Displaced Thresholds.
Join Date: Jul 2001
Location: Hong Kong
Posts: 287
Likes: 0
Received 0 Likes
on
0 Posts
The Australian AIP has the following note associated with the diagram showing the undershoot area with a permanent displaced threshold:
"This section of runway available for all operations except landing in the direction indicated".
http://www.airservicesaustralia.com/...ad/ad11120.pdf Go to Figure 5.
"This section of runway available for all operations except landing in the direction indicated".
http://www.airservicesaustralia.com/...ad/ad11120.pdf Go to Figure 5.
Thread Starter
Join Date: Aug 2002
Location: Caribbean
Posts: 17
Likes: 0
Received 0 Likes
on
0 Posts
Thanks ex-driver,
I wish however that they would be a little more explicit with the law. That looks like it is to be interpreted as being illegal to land before, but then they have the approach obstacled clearance slope end 60m before the displacement.
From a common sense point of view, I still can't understand why it would be illegal. You've cleared the obstacle, and the pavement is solid, at that point, what exactly is unsafe?
Thanks for the link. I guess that appears to be one for illegal.
Score now 1-1.
I wish however that they would be a little more explicit with the law. That looks like it is to be interpreted as being illegal to land before, but then they have the approach obstacled clearance slope end 60m before the displacement.
From a common sense point of view, I still can't understand why it would be illegal. You've cleared the obstacle, and the pavement is solid, at that point, what exactly is unsafe?
Thanks for the link. I guess that appears to be one for illegal.
Score now 1-1.
Join Date: Jul 2001
Location: Hong Kong
Posts: 287
Likes: 0
Received 0 Likes
on
0 Posts
My question is "why"? What factors are coming in to play to require that extra runway before the displaced threshold?"
Airmanship (and the law) require that you know the landing distance required vs the landing distance actually available, before committing your tyres to the tarmac.
Landing distance available means the length of runway declared to be available and suitable for the ground run of an aeroplane landing.
For most operations, the Landing Distance Required calculated is factored to give "fat" to the demonstrated distances. This "fat" should be used to give a bit of breathing space during the landing roll, not an attempt to put the wheels just past the weeds.
For info, here are the factors for various aircraft weights here in Aussie (should be ICAO.....!)
...an aircraft must not land unless the landing distance available is equal to or greater than the distance required to bring the aeroplane to a complete stop,..., following an approach to land at a speed not less than 1.3 Vs maintained to within 50 ft of the landing surface. This distance is to be measured from the point where the aeroplane first reaches a height of 50 feet above the landing surface and must be multiplied by the following factors:
RPT SINGLE ENGINE AEROPLANES, CHARTER OPS, AERIAL WORK, & PRIVATE OPS
(a) 1.15 for aeroplanes with MTOW of 2000kg or less;
(b) 1.43 for aeroplanes with MTOW of 4500kg or greater;
(c) for aeroplanes with MTOW between 2000kg and 4500kg, a factor derived by linear interpolation between 1.15 and 1.43 according to the MTOW.
RPT MULTI-ENGINE NOT ABOVE 5700KG
(a) 1.15 for MTOW equal to or less than 2000kg
(b) 1.318 for MTOW equal to 3500kg
(c) for aeroplanes with MTOW greater than 2000kg but less than 3500kg, a factor derived by linear interpolation betwenn 1.15 and 1.318
(d)1.43 for MTOW exceeding 3500kg but not exceeding 5700kg
AEROPLANES ABOVE 5700KG - ALL OPERATIONS (Turbine and Piston)
for jet-engined aeroplanes
(a) 1.67 for RPT when landing on a dry runway, or charter on a wet or dry runway
(b) 1.92 for RPT landing on a wet runway (or the distance given in a wet runway landing chart
For propeller driven aeroplanes landing at a destination aerodrome
(a) 1.43 for a dry runway
(b) 1.67 for a wet runway
Airmanship (and the law) require that you know the landing distance required vs the landing distance actually available, before committing your tyres to the tarmac.
Landing distance available means the length of runway declared to be available and suitable for the ground run of an aeroplane landing.
