Wet V1
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Beware of Cowboys
Just to clear the air on a few well considered responses........
BizJetJock, Yes, I'm well aware that the JAR does require that the normal 'Dry' Takeoff Weight is the upper limit of Wet Runway considerations. You are right, it IS a geographical difference, not all countrys make that distinction in their legislation. In my Performance number crunching, I use a composite of JAR 25, FAR 25, and the Australian CAO 20.7.1B. There are various reasons for this (mainly to satisfy all of the regulatory authorities), but also as a safety issue.
In my earlier computer runs to calculate RTOWs, I encountered about 10% of cases where the Wet RTOW exceeded the Normal Dry RTOW. After much thought, I realised that 2 major safety margins are eliminated for Wet operations, thus leading to better weights with Wet figures, as Denti and PBL might say - "Daran habe ich gar nicht gedacht!". From that time onwards, I've used the 'composite legislation' approach.
lion-g asked "Can somebody explain why is there a reduced SAFETY margin for wet runway ?". Normal rules apply to the dry runway condition where (i) one means of stopping the aircraft must be held in reserve. Typically, Reverse Thrust is the reserve means not considered, and it's contribution are a bonus, and (ii) The screen height is reduced from 35 ft to 15 ft.
THE LEGISLATION OBLIGES US TO FOLLOW THE NORMAL DRY RUNWAY RULES, WITH CONCESSION AGAINST THE 2 SAFETY REQUIREMENTS MENTIONED ABOVE ONLY IN THE CASE OF WET RUNWAY OPERATIONS. To do otherwise is patently ILLEGAL.
Let's take a case where the runway is Dry, but you check Wet runway data and find that the 2 RTOW limits are exactly the same. Some cowboys will use the Wet data for an "improved" V1, but have effectively eliminated the afore-mentioned 2 safety considerations REQUIRED - ILLEGAL! If you suffer an engine failure before V1, you have obviously improved your RTO performance even without Reverse Thrust (because of the lower V1). If the failure is recognised a micro-second after V1, your screen height will be 15 ft, which is much less than the MANDATORY 35 ft required for Dry runways.
It is illegal to use a concession outside of the parameters which allow the use of the concession. Do so at your own risk, but please not when I, or my family, are sitting down the back!!!!!!!
Regards (but not to the cowboys),
Old Smokey
BizJetJock, Yes, I'm well aware that the JAR does require that the normal 'Dry' Takeoff Weight is the upper limit of Wet Runway considerations. You are right, it IS a geographical difference, not all countrys make that distinction in their legislation. In my Performance number crunching, I use a composite of JAR 25, FAR 25, and the Australian CAO 20.7.1B. There are various reasons for this (mainly to satisfy all of the regulatory authorities), but also as a safety issue.
In my earlier computer runs to calculate RTOWs, I encountered about 10% of cases where the Wet RTOW exceeded the Normal Dry RTOW. After much thought, I realised that 2 major safety margins are eliminated for Wet operations, thus leading to better weights with Wet figures, as Denti and PBL might say - "Daran habe ich gar nicht gedacht!". From that time onwards, I've used the 'composite legislation' approach.
lion-g asked "Can somebody explain why is there a reduced SAFETY margin for wet runway ?". Normal rules apply to the dry runway condition where (i) one means of stopping the aircraft must be held in reserve. Typically, Reverse Thrust is the reserve means not considered, and it's contribution are a bonus, and (ii) The screen height is reduced from 35 ft to 15 ft.
THE LEGISLATION OBLIGES US TO FOLLOW THE NORMAL DRY RUNWAY RULES, WITH CONCESSION AGAINST THE 2 SAFETY REQUIREMENTS MENTIONED ABOVE ONLY IN THE CASE OF WET RUNWAY OPERATIONS. To do otherwise is patently ILLEGAL.
Let's take a case where the runway is Dry, but you check Wet runway data and find that the 2 RTOW limits are exactly the same. Some cowboys will use the Wet data for an "improved" V1, but have effectively eliminated the afore-mentioned 2 safety considerations REQUIRED - ILLEGAL! If you suffer an engine failure before V1, you have obviously improved your RTO performance even without Reverse Thrust (because of the lower V1). If the failure is recognised a micro-second after V1, your screen height will be 15 ft, which is much less than the MANDATORY 35 ft required for Dry runways.
