Re: GPS glide ratio calculations

[Jason Armistead]

(Kirk Stant) wrote in message >...
> James,
>
> Interesting hobby!
>
> You could use a GPS logger (like a Volkslogger or Colibri), set to
> minimum logging interval (1 or 2 seconds). You would have to download
> the trace afterwards and use a program to view it. I would recommend
> SeeYou, but some other more terrain-oriented programs might have
> better terrain resolution (which would be important for you, I
> assume).
>
> This setup would require a small battery hooked up to the logger, but
> with the short flight duration it shouldn't be too big.
>
> Some of the newer Garmin handhelds also log altitude, they may be a
> lot cheaper and just as useful. The key is probably going to be the
> software you use to look at the trace.
>
> Let us know how it works out.
>
> Kirk
> LS6-b "66"

Given the relatively short flight time, and the inherent inaccuracy of
GPS (even with Selective Availability switched off by the US
Government), you might find that the error in the GPS fix is
insufficient for accurate speed measurements.

Try setting up your GPS in a fixed location, and then leave it there
logging data for a few minutes. You will see that the position fix
moves around slightly due to the inherent inaccuracy of the system.

For a discussion of Selective Availability and accurace of GPS, see
the following site:

http://www.ngs.noaa.gov/FGCS/info/sans_SA/

and the linked-to Accuracy Comparison pages, especially the most
recent one

http://www.ngs.noaa.gov/FGCS/info/sans_SA/compare/ERLA.htm

which suggests 6.3 metre accuracy with SA off and 45 metres with SA
on.

Small, perhaps, but maybe important when you're taking short-period
differentials (1st derivative of position give speed). If you're
moving 60 km/h (approx 16.6 m/sec) then an error of 1m in your
position fix (well within the error limits of GPS) will give you a
derived speed now of between 15.6 m/sec (56 km/h) and 17.6 m/sec (63.3
km/h). Try repeating those calculations with a worst-case inaccuracy
of 6.3 metres and you get speeds between 37 km/h and 82.4 km/h !

I would perhaps consider going to a Differntial GPS (DGPS) system,
where a known fixed local station broadcasts supplemental position
correction information that improves the accuracy of the satellite
location fix.

For a good discussion of accuracy between GPS and DGPS systems, see

http://www.gpscontrol.com/php/support/tutorial/accuracy.php

In summary, my take on all this is that GPS is good for averaged
velocity based on samples over a period of several seconds (our
minutes, like gliding !), rather than instantaneous velocity based on
sample-to-sample differentiation where GPS accuracy can cloud the
results (like your free-falling bird man attempts).

Good luck and watch those landings !


Cheers

Jason

[Mike Borgelt]

On 4 Sep 2003 21:11:38 -0700, (Jason Armistead)
wrote:

(Kirk Stant) wrote in message >...
>> James,
>>
>> Interesting hobby!
>>
>> You could use a GPS logger (like a Volkslogger or Colibri), set to
>> minimum logging interval (1 or 2 seconds). You would have to download
>> the trace afterwards and use a program to view it. I would recommend
>> SeeYou, but some other more terrain-oriented programs might have
>> better terrain resolution (which would be important for you, I
>> assume).
>>
>> This setup would require a small battery hooked up to the logger, but
>> with the short flight duration it shouldn't be too big.
>>
>> Some of the newer Garmin handhelds also log altitude, they may be a
>> lot cheaper and just as useful. The key is probably going to be the
>> software you use to look at the trace.
>>
>> Let us know how it works out.
>>
>> Kirk
>> LS6-b "66"
>
>Given the relatively short flight time, and the inherent inaccuracy of
>GPS (even with Selective Availability switched off by the US
>Government), you might find that the error in the GPS fix is
>insufficient for accurate speed measurements.
>
>Try setting up your GPS in a fixed location, and then leave it there
>logging data for a few minutes. You will see that the position fix
>moves around slightly due to the inherent inaccuracy of the system.
>
>For a discussion of Selective Availability and accurace of GPS, see
>the following site:
>
>http://www.ngs.noaa.gov/FGCS/info/sans_SA/
>
>and the linked-to Accuracy Comparison pages, especially the most
>recent one
>
>http://www.ngs.noaa.gov/FGCS/info/sans_SA/compare/ERLA.htm
>
>which suggests 6.3 metre accuracy with SA off and 45 metres with SA
>on.
>
>Small, perhaps, but maybe important when you're taking short-period
>differentials (1st derivative of position give speed). If you're
>moving 60 km/h (approx 16.6 m/sec) then an error of 1m in your
>position fix (well within the error limits of GPS) will give you a
>derived speed now of between 15.6 m/sec (56 km/h) and 17.6 m/sec (63.3
>km/h). Try repeating those calculations with a worst-case inaccuracy
>of 6.3 metres and you get speeds between 37 km/h and 82.4 km/h !
>
>I would perhaps consider going to a Differntial GPS (DGPS) system,
>where a known fixed local station broadcasts supplemental position
>correction information that improves the accuracy of the satellite
>location fix.
>
>For a good discussion of accuracy between GPS and DGPS systems, see
>
>http://www.gpscontrol.com/php/support/tutorial/accuracy.php
>
>In summary, my take on all this is that GPS is good for averaged
>velocity based on samples over a period of several seconds (our
>minutes, like gliding !), rather than instantaneous velocity based on
>sample-to-sample differentiation where GPS accuracy can cloud the
>results (like your free-falling bird man attempts).
>
>Good luck and watch those landings !
>
>
>Cheers
>
>Jason


