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Lancair crash at SnF



 
 
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  #31  
Old April 25th 08, 12:42 AM posted to rec.aviation.piloting,rec.aviation.student
SR20GOER
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Default Lancair crash at SnF


"WingFlaps" wrote in message
...
On Apr 25, 3:12 am, Dylan Smith wrote:
On 2008-04-24, Brian wrote:

Depends on what you mean by "the impossible turn". If you mean turning
back
at 200 AGL, yeah, that one's pretty much impossible. If you mean 600
AGL,
it's pretty much possible in the average aircraft. (Hell, that's
pattern
altitude at EFD!) The line lies somewhere in between.


It is statements like this that get pilots killed.


It's statements like 'never turn, always land straight ahead' that also
gets pilots killed. There are plenty of airfields where going straight
ahead is quite possibly the worst option, and the best survivability
options are at least a 120 degree turn away from whatever point you're
at when at 600' AGL.

The only thing you can do is use the best judgement at the time. You get
one chance - it may be wrong. Sometimes, trying to turn back might be
wrong. Sometimes doing anything *other* than trying to turn back might
be wrong.

In gliders, every glider pilot is taught "the impossible turnback" from
200 feet (which, in the typical low performance training glider, is
about equal to turning back at 600 feet in a C172).


It's the L/D that makes it much harder in a typical powered plane.
This means that all manouvers lose energy much faster. The turn back
needs at least 2 turns as well as acceleration if there is any wind.
You will note that nearly all the accidents are stall spins -a moments
thought about the situation will make you realize why this is. The
turns are made tight because there is not enough height/time for a
lazy turn.

Let's work some real numbers for a 172 at 500'. Say climb was a Vx 59
knots. The plane must first be accelerated to 65 for best glide. The
pilot carries out some trouble checks say 10s. Calls on the radio =10
s and plans his return. Note that 20s have probably elapsed. The plane
has already travelled ~0.4 miles and at a 10:1 glide ratio has lost
200' (assuming he did get it to best glide in the first place). Can

he make 2 turns and land back -no way!

Ah you say, I'm a much better pilot, I would loose not more than 10
seconds in starting my turn back., trimming etc.
But how much does the turn back cost? Assuming you keep to 45 degrees
of bank to stay _above_ stall (the stall is now damn close -better
hope there's no significant wind) the turns are still going to cost
you 35 seconds. 45 seconds lost = 450 feet! Now we add in the energy
losses from having to accelerate with the wind and to glide speed.
It's still an impossible turn. Try to tighten that turn more and you
have to dive to accelerate to avoid the stall and what does that do to
your energy management and turn radius?

Now what safety margin is appropriate for you and you PAX? Say 100%
in that case, unless you've climbed to 1000' don't even think about
turning back but practice spotting good landing sites.

I've also heard a lot of BS in this thread about not having good
palces to put the plane. There is nearly always somewhere flat to put
the plane within 90 degrees of the runway centerline -even a road.
Malls have big parking lots! Put it down flat in landing config and
you will probably survive, stall spin and you'll DIE along with your
PAX. A good pilot looks at the airport environs in a strange airport
and may ask about options at the runway end for this emergency.

Cheers

Why two turns? At 500' why not one turn and land with wind up derriere?
And, at 500 ft I wouldn't be too worried about the radio.
Brian


  #32  
Old April 25th 08, 12:43 AM posted to rec.aviation.piloting,rec.aviation.student
Bertie the Bunyip[_25_]
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Default Lancair crash at SnF

WingFlaps wrote in
:

On Apr 25, 3:12*am, Dylan Smith wrote:
On 2008-04-24, Brian wrote:

Depends on what you mean by "the impossible turn". If you mean
turning

back
at 200 AGL, yeah, that one's pretty much impossible. If you mean
600 AG

L,
it's pretty much possible in the average aircraft. (Hell, that's
patter

n
altitude at EFD!) The line lies somewhere in between.


It is statements like this that get pilots killed.


It's statements like 'never turn, always land straight ahead' that
also gets pilots killed. There are plenty of airfields where going
straight ahead is quite possibly the worst option, and the best
survivability options are at least a 120 degree turn away from
whatever point you're at when at 600' AGL.

