john_tullamarine
25th Apr 2006, 12:07
Thread started to separate a discussion on reduced V1 into dry and contaminated runway cases ... the following several posts/part posts have been copied from the other thread so that discussion on contaminated V1 can continue without distracting the other dry V1 discussion ... me, I'm always a bit worried in contaminated conditions ... reduce the V1 and the acceleration to VR becomes a potential what-if for the real world continued case .. run high with V1 and we are balancing increased contaminant drag (good) with reduced coefficients (not so good) for the real world reject ... sometimes I wish I had taken up that offer to be a bank clerk when I was 15 ..
If we can use this thread for contaminated discussions, please, and the other for dry runway considerations ..
Jambo Buana ...
Flying with an American Airlines Direct entry Captain a few weeks ago. He mentioned that they by way of SOP, AA always reduced V1 to its minimum value.
Given that 2/3 of runway overrun incidents were unnecessarily rejected in the first place is this a good policy and how many of the EU operators out there follow this policy?
Thanks
BOAC ...
Not one of the three UK airlines I have worked for do, and this is the CAA's advice on it. "Some margins are provided in the continued take-off performance in the event of a decision to continue the take-off with an engine failure below V1 but these could be eroded to such an extent that the aeroplane may not be able to lift off by the end of the runway and/or to clear obstacles once airborne. This is particularly so when using a 'wet' V1. 'Wet' V1 accounts for the reduced stopping capability on a wet runway, but it also reduces the margins in the continued take-off performance compared to the dry runway situation."
I would suggest that you would have to have full performance factors for the runway/obstacles to start messing with V1 for no particular reason. If the runway is so long that V1 can safely be reduced and still enable a 'go' then stopping at V1 is equally not a problem? There are places like JER27 and FNC where it might be a good idea.
TomConrad ...
My old company in the U.S., after a 737-400 accident at LaGuardia, adopted Boeing's suggestion that V1 could be 'reduced' as conditons permit...as conditions warrant. This does not necessarily mean that the 'MIN V1' is VMGC +1 or whatever. But, it's a perfomance issue that considers takeoff flap settings, density altitude, derated engines (or not), close-in obstacle conditions (first segment climb requirements), runway length, runway conditions, etc., etc.
Boeing (and Airbus, I'm sure) has charts and graphs for just about any combination of conditions and situations. What my old company did was absolutely in accordance with the AFM...totally Boeing approved (and Boeing suggested)...totally FAA approved...and, when applied prudently, added to the safety margin for takeoffs.
Additionally, the 'final numbers' that were computer generated gave a normal V1, and a minimum V1. (Again, Min V1 was not necessarily VMGC limited...and in most cases it was well above VMGC.) It was the captain's decision. He/she could use the normal V1, the minimum V1 or any number in between.
The restrictions were: (1) Whatever V1 was chosen, it was a for real V1...once decided, it was carved in stone, (2) It had to be briefed what this V1 speed was...and, as well, what Vr was...and, as well, not to rotate prior to Vr (but to rotate at Vr).
Again, the computer-generated speeds were all AFM, Boeing, FAA, and company approved. And, it worked very nicely. Coming out of La Guardia on a snowy day reduced the pucker factor just a bit, knowing that with the reduced V1, you at least had some chance of stopping (assuming you rejected properly, etc.) prior to the end of the runway.
O\Zone...
Probably 90% of Airbus (fly-by-wire) operators using standard RTOW charts use V1 min.
Indeed, its a requirement in FCOM II, that if you are to use the corrections for wet or contaminated runways, your RTOW chart must be based on V1 min.
Mutt...
As an FAA certified operator of 17 different versions of Boeing airliners certified under FAR25, I have NEVER seen contaminated runway correction data in any FAA Approved Airplane Flight Manual. I'm therefore surprised that they granted approval to 1 specific airline.
We base our contaminated runway information on FAA AC91-6B and the data provided in the Operations Manual.
TomConrad ...
But, I can tell you, definitively, that the reduced V1 is the SOP of my old carrier. And, with wet or contamiated runways, the figure routinely came across with the weight and balance figures from the ACARS uplink.
It was very nice to have. For example, you're doing a runway 01 takeoff in DCA...it's been snowing...runway is in good shape, though (relatively)...and the numbers come up on the ACARS.
Min V1 V1 Vr V2
128 141 143 148
(I'm just making these numbers up...)
But, the captain has the authority to choose his V1 anywhere between 128 and 141 (inclusive). Again, the only restriction in the SOP stated that, once the V1 is chosen, it is to be flown.
So, if, in the above example, the guys decide that 135 would be a prudent figure for V1, and an engine fails at 136, a "GO" is absolutely mandatory.
