Performance requirements at time of dispatch
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Joined: May 2010
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From: UK
Performance requirements at time of dispatch
Hi, does anyone understands the logic of why you could dispatch to a runway that is contaminated as long as you have 2 alternates planned. But you are not allowed to apply this logic to a runway that is dry/wet.
(both under most favorable, no wind conditions)
(both under most favorable, no wind conditions)
Flight prep instructionsLanding
The maximum landing weight of the aeroplane for the destination, destination alternate, fuel ERA and re-dispatch or re-clearance aerodrome(s) must be limited as follows: 1. Maximum weight for the elevation and temperature at the ETA resulting from approach climb, landing climb or maximum weight for operations with Decision Height (DH) below 200 ft. Possible resulting limitations are published in OM Part B and OM Part C3. 2. Maximum weight for the elevation, forecasted wind and expected runway condition at the Estimated Time of Arrival (wet, dry or contaminated), the aeroplane shall: a. Firstly, land on the most favourable runway (normally the longest) in still air. Regardless of the wind conditions, the maximum landing mass for an aerodrome/aeroplane configuration at a particular aerodrome cannot be exceeded; b. Secondly, land on the runway most likely to be assigned considering the probable wind speed and direction and the ground handling characteristics of the aeroplane and considering other aids such as landing aids and terrain. The expected wind, ATC and noise abatement procedures, may indicate the use of a different runway. These factors may result in a lower landing mass than permitted under (a) in which case dispatch should be based on this lesser mass.
3. If unable to comply with point (2)(a) above for the destination aerodrome where the appropriate weather reports or forecasts indicate that the runway at the Estimated Time of Arrival may be dry or wet and where a landing depends upon a specific wind component, the aeroplane shall not be dispatched.
4. If unable to comply with point (2)(a) above for the destination aerodrome where the appropriate weather reports or forecasts indicate that the runway at the Estimated Time of Arrival may be contaminated and where a landing depends upon a specific wind component, the aeroplane shall only be dispatched if two alternate aerodromes are selected which permits full compliance with all landing requirements above.
5. When the appropriate weather reports or forecasts indicate that the runway at the estimated time of arrival may be contaminated, the LDA shall be at least the landing distance determined in accordance with OM Part B (FCOM) Performance sections for wet runways, or at least 115 % of the landing distance determined in accordance with approved contaminated landing distance data in OM Part B (FCOM), whichever is greater.
6. If unable to comply with (2)(b) above for the destination aerodrome, the aeroplane may be dispatched if one destination alternate aerodrome is selected which permits full compliance with all landing requirements above and the dispatch landing performance requirements specified in the FCOM. the FCOM. Points 2 to 6 are summarized in the runway suitability check table below:
Runway At time of dispatch, check for ETA
Most favorable, no wind | and | Most likely, probably wind
If unable to comply:
Dry No dispatch | 1 Alternate
Wet No dispatch | 1 Alternate
Contaminated 2 Alternates | 1 Alternate
The maximum landing weight of the aeroplane for the destination, destination alternate, fuel ERA and re-dispatch or re-clearance aerodrome(s) must be limited as follows: 1. Maximum weight for the elevation and temperature at the ETA resulting from approach climb, landing climb or maximum weight for operations with Decision Height (DH) below 200 ft. Possible resulting limitations are published in OM Part B and OM Part C3. 2. Maximum weight for the elevation, forecasted wind and expected runway condition at the Estimated Time of Arrival (wet, dry or contaminated), the aeroplane shall: a. Firstly, land on the most favourable runway (normally the longest) in still air. Regardless of the wind conditions, the maximum landing mass for an aerodrome/aeroplane configuration at a particular aerodrome cannot be exceeded; b. Secondly, land on the runway most likely to be assigned considering the probable wind speed and direction and the ground handling characteristics of the aeroplane and considering other aids such as landing aids and terrain. The expected wind, ATC and noise abatement procedures, may indicate the use of a different runway. These factors may result in a lower landing mass than permitted under (a) in which case dispatch should be based on this lesser mass.
3. If unable to comply with point (2)(a) above for the destination aerodrome where the appropriate weather reports or forecasts indicate that the runway at the Estimated Time of Arrival may be dry or wet and where a landing depends upon a specific wind component, the aeroplane shall not be dispatched.