It is illegal to use a concession outside of the parameters which allow the use of the concession. Do so at your own risk, but please not when I, or my family, are sitting down the back!!!!!!!
Regards (but not to the cowboys),
Old Smokey
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Hi,
Yes Sir !! Got your points loud and clear ! Thank you for your inputs.
Just to digress a bit, on my fleet (AIRBUS), the takeoff off speeds are "fixed" for a certain weight, regardless of WET/DRY/CONTAMINATED/BRAKES DEACTIVATED !!!! The only difference will be the STOP Margin given on the RESULTS page in the LPC.
We are taking off with a very LOW V1 everytime. Even if I put in 8 brakes deactivated into the T/O Calculation, the V-speeds will still be the same!!! Only the MTOW(perf) as well as the STOP MARGIN changes.
Is this legal ?
Regards,
lion-g
Yes Sir !! Got your points loud and clear ! Thank you for your inputs.
Just to digress a bit, on my fleet (AIRBUS), the takeoff off speeds are "fixed" for a certain weight, regardless of WET/DRY/CONTAMINATED/BRAKES DEACTIVATED !!!! The only difference will be the STOP Margin given on the RESULTS page in the LPC.
We are taking off with a very LOW V1 everytime. Even if I put in 8 brakes deactivated into the T/O Calculation, the V-speeds will still be the same!!! Only the MTOW(perf) as well as the STOP MARGIN changes.
Is this legal ?
Regards,
lion-g
Last edited by lion-g; 6th Aug 2010 at 05:43.
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Hi lion-g,
I must admit to deliberately waiting a day or two to respond to you, in the hopes that some Airbus knowledgable person might reply, I'm strictly a BCAR, FAR 25, and CAO 20.7.1B nerd. The JAR I respect greatly, but not done any work with any of their products (apart from plagiarising a few good ideas)
).
All of that is a round-about way of saying that I do not know much about how Airbus do things.
To go to your last sentence "Is this legal ?", yes it is, but quaint, a bit 1950'ish.
Having already admitted to not knowing Airbus' mode d'emploi, my reaction is that they've over-simplified things at the expense of optimisation of Takeoff Weights. As you've said, for a given weight, the speeds are constant irrespective of the other variable conditions. What the Airbus engineering people have now done is to make the MTOW(perf) as well as the STOP MARGIN 'fit' the speeds. That's safe, but off-optimum. On the other side of the Atlantic they would have taken the variable considerations (including MEL) and optimised a Weight / Speed schedule for the condition.
Boeing are 'guilty' of doing the same thing for some MEL conditions (to keep things simple), but for more routine semi-unusual cases such as Wet Runway, optimised a whole new set of data. An example of this would be dispatch with a Hydraulic pump U/S, which directly affects gear retraction time and distance, thus imposing a 1st segment penalty. The technique used would be to use the normal V-Speeds, but apply a weight penalty to the MTOW.
A good idea to wait for a response from an Airboos expert, these remarks are just my thinking out aloud
Regards,
Old Smokey
I must admit to deliberately waiting a day or two to respond to you, in the hopes that some Airbus knowledgable person might reply, I'm strictly a BCAR, FAR 25, and CAO 20.7.1B nerd. The JAR I respect greatly, but not done any work with any of their products (apart from plagiarising a few good ideas)
).All of that is a round-about way of saying that I do not know much about how Airbus do things.
To go to your last sentence "Is this legal ?", yes it is, but quaint, a bit 1950'ish.
Having already admitted to not knowing Airbus' mode d'emploi, my reaction is that they've over-simplified things at the expense of optimisation of Takeoff Weights. As you've said, for a given weight, the speeds are constant irrespective of the other variable conditions. What the Airbus engineering people have now done is to make the MTOW(perf) as well as the STOP MARGIN 'fit' the speeds. That's safe, but off-optimum. On the other side of the Atlantic they would have taken the variable considerations (including MEL) and optimised a Weight / Speed schedule for the condition.
