Question: Elevation --- RWY

[john89]

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

[Mike Ash]

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

[quietguy]

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.

[D Ramapriya]

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

[Ron Reagun]

"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

[bod43]

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-hnRfO8&feature=related

Here is the biggest visitor I can find.
De Havilland Canada DHC-7-102 Dash 7
http://www.airliners.net/photo/Tyrolean-Airways/De-Havilland-Canada/0466502/&sid=19c553be7546cb7b91bd7361540d25e9

Rumours of a Citation.

[A Guy Called Tyketto]

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Hash: SHA1

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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[john89]

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

[jan olieslagers[_2_]]

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

[C Gattman[_3_]]

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

[a[_3_]]

On Aug 11, 3:49*pm, C Gattman > wrote:
> 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

I must qualify for 'least sensitive' pilot here. I've made a number of
landings with Wx close to minimums, nasty weather, cross winds, night
time, and all that stuff. When I look up at minimums and see VASI and
runway locater lights and all that good stuff, I'm real happy to go
down the last couple of hundred feet, flare, and become earthbound
again. From the moment I go visual I really don't care what the actual
altitude of the runway I'm approaching is, I can see it, and know what
I have to do to fly the miss if needed. Does it really matter if it's
at 469 feet, or 500, at that point to those of us messing around in
SELs like Mooneys? What am I missing here? Even if a CAT 3 landing
(not in MY airplane!) the radar altimeter controls yoke back pressure
at flare, doesn't it? It's looking at actual wheels to ground
distances, not some indirect measure like "corrected altimeter
subtract field elevation equals air between wheels and ground.

The other minor blimp in all of this is I set the kollsman window,
then verify the altitude indication is within specification of
published altitude. The difference in altitude between the reference
datum and my static tube could be pretty significant -- something I
had not thought about before. 20 feet eats up a lot of a 50 foot error
budget.

[Mike Ash]

In article >,
john89 > wrote:

> 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.

If the high point is in the middle, it's probably because that's what
the terrain looked like before the runway was built. Ground never comes
perfectly level, and it's often not worth the expense of fixing it to be
absolutely level just because you happen to be building a runway.

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

[Peter Dohm]

"jan olieslagers" > wrote in message
...
> 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

If the winds are calm (<4 Kts, IIRC) and there is no traffic, you could get
a similar response here in the US; although, other factors are trivial, some
airports do have a preferred take off direction for noise abatement. I
suppose that the approved "phraseology" would be different, but the sense of
it should still work.

Peter

[Peter Dohm]

"a" > wrote in message
...
>On Aug 11, 3:49 pm, C Gattman > wrote:
>> 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
>
> I must qualify for 'least sensitive' pilot here. I've made a number of
> landings with Wx close to minimums, nasty weather, cross winds, night
> time, and all that stuff. When I look up at minimums and see VASI and
> runway locater lights and all that good stuff, I'm real happy to go
> down the last couple of hundred feet, flare, and become earthbound
> again. From the moment I go visual I really don't care what the actual
> altitude of the runway I'm approaching is, I can see it, and know what
> I have to do to fly the miss if needed. Does it really matter if it's
> at 469 feet, or 500, at that point to those of us messing around in
> SELs like Mooneys? What am I missing here?
>
Funny you should ask... :-)

Speaking as a former avionics technician and also student pilot, who also
rode "shotgun" on a few single pilot IFR flights back in the day, you are
exactly correct. It just happens that, in addition to the dedicated
"simmers" who stop by from time to time, this forum also serves as a source
of information for a lot of beginning students--and also for future pilots
and other interested citizens who have never been inside the airport fence.
Therefore, they are not necessary aware of which portions of the information
which is required to be surveyed, and entered into databases and onto
charts, arereally trivial in normal operations.


>
> Even if a CAT 3 landing
> (not in MY airplane!) the radar altimeter controls yoke back pressure
> at flare, doesn't it? It's looking at actual wheels to ground
> distances, not some indirect measure like "corrected altimeter
> subtract field elevation equals air between wheels and ground.
>
I have no personal experience with Cat 3, so I can not address the
interconnection between the radio altimeter and the autopilot; but...

