"position & hold" going away

Steven wrote:
That depends on the albedo of the airplane, the angle it presented to the
sun, the brightness of the landing light, and the exact direction it was
facing. It does not sound unreasonable to me, although I wasn't there at
that exact moment.

The landing light may have made the arriving aircraft harder to spot. In
WWII it was found that forward facing lights mounted on ASW aircraft allowed
them to get closer to surfaced submarines before being spotted.

I expect the pilots of those planes knew enough to make their attack
runs with the sun at their back; i.e. a direction where the vision of
the submariners would be impaired.
Lights can be used as camouflage when you have a relatively dark plane
silouetted against a brighter sky. But in this circumstance where the
landing plane is observed from the direction of an almost setting sun
you have the opposite situation; a brightly illuminated plane seen
against an already darkening sky. Adding lights would then only make
the plane more visible.

Similarly the bright white winter coat of an arctic hare is good
camouflage, but the same color on an albino rabbit in a hay field just
makes it stand out as an obvious target.

Steven wrote:
Because they were human and sometimes make mistakes, especially under
conditions of poor visibility such as caused by having to look in the
direction of the sun near the horizon.

Why would they be looking in the direction of the sun near the horizon
instead of in the direction of the runway?

Landing on runway 24 the direction is almost the same. Also note that
the sunlight would be reflecting off things on the ground such as
rooftops, any pools of water, vehicle windows, etc. Even if you can
lower a visor to hide the sun itself, there are still lots of bright
sources of reflected light on the ground that can create glare and
distraction and make it that much easier to make a mistake and miss
seeing the plane on the runway.

Go out just before sunset and look at the sky in the direction opposite
from the sun. You should notice that it's already considerably darker
than at midday even though the sun has not yet set. Looking in that
direction a plane would be very easy to see because it would be
brightly lit by the sun and is set against a darker background sky. If
the landing light is on that would make it even more visible.

So at the time of this accident the crew of the landing plane had
relatively poor visual conditions while if the crew of the plane on the
ground had been in a position to look back they would have had
excellent visibility.

If it's truly just before sunset there isn't much sun above the horizon to
be shining in the eyes of the approaching crew.

As I recall it was about half an hour before sunset so all of the sun
was still above the horizon. But the sky at that time is already much
darker than during the middle of the day.

Presumably the purpose is to be able to respond quickly to a clearance
to take off. If the plane is angled but full power can still be
applied and the plane's path down the runway straightened out in the
first few seconds of the takeoff roll then no time would be lost and
the same purpose would still be achieved.

Time is lost because full power is not being applied in the direction of the
takeoff roll.

No, it takes a certain amount of time for a plane to reach takeoff
speed after the application of full throttle. Whether the first few
seconds of that acceleration are spent going straight down the runway
or starting out at an angle and then straightening out will have no
significant effect on the time to accelerate to the critical speed.

Consider this from an energy standpoint. The engines need to provide
enough power for a long enough time to give the plane enough kinetic
energy for takeoff. The only effect of starting out at an angle and
then straightening will be a miniscule increase in rolling resistance
of the nose wheel due to slight scrubbing forces. The energy lost to
that slight extra rolling resistance is negligible compared to the
total takeoff energy.

Well, if the conditions are such that the arriving aircraft cannot see an
aircraft on the runway, it's unlikely the aircraft on the runway could have
spotted the arriving aircraft even if it had been cocked towards it. The
aircraft on the runway has to scan a larger area and at varying distances.
The arriving aircraft has to scan a much smaller area and at a fixed
distance, the runway surface.

Black cat in a coal mine at night, hiding from a miner with a
flashlight. Who's got the odds?

The landing light may have made the arriving aircraft harder to spot. In
WWII it was found that forward facing lights mounted on ASW aircraft allowed
them to get closer to surfaced submarines before being spotted.

Maybe. I haven't seen the study but do see where this could be true.
I've also read that bright colors in angular patterns made better
camoflauge than the standard green on green.

Depending on how the light hit, it could go either way in any specific case.

Jose
--
Quantum Mechanics is like this: God =does= play dice with the universe,
except there's no God, and there's no dice. And maybe there's no universe.
for Email, make the obvious change in the address.

Steven wrote:
People see what they expect to see.

A pilot sitting on a runway obviously wouldn't expect to see an airplane
landing on that runway.

Mike indicated that he would feel more comfortable positioning his
plane at an angle on the runway so he could look behind for landing
traffic. Since he'd be looking back specifically to look for incoming
planes he'd be unlikely to miss seeing such a plane especially if
lighting and weather conditions were favorable.

OTOH, the crew of a plane that's been cleared to land would be looking
at the runway primarily to judge their approach and might be more
likely to miss seeing another plane since they wouldn't be expecting
one there. Such a mistake would be more likely under poor visibility
conditions such as landing into a setting sun when glare from various
reflections would make objects on the ground harder to distinguish.

Such conditions could easily increase their effort to focus on viewing
the end of the runway and the numbers to judge their landing in much
the same way that viewers in the psychology perception test focussed on
the basketball passes and totally missed the presence of the gorilla.

In article . net,
"Steven P. McNicoll" wrote:

People see what they expect to see.

A pilot sitting on a runway obviously wouldn't expect to see an airplane
landing on that runway.

Yeah, no pilot ever sees that, or ever even looks. That's how I was
taught years ago. Once cleared on the runway, I know it's always
mine and never ever need to look.

not

--
Bob Noel
no one likes an educated mule

On Sun, 28 Aug 2005 20:53:00 GMT, "Steven P. McNicoll"
wrote in
. net::

If the plane is angled but full power can still be
applied and the plane's path down the runway straightened out in the
first few seconds of the takeoff roll then no time would be lost and
the same purpose would still be achieved.


Time is lost because full power is not being applied in the direction of the
takeoff roll.

In your estimation, about how much time would be lost in the case of a
typical GA aircraft, a Cessna 172?

On Mon, 29 Aug 2005 03:58:25 -0400, Bob Noel
wrote in
::

In article . net,
"Steven P. McNicoll" wrote:

People see what they expect to see.

A pilot sitting on a runway obviously wouldn't expect to see an airplane
landing on that runway.

Yeah, no pilot ever sees that, or ever even looks. That's how I was
taught years ago. Once cleared on the runway, I know it's always
mine and never ever need to look.

not

Exactly. Arguing that a pilot should place his aircraft in the path
of arriving traffic and in a position from which he is unable to
observer arriving traffic, in the name of expediency, is contrary to
good safety practice.

The fact that pilots may at times under IFR operations place the
well-being of their flights in the hands of ATC controllers does not
mitigate the risk caused by the Position And Hold procedure.