Boeing are 'guilty' of doing the same thing for some MEL conditions (to keep things simple), but for more routine semi-unusual cases such as Wet Runway, optimised a whole new set of data. An example of this would be dispatch with a Hydraulic pump U/S, which directly affects gear retraction time and distance, thus imposing a 1st segment penalty. The technique used would be to use the normal V-Speeds, but apply a weight penalty to the MTOW.
A good idea to wait for a response from an Airboos expert, these remarks are just my thinking out aloud
Regards,
Old Smokey
my reaction is that they've over-simplified things at the expense of optimisation of Takeoff Weights.
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Old Smokey, while i appreciate your knowledge and your experience i think you are not 100% correct on this one.
Lets suppose you are conducting a T/O from Dry Runway with Clearway, using Dry Performance Data. Regulations demand that, when factoring in the clearway, that in the accelerate - go case half of the distance from Liftoff to the point where the 35ft Screenheight is reached must be over the runway (sorry for that formulation, i'll try to provide exact references later). So overhead the Departure End of the Runway, you'll have gained 35ft/2 = 17.5ft height. However, this figure will be a tad lower as climb performence increases with increasing speed and will be almost exact 15ft.
Now lets do the Takeoff again on the very same runway, same conditions but now using Wet Performance Data. The Screenheight is reduced to 15ft, however you are not allowed to factor in the clearway (at least with B777 Performance Tools but i'm thinking this is a general requirement) so when you reach your screenheight of 15ft you'll be at the end of your Take-Off Distance Available which is the Departure End of the Runway.
Exactly the same as when using the Dry Performance Figures! And no reduction in safety.
Now suppose you perform a Take-Off on a runway without clearway eg close-in obstacles. Now using Wet compared to Dry leaves you with less height in the same spot (15ft compared to 35ft) however regulations demand that you cross any obstacle by at least 35ft and make no difference between a Wet and a Dry Runway. That means, that when using Wet Data you still have to achieve 35ft over the first obstacle and thus your climb gradient must be better. This fact is being accounted for in the performance calculation and results in more excess thrust when compared to Dry Runway Data.
So again no reduction in safety.
The only thing which Wet Data really improves is your accelerate - stop performance. Should this result in a higher RTOW compared to a RTOW when using Dry Figures, the latter are used.
So in short, there is no reduction in safety when using Wet compared to Dry Performance Data!!
I stand to be corrected however.
Lets suppose you are conducting a T/O from Dry Runway with Clearway, using Dry Performance Data. Regulations demand that, when factoring in the clearway, that in the accelerate - go case half of the distance from Liftoff to the point where the 35ft Screenheight is reached must be over the runway (sorry for that formulation, i'll try to provide exact references later). So overhead the Departure End of the Runway, you'll have gained 35ft/2 = 17.5ft height. However, this figure will be a tad lower as climb performence increases with increasing speed and will be almost exact 15ft.
Now lets do the Takeoff again on the very same runway, same conditions but now using Wet Performance Data. The Screenheight is reduced to 15ft, however you are not allowed to factor in the clearway (at least with B777 Performance Tools but i'm thinking this is a general requirement) so when you reach your screenheight of 15ft you'll be at the end of your Take-Off Distance Available which is the Departure End of the Runway.
Exactly the same as when using the Dry Performance Figures! And no reduction in safety.
Now suppose you perform a Take-Off on a runway without clearway eg close-in obstacles. Now using Wet compared to Dry leaves you with less height in the same spot (15ft compared to 35ft) however regulations demand that you cross any obstacle by at least 35ft and make no difference between a Wet and a Dry Runway. That means, that when using Wet Data you still have to achieve 35ft over the first obstacle and thus your climb gradient must be better. This fact is being accounted for in the performance calculation and results in more excess thrust when compared to Dry Runway Data.
So again no reduction in safety.
The only thing which Wet Data really improves is your accelerate - stop performance. Should this result in a higher RTOW compared to a RTOW when using Dry Figures, the latter are used.
