Almost a statisic

"Mike Rapoport" wrote in message
ink.net...

"Sriram Narayan" wrote in message
news:1105574315.223629d9c9b6178c7b6b555f5ecac8c3@t eranews...

"Gary Drescher" wrote in message
...
"dlevy" wrote in message
...
I had a pitot/static problem as a new PPL (clear weather) that was
very
exciting. Airspeed was fine till about 20 feet off the ground. At
that
point airspeed would start dropping. I kept pushing the nose over and
airspeed kept dropping. I then realized rpm's were normal, the
propellor
was attached, and everything sounded right. It scared the bejezus
outta
me. Turned out to be water in the static line. Afterwards, I realized
I
was way too dependant on that one indicator. Had it been IMC, it
could
have been very ugly.

Hm, shouldn't a blocked static line cause the airspeed indicator to
show
an
increase in airspeed, rather than a decrease, with increasing altitude?


It would indicate a lower airspeed.

The pitot ram air pressure for a given airspeed decreases with higher
altitude. If the static port were blocked (at say, the takeoff
altitude),
the airspeed would "indicate" a lower airspeed since the pitot pressure
has
dropped for that airspeed as the plane gains altitude. As another poster
commented, the only altitude where the ASI is accurate is at the
altitude
where the blockage occurred.



Actually, the OP didn't say anything about the static line being blocked,
he
said that it had water in it. The static pressure availilble at the
instruments still changes in the proper direction if the static (or pitot)
line has water in it, it just changes at a different (usually lower) rate.


Mike
MU-2
Helio Courier



I don't disagree. I was responding to Gary Drescher's post (not the OP)
where he talked about a blocked static port, not one which may have water in
it, which like you say behaves like a partially blocked port but could be
even more erratic.

In my case, it was a CAVU day but extremely windy and quite turbulent. It
was 25G35 blowing straight down the runway with a 10-15kt shear every now
and then. I was bouncing all over the place on final, and the ground was
going by much more slowly than in a normal 0-15kt headwind. My ASI, VSI, and
altimeter were all not working, the sight picture was constantly changing
due to turbulence, and the rate of ground passage was much slower than on a
normal day, making it difficult to guage anything accurately by sight. It
was nice to be able to know I was nowhere near the stall by adding 25 to my
GPS groundspeed.

The cause of this remains unknown, as it cleared itself up while I was still
about 500'. The symptoms were a non-zero but clearly wrong airspeed (it was
stuck at about 60 kts for a while), a VSI pegged at 1000fpm climb, and a
frozen altimeter.

"Colin W Kingsbury" wrote in message
ink.net...

"dlevy" wrote in message
...
GPS groundspeed implies airspeed. If the airspeed indicator is zero,
rpm's
2500, the nose pitched up, and gps groundspeed holding at 80 knots......
which is wrong?

You see the ground moving and the altitude isn't dropping- no GPS needed


GPS groundspeed isn't really useful for aviating, since you've got to
factor
wind in. 20 knots is the difference between too fast and too slow in
approach. OTOH, if you fly pitch and power settings, you won't come to
grief
no matter what the wind is doing. Even IFR the GPS groundspeed isn't
necessary. If your power is too low you'll lose altitude, too high you'll
climb. I've flown complete approaches in actual IFR with a post-it over
the
ASI, and never once looked at the GPS groundspeed.

So, you don't need the GPS to tell you you're moving, and it can't tell
you
what your airspeed is, while pitch/power will let you fly the plane all
day
long. What does GPS buy me again in this situation?

"Colin W Kingsbury" wrote in message
ink.net...
snip
GPS groundspeed is useless for flying the plane. What do you think
you're
getting by watching it?

-cwk.

I thought so too. Apparently, the instrument knew better. That's one of
the reasons it was an exciting event!

BTW, it was water in the static line. Maybe that is different from a
complete blockage?

I made my instructor go up with me to prove to someone else what was
happening.


"Gary Drescher" wrote in message
...
"dlevy" wrote in message
...
I had a pitot/static problem as a new PPL (clear weather) that was very
exciting. Airspeed was fine till about 20 feet off the ground. At that
point airspeed would start dropping. I kept pushing the nose over and
airspeed kept dropping. I then realized rpm's were normal, the propellor
was attached, and everything sounded right. It scared the bejezus outta
me. Turned out to be water in the static line. Afterwards, I realized I
was way too dependant on that one indicator. Had it been IMC, it could
have been very ugly.

