Setting altimeters with no radio

"Denny" wrote in message
ups.com...
My filter failed and this message popped up... Not an issue of any
importance in itself and fixed again with two mouse clicks...
However, seeing the list of you tripping over yourselves to answer his
trolling have me howling with laughter...

If pilots don't know the answer, then he's asking a good question.

I've objected to some of his posts in the past, but there's no point in
objecting when his posts are reasonable.

--Gary

"TxSrv" wrote in message
. ..

That Reg does not apply to flight within 3,000 above the surface. You have
to look at two other Regs to conclude that. Therefore, under 3,000, an
adjustable altimeter is not required per 91.205. FARs don't apply to you;
stay away.


An altimeter adjustable for barometric pressure is not required for VFR
flight at any altitude.

If you're operating at any altitude below 18,000 feet and you're equipped
with a radio and you have an altimeter adjustable for barometric pressure
you must set it to the current reported altimeter setting of an appropriate
available station, VFR and IFR.

Stefan wrote:

The only use for GPS altitude in aviation is to calculate the final
glide of a glider. (Or an IFR approach, but I don't know enough about
IFR flight to comment this.)

Most of what you said is correct except this one. My belief is that
GPS altitude is fine for terrain separation. But not for aircraft
separation which you correctly state is based upon pressure altitude.

Ron Lee

Mxsmanic wrote:

GPS is routinely off by hundreds of feet.

With SA off the vertical error is probably better that altimeter
accuracy requirements. At least close enough for most users and if
you can get WAAS corrections it is very good.

Ron Lee

"Ron Lee" wrote in message
...
Stefan wrote:

The only use for GPS altitude in aviation is to calculate the final
glide of a glider. (Or an IFR approach, but I don't know enough about
IFR flight to comment this.)

Most of what you said is correct except this one. My belief is that
GPS altitude is fine for terrain separation. But not for aircraft
separation which you correctly state is based upon pressure altitude.

Ron Lee

Your belief is wrong. Could be DEAD wrong. Read MX's posts...........he can
give you an education on this subject.

Karl

Mxsmanic wrote in
:

Since it is possible to fly without voice radio equipment, and given
that (if I understand correctly) pilots are supposed to have their
altimeters set correctly to a reference located not more than 100
miles from their position, how does an aircraft without a radio keep
its altimeter properly set as it travels?


Set it to field elevation of the departure airport before you take off. Or
if you want you can do a time distance formula, just point the nose
straight down and when your airspeed stabalizes note indicated altitude and
start time. The clock should stop on inpact, just multiply the time it
took by your airspeed, convert the distance to feet. Now find the
differance between your figure and the altitude you started time at and you
have your correction. Unfortunatly you dont die in a sim.

"karl gruber" wrote:


"Ron Lee" wrote in message
...
Stefan wrote:

The only use for GPS altitude in aviation is to calculate the final
glide of a glider. (Or an IFR approach, but I don't know enough about
IFR flight to comment this.)

Most of what you said is correct except this one. My belief is that
GPS altitude is fine for terrain separation. But not for aircraft
separation which you correctly state is based upon pressure altitude.

Ron Lee

Your belief is wrong. Could be DEAD wrong. Read MX's posts...........he can
give you an education on this subject.

Not sure what he can help on since I understand GPS quite well. I
also fly in mountainous terrain which I doubt that he does.

Ron Lee

mike regish writes:

Do those amounts vary with location?

Yes, but unfortunately that is only one of the variables. They also
vary dramatically with the changing positions of the satellites above
(and the satellites move significantly from one minute to the next).
Atmospheric conditions and other factors also come into play.

Overall, though, the problem is that the satellites are positioned to
optimize lateral navigation--but that also positions them in a way
that is unfavorable to vertical navigation. The vertical accuracy can
never be as high as the lateral accuracy; it can't even come close.
That's the way the system is designed.

Perhaps one day GPS will provide altitudes accurate to within a few
feet; but if it does, then by that time the lateral positions will be
accurate to within millimeters.

How large a difference is there between the 2?

It varies by location and conditions. I'm not sure of the exact
differences. One problem is that the geoid altitude is fixed, whereas
pressure altitudes depend on atmospheric conditions.

If everyone used GPS for altitude, it would probably work out okay in
some cases, particularly at high altitudes. But as long as anyone is
using a conventional altimeter, the differences are large enough to be
dangerous.

But you're right. If that's true, and I don't doubt it is, GPS would be
better suited to terrain avoidance and less so to aircraft separation.

I prefer to reserve GPS for lateral navigation only. For that it
works quite well, on a par with other navaids (depending on various
factors). For altitude it's a waste of time. Better to have a
standard altimeter and a radar altimeter for terrain.

--
Transpose mxsmanic and gmail to reach me by e-mail.

Ron Lee writes:

With SA off the vertical error is probably better that altimeter
accuracy requirements.

No. The figure of hundreds of feet is with SA OFF. It's even worse
with SA on.

At least close enough for most users and if
you can get WAAS corrections it is very good.

If you have external corrections, you can do far better. But you're
still at least as well off with a standard altimeter. At least right
now, you don't really gain anything for altitude measurement with GPS.

--
Transpose mxsmanic and gmail to reach me by e-mail.

mike regish writes:

Dang. I actually learned something from this post.

You've also learned about GPS.

--
Transpose mxsmanic and gmail to reach me by e-mail.