So in short, there is no reduction in safety when using Wet compared to Dry Performance Data!!
I stand to be corrected however.
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@Parkbremse
not quite.
the difference is in the take off run which include half the distance to 35ft dry but all the distance to 15ft wet. Otherwise clearway is used the same for take off distance.
not quite.
the difference is in the take off run which include half the distance to 35ft dry but all the distance to 15ft wet. Otherwise clearway is used the same for take off distance.
CS 25.113 Take-off distance and take-off run
(a)Take-off distance on a dry runway is the greater of –
(a)Take-off distance on a dry runway is the greater of –
(1) The horizontal distance along the take-off path from the start of the take-off to the point at which the aeroplane is 11 m (35 ft) above the take-off surface, determined under CS 25.111 for a dry runway; or
(2)115% of the horizontal distance along the take-off path, with all engines operating, from the start of the take-off to the point at which the aeroplane is 11 m (35 ft) above the take-off surface, as determined by a procedure consistent with CS25.111. (See AMC 25.113(a)(2), (b)(2) and (c)(2).)
(b)Take-off distance on a wet runway is the greater of –(2)115% of the horizontal distance along the take-off path, with all engines operating, from the start of the take-off to the point at which the aeroplane is 11 m (35 ft) above the take-off surface, as determined by a procedure consistent with CS25.111. (See AMC 25.113(a)(2), (b)(2) and (c)(2).)
(1)The take-off distance on a dry runway determined in accordance with sub-paragraph (a) of this paragraph; or
(2) The horizontal distance along the take-off path from the start of the take-off to the point at which the aeroplane is 4,6 m (15 ft) above the take-off surface, achieved in a manner consistent with the achievement of V2 before reaching 11 m (35 ft) above the take-off surface, determined under CS 25.111 for a wet runway. (See AMC 113(a)(2), (b)(2) and (c)(2).)
(c)If the take-off distance does not include a clearway, the take-off run is equal to the take-off distance. If the take-off distance includes a clearway –(2) The horizontal distance along the take-off path from the start of the take-off to the point at which the aeroplane is 4,6 m (15 ft) above the take-off surface, achieved in a manner consistent with the achievement of V2 before reaching 11 m (35 ft) above the take-off surface, determined under CS 25.111 for a wet runway. (See AMC 113(a)(2), (b)(2) and (c)(2).)
(1)The take-off run on a dry runway is the greater of –
(i)The horizontal distance along the take-off path from the start of the take- off to a point equidistant between the point at which VLOF is reached and the point at which the aeroplane is 11 m (35 ft) above the take-off surface, as determined under CS 25.111 for a dry runway; or
(ii)115% of the horizontal distance along the take-off path, with all engines operating, from the start of the take-off to a point equidistant between the point at which VLOF is reached and the point at which the aeroplane is 11 m (35 ft) above the take-off surface, determined by a procedure consistent with CS25.111. (See AMC 25.113(a)(2), (b)(2) and (c)(2).)
(2)The take-off run on a wet runway is the greater of –(ii)115% of the horizontal distance along the take-off path, with all engines operating, from the start of the take-off to a point equidistant between the point at which VLOF is reached and the point at which the aeroplane is 11 m (35 ft) above the take-off surface, determined by a procedure consistent with CS25.111. (See AMC 25.113(a)(2), (b)(2) and (c)(2).)
(i) The horizontal distance along the take-off path from the start of the take- off to the point at which the aeroplane is 4,6 m (15 ft) above the take-off surface, achieved in a manner consistent with the achievement of V2 before reaching 11 m (35 ft) above the take-off surface, determined under CS 25.111 for a wet runway; or
(ii)115% of the horizontal distance along the take-off path, with all engines operating, from the start of the take-off to a point equidistant between the point at which VLOF is reached and the point at which the aeroplane is 11 m (35 ft) above the take-off surface, determined by a procedure consistent with CS 25.111. (See AMC 25.113(a)(2).)
