdope.com/u/ElvisL1ves)\ **Post date:** [December 28, 2009, 4:46pm UTC](https://boards.straightdope.com/t/aircraft-turns-from-headwind-to-tailwind-loss-of-ias/522386/35 "2009-12-28T16:46:38Z")
[quote=“1920s Style “Death Ray”, post:14, topic:522386”] This is not true. The extreme case of instantly yawing through 180 degrees violates all of the physics that governs how the aircraft flies in the first place, making the analogy irrelevant and the conclusion wrong. [/quote] Come on now. I said it was an extreme case, and those do have instructional value. Sometimes that instructional value is substantial, if, for instance as in this case, it allows one to separate transient from steady-state effects. > [@](#): > > Turning quickly loses you airspeed due to increased drag. But not immediately, due to inertia effects. Those transient effects will be smaller with slower rates of turn, until they’re unnoticeable for a normal airplane at normal rates of turn. But they’re there and can be measured. Really, this is just high-school physics stuff, and not the advanced class, either. ``` - Aerospace engineer and pilot ``` ---
**Author:** ![GusNSpot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gusnspot/32/436_2.png) [@GusNSpot](https://boards.straightdope.com/u/GusNSpot)\ **Post date:** [December 28, 2009, 6:26pm UTC](https://boards.straightdope.com/t/aircraft-turns-from-headwind-to-tailwind-loss-of-ias/522386/36 "2009-12-28T18:26:34Z")
> [@](#): > > But they’re there and can be measured. Really, this is just high-school physics stuff, and not the advanced class, either. Agreed ---- if it is kept in high school and there are no student pilots in the class. ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [December 29, 2009, 8:41am UTC](https://boards.straightdope.com/t/aircraft-turns-from-headwind-to-tailwind-loss-of-ias/522386/37 "2009-12-29T08:41:54Z")
> [@ElvisL1ves](#): > > Come on now. I said it was an extreme case, and those do have instructional value. Sometimes that instructional value is substantial, if, for instance as in this case, it allows one to separate transient from steady-state effects. So just to be clear, you believe that in _steady_ wind, unblemished by turbulence, when turning from into wind to down wind there will be a loss of IAS that is not present when turning from a tail wind to a head wind? ---
**Author:** ![ElvisL1ves](https://avatars.discourse-cdn.com/v4/letter/e/5daacb/32.png) [@ElvisL1ves](https://boards.straightdope.com/u/ElvisL1ves)\ **Post date:** [December 29, 2009, 5:20pm UTC](https://boards.straightdope.com/t/aircraft-turns-from-headwind-to-tailwind-loss-of-ias/522386/38 "2009-12-29T17:20:26Z")
Transiently, and slightly, but yes, certainly. And in the latter case, there will be a similar increase in IAS. It’s just F = m a, where a is relative to the gravitational field, IOW the _ground_. If that isn’t clear, try this: You’ve seen an IAS change in a headwind or tailwind gust, right? And it’s settled back down when the gust has been sustained for a few seconds, right? Well, an abrupt change in aircraft orientation can have the same effect on the wind relative to the aircraft as a gust does. If it didn’t, there would be no wind-shear accidents, since aircraft would never suddenly lose airspeed because of them. ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [December 29, 2009, 6:06pm UTC](https://boards.straightdope.com/t/aircraft-turns-from-headwind-to-tailwind-loss-of-ias/522386/39 "2009-12-29T18:06:06Z")
> [@ElvisL1ves](#): > > Transiently, and slightly, but yes, certainly. And in the latter case, there will be a similar increase in IAS. It’s just F = m a, where a is relative to the gravitational field, IOW the _ground_. > > If that isn’t clear, try this: You’ve seen an IAS change in a headwind or tailwind gust, right? And it’s settled back down when the gust has been sustained for a few seconds, right? Well, an abrupt change in aircraft orientation can have the same effect on the wind relative to the aircraft as a gust does. If it didn’t, there would be no wind-shear accidents, since aircraft would never suddenly lose airspeed because of them. Good grief… Are we talking prop planes that change direction almost totally by their aerodynamic surfaces interacting with the AIR…or are we talking about rocketships that happen to be in the atmosphere? Yeah, you are technically right at some measurable but very small level, but IMO this kinda stuff causes more problems than it solves. IMO you might as well bring quantum effects into the plane on a treadmill debate. ---
**Author:** ![hibernicus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hibernicus/32/2802_2.png) [@hibernicus](https://boards.straightdope.com/u/hibernicus)\ **Post date:** [December 29, 2009, 7:13pm UTC](https://boards.straightdope.com/t/aircraft-turns-from-headwind-to-tailwind-loss-of-ias/522386/40 "2009-12-29T19:13:32Z")
Just dropping back in to say I’ve been reading this discussion with great interest and have learned a lot. Thanks to everyone who’s taken the time and trouble to respond. [Previous page](https://boards.straightdope.com/t/aircraft-turns-from-headwind-to-tailwind-loss-of-ias/522386.md?page=1) [Next page](https://boards.straightdope.com/t/aircraft-turns-from-headwind-to-tailwind-loss-of-ias/522386.md?page=3)