4. If unable to comply with point (2)(a) above for the destination aerodrome where the appropriate weather reports or forecasts indicate that the runway at the Estimated Time of Arrival may be contaminated and where a landing depends upon a specific wind component, the aeroplane shall only be dispatched if two alternate aerodromes are selected which permits full compliance with all landing requirements above.
5. When the appropriate weather reports or forecasts indicate that the runway at the estimated time of arrival may be contaminated, the LDA shall be at least the landing distance determined in accordance with OM Part B (FCOM) Performance sections for wet runways, or at least 115 % of the landing distance determined in accordance with approved contaminated landing distance data in OM Part B (FCOM), whichever is greater.
6. If unable to comply with (2)(b) above for the destination aerodrome, the aeroplane may be dispatched if one destination alternate aerodrome is selected which permits full compliance with all landing requirements above and the dispatch landing performance requirements specified in the FCOM. the FCOM. Points 2 to 6 are summarized in the runway suitability check table below:
Runway At time of dispatch, check for ETA
Most favorable, no wind | and | Most likely, probably wind
If unable to comply:
Dry No dispatch | 1 Alternate
Wet No dispatch | 1 Alternate
Contaminated 2 Alternates | 1 Alternate
Joined: Apr 2003
Aviation Qualifications: ATPL
Posts: 3,652
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From: Europe
Maybe because of your quite justified expectation that the reported 3 meters of overnight snow will be cleared by the time you come in to land? Only then can an accurate performance assessment be made. Compare that to a dry runway: if you know before departure that you cannot land within the regulated LD, then what's the point of departing to that runway?
Joined: Sep 2004
Aviation Qualifications: ATPL(H)
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From: Canada
My lord - that is some of the most horribly written bafflegab I have ever seen!
I envisage a crew, in dubious meteorological circumstances, with the AFM, OMA, OMB, Airdrome charts, METARS, TAFs, Area forecasts, Ouija Board and Magical Mystery Orb to hand trying to figure out whether to go, delay, cancel, flip a coin or just resign and head for the bar.
An excellent example of micro-management at maxi-distance. ( “If all goes well we are management geniuses, if it doesn’t there is something in the fine print or vague reference to hang the crew with! Bonuses for the management team in any case.” )
I envisage a crew, in dubious meteorological circumstances, with the AFM, OMA, OMB, Airdrome charts, METARS, TAFs, Area forecasts, Ouija Board and Magical Mystery Orb to hand trying to figure out whether to go, delay, cancel, flip a coin or just resign and head for the bar.
An excellent example of micro-management at maxi-distance. ( “If all goes well we are management geniuses, if it doesn’t there is something in the fine print or vague reference to hang the crew with! Bonuses for the management team in any case.” )
Joined: Jan 2006
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From: Between a rock and a hard place
Are these your company specific regulations? Our OM-A makes no difference between dry/wet/contaminated.
If you can't land on the most likely runway given the wind - Dispatch OK with 1 alternate.
If you can't land on the most favourable runway in no wind - Dispatch OK with 2 alternates.
Apologies for not answering your question, it just got me thinking as to who made that up?
If you can't land on the most likely runway given the wind - Dispatch OK with 1 alternate.
If you can't land on the most favourable runway in no wind - Dispatch OK with 2 alternates.
Apologies for not answering your question, it just got me thinking as to who made that up?
Joined: Feb 2000
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From: 500 miles from Chaikhosi, Yogistan
As someone responsible for writing and updating OMs, can I say that is some of the most unfit for purpose verbiage (even with proper formatting) I have seen in a long time.
The purpose of an OM is like a babel fish. It should take arse covering legislative NAA legalese and translate it into clear and concise words to the simplest pilot in your cohort to accurately interpret under time pressure.
If that’s as good as I could come up with I’d stand down from my OM authorship. You have my sympathies.
The purpose of an OM is like a babel fish. It should take arse covering legislative NAA legalese and translate it into clear and concise words to the simplest pilot in your cohort to accurately interpret under time pressure.
If that’s as good as I could come up with I’d stand down from my OM authorship. You have my sympathies.