(ii)115% of the horizontal distance along the take-off path, with all engines operating, from the start of the take-off to a point equidistant between the point at which VLOF is reached and the point at which the aeroplane is 11 m (35 ft) above the take-off surface, determined by a procedure consistent with CS 25.111. (See AMC 25.113(a)(2).)
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Thanks for the reference, this what i was looking for and actually undermines my point. (But stated in clearer english i suppose...)
So:
Dry Runway: TOR = Start of T/O Run until point equidistant between v_lof and the point where 35ft is reached. At that point your height will be 15ft. (paragraph c1(i) )
Wet Runway: TOR = Start of T/O Run to the point where 15ft are reached. (paragraph c2(i) )
Exactly the same. Note that it says Take-Off Run and not Take-Off Distance The difference is that in the WET case your Take-Off is completed at 15ft screenheight so TOR = TOD which is practically the same as disregarding the clearway.
(c)If the take-off distance does not include a clearway, the take-off run is equal to the take-off distance. If the take-off distance includes a clearway –
(1)The take-off run on a dry runway is the greater of –
(i)The horizontal distance along the take-off path from the start of the take- off to a point equidistant between the point at which VLOF is reached and the point at which the aeroplane is 11 m (35 ft) above the take-off surface, as determined under CS 25.111 for a dry runway; or
(ii)115% of the horizontal distance along the take-off path, with all engines operating, from the start of the take-off to a point equidistant between the point at which VLOF is reached and the point at which the aeroplane is 11 m (35 ft) above the take-off surface, determined by a procedure consistent with CS25.111. (See AMC 25.113(a)(2), (b)(2) and (c)(2).)
(2)The take-off run on a wet runway is the greater of –
(i) The horizontal distance along the take-off path from the start of the take- off to the point at which the aeroplane is 4,6 m (15 ft) above the take-off surface, achieved in a manner consistent with the achievement of V2 before reaching 11 m (35 ft) above the take-off surface, determined under CS 25.111 for a wet runway; or
(ii)115% of the horizontal distance along the take-off path, with all engines operating, from the start of the take-off to a point equidistant between the point at which VLOF is reached and the point at which the aeroplane is 11 m (35 ft) above the take-off surface, determined by a procedure consistent with CS 25.111. (See AMC 25.113(a)(2).)
(1)The take-off run on a dry runway is the greater of –
(i)The horizontal distance along the take-off path from the start of the take- off to a point equidistant between the point at which VLOF is reached and the point at which the aeroplane is 11 m (35 ft) above the take-off surface, as determined under CS 25.111 for a dry runway; or
(ii)115% of the horizontal distance along the take-off path, with all engines operating, from the start of the take-off to a point equidistant between the point at which VLOF is reached and the point at which the aeroplane is 11 m (35 ft) above the take-off surface, determined by a procedure consistent with CS25.111. (See AMC 25.113(a)(2), (b)(2) and (c)(2).)
(2)The take-off run on a wet runway is the greater of –
(i) The horizontal distance along the take-off path from the start of the take- off to the point at which the aeroplane is 4,6 m (15 ft) above the take-off surface, achieved in a manner consistent with the achievement of V2 before reaching 11 m (35 ft) above the take-off surface, determined under CS 25.111 for a wet runway; or
(ii)115% of the horizontal distance along the take-off path, with all engines operating, from the start of the take-off to a point equidistant between the point at which VLOF is reached and the point at which the aeroplane is 11 m (35 ft) above the take-off surface, determined by a procedure consistent with CS 25.111. (See AMC 25.113(a)(2).)
Dry Runway: TOR = Start of T/O Run until point equidistant between v_lof and the point where 35ft is reached. At that point your height will be 15ft. (paragraph c1(i) )
Wet Runway: TOR = Start of T/O Run to the point where 15ft are reached. (paragraph c2(i) )
Exactly the same. Note that it says Take-Off Run and not Take-Off Distance The difference is that in the WET case your Take-Off is completed at 15ft screenheight so TOR = TOD which is practically the same as disregarding the clearway.
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Hi,
Engine failure is taken in consideration on takeoff performance. Besides OEI acceleration, are there any other factors that affect takeoff performance and are taken in consideration for the calculation of aircraft performance?
