Three more newbie Qs, if you don't mind :)

"Ramapriya" wrote in message
om...

1. Is there a way of mathematically justifying the dictum that a
successful takeoff is guaranteed if you develop 70% of the desired
thrust in half the runway length? And is this dictum kind of set in
stone or are there riders?

I've never heard it but I don't fly jets. I doubt it can be mathematically
justified. Too many variables.

2. I've heard that you can let an aircraft fly itself off, so to
speak, by lifting the nose early in the takeoff roll to the desired
takeoff attitude.

You're barking up the right tree, at least partially. The Angle of Attack is
the critical element, though for most purposes you can use airspeed instead.
There are three numbers that apply he

Vx: Best angle-of-climb speed: This is the speed at which you gain the most
altitude per unit of distance traveled over the ground. If there's a tall
tree at the end of the runway you need to clear, this is what you want to
use.

Vy: Best rate-of-climb speed: The speed at which you gain the most altitude
per minute. This is both faster and more efficient than Vx, but because it's
shallower you may hit the tree at the end of the runway if you climb at this
speed.

Vr: Rotation speed: This is the speed at which you want to lift the nose off
the runway. If you rotate too soon, you will create drag and actually
lengthen the takeoff roll. If you rotate too late, you lenghten takeoff roll
unnecessarily. This number becomes pretty important on big jets, not as much
on small planes unless you're trying to dig out of a short runway.

There's also the phenomenon of "ground effect." When a wing is within one
wingspan of the ground, it will generate more lift. The result is that you
can get a plane to lift off the ground and fly in ground effect at lower
airspeed than it will fly at. If you try to climb out of ground effect
without sufficient airspeed, the most likely result is that you'll bounce
back down onto the runway. If you wait too long to abort you'll meet that
tree at the end of the runway. However, you can use this to your advantage
in some situations. For instance, if you're taking off from a grass field
(which tends to slow you down more than asphalt) you take off and pop up
into ground effect and then stay there (not climbing) until you accelerate
to Vx and then climb. Because there is less drag up in the air you will take
off in less distance.

Regarding the core question of the airplane "flying itself off" I don't
think this would work in most larger planes, but it would definitely happen
in most light airplanes.

3. Is it possible for a cruising aircraft (say at 35000 feet) to
descend and land without the pilot having to pitch the nose downward
even once? I mean, is it possible to lose altitude by just a
combination of the throttle and flaps? I know it might take a lot
longer to do it this way but is it a theoretical possibility?

This is a pretty complicated question actually. There have been several
incidents where aircraft lost all primary controls and landed with some
success. United 232 (?) is one of the most famous, but the DHL plane shot by
a missile over Baghdad last year also suffered total hydraulic failure and
managed to land on its gear under control. UA232 might have also, but for a
puff of wind at the very end.

A full description of the challenges this situation poses would have to
start by teaching you basic aeronautics. If you are interested in that, I
suggest you read "Stick and Rudder" by Langewiesche, and is written for the
non-pilot. Suffice it here to say that it is a deadly serious challenge,
among the worst situations you can find yourself in short of plummeting
straight towards the ground. But as these crews demonstrated, it is not
hopeless.

-cwk.

Take a demonstration flight at a flight school near you. An inexpensive way
to get a lot of your questions answered.

-0-

"Ramapriya" wrote in message
om...
Hi all,

I'm encouraged by your non-disparaging response to my first posting
here yesterday. I have a few more Qs that will look utterly idiotic to
you guys -- but remember that I'm not a pilot

Er... actually I'm from India, where flying is affordable to a very
small section of the populace, and I've never been in that category.
Poverty hasn't helped keep my interest for flying down, although it
hasn't helped in making that actually happen :\

Also, I'm 37 and 64 inches tall, both prohibitive minuses to even
think of flying lessons, from what I've heard. One guy (a pilot) had
said I wouldn't be able to reach the rudder pedal with my short
stature, making me wonder if planes don't have adjustable seats like
cars do

Ramapriya



"Will Robinson" wrote in message news:awPid.25$mL1.15@trnddc08...
Take a demonstration flight at a flight school near you. An inexpensive way
to get a lot of your questions answered.