Jason,

GPS does not use the sample to sample differences to give you
velocities. The 3 D velocities are done from Doppler shifts.

Mike Borgelt

[Jonathan Gere]

Not much use to Jason, when his Garmin or IGC logger won't record that
velocity information. Or are you suggesting he look at the velocity
screen and take notes while falling (I mean flying).

Jonathan Gere


Mike Borgelt > wrote in message >...
>
> Jason,
>
> GPS does not use the sample to sample differences to give you
> velocities. The 3 D velocities are done from Doppler shifts.
>
> Mike Borgelt

[Tom Seim]

Why don't you try a safer sport, like standing in front of a Mach
truck and seeing how close it can get before jumping out of the way.

Base jumpers are in the same class as low pass flyers, in my opinion.
This is a contest you don't want to win.

I suggest that you go to a group more alligned to your thinking, like
the alt.sport.russion.roulette people.

[Tom Seim]

Philip Plane > wrote in message >...
> In article >, Tom Seim wrote:
> > Why don't you try a safer sport, like standing in front of a Mach
> > truck and seeing how close it can get before jumping out of the way.
>
> Ah, the happy sound of a 'safe' pilot.
>
> > Base jumpers are in the same class as low pass flyers, in my opinion.
> > This is a contest you don't want to win.
>
> You're probably right.
>
> Low pass flyers love the rush. They like a little excitement.
> They probably also have a better safety record than the rule
> followers who think rules will keep them safe when the
> reality is that the only thing that will keep you safe is your
> own judgement.


Philip,

You should avoid debating as an occupation. 'Probably' is the choice
of word for those who haven't done their homework. We know that pilots
have died attempting these low passes; are you seriously arguing that
their safety records are better than the norm?

I agree with you that good judgment enhances your safety. I just don't
think that you (and the low passers) have good judgment. You are free
to partake in your high-risk sport, just don't argue that it is safe.
Newbies do look to veterans when formulating the rules that,
eventually, become what we call *judgment*. Bad judgment, for this
reason, must be clearly labled as such because the newbies are reading
these posts.

Tom

[Philip Plane]

In article >, Tom Seim wrote:

>> Low pass flyers love the rush. They like a little excitement.
>> They probably also have a better safety record than the rule
>> followers who think rules will keep them safe when the
>> reality is that the only thing that will keep you safe is your
>> own judgement.
>
>
> Philip,
>
> You should avoid debating as an occupation. 'Probably' is the choice
> of word for those who haven't done their homework. We know that pilots
> have died attempting these low passes; are you seriously arguing that
> their safety records are better than the norm?

You're right, I probably should.

I wouldn't shy away from the safety record of people who do low passes
though. A well executed low pass is nothing to be worried about.

I certainly know that the pilots I am familiar with who do a low
pass whenever they see the opportunity all have good safety records.
Probably because they (mostly) use good judgement about where and when
to perform the low pass.

I have seen a few badly executed low passes though, and they
are the sort of thing that people should worry about. But the
same can be said of any part of gliding. Do it right, or you're
in trouble. I expect base jumpers also have to do it right.

> I agree with you that good judgment enhances your safety. I just don't
> think that you (and the low passers) have good judgment. You are free
> to partake in your high-risk sport, just don't argue that it is safe.

> Newbies do look to veterans when formulating the rules that,
> eventually, become what we call *judgment*. Bad judgment, for this
> reason, must be clearly labled as such because the newbies are reading
> these posts.

Whoops. You just pushed another of my buttons.

Rules aren't judgement. Rules are used to define the normal, expected
way to do things. There are, for instance, rules to be followed
when doing a low pass. Judgement is knowing when to follow the rules.

And 'newbies' can use their own judgement to stay within their own
capabilities. Because an activity is beyond the skill level of some
pilots doesn't mean that those who can do it should not. If the
newbies don't see people doing advanced stuff, how will they know
what more there is on offer?

Aviation is a risky business. We can manage that risk to make it 'safe'.
We manage the risk by building our skills up so we can reduce the
risk. We manage the risk by building our judgement up to recognise
what is within our skill level. And we all have a personal level of
risk we are willing to accept.

