PDA

View Full Version : ASDA < TORA?


rcav8r
28th Feb 2012, 22:31
I was glancing through the KATL AFD and noticed on all rwys the ASDA is less than the TORA. :uhoh:

http://aeronav.faa.gov/pdfs/se_136_9FEB2012.pdf

Can someone explain how this is possible?

While we're on the subject of TORA ASDA, does anyone know off hand which US airport actually has rwys with TORA < ASDA? All the major airports that I'm familiar with have TORA = ASDA (except above example), and typically have blast pads or RSA. Are stopways uncommon in the US?

frankthefrowner
29th Feb 2012, 00:26
The FAA is no longer issuing waivers for Runway End Safety Areas (RESA). As a result, some airports are having to use as ASDA less than TORA. Jepp & FMS normally do not publish these reduced ASDA numbers at this time. The AFD is the most reliable resource to find proper declared distances.

rcav8r
29th Feb 2012, 01:07
Thanks for the reply but can you elaborate on how RSA, which to my understanding is area beyond and not including the SWY, affects ASDA?

Zeffy
29th Feb 2012, 12:05
Thanks for the reply but can you elaborate on how RSA, which to my understanding is area beyond and not including the SWY, affects ASDA?

At locations where the area beyond the end of the pavement cannot be used as a runway safety area -- e.g., water, highway, etc. -- the airport management effectively "saws off" the distant end of the runway, designating ("Declaring") that a portion of the pavement is now part of the RSA and cannot be used in calculation of distance for Accelerate Stop.

See FAA AIM 4-3-6-c (http://www.faa.gov/air_traffic/publications/ATpubs/AIM/aim0403.html#aim0403.html.6)

and-
Runway safety area - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Runway_safety_area)
http://www.faa.gov/airports/airport_safety/certalerts/media/cert0905.pdf
http://legacy.icao.int/nacc/meetings/2007/9ccardca/9CCARDCAip07.pdf

bookworm
29th Feb 2012, 14:03
So what's the justification for allowing an aircraft to have its wheels on the pavement in the RSA when approaching Vr at the end of its take-off run, but not when slowing to a halt at the end of its accelerate-stop?

Zeffy
29th Feb 2012, 14:50
So what's the justification for allowing an aircraft to have its wheels on the pavement in the RSA when approaching Vr at the end of its take-off run, but not when slowing to a halt at the end of its accelerate-stop?

I'm not certain that I understand the question, but TORA does not permit that.

Please refer to the cites above.

From the AIM:(1) Takeoff Run Available (TORA) – The runway length declared available and suitable for the ground run of an airplane taking off.

The TORA is typically the physical length of the runway, but it may be shorter than the runway length if necessary to satisfy runway design standards. For example, the TORA may be shorter than the runway length if a portion of the runway must be used to satisfy runway protection zone requirements.

rcav8r
29th Feb 2012, 15:56
I believe what he's trying to ask is why the 'sawed off' part of the pavement that is now part of the RSA, not to be allowed as part of ASDA calcs, but remains available for TORA.

Zeffy
29th Feb 2012, 16:20
It is NOT available for TORA.

Please read the last sentence of the definition above.

rcav8r
29th Feb 2012, 16:23
If it weren't available for TORA this thread wouldn't exist in the first place.

Going back to the KATL AFD. You can see TORA is greater than ASDA on almost all rwys.

Also, in the second link you provided, the appendix on pg. 3 illustrates such an example where the TORA included 200' of the RSA pavement where as the ASDA did not.

Zeffy
29th Feb 2012, 20:35
rcav8rIf it weren't available for TORA this thread wouldn't exist in the first place.

Going back to the KATL AFD. You can see TORA is greater than ASDA on almost all rwys.

Also, in the second link you provided, the appendix on pg. 3 illustrates such an example where the TORA included 200' of the RSA pavement where as the ASDA did not.

How stupid of me. Next time I'll read the question more carefully prior to posting. :O

My apologies.

The least I can do is provide the illustration of a TORA > ASDA:

http://i202.photobucket.com/albums/aa92/zeffy_bucket/ASDATORAExample.png

As far as the rational is concerned, I can only speculate...

