FAR 91.171 interpretation

[James L. Freeman]

What is the point of the phrase "at the airport of intended departure"
in FAR 91.171(b)(1)?

Interpreted literally, it would mean that while the VOR check done
with a VOT is good for 30 days, it is only valid for departures from
the airport where it was done. That makes no sense. Any other
interpretation that I can think of would be the same with or without
that phrase. What were "they" thinking?

[ArtP]

On 15 Sep 2003 17:24:43 -0700, (James L. Freeman)
wrote:

>What is the point of the phrase "at the airport of intended departure"
>in FAR 91.171(b)(1)?
>
>Interpreted literally, it would mean that while the VOR check done
>with a VOT is good for 30 days, it is only valid for departures from
>the airport where it was done. That makes no sense. Any other
>interpretation that I can think of would be the same with or without
>that phrase. What were "they" thinking?

Without trying to justify the reason, it sounds like you are not
allowed to test the VOR on the ground and then truck the plane to a
different airport for departure and still have it count as a check.

[Ron Natalie]

"James L. Freeman" > wrote in message om...
> What is the point of the phrase "at the airport of intended departure"
> in FAR 91.171(b)(1)?

I always contended that it means you can't do the VOR check and
then either:
1. Have an uninteded departure.
2. Move the aircraft to some other airport before departure.

I think it's just fluff. The intent of the phrase is the same as if the
phrase wasn't ther.

[James Blakely]

And if you have an unintended departure, you have bigger problems than a
current VOR check.


"Ron Natalie" > wrote in message
m...
>
> "James L. Freeman" > wrote in message
om...
> > What is the point of the phrase "at the airport of intended departure"
> > in FAR 91.171(b)(1)?
>
> I always contended that it means you can't do the VOR check and
> then either:
> 1. Have an uninteded departure.
> 2. Move the aircraft to some other airport before departure.
>
> I think it's just fluff. The intent of the phrase is the same as if the
> phrase wasn't ther.
>
>

[Mike Granby]

"James L. Freeman" > wrote:

> What is the point of the phrase "at the airport
> of intended departure" in FAR 91.171(b)(1)?

Well, how about this? The identity of the airport cannot be the issue,
because departure is not previously referenced in the regulation (ie. it
doesn't start with "no person may depart...") and because, absent this more
specific definition, any airport at which you land must be an airport of
intended departure, or you'd never leave there! In other words, it doesn't
matter which airport it is relative to the flight. Therefore, the key must
be the fact that you are at the airport where the VOT or check point is
located, and that you are still on the ground. If you remove the phrase from
(b)(1) it looks to me like it would then allow you to circle around an
airport with a VOT, and test your receiver from the air. With the phrase
included, this is not permitted. The argument is a little weaker for (b)(2),
but again, without the phrase, you could (just about!) over-fly the
designated check-point rather than be on the ground.

--
Mike Granby, PP-ASEL,IA
Warrior N44578
http://www.mikeg.net/plane

[Ray Andraka]

Perhaps it is to prevent you from using a weak VOT signal from a nearby
airport. Can't think of any particular airports, but say your small airport or
private strip is located within reception range of the VOT at a nearby big
airport, this wording would not allow you to use the signal from that VOT (which
is not on the airport of intended departure).

Mike Granby wrote:

> "James L. Freeman" > wrote:
>
> > What is the point of the phrase "at the airport
> > of intended departure" in FAR 91.171(b)(1)?
>
> Well, how about this? The identity of the airport cannot be the issue,
> because departure is not previously referenced in the regulation (ie. it
> doesn't start with "no person may depart...") and because, absent this more
> specific definition, any airport at which you land must be an airport of
> intended departure, or you'd never leave there! In other words, it doesn't
> matter which airport it is relative to the flight. Therefore, the key must
> be the fact that you are at the airport where the VOT or check point is
> located, and that you are still on the ground. If you remove the phrase from
> (b)(1) it looks to me like it would then allow you to circle around an
> airport with a VOT, and test your receiver from the air. With the phrase
> included, this is not permitted. The argument is a little weaker for (b)(2),
> but again, without the phrase, you could (just about!) over-fly the
> designated check-point rather than be on the ground.
>
> --
> Mike Granby, PP-ASEL,IA
> Warrior N44578
> http://www.mikeg.net/plane

--
--Ray Andraka, P.E.
President, the Andraka Consulting Group, Inc.
401/884-7930 Fax 401/884-7950
email
http://www.andraka.com

"They that give up essential liberty to obtain a little
temporary safety deserve neither liberty nor safety."
-Benjamin Franklin, 1759

[Mike Granby]

"Ray Andraka" > wrote:

> Perhaps it is to prevent you from using a
> weak VOT signal from a nearby airport.

Good point. The key is that you have to be at the airport where the VOT or
checkpoint is located.

--
Mike Granby, PP-ASEL,IA
Warrior N44578
http://www.mikeg.net/plane

[John Harper]

I just got round to looking this one up, and I have a question... 91.171(b)
is clear about "airport of intended departure". But 91.171(c) says that if
you have two VOR receivers (which I guess any serious IFR airplane does)
then you can check them against each other IN PLACE OF ... (b). It
doesn't say anything about airports of intended departure, or VOTs,
or complicated airborne procedures.

I would interpret this to read that if I have a decent VOR signal on the
ground at an airport (without a designated checkpoint) - which I do
at my home airport - then a simple cross-check is OK for 91.171.
(And for sanity's sake checked also against the GPS, although of course
this is neither necessary nor sufficient for 91.171).

Anyone have thoughts on this or know a FSDO that thinks differently?

John

"James L. Freeman" > wrote in message
om...
> What is the point of the phrase "at the airport of intended departure"
> in FAR 91.171(b)(1)?
>
> Interpreted literally, it would mean that while the VOR check done
> with a VOT is good for 30 days, it is only valid for departures from
> the airport where it was done. That makes no sense. Any other
> interpretation that I can think of would be the same with or without
> that phrase. What were "they" thinking?

[Stan Gosnell]

"John Harper" > wrote in
news:1064079581.743889@sj-nntpcache-5:


> I would interpret this to read that if I have a decent VOR
> signal on the ground at an airport (without a designated
> checkpoint) - which I do at my home airport - then a simple
> cross-check is OK for 91.171.

Yep. We do this all the time. We have lots of helicopter
bases, not close to an airport, & the VOR's have to be checked
every 30 days, so we just tune in a VOR on both and cross-check
them. If we can't get a signal on the ground, a check in the
air will work.

--
Regards,

Stan