For most operations, the Landing Distance Required calculated is factored to give "fat" to the demonstrated distances. This "fat" should be used to give a bit of breathing space during the landing roll, not an attempt to put the wheels just past the weeds.
For info, here are the factors for various aircraft weights here in Aussie (should be ICAO.....!)
...an aircraft must not land unless the landing distance available is equal to or greater than the distance required to bring the aeroplane to a complete stop,..., following an approach to land at a speed not less than 1.3 Vs maintained to within 50 ft of the landing surface. This distance is to be measured from the point where the aeroplane first reaches a height of 50 feet above the landing surface and must be multiplied by the following factors:
RPT SINGLE ENGINE AEROPLANES, CHARTER OPS, AERIAL WORK, & PRIVATE OPS
(a) 1.15 for aeroplanes with MTOW of 2000kg or less;
(b) 1.43 for aeroplanes with MTOW of 4500kg or greater;
(c) for aeroplanes with MTOW between 2000kg and 4500kg, a factor derived by linear interpolation between 1.15 and 1.43 according to the MTOW.
RPT MULTI-ENGINE NOT ABOVE 5700KG
(a) 1.15 for MTOW equal to or less than 2000kg
(b) 1.318 for MTOW equal to 3500kg
(c) for aeroplanes with MTOW greater than 2000kg but less than 3500kg, a factor derived by linear interpolation betwenn 1.15 and 1.318
(d)1.43 for MTOW exceeding 3500kg but not exceeding 5700kg
AEROPLANES ABOVE 5700KG - ALL OPERATIONS (Turbine and Piston)
for jet-engined aeroplanes
(a) 1.67 for RPT when landing on a dry runway, or charter on a wet or dry runway
(b) 1.92 for RPT landing on a wet runway (or the distance given in a wet runway landing chart
For propeller driven aeroplanes landing at a destination aerodrome
(a) 1.43 for a dry runway
(b) 1.67 for a wet runway
Last edited by Ex Douglas Driver; 25th Jul 2005 at 10:33.
Guest
Posts: n/a
Regarding ' things going on, on the displaced portion that the pilot doesn't know about '... This would have to be covered in a notam. Any change to a runway, whether temporary displacement or otherwise, must be issued in a notam.
Also, if the area is unfit for surface movement of a/c it must be marked with X's or chevrons leading to the displaced threshold (not arrows).
Also, if the area is unfit for surface movement of a/c it must be marked with X's or chevrons leading to the displaced threshold (not arrows).
The markings are, I think, a different issue.
Obviously you have a problem with your local authority that, on the information you have given, seems to want to make an example of your friend. I'm wary of quoting law - as you have asked for - because only a lawyer familiar with your legislation can advise you on this but your link to the Canadian AIP may not be quite the same as law. In the UK there is law (called the Air Navigation Order - ANO) that covers how aircraft are operated and other aviation things. The AIP is an information document that has no status as law. But the ANO says you mustn't endanger anyone with your aircraft and if you ignore something in the AIP you may be accused of endangering someone, maybe because you didn't follow normal aviation procedures or advice in the AIP.
Join Date: Jan 2005
Location: ISTANBUL
Posts: 81
Likes: 0
Received 0 Likes
on
0 Posts
ac500u,
The ICAO documents are not like Canadian AIP. I checked once more.
Just a copy paste for you from Annex 14 Aerodromes
10.2 Displaced threshold
10.2.1 If an object extends above the approach surface
and the object cannot be removed, consideration should be
given to displacing the threshold permanently.
10.2.2 To meet the obstacle limitation objectives of
Chapter 4, the threshold should ideally be displaced down the
runway for the distance necessary to provide that the approach
surface is cleared of obstacles.
10.2.3 However, displacement of the threshold from the
runway extremity will inevitably cause reduction of the
landing distance available, and this may be of greater operational
significance than penetration of the approach surface
by marked and lighted obstacles. A decision to displace the
threshold, and the extent of such displacement, should
therefore have regard to an optimum balance between the
considerations of clear approach surfaces and adequate landing
distance. In deciding this question, account will need to be
taken of the types of aeroplanes which the runway is intended
to serve, the limiting visibility and cloud base conditions under
which the runway will be used, the position of the obstacles in
relation to the threshold and extended centre line and, in the
case of a precision approach runway, the significance of the
obstacles to the determination of the obstacle clearance limit.
