Is Flying AGL Legal?

I am a member of two local soaring organizations and work with several
others. Most organizations fly MSL. A few teach flying AGL. It was
pointed out at one meeting that flying MSL is illegal if you read FAR
91.121 (shown below). They also mentioned that if you crash and the
NTSB says your altimeter was set wrong, then your insurance (life
and/or hull) may not pay up.

At least one CFIG at the club that teaches AGL says that gliders do not
fly "cruising altitude or flight level" and thus this FAR does not
apply.

What is your opinion? I offer none of my own at this point.

Thanks, John

===============

FAR Sec. 91.121

Altimeter settings.

(a) Each person operating an aircraft shall maintain the cruising
altitude or flight level of that aircraft, as the case may be, by
reference to an altimeter that is set, when operating--
(1) Below 18,000 feet MSL, to--
(i) The current reported altimeter setting of a station along the route
and within 100 nautical miles of the aircraft;
(ii) If there is no station within the area prescribed in paragraph
(a)(1)(i) of this section, the current reported altimeter setting of an
appropriate available station; or
(iii) In the case of an aircraft not equipped with a radio, the
elevation of the departure airport or an appropriate altimeter setting
available before departure; or
(2) At or above 18,000 feet MSL, to 29.92'' Hg.
(b) The lowest usable flight level is determined by the atmospheric
pressure in the area of operation as shown in the following table:

Current altimeter setting Lowest usable flight level
29.92 (or higher) 180
29.91 through 29.42 185
29.41 through 28.92 190
28.91 through 28.42 195
28.41 through 27.92 200
27.91 through 27.42 205
27.41 through 26.92 210

(c) To convert minimum altitude prescribed under Secs. 91.119 and
91.177 to the minimum flight level, the pilot shall take the flight
level equivalent of the minimum altitude in feet and add the
appropriate number of feet specified below, according to the current
reported altimeter setting:

Current altimeter setting Adjustment factor
29.92 (or higher) None
29.91 through 29.42 500
29.41 through 28.92 1,000
28.91 through 28.42 1,500
28.41 through 27.92 2,000
27.91 through 27.42 2,500
27.41 through 26.92 3,000

ContestID67 wrote:
I am a member of two local soaring organizations and work with several
others. Most organizations fly MSL. A few teach flying AGL. It was
pointed out at one meeting that flying MSL is illegal if you read FAR
91.121 (shown below). They also mentioned that if you crash and the
NTSB says your altimeter was set wrong, then your insurance (life
and/or hull) may not pay up.

At least one CFIG at the club that teaches AGL says that gliders do not
fly "cruising altitude or flight level" and thus this FAR does not
apply.

What is your opinion? I offer none of my own at this point.

Thanks, John

John,

There was a pretty good discussion of this subject here last year.
Seach for QFE and QNH and you will probably find all the argument you
need!

I think you have it backwards about MSL vs AGL - The FARs would tend
towards stating that flying AGL (i.e. altimeter set so that when on the
ground, it reads zero) is illegal, and that you are required to set the
altimeter to the best local setting - that makes the altimeter
inticate your altitude MSL (field elevation on the ground).

I think the argument about gliders not having a cruise altitude is
bogus - the point is to be able to avoid other aircraft cruising at VFR
hemispheric altitudes that you are descending or climbing through; by
knowing where to look. Hard to do with your altimeter set on QFE!

Kirk
MSL/QNH all the way.

I mispoke and you are correct. AGL is illegal per the FARs per my
reading. Also I agree that the cruise altitude argument is a
non-started. I will search for QFE and QNH. Thanks.

Anyone who thinks 91.121 mandates AGL altimeter settings needs to take
a course in remedial reading.

1) At our field you cannot set the altimeter to "Zero" for AGL flying, the
altimeter does not adjust that far.
2) We fly close to Class B airspace and under Class B "Shelves", how can you
knowingly stay out of Class B if you do not know the MSL altitude that Class
B is defined by and it becomes your ceiling.
3) We fly in mountainous to hilly terrain. How do you know you have glide
made above a distant ridge line between you and "home".
4) We fly in mountainous to hilly terrain. All charted land out areas away
from "home" are known by MSL altitudes, how do you know you have final glide
made to those safe havens.
5) (ALL of 5 is not an argument) Stating that gliders do not fly "set
cruise altitudes" is not an argument. How do you know what MSL altitude you
are at and "hopefully" that powered aircraft in cruise will be coming from
which direction based on what cruise altitude... you don't know what the
altitude is because you attempted to fly zero setting. Powered aircraft
pilots do not diligently fly proper cruise altitudes either.

BT

"ContestID67" wrote in message
oups.com...
I am a member of two local soaring organizations and work with several
others. Most organizations fly MSL. A few teach flying AGL. It was
pointed out at one meeting that flying MSL is illegal if you read FAR
91.121 (shown below). They also mentioned that if you crash and the
NTSB says your altimeter was set wrong, then your insurance (life
and/or hull) may not pay up.

At least one CFIG at the club that teaches AGL says that gliders do not
fly "cruising altitude or flight level" and thus this FAR does not
apply.