Wouldn't it seem logical that an airplane requiring the full TORA value would be well beyond V1 as it passes the end of the pavement designated as the ASDA limit?

In other words, at the ASDA limit, hasn't the focus of the runway certification switched from stopping safely to achieving a safe flight path?

bookworm
29th Feb 2012, 21:23
How stupid of me.

On the contrary, you've led us to the right documents...

Wouldn't it seem logical that an airplane requiring the full TORA value would be well beyond V1 as it passes the end of the pavement designated as the ASDA limit?

In other words, at the ASDA limit, hasn't the focus of the runway certification switched from stopping safely to achieving a safe flight path?

But isn't that what TODA is all about? Or put another way, in a situation with significant clearway, where TORA, not TODA, is limiting, is it not still about pavement rather than safe flight path.

In practice, is TORA ever limiting?

john_tullamarine
29th Feb 2012, 22:05
Keep in mind that the all the TORA is not going to be used/available for the aircraft roll .. despite what might be inferred from the AIM definition cited.

Depending on the rules in play the use of TORR is that either one third or one half of the airborne distance from liftoff to screen has to be over the TORR .. ie the calculated ground run (which is transparent to the pilot in the AFM) never uses that last bit of the TORR.

ASDR, on the other hand, is serious rubber on pavement stuff.

Can TORR be limiting ? .. depends on the aircraft, runway and ambients. Usually, TOR considerations are hidden in the AFM calculations and, so, tend to be a bit of a mystery for pilots. Some AFMs will provide explicit TOR data .. just depends on OEM practices.

FE Hoppy
29th Feb 2012, 23:54
The RSA came after many runways so in-order to make it fit the ASDA has to be reduced in some places. It's a stopping thing so it doesn't impact the declared going distances of TORA and TODA.

Gin Jockey
1st Mar 2012, 05:03
My head hurt after reading 3 sentences of this thread. :8

You lot would really be a laugh a minute at the bar in the evening. :zzz:

Time for a martini. :E

richjb
3rd Mar 2012, 04:50
Racv8r,

As stated in these replies and in the AIM, airport design standards may require adjustments to the runway’s declared distances. In the event that the full, standard Runway Safety Area (1000’) cannot be obtain, a portion of the runway may be used to obtain the require RSA length. In this case, ASDA and LDA will be reduced as required to obtain this 1000’. The US is the only country currently applying this method to obtain full RSA; however, other countries and ICAO are considering adopting this practice. Another factor that may affect declared distances is the Runway Protection Zone (RPZ), which is designed to limit undesirable activity immediately beyond the runway. To obtain the required RPZ, the TORA may be reduced below the physical runway length. For example, see Concord, CA (KCCR).

True stopways, where ASDA is > TORA & TODA are rare in the US. Glasgow, MT (KGGW) is one airport that has an honest-to-goodness stopway on three of the runway ends. This is one of the few (only?) airport in the US with fully documented and declared stopway, declared being the operative word for use in accelerate-stop distance calculations. To be declared a stopway, the runway must have the stopway noted in the A/FD remarks and have published declared distances for that runway (ref: AC 150/5300-13).

Unfortunately, there are some aberrations in declared distances at some US runways. Detroit Metro (KDTW) being the latest:

02/451 (A1568/12) - RWY 22L TODA 11300. 28 FEB 17:00 2012 UNTIL 03 MAR 20:00 2012. CREATED: 27 FEB
19:45 2012

Declared Distances
Take Off Run Avbl. (TORA) 12,003/12,003
Take Off Dist. Avbl. (TODA) 12,003/12,003
Actl. Stop Dist. Avbl. (ASDA) 12,003/12,003
Lndg. Dist. Avbl. (LDA) 12,003/12,003

For the purpose of takeoff planning, accelerate-stop distance must be less than ASDA, takeoff distance must be less than TODA, and takeoff run must be less than TORA. Use of declared distances that differ from the full, physical runway length requires takeoff data that can take advantage of an un-balanced V1 speed and unbalanced field length calculation. For those airplane types that provide only balanced field takeoff data based on a balanced field V1 speed (within certification limitations), then the balanced field takeoff distance or runway limited takeoff weight must limited by the most restrictive of the ASDA, TORA, or TODA length.


