Reserve altitude

On Friday, May 26, 2017 at 8:46:28 AM UTC-4, MNLou wrote:
Hi Evan -

Would you please expand a bit on why you think it is better to set reserve altitude to zero?

Thanks!

Lou

Uh, sure. This is a semi-religious issue, so opinions will vary. Here's my $0.02 on a rainy day:

Conditions vary. Airport environments vary. I happen to fly in a region of the world (Northern New England) that features a lot of terrain that runs between poorly landable and completely unlandable, and weather than runs from benign to a crash-waiting-to-happen. While my environment is more challenging than many, yours isn't uniform, either.

So, the basic point is: there is no one standard reserve height that is appropriate in all situations. You as PIC need to be making decisions based on environment, current conditions & anything else that affects safety of flight. The computer is your assistant, not your decision maker.

For example: At my home airport (also DC's home airport) our traffic pattern is high due to surrounding terrain and your final glide ought to be padded well beyond this because there is simply no safe place to land other than the airport for a radius of about 5 miles (and then only one or two places, not necessarily where you want them!). Furthermore, the "safe" (that is, landable) route into my home airport follows a river valley which often features a) valley winds and b) subsiding air. I'm usually looking for 1500' over an MC 2.0 (kts) final glide from 25 out, based on the airport elevation. When I was learning to fly XC here, it was more like 2000 over.

This is total overkill at a million flat lands airports.

The obvious, simple solution is to set your flight computer to report estimated arrival height at any destination without any reserve, then do the PIC decision making thing. For old Cambridge gear, that's trivial. For ClearNav, there's one gotcha involved (easily handled, set the purple amoeba to zero and the red one to 1000 agl), for SN-10, you have to build yourself a whole new database with fake-news airport elevations (yes, people really do this, I've watched).

Go fast, make good decisions, land safe!

best,
Evan Ludeman / T8

I agree with Evan.

But why not get the guys at LXNav, Naviter,
LXNavigation, to call it arrival "height" and reserve
"height" if you must have it? Which imho is what it is
displayed, and this more precise terminology might
remove at least one source of confusion.

While you're at it, Waypoints have Elevation, perhaps.



At 14:08 26 May 2017, Tango Eight wrote:
On Friday, May 26, 2017 at 8:46:28 AM UTC-4, MNLou
wrote:
Hi Evan -=20
=20
Would you please expand a bit on why you think it is
better to set
reserv=
e altitude to zero?
=20
Thanks!
=20
Lou

Uh, sure. This is a semi-religious issue, so opinions will
vary. Here's
m=
y $0.02 on a rainy day:

Conditions vary. Airport environments vary. I happen
to fly in a region
o=
f the world (Northern New England) that features a lot
of terrain that
runs=
between poorly landable and completely unlandable,
and weather than runs
f=
rom benign to a crash-waiting-to-happen. While my
environment is more
chal=
lenging than many, yours isn't uniform, either.

So, the basic point is: there is no one standard reserve
height that is
app=
ropriate in all situations. You as PIC need to be making
decisions based
o=
n environment, current conditions & anything else that
affects safety of
fl=
ight. The computer is your assistant, not your decision
maker.

For example: At my home airport (also DC's home
airport) our traffic
patter=
n is high due to surrounding terrain and your final glide
ought to be
padde=
d well beyond this because there is simply no safe
place to land other
than=
the airport for a radius of about 5 miles (and then only
one or two
places=
, not necessarily where you want them!). Furthermore,
the "safe" (that
is,=
landable) route into my home airport follows a river
valley which often
fe=
atures a) valley winds and b) subsiding air. I'm usually
looking for
1500'=
over an MC 2.0 (kts) final glide from 25 out, based on
the airport
elevati=
on. When I was learning to fly XC here, it was more
like 2000 over.=20

This is total overkill at a million flat lands airports.=20

The obvious, simple solution is to set your flight
computer to report
estim=
ated arrival height at any destination without any
reserve, then do the
PIC=
decision making thing. For old Cambridge gear, that's
trivial. For
Clear=
Nav, there's one gotcha involved (easily handled, set
the purple amoeba to
=
zero and the red one to 1000 agl), for SN-10, you have
to build yourself a
=
whole new database with fake-news airport elevations
(yes, people really
do=
this, I've watched).