In certain cases such snow, slush, and standing water where both acceleration and stopping are affected. How huge is the payload loss (may be a number if possible)?
Feedback appreciated.
Thank you.
Regards
Engine failure is taken in consideration on takeoff performance. Besides OEI acceleration, are there any other factors that affect takeoff performance and are taken in consideration for the calculation of aircraft performance?
In certain cases such snow, slush, and standing water where both acceleration and stopping are affected. How huge is the payload loss (may be a number if possible)?
Feedback appreciated.
Thank you.
Regards
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In the case of contaminated runways, impingement drag, retardation affects, lateral control and the benefits of ploughing are taken into account. As for an average figure, there isn't really such a thing with today's computerised programs, however with our old Classics we used 10% of the runway limit weight as an average reduction.
However I do stress that under our regulations, contaminated runway data isn't certified so we legally do not have to account for anything, but if we do make corrections, we can calculate takeoff weight without accounting for an engine failure
But there is a difference between legal responsibilities and moral responsibilities.
Mutt
However I do stress that under our regulations, contaminated runway data isn't certified so we legally do not have to account for anything, but if we do make corrections, we can calculate takeoff weight without accounting for an engine failure
But there is a difference between legal responsibilities and moral responsibilities.
Mutt
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Which brings to my mind a question....
In the case of the Southwest accident at Chicago's Midway airport, were these guys landing on a wet runway or a contaminated runway?
Mutt's last post brought this question to mind.....
Fly safe,
PantLoad
Mutt's last post brought this question to mind.....
Fly safe,
PantLoad
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according to the NTSB factual report, the runway surface condition is stated as "snow". So actual conditions seem to have been "contaminated".
edit to add the the final report makes many references to "contaminated" runway in its analysis and recommendations, but I haven't (yet) found an explicit statement "runway was contaminated" or similar, though it seems the only logical conclusion
edit to add the the final report makes many references to "contaminated" runway in its analysis and recommendations, but I haven't (yet) found an explicit statement "runway was contaminated" or similar, though it seems the only logical conclusion
Last edited by Mad (Flt) Scientist; 18th Aug 2010 at 16:49.
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Mad (Flt) Scientist
Thank you....
Also thinking....
Weren't they using their fancy performance laptops to figure landing distance?
I guess I have to read the report....
Point is: Performance data on contaminated surfaces are not certified. You're a test pilot.
Fly safe,
PantLoad
Also thinking....
Weren't they using their fancy performance laptops to figure landing distance?
I guess I have to read the report....
Point is: Performance data on contaminated surfaces are not certified. You're a test pilot.
Fly safe,
PantLoad
Just to add to this. The company I work for had an SOP on one of our fleets to use wet V1s for all performance calculations. This was approved by the CAA. So I don't think its illegal. However the fleet I'm referring to didn't suffer a lack of performance, even at MTOM and one engine, it still went up like a home sick angel.
Moderator
Just talking generally, and not in any way specifically directed toward the CAA.
However, just because Bloggs works for the Regulator doesn't necessarily mean he knows much in respect to what he is talking about .... I've seen a few Regulator folks I wouldn't feed in a fit.
On the other hand some are absolutely superb in their knowledge and competence.
Just a matter of being able to distinguish between one and the other ...
However, just because Bloggs works for the Regulator doesn't necessarily mean he knows much in respect to what he is talking about .... I've seen a few Regulator folks I wouldn't feed in a fit.
On the other hand some are absolutely superb in their knowledge and competence.
Just a matter of being able to distinguish between one and the other ...
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What is a wet runway?.
I ask this because i know that on a dry runway the performance figures are fairly easy to calculate. On a Wet runway it is very different,a lot of things to consider.
In F1 racing as soon as drops of water appear it has an effect on performance. Lap times increase until the cars cannot stay on the track.
On another point i believe that they use statistics to help define the regulations. Most take offs are made in dry conditions,some crews may go a very long time before doing a wet take off. So the chance of an engine failure in wet conditions are very low.
