# What will happen to THIS plane? **URL:** \ **Category:** Factual Questions\ **Created:** [December 13, 2005, 5:05pm UTC](https://boards.straightdope.com/t/what-will-happen-to-this-plane/335433 "2005-12-13T17:05:50Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![spingears](https://avatars.discourse-cdn.com/v4/letter/s/ebca7d/32.png) [@spingears](https://boards.straightdope.com/u/spingears)\ **Post date:** [December 13, 2005, 5:05pm UTC](https://boards.straightdope.com/t/what-will-happen-to-this-plane/335433/1 "2005-12-13T17:05:50Z")
A prior thread asks: [\*\*Will a plane on a treadmill take off? \*\*](http://boards.straightdope.com/sdmb/showthread.php?t=348452&page=7&pp=50) Now consider a plane flying at 28 mph into a head wind of 30 mph The pilot executes a roll of 180 deg. to the right. What is the speed of the plane after the turn? ---
**Author:** ![Inigo\_Montoya](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/inigo_montoya/32/124_2.png) [@Inigo\_Montoya](https://boards.straightdope.com/u/Inigo_Montoya)\ **Post date:** [December 13, 2005, 5:11pm UTC](https://boards.straightdope.com/t/what-will-happen-to-this-plane/335433/2 "2005-12-13T17:11:26Z")
Assuming it can turn around without getting upended when it gets to 90 degrees? How about: Air Speed -2 (and tumbling) & and Ground Speed 58 … for a few seconds at least. Unless there’s a naked air hostess on board. In which case one has to indirectly wonder whether or not the cat is actually still in the box. ---
**Author:** ![Finagle](https://avatars.discourse-cdn.com/v4/letter/f/b19c9b/32.png) [@Finagle](https://boards.straightdope.com/u/Finagle)\ **Post date:** [December 13, 2005, 5:26pm UTC](https://boards.straightdope.com/t/what-will-happen-to-this-plane/335433/3 "2005-12-13T17:26:24Z")
Assuming it’s a powered airplane and not a glider? I’m thinking 88 mph, more or less, based on the engine not having to fight against the wind. But there would be a transition period where you might lose lift and might have to dive to gain airspeed. But then again, I’m not a pilot, so I’m pretty much guessing here. ---
**Author:** ![ElvisL1ves](https://avatars.discourse-cdn.com/v4/letter/e/5daacb/32.png) [@ElvisL1ves](https://boards.straightdope.com/u/ElvisL1ves)\ **Post date:** [December 13, 2005, 5:28pm UTC](https://boards.straightdope.com/t/what-will-happen-to-this-plane/335433/4 "2005-12-13T17:28:25Z")
Nope. The plane can’t tell where the ground is, only the air. The airspeed will continue to be 28 mph, and the groundspeed will increase from -2 to 58. **Inigo** ’s mistaken view actually used to be common, and it took Jimmy Doolittle’s PhD thesis at MIT to explain the difference between airspeed and groundspeed to everyone’s satisfaction. Somehow the lack of airplane crashes caused by turning downwind, and the lack of pilots noticing any sudden loss of speed or control regardless of wind (except for gusts), didn’t do it. Please please please let this one stop sooner than the treadmill thread … ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [December 13, 2005, 5:30pm UTC](https://boards.straightdope.com/t/what-will-happen-to-this-plane/335433/5 "2005-12-13T17:30:59Z")
> [@spingears](#): > > …The pilot executes a roll of 180 deg. to the right. Did you mean to say that the plane ends up inverted? That’s what a 180-degree roll would do. Or did you mean to say that the plane does a 180-degree turn, so that it ends up headed in the opposite direction? ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [December 13, 2005, 5:33pm UTC](https://boards.straightdope.com/t/what-will-happen-to-this-plane/335433/6 "2005-12-13T17:33:18Z")
Is that 28 mph ground speed or airspeed? If it’s ground speed, then original airspeed is 28+30=58 mph. After you turn 180 degrees, your airspeed is still 58 mph (assuming same altitude, same engine power, etc). So ground speed is now 58+30=88 mph. ---