Rich Boll
Wichita, KS

OverRun
3rd Mar 2012, 04:54
Hold up chaps. There is something not quite right here. I haven't got it fully worked out yet, but thought I'd post my query in the interim.

There may be something in the difference between RESA and RSA. RESA in its ICAO implementation is from the strip end. RSA in the FAA implementation is from the runway end. So with the RSA, it is easy to fiddle with the runway length independently of the strip, and so it is possible to have the ASDA less than the TORA.

But with the ICAO RESA, this starts from the strip end which is at least 60m (200') beyond the TORA. So under ICAO rules, if RESA is needed and cannot be built, the TODA (and thus the TORA) have to be artificially reduced to provide the RESA length. This also probably means that some stopway has been created consisting of the now-redundant pavement/strip. The stopway is not included on the TORA or TODA, but can be included in the ASDA calculation. So the ASDA can be longer than the TORA and TODA, but never in the ICAO system can it be < TORA.

I'm welcoming constructive comments here, because this rather mirrors an intractable runway problem in Oz that some of us have got at present.

richjb
3rd Mar 2012, 12:44
OveRun,

In FAA parlance, the RSA encompasses the entire runway. The RSA width limits may be identified by the runway hold short signs as the must be located no closer to the runway than the RSA limit. There’s a takeoff RSA that extends beyond the departure end of the runway and a landing RSA that extends out before the approach end of the runway. However, if the runway is operationally bi-directional the takeoff RSA for both runway ends establishes the RSA length beyond each runway end. The illustration shown in the CARDAip07.pdf ICAO document linked earlier in this thread depicts this concept.

In the US, the RSA is intended to contain the aircraft in the event of runway excursion, laterally or off the ends. It must be graded and constructed (does not need to be pavement) to support the aircraft without undue risk of damage to the aircraft in the event of such an excursion. When the airport geography does not allow the airport operator to obtain the full RSA length beyond the runway end, then FAA allows the operator to declare a reduced ASDA and LDA to obtain the required length (or obtain as much as practical while not adversely impacting the runway’s usability).

In the US, ASDA may be less than TORA or TODA as necessary to obtain the required RSA length. My understanding is that in ICAO Annex 14, ASDA may not be less than TORA or TODA.

On another note, I failed to mention in my previous post that TODA may be reduced to less than the full, physical runway length (and less than TORA) if by doing so the airport operator can obtain a clear 40:1 OCS as defined in AC 150/5300-13, Airport Design (not TERPS…closely related, but different 40:1 surface). The allows the airport operator to establish a runway length that the FAA TERPS procedure designers will use in evaluating obstacles in the TERPS takeoff Initial Climb Area (ICA) and may result in the elimination of 40:1 TERPS OCS penetrations that would result in non-standard takeoff minimums and/or use of a takeoff climb gradient on a SID. There are some airports (I believe that one example may be found at Memphis, KMEM) where this technique is applied.

Rich

rcav8r
3rd Mar 2012, 14:13
richjb,

If I'm understanding it correctly, RSA compliance, at least in the US, is implemented by the FAA on a case by case basis?

Take KDCA for example, its rwys are all within 1000' of either the river or a highway, yet is able to retain rwy length declared distances.

Sir George Cayley
3rd Mar 2012, 16:49
In the UK the CAA publish CAP 168 Aerodrome Licensing. In there is a section about RESA which follows the ICAO regs.

SGC

OverRun
4th Mar 2012, 03:10
richjb,

Thanks for the explanation. The FAA RSA is rather like the ICAO runway strip (or more accurately the graded strip). Both are similar dimensions, but different names. The dimensions of both vary with aircraft class (i.e. size).