--
Philip Plane _____
|
---------------( )---------------
Glider pilots have no visible means of support

[Jack]

in article , Kirk Stant at
wrote on 2003/09/08 15:32:

> ...post-[low]pass stall-spins from pattern altitude [are] a pattern
> problem, not a low pass problem.

> Bad judgement is attempting something you are not trained for or
> experienced enough for. Good judgement is acquiring the skills
> necessary prior to performing any demanding task. Otherwise, anything
> can be dangerous.

> ...the ex-fighter pilot senior airline captain does a gentle,
> tail first, low energy landing in his glass ship.



Low passes, in themselves, are no more dangerous than the aero tow.

Lots of low passes are safely done all over the world, at much higher speeds
and in more hostile environments than your local glider port will ever be --
with live ordnance yet!

The busy-body self-appointed safety minders will squeeze every drop of fun
from life if we let them. Don't be one of them -- but don't ever give them
more ammunition by trying maneuvers for which you are not thoroughly trained
and prepared.



Jack

(ex-fighter pilot, retired airline captain, new glider pilot -- not yet
ready to do low glider passes -- and too cheap to buy "glass")

[Mike Borgelt]

On 8 Sep 2003 22:58:50 GMT, Andy Blackburn
> wrote:

>Over the past 30 years I have known more than a few
>people who've died while flying a sailplane - and I've
>been witness to a couple. I can think of a few speed
>related accidents and they all invloved loss of control
>and/or structural failure at several thousand feet
>altitude. I've never heard of a fatality, or even
>an accident during a 'contest finish' - either during
>a contest or at any other time, though I cannot say
>definitively that it's never happend. My personal experience
>(and statistics on the subject) suggests that we should
>be more concerned with too little speed (stall/spin)
>than too much speed.
>
>I reject the notion that contest finishes are inherently
>unsafe any more than gaggle flying, landing or tow.
>Pilots making contest finishes have as high or higher
>situational awareness than in any other phase of flight
>- they tend to be more focused and less likely to be
>multi-tasking. Like all other phases of flight, the
>maneuver can be performed well or poorly, but that
>is not the basis for making generalizations.
>
>The contest finish is an exuberant and graceful way
>to put an exclamation point on the end of a cross-country
>or racing flight (or even a local flight, for that
>matter). They are perhaps the one phase of glider flight
>that generates positive excitement with spectators
>on the ground.
>
>Goodness knows the sport could use ways to get visitors
>to the glider field excited.


Well said, Andy.
During the 1970's in Western Australia I flew at several clubs where
contest type finishes were the norm and the only guy ever to screw up
was the Chief Flying Instructor of one club in his own glider who spun
in from the top of the pullup. We used to go down to about 20 - 30
feet. I think that is reasonable as you won't hit the ground if you
encounter a gust.(that has happened in WA at another club and at Alice
Springs it was I think an IS 28 got flown through the club bar on a
low finish. Fortunately nobody was in there and the building wasn't
all that substantial and no fatalities. The 28 and the bar were write
off though.)

I then had the misfortune to spend 15 years at another club in another
state who banned contest type finishes.(amonst other things) They sure
managed to make a nice thing like gliding boring and unpleasant. They
also can't figure out why they lose members.

Mike Borgelt

[Tom Seim]

(Kirk Stant) wrote in message >...
> (Tom Seim) wrote in message
>
> >We know that pilots have died attempting these low passes; are you
> seriously >arguing that their safety records are better than the norm?
>
> Name a pilot who has died during a low pass.
>
> > I agree with you that good judgment enhances your safety. I just don't
> > think that you (and the low passers) have good judgment. You are free
> > to partake in your high-risk sport, just don't argue that it is safe.
> > Newbies do look to veterans when formulating the rules that,
> > eventually, become what we call *judgment*. Bad judgment, for this
> > reason, must be clearly labled as such because the newbies are reading
> > these posts.
> >
> > Tom
>
> You are so full of it! Show me an accident directly caused by a low
> pass, while in the low and fast part of it. Don't cheat by using
> post-pass stall-spins from pattern altitude - that is a pattern
> problem, not a low pass problem.

You, also, should avoid employment as a debater. Character assignation
is a definte debate loser. Present your supporting evidence and let it
speak for itself.

I searched the records and found 4 such accidents. And, no, I will not
exclude pull up stall-spins following the low pass. This is an
essential part of the maneuver which would not have been attempted had
it not been for the low pass. Thus the low pass was directly
contributory to the accident. The accidents are:

N117JB 11/3/01
N4458 8/26/00
N597R 10/4/96
N48032 5/26/84

When one considers the fatal accident rate by usual measures, namely
accidents per 100,000 flight hours, this maneuver goes off the Richter
scale. You, and others like you, can consider it perfectly safe, but
you are in a huge state of denial.