Hm, shouldn't a blocked static line cause the airspeed indicator to show
an increase in airspeed, rather than a decrease, with increasing altitude?

--Gary

"Jeremy Lew" wrote in message
...
In my case, it was a CAVU day but extremely windy and quite turbulent. It
snip
was nice to be able to know I was nowhere near the stall by adding 25 to
my
GPS groundspeed.

I'm still not sold. Here's my thinking. You've got squirrely winds changing
direction and speed with altitude. So, at best you have to bracket that
GPS-derived airspeed by +/- 10kts just to be sure. If we're talking about
approach speeds this is quite a difference. So, broken record again, it's
not fundamentally useful since it can't be considered accurate for flying
the plane.

OTOH, here comes the broken record again, trimming for pitch attitude and
setting power for the chosen regime of flight *will* produce a known
airspeed. In my Skyhawk if you set one notch of flaps and 1900rpm and trim
for level flight, the speed will stabilize around 72kts. Pull 500rpm and
trim nose up one full turn and you'll descend at just about 500fpm at 72
kts. 2350 and level will always indicate 95-100kts. Climb is of course
whatever you can get with full throttle and 10deg nose up. This is the Law
of the Wing: it has ever been thus, and thus it ever shall be.

Also, if you fly the same plane regularly, or even just the same type, you
should be able to "feel" the airspeed reasonably well without any
instruments at all. Obviously this is easier in a pussycat like a 172
compared to a Mooney or Bo, but its still possible. Most pilots today just
don't get enough practice in slow flight because our instinct has become to
avoid it. Instrument pilots get a double whammy because we tend to focus our
proficiency activities on IFR skills, which expressly avoid true slow-flight
for good reason, but this compounds the problem. Of course, I'm speaking
about myself here as well, but all this is the way my CFII trained me, and I
try to live up to it.

Best,
-cwk.

Colin, you adopt quite the air of authority for someone who has had their
ASEL for less than 2.5 years. In this case I wanted to come in at about
80kts and one notch because of the wind shear, which is not a normal
approach speed or flap configuration for me. Are you telling me you have
memorized every permutation of pitch/power/flaps/airspeed for all possible
gust conditions on approach?

"Colin W Kingsbury" wrote in message
news

"Jeremy Lew" wrote in message
...
In my case, it was a CAVU day but extremely windy and quite turbulent.
It
snip
was nice to be able to know I was nowhere near the stall by adding 25 to
my
GPS groundspeed.

OTOH, here comes the broken record again, trimming for pitch attitude and
setting power for the chosen regime of flight *will* produce a known
airspeed. In my Skyhawk if you set one notch of flaps and 1900rpm and trim
for level flight, the speed will stabilize around 72kts. Pull 500rpm and
trim nose up one full turn and you'll descend at just about 500fpm at 72
kts. 2350 and level will always indicate 95-100kts. Climb is of course
whatever you can get with full throttle and 10deg nose up. This is the Law
of the Wing: it has ever been thus, and thus it ever shall be.

"Jeremy Lew" wrote in message
...
Colin, you adopt quite the air of authority for someone who has had their
ASEL for less than 2.5 years. In this case I wanted to come in at about
80kts and one notch because of the wind shear, which is not a normal
approach speed or flap configuration for me. Are you telling me you have
memorized every permutation of pitch/power/flaps/airspeed for all possible
gust conditions on approach?

Depending on how and what you fly, 1 notch and 80 kts sounds awfully close
to approach configuration in either level flight or descending on the ILS.
Some people fly a little slower, others a little faster, but it's in the
ballpark. If you told me to climb at 100FPM and 90 knots, no, I have no idea
what the setting for that is off the top of my head. But that's not the
situation.

If my normal approach speed is 65 knots, and I want to fly 75 for gusty
conditions, I'm not using the GPS groundspeed to do it. It's too coarse a
measure to be used with real precision. I'm setting up for an ILS-type
configuration which normally settles right in at 72 knots, and adding
another 50-100rpm and trim to hold the descent rate around 500rpm. I bet
that'll get me pretty darn close, at least on the right side of things. I
contend that you're better off setting pre-determined power/pitch settings
and understanding control feel than looking at the GPS groundspeed expecting
to learn too much from it.