Back in the day, I was a "fill in" for the regular radio altimeter
technician--so here foes: The radio altimeter, which provides the
information regarding the flare in precision approaches, measures the
distance between the ground and the radio altimeter antenna--corrected for
the height of the antenna above the ground in the typical landing attitude.
On large transport category aircraft, that is typically several feet lower
than the antenna position when the aircraft is at rest. So, in practice,
you are exactly right about the reading of the radio altimeter in the
process of landing with the expected attitude and flap deployment.

BTW, on very large aircraft such as the Boeing 747, where the pilots eye
level at the time of touchdown is too high to give a reliable height
indication relative to the runway, it is common to also use the radio
altimeter as an information source in initiating the flare.

Peter
>
> The other minor blimp in all of this is I set the kollsman window,
> then verify the altitude indication is within specification of
> published altitude. The difference in altitude between the reference
> datum and my static tube could be pretty significant -- something I
> had not thought about before. 20 feet eats up a lot of a 50 foot error
> budget.

[[email protected][_2_]]

On Aug 11, 1:18*pm, john89 > wrote:

> Apparently there are just now "absolute" true rules such as:
>
> Airplanes always land in the same direction as they took off.

Not so (although the norm in most cases, especially when wind is a
factor). I fly towplanes and gliders on weekends, and on days when
the wind is light, it's common to takeoff in one direction and land in
the opposite direction, as this saves taxy time and makes for a more
efficient (and actually safer, believe it or not, as it avoids power
vs glider conflicts on final) operation. Granted, this is on a huge
grass airstrip, so there is no head-on conflict - but I've even seen
cases of simultaneous takeoffs and landings in opposite directions,
with the planes/gliders passing on the ground in the middle of their
respective takeoff and landing rolls.

Definitely requires a good lookout!

Kirk
66

[Jon Woellhaf]

> wrote

> ... I've even seen
cases of simultaneous takeoffs and landings in opposite directions,
with the planes/gliders passing on the ground in the middle of their
respective takeoff and landing rolls.

Yikes!

[[email protected][_2_]]

On Aug 14, 3:35*pm, "Jon Woellhaf" > wrote:
> > wrote
>
> > ... I've even seen
>
> cases of simultaneous takeoffs and landings in opposite directions,
> with the planes/gliders passing on the ground in the middle of their
> respective takeoff and landing rolls.
>
> Yikes!

Yikes for sure. That happened at the old Issaquah, WA gliderfield -
there were two commercial glider operations there, one at each end of
a nice grass strip, and each disliked the other. So when the winds
were light - you had to be heads up, to say the least! Plus there was
a jump school, so occasionnally you had to add a student under a chute
to the mix, and worst of all was the ultralight driver who would
wander around the pattern ...

Sigh, that was a fun place - always a crowd of onlookers ( I wonder
why!!). Shopping center now, of course.

Kirk
66

[Mike Ash]

In article
>,
" > wrote:

> On Aug 14, 3:35*pm, "Jon Woellhaf" > wrote:
> > > wrote
> >
> > > ... I've even seen
> >
> > cases of simultaneous takeoffs and landings in opposite directions,
> > with the planes/gliders passing on the ground in the middle of their
> > respective takeoff and landing rolls.
> >
> > Yikes!
>
> Yikes for sure. That happened at the old Issaquah, WA gliderfield -
> there were two commercial glider operations there, one at each end of
> a nice grass strip, and each disliked the other. So when the winds
> were light - you had to be heads up, to say the least! Plus there was
> a jump school, so occasionnally you had to add a student under a chute
> to the mix, and worst of all was the ultralight driver who would
> wander around the pattern ...
>
> Sigh, that was a fun place - always a crowd of onlookers ( I wonder
> why!!). Shopping center now, of course.