BTW: To estimate the accident rate you need to.
1. Estimate the duration of the manouvour in hours.
2. Estimate the number operations per year.
3. Multiply (1) by (2) and by the number of years.
4. Divide the number of accidents, 4, by the result of (3).
5. Multiple (4) by 100,000.

Rate = 4 *100000 / (.0333 * 1000 *9)
= 1333
Assumes 2 min per operation and 1000 operations per year.

Compare this to all other accident rates and you will find there is
not comparison whatsoever. Changing the assumptions, even by an order
of magnitude, doesn't change this.


> Bad judgement is attempting something you are not trained for or
> experienced enough for.

Good judgement is acquiring the skills
> necessary prior to performing any demanding task. Otherwise, anything
> can be dangerous.

What training did you get for high speed low passes? It isn't part of
the practical test standards and it certainly wasn't a part of my
training.


>
> I do low passes because they are fun. I do them safely (no overflying
> people, structures, lots of speed, no strangers in the pattern, proper
> radio calls, etc. Done correctly, they are safe. Just as skydiving,
> done correctly, is safe. Just as SCUBA divingm, done correctly, is
> safe.

We just had a SCUBA diving fatality over the weekend that involved a
certified instructor.

>
> I can just picture you and a "newbie", standing next to your ancient
> 2-33, watching somebody doing a nice high-energy low pass in a state
> of the art glass ship, water still streaming from it. The newbie says
> "Wow, that's cool, someday I want to do that!" And you respond with a
> sneer "That guy is just showing off, he's dangerous, has no judgement,
> a safe pilot would never do that, blah blah blah - stick to the local
> area and 1000ft patterns in the 2-33 like real glider pilots!
>
> And the newbie wanders off, never to be seen again....while the
> ex-fighter pilot senior airline captain does a gentle, tail first, low
> energy landing in his glass ship.

Well, the guy IS showing off, that's why they do the low passes.

I am not saying that there aren't pilots qualified to do this
maneuver, because there are. The guy that gets into trouble is the one
with 200 hours or is a high time power pilot recently transitioned
into gliders.

I see that I touched a nerve here, but that isn't my concern. Judgment
is the integration of training and experience. Let the record speak
for itself; this maneuver is, deservedly, a high risk one.

[Kirk Stant]

(Tom Seim) wrote in message

> You, also, should avoid employment as a debater. Character assignation
> is a definte debate loser. Present your supporting evidence and let it
> speak for itself.

Confusing sarcastic disagreement with character assignation (sic) is
probably not a debate winner either.

(lots of stats snipped)

Andy does an excellent rebuttal, I won't bother. I prefer first hand
observations, anyway - I've seen CFIGs crash a lot of planes on simple
training flights; the only racers I've seen hurt planes is on
outlandings (which is another issue altogether!)

> What training did you get for high speed low passes? It isn't part of
> the practical test standards and it certainly wasn't a part of my
> training.

What does the PTS have to do with it? Some things in life you have to
figure out for yourself, find out who to talk to, watch carefully, and
ease yourself into. Acro training help (is there any PTS for that?).
Self-preservation instinct helps a lot. Prior military training helps
a lot - but can be a bit expensive in time and effort. If you want
dual, go to a field with any 2 seat glass and I'm sure any competent
CFIG would be happy to show you.

> We just had a SCUBA diving fatality over the weekend that involved a
> certified instructor.

So? Anybody can screw up.

> Well, the guy IS showing off, that's why they do the low passes.

And what is wrong with showing off? We all do it - the cars we buy,
the clothes we wear, the sports we play. Just because someone is
showing off doesn't mean they lack judgement and are dangerous! What
about airshows - everybody is showing off there - thats what they are
all about!

> I am not saying that there aren't pilots qualified to do this
> maneuver, because there are. The guy that gets into trouble is the one
> with 200 hours or is a high time power pilot recently transitioned
> into gliders.

No that is exactly what you said. You were hammering the originator
of this thread for his choice of activity and "lack of judgement".
>
> I see that I touched a nerve here, but that isn't my concern. Judgment
> is the integration of training and experience. Let the record speak
> for itself; this maneuver is, deservedly, a high risk one.

Again, risk is not the same as danger. Arguably, landings are a much
more dangerous maneuver than low passes - you get much closer to the
ground, at speeds close to the stall, and can't get away from it.

You are right about touching a nerve - We wonder why this sport is
shrinking. It's not the cost (time x money probably hasn't changed
much). But while the sport is advancing, our attitudes (in the US)
seem to stand still. Very few places seem to emphasize the excitement
of soaring; all I hear is how "peaceful and relaxing" it is. That's
fine for retirees who have had all the excitement they need, but
younger newcomers to the sport need to see something more exciting to
motivate them to stay in. And yes, that means that some "risky"
behavior is part of the attraction - XC, Acro, racing. But while the
racing crowd isn't much concerned with the training/local crowd (as
long as they stay out of the way), the training/local crowd seems to
get more vocal about their dislike of the racing crowd - the
Glassholes, showing off, etc..

