Plane Stopped in Midair

"DM" wrote in message
...
Yesterday I saw a cargo jet (a major air express company) come to what
seemed like a dead stop in midair as it was making its ascent. After
about 20 - 30 seconds of hanging without dropping out of the sky, it
continued climbing and apparently did not crash. There's been nothing
about it in the local news but I've still been very concerned. Could
someone here explain how such a thing is possible?

Some details: the temperature was about 50 degrees F, the sky was
mostly clear, and the time was around 0645. I was traveling by car at
about 40 MPH on a street that is parallel to a regular flight path.
From this street it's common to see 3 or 4 planes per minute either
climbing or descending; the airport is about a mile or two away from
this particular street.

As I was moving relatively slowly compared to the how fast the jet
should have been moving, I noticed that I was gaining on it. I quickly
eyeballed the area for tall buildings and other geographical reference
points so I could be sure that I had a good perspective and wasn't
just "seeing things". The object was either not moving or it was
moving *very* slowly, and it was not a helicopter. For a few seconds I
was stopped at an intersection looking at this hanging plane and at
the people in the other cars around me. No one else seemed to be
paying any attention to it besides me.

The main reason this bothered me so much is because had the plane
fallen, it would have landed less than a half mile from where I and
about 30 other running cars were, in addition to several
warehouse-type buildings and auto repair garages, plus a 6 or 8 lane
freeway filled with morning traffic. Since the plane had just taken
off and was probably full of fuel, and was still low enough for its
markings to be readable from the ground, the crash probably would have
been extraordinarily disastrous.

I've done a lot of Googling to try to get an understanding of what I
saw and really haven't learned anything meaningful. I'm hoping someone
here can explain how a "regular" jet--versus a specialized military
jet--can apparently stop in midair and not drop from the sky. As a
daily traveler near a major metro airport, I'd really like to be
reassured that this is not a common occurrence.

Debbie

A pilot acquaintance of mine in Montana (Larry) flies a Super Cub to
inspect pipelines. Sometimes, when it's windy, he confounds drivers on
the Interstate by flying backwards above them. Not a problem; it's only
airspeed that matters.

John Lowry
Flight Physics

John T Lowry wrote:

A pilot acquaintance of mine in Montana (Larry) flies a Super Cub to
inspect pipelines. Sometimes, when it's windy, he confounds drivers on
the Interstate by flying backwards above them. Not a problem; it's only
airspeed that matters.

Hmm. Perhaps the idea of a nose-dragger originated when a tail-dragger
landed in a stiff wind.

- Andrew

One thing to add to what the other posters have said...
in a climbing turn a plane can easily appear to be
stationary for a short while. Not sure about the optics
of this but from my office area I can see planes taking
off from San Jose and starting the right turn for the
standard departure course, and this illusion is quite
common. Combine that with a strong headwind and the effect
of the size of the plane, and you could easily believe it
had stopped.

John

jharper aaatttt cisco dddooottt com wrote:

One thing to add to what the other posters have said...
in a climbing turn a plane can easily appear to be
stationary for a short while. Not sure about the optics
of this but from my office area I can see planes taking
off from San Jose and starting the right turn for the
standard departure course, and this illusion is quite
common. Combine that with a strong headwind and the effect
of the size of the plane, and you could easily believe it
had stopped.

John

yes, but as best as I could tell, the plane wasn't turning. It appeared
to be taking a straight path up, or trying to anyway.

Debbie

One other thing... it's essentially impossible to
stop a fixed-wing airplane in midair. (You can have
zero ground speed due to headwinds, but not zero
airspeed). If you try, the nose drops and it glides
towards the ground. If you try to stop that, it will
eventually perform an aerodynamic stall, which WILL
make the nose drop, but it still won't come to a halt.
About the only way to reach zero airspeed is to
pull the plane into a near-vertical climb. And even
then it reacts by dropping the nose and building
up some speed again (or if you are truly vertical,
it can fall tail-first and then it will at some point
snap into a more normal posture and then start
to fly nose-first again). It's fun to do though, in
the right kind of airplane - a small aerobatic one -
and with enough altitude.

John

jharper aaatttt cisco dddooottt com wrote:

One other thing... it's essentially impossible to
stop a fixed-wing airplane in midair.

yep, that's why I was expected the plane to fall from the sky.

(You can have
zero ground speed due to headwinds, but not zero
airspeed). If you try, the nose drops and it glides
towards the ground. If you try to stop that, it will
eventually perform an aerodynamic stall, which WILL
make the nose drop, but it still won't come to a halt.
About the only way to reach zero airspeed is to
pull the plane into a near-vertical climb. And even
then it reacts by dropping the nose and building
up some speed again (or if you are truly vertical,
it can fall tail-first and then it will at some point
snap into a more normal posture and then start
to fly nose-first again). It's fun to do though, in
the right kind of airplane - a small aerobatic one -
and with enough altitude.

John

if it had been an airshow kind of situation I wouldn't have given it a
thought but this was a commercial jet and it was over a populated area.
No fun...

Debbie

Debbie,

A large transport jet (such as a DC-10 operated by FedEx) can climb, lightly
loaded, at speeds around 150mph. This would be unusual (170-200mph is more
normal) but well short of impossible. It might have been a maintenance
flight, for instance.

Now, with that in mind let's apply a few more factors. First, windspeed.
Let's say the wind is blowing at 40mph. This would not be unusual for the
Northern half of the country this time of year. An airplane flying into that
wind would only need to move at 110mph relative to the ground. Windspeed can
vary strongly from the ground to the first few thousand feet as well, so you
might not have noticed the wondspeed on the ground. Now, you also mentioned
you were in the car going at least 40mph, so relative to you, the plane
would only appear to be moving at 70mph.