This all got started because someone who sounded even greener than me said
they were going to keep an eye on their GPS groundspeed during takeoff, and
it didn't strike me as such a great idea, for all the reasons I've laid out.
A reasonable (i.e. can be formed in one good lesson) understanding of
pitch/power settings will allow you to fly the plane safely all day long
without an ASI, in any kind of conditions. I don't think this is
particularly controversial and it's the way I was taught when I got my
private, instrument, and seaplane ratings.

Of course we all use everything available to us to form the most complete
picture possible, and GPS groundspeed can be included in that, so long as we
account for its limitations. It can tell you magnitude of change (i.e. a
change in groundspeed of 10kts at constant power/pitch means the wind has
changed 10kts) for instance and that is useful. More importantly, it can
tell us how much longer we have to go before we can empty our tanks, or fill
our plane's.

Forget my authority or lack thereof. What is wrong with my reasoning here?

best,
-cwk.

There's nothing wrong with your reasoning in general, but it *was* your
original assertion that the groundspeed is "useless for flying the plane."
Again, in my case, I had no ASI, VSI or altimeter to work with, so how am I
supposed to trim to hold a 500fpm descent? What if the pitch indication
was slightly off? I set it up by sight and feel as best I could and used
the groundspeed as a crosscheck, which I maintain was useful for flying the
plane. You're right about takeoff, I don't see the value there.

BTW, I'm only 3 months less green than you chronologically, and probably
greener in flight-hours


Jeremy
"Colin W Kingsbury" wrote in message
nk.net...

"Jeremy Lew" wrote in message
...
Colin, you adopt quite the air of authority for someone who has had their
ASEL for less than 2.5 years. In this case I wanted to come in at about
80kts and one notch because of the wind shear, which is not a normal
approach speed or flap configuration for me. Are you telling me you have
memorized every permutation of pitch/power/flaps/airspeed for all
possible
gust conditions on approach?

Depending on how and what you fly, 1 notch and 80 kts sounds awfully close
to approach configuration in either level flight or descending on the ILS.
Some people fly a little slower, others a little faster, but it's in the
ballpark. If you told me to climb at 100FPM and 90 knots, no, I have no
idea
what the setting for that is off the top of my head. But that's not the
situation.

If my normal approach speed is 65 knots, and I want to fly 75 for gusty
conditions, I'm not using the GPS groundspeed to do it. It's too coarse a
measure to be used with real precision. I'm setting up for an ILS-type
configuration which normally settles right in at 72 knots, and adding
another 50-100rpm and trim to hold the descent rate around 500rpm. I bet
that'll get me pretty darn close, at least on the right side of things. I
contend that you're better off setting pre-determined power/pitch settings
and understanding control feel than looking at the GPS groundspeed
expecting
to learn too much from it.

This all got started because someone who sounded even greener than me said
they were going to keep an eye on their GPS groundspeed during takeoff,
and
it didn't strike me as such a great idea, for all the reasons I've laid
out.
A reasonable (i.e. can be formed in one good lesson) understanding of
pitch/power settings will allow you to fly the plane safely all day long
without an ASI, in any kind of conditions. I don't think this is
particularly controversial and it's the way I was taught when I got my
private, instrument, and seaplane ratings.

Of course we all use everything available to us to form the most complete
picture possible, and GPS groundspeed can be included in that, so long as
we
account for its limitations. It can tell you magnitude of change (i.e. a
change in groundspeed of 10kts at constant power/pitch means the wind has
changed 10kts) for instance and that is useful. More importantly, it can
tell us how much longer we have to go before we can empty our tanks, or
fill
our plane's.

Forget my authority or lack thereof. What is wrong with my reasoning here?

best,
-cwk.

Jeremy,

Chalk it up to typical Usenet hyperbole. I like to write with a little zip
which sometimes interferes with the message. I agree that used as a
cross-check the groundspeed can be useful, and you obviously understand what
it's really telling you. As usual I suspected you and I were pretty much on
the same page but the debate club geek inside of me got out and argued the
point for the sake of it. As someone who's still quite green I remember all
too well the temptation to get lost staring at the instruments. I had this
picture in my head of this new pilot watching the GPS groundspeed and not
fully comprehending what it meant. A new pilot should focus on learning to
fly the plane by feel and become comfortable with high-performance takeoffs
and landings, crosswinds, and cross-country navigation. Unfortunately, this
is typically the last thing that happens once you get out of the structured
training environment, especially if like me you are located at a big field
where the crosswind runway is 5000' long.