No stats, just personal observation.

Kirk
66

[PuffnFresh]

Hi there:

I think the Vista and will log altitude, but you have no control over
the timing of the recording unless it is a higher end version - it is
always automatic. The Garmin76 has long tracks and has better timing
control (more expensive though) - The GPS12X does not record altitudes.
Magellans have much worse support for logging tracks. They are always on
and you have almost no control over the track. I don't know about the
Flyer - it may be better. Occasionally the altitudes on GPS can be be
off and sometimes will jump around or plummet to the ground (goes to
zero suddenly because of loss of signal). I think you must keep the
antenna on the GPS clear of obstructions and then everything is fine. I
would say that the Garmin76 would be the best for your purposes.

On software - I have 3DTracer myself. It will calculate glide ratios as
you can select any section of the flight track and then perform
calculations on it. You can also load 3d maps from terrain DEM files.
(The animations are just amazing - but off topic I suppose). It is
cheaper than SeeYou and the animations are better - but less support for
OLC. I also looked at CompeGPS, too - it is geared to hanggliders - But
it had a few crashes on my machine and the 3D part was difficult to move
around in. The hard part in 3DTrace is getting the files properly set up
- the data is on the web you just must find it and calibrate the map
properly. Oh yes it also has a cool flight deck that shows you
everything thats occurring.

The other option is to hook up a PDA to the GPS and this can be your
logger - this has the difficulty that it is and extra cable, an extra
set of batteries and getting the software on the PDA. But it works - I
have the GPS12 with PDA software on an old Palm, with spliced together
cabling. It was around $500 altogether - $200 for GPS, $200 for the PDA,
$100 for the software - and you can use the PDA for its originally
intended use.

Any how my 2 cents


Kirk Stant wrote:
> James,
>
> Interesting hobby!
>
> You could use a GPS logger (like a Volkslogger or Colibri), set to
> minimum logging interval (1 or 2 seconds). You would have to download
> the trace afterwards and use a program to view it. I would recommend
> SeeYou, but some other more terrain-oriented programs might have
> better terrain resolution (which would be important for you, I
> assume).
>
> This setup would require a small battery hooked up to the logger, but
> with the short flight duration it shouldn't be too big.
>
> Some of the newer Garmin handhelds also log altitude, they may be a
> lot cheaper and just as useful. The key is probably going to be the
> software you use to look at the trace.
>
> Let us know how it works out.
>
> Kirk
> LS6-b "66"

[Tom Seim]

Jack > wrote in message >...
> in article , Tom Seim at
> wrote on 2003/09/08 23:52:
>
> > Character assignation is a definte debate loser.
>
> Perhaps you meant "...assassination", rather than "...assignation"?

Yes, my fingers were a couple words behind my brain. Shows the problem
with spell check.

>
>
> > ...pull up stall-spins following the low pass [are] an
> > essential part of the maneuver which would not have been
> > attempted had it not been for the low pass. Thus the low
> > pass was directly contributory to the accident.
>
> I think you may have to go further and tell us how you define
> "low pass". Are pull ups from three feet more dangerous than pullups from
> ten feet, or one hundred feet, or three hundred? And by how much,
> statistically speaking?

Now you are in the 'bring me a rock' mode. You are no more interested
in additional stats than you are in changing your mind on the matter.
The maneuver is an inherently high-risk one with little margin for
error. Blasting thru a busy GA airport such as the one where I fly out
of with piston A/C, turbine A/C, ultra-lights and helicopters is using
questionable judgment. Not all pilots are on the correct frequency or
have their squelch set properly. Some don't have radios at all. None
will be expecting this maneuver.

Some maneuvers are inherently more dangerous than others (i.e. ridge
soaring and landings). Their accident rate per flight hour WILL be
higher, but you don't see it referenced. It gets lumped into the
overall rate. All of us will be doing one landing for each flight; few
will be doing a low pass.

>
>
> > ...training...for high speed low passes...isn't part of
> > the practical test standards and it certainly wasn't a
> > part of my training.
>
> Then please don't do them. Nor should you presume to decide who is qualified
> to do them and who is not, nor how much risk exposure is involved.
>
>
> > Judgment is the integration of training and experience.
> > Let the record speak for itself; this maneuver is,
> > deservedly, a high risk one.
>
> The record merely tells us that some glider pilots have performed the low
> pass maneuver poorly. You have no idea how many do it every day with success
> and even aplomb.