The other caveat as explicitly stated in the manual is that the V1 - Vr spread is emphasized. (Yes, my old carrier had another accident in LaGuardia, partially because the captain rotated early, rotated aggessively, with contaminated wings. There was a sizable spread between V1 and Vr.) So, this spread, under their SOP, must be briefed.
Incidently, a related SOP, the V1 call by the PM (Pilot Monitoring a.k.a. PNF :> :> :>), is made 5 knots prior to V1. So, in the above example, even if the guys were to choose the absolute minimum V1 of 128, the V1 call during the takeoff roll would occur at 123. Of course, once the call is made...you 'go'.
I can tell you, most definitely, that Boeing professes these procedures. They explicitly stated all of this at a special safety symposium they held for my old company...after the series of accidents. (I was there, took notes, and remember all of this....despite my failing memory. :> :>:>) Present in the hotel ballroom was FAA, both from the Air Carrier District Office, and from Washington. Six months after this meeting, the above-stated procedures became the airline's SOP.
Another interesting bit I got out of this meeting is the fact that Boeing has a bazillion graphs/charts, etc. with regard to aircraft performance. They're all "FAA Approved". What we, as pilots see in our manuals, is just a small sample of what Boeing has...really not much more than the minimum what the FAA requires.
For example, before this seminar, I never knew that Flaps 25 was 'an approved' takeoff flap setting on the 737. I've never seen numbers for a Flaps 25 takeoff...I've never heard of anyone using Flaps 25 for takeoff...but, the numbers exist, the performance (under certain contitions) meets FAA requirements, and it's FAA approved. The point, there are a lot of things regarding aircraft certification/performance, etc., that we, as pilots, never heard of (and may think are weird as heck)...but they're there, they're FAA approved, and they can be used (as part of the airline's SOP, of course).
Mutt...
Just to focus on contaminated runways for a while. This is one of my little points of contention where I feel that the FAA should provide certification and operational regulations for operations from contaminated runways.
You won’t find an AFM page with contaminated runway definitions nor performance data, it just doesn’t exist. In the same way the wonderful electronic Flight Manual for the B777 won’t produce contaminated runway data as it just isn’t required under FAR25.
JAA regulations require operators to account for runway contaminants, JAR operators are therefore provided with contaminated runway data in the Flight Manuals. The best that the FAA has come up with is a 20 year old Advisory Circular based on a NASA test program using a Convair 880. AC91-6A is used as the basis for the data that Boeing provides in the Operations Manual and their non-certified computer programs.
So you are left in the quandary,
- There are NO Federal Aviation Regulations pertaining to contaminated runway operations.
- The FAA provides definitions and performance data in the form of Advisory Circular 91-6B.
- The manufacturer hasn’t flight tested the aircraft on contaminated runways
- The manufacturer offers “advisory” data.
- Your airline accepts it as SOP.
If we can use this thread for contaminated discussions, please, and the other for dry runway considerations ..
Jambo Buana ...
Flying with an American Airlines Direct entry Captain a few weeks ago. He mentioned that they by way of SOP, AA always reduced V1 to its minimum value.
Given that 2/3 of runway overrun incidents were unnecessarily rejected in the first place is this a good policy and how many of the EU operators out there follow this policy?
Thanks
BOAC ...
Not one of the three UK airlines I have worked for do, and this is the CAA's advice on it. "Some margins are provided in the continued take-off performance in the event of a decision to continue the take-off with an engine failure below V1 but these could be eroded to such an extent that the aeroplane may not be able to lift off by the end of the runway and/or to clear obstacles once airborne. This is particularly so when using a 'wet' V1. 'Wet' V1 accounts for the reduced stopping capability on a wet runway, but it also reduces the margins in the continued take-off performance compared to the dry runway situation."
I would suggest that you would have to have full performance factors for the runway/obstacles to start messing with V1 for no particular reason. If the runway is so long that V1 can safely be reduced and still enable a 'go' then stopping at V1 is equally not a problem? There are places like JER27 and FNC where it might be a good idea.
TomConrad ...
My old company in the U.S., after a 737-400 accident at LaGuardia, adopted Boeing's suggestion that V1 could be 'reduced' as conditons permit...as conditions warrant. This does not necessarily mean that the 'MIN V1' is VMGC +1 or whatever. But, it's a perfomance issue that considers takeoff flap settings, density altitude, derated engines (or not), close-in obstacle conditions (first segment climb requirements), runway length, runway conditions, etc., etc.
Boeing (and Airbus, I'm sure) has charts and graphs for just about any combination of conditions and situations. What my old company did was absolutely in accordance with the AFM...totally Boeing approved (and Boeing suggested)...totally FAA approved...and, when applied prudently, added to the safety margin for takeoffs.
Additionally, the 'final numbers' that were computer generated gave a normal V1, and a minimum V1. (Again, Min V1 was not necessarily VMGC limited...and in most cases it was well above VMGC.) It was the captain's decision. He/she could use the normal V1, the minimum V1 or any number in between.
