Tolerances - Published Minimum Altitudes

[John[_17_]]

If assigned IFR altitudes can be considered to have a tolerance of +/-
200 ft before you are "busted", what applies to published minimum
altitudes other than DH and MDA on approach plates? Most people will
say that you are not supposed to descend any amount below the DH/MDA
altitudes. Does this also apply to procedure turn altitudes,
transitions etc.? Is there a tolerance that is in effect +200 -0 that
applies?

In practical terms, whereas a decent of 100 ft below an assigned
altitude will cause no problems, is such a decent of 50-100' below a
published procedure turn altitude, transition altitude enough to get in
trouble?

John

[Hilton]

John,

Not really answering your question, but note that descending below DH is (by
definition if you think about it) legal even if you see absolutely nothing.
MDA means don't go below this altitude, but DH means make you decision here
and immediately start to get 'er going up which implies some time spent
below DH.

Hilton


"John" > wrote in message
...
> If assigned IFR altitudes can be considered to have a tolerance of +/- 200
> ft before you are "busted", what applies to published minimum altitudes
> other than DH and MDA on approach plates? Most people will say that you
> are not supposed to descend any amount below the DH/MDA altitudes. Does
> this also apply to procedure turn altitudes, transitions etc.? Is there a
> tolerance that is in effect +200 -0 that applies?
>
> In practical terms, whereas a decent of 100 ft below an assigned altitude
> will cause no problems, is such a decent of 50-100' below a published
> procedure turn altitude, transition altitude enough to get in trouble?
>
> John

[Everett M. Greene[_2_]]

John > writes:
> If assigned IFR altitudes can be considered to have a tolerance of +/-
> 200 ft before you are "busted", what applies to published minimum
> altitudes other than DH and MDA on approach plates? Most people will
> say that you are not supposed to descend any amount below the DH/MDA
> altitudes. Does this also apply to procedure turn altitudes,
> transitions etc.? Is there a tolerance that is in effect +200 -0 that
> applies?
>
> In practical terms, whereas a decent of 100 ft below an assigned
> altitude will cause no problems, is such a decent of 50-100' below a
> published procedure turn altitude, transition altitude enough to get in
> trouble?

[It's "descent", not "decent".]

The question for which I've never seen a definitive
answer is where is the reference point on the airplane
for measuring the altitude to which the MDA/DH applies?
It would seem that on the largest transport aircraft,
the cockpit would be at a substantially higher altitude
than the wheels on an approach. The wheels could all
but be on the ground while the cockpit is at 50 feet.
Visibility for the pilot is the controlling factor.
If a radar altimeter is the instrument determining
altitude for a low DH, is its reading compensated for
the aircraft attitude?

[Sam Spade]

John wrote:
> If assigned IFR altitudes can be considered to have a tolerance of +/-
> 200 ft before you are "busted", what applies to published minimum
> altitudes other than DH and MDA on approach plates? Most people will
> say that you are not supposed to descend any amount below the DH/MDA
> altitudes. Does this also apply to procedure turn altitudes,
> transitions etc.? Is there a tolerance that is in effect +200 -0 that
> applies?
>
> In practical terms, whereas a decent of 100 ft below an assigned
> altitude will cause no problems, is such a decent of 50-100' below a
> published procedure turn altitude, transition altitude enough to get in
> trouble?
>
> John

The practical test standards are simply wrong when it comes to MEAs or
any minimum altitude on an IAP.

The minimum is the minimum by law...period.

The only exception is not really an exception at all, DA. As a matter
of regulation DA does not have the word "minimum" associated with it.
Instead, at DA the decision must be made to continue descent with visual
reference or begin the missed approach.

[John[_17_]]

Sam Spade wrote:
> John wrote:
>> If assigned IFR altitudes can be considered to have a tolerance of +/-
>> 200 ft before you are "busted", what applies to published minimum
>> altitudes other than DH and MDA on approach plates? Most people will
>> say that you are not supposed to descend any amount below the DH/MDA
>> altitudes. Does this also apply to procedure turn altitudes,
>> transitions etc.? Is there a tolerance that is in effect +200 -0 that
>> applies?
>>
>> In practical terms, whereas a decent of 100 ft below an assigned
>> altitude will cause no problems, is such a decent of 50-100' below a
>> published procedure turn altitude, transition altitude enough to get
>> in trouble?
>>
>> John
>
> The practical test standards are simply wrong when it comes to MEAs or
> any minimum altitude on an IAP.
>
> The minimum is the minimum by law...period.
>
> The only exception is not really an exception at all, DA. As a matter
> of regulation DA does not have the word "minimum" associated with it.
> Instead, at DA the decision must be made to continue descent with visual
> reference or begin the missed approach.