Joined: Sep 1999
Posts: 615
Likes: 8
From: Middle England
FFS.
I used to dispatch to airfields where no SNOTAM was available because the airfield was closed at the time of departure. 10 hour long haul flight to somewhere at -26 in heavy snow. We always went on the basis that by the time we got there, the runway would be cleared and open.
This **** makes me look forward to the day I retire. Where did common sense go?
I used to dispatch to airfields where no SNOTAM was available because the airfield was closed at the time of departure. 10 hour long haul flight to somewhere at -26 in heavy snow. We always went on the basis that by the time we got there, the runway would be cleared and open.
This **** makes me look forward to the day I retire. Where did common sense go?
Joined: Apr 2003
Aviation Qualifications: ATPL
Posts: 3,652
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From: Europe
Are these your company specific regulations? Our OM-A makes no difference between dry/wet/contaminated.
If you can't land on the most likely runway given the wind - Dispatch OK with 1 alternate.
If you can't land on the most favourable runway in no wind - Dispatch OK with 2 alternates.
Apologies for not answering your question, it just got me thinking as to who made that up?
If you can't land on the most likely runway given the wind - Dispatch OK with 1 alternate.
If you can't land on the most favourable runway in no wind - Dispatch OK with 2 alternates.
Apologies for not answering your question, it just got me thinking as to who made that up?
Same with making no difference between dry/wet/contaminated runways. The added regulatory factors might be inconsequential for your specific operation and runways, but might make the difference between yes or no dispatch for another operator.
Last edited by PENKO; 18th December 2024 at 20:22.
Joined: Apr 2003
Aviation Qualifications: ATPL
Posts: 3,652
Likes: 492
From: Europe
FFS.
I used to dispatch to airfields where no SNOTAM was available because the airfield was closed at the time of departure. 10 hour long haul flight to somewhere at -26 in heavy snow. We always went on the basis that by the time we got there, the runway would be cleared and open.
This **** makes me look forward to the day I retire. Where did common sense go?
I used to dispatch to airfields where no SNOTAM was available because the airfield was closed at the time of departure. 10 hour long haul flight to somewhere at -26 in heavy snow. We always went on the basis that by the time we got there, the runway would be cleared and open.
This **** makes me look forward to the day I retire. Where did common sense go?
As someone responsible for writing and updating OMs, can I say that is some of the most unfit for purpose verbiage (even with proper formatting) I have seen in a long time.
The purpose of an OM is like a babel fish. It should take arse covering legislative NAA legalese and translate it into clear and concise words to the simplest pilot in your cohort to accurately interpret under time pressure.
If that’s as good as I could come up with I’d stand down from my OM authorship. You have my sympathies.
The purpose of an OM is like a babel fish. It should take arse covering legislative NAA legalese and translate it into clear and concise words to the simplest pilot in your cohort to accurately interpret under time pressure.
If that’s as good as I could come up with I’d stand down from my OM authorship. You have my sympathies.
Joined: May 2007
Aviation Qualifications: ATP+Mil
Posts: 108
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From: Somewhere at the Milky Way
The way i understand this is: first (left column) is for the longest runway available with no wind. The second column is for the most probable runway (but not necessarily the longest one) accounting for probable winds. The second column caters for uncertainty as this runway might change if the wind changes.
If you cannot make it into the longest runway, no wind, dry or wet, then you can´t dispatch as this is the life saver case. Then, for the most probable runway, as you might not make it to other runway if wind changes, then you need an alternate. Amsterdam with its multiple lay-out runways comes into my mind.
The contaminated case I am with you, the contamination might clear once you arrive, but just in case, there are 2 other options available.
Indeed it is written like hell, I think in EU text could be written easier to understand, but then where would all the bureaucrats and lawyers go?
If you cannot make it into the longest runway, no wind, dry or wet, then you can´t dispatch as this is the life saver case. Then, for the most probable runway, as you might not make it to other runway if wind changes, then you need an alternate. Amsterdam with its multiple lay-out runways comes into my mind.
The contaminated case I am with you, the contamination might clear once you arrive, but just in case, there are 2 other options available.
Indeed it is written like hell, I think in EU text could be written easier to understand, but then where would all the bureaucrats and lawyers go?
