Runway Lengths

In article ,
(Ace Pilot) wrote:

I don't know anything about the engineering of runways, but it would
come as a surprise to me that modern methods (laser range finding,
GPS, etc.) couldn't pin down a runway length to within several inches.

Can one _define_ the "start" and the "end" of a runway to within several
inches? (seems to me paving or blacktop would roll off over several
inch range)

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FAA Advisory circulars 150/5300-13 and 150/5325 privide explaination of
runway lengths required based on aircraft capabilities.

AES/newspost wrote:

Can one _define_ the "start" and the "end" of a runway to within several
inches? (seems to me paving or blacktop would roll off over several
inch range)

Absolutely. You start the measuring wheel at the edge of the threshold mark and
stop it at pavement end.

George Patterson
To a pilot, altitude is like money - it is possible that having too much
could prove embarassing, but having too little is always fatal.

An Actual Fact (out of character for Usenet, but don't tell anybody) from a
friend who's an airport manager. I posed the group question, and his reply is:

"Most airports have that extra foot for insurance reasons. Aircraft insurance
policies for GA and corporate aircraft limit the operators to runways longer
than 3600 feet, 4000 feet, 5000 feet or whatever. So we build runways one foot
longer than what we think the insurance carriers require. The other requirement
that insurance carriers what are precision approaches. Aircraft owners of
turbines can get reduced premiums or are limited to use runways with precision
approaches."

"G.R. Patterson III" wrote:

AES/newspost wrote:

Can one _define_ the "start" and the "end" of a runway to within several
inches? (seems to me paving or blacktop would roll off over several
inch range)

Absolutely. You start the measuring wheel at the edge of the threshold mark
and
stop it at pavement end.

I obviously wasn't making any very great point here, other than that
"pavement end" might not be all that sharply defined, at least given my
observations of the edges of highway pavements, and more generally
measuring large physical things to 1 part in 5000, or 0.05% accuracy,
takes some care. To measure a 5000 foot runway to a precision of 1 foot
using a 2 foot diameter measuring wheel requires for example that the
diameter of said wheel be known to an accuracy of 5 mils = 0.005 inches,
including any dust or dirt layers it may pick up. I'd also note that if
the end of a 50 foot wide runway (I suppose that's a pretty wide runway
for some airports) is cut 1 degree off from perfectly square, the runway
is 1 foot longer on one side than on the other.

On 21 Oct 2003 02:44:05 GMT, (StellaStar) wrote:

An Actual Fact (out of character for Usenet, but don't tell anybody) from a
friend who's an airport manager.

Bringing Actual Facts into a newsgroup discussion is an unforgivable
breach of Usenet ethics.

all the best -- Dan Ford
email: www.danford.net/letters.htm#9

see the Warbird's Forum at www.warbirdforum.com
and the Piper Cub Forum at www.pipercubforum.com

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In article ,
AES/newspost wrote:

I obviously wasn't making any very great point here, other than that
"pavement end" might not be all that sharply defined, at least given my
observations of the edges of highway pavements, and more generally
measuring large physical things to 1 part in 5000, or 0.05% accuracy,
takes some care. To measure a 5000 foot runway to a precision of 1 foot
using a 2 foot diameter measuring wheel requires for example that the
diameter of said wheel be known to an accuracy of 5 mils = 0.005 inches,
including any dust or dirt layers it may pick up. I'd also note that if
the end of a 50 foot wide runway (I suppose that's a pretty wide runway
for some airports) is cut 1 degree off from perfectly square, the runway
is 1 foot longer on one side than on the other.

Differential GPS can measure down to 0.001 cm.
Laser rangefinding is comparable.

I would think it has more to do with the painting on the runway. The
length of the pavement seems to rarely correlate to the length of the
runway. ie over runs, thresholds, etc.

--
Kevin McCue
KRYN
'47 Luscombe 8E
Rans S-17 (for sale)




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"Steve Robertson" wrote in message
...
Never thought about that before. However, my guess is that it is to make
sure that aircraft insurance requirements as to minimum runway lenght for
certain types is exceeded rather than simply met.

Anybody else?

Best regards,
I think you are correct.
The posters talking about the tarmac getting longer/shorter, or other
similar ideas, are ignoring the fact that the published 'runway length',
rarely matches that of the actual surface. Most airports, do not have the
threshold painted exactly on the ends of the runway surface. A local
airfield to me, exactly meets the other type of example being given (with a
runway 1 foot under a round number), yet the actual surface extends over 50
feet past the threshold markings. Hence the markings have been deliberately
placed inside the physical runway length, and an insurance/physical planning
limitation on particular aircraft types, would seem to be the only logical
explanation.

Best Wishes

Steve Robertson
N4732J 1967 Beechcraft A23-24 Musketeer

Ace Pilot wrote:

Can anyone explain why runway lengths are sometimes "X thousand and
ONE feet" in length? I was just looking through a list of Iowa's
approximately 110 airports and 7 of them have runways that are "X
thousand and one feet" long.

Do runway manufacturing companies offer special deals like "Buy 5,000
feet of runway, get your next foot free!!!"

There's got to be a logical explanation - anyone know it?

"Kevin McCue" wrote in message ...
I would think it has more to do with the painting on the runway. The
length of the pavement seems to rarely correlate to the length of the
runway. ie over runs, thresholds, etc.


Maybe heavy braking on a hot day stretches the pavement? ;-)

Dan