10.2.4 Notwithstanding the consideration of landing
distance available, the selected position for the threshold
should not be such that the obstacle-free surface to the threshold
is steeper than 3.3 per cent where the code number is 4 or
steeper than 5 per cent where the code number is 3.
10.2.5 In the event of a threshold being located according
to the criteria for obstacle-free surfaces in the preceding paragraph,
the obstacle marking requirements of Chapter 6 should continue to be met in relation to the displaced threshold.
But may be this might be of help for you (also from An14) :
3.1.5 Recommendation.- When it is necessary to
displace a threshold, either permanently or temporarily, from
its normal location, account should be taken of the various
factors which may have a bearing on the location of the
threshold. Where this displacement is due to an unserviceable
runway condition, a cleared and graded area of at least 60 m
in length should be available between the unserviceable area
and the displaced threshold. Additional distance should also
be provided to meet the requirements of the runway end safety
area as appropriate.
Best Regards,
Guclu
The ICAO documents are not like Canadian AIP. I checked once more.
Just a copy paste for you from Annex 14 Aerodromes
10.2 Displaced threshold
10.2.1 If an object extends above the approach surface
and the object cannot be removed, consideration should be
given to displacing the threshold permanently.
10.2.2 To meet the obstacle limitation objectives of
Chapter 4, the threshold should ideally be displaced down the
runway for the distance necessary to provide that the approach
surface is cleared of obstacles.
10.2.3 However, displacement of the threshold from the
runway extremity will inevitably cause reduction of the
landing distance available, and this may be of greater operational
significance than penetration of the approach surface
by marked and lighted obstacles. A decision to displace the
threshold, and the extent of such displacement, should
therefore have regard to an optimum balance between the
considerations of clear approach surfaces and adequate landing
distance. In deciding this question, account will need to be
taken of the types of aeroplanes which the runway is intended
to serve, the limiting visibility and cloud base conditions under
which the runway will be used, the position of the obstacles in
relation to the threshold and extended centre line and, in the
case of a precision approach runway, the significance of the
obstacles to the determination of the obstacle clearance limit.
10.2.4 Notwithstanding the consideration of landing
distance available, the selected position for the threshold
should not be such that the obstacle-free surface to the threshold
is steeper than 3.3 per cent where the code number is 4 or
steeper than 5 per cent where the code number is 3.
10.2.5 In the event of a threshold being located according
to the criteria for obstacle-free surfaces in the preceding paragraph,
the obstacle marking requirements of Chapter 6 should continue to be met in relation to the displaced threshold.
But may be this might be of help for you (also from An14) :
3.1.5 Recommendation.- When it is necessary to
displace a threshold, either permanently or temporarily, from
its normal location, account should be taken of the various
factors which may have a bearing on the location of the
threshold. Where this displacement is due to an unserviceable
runway condition, a cleared and graded area of at least 60 m
in length should be available between the unserviceable area
and the displaced threshold. Additional distance should also
be provided to meet the requirements of the runway end safety
area as appropriate.
Best Regards,
Guclu
Thread Starter
Join Date: Aug 2002
Location: Caribbean
Posts: 17
Likes: 0
Received 0 Likes
on
0 Posts
Thanks for everyone's replies.
Responses in Order....
Ex-DC-Driver - Regarding why. Simple put, because it is safer. Some aircraft which were built in the 50's, had numbers that were very optimistic. It was very popular in that era to juice the numbers to sell aircraft. The Ac500 is a fine example. I can't remember the exact numbers but it says you can land at gross, in something like 1100ft. It also suggests that you approach at around 65 kts. Both of these are near impossible. At gross and 65kts, the aircraft is in a full stall, not just horn, full wing drop chaos. Maybe if you hit the runway at 65 you could stop in 1100, but you might not be able to use the aircraft again. But, according to the numbers, and the 'buffer' it is perfectly legal. But, I assure you those numbers are truely outrageous. The t/o numbers are even worse. Something like 1400 at gross. Absolutely absurd. Anyone who's flown one can verify. So, in my mind, not why, but WHY NOT. The obstacle is cleared, the runway is solid, and the is 50 feet of water 4ft of the end of the runway. Which do you really think is safer?