**Author:** ![Ethilrist](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ethilrist/32/4604_2.png) [@Ethilrist](https://boards.straightdope.com/u/Ethilrist)\ **Post date:** [December 13, 2005, 5:59pm UTC](https://boards.straightdope.com/t/what-will-happen-to-this-plane/335433/7 "2005-12-13T17:59:00Z")
> [@ElvisL1ves](#): > > Please please please let this one stop sooner than the treadmill thread … Well, given that people are still posting to that thread, there’s still room for five or six more pages of this. Yay! ---
**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 13, 2005, 8:00pm UTC](https://boards.straightdope.com/t/what-will-happen-to-this-plane/335433/8 "2005-12-13T20:00:57Z")
The difference is that this thread is on a real world topic that has a factual answer (that is that the airspeed of the aircraft remains the same throughout the turn.) ---
**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\ **Post date:** [December 13, 2005, 8:44pm UTC](https://boards.straightdope.com/t/what-will-happen-to-this-plane/335433/9 "2005-12-13T20:44:47Z")
> [@1920s Style "Death Ray"](#): > > The difference is that this thread is on a real world topic that has a factual answer… Ah, are you so certain? He doesn’t specify that he’s asking for airspeed, and he specifies a 180 degree _roll_, which to my understanding would simply invert the airplane. Yes, this one could run for pages. ---
**Author:** ![Ethilrist](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ethilrist/32/4604_2.png) [@Ethilrist](https://boards.straightdope.com/u/Ethilrist)\ **Post date:** [December 13, 2005, 8:52pm UTC](https://boards.straightdope.com/t/what-will-happen-to-this-plane/335433/10 "2005-12-13T20:52:05Z")
Good point. A 180 degree roll to the right means dropping the right wingtip and continuing that motion until the right wingtip is now the left wingtip. So, the speed would be about the same, probably increasing somewhat as the plane loses altitude and begins to dive due to loss of lift from the now-inverted wings… “you keep using that word… I do not think it means what you think it does…” ---
**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 13, 2005, 10:55pm UTC](https://boards.straightdope.com/t/what-will-happen-to-this-plane/335433/11 "2005-12-13T22:55:09Z")
Is it a magical , instantaneous turn or do the laws of flight, time and physics apply? I have never flown a perfectly symmetrical aircraft so I always lost some speed while inverted or doing a roll. I want to fly in this fixed wing aircraft that will carry me at 28 MPH. We are talking ‘gound effect’ aren’t we? Is it a standerd rate turn? Do I have to stay level? Shall we add lead and lag to the rotor blades of a rapidly decelerating helicopter in a strong tailwind while attempting to come to zero ground speed without facing the wind? We’ll get 10 pages out of this sucker yet… ---
**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 14, 2005, 1:56am UTC](https://boards.straightdope.com/t/what-will-happen-to-this-plane/335433/12 "2005-12-14T01:56:23Z")
> [@Ethilrist](#): > > Good point. A 180 degree roll to the right means dropping the right wingtip and continuing that motion until the right wingtip is now the left wingtip. > > So, the speed would be about the same, probably increasing somewhat as the plane loses altitude and begins to dive due to loss of lift from the now-inverted wings… > > “you keep using that word… I do not think it means what you think it does…” If, in fact, a 180 degree _roll_ really was meant then, assuming the pilot is skilled enough to keep the plane from losing altitude throughout and after the roll, the plane will end up inverted, flying level, with less airspeed then it had before. A higher angle of attack will be required to generate enough lift to make up for the less than optimal shape of the inverted wing. This will produce more drag, which will lower the airspeed. (Even aircraft such as a Pitts Special, which has a symmetrical wing section, fly slower inverted than upright.) Enjoy. ---
**Author:** ![drewbert](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/drewbert/32/15890_2.png) [@drewbert](https://boards.straightdope.com/u/drewbert)\ **Post date:** [December 14, 2005, 2:22am UTC](https://boards.straightdope.com/t/what-will-happen-to-this-plane/335433/13 "2005-12-14T02:22:13Z")
> [@Finagle](#): > > I’m thinking 88 mph Let’s not involve time travel, this thread will probably end up weird enough without it. ---