One of the best things I did as a new pilot was to get my floatplane rating
up in Alaska (I live in Boston). It wasn't meant to happen the way it did,
but I literally left to go there two days after I passed my checkride. They
(Alaska Float Ratings, highly recommended) gave instruction in a Super Cub
which was quite a different critter than the Warriors I got my ticket in.
The instructors were working 135 pilots and knew how to wring every drop of
performance out of the plane. Plus, flying patterns at 400AGL and being
surrounded by the Chugach mountains was a whole new experience for this
flatlander. Being as green as I was (am) I think my bad habits were a little
less ingrained and I was able to absorb things better than I would a few
hundred hours later.

It's actually getting to be time to do another check on my slow
flight/crosswind skills. I try to do a ride every six months or so to keep
me on my toes. I think what I really need to do is take some trips to some
smaller fields where I *have* to land in a thousand feet or so. I've been
busy starting a new business lately so it's getting real sloppy and all of
my practice has focused on instrument approaches.

Been fun chatting,
-cwk.

"Jeremy Lew" wrote in message
...
There's nothing wrong with your reasoning in general, but it *was* your
original assertion that the groundspeed is "useless for flying the plane."
Again, in my case, I had no ASI, VSI or altimeter to work with, so how am
I
supposed to trim to hold a 500fpm descent? What if the pitch indication
was slightly off? I set it up by sight and feel as best I could and used
the groundspeed as a crosscheck, which I maintain was useful for flying
the
plane. You're right about takeoff, I don't see the value there.

BTW, I'm only 3 months less green than you chronologically, and probably
greener in flight-hours


Jeremy
"Colin W Kingsbury" wrote in message
nk.net...

"Jeremy Lew" wrote in message
...
Colin, you adopt quite the air of authority for someone who has had
their
ASEL for less than 2.5 years. In this case I wanted to come in at
about
80kts and one notch because of the wind shear, which is not a normal
approach speed or flap configuration for me. Are you telling me you
have
memorized every permutation of pitch/power/flaps/airspeed for all
possible
gust conditions on approach?

Depending on how and what you fly, 1 notch and 80 kts sounds awfully
close
to approach configuration in either level flight or descending on the
ILS.
Some people fly a little slower, others a little faster, but it's in the
ballpark. If you told me to climb at 100FPM and 90 knots, no, I have no
idea
what the setting for that is off the top of my head. But that's not the
situation.

If my normal approach speed is 65 knots, and I want to fly 75 for gusty
conditions, I'm not using the GPS groundspeed to do it. It's too coarse
a
measure to be used with real precision. I'm setting up for an ILS-type
configuration which normally settles right in at 72 knots, and adding
another 50-100rpm and trim to hold the descent rate around 500rpm. I bet
that'll get me pretty darn close, at least on the right side of things.
I
contend that you're better off setting pre-determined power/pitch
settings
and understanding control feel than looking at the GPS groundspeed
expecting
to learn too much from it.

This all got started because someone who sounded even greener than me
said
they were going to keep an eye on their GPS groundspeed during takeoff,
and
it didn't strike me as such a great idea, for all the reasons I've laid
out.
A reasonable (i.e. can be formed in one good lesson) understanding of
pitch/power settings will allow you to fly the plane safely all day long
without an ASI, in any kind of conditions. I don't think this is
particularly controversial and it's the way I was taught when I got my
private, instrument, and seaplane ratings.

Of course we all use everything available to us to form the most
complete
picture possible, and GPS groundspeed can be included in that, so long
as
we
account for its limitations. It can tell you magnitude of change (i.e. a
change in groundspeed of 10kts at constant power/pitch means the wind
has
changed 10kts) for instance and that is useful. More importantly, it can
tell us how much longer we have to go before we can empty our tanks, or
fill
our plane's.

Forget my authority or lack thereof. What is wrong with my reasoning
here?

best,
-cwk.

That's all I meant.....

"Colin W Kingsbury" wrote in message
ink.net...

snip
I agree that used as a cross-check the groundspeed can be useful,
snip