Spitoon - Regarding changes to the displaced portion. As you described yourself, this portion is clearly allowed to be used for backtrack, takeoff, and landing roll from other direction, it's just landing that's in question. If someone was digging a hole ON ANY PART OF THE MANUEVERING AREA, there would have to be a notam, and resultant markings. It is still part of the manuevering area, irregardless of it's availability for landing.
Still very interested in any quotes from law, or even guidance books such as AIP's. I've read the ICAO standards several times, but it doesn't clearly stipulate yes or no.
Thanks again for everyone's input.
Responses in Order....
Ex-DC-Driver - Regarding why. Simple put, because it is safer. Some aircraft which were built in the 50's, had numbers that were very optimistic. It was very popular in that era to juice the numbers to sell aircraft. The Ac500 is a fine example. I can't remember the exact numbers but it says you can land at gross, in something like 1100ft. It also suggests that you approach at around 65 kts. Both of these are near impossible. At gross and 65kts, the aircraft is in a full stall, not just horn, full wing drop chaos. Maybe if you hit the runway at 65 you could stop in 1100, but you might not be able to use the aircraft again. But, according to the numbers, and the 'buffer' it is perfectly legal. But, I assure you those numbers are truely outrageous. The t/o numbers are even worse. Something like 1400 at gross. Absolutely absurd. Anyone who's flown one can verify. So, in my mind, not why, but WHY NOT. The obstacle is cleared, the runway is solid, and the is 50 feet of water 4ft of the end of the runway. Which do you really think is safer?
Spitoon - Regarding changes to the displaced portion. As you described yourself, this portion is clearly allowed to be used for backtrack, takeoff, and landing roll from other direction, it's just landing that's in question. If someone was digging a hole ON ANY PART OF THE MANUEVERING AREA, there would have to be a notam, and resultant markings. It is still part of the manuevering area, irregardless of it's availability for landing.
Still very interested in any quotes from law, or even guidance books such as AIP's. I've read the ICAO standards several times, but it doesn't clearly stipulate yes or no.
Thanks again for everyone's input.
Join Date: Jan 2000
Location: Currently, East, Middle of
Posts: 55
Likes: 0
Received 0 Likes
on
0 Posts
Any legal document - here's a couple
You asked for "any" legal reference. Here's one, albeit local in nature but very plain.
http://www.dot.wisconsin.gov/travel/...-standards.doc
scroll down, item 9
The quote:
A displaced threshold is a runway threshold located at a point other than the physical end of the runway. The portion of the runway so displaced may be used for takeoff but not for landing. Landing aircraft may use the displaced area on the opposite end for roll out
And onther....
From the FAA, Central Region - Airports Division, AIP Guide Index, Runway Commissioning, Data elements:
The link:
http://www.faa.gov/arp/ace/aip/aip-1121.cfm
Scroll down to item 51.
The quote:
The portion of pavement behind a displaced threshold may be available for takeoffs either
direction and landings from the opposite direction. This length is included in the total length of the
runway.
http://www.dot.wisconsin.gov/travel/...-standards.doc
scroll down, item 9
The quote:
A displaced threshold is a runway threshold located at a point other than the physical end of the runway. The portion of the runway so displaced may be used for takeoff but not for landing. Landing aircraft may use the displaced area on the opposite end for roll out
And onther....
From the FAA, Central Region - Airports Division, AIP Guide Index, Runway Commissioning, Data elements:
The link:
http://www.faa.gov/arp/ace/aip/aip-1121.cfm
Scroll down to item 51.
The quote:
The portion of pavement behind a displaced threshold may be available for takeoffs either
direction and landings from the opposite direction. This length is included in the total length of the
runway.
Last edited by LanFranc; 25th Jul 2005 at 22:37.
PPRuNeaholic
Join Date: Jun 2000
Location: Cairns FNQ
Posts: 3,255
Likes: 0
Received 0 Likes
on
0 Posts
It might be a good idea to remember that, when quoting anything from an ICAO Annex, it is not law. Contracting States make it into law through their own legal processes and should notify any differences in their AIP. This might be a good place to start your research ac500u.