The only thing you can do is use the best judgement at the time. You
get one chance - it may be wrong. Sometimes, trying to turn back
might be wrong. Sometimes doing anything *other* than trying to turn
back might be wrong.

In gliders, every glider pilot is taught "the impossible turnback"
from 200 feet (which, in the typical low performance training glider,
is about equal to turning back at 600 feet in a C172).


It's the L/D that makes it much harder in a typical powered plane.
This means that all manouvers lose energy much faster. The turn back
needs at least 2 turns as well as acceleration if there is any wind.
You will note that nearly all the accidents are stall spins -a moments
thought about the situation will make you realize why this is. The
turns are made tight because there is not enough height/time for a
lazy turn.

Let's work some real numbers for a 172 at 500'. Say climb was a Vx 59
knots. The plane must first be accelerated to 65 for best glide. The
pilot carries out some trouble checks say 10s. Calls on the radio =10
s and plans his return. Note that 20s have probably elapsed. The plane
has already travelled ~0.4 miles and at a 10:1 glide ratio has lost
200' (assuming he did get it to best glide in the first place). Can

he make 2 turns and land back -no way!

Ah you say, I'm a much better pilot, I would loose not more than 10
seconds in starting my turn back., trimming etc.
But how much does the turn back cost? Assuming you keep to 45 degrees
of bank to stay _above_ stall (the stall is now damn close -better
hope there's no significant wind) the turns are still going to cost
you 35 seconds. 45 seconds lost = 450 feet! Now we add in the energy
losses from having to accelerate with the wind and to glide speed.
It's still an impossible turn. Try to tighten that turn more and you
have to dive to accelerate to avoid the stall and what does that do to
your energy management and turn radius?

Now what safety margin is appropriate for you and you PAX? Say 100%
in that case, unless you've climbed to 1000' don't even think about
turning back but practice spotting good landing sites.

I've also heard a lot of BS in this thread about not having good
palces to put the plane. There is nearly always somewhere flat to put
the plane within 90 degrees of the runway centerline -even a road.
Malls have big parking lots! Put it down flat in landing config and
you will probably survive, stall spin and you'll DIE along with your
PAX. A good pilot looks at the airport environs in a strange airport
and may ask about options at the runway end for this emergency.


Exactly.

I've practiced turning back. It's difficult, at best, even when you know
it's going to happen. It has to be planned before the departure and the
pilot mjst be very sharp to get away with one. No way is comparable to a
rope break in a glider at 200' unless it's something like a Luscombe.
Even if I went out and practiced them continuously, I don't think I'd
try one on the day unless the outlying terrain was really poor and the
departure field was particularly well suited to me doing so. But doin
git without proficiency is suicide. Better to het something at 55 under
control than to spin from 100 feet.

Bertie
  #33  
Old April 25th 08, 12:43 AM posted to rec.aviation.piloting,rec.aviation.student
Bertie the Bunyip[_25_]
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Posts: 3,735
Default Lancair crash at SnF

Stefan wrote in news:9f9a3$481106d6$54487369
:

WingFlaps schrieb:

(the stall is now damn close -better
hope there's no significant wind)

...
Now we add in the energy losses from having to
accelerate with the wind and to glide speed.


Arrrgh! Not the old "turn into downwind" legend again! Better work out
your understanding of physics before publicly reasoning about turns.

There is nearly always somewhere flat to put the plane


The operative word in this sentence is "nearly".



so you've done this, have you?


Bertie
  #34  
Old April 25th 08, 12:58 AM posted to rec.aviation.piloting,rec.aviation.student
Bertie the Bunyip[_25_]
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Posts: 3,735
Default Lancair crash at SnF

WingFlaps wrote in news:80a95935-4492-4d7d-95c1-
:

On Apr 25, 10:48*am, Stefan wrote:
WingFlaps schrieb:

Try reading the statement again, here it is:


"Now we add in the energy losses from having to accelerate with the
wind and to glide speed."