ICAO matches FAA using a combination of runway strip and RESA. The ICAO runway strip for a medium airline jet is typically 150m (500 feet) or more wide and runs the full length of the runway to extend 60m (200 feet) beyond the end of the runway at each end. The RESA starts beyond the runway strip at each end and extends at least another 90m (300’) or the recommended 240m (800 feet). It sort of matches the FAA’s RSA which I show below using the image from the useful 9CCARDCAip07.pdf reference you mentioned.

http://www.profemery.info/RSA.jpg
FAA runway safety area


http://www.profemery.info/RESA.jpg
ICAO runway end safety area

BTW I say typical because there are many ICAO runway strips for airline aircraft which are 300m (1000 feet) wide, and some which are 300m (1000 feet) wide but only the central 150m (500 feet) is graded and constructed for the passage of an aircraft without undue risk.

However there are still a number of subtle differences between FAA and ICAO here, and it is important not to blindly copy from one to the other (i.e. RSA is much wider beyond the end of the ICAO strip; RESA is stronger pavement).

richjb
4th Mar 2012, 15:19
FAA stopped issuing waivers to the RSA standards a few years back and published Order 5200.8 in 1999 addressing the process to assess and address RSAs. Over the last several years, US airports subject to part 139 and FAA airport funding have worked to address substandard RSA. Some airports like, DCA and MDW were known to be problematic with respect to full RSA compliance. The availability of arresting systems EMAS have dramatically helped address these runway ends where airport geometry limits the space available for RSA extension. Simply reducing the ASDA is not always a solution, since by doing so one can make the runway not economically viable for air carrier operations.

To answer your question, RSA compliance is mandatory and FAA no issues waivers to the standard like they did in the past. All airports are required to come into full compliance to the maximum extent practicable and to develop a plan to do so. However, there will be some airports where full RSA compliance is not possible. Where DCA fits into this process, I don’t know.

Rich

richjb
4th Mar 2012, 15:22
Thanks for the explanation!

Most of the information that I have on ICAO runway standards is from Annex 14. Is there another Annex or other guidance provided by ICAO on airport design standards?

Thanks again,

Rich

OverRun
5th Mar 2012, 09:53
Rich,

Annex 14 is the main ICAO document on airport design standards. There is a handy link in the sticky’d threads at the top of ‘Tech Log’ to an electronic version of it.

There are some other ICAO documents but these are peripheral and 99.9% of airport design can be done using Annex 14. The other documents go into more detail in certain areas. I use mainly Parts 1-3 of the following:

Aerodrome Design Manual (Doc 9157)
Part 1 — Runways
Part 2 — Taxiways, Aprons and Holding Bays
Part 3 — Pavements
Part 4 — Visual Aids
Part 5 — Electrical Systems

Some other airport aspects are covered in the following, but some of them are quite dated and not of as much value:

Airport Planning Manual (Doc 9184)
Part 1 — Master Planning
Part 2 — Land Use and Environmental Control
Part 3 — Guidelines for Consultant/Construction Services

Airport Services Manual (Doc 9137)
Part 1 — Rescue and Fire Fighting
Part 2 — Pavement Surface Conditions
Part 3 — Bird Control and Reduction
Part 4 — Fog Dispersal (withdrawn)
Part 5 — Removal of Disabled Aircraft
Part 6 — Control of Obstacles
Part 7 — Airport Emergency Planning
Part 8 — Airport Operational Services
Part 9 — Airport Maintenance Practices

There is a heliport manual, but Annex 14 Vol 2 also covers heliports. The manual is:
Heliport Manual (Doc 9261).

Cheers
OverRun

NotaLOT
5th Mar 2012, 10:42
Hi All,

I am also from the ICAO part of the world. I have read through the explanations regarding ASDA sacrifice for RSA, but there is still one thing I don't understand. In such a constrained case surely increasing the longitudinal size of RSA requires not only a decrease in ASDA, but also in TORA?

john_tullamarine
5th Mar 2012, 19:21
not only a decrease in ASDA, but also in TORA?

Philosophically, ASDA is critical because the aircraft is on the ground throughout ASDR. However, the last part of TORR is airborne (by definition) so that may permit a lesser concern in regard to declared TORA.