If there's no reference to "displaced thresholds" you might be able to infer that the national aviation laws in the particular country fully reflect the Annex 14 specifications. If so, you probably need to see what clarifying information is provided in the AIP. After checking all of that, you'll probably need to consult a lawyer who is conversant with the laws of that country.
If there's no reference to "displaced thresholds" you might be able to infer that the national aviation laws in the particular country fully reflect the Annex 14 specifications. If so, you probably need to see what clarifying information is provided in the AIP. After checking all of that, you'll probably need to consult a lawyer who is conversant with the laws of that country.
ac500u, you use the phrase "the runway is solid". But is it STRONG enough to take the forces of a landing aircraft? Runway extensions are often built to lower bearing standards because its cheaper! How are you supposed to know what the strength of this area is? Because you have always landed on it in the past? Don't think that would stand up in court.
Thread Starter
Join Date: Aug 2002
Location: Caribbean
Posts: 17
Likes: 0
Received 0 Likes
on
0 Posts
The runway is consistent from end to end. The only put the displaced threshold markings in a few years ago.
Also, if a portion of the runway in too weak to support landing light aircraft, it would most likely be too soft to support taxiing, or stationary aircraft as well, due to prolonged times in one position.
I've never heard of pavement that can support light aircraft taxiing, but not landing. I don't mean it doesn't exist, I've just never heard of it, have you? You have any examples?
Oh, and finding a lawyer who\'s conversant with the local regulations is like finding a local rocket scientist.
Also, if a portion of the runway in too weak to support landing light aircraft, it would most likely be too soft to support taxiing, or stationary aircraft as well, due to prolonged times in one position.
I've never heard of pavement that can support light aircraft taxiing, but not landing. I don't mean it doesn't exist, I've just never heard of it, have you? You have any examples?
Oh, and finding a lawyer who\'s conversant with the local regulations is like finding a local rocket scientist.
Prof. Airport Engineer
Join Date: Oct 2000
Location: Australia (mostly)
Posts: 726
Likes: 0
Received 0 Likes
on
0 Posts
ac500u,
I've stuck a few displaced thresholds in during my time. Before I come out with my version of the warnings that j-t and mutt were making, let me mention the ICAO section that goes to the heart of the aircraft operation and is relevant to your request: Annex 6 — Operation of Aircraft Part 1 (8th edition):
There is nothing else in Annex 6 that makes landing short illegal or legal. There are also examples in the Attachments of that Annex on how the aircraft manufacturers calculate landing distance, but while informative to read, they don’t dictate how the pilot must land the aircraft. They are presumably for standardisation and the avoidance of over-optimistic performance numbers such as you mentioned earlier.
OzExpat put a nice argument in his post above, which suggests your lawyers can take forward this short, but powerful section 5.2.11 to build the case that the flight was legal because you landed safely etc etc. The pavement strength issue is a rarity and not normally expected to crop up in displaced thresholds (but I'm not ruling it out). If the local groundstaff can drive their truck up the runway or drive the firetender up it, then it will support a light aircraft.
Now back to the warnings. I find the calculation of displaced thresholds are not easy and are somewhat counter-intuitive. We always have 3 or 4 people do the calculations, and after going around a bit, they hopefully come up with the right answer. That takes a few days to work out, and I wonder how your friend can do it so quickly while landing the aircraft. I'm sure he is aware of the obvious traps, such as:
I've stuck a few displaced thresholds in during my time. Before I come out with my version of the warnings that j-t and mutt were making, let me mention the ICAO section that goes to the heart of the aircraft operation and is relevant to your request: Annex 6 — Operation of Aircraft Part 1 (8th edition):
5.2.11 Landing. The aeroplane shall, at the aerodrome of intended landing and at any alternate aerodrome, after clearing all obstacles in the approach path by a safe margin, be able to land, with assurance that it can come to a stop or, for a seaplane, to a satisfactorily low speed, within the landing distance available. Allowance shall be made for expected variations in the approach and landing techniques, if such allowance has not been made in the scheduling of performance data.