Now perhaps you would like to revise some physics and try to

critcise
it for us?


It's the "having to accelerate with the wind" part which is complete

BS
unless I completely misunderstand what you are trying to say.


The latter I think. The imposed accelerations associated with the
change in direction (from upwind to downwind) require control inputs
that add drag and increased energy loss (from drag).

To summarise your missed point, the pilot control inputs cost energy
that is not factored into simple glide/time analysis.


Nope, the wind is going to help you in almost every way if you're
turning back. Firstly, your climnb gradient will have improved from the
headwind, leaving you higher for a given distance from the field. Also,
your glide is going to be improved by the tailwind when you do turn
downwind. also, your best LD speed is going to occur at a lower
airspeed, which will give you a couple of extra seconds if you have the
presence of mind to take advantage of it. You'll probably be a little on
the slow side after having made the turn anyway, so that's a help there.
If there is any crosswind element to the wind, you have another plus if
you turn towards the wind. The x-wind will minimise the radius of the
manuevering turns you will have to make.
There is no inertia involved in making a downwind turn. None. What does
cause trouble during a climbout is twofold. the wind gradient can cause
trouble, as it will for any tailwind/climb situation because inertia
does play a role there, and two, the perceived acceleration to the
eyeball can cause the pilot to do some untoward things. That's how that
particular old wive's tale came about.
However, the gradient is also your friend in the turnback/tailwind on
approach situation. the decreasing tailwind will bump your airspeed up
on approach and cut your G/S as you descend back to the runway.
I'd consider a turnback with some headwind on takeoff and the calmer it
is the less consideration I'd give to that avenue, depending of course
on the other circumstances.


Bertie
  #35  
Old April 25th 08, 01:24 AM posted to rec.aviation.piloting,rec.aviation.student
Bertie the Bunyip[_25_]
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Default Lancair crash at SnF


Why two turns? At 500' why not one turn and land with wind up
derriere? And, at 500 ft I wouldn't be too worried about the radio.



When you turn back for the runway, you will not be lined up with it! Still
air, you have to turn in excess of 180 deg to get back on or near the RW
centerline and then, you need to make on in the opposite direction to line
up.


Bertie




  #36  
Old April 25th 08, 01:31 AM posted to rec.aviation.piloting
gatt[_3_]
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Posts: 193
Default Lancair crash at SnF

WingFlaps wrote:

A Lancair crashed just moments after takeoff here in Mesa, Arizona,
today, too. Plane was headed for California. There was smoke trailing
from the plane on takeoff and controllers cleared them to turn back
around and land. They tried -- they made the left turn but crashed into
the orange orchard. Three fatalities, all in their late 20s. Sympathies
and prayers to the families.


When will pilots learn to stop trying to do the impossible turn... and
go for a straight ahead landing on soemthing horizontal?


What a bummer.

The Jeppeson Instrument/Commercial text has a great illustration of how
turning to land after losing power on takeoff doesn't work.

-c
  #37  
Old April 25th 08, 01:33 AM posted to rec.aviation.piloting
gatt[_3_]
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Posts: 193
Default Lancair crash at SnF

Dylan Smith wrote:


We don't know it was an 'impossible turn'. We don't even know what
altitude they were at, whether the engine was still developing power or
not, or whether the plane caught fire, or ... there simply isn't enough
information to


Except we know they didn't make it. Assuming the pilot was reasonably
proficient, that suggests the turn couldn't be made.

Late '20s, flying a Lancair. Well, at least he seems to have lived well.

-c
  #38  
Old April 25th 08, 01:33 AM posted to rec.aviation.piloting,rec.aviation.student
Larry Dighera
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Default Lancair crash at SnF

On Fri, 25 Apr 2008 00:48:45 +0200, Stefan
wrote in :

WingFlaps schrieb:

Try reading the statement again, here it is:

"Now we add in the energy losses from having to accelerate with the
wind and to glide speed."

Now perhaps you would like to revise some physics and try to critcise
it for us?


It's the "having to accelerate with the wind" part which is complete BS
unless I completely misunderstand what you are trying to say.