What is your opinion? I offer none of my own at this point.

Thanks, John

===============

FAR Sec. 91.121

Altimeter settings.

(a) Each person operating an aircraft shall maintain the cruising
altitude or flight level of that aircraft, as the case may be, by
reference to an altimeter that is set, when operating--
(1) Below 18,000 feet MSL, to--
(i) The current reported altimeter setting of a station along the route
and within 100 nautical miles of the aircraft;
(ii) If there is no station within the area prescribed in paragraph
(a)(1)(i) of this section, the current reported altimeter setting of an
appropriate available station; or
(iii) In the case of an aircraft not equipped with a radio, the
elevation of the departure airport or an appropriate altimeter setting
available before departure; or
(2) At or above 18,000 feet MSL, to 29.92'' Hg.
(b) The lowest usable flight level is determined by the atmospheric
pressure in the area of operation as shown in the following table:

Current altimeter setting Lowest usable flight level
29.92 (or higher) 180
29.91 through 29.42 185
29.41 through 28.92 190
28.91 through 28.42 195
28.41 through 27.92 200
27.91 through 27.42 205
27.41 through 26.92 210

(c) To convert minimum altitude prescribed under Secs. 91.119 and
91.177 to the minimum flight level, the pilot shall take the flight
level equivalent of the minimum altitude in feet and add the
appropriate number of feet specified below, according to the current
reported altimeter setting:

Current altimeter setting Adjustment factor
29.92 (or higher) None
29.91 through 29.42 500
29.41 through 28.92 1,000
28.91 through 28.42 1,500
28.41 through 27.92 2,000
27.91 through 27.42 2,500
27.41 through 26.92 3,000

"ContestID67" wrote in message
oups.com...
They also mentioned that if you crash and the
NTSB says your altimeter was set wrong, then your insurance (life
and/or hull) may not pay up.

This is mostly a "boogey man" argument.

IF the insurance company could prove that the altimeter setting was
knowingly set wrong by the pilot, and IF they could prove that the direct cause
of the accident was that altimeter setting then PERHAPS they would have a case,
(depending on your state law and the actual words in your insurance contract).
If insurance investigators actually showed up after every accident to comb the
debris for some tiny FAR violation to "automatically" void the insurance, there
would be no point in buying insurance.

Your insurance normally pays even when you are in the wrong, even when you
do something stupid; that is what it is there for, that is what you pay for.

Flying AGL is pretty much mantitory. Attemps to fly below ground level are
often fatal.

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
Spell checking is left as an excercise for the reader.

ContestID67 wrote:
I am a member of two local soaring organizations and work with several
others. Most organizations fly MSL. A few teach flying AGL. It was
pointed out at one meeting that flying MSL is illegal if you read FAR
91.121 (shown below). They also mentioned that if you crash and the
NTSB says your altimeter was set wrong, then your insurance (life
and/or hull) may not pay up.

At least one CFIG at the club that teaches AGL says that gliders do not
fly "cruising altitude or flight level" and thus this FAR does not
apply.

What is your opinion? I offer none of my own at this point.

Thanks, John

===============

FAR Sec. 91.121

Altimeter settings.

(a) Each person operating an aircraft shall maintain the cruising
altitude or flight level of that aircraft, as the case may be, by
reference to an altimeter that is set, when operating--
(1) Below 18,000 feet MSL, to--
(i) The current reported altimeter setting of a station along the route
and within 100 nautical miles of the aircraft;
(ii) If there is no station within the area prescribed in paragraph
(a)(1)(i) of this section, the current reported altimeter setting of an
appropriate available station; or
(iii) In the case of an aircraft not equipped with a radio, the
elevation of the departure airport or an appropriate altimeter setting
available before departure; or
(2) At or above 18,000 feet MSL, to 29.92'' Hg.
(b) The lowest usable flight level is determined by the atmospheric
pressure in the area of operation as shown in the following table:

Current altimeter setting Lowest usable flight level
29.92 (or higher) 180
29.91 through 29.42 185
29.41 through 28.92 190
28.91 through 28.42 195
28.41 through 27.92 200
27.91 through 27.42 205
27.41 through 26.92 210

(c) To convert minimum altitude prescribed under Secs. 91.119 and
91.177 to the minimum flight level, the pilot shall take the flight
level equivalent of the minimum altitude in feet and add the
appropriate number of feet specified below, according to the current
reported altimeter setting:

Current altimeter setting Adjustment factor
29.92 (or higher) None
29.91 through 29.42 500
29.41 through 28.92 1,000
28.91 through 28.42 1,500
28.41 through 27.92 2,000
27.91 through 27.42 2,500
27.41 through 26.92 3,000

Flying "AGL" may be open to interpretation, but I assure you that
flying "BGL" will surely attract somebody's attention :-)

On Sun, 19 Mar 2006 04:13:50 UTC, "Mark628CA"
wrote:

Flying "AGL" may be open to interpretation, but I assure you that
flying "BGL" will surely attract somebody's attention :-)

I once did eight miles at 10 - 200' BGL on mybway back to Sutton Bank.

Ian


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