OzExpat put a nice argument in his post above, which suggests your lawyers can take forward this short, but powerful section 5.2.11 to build the case that the flight was legal because you landed safely etc etc. The pavement strength issue is a rarity and not normally expected to crop up in displaced thresholds (but I'm not ruling it out). If the local groundstaff can drive their truck up the runway or drive the firetender up it, then it will support a light aircraft.
Now back to the warnings. I find the calculation of displaced thresholds are not easy and are somewhat counter-intuitive. We always have 3 or 4 people do the calculations, and after going around a bit, they hopefully come up with the right answer. That takes a few days to work out, and I wonder how your friend can do it so quickly while landing the aircraft. I'm sure he is aware of the obvious traps, such as:
Thread Starter
Join Date: Aug 2002
Location: Caribbean
Posts: 17
Likes: 0
Received 0 Likes
on
0 Posts
Over Run,
Thanks for the informative post. Nice name by the way... somewhat appropriate for this topic.
When it comes down to safety, (and longevity) like you had mentioned, that obviously has to be taken on a case by case basis.
I would never suggest landing prior to a displaced threshold on any airport that someone wasn't extremely familiar with.
The sea level VFR only airport in question has been around for about 12 years. They decided to paint a displaced threshold on it about 6 years ago. The pilot in question has landed at this airport virtually every working day for the last 4 years. Probably more than 1000 times. The obstacle on the approach cannot be mistaken, it is a large hill approximately 2 miles on final roughly 500 ft tall. It is possible to approach over the hill, but the gradient is quite extreme. It is very easy, and common practice to turn base/final inside of the 2 miles, and thus entirely avoid the hill, the very obstacle displacing the threshold.
In this particular case, safety and longevity require landing before the displaced threshold. History at this airfield has shown that several aircraft have overrun the runway, after touching down post threshold, but none have ever over run after settling prior to.
The numbers allow several different types to land there, commonly BN2's, AC500's, DHC6's, C402(stolkit) etc. Some have gotten authority to land 208's and 228's but the numbers do not allow such.
In summary, I think in this specific case, and several others, the opposite of the theory could be valid. That is, you could get away with landing after the threshold once, but it would be safer to land before it, every time.
Thanks for the informative post. Nice name by the way... somewhat appropriate for this topic.
When it comes down to safety, (and longevity) like you had mentioned, that obviously has to be taken on a case by case basis.
I would never suggest landing prior to a displaced threshold on any airport that someone wasn't extremely familiar with.
The sea level VFR only airport in question has been around for about 12 years. They decided to paint a displaced threshold on it about 6 years ago. The pilot in question has landed at this airport virtually every working day for the last 4 years. Probably more than 1000 times. The obstacle on the approach cannot be mistaken, it is a large hill approximately 2 miles on final roughly 500 ft tall. It is possible to approach over the hill, but the gradient is quite extreme. It is very easy, and common practice to turn base/final inside of the 2 miles, and thus entirely avoid the hill, the very obstacle displacing the threshold.
In this particular case, safety and longevity require landing before the displaced threshold. History at this airfield has shown that several aircraft have overrun the runway, after touching down post threshold, but none have ever over run after settling prior to.
The numbers allow several different types to land there, commonly BN2's, AC500's, DHC6's, C402(stolkit) etc. Some have gotten authority to land 208's and 228's but the numbers do not allow such.
In summary, I think in this specific case, and several others, the opposite of the theory could be valid. That is, you could get away with landing after the threshold once, but it would be safer to land before it, every time.
Guest
Posts: n/a
ac500u, I am pleased that you have gained confidence from the posts in response to your question. You clearly believe that the information that I offered, to the effect that as the pilot of a landing aircraft you may not be aware or be made aware of some activity that is taking place in an area of the aerodrome that is not available for landing, is incorrect.
Having spent the best part of 30 years dealing with such matters, I can assure you that in certain circumstances this may well be the case. For the benefit of anyone else reading this I would suggest that touching down before a displaced landing threshold is highly inadvisable. To re-iterate my earlier comment "A displaced landing threshold is the start of the runway for a landing aircraft".