Here's what a physics professor, pilot and author of Performance of
Light Aircraft* had to say on the subject of downwind turns when he
was active on Usenet:



http://groups.google.com/group/rec.a...41feb8649bbe12
Nov 22 1996, 1:00 am

The Kinetic Energy "Paradox"

Several recent rec.aviation.xx threads have featured or involved the
apparent paradox that an aircraft which turns downwind thereby
undergoes a large gain of kinetic energy (KE) w.r.t. (with respect
to) the earth but no gain of kinetic energy w.r.t. the air mass.
Initial
(incorrect) physical reasoning is often along these lines: there is
only a constant velocity (that of the wind) difference between CSs
(coordinate systems) fixed w.r.t. the earth and w.r.t. the air. Hence
time rates of change of velocities (accelerations) are the same in
the two systems (the derivative of a constant being zero); hence so
are the forces the same in both (the mass never varies). Since it
takes a difference in forces to produce a difference in kinetic
energies, there SHOULD be no such KE difference. But there is.

The error is in the seemingly innocuous statement that two
identical forces F(t), t the time, produce the same KE difference.
The solution is to see that even though the forces, as seen in the
two CSs, are identical, the DISTANCES moved under those
forces, and the parallelism between force and displacement, are
NOT the same. Delta_KE = Int(F dot dr) = Int(F dot v)dt=F dot
vdelta_t; Int' stands for integral, F and dr and v are vectors and
dot' is that of the dot or scalar product, the product of the two
flankers times the cosine of the angle between them. Angular
brackets, as X , stand for the average of quantity X. If one keeps
track of the displacements, and their orientation with respect to the
forces, which is what vector analysis does, then the kinetic energy
difference computes properly and, as always, there is NO
PARADOX. The truth is that the forces ARE the same, but the
kinetic energy changes w.r.t. the two systems are NOT the same.

Here's a simple example. A jet is heading North, unit vector i, at
speed V w.r.t. the earth. The stewardess, Linda, of mass m, is
walking South at velocity -si w.r.t. the jet. V might be 600 mph, s
might be 4 mph. She hands a copy of Mountain Pilot magazine to a
passenger, reverses course, and walks North at velocity +si.

W.r.t. the jet, Linda has undergone a momentum change delta_p =
2msi. And, also w.r.t. the jet, a KE change delta_KE = 0.

W.r.t. the earth, Linda has undergone a momentum change delta_p
= 2msi (the same as w.r.t. the jet). And, also w.r.t. the earth, a KE
change delta_KE = (m/2)*(V+s)^2 - (m/2)*(V-s)^2 = 2mVs. Not at
all the same as w.r.t. the jet.

The force of the deck carpeting on Linda's pumps, F(t), is in the +i
direction during her turnabout maneuver; some sort of Gaussian
peak over a relatively small time interval delta_t. Ignoring the
small walking speed difference, her speed w.r.t. the earth
throughout that maneuver was essentially V. (A relatively tiny bit
less before she got stopped, a relatively tiny bit more afterwards.)
So F dot V = FV (they're in the same direction). Now her
momentum change is Int(F dt) = F delta_t = 2msi. We can use
this fact to evaluate Fdelta_t, plug it in the average of the
integral formulation in the second paragraph, and find that indeed
her delta_KE = 2msV, just as calculated by taking simple
differences.

The short time intervals, integrals approximated as averages, etc.,
are only incidental features which have no bearing on the essential
argument. (Not any more than accelerations at the end and
beginning of one twin's journey at 0.9c has any real bearing on the
twin "paradox" in special relativity.) The only trouble with treating
the original airplane case, which I've done, is that you get two and
a half pages of fairly dense vector calculus and the Internet is not
yet sophisticated enough to let us put that across uniformly in this
kind of forum.