Go fast, make good decisions, land safe!

best,
Evan Ludeman / T8

I also set reserve to zero. Remembering which reserve altitude is set for the glide to turnpoint, glide to alternates, glide to finish, and the two amoebas (clearnav) is too much for me. So I set them all to zero. If I want to arrive at 1000', I don't proceed unless it says 1000' (plus a decent macCready). The one exception is the finish -- if it's a contest finish and the arrival height is 1000' MSL, then I set that to 1000' MSL, which is the logical equivalent of zero.

John Cochrane BB

I prefer setting an appropriate pattern entry altitude for the simple reason that many places I fly have a ridge or other high obstacle to clear before I get home. The LX9000 software will show if my current final glide will clear the offending obstacle. Granted, it isn't full proof, but it gives a general idea. Setting the reserve to zero negates this feature.
Craig

On Saturday, May 27, 2017 at 5:18:24 PM UTC-7, Craig Reinholt wrote:
I prefer setting an appropriate pattern entry altitude for the simple reason that many places I fly have a ridge or other high obstacle to clear before I get home. The LX9000 software will show if my current final glide will clear the offending obstacle. Granted, it isn't full proof, but it gives a general idea. Setting the reserve to zero negates this feature.
Craig

I agree with Craig and John.

1) I don't like the idea of setting up a final glide where I get no indication if the calculation works out that I will clear a ridge by 1 foot. I'd like to know if it's going to be close.

2) Most contest finish cylinders are 1000' - the scoring equivalent of ground level (sort of).

Therefore 1000' reserve is what I use. If I have a half-decent climb I will go to at least Mc=4 plus an additional 500-1000'.

Andy Blackburn
9B

On Sunday, May 28, 2017 at 9:17:29 AM UTC+3, Andy Blackburn wrote:
On Saturday, May 27, 2017 at 5:18:24 PM UTC-7, Craig Reinholt wrote:
I prefer setting an appropriate pattern entry altitude for the simple reason that many places I fly have a ridge or other high obstacle to clear before I get home. The LX9000 software will show if my current final glide will clear the offending obstacle. Granted, it isn't full proof, but it gives a general idea. Setting the reserve to zero negates this feature.
Craig

I agree with Craig and John.

1) I don't like the idea of setting up a final glide where I get no indication if the calculation works out that I will clear a ridge by 1 foot. I'd like to know if it's going to be close.

2) Most contest finish cylinders are 1000' - the scoring equivalent of ground level (sort of).

Therefore 1000' reserve is what I use. If I have a half-decent climb I will go to at least Mc=4 plus an additional 500-1000'.

Not having used one of these devices: if you set 1000' reserve and Mc=10, will you be at 1000 ft when you arrive, or after you pull up?

On Sunday, May 28, 2017 at 2:17:08 AM UTC-7, Bruce Hoult wrote:
On Sunday, May 28, 2017 at 9:17:29 AM UTC+3, Andy Blackburn wrote:
On Saturday, May 27, 2017 at 5:18:24 PM UTC-7, Craig Reinholt wrote:
I prefer setting an appropriate pattern entry altitude for the simple reason that many places I fly have a ridge or other high obstacle to clear before I get home. The LX9000 software will show if my current final glide will clear the offending obstacle. Granted, it isn't full proof, but it gives a general idea. Setting the reserve to zero negates this feature.
Craig

Not having used one of these devices: if you set 1000' reserve and Mc=10, will you be at 1000 ft when you arrive, or after you pull up?

My understanding is they have total energy in the calculation, but I believe they calculate finish height assuming you are still going at the STF for the McCready setting, so the total energy altitude adjustment is for deviations away from the Mc setting. Pushing and pulling on final glide ought not generate changes in estimated arrival altitude, unless you fly off-STF for a long time.

It's hardly ever well documented, so YMMV.

Andy Blackburn
9B

With ClearNav you can use the Amoebas as a good way of verifying ridge clearance. Set one amoeba to zero and the other to 1000 ft. Using the Amoebas for the ridge problem, allows the more sensible: reserve = 0 setting. Using the amoeba this way gives a visual / analog sense of clearance that is really better than a go/ no go. The width of the amoeba clearance through the pass or over the ridge provides a great indication of margin.