Not many. I seldom see it performed. Most of them were done at
contests until the rules were changed over concern about safety. I
personally have done them at contests. And I admit it; they were fun!
With the new tasks which had gliders coming in to the finish line from
any direction, even though we all crossed the finish line in the same
direction, heightened the risk substantially.

>
> It is a failing of our government-approved so-called system of training
> which refuses to even acknowledge, let alone prepare pilots for, any number
> of maneuvers which a competent pilot should have in his repertoire. No
> wonder they occasionally do them poorly.
>

The current program doesn't even address cross country soaring. It
basically teaches gliding, not soaring. Yet much of the glider hours
flown are cross country. The Feds will change training requirements
when they see unusually high accident rates, which is probably just as
well because we would have a real problem getting instructors.

Let me be clear about one thing: the low pass maneuver is legal except
where prohibited by local A/P rules (assuming you don't violate some
other rule in the process). I have no intention of petitioning the FAA
otherwise (have you read the posts by the club that is having major
difficulties with the A/P management?). I was expressing my opinion to
which I am entitled, and just think that low time pilots should not be
attempting it. Now, the bird man thing is another story.

[Andy Blackburn]

Sorry, but I still don't see it. Two accidents in 20
years doesn't strike me as a top ten safety issue.
Certainly finding better ways to train for more advanced
forms of soaring (cross country, racing, acro, etc.)
and exercising good judgement generally are motherhood
issues for the sport.

I think it is possible to construct worst case scenarios
for any phase of flight and thinking about these scenarios
may prove instructive for the development of flying
judgement -- after all judgement is generally born
out of learning from experience. If you construct a
low pass scenario of gliders converging from different
directions on a busy, mixed-use airport without proper
radio procedures or situational awareness, crossing
active runways without looking, squeezing between buildings
and frightening the children it starts to sound reckless.
But in my view that is a debating canard. I can make
a simple pattern tow sound dangerous with similar 'scenario-buildi
ng' just by adding in high crosswinds, local thunderstorms,
poor preflight procedures... you get the picture.

If there are facts about actual accidents (Tom's search
turned up two that were of questionable applicability
since I don't think we're talking about attempting
loops at low altitude as a standard procedure), or
facts about near misses where another aircraft was
forced to take emergency evasive action, then maybe
there can be a productive discussion about what to
do to improve safety. But the facts don't seem to bear
this out.

Tom, I don't dispute your general points about judgement
and training, I just think we need to be careful about
characterizing certain types of flying as inherently
risky if the real point is reckless or thoughtless
flying in any phase of flight is potentially dangerous.
The first thought tends to lead to rules and regulations
about specific flight procedures (e.g. no low-passes,
no more than one glider in a thermal, no ridge soaring,
no landings [okay that might be a tough one to implement]),
but if the real issue is poor judgement generally,
than all the rules do is take the fun out of flying
and give some people a false sense of security. Some
of the clubs I've belonged to that have been the most
'rule happy' actually have poorer safety records (no
I don't have statistics). I'd hate to distract people
away from the real safety issues, which (according
to the statistics) have to do with maintaining proper
control of the aircraft and adequate flying speed/coordination.

Hope these thoughts are viewed as constructive - it's
how they are intended.