The result: though the forces are the same in the two coordinate
systems (air mass and earth), the greater distance travelled in the
earth-based system, and the fact that those displacements in space
are not perpendicular to the forces (as they always are in the air
mass based system), means that indeed kinetic energy IS gained in
a downwind turn w.r.t. the earth. Here's the final result:
Delta_KE(w.r.t. earth) = -m*omega*R*Vw*(cos(omega*tf)-1),
where omega is the angular speed (yaw rate) in radians/sec, R is
the radius of the turn w.r.t. the air mass, Vw is the wind speed, and
tf is the time of flight. When you do a 180-degree turn, tf = T/2,
where T is the time needed to make a circle w.r.t. the air mass.
Then delta_KE = 2m*omega*R*Vw. If you continue around to
make a 360, you find, as intuition suggests, that delta_KE(w.r.t.
earth) = 0.

NO paradox. There never is. There's only (hopefully, temporary)
CONFUSION. Physics is wonderful.
-------------------------------------


http://groups.google.com/group/rec.a...c4f35133062386
Jun 25 1996, 12:00 am

Here's a posting I came up with this afternoon which *SHOULD* excite
some discussion. At the moment, however, it is also
my genuine opinion.
John

You Do Lose Airspeed in a Downwind Turn

John T. Lowry, PhD
Flight Physics
Billings, Montana
(406) 248 2606

June 1996

I came across a side reference to the infamous "downwind turn
controversy" in an Internet user group posting. Then I located a
reference to that conundrum, in Joe Christy's "Good Takeoffs
and Good Landings," 2nd edition. On page 11 Mr. Christy writes:

...there is no difference between downwind, upwind, or
crosswind turns in flight. They are all the same to the
airplane.

It seems that beginning flight students think that they will
need to add power or angle of attack when turning from upwind
to downwind because of the loss of airspeed inherent in the
reversal of direction. Later on they learn the more sophisti-
cated "truth." As expressed by Joe Christy farther down the
same page:

Remember, when airborne, you are carried *with* a moving
air mass independently of your movement *through* it.

His italics shown with *XX*. So the conventional wisdom is that
there is no difference, except for the name, between a turn from
downwind to upwind and one from upwind to downwind. Let's leave
it at that for the moment.

And let's change the subject; to that of horizontal wind shear,
or gusts. Say you're heading into the wind at 100 KTAS and at
first (Wind A) the wind is 40 knots. Suddenly (Wind B) there is
a slackening gust to only 10 knots. (All wind speeds are ground
speeds, speeds with respect to the earth just below them.) What
happens? Your airspeed suddenly drops 30 knots to 70 KTAS. (For
the moment, your 60 knot ground speed stays the same.) Let's say
you take no immediate pilot control action. If your airplane is
properly trimmed, the lower airspeed results in the airplane
both losing altitude and nosing over. Airspeed begins to
recover. When the original 100 KTAS is regained, you're back
into trim. Albeit at a lower altitude. The point is: your air
speed really did diminish. In fact there's a caveat to the
conventional wisdom in a figure caption on that same page of
Mr. Christy's book:

To an airplane in flight, there is no difference between
turning downwind, crosswind, or upwind, *except when
flying through a wind shear*.

This time, my (**) italics. So at this point we have it that
turning towards downwind does not result in loss of air speed
but flying into a slackening gust does result in loss of
airspeed.

But here's the kicker. *Turning to downwind is the same thing
as a slow wind shear*. Say you start a coordinated turn from
upwind towards downwind at standard rate, 3ø per second. At the
start, say you have a 30 knot headwind. A second later you have
a 30*cos(3ø) = 30*0.9986 = 29.96 knot headwind. It's not much
less, but it *is* less. After turning for 10 seconds you've
turned 30ø and the headwind has slacked off to "only"
30*cos(30ø) = 30*0.8660 = 25.98 knots. That's getting to be at
least marginally perceptible, but remember the effect has been
continuously spread over ten seconds. After a quarter turn from
headwind to crosswind, 90ø, which took 30 seconds, your relative
headwind has changed by 30 knots.

That 30 knots is almost precisely the size (50 ft/sec) of the
FAA's standard gust. But the FAA takes it that the gust develops
its full force over only one quarter second! There's the
difference. The same wind change, spread over a time interval
30/0.25 = 120 times as long and at a time while you've already
increased angle of attack to counteract your banked and
therefore off-vertical lift vector, and possibly also increased
power a little to counteract increased induced drag and
increased trim drag in the turn, is essentially imperceptible.
The time scales are vastly different.