Clearly, were the decrement to be significant, TORA would need to be revisited but, for the typical short distances involved, the aircraft still is going to be airborne for that remaining TORA delta.

Sir George Cayley
7th Mar 2012, 19:05
Standards and Recommended Practices. In ICAO language this means shall or should.

So in relation to RESA, the standard is 90m and the recommendation is 240m.

Some states take the recommended value as a requirement although often permit a distance between 90 & 240 if an aeronautical study shows the risk has been reduced to as low as reasonably practicable.

A cursory glance at some rejected take off overruns seems to point at 240m as a norm not 90m.

One area that needs addressing is aircrew electing to stop at either V1 or just above. The Brussels Kalitta 747 is a case in point. Does it suggest that some crew are so concerned that they prefer an overrun to exporting the problem into the air?

SGC

JammedStab
13th Jan 2016, 17:29
LAX notam for runway 24L which is normal length of 10,285'.

!LAX 12/299 LAX RWY 24L DECLARED DIST: TORA 9935FT TODA 9935FT ASDA 8935FT LDA 8362FT. 1512280125-1606012359EST

KLAX airport website info,

"Los Angeles International Airport (LAX) today closed Runway 7R-25L, the first of four runways currently scheduled for maintenance and federally-mandated Runway Safety Area (RSA) improvements. The one-runway-at-a-time construction work is scheduled to last through 2018 and may cause flight delays similar to those experienced during bad weather conditions.
The runway closures and/or temporary shortenings will allow crews to revise grades, construct new runway safety areas, lighting systems, and navigational aids to comply with federal RSA requirements. When runways are closed for RSA work, crews will take advantage of the time to also conduct runway maintenance and rehabilitation.

Following completion of the RSA projects, Los Angeles World Airports (LAWA) will perform additional runway and taxiway maintenance projects. These additional projects are currently in planning and the construction dates, runway closures and other impacts associated with these projects are still being determined.

Closures and/or shortening of LAX’s runways are anticipated to continue over the next three years and are scheduled as follows:

• Runway 7R-25L: March 2015 – April 2015

• Runway 6L-24R: June 2015 – October 2015

• Runway 6R-24L: November 2015 – October 2016

• Runway 7L-25R: October 2016 – June 2017

• Additional Runway Maintenance: Dates To Be Determined

Scheduled dates are subject to change."

underfire
14th Jan 2016, 21:51
For FAA land, the FAA document explaining the differences. Basically the mandated RSA is being put into place, either in reality or by moving the invisible lines..https://www.faa.gov/airports/airport_safety/certalerts/media/cert0905.pdf

In some cases, an airport operator may use declared distances to satisfy the requirement for a runway safety area off a particular runway end. This in effect would shorten the runway length available to be used for ASDA and LDA. (TORA and TODA are never reduced in this situation.) (emphasis added) In other cases, an airport operator may use declared distances different than the paved runway length to satisfy runway protection zone (RPZ) or runway object free area (ROFA) requirements, or to reflect a displaced threshold, clearway, or stopway. See the definitions in AC 150/5300-13 Appendix 14, except note that declared distances are to be listed for all runways at certificated airports, not limited to those cases where it is impracticable to provide the required RSA, ROFA, or RPZ as stated in the AC. Additionally, the contents of CERTALERT 00-03 (Stopway), as amended in accordance with this CERTALERT, is attached as a reminder of the criteria to use for designating a stopway.

Pilots and airplane operators’ performance engineers need this information for calculating their allowable takeoff and landing weights and speeds. Therefore, this information needs to be readily available.

The TODA does not take into account obstacles (other than those considered in meeting the RPZ, ROFA, and clearway requirements) that may be off the departure end of the runway. Therefore, the pilot is responsible for determining if the aircraft can clear those obstacles according to the applicable airplane operating regulations and airplane performance data.

Omjeeprasad
11th Apr 2019, 09:46
As per ICAO, Annex-14: Accelerate-stop Distance Available (ASDA) is "The length of the take-off run available (TORA) plus the length of the stopway, if provided". Which means that
ASDA = TORA + Stopway (If provided).

Hence, It is very clear that in any case the ASDA can not be less that the TORA of the associated RWY.