Any comments?.
I ask this because i know that on a dry runway the performance figures are fairly easy to calculate. On a Wet runway it is very different,a lot of things to consider.
In F1 racing as soon as drops of water appear it has an effect on performance. Lap times increase until the cars cannot stay on the track.
On another point i believe that they use statistics to help define the regulations. Most take offs are made in dry conditions,some crews may go a very long time before doing a wet take off. So the chance of an engine failure in wet conditions are very low.
Any comments?.
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CONTAMINATED RUNWAY : A runway is considered to be contaminated when more than 25% of the runway surface area (whether in isolated areas or not) within the required length and width being used is covered by the following:
1. Surface water more than 3 mm (0.125 inches) deep, or by slush, or loose snow, equivalent to more than 3 mm of water.
2. Snow which has been compressed into solid mass which resists further compression and will hold together or break into lumps if picked (compacted snow), or
3. Ice, including wet ice.
DRY RUNWAY : A dry runway is one which is neither wet nor contaminated, and includes those paved runways which have been specially prepared with grooves or porous pavement and maintained to retain “effectively dry” breaking action even when moisture is present.
WET RUNWAY : A runway is considered wet when the runway surface is covered with water, or equivalent, less than specified as in contaminated runway above or when there is sufficient moisture on the runway surface to cause it to appear reflective, but without significant areas of standing water
*According to JAR-OPS 1
My note: Never flex in case of Contaminated Runway
My question...
Do you continue considering to use wet V1 if you don´t flex?
BR.
1. Surface water more than 3 mm (0.125 inches) deep, or by slush, or loose snow, equivalent to more than 3 mm of water.
2. Snow which has been compressed into solid mass which resists further compression and will hold together or break into lumps if picked (compacted snow), or
3. Ice, including wet ice.
DRY RUNWAY : A dry runway is one which is neither wet nor contaminated, and includes those paved runways which have been specially prepared with grooves or porous pavement and maintained to retain “effectively dry” breaking action even when moisture is present.
WET RUNWAY : A runway is considered wet when the runway surface is covered with water, or equivalent, less than specified as in contaminated runway above or when there is sufficient moisture on the runway surface to cause it to appear reflective, but without significant areas of standing water
*According to JAR-OPS 1
My note: Never flex in case of Contaminated Runway
My question...Do you continue considering to use wet V1 if you don´t flex?
BR.
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Old Smokey
Great thread Smokey,many thanks, a subject to my heart and makes Prune well worth the money! Very interesting and informative responses from guys, especially my mate Mutt.
Just a quick question if I may, can you please confirm that in the wet/contaminated accelerate-stop case, the FAA figures are predicated on the use of reverse thrust, whilst in the JAA rules use of reverse thrust is not taken into consideration???
Why the difference, or is it just another one of those regulatory anomalies
Can you correct my thinking, or am I just plain wrong on this?
Best regards.
JO.
Just a quick question if I may, can you please confirm that in the wet/contaminated accelerate-stop case, the FAA figures are predicated on the use of reverse thrust, whilst in the JAA rules use of reverse thrust is not taken into consideration???
Why the difference, or is it just another one of those regulatory anomalies
Can you correct my thinking, or am I just plain wrong on this?
Best regards.
JO.
But there is a difference between legal responsibilities and moral responsibilities.
Mutt
Mutt
Old Smokey's thread really gets to the heart and soul of these matters
Some info sources:-
Flight operation aviation library on SmartCockpit
Aerodynamics & Performance – ‘Understanding Range of V1’
Aerodynamics & Performance – ‘Wet Runway (Physics - Certfication & Application)’
Takeoff / Landing on Wet, Contaminated, and Slippery Runways
Flight operation aviation library on SmartCockpit
Aerodynamics & Performance – ‘Understanding Range of V1’
Aerodynamics & Performance – ‘Wet Runway (Physics - Certfication & Application)’
Takeoff / Landing on Wet, Contaminated, and Slippery Runways
Join Date: Mar 2001
Location: I wouldn't know.
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My note: Never flex in case of Contaminated Runway