"Ramapriya" wrote in message
om...
Also, I'm 37 and 64 inches tall, both prohibitive minuses to even
think of flying lessons, from what I've heard.

When I first read that sentence, I thought you were 101 inches tall. That
definitely would cause problems.

However, being 37 certainly has nothing to do with taking flying lessons (it
might keep you out of an airliner cockpit, that's about all), and your
height, while admittedly lower than average, is no shorter than many others
who pilot airplanes. Most airplanes do have adjustable seats, some other
airplanes have fixed position seats with adjustable rudder pedals, and not
all airplanes are created equal. Just as with cars, some are better suited
to smaller pilots, while others are better suited to larger pilots.

Even in a plane where you don't fit right off the bat, there are ways to
work around the issue. I've heard of at least one pilot wearing what amount
to platform shoes, for example.

Anyway, access to affordable training sounds like the biggest impediment,
and for all I know in India that's enough to prevent you from learning to
fly. But certainly nothing about your age or height would.

Pete

(Ramapriya) wrote in
om:

Er... actually I'm from India, where flying is affordable to a very
small section of the populace, and I've never been in that category.
Poverty hasn't helped keep my interest for flying down, although it
hasn't helped in making that actually happen :\

Also, I'm 37 and 64 inches tall, both prohibitive minuses to even
think of flying lessons, from what I've heard. One guy (a pilot) had
said I wouldn't be able to reach the rudder pedal with my short
stature, making me wonder if planes don't have adjustable seats like
cars do

Ramapriya




I don't think 5'4" is a problem. I have taught students who were about that
height. You can pull the seats forward, but the rudder is at a fixed depth
behind the panel, and if you pull too far forward your face will be too
close to the panel. You may also face a problem with seeing over the panel.
For that you may need a seat cushion.

37 is not old. Some have started that late and even gone on to airline
jobs, but admittedly that is not very common. There are plenty of people
who took their first lesson past 30 and went on to earn all the ratings and
are very active in aviation. In fact, I would suspect that the majority of
GA pilots started in their 30's or later.


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Ramapriya wrote:
Er... actually I'm from India, where flying is affordable to a very
small section of the populace, and I've never been in that category.
Poverty hasn't helped keep my interest for flying down, although it
hasn't helped in making that actually happen :\

Also, I'm 37 and 64 inches tall, both prohibitive minuses to even
think of flying lessons, from what I've heard. One guy (a pilot) had
said I wouldn't be able to reach the rudder pedal with my short
stature, making me wonder if planes don't have adjustable seats like
cars do

64 inches --- so what? Lots of shorter people fly. I'm only 66 in
and fly with no problem -- pillows or telephone books!

37 years old -- so what? We're not talking flying for a major airline
in the US, just aviation knowledge.

You can probably finds books about aerodynamics and aviation in
a school library. Is there an airport nearby? Talk to people there
about working/helping.

Ramapriya wrote:

Also, I'm 37 and 64 inches tall, both prohibitive minuses to even
think of flying lessons, from what I've heard.

In this country, you could still manage to have a career of ten years or more as an
airline pilot, with a bit of luck. You are definitely not too old to learn to fly.
While there are a few aircraft in which you would have trouble reaching the rudder
pedals (mine is one), you would have no problems in many aircraft. They also make
extensions for the pedals for very short people, and these could be mounted in
aircraft like mine, which would let you fly them.

I have read that flying is very expensive in India, however, and there's no way
around that. Better move.

George Patterson
If a man gets into a fight 3,000 miles away from home, he *had* to have
been looking for it.