Last, you need to do a little trigonometry, I'm afraid. Imagine putting a
ladder up against the side of your house. The ladder goes up ten feet, and
at its base is set back perhaps three or four feet from the house. Now, when
you climb that ladder, you are traveling ten feet, but you only move forward
three or four. A similar thing is going on when you compare your speed in
the car to the plane's speed in the air. So we can reduce the difference to
perhaps 55 or 60mph.

What you perceive as speed is going to be based on changes in angle, in
other words, you expect to see the plane "pulling ahead of you" at a certain
rate. It turns out that the human eye is quite poor at judging small angles.
A speed difference of 60mph at a distance of half a mile is going to produce
very small angular changes, which your eye will not perceive well. So, even
though the plane is moving at sufficient speed to fly quite safely, to your
eye it will appear to be standing still.

I can assure you that even us pilots, who know all these things, still often
see the very same illusion you describe, especially with very large
airplanes. It's simply a combination of factors that produce an overwhelming
optical illusion.

-cwk.

C Kingsbury wrote:

Debbie,

A large transport jet (such as a DC-10 operated by FedEx) can climb, lightly
loaded, at speeds around 150mph. This would be unusual (170-200mph is more
normal) but well short of impossible. It might have been a maintenance
flight, for instance.

Now, with that in mind let's apply a few more factors. First, windspeed.
Let's say the wind is blowing at 40mph. This would not be unusual for the
Northern half of the country this time of year. An airplane flying into that
wind would only need to move at 110mph relative to the ground. Windspeed can
vary strongly from the ground to the first few thousand feet as well, so you
might not have noticed the wondspeed on the ground. Now, you also mentioned
you were in the car going at least 40mph, so relative to you, the plane
would only appear to be moving at 70mph.

Last, you need to do a little trigonometry, I'm afraid. Imagine putting a
ladder up against the side of your house. The ladder goes up ten feet, and
at its base is set back perhaps three or four feet from the house. Now, when
you climb that ladder, you are traveling ten feet, but you only move forward
three or four. A similar thing is going on when you compare your speed in
the car to the plane's speed in the air. So we can reduce the difference to
perhaps 55 or 60mph.

What you perceive as speed is going to be based on changes in angle, in
other words, you expect to see the plane "pulling ahead of you" at a certain
rate. It turns out that the human eye is quite poor at judging small angles.
A speed difference of 60mph at a distance of half a mile is going to produce
very small angular changes, which your eye will not perceive well. So, even
though the plane is moving at sufficient speed to fly quite safely, to your
eye it will appear to be standing still.

I can assure you that even us pilots, who know all these things, still often
see the very same illusion you describe, especially with very large
airplanes. It's simply a combination of factors that produce an overwhelming
optical illusion.

-cwk.

yes, I've imagined the whole trig thing. That's why I was looking at the
buildings and other higher geographic markers to get a fix on how it
appeared to be moving relative to those things. Plus, for a moment I was
stopped and pretty much next to it, although of course I was on the
ground and it was probably a couple of thousand feet up or less. And, if
it makes a difference in possible explanations, the plane was headed
east and I was moving west. I'm 99.999% sure it wasn't moving or was
moving very slowly.

Note, I've driven in this particular area for more than a decade and
I've seen hundreds of planes moving in the sky from many vantage points
under many different weather and cloud conditions. I'm pretty sure of
what I saw. Your explanation makes great sense but I'm still not
convinced that it was an optical illusion. Really hope so though because
it was quite disturbing.

Debbie

DM wrote:


yes, I've imagined the whole trig thing. That's why I was looking at the
buildings and other higher geographic markers to get a fix on how it
appeared to be moving relative to those things. Plus, for a moment I was
stopped and pretty much next to it, although of course I was on the
ground and it was probably a couple of thousand feet up or less. And, if
it makes a difference in possible explanations, the plane was headed
east and I was moving west. I'm 99.999% sure it wasn't moving or was
moving very slowly.

Put me in for $100 on that 99,999-to-1 odds bet! g

Seriously, it sounds like you are trying to understand what you
perceived, and I think the responses here have been right on target.
I'm betting on the laws of physics and hope some explanation here will
lead to an "aha" for you, to understand what caused your perception.
--
Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.

In article ,
says...

yes, I've imagined the whole trig thing. That's why I was looking at the
buildings and other higher geographic markers to get a fix on how it
appeared to be moving relative to those things. Plus, for a moment I was
stopped and pretty much next to it, although of course I was on the
ground and it was probably a couple of thousand feet up or less. And, if
it makes a difference in possible explanations, the plane was headed
east and I was moving west. I'm 99.999% sure it wasn't moving or was
moving very slowly.


You were moving in opposite directions - This is notoriously the most
difficult movement to perceive. The enormous size of the object is the other
factor that confuses our judgement. Sooner or later you are going to have to
accept the 0.001% and admit that you were victim - just as all of us have been
- to an illusion. It's actually a very common illusion, and if it's the first
time you see it, in your frequent drives near that airport, it very well may
not be the last. You must accept that your eye *cannot* reasonably appreciate
the size of the thing. You cannot know how high it is, or how far away it is
or its position relative to ground landmarks or where it would land on the
ground if it were to fall at that instant.

I have seen such illusions many times - but your suggestion that the plane
was stopped, or nearly so, is quite impossible.

G Faris