Funny. At my club, if we have a glider hooked up and ready to take off
on the pavement, and another glider on final for the parallel grass, we
will usually hold the takeoff until the landing glider is down and
stopped just to make sure everybody has the maximum number of options in
case Bad Stuff ensues.

The past is a different country, for sure.

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

[jan olieslagers[_2_]]

> On Aug 11, 1:18 pm, john89 > wrote:
>
>> Apparently there are just now "absolute" true rules such as:
>>
>> Airplanes always land in the same direction as they took off.

As I said before: it all depends on where you are. Take a look at
Gap-Tallard LFNA on a sunny day and you will see glider tugs AND
paradrop planes like Twin Otters taking off one way and landing in the
other - for efficiency indeed. Quite funny to take off from the 21 and
hear a Pilatur Porter announce finals for the 03! I suppose one gets
used to it.
KA

[RST Engineering - JIm]

KGOO (formerly O17, Grass Valley CA) has a 3% slope to the runway. The
firebombers (air tankers Grumman S2Ts) always take off downhill and land
uphill. Night operations for everybody are notamed the same because of the
trees at the east end of the runway.

Jim




On Aug 11, 1:18 pm, john89 > wrote:

> Apparently there are just now "absolute" true rules such as:
>
> Airplanes always land in the same direction as they took off.

[a[_3_]]

On Aug 15, 11:18*am, "RST Engineering - JIm" >
wrote:
> KGOO (formerly O17, Grass Valley CA) has a 3% slope to the runway. *The
> firebombers (air tankers Grumman S2Ts) always take off downhill and land
> uphill. *Night operations for everybody are notamed the same because of the
> trees at the east end of the runway.
>
> Jim
>
> On Aug 11, 1:18 pm, john89 > wrote:
>
>
>
> > Apparently there are just now "absolute" true rules such as:
>
> > Airplanes always land in the same direction as they took off.- Hide quoted text -
>
> - Show quoted text -

Jim, a 3% slope would mean 3 feet of altitiude change per 100 feet of
runway. On a 4000 fooot runway that means 120 feet. My question is,
if the tiedowns are near the low end, when the altimeter is set to
local pressure, if the altimeter is calibrated and the field elevation
is taken as the highest point on the runway, there would be a 120 foot
'error'. For a pilot starting an IFR flight who didn't know better,
that's outside the 75 foot error allowed. Are there special
procedures published for that airport or others like it?

SInce the takeoffs there are downhill, the altimeter would read
within tolerance if checked during run-up at the take off end (if one
knew of the problem) but I am wondering about the more general case.

[RST Engineering - JIm]

My error. We did a massive cut and paste job on the runway about 15 years
ago and took an average 3% slope down to 2.1%

But that's not the point. THe point is that both ends of the runway are
surveyed and the elevation at that end marked for altimeter setting.

THe other point is that instrument approach charts list TDZE (touch down
zone elevation) for just this reason ... not many airports have EXACTLY the
same elevation at both ends, not even in Kansas, Toto.

Jim



"a" > wrote in message
...
On Aug 15, 11:18 am, "RST Engineering - JIm" >
wrote:
> KGOO (formerly O17, Grass Valley CA) has a 3% slope to the runway. The
> firebombers (air tankers Grumman S2Ts) always take off downhill and land
> uphill. Night operations for everybody are notamed the same because of the
> trees at the east end of the runway.
text -
>
> - Show quoted text -

Jim, a 3% slope would mean 3 feet of altitiude change per 100 feet of
runway. On a 4000 fooot runway that means 120 feet. My question is,
if the tiedowns are near the low end, when the altimeter is set to
local pressure, if the altimeter is calibrated and the field elevation
is taken as the highest point on the runway, there would be a 120 foot
'error'. For a pilot starting an IFR flight who didn't know better,
that's outside the 75 foot error allowed. Are there special
procedures published for that airport or others like it?

SInce the takeoffs there are downhill, the altimeter would read
within tolerance if checked during run-up at the take off end (if one
knew of the problem) but I am wondering about the more general case.