(Ramapriya) wrote in
om:

Hi all,

I'm encouraged by your non-disparaging response to my first posting
here yesterday. I have a few more Qs that will look utterly idiotic to
you guys -- but remember that I'm not a pilot

1. Is there a way of mathematically justifying the dictum that a
successful takeoff is guaranteed if you develop 70% of the desired
thrust in half the runway length? And is this dictum kind of set in
stone or are there riders?

Successful takeoff is never guaranteed... But specifically to your dictum,
if your throttle setting is not high enough to create adequate lift, you
may get 100% of the selected thrust and never get off the ground.

More seriously, though, since takeoff distance is affected by other factors
besides thrust, such as wind speed and direction, angle of attack of the
control surfaces, runway terrain and condition, trim position, etc. I can't
imagine that your dictum, which by the way I never heard before, is set in
stone.

2. I've heard that you can let an aircraft fly itself off, so to
speak, by lifting the nose early in the takeoff roll to the desired
takeoff attitude. To a non-pilot like me, it's intriguing how this can
be possible. I know that plane manufacturers prescribe takeoff flap
settings, which means that there's gotta be some predetermined angle
of the wing with reference to the horizontal that'll give the aircraft
an optimal kind of lift at some speed enough to make it afloat and
keep it afloat. How then would increasing this wing angle, which is
what would happen by an early nose-lift, help? If at all, I feel it'll
get the craft airborne without enough speed to sustain itself,
whereupon it should start descending before too long... I could be
completely wrong in the way I'm thinking here but would love to hear
how this principle works.

Your intrigue comes, IMHO, from a lack of understanding of the power curve
and of the relationship between pitch and power how they are controled.
This is even more pronounced in your third question.

For the answer to this question, though, look to the Elevator Trim tab,
which attaches to the elevator and essentially stabilizes the elevator at a
certain attitude, which produces a specifc speed based on the power
setting. Basically, the Elevator Trim tab is like a cruise control. The
plane will constantly seek out the set speed - if the plane is flying more
slowly than that speed, the nose will start to fall and the plane will go
faster. If the plane is flying faster than that speed, the nose will start
to pitch up and the plane will start to slow down. If left on its own, the
plane will sort of bobble up and down until it finally levels off at the
set speed...

On the ground, part of the pre-takeoff checklist includes setting the trim
tab to the takeoff position, which is marked on the trim control, and
generally sets the trim tab to about climbout speed at full power. If the
plane were in the air already flying at that trim setting and full power,
the plane would be climbing in a climb attitude at climbout speed. As the
plane speeds up on the runway, then, and the airspeed increases past
climbout speed, the nose of the plane will pitch up to slow the plane back
down to climbout speed. This will essentially start to lift the plane off
the groud all by itself. In fact, no pulling back on the yoke is necessary
to take the plane off the ground if the trim tab is set properly. It will
do it all by itself if you can keep the plane on the runway.

3. Is it possible for a cruising aircraft (say at 35000 feet) to
descend and land without the pilot having to pitch the nose downward
even once? I mean, is it possible to lose altitude by just a
combination of the throttle and flaps? I know it might take a lot
longer to do it this way but is it a theoretical possibility?

A plane can cut power completely, pitch the nose up, descend in a stall all
the way to the ground, and do this at a very aggressive rate. In fact, a
plane can have full power, pitch way up, and be descending in a stall.
Without the proper angle of attack on the wing, the wing doesn't produce
enough lift to carry the weight of the plane, and the plane falls. Even
with thrust,though, the airspeed relative to the angle of attack of the
wing is what really impacts lift.

You may be stifling laughs by now at these but I hope to get better in
the days to come through such Qs... not wrong to hope, is it?

If you want to get better, I have a better idea - just go to your local
airport Fixed Based Operator and make an appointment for a discovery
flight. If you're not sure where to start to look, try www.beapilot.com .
They will give you a certificate for a $50 intro flight, and help you find
the nearest flight school...

It's great to talk about it in a newsgroup, it doesn't compare to the
first-hand experience...