Having spent the best part of 30 years dealing with such matters, I can assure you that in certain circumstances this may well be the case. For the benefit of anyone else reading this I would suggest that touching down before a displaced landing threshold is highly inadvisable. To re-iterate my earlier comment "A displaced landing threshold is the start of the runway for a landing aircraft".
Thread Starter
Join Date: Aug 2002
Location: Caribbean
Posts: 17
Likes: 0
Received 0 Likes
on
0 Posts
Spitoon,
Would you agree that the 'unavailable portion' as you've described it, is part of the Manuevering Area? If it isn't, why not? If it is, why would this area not be held to he standards of the rest of the manuevering area, such as surface integrity, clearance to position, etc?
If you need clearance to taxi on the taxiway, why would you not need clearance to move through the displaced portion? If potholes on the apron are notamed, or marked, why would they not be on the pre threshold portion? If there were some obstacle on the displaced part, wouldn't they then have to re-displace the displaced threshold temporarily to avoid the obstacle?
The quote I\'m most familiar with regarding this (from local regulations) is as follows.
MATTERS OF OPERATIONAL SIGNIFICANCE AFFECTING AIRCRAFT PERFORMANCE
The condition of the movement area and the operational status of related facilities shall be monitored and reports on metters of operational significance of affecting aircraft performance given, particularly in respect of the following.
a) construction or maintenance work;
b) rough or broken surfaces on a runway, a taxiway or an apron;
c) snow, slush, or ice on a runway, a taxiway or an apron;
d) water on a runway, a taxiway or an apron;
e) snow banks or drifts adjacent to a runway, a taxiway or an apron
f) anti-icing or de-icing liquid chemicals on a runway, a taxiway or an apron;
g) other temporary hazards, including parked aircraft;
h) failure or irregular operation of part or all of the aerodrome visual aids; and
i) failure of the normal or secondary power supply.
Spitoon, what is it that you are speculating could be taking place on this displaced portion that the pilot wouldn\'t know about?
Would you agree that the 'unavailable portion' as you've described it, is part of the Manuevering Area? If it isn't, why not? If it is, why would this area not be held to he standards of the rest of the manuevering area, such as surface integrity, clearance to position, etc?
If you need clearance to taxi on the taxiway, why would you not need clearance to move through the displaced portion? If potholes on the apron are notamed, or marked, why would they not be on the pre threshold portion? If there were some obstacle on the displaced part, wouldn't they then have to re-displace the displaced threshold temporarily to avoid the obstacle?
The quote I\'m most familiar with regarding this (from local regulations) is as follows.
MATTERS OF OPERATIONAL SIGNIFICANCE AFFECTING AIRCRAFT PERFORMANCE
The condition of the movement area and the operational status of related facilities shall be monitored and reports on metters of operational significance of affecting aircraft performance given, particularly in respect of the following.
a) construction or maintenance work;
b) rough or broken surfaces on a runway, a taxiway or an apron;
c) snow, slush, or ice on a runway, a taxiway or an apron;
d) water on a runway, a taxiway or an apron;
e) snow banks or drifts adjacent to a runway, a taxiway or an apron
f) anti-icing or de-icing liquid chemicals on a runway, a taxiway or an apron;
g) other temporary hazards, including parked aircraft;
h) failure or irregular operation of part or all of the aerodrome visual aids; and
i) failure of the normal or secondary power supply.
Spitoon, what is it that you are speculating could be taking place on this displaced portion that the pilot wouldn\'t know about?
PPRuNeaholic
Join Date: Jun 2000
Location: Cairns FNQ
Posts: 3,255
Likes: 0
Received 0 Likes
on
0 Posts
Would you agree that the 'unavailable portion' as you've described it, is part of the Manuevering Area? If it isn't, why not? If it is, why would this area not be held to he standards of the rest of the manuevering area, such as surface integrity, clearance to position, etc?
I have seen nothing in Annex 14 that specifies what the strength of these areas should be. As a result, in my country of operations, the Stopway is only half the strength of the RWY and, if there's a RESA, it is compacted gravel and soil, grassed over. I don't want to get into RESA too much, despite the fact that the Annex 14 specification states that it is provided for aircraft undershooting on approach, or an over-run on take-off. Many of the poorer countries do not provide RESA and this is why I don't want to discuss it in any depth.