Cheers
Om Jee Prasad

Sepp
11th Apr 2019, 17:57
...
ASDA can not be less that the TORA of the associated RWY.

Cheers
Om Jee Prasad

Meanwhile, at KATL: Rwy 08L/26R (https://uk.flightaware.com/resources/airport/KATL/runway/08L/26R) ASDA 8800 ft., TORA 9000 ft.

Smythe
11th Apr 2019, 18:11
ASDA=TORA - stopway (if you need part of the runway as the stopway.)

8800=9000-200.

KPSP RW13R: TORA:10000 TODA:10000 ASDA:9857 LDA:6857

Musket90
11th Apr 2019, 18:29
Whoever calculated the ASDA distance to be less than TORA is wrong. ASDA value is either equal to TORA (when no stopway provided) or more (when stopway is provided). The origin of the RESA starts 60m (runway strip) beyond the end of TORA or ASDA. Check ICAO Annex 14.

Sepp
11th Apr 2019, 18:47
Whoever calculated the ASDA distance to be less than TORA is wrong. ASDA value is either equal to TORA (when no stopway provided) or more (when stopway is provided).
...

Not according to the FAA AIM. Witness this diagram (http://www.faraim.org/aim/aim-4-03-14-196.html). Note the figures for rwy 09 and associated explanation. ASDA can be shorter than TORA if part of the runway has to be "used up" to satisfy one or more design requirements.

Smythe
11th Apr 2019, 18:48
one should note that the RW examples given are FAA, not ICAO.

https://cimg6.ibsrv.net/gimg/pprune.org-vbulletin/861x567/hkvho6e_8f043b0420e610659599566890e19f9e2e0c54d4.jpg

pattern_is_full
11th Apr 2019, 19:06
Of note: ATL 08L/26R has HOLD markings right across the runway 400 feet in from the threshold keys at each end. ==============

https://www.google.com/maps/place/Hartsfield-Jackson+Atlanta+International+Airport/@33.6495301,-84.4374408,309m/data=!3m1!1e3!4m5!3m4!1s0x0:0x4117a3ef1892b048!8m2!3d33.6407 282!4d-84.4277001

Similar to LAHSO markings (except no crossing runway in existence). No idea why (any local knowledge?).

What effect do such markings have on ASDA calculation?

NB: KATL 09R/27L has similar markings - and also has ASDA < TORA (slightly).

Musket90
11th Apr 2019, 19:42
Interesting. These 08L/26R markings are taxiway/runway holding position "pattern A" markings and it appears they have associated signs. I can only think that they are provided for ATC to hold an aircraft at these positions on the runway to give priority to aircraft on the crossing taxiway at the runway ends. An odd situation as runway movements would normally have priority over crossing traffic, unless the runway is sometimes used as a taxiway.

Regarding TORA/ASDA, maybe FAA file a difference with ICAO on this but I don't understand the logic.

Smythe
11th Apr 2019, 21:51
In the case of the USA, the FAA Airport Design requirements specify the minimum dimensions of a ‘Runway Safety Area’ which includes the Runway Strip defined by ICAO. Since 2002, these requirements have included a Runway Safety Area at each end of a runway which takes account of the direction of runway use when specifying the minimum length of the runway end element. The basic standard is defined for instrument runways used by transport aircraft and any such runway with an ‘approach visibility minima’ of less than 1200 metres and is 300 metres for the overrun case and 180 metres for the undershoot case. It is permissible to reduce the overrun case to 180 metres if the runway has either instrument or visual vertical guidance aids and an Engineered Materials Arresting System (https://www.skybrary.aero/index.php/Engineered_Materials_Arresting_Systems) (EMAS) which can stop an aircraft which leaves the end of the runway at up to 70 kts groundspeed is provided.

It can be seen that the FAA overrun requirement (300 metres) is equivalent to the ICAO RESA Recommended Practice plus the required Runway Strip (also totalling 300 metres) but that the FAA undershoot requirement (180 metres) is only slightly more than the ICAO RESA Standard plus the required runway strip (totalling 150 metres).