So you do lose airspeed in a downwind turn. Only, normally, not
much.

I can imagine that students and instructors of aviation have
infused their hangar flying sessions on this subject with
several additional scientific red herrings. The Internet
posting I mentioned even got into general relativity. Here are
the more likely possibilities I can think of.

Possible Red Herrings in the Downwind Turn Controversy

1. The air mass in which the airplane is embedded is an inertial
frame and so . . . .

If the air mass is steady, that's so. But if you fly from Wind A
into slower moving Wind B, you're talking about two *different*
inertial frames. Your air speed is your speed through the air in
which you're currently flying, not your speed relative to the
air a mile back. An airplane can change air speed quite rapidly
because the speeds of air molecules can vary considerably from
one place to another place fairly near by. That is, gusts exist.

2. Air speed is air speed, so . . . .

Air speed is speed through that air *in the direction the
airplane is pointed*. Say I told you an airplane was progressing
northward against a 30 knot wind out of the north and its ground
speed was northward at 70 knots. You'd probably say its air
speed was 100 knots. But what if I told you, in addition, that
that airplane's nose was pointed directly to the *south*. (The
ultimate skidded flat turn.) Tilt! Unfair! Now the air speed has
suddenly become -100 knots. The concept of air speed takes a bit
more refinement than most of us give it.

3. The earth isn't actually an inertial frame of reference
anyway . . . .

True. But the non-inertial terms (due to rotation about its axis
and revolution about the sun) are known. And quite small. So for
all practical intents and short term purposes, the earth is an
inertial frame. Therefore, a force is necessary to change the
speed of the airplane relative to the earth. Even if the
airplane flew into a vacuum, it would *initially* still move at
the same speed in the same direction, just as does a tennis ball
you drop out the window of a speeding car. Then, as the changed
and unbalanced forces took over, the airplane would accelerate.

In summary, my answer to the downwind turn controversy is: You
do lose air speed in a downwind turn, but in a "noisy"
environment and only over a time span that renders that loss
almost imperceptible. Still, I think those beginning students
were right.

COMMENTS? CONTRARY VIEWS?

-------------------------------------

http://groups.google.com/group/sci.p...37f136c766e351
Feb 10 1999, 1:00 am

There is a problem similar to the ball/train/kinetic energy problem in
aviation. When turning from heading upwind to heading downwind, the
airplane apparently has a large gain of kinetic energy (as measured
with respect to the Earth underneath). Even though the forces acting
on the airplane during the turn (aerodynamic + weight) are the same in
both the Air Mass- and the Earth-based systems (uniform motion between
them), the kinetic energies are not. It's because Delta_KE is the
integral of Force dot dr and the space increments dr are NOT the same
in the two systems.

Rather than go into this with pilots I usually simplify to a flight
attendant handing a passenger a magazine, then turning on her pumps
and walking back the way she came from. Similar to the bouncing ball.

John.

John T. Lowry, PhD
Flight Physics; Box 20919; Billings MT 59104
Voice: 406-248-2606
----------------------



http://groups.google.com/group/aus.a...e03975757e040d
Mar 16 1999, 1:00 am

Gavan Cook asked me to address this issue. It's a repost of an older
response on the same subject in rec.aviation.piloting.

For me, the convincing reason there is NO DIFFERENCE
between a downwind turn and an upwind turn is: **all the relevant
FORCES in the turn (except gravity, which doesn't change) are
aerodynamic.** With those forces being only between the airframe
or control surfaces or propeller and the AIR, what possible effect
could anything else have? It's only forces which make
accelerations which are changes in velocity. This of course
assumes the exact same air mass motion (no gusts or wind shear),
the same control inputs, etc., throughout the two (to downwind or
to upwind) turn maneuvers.

Now the airplane DOES slow down (in air speed) in a turn,
due to increased induced drag due to larger lift due to bank, but it
doesn't slow down any MORE in a downwind turn than in an
upwind one.