9B

At 01:54 10 September 2003, Tom Seim wrote:
>Jack wrote in message news:...
>> in article ,
>>Tom Seim at
>> wrote on 2003/09/08 23:52:
>>
>> > Character assignation is a definte debate loser.
>>
>> Perhaps you meant '...assassination', rather than
>>'...assignation'?
>
>Yes, my fingers were a couple words behind my brain.
>Shows the problem
>with spell check.
>
>>
>>
>> > ...pull up stall-spins following the low pass [are]
>>>an
>> > essential part of the maneuver which would not have
>>>been
>> > attempted had it not been for the low pass. Thus
>>>the low
>> > pass was directly contributory to the accident.
>>
>> I think you may have to go further and tell us how
>>you define
>> 'low pass'. Are pull ups from three feet more dangerous
>>than pullups from
>> ten feet, or one hundred feet, or three hundred? And
>>by how much,
>> statistically speaking?
>
>Now you are in the 'bring me a rock' mode. You are
>no more interested
>in additional stats than you are in changing your mind
>on the matter.
>The maneuver is an inherently high-risk one with little
>margin for
>error. Blasting thru a busy GA airport such as the
>one where I fly out
>of with piston A/C, turbine A/C, ultra-lights and helicopters
>is using
>questionable judgment. Not all pilots are on the correct
>frequency or
>have their squelch set properly. Some don't have radios
>at all. None
>will be expecting this maneuver.
>
>Some maneuvers are inherently more dangerous than others
>(i.e. ridge
>soaring and landings). Their accident rate per flight
>hour WILL be
>higher, but you don't see it referenced. It gets lumped
>into the
>overall rate. All of us will be doing one landing for
>each flight; few
>will be doing a low pass.
>
>>
>>
>> > ...training...for high speed low passes...isn't part
>>>of
>> > the practical test standards and it certainly wasn't
>>>a
>> > part of my training.
>>
>> Then please don't do them. Nor should you presume
>>to decide who is qualified
>> to do them and who is not, nor how much risk exposure
>>is involved.
>>
>>
>> > Judgment is the integration of training and experience.
>> > Let the record speak for itself; this maneuver is,
>> > deservedly, a high risk one.
>>
>> The record merely tells us that some glider pilots
>>have performed the low
>> pass maneuver poorly. You have no idea how many do
>>it every day with success
>> and even aplomb.
>
>Not many. I seldom see it performed. Most of them were
>done at
>contests until the rules were changed over concern
>about safety. I
>personally have done them at contests. And I admit
>it; they were fun!
>With the new tasks which had gliders coming in to the
>finish line from
>any direction, even though we all crossed the finish
>line in the same
>direction, heightened the risk substantially.
>
>>
>> It is a failing of our government-approved so-called
>>system of training
>> which refuses to even acknowledge, let alone prepare
>>pilots for, any number
>> of maneuvers which a competent pilot should have in
>>his repertoire. No
>> wonder they occasionally do them poorly.
>>
>
>The current program doesn't even address cross country
>soaring. It
>basically teaches gliding, not soaring. Yet much of
>the glider hours
>flown are cross country. The Feds will change training
>requirements
>when they see unusually high accident rates, which
>is probably just as
>well because we would have a real problem getting instructors.
>
>Let me be clear about one thing: the low pass maneuver
>is legal except
>where prohibited by local A/P rules (assuming you don't
>violate some
>other rule in the process). I have no intention of
>petitioning the FAA
>otherwise (have you read the posts by the club that
>is having major
>difficulties with the A/P management?). I was expressing
>my opinion to
>which I am entitled, and just think that low time pilots
>should not be
>attempting it. Now, the bird man thing is another story.
>

[Eric Greenwell]

In article >,
says...
I've never heard of a fatality, or even
> an accident during a 'contest finish' - either during
> a contest or at any other time, though I cannot say
> definitively that it's never happend.

Here are two I can definitively remember:

A fatality occurred after a low pass at California City contest a few
years ago.

There was a famous accident at our local regional many years ago,
where a pilot finished too slowly, pulled up, and flew through the
aerials on the Flight Service Station. No injury, limited damage, very
lucky.

> My personal experience
> (and statistics on the subject) suggests that we should
> be more concerned with too little speed (stall/spin)
> than too much speed.

The scary low passes I've seen were almost all done with too little
speed, which means when the pilot pulls up, he is still low, making a
pattern (any kind of pattern) to the landing more difficult.

--
!Replace DECIMAL.POINT in my e-mail address with just a . to reply
directly

Eric Greenwell
Richland, WA (USA)

[John Morgan]

"Eric Greenwell" > wrote in message
.. .
> In article >,
> says...
> The scary low passes I've seen were almost all done with too little
> speed, which means when the pilot pulls up, he is still low, making a
> pattern (any kind of pattern) to the landing more difficult.
>
> --
> !Replace DECIMAL.POINT in my e-mail address with just a . to reply
> directly
>
> Eric Greenwell
> Richland, WA (USA)


A "rule of thumb" I've used is 1 knot = about 9 feet. So if I start the
pull-up at 110 knots and push over to level for the pattern at about 60
knots, I'll be around 450 feet plus whatever altitude the low pass was flown
at.

I've done a few low passes at Napa, CA, a towered airport. I never ask when
there's other pattern traffic and so far the tower has always cleared me for
the low pass.

Disclaimer: the "formula" above isn't mine, don't know where I read it, it's
probably inaccurate, and don't try it at home . . . or in a glider for that
matter and try it at altitude first.
--
bumper >
"Dare to be different . . . circle in sink."
to reply, the last half is right to left




---
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[goneill]