Joined: Mar 2012
Posts: 2,605
Likes: 154
From: Having a margarita on the beach
as already mentioned above the idea is if you dispatch to a destination with a dry or wet runway You must be able to satisfy the dispatch landing criteria on the most favorable runway. Example: summer time, you fly at night to a greek island on a fully loaded A321/B738. Runway 36/18. Calculations done for the most favorable runway with no winds: good to go. Imagine only Runway 36 has an IAP and 18 nothing, no circling or visual allowed. Current winds are likely to assign you 36 with max tailwind. Dispatch performances are red. You can dispatch legally with a suitable alternate as prescribed in the AMC as with no wind you would be good to go. Of course you can reduce the weights and so on to fit on Rwy 36, but we are talking about legality rather than operational effects. By the time you get there your IFLD might give you thumbs up. Same story if the runway is wet.
Now, if your landing dispatch results are red even on the most favorable runway with no winds, you have to do something about it, i.e. reduce payload. It's mainly common sense, you can't dispatch somewhere where the calculations done prior to the flight are a no-no.
On a contaminated runway chances are that the runway will be cleared and/or better RWYCC by the time you get there. So you are good to go even if you don't fit in the most favorable runway but you need more safety nets, i.e. 2 alternates.
Joined: Jan 2008
Posts: 99
Likes: 4
From: U.K
My ex company thought it acceptable to dispatch to an airfield that was out of dispatch limits if you had 2 alternates.
You could then land there even if the conditions had not changed by then using actual landing distance as you were now flying and not in the dispatch phase!
Was always a good conversation piece, what would you do, with FOs about do a command course.
You could then land there even if the conditions had not changed by then using actual landing distance as you were now flying and not in the dispatch phase!
Was always a good conversation piece, what would you do, with FOs about do a command course.
Joined: Jun 2009
Aviation Qualifications: ATPL
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From: Asia
3. If unable to comply with point (2)(a) above for the destination aerodrome where the appropriate weather reports or forecasts indicate that the runway at the Estimated Time of Arrival may be dry or wet and where a landing depends upon a specific wind component, the aeroplane shall not be dispatched.
4. If unable to comply with point (2)(a) above for the destination aerodrome where the appropriate weather reports or forecasts indicate that the runway at the Estimated Time of Arrival may be contaminated and where a landing depends upon a specific wind component, the aeroplane shall only be dispatched if two alternate aerodromes are selected which permits full compliance with all landing requirements above.
4. If unable to comply with point (2)(a) above for the destination aerodrome where the appropriate weather reports or forecasts indicate that the runway at the Estimated Time of Arrival may be contaminated and where a landing depends upon a specific wind component, the aeroplane shall only be dispatched if two alternate aerodromes are selected which permits full compliance with all landing requirements above.
(2)(a): Firstly, land on the most favourable runway (normally the longest) in still air.
If you cannot comply with (2)(a) but can comply with (2)(b), you have taken advantage of a strong headwind in order to apply the dispatch planning factors and land at an airport whereby under still wind you wouldn't be able to access. If it was just a case of having a forecast tailwind on the probable runway, you could still comply with (2)(a) and dispatch. If you cannot comply with (2)(a) then you are gaining a performance advantage purely from a strong headwind onto a runway that is marginal for your type and the regulations prevent you from having a go. Imagine R09, wet, wind 090/35 and the runway has an LDA of 2000m, and you have a still wind LDR of 2100m. Taking into account half the headwind, you now have an LDR of 1900m. The only way you can land on that wet runway is because of the headwind - you cannot satisfy (2)(a), so you can't go.
With a contaminated runway, I would suggest that braking action has a much greater effect on landing distance than 50% of the forecast wind, and as it is usually derived from dry/wet runway data with considerable factorisation is therefore much more of a guidance where you should tread with caution. Therefore dispatch is permitted with two alternates, and on you go, brave commander.
Thread Starter
Joined: May 2010
Posts: 6
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From: UK
Thanks all for the input and clarifying, much appreciated. It does make sense indeed that you can only plan for an airport with a runway (in favourable conditions) on which you can actually land; otherwise, there is no point in going. Or in the contaminated case, as there is a possibility it will be cleared by the time you get there. But with the added safety layer of two alternates.