**Author:** ![spingears](https://avatars.discourse-cdn.com/v4/letter/s/ebca7d/32.png) [@spingears](https://boards.straightdope.com/u/spingears)\ **Post date:** [December 14, 2005, 3:11am UTC](https://boards.straightdope.com/t/what-will-happen-to-this-plane/335433/14 "2005-12-14T03:11:10Z")
> [@Xema](#): > > Did you mean to say that the plane ends up inverted? That’s what a 180-degree roll would do. No. Most readers interpreted what was posted. You read what was posted. > [@](#): > > Or did you mean to say that the plane does a 180-degree turn, so that it ends up headed in the opposite direction? YES My error in terminology. :smack: ---
**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 14, 2005, 3:20am UTC](https://boards.straightdope.com/t/what-will-happen-to-this-plane/335433/15 "2005-12-14T03:20:19Z")
> [@spingears](#): > > No. Most readers interpreted what was posted. You read what was posted. > > YES My error in terminology. :smack: In that case the planes air speed will remain the same. Though, to be picky, it actually decreases a little during the turn due to the extra wingloading. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [December 14, 2005, 3:21am UTC](https://boards.straightdope.com/t/what-will-happen-to-this-plane/335433/16 "2005-12-14T03:21:10Z")
The other (less important) point of clarification would be this: When you say “consider a plane flying at 28 mph into a head wind of 30 mph”, is 28mph the airspeed or the groundspeed? ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [December 14, 2005, 3:27am UTC](https://boards.straightdope.com/t/what-will-happen-to-this-plane/335433/17 "2005-12-14T03:27:17Z")
> [@1920s Style "Death Ray"](#): > > Though, to be picky, it actually decreases a little during the turn due to the extra wingloading. To be even pickier, that depends on certain assumptions, such as constant power and altitude. IOW, you could maintain constant airspeed by adding some power or sacrificing some altitude. ---
**Author:** ![Padeye](https://avatars.discourse-cdn.com/v4/letter/p/a9a28c/32.png) [@Padeye](https://boards.straightdope.com/u/Padeye)\ **Post date:** [December 14, 2005, 3:38am UTC](https://boards.straightdope.com/t/what-will-happen-to-this-plane/335433/18 "2005-12-14T03:38:34Z")
Airpspeed doesn’t neccessarily rise during a turn but the turn and higher G load means the stall speed increases so sometimes the pilot should increase airspeed if he wants to keep flying. ---
**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\ **Post date:** [December 14, 2005, 4:00am UTC](https://boards.straightdope.com/t/what-will-happen-to-this-plane/335433/19 "2005-12-14T04:00:29Z")
> [@spingears](#): > > No. Most readers interpreted what was posted. You read what was posted. Or maybe you just did a really bad job of wording the question? We still don’t know if you gave us airspeed or groundspeed, or if you were asking for airspeed or groundspeed. ---
**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 14, 2005, 6:47am UTC](https://boards.straightdope.com/t/what-will-happen-to-this-plane/335433/20 "2005-12-14T06:47:23Z")
> [@1920s Style "Death Ray"](#): > > If, in fact, a 180 degree _roll_ really was meant then, assuming the pilot is skilled enough to keep the plane from losing altitude throughout and after the roll, the plane will end up inverted, flying level, with less airspeed then it had before. A higher angle of attack will be required to generate enough lift to make up for the less than optimal shape of the inverted wing. This will produce more drag, which will lower the airspeed. (Even aircraft such as a Pitts Special, which has a symmetrical wing section, fly slower inverted than upright.) > > Enjoy. I knew you was gonna do dat so that is why I said, > [@](#): > > I have never flown a perfectly symmetrical aircraft so I always lost some speed while inverted Note the words ‘perfectly’ and ‘symmetrical’ and ‘aircraft’ ( not just airfoils ) nener, nener, nener, 😛😛 [Next page](https://boards.straightdope.com/t/what-will-happen-to-this-plane/335433.md?page=2)