Sloping runway
Joined: Sep 2002
Posts: 2,188
Likes: 6
From: La Belle Province
Because the ground slopes!
Runway location is a compromise between geographic location (towns, transport links), suitable ground for construction (i.e. not a swamp, preferably!), relatively level ground (level being ideal) and alignment with prevailing winds.
Since it's unlikely all of these can be met perfectly, some compromise must be accepted.
It is not practical to level the ground in most cases. A 10,000ft runway, 150ft wide and with a 2% slope (typical maximum catered for in perf manuals) would require some 4,500,000 cubic metres of infill simply to bring it level, resulting in a 200ft cliff at the end of the runway. To achieve a safe gradient around this runway-embankment would double or triple the amount of earth to be moved.
Runway location is a compromise between geographic location (towns, transport links), suitable ground for construction (i.e. not a swamp, preferably!), relatively level ground (level being ideal) and alignment with prevailing winds.
Since it's unlikely all of these can be met perfectly, some compromise must be accepted.
It is not practical to level the ground in most cases. A 10,000ft runway, 150ft wide and with a 2% slope (typical maximum catered for in perf manuals) would require some 4,500,000 cubic metres of infill simply to bring it level, resulting in a 200ft cliff at the end of the runway. To achieve a safe gradient around this runway-embankment would double or triple the amount of earth to be moved.
Joined: Sep 2002
Posts: 2,188
Likes: 6
From: La Belle Province
10,000ft long : 3048m
2% slope : 200ft drop : 60.96m
150ft wide : 45.72m
volume of triangular wedge under runway = length*'drop'*1/2 * width
I used 3000m * 60m * 50m * 0.5 to give 4.5million
If you use the 'exact' numbers its more like 4.2million
There's also a small inaccuracy in that the 10,000ft is along the runway surface, not horizontal, but that is only another 1 or 2 % error.
edit: I believe you must have used a 2 degree slope, which is equivalent to a 3.5% slope and would, indded, result in approx 7.3million cubic metres of infill
2% slope : 200ft drop : 60.96m
150ft wide : 45.72m
volume of triangular wedge under runway = length*'drop'*1/2 * width
I used 3000m * 60m * 50m * 0.5 to give 4.5million
If you use the 'exact' numbers its more like 4.2million
There's also a small inaccuracy in that the 10,000ft is along the runway surface, not horizontal, but that is only another 1 or 2 % error.
edit: I believe you must have used a 2 degree slope, which is equivalent to a 3.5% slope and would, indded, result in approx 7.3million cubic metres of infill
Last edited by Mad (Flt) Scientist; 12th November 2003 at 01:47.
Joined: Jun 2001
Posts: 274
Likes: 4
From: Outer Space
If memory serves, Bristol Lulsgate has quite a spectacular slope on one end of the runway. My colleague reminded me that if you stood at one end of the airfield, a westerly departing aircraft would dissapear down the slope halfway down and reappear in the climb at the other end.
Joined: Oct 2003
Posts: 71
Likes: 0
From: On your right..
When I went on first flying lesson i found out that Southend Airports runway EGMC (06/24) has what looks like a crater in the middle of it. Luckily we got using a 1/4 of the runway but still it must be funny in a large airplane when your taking off and your going up and down an hill!
Thanks Dave 14
Thanks Dave 14
Joined: Aug 2003
Posts: 26
Likes: 0
From: Australia
Sloping Runways
If you really want to see an prime example of a sloping runway, try looking at either WAU or BULOLO - i forget which one but the slope is from memory about 17 degrees. The old DC 3s used to land up slope and turn left onto a level hardstand at the end of the up slope - full throttle required otherwise they would roll back down the strip.
Take off no problem - point the nose down hill and away you go except for a few pine trees at the end of the strip.
I used to have some photos but have lost them in many moves.
vitamin B
Take off no problem - point the nose down hill and away you go except for a few pine trees at the end of the strip.
I used to have some photos but have lost them in many moves.
vitamin B
PPRuNeaholic
Joined: Jun 2000
Posts: 3,255
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From: Cairns FNQ
Bulolo is a level 2-way strip vitamin B, so Wau is the one you're thinking about. It has a published gradient of 8% and is a pretty constant slope, unlike many others in PNG. Of course, the reason why there's so many sloping runways in this country is that there is nowhere else to build them in a country that is basically all up and down.
Joined: Nov 2003
Posts: 128
Likes: 0
From: cheshire
24L at MAN is far from flat it has a concaved runway and quit a steep one at that (in runway tearm's that is) .... its quit an experianc watching a A330 take off from 24L watching it from behind like i did early this year ... what a site could se the top of the A330 as it got near V1 
