Question: Elevation --- RWY

Hello everybody,

I got a question regarding the so-called "elevation", i.e. the highest point of a runway. I have been told that the elevation is usually at the threshold, right before the touchdown zone, in order to ensure an easier take-off.
However, as airplanes land in the same direction as they take off, isn't the descending RWY a problem for landing? My (admittedly unprofessional) reasoning suggests that it would be better for aircraft to land on RWYs increasing in altitude.
Am I completely off the track? Any experts out there, please help ;-)

John

In article ,
john89 wrote:

Hello everybody,

I got a question regarding the so-called "elevation", i.e. the highest
point of a runway. I have been told that the elevation is usually at
the threshold, right before the touchdown zone, in order to ensure an
easier take-off.
However, as airplanes land in the same direction as they take off,
isn't the descending RWY a problem for landing? My (admittedly
unprofessional) reasoning suggests that it would be better for aircraft
to land on RWYs increasing in altitude.
Am I completely off the track? Any experts out there, please help ;-)

Don't forget that most runways are also used in both directions
depending on wind, so that a sloping runway which is uphill for takeoff
in one direction becomes downhill for takeoff in the other.

Most runways are roughly level. If the money is available and the
terrain is amenable enough to be able to decide that one point on the
runway should be the highest point, then it should be enough to decide
that the runway should be level altogether and not have a single highest
point. This is usually considered the goal of making a runway.

Many runways are only roughly level, and contain small but noticeable
slopes. This is especially true at smaller airports. These slopes are
usually hard to discern from the ground (although I'm sure people will
chime in with counterexamples here) and don't affect aircraft
performance significantly.

There are a few airports whose runways are significantly sloped. You are
correct that aircraft are better off taking off downhill and landing
uphill. On runways like this, the aircraft will do exactly that, and
thus will take off and land in opposite directions. In a case like this,
using the slope appropriately is more important than operating into the
wind, so the typical performance reason for taking off and landing in
the same direction isn't there.

So in short, most runways are more or less level, and so takeoff/landing
direction isn't determined by slope. When the slope is significant, take
off downhill, land uphill.

--
Mike Ash
Radio Free Earth
Broadcasting from our climate-controlled studios deep inside the Moon

On Aug 10, 2:41*pm, john89 wrote:
I have been told that the elevation is usually at the threshold, right before
the touchdown zone, in order to ensure an easier take-off.


Field elevation is the elevation of the highest point on the usable
portion of the runway(s). Its location can't be assumed, and the only
place I've ever seen it precisely indicated is on geodetic survey maps.

On Aug 11, 5:50*am, Mike Ash wrote:
In article ,

Many runways are only roughly level, and contain small but noticeable
slopes. This is especially true at smaller airports. These slopes are
usually hard to discern from the ground (although I'm sure people will
chime in with counterexamples here)


I seem to remember that the runway in my hometown Bangalore had its
maximum elevation at roughly the center


and don't affect aircraft performance significantly.


From what I've heard, (a) aircraft are certified for a 2% slope and
(b) you're barred from employing flexible takeoffs where the runway is
sloped (I don't know if this applies to *any* slope).

The other aspect this influences - and I think this doesn't apply for
GA aircraft - is the maximum takeoff weight. FAR 121.189(e) mentions
runway gradient as a factor in MTOW calculations.

Ramapriya

"john89" wrote in message
...

Hello everybody,

I got a question regarding the so-called "elevation", i.e. the highest
point of a runway. I have been told that the elevation is usually at
the threshold, right before the touchdown zone, in order to ensure an
easier take-off.
However, as airplanes land in the same direction as they take off,
isn't the descending RWY a problem for landing? My (admittedly
unprofessional) reasoning suggests that it would be better for aircraft
to land on RWYs increasing in altitude.
Am I completely off the track? Any experts out there, please help ;-)

John

http://204.108.4.16/d-tpp/0908/00769IL9.PDF


An IFR chart will gir you the touchdown elevation for the runway your
landing on.



--
john89

On 11 Aug, 04:54, "Ron Reagun" wrote:
"john89" wrote in message

...





Hello everybody,

I got a question regarding the so-called "elevation", i.e. the highest
point of a runway. I have been told that the elevation is usually at
the threshold, right before the touchdown zone, in order to ensure an
easier take-off.
However, as airplanes land in the same direction as they take off,
isn't the descending RWY a problem for landing? My (admittedly
unprofessional) reasoning suggests that it would be better for aircraft
to land on RWYs increasing in altitude.
Am I completely off the track? Any experts out there, please help ;-)

John

http://204.108.4.16/d-tpp/0908/00769IL9.PDF

An IFR chart will gir you the touchdown elevation for the runway your
landing on.

Here is one where you land uphill and takeoff
downhill - everytime.

http://www.youtube.com/watch?v=uNFNFZq2BFY
Courchevel, France.

http://www.youtube.com/watch?v=LDY1-...eature=related

Here is the biggest visitor I can find.
De Havilland Canada DHC-7-102 Dash 7
http://www.airliners.net/photo/Tyrol...bd7361540d25e9

Rumours of a Citation.

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bod43 wrote:

Here is one where you land uphill and takeoff
downhill - everytime.

http://www.youtube.com/watch?v=uNFNFZq2BFY
Courchevel, France.

Another:

http://www.jetphotos.net/viewphoto.php?id=152136
http://www.airliners.net/photo/0364044/M/

Tenzing/Hillary airport, Lukla, Nepal. If you miss it, you
won't have a chance to go around.

BL.
- --
Brad Littlejohn | Email:
Unix Systems Administrator, |
Web + NewsMaster, BOFH.. Smeghead! | http://www.wizard.com/~tyketto
PGP: 1024D/E319F0BF 6980 AAD6 7329 E9E6 D569 F620 C819 199A E319 F0BF

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Thanks a lot guys,

very detailled and informative answers!
Apparently there are just now "absolute" true rules such as:

Airplanes always land in the same direction as they took off.
Airplanes take off downhills and land uphills.
Airplanes both take off and land with headwind. etc...

Alas, no rule without exception ;-)

Still, the elevation of the RWY being in its centre (as claimed by D Ramapriya) still denies any logic as far as I can see.

John

john89 schreef:

Alas, no rule without exception ;-)


That's true enough, but on top of that the rules that do exist have
their bounds, geographical or other.
One example: here in Belgium, we have the notion of an "active runway"
and this is communicated either per radio (on controlled aerodromes) or
in the signal square. But in France the concept of an active runway is
not universally applied (to say the least), I remember hearing a
visiting pilot inquiring what run runway to use, and getting for answer
"ah, you know, there's not too much wind, you just pick the 12 or 30 as
you prefer..."


KA

On Aug 10, 12:41*pm, john89 wrote:

I got a question regarding the so-called "elevation", i.e. the highest
point of a runway. I have been told that the elevation is usually at
the threshold, right before the touchdown zone, in order to ensure an
easier take-off.

This information is available to pilots and updated periodically in
the Airport/Facilities Directory and the US Terminal Procedures, etc.

The A/FD defines it's "elevation" figure as "the highest point of an
airport's usable runways measured in feet from mean sea level." In
addition, the A/FD lists runway slope when it is .3 or greater for
airports that have instrument approaches and elaborates based on other
runway criteria ( or than 8000', etc)

For IFR purposes, the A/FD and approach plates include a Touchdown
Zone Elevation (TDZE) for specific runways.

Pilots, particular under IFR, are expected to be familiar with runways
of intended use and, if required, alternate airports. We're strongly
encouraged to study other airports along the route in case we need to
divert. Cheers!

-Chris
CFI, KTTD