This is in line with what I thought from a strictly legalistic
standpoint. But in practical real world terms, does this mean that if
you are hand flying an approach and say are in a procedure turn, you
will fly 100' above the published altitude to avoid going below? Or do
most ppl just fly the published altitude (I'm talking transition or PT
or something other than "close to the ground") and not worry about +/-
100 ft?

John

[Sam Spade]

John wrote:

> Sam Spade wrote:
>
>> John wrote:
>>
>>> If assigned IFR altitudes can be considered to have a tolerance of
>>> +/- 200 ft before you are "busted", what applies to published minimum
>>> altitudes other than DH and MDA on approach plates? Most people will
>>> say that you are not supposed to descend any amount below the DH/MDA
>>> altitudes. Does this also apply to procedure turn altitudes,
>>> transitions etc.? Is there a tolerance that is in effect +200 -0
>>> that applies?
>>>
>>> In practical terms, whereas a decent of 100 ft below an assigned
>>> altitude will cause no problems, is such a decent of 50-100' below a
>>> published procedure turn altitude, transition altitude enough to get
>>> in trouble?
>>>
>>> John
>>
>>
>> The practical test standards are simply wrong when it comes to MEAs or
>> any minimum altitude on an IAP.
>>
>> The minimum is the minimum by law...period.
>>
>> The only exception is not really an exception at all, DA. As a matter
>> of regulation DA does not have the word "minimum" associated with it.
>> Instead, at DA the decision must be made to continue descent with
>> visual reference or begin the missed approach.
>
>
> This is in line with what I thought from a strictly legalistic
> standpoint. But in practical real world terms, does this mean that if
> you are hand flying an approach and say are in a procedure turn, you
> will fly 100' above the published altitude to avoid going below? Or do
> most ppl just fly the published altitude (I'm talking transition or PT
> or something other than "close to the ground") and not worry about +/-
> 100 ft?
>
> John

I wouldn't worry about the regulation until passing the IF, where
obstacle clearance becomes 500 feet (perhaps less because of temperature
or other altimeter errors).

The PTS limits MDA to +100 feet, - zero feet, which is very important at
that point.

[Andrew Sarangan]

On May 9, 11:03 pm, John > wrote:
> If assigned IFR altitudes can be considered to have a tolerance of +/-
> 200 ft before you are "busted", what applies to published minimum
> altitudes other than DH and MDA on approach plates? Most people will
> say that you are not supposed to descend any amount below the DH/MDA
> altitudes. Does this also apply to procedure turn altitudes,
> transitions etc.? Is there a tolerance that is in effect +200 -0 that
> applies?
>
> In practical terms, whereas a decent of 100 ft below an assigned
> altitude will cause no problems, is such a decent of 50-100' below a
> published procedure turn altitude, transition altitude enough to get in
> trouble?
>
> John

Where is the +/-200ft tolerance specified except in the PTS? I've
heard many people refer to it, but could not find it in the FAR or AIM.

[Christopher Brian Colohan]

I am currently working through the King Schools IFR DVDs in
preparation for my US IFR written. Something is really bugging me,
and I figured someone here might know the answer.... (And I am too
impatient to wait for my next lesson.)

In one section of this course, we learn that the outer merker and
middle marker used to matter. It used to be the case that if they
were broken you had to increase your approach minimums by some amount.
But the King's don't think we have to know why your minimums used to
change, how the rule about minimums changed (other than getting
abolished), or why the rule changed -- simply that it no longer
matters any more, and you must know that since some FAA questions will
try to "trick" you by giving you the old rules (which I don't know
anyways) as potential answers.

They then go and devote a whole section of the course to suitable
substitutions for the broken devices. So now I know that if I want to
ignore the outer marker on an ILS, and it happens to be broken, it is
legal for me to substitute an NDB and ignore that instead.

So my question is twofold:

a) are marker beacons used for any real (regulatory) purpose any more,
or are they simply for positional awareness?

b) if the answer to (a) is "no, they are no longer used", why do we
have to memorize a set of rules about what we can legally substitute
for these unused beacons?

Chris

[Sam Spade]

Andrew Sarangan wrote:
> On May 9, 11:03 pm, John > wrote:
>
>>If assigned IFR altitudes can be considered to have a tolerance of +/-
>>200 ft before you are "busted", what applies to published minimum
>>altitudes other than DH and MDA on approach plates? Most people will
>>say that you are not supposed to descend any amount below the DH/MDA
>>altitudes. Does this also apply to procedure turn altitudes,
>>transitions etc.? Is there a tolerance that is in effect +200 -0 that
>>applies?
>>
>>In practical terms, whereas a decent of 100 ft below an assigned
>>altitude will cause no problems, is such a decent of 50-100' below a
>>published procedure turn altitude, transition altitude enough to get in
>>trouble?
>>
>>John
>
>
> Where is the +/-200ft tolerance specified except in the PTS? I've
> heard many people refer to it, but could not find it in the FAR or AIM.