Phil's insistence on a **coordinated** turn is very
important in a practical sense. Say you turned by kicking hard
rudder, with a real big rudder, so that you skidded around 180
degrees in (say) two seconds. (Strange to say, one airline pilot told
me another airline pilot told him that this slewing-around skidding
turn is just the thing to do!) THEN you've got a problem all right.
You've then got (almost) your original 50 knots of ground speed,
in the same direction (now backwards), plus a 20 knot tailwind.
Seventy knots air speed, but a NEGATIVE 70 knots air speed with
reference to the direction the airplane is pointed. You'd "fall out of
the sky." However, there is no difference in this foolish maneuver
whether it's a turn to downwind or upwind. In the other case,
where you'd initially have 70 knots air speed and 90 knots ground
speed, an instantaneous skidded reversal would leave you at 90
knots ground speed backwards and a 20 knot headwind, net result
still the exact same negative 70 knots air speed with reference to
the direction the airplane is pointed. So still a real bad idea to
skid around, but the SAME bad idea whether to downwind or upwind.

There's no AERODYNAMIC difference between turns to
dowwind or to upwind. The only differences are between their final
ground speeds, and in the perception of the pilot who unwittingly
slows his air spseed when he notices, by looking at the earth,
increased ground speed during and after his turn to downwind.

Hope this clarifies. Sometime later on I'll address the
question "Where does the additional kinetic energy (with respect to
the earth, an (approximate) inertial frame of reference), after a
downwind turn, come from?" It DOES come, even though all the relevant
forces, as argued above, are the same. It's a subtler issue.

John Lowry.
--
John T. Lowry, PhD
Flight Physics; Box 20919; Billings MT 59104
Voice: 406-248-2606

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  #39  
Old April 25th 08, 01:41 AM posted to rec.aviation.piloting,rec.aviation.student
Tman
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Posts: 68
Default Lancair crash at SnF

Hold on while I try to correct some nits in what Bertie said and see
what happens

Bertie the Bunyip wrote:
Nope, the wind is going to help you in almost every way if you're
turning back.

[ many good points supporting this assertion, but... ]
also, your best LD speed is going to occur at a lower
airspeed,

Well, technically, your best LD speed is related to angle of attack, and
not the groundspeed, so that won't change. Your best glide speed
certainly will be less...

There is no inertia involved in making a downwind turn. None.


Here's why I wonder about that. Let's suppose 65 KAS before and after a
180 turn from a 10 KT headwind. OK, before the turn, your groundspeed
is 55KTS and after the turn your groundspeed is 75KTS. Your intertial
frame of reference is tied to the g/speed, not the a/speed. So -- the
kinetic energy of the aircraft and contents is about 33% higher
(75/55)^2. That energy is only going to come from one place with no
power -- trading in altitude (potential energy) for kinetic energy.
  #40  
Old April 25th 08, 01:44 AM posted to rec.aviation.piloting
gatt[_3_]
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Posts: 193
Default Lancair crash at SnF

Buttman wrote:
On Thu, 24 Apr 2008 17:05:06 +0200, Stefan sayeth:

Brian schrieb:

Your right in that many aircraft it is possible. But the problem is it
isn't possible for many pilots when the engine quits. It is not a
maneuver that is routinly practiced.

Now this problem could be solved.


You're suggesting instructors practice engine failures with their
students on takeoff? Oh boy, better hope Dudly doesn't see this...


One way to practice this would be to establish a "runway altitude" at,
say, 1000ft AGL, get the airplane into takeoff configuration on heading
at that altitude over a road or something, simulate a failure at a
specified altitude--say, 1,500 feet--and see what altitude you're at
when you get back to your reciprocal heading. If it's above your
starting altitude, you made it.

Wind, density altitude and aircraft weight are significant variables.

Of course, a proficient pilot will have considered all these variables
as well as the terrain downrange before takeoff, so they already know
what they will do if the engine quits at a specific altitude. On
probably as many checkrides and flight reviews as not, the instructor
has asked me what I will do if I lose power on takeoff so I already know
where there transmission lines are, about how far it is to the lake, etc.

-c
 




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