The restrictions were: (1) Whatever V1 was chosen, it was a for real V1...once decided, it was carved in stone, (2) It had to be briefed what this V1 speed was...and, as well, what Vr was...and, as well, not to rotate prior to Vr (but to rotate at Vr).
Again, the computer-generated speeds were all AFM, Boeing, FAA, and company approved. And, it worked very nicely. Coming out of La Guardia on a snowy day reduced the pucker factor just a bit, knowing that with the reduced V1, you at least had some chance of stopping (assuming you rejected properly, etc.) prior to the end of the runway.
O\Zone...
Probably 90% of Airbus (fly-by-wire) operators using standard RTOW charts use V1 min.
Indeed, its a requirement in FCOM II, that if you are to use the corrections for wet or contaminated runways, your RTOW chart must be based on V1 min.
Mutt...
As an FAA certified operator of 17 different versions of Boeing airliners certified under FAR25, I have NEVER seen contaminated runway correction data in any FAA Approved Airplane Flight Manual. I'm therefore surprised that they granted approval to 1 specific airline.
We base our contaminated runway information on FAA AC91-6B and the data provided in the Operations Manual.
TomConrad ...
But, I can tell you, definitively, that the reduced V1 is the SOP of my old carrier. And, with wet or contamiated runways, the figure routinely came across with the weight and balance figures from the ACARS uplink.
It was very nice to have. For example, you're doing a runway 01 takeoff in DCA...it's been snowing...runway is in good shape, though (relatively)...and the numbers come up on the ACARS.
Min V1 V1 Vr V2
128 141 143 148
(I'm just making these numbers up...)
But, the captain has the authority to choose his V1 anywhere between 128 and 141 (inclusive). Again, the only restriction in the SOP stated that, once the V1 is chosen, it is to be flown.
So, if, in the above example, the guys decide that 135 would be a prudent figure for V1, and an engine fails at 136, a "GO" is absolutely mandatory.
The other caveat as explicitly stated in the manual is that the V1 - Vr spread is emphasized. (Yes, my old carrier had another accident in LaGuardia, partially because the captain rotated early, rotated aggessively, with contaminated wings. There was a sizable spread between V1 and Vr.) So, this spread, under their SOP, must be briefed.
Incidently, a related SOP, the V1 call by the PM (Pilot Monitoring a.k.a. PNF :> :> :>), is made 5 knots prior to V1. So, in the above example, even if the guys were to choose the absolute minimum V1 of 128, the V1 call during the takeoff roll would occur at 123. Of course, once the call is made...you 'go'.
I can tell you, most definitely, that Boeing professes these procedures. They explicitly stated all of this at a special safety symposium they held for my old company...after the series of accidents. (I was there, took notes, and remember all of this....despite my failing memory. :> :>:>) Present in the hotel ballroom was FAA, both from the Air Carrier District Office, and from Washington. Six months after this meeting, the above-stated procedures became the airline's SOP.
Another interesting bit I got out of this meeting is the fact that Boeing has a bazillion graphs/charts, etc. with regard to aircraft performance. They're all "FAA Approved". What we, as pilots see in our manuals, is just a small sample of what Boeing has...really not much more than the minimum what the FAA requires.
For example, before this seminar, I never knew that Flaps 25 was 'an approved' takeoff flap setting on the 737. I've never seen numbers for a Flaps 25 takeoff...I've never heard of anyone using Flaps 25 for takeoff...but, the numbers exist, the performance (under certain contitions) meets FAA requirements, and it's FAA approved. The point, there are a lot of things regarding aircraft certification/performance, etc., that we, as pilots, never heard of (and may think are weird as heck)...but they're there, they're FAA approved, and they can be used (as part of the airline's SOP, of course).
Mutt...
Just to focus on contaminated runways for a while. This is one of my little points of contention where I feel that the FAA should provide certification and operational regulations for operations from contaminated runways.
You won’t find an AFM page with contaminated runway definitions nor performance data, it just doesn’t exist. In the same way the wonderful electronic Flight Manual for the B777 won’t produce contaminated runway data as it just isn’t required under FAR25.
JAA regulations require operators to account for runway contaminants, JAR operators are therefore provided with contaminated runway data in the Flight Manuals. The best that the FAA has come up with is a 20 year old Advisory Circular based on a NASA test program using a Convair 880. AC91-6A is used as the basis for the data that Boeing provides in the Operations Manual and their non-certified computer programs.
So you are left in the quandary,
- There are NO Federal Aviation Regulations pertaining to contaminated runway operations.
- The FAA provides definitions and performance data in the form of Advisory Circular 91-6B.
- The manufacturer hasn’t flight tested the aircraft on contaminated runways
- The manufacturer offers “advisory” data.
- Your airline accepts it as SOP.