It isn't.

[Bob Gardner]

"SUMMARY: The FAA is amending its regulations to reflect technological
advances that support area navigation (RNAV); include provisions on the use
of suitable RNAV systems for navigation; amend certain terms for consistency
with those of the International Civil Aviation Organization (ICAO); remove
reference to the middle marker in certain sections because a middle marker
is no longer operationally required; clarify airspace terminology; and
incorporate by reference obstacle departure procedures into Federal
regulations. The changes will facilitate the use of new navigation reference
sources, enable advancements in technology, and increase efficiency of the
National Airspace System."

The bottom line answer to your question is that the test writers in Oklahoma
City have always been several years behind the times. Take a knowledge test
today and you will be faced with black-and-white weather maps that require
diligent searching to find on the ADDS page...the color graphics that we use
every day have not yet been recognized by the test writers.

Bob Gardner


"Christopher Brian Colohan" > wrote in message
.. .
>I am currently working through the King Schools IFR DVDs in
> preparation for my US IFR written. Something is really bugging me,
> and I figured someone here might know the answer.... (And I am too
> impatient to wait for my next lesson.)
>
> In one section of this course, we learn that the outer merker and
> middle marker used to matter. It used to be the case that if they
> were broken you had to increase your approach minimums by some amount.
> But the King's don't think we have to know why your minimums used to
> change, how the rule about minimums changed (other than getting
> abolished), or why the rule changed -- simply that it no longer
> matters any more, and you must know that since some FAA questions will
> try to "trick" you by giving you the old rules (which I don't know
> anyways) as potential answers.
>
> They then go and devote a whole section of the course to suitable
> substitutions for the broken devices. So now I know that if I want to
> ignore the outer marker on an ILS, and it happens to be broken, it is
> legal for me to substitute an NDB and ignore that instead.
>
> So my question is twofold:
>
> a) are marker beacons used for any real (regulatory) purpose any more,
> or are they simply for positional awareness?
>
> b) if the answer to (a) is "no, they are no longer used", why do we
> have to memorize a set of rules about what we can legally substitute
> for these unused beacons?
>
> Chris

[Ronald Natalie]

Christopher Brian Colohan wrote:
> I am currently working through the King Schools IFR DVDs in
> preparation for my US IFR written. Something is really bugging me,
> and I figured someone here might know the answer.... (And I am too
> impatient to wait for my next lesson.)

How old are these DVD's?

>
> In one section of this course, we learn that the outer merker and
> middle marker used to matter. It used to be the case that if they
> were broken you had to increase your approach minimums by some amount.

It used to be that no middle marker gave you a 50 foot penalty. That
went away back in the late eighties. If they still talk about that,
they need to remove that.

The outer marker is specifically required by regulation. You can
substitute another fix that happens to be in the same place. Our local
TERPS expert can get into the why, but there's no particularly strong
reason other than the regs say it is a component of an ILS.

[Christopher Brian Colohan]

Ronald Natalie > writes:

> Christopher Brian Colohan wrote:
>> I am currently working through the King Schools IFR DVDs in
>> preparation for my US IFR written. Something is really bugging me,
>> and I figured someone here might know the answer.... (And I am too
>> impatient to wait for my next lesson.)
>
> How old are these DVD's?

About 2 months old.

>> In one section of this course, we learn that the outer merker and
>> middle marker used to matter. It used to be the case that if they
>> were broken you had to increase your approach minimums by some amount.
>
> It used to be that no middle marker gave you a 50 foot penalty. That
> went away back in the late eighties. If they still talk about that,
> they need to remove that.

What they say is roughly "this used to give you a penalty, but now it
doesn't. So one of the questions will have wrong answers talking
about the penalty this gives you, and you can ignore those wrong
answers."

> The outer marker is specifically required by regulation. You can
> substitute another fix that happens to be in the same place. Our
> local TERPS expert can get into the why, but there's no particularly
> strong reason other than the regs say it is a component of an ILS.

Ok.

Chris

[Kobra]

> It used to be that no middle marker gave you a 50 foot penalty. That
> went away back in the late eighties. If they still talk about that, they
> need to remove that.

I hate to sound stupid, but what exactly is this 50' penalty for a middle
marker--either now or in the past?

Kobra




>
> The outer marker is specifically required by regulation. You can
> substitute another fix that happens to be in the same place. Our local
> TERPS expert can get into the why, but there's no particularly strong
> reason other than the regs say it is a component of an ILS.
>

[Steven P. McNicoll[_2_]]

"Kobra" > wrote in message
. ..
>
> I hate to sound stupid, but what exactly is this 50' penalty for a middle
> marker--either now or in the past?
>

Decision height was increased by 50 feet if the marker was unavailable.