However, the stopway is simply there to allow an additional length for an aeroplane to stop in the event of a rejected take-off, without doing any damage to the aircraft. Therefore, it is not intended to suffer the impact load associated with a landing and, hence, doesn't have to be as strong as the RWY itself.
The reality is that any airport operator that wants to save some money will use a lesser strength in the Stopway.
Now, to make this relevant to the permanently displaced THR scenario, the airport operator is not required to maintain the area prior to the THR to the same structual integrity as the RWY. Therefore, if the operator wants to save a quid, he won't bother to spend money on it as it deteriorates - short of patching potholes, etc.
I think this might suggest that you will never know the actual strength of the area before the displaced THR.
Thread Starter
Join Date: Aug 2002
Location: Caribbean
Posts: 17
Likes: 0
Received 0 Likes
on
0 Posts
If we're talking standards, rather than specifics, the pre threshold area is part of the movement area, and must me maintained as such. If it's condition deteriorates, and it becomes unfit for surface movement of aircraft, they would have to remark it with chevrons, or x's.
If we're talking specifics, rather than standards, lets take a step back to reality. We're talking about light aircraft here. Prior to there being a runway at this location there was a piece of dirt, which seemed to have enough surface integrity to support light aircraft. To throw 12 inches of pavement over that dirt, and say the first 600 ft is unfit is ridiculous.
Again, I'm in no way advocating 747's landing before displaced thresholds.
On a different note..
I found an interesting airport diagram in the UK AIP for Denham. AD 2-EGLD-1-3. It has two runways. In the section for 'local regulations' it states.......
"a public road adjacent to the aerodrome boundary crosses the approach to runway 24. Aircraft should not descend below the glidepath, nor touch down before the displaced threshold."
Now, this is a note for runway 24 ONLY, if this is infact regular law, why would it have to be stated as such? They don't quote and other 'standard regulations' in this section, nor on any other diagrams I looked at.
According to the locate authority, isn't this 'basic aviation knowledge'?? Why would it have to be listed with other irregularities??
If we're talking specifics, rather than standards, lets take a step back to reality. We're talking about light aircraft here. Prior to there being a runway at this location there was a piece of dirt, which seemed to have enough surface integrity to support light aircraft. To throw 12 inches of pavement over that dirt, and say the first 600 ft is unfit is ridiculous.
Again, I'm in no way advocating 747's landing before displaced thresholds.
On a different note..
I found an interesting airport diagram in the UK AIP for Denham. AD 2-EGLD-1-3. It has two runways. In the section for 'local regulations' it states.......
"a public road adjacent to the aerodrome boundary crosses the approach to runway 24. Aircraft should not descend below the glidepath, nor touch down before the displaced threshold."
Now, this is a note for runway 24 ONLY, if this is infact regular law, why would it have to be stated as such? They don't quote and other 'standard regulations' in this section, nor on any other diagrams I looked at.
According to the locate authority, isn't this 'basic aviation knowledge'?? Why would it have to be listed with other irregularities??
Moderator
Without checking back on previous posts ... I think Over run touched on this in saying that approach (and takeoff) obstacle clear surfaces sometimes relate to obstacles which aren't there ... and that includes transient vehicles which often constitute a limiting obstacle for the calculations ....
Displaced thresholds are mostly there for the heavies that require a 3 degree stabilised approach from the outer marker.
As you have noted, light a/c have no problem setting up a one mile final that will also be one mile away from the hill and approximately level with it.
Perhaps somebody well connected objects to a/c turning final over his house -- not that making the turn 600' closer to the runway would make much difference to those below.
Before it was converted into a construction equipment parking area, I often flew out of a strip with the threshold 50' away from the road. When landing I looked both ways before crossing the street
As you have noted, light a/c have no problem setting up a one mile final that will also be one mile away from the hill and approximately level with it.
Perhaps somebody well connected objects to a/c turning final over his house -- not that making the turn 600' closer to the runway would make much difference to those below.
Before it was converted into a construction equipment parking area, I often flew out of a strip with the threshold 50' away from the road. When landing I looked both ways before crossing the street