The rule I use is simple
At ground level!
70knots to 90 knots I have enough energy for a 180degree turn
90 knots + I have energy for 360 degree turn.
THESE ARE ABSOLUTE MINIMUMS.
I add 10-20knots to avoid a case of "brown adrenalin"
These figures are calculated on Cirrus,Libelle,Asw19 type aircraft
so later generation gliders gain on on these figures
I REPEAT I ADD 10-20 KNOTS FOR SAFETY
These figures were calculated about by a well known pilot
15-20 years whose name I cannot recall.
gary
"John Morgan" > wrote in message
...
>
> "Eric Greenwell" > wrote in message
> .. .
> > In article >,
> > says...
> > The scary low passes I've seen were almost all done with too little
> > speed, which means when the pilot pulls up, he is still low, making a
> > pattern (any kind of pattern) to the landing more difficult.
> >
> > --
> > !Replace DECIMAL.POINT in my e-mail address with just a . to reply
> > directly
> >
> > Eric Greenwell
> > Richland, WA (USA)
>
>
> A "rule of thumb" I've used is 1 knot = about 9 feet. So if I start the
> pull-up at 110 knots and push over to level for the pattern at about 60
> knots, I'll be around 450 feet plus whatever altitude the low pass was
flown
> at.
>
> I've done a few low passes at Napa, CA, a towered airport. I never ask
when
> there's other pattern traffic and so far the tower has always cleared me
for
> the low pass.
>
> Disclaimer: the "formula" above isn't mine, don't know where I read it,
it's
> probably inaccurate, and don't try it at home . . . or in a glider for
that
> matter and try it at altitude first.
> --
> bumper >
> "Dare to be different . . . circle in sink."
> to reply, the last half is right to left
>
>
>
>
> ---
> Outgoing mail is certified Virus Free.
> Checked by AVG anti-virus system (http://www.grisoft.com).
> Version: 6.0.514 / Virus Database: 312 - Release Date: 9/1/2003
>
>

[Tom Seim]

Andy Blackburn > wrote in message >...
> Tom,
> I took a look at your references -- by N#. The first
> and third appear to be low passes - though in both
> cases they were in the context of doing low-altitude
> aerobatics, rather than traditional 'contest finish'
> maneuvers, but I'll let them pass. The reports on the
> second and fourth had no references to low, fast passes.
> The BG-12 lost a wing at 2000' and the Blanik was just
> high on approach. (Excerpts from the accident reports
> attached).
>
> Your formula for estimating accident rate by phase
> of flight seems ok, but you have to be careful about
> making conclusions from VERY low rates of occurence
> (i.e. one every ten years). Also, I would disagree
> with your estimate of 1,000 operations for
> high-speed passes in the US in a year. The Arizona
> Soaring Association weekend contest series generates
> over 200 contest finishes in a summer - and that's
> just one soaring site. Add all the other sites in the
> US, plus sanctioned contests and you get a much bigger
> number. Finally, you used 9 years for the time period,
> but your examples spanned 19 years (1984 to present).
> Given the low rate of occurence, I emphasize that calculating
> a rate is likely to be misleading. The rates associated
> with landing phase would seem to be higher, since there
> we have several per year.
>
> In any event, I remain unconvinced that making contest
> finishes is inherently dangerous, particularly now
> that the evidence in favor of the argument has been
> presented.
>

Those two accidents were mostly caused by a badly botched attempt at a
hihg-speed low pass. The pilot of the BG-12 exceeded Vne; why did he
do that entering the pattern? The only ligit explanation, in my mind,
is that he was starting a low pass and didn't pay attention to
airspeed. The other one was very curious. They described a high pass,
yet he hit A/C on the ground! These two statements are completely
inconsistent:

WITNESSES REPORTED THAT THE ACFT APPEARED TO BE TOO
HIGH, TOO FAST, AND IN A CRAB AS IT APPROACHED THE
RWY. OVER THE RWY THE GLIDER WAS OBSERVED TO ROLL INTO
A RIGHT TURN AS THE NOSE CAME UP. SHORTLY THEREAFTER
THE RIGHT WING STRUCK 3 PARKED ACFT AND COLLIDED WITH
THE TERRAIN.

I concluded that the glider wasn't as high as the witnesses thought
(surprise!) and that he was doing a show off low pass for his
passenger (surprise again).

The accident rate calculation is illustrative, giving an order of
magnitude to the situation. You can adjust the calculation by
assigning an educated probability to the accident falling in this
category; it doesn't change things materially. If you compare this,
small, category to all fatal accidents it is totally out of proportion
by any measure.

Your attitude from the outset has been "show me!". I've been in this
sport a long time (over 20 years), and that's a red flag attitude in
my book. I'm sure you've seen pilots who over estimate their
capabilities, given your resume. I've grown more conservative in my
old age (old pilots vs bold pilots). I say to you, show me how it is
safe, considering ALL conditions, such as pilot capabilities and
surroundings (i.e. glider only A/P vs GA A/P). The bottom line is: is
it worth it? Are you going to assume an avoidable risk vs a quick
thrill? My message isn't to you guys (you're already to emotionally
invested in proving me wrong), its to low time pilots who are
wondering what's this all about. Do I really have to explain what is
wrong with showing off? Are you guys so thick skulled as to not see a
problem with that kind of attitude? If so I hope I don't see your name
on an NTSB report. I have said it before: I would rather have someone
****ed off at me for voicing my oppinion than to stand silent and
watch them kill themselves. Personally, given your background I am
surprised at your attitude. I will consider my comments a complete
success if I have thrown a note of caution into just a single pilot,
or pilot to be, that has followed this exchange.

BTW: Go for the glass!