greater v1 or lower v1
Bubbers, I'm just addressing the specific question in this thread. Whether it is allowed by the rules or the flight manual is immaterial as it seemed to be a purely theoretical question.
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I'm amazed at how difficult many of you are making this. The question is purely about using a high V1 speed when a range of V1 speeds are available and can be used (i.e., the takeoff is not field length limited and multiple V1 speed data are available in the AFM). It says nothing about changing V2, using improved climb, or overspeeds.
Aerocat is spot on. Using a higher V1 results in a shorter accelerate-go (i.e., takeoff) distance, which will also increase your vertical clearance over obstacles. You get that increased vertical clearance because you got into the air in a shorter distance; there isn't any effect on your climb gradient.
Aerocat is spot on. Using a higher V1 results in a shorter accelerate-go (i.e., takeoff) distance, which will also increase your vertical clearance over obstacles. You get that increased vertical clearance because you got into the air in a shorter distance; there isn't any effect on your climb gradient.
Last edited by donstim; 18th Feb 2012 at 19:11.
Originally Posted by bubbers44
All I know is I would be in deep trouble if I aborted after V1 at my company, a major US airline. Maybe Australia has different rules but we can't do that.
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I don't think that the original question is about variable v2 also. At least that is not indicated in the question.
I remember that on the A320 there was something called a "variable kvs factor" and had to do with shifting v2 by pretendig to need a higher stall margine to increase v2 and therefore being able to pull out more weight in case of engine failure. That was the reason why even on very long RWYs we got rather small stopping margines. One would expect around 1500m+ on a 4000m RWY on a twin like the 320 but it was way less.
I doubt that this is the examn's question. On our EFB, the takeoff data calculation does show a v1 range, but always, alyways only one vr and one v2. Wether that v2 is "kvs factored", is not important, as there is no range to choose from.
So i beleive, aerocat and I agree, and do give the correct answer.
But who knows, thinking back on my examn, and how many wrong answers were the ones you had to check to get the points...
Nic
I remember that on the A320 there was something called a "variable kvs factor" and had to do with shifting v2 by pretendig to need a higher stall margine to increase v2 and therefore being able to pull out more weight in case of engine failure. That was the reason why even on very long RWYs we got rather small stopping margines. One would expect around 1500m+ on a 4000m RWY on a twin like the 320 but it was way less.
I doubt that this is the examn's question. On our EFB, the takeoff data calculation does show a v1 range, but always, alyways only one vr and one v2. Wether that v2 is "kvs factored", is not important, as there is no range to choose from.
So i beleive, aerocat and I agree, and do give the correct answer.
But who knows, thinking back on my examn, and how many wrong answers were the ones you had to check to get the points...
Nic
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Take-Off Speeds for the 737-300/400/500
TOW 737-300 20K 737-400 23.5K 737-500 18.5K
1000kg V1 VR V2 V1 VR V2 V1 VR V2
70 158 162 168
65 154 155 160 152 154 162
60 147 148 154 144 147 155 147 147 152
55 140 141 148 137 139 149 140 140 146
50 133 133 141 129 131 143 132 132 139
45 123 123 133 121 123 136 123 123 132
40 114 114 126 112 115 130 113 114 124
35 104 104 117 104 104 117
ISA Vmcg=111 ISA Vmcg=115 ISA Vmcg=106
Typical wet V1= dry V1-10kts.
All speeds assume balanced field, flap 5, pa<5000ft, OAT<35C, nil slope, nil wind, runway dry.
Looks like increasing V1 and leaving Vr and V2 alone doesn't change anything enough to be readable or none on a 737.
TOW 737-300 20K 737-400 23.5K 737-500 18.5K
1000kg V1 VR V2 V1 VR V2 V1 VR V2
70 158 162 168
65 154 155 160 152 154 162
60 147 148 154 144 147 155 147 147 152
55 140 141 148 137 139 149 140 140 146
50 133 133 141 129 131 143 132 132 139
45 123 123 133 121 123 136 123 123 132
40 114 114 126 112 115 130 113 114 124
35 104 104 117 104 104 117
ISA Vmcg=111 ISA Vmcg=115 ISA Vmcg=106
Typical wet V1= dry V1-10kts.
All speeds assume balanced field, flap 5, pa<5000ft, OAT<35C, nil slope, nil wind, runway dry.
Looks like increasing V1 and leaving Vr and V2 alone doesn't change anything enough to be readable or none on a 737.
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Sorry, but that ain't it. That info only provides a single, balanced field V1 value for each weight. You cannot use that info to select an unbalanced field V1 value, which is what you are doing when selecting from a range of possible V1 values.
You need to get that info from the AFM, not from a basic ops speeds card.
You need to get that info from the AFM, not from a basic ops speeds card.
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Since in my long career through several airlines I have never heard of variable V1 speeds except for improved climb which changes all the speeds where do you find this information. Also by adding an average of 1 knot to V1 and leaving the other V speeds the same what does that accomplish? It seems we are wasting a lot of bandwith here.
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Most likely, the performance engineers at your companies has heard of this for your aircraft. But, in the name of simplicity, for all the pilots on the line at your company, for a given set of conditions, the same V1 speed is always used.
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Since in my long career through several airlines I have never heard of variable V1 speeds except for improved climb which changes all the speeds where do you find this information. Also by adding an average of 1 knot to V1 and leaving the other V speeds the same what does that accomplish? It seems we are wasting a lot of bandwith here.
The software used to produce the IRTs will have a setting along the lines of:
Where a range of V1s is available choose: Highest, Lowest, Balanced or fixed V1/V2 ratio.
The end user on the line doesn't normally see the choices but the type of V1 chosen should in my view be printed on the IRT for information.
The examiner talks about the engine failure case which is the reason why V1 was designed anyway. Fairly obvious A is correct I would say.
The question is clearly with a fixed V2. V2 and V1 have regulatory no direct link as far as I know (and I presume this is a question for an official exam). V2 is limited by rotation speed, minimum control speed (air) and stall speed. If a company uses fixed V1/V2 relationships than that is their choice as long as it makes sure the minimum climb requirements, etc, are fullfilled.
Improved climb uses available excess field to increase Vr, hence V2, and hence creating better climb gradients. Different story that has initially nothing to do with V1 changes (although V1 is likely to change because Vr and V2 change). The note about the field limit might be confusing, but it's only there to show V1 can be increased, field length is not limiting your stopping distance because of a higher V1.
The question is clearly with a fixed V2. V2 and V1 have regulatory no direct link as far as I know (and I presume this is a question for an official exam). V2 is limited by rotation speed, minimum control speed (air) and stall speed. If a company uses fixed V1/V2 relationships than that is their choice as long as it makes sure the minimum climb requirements, etc, are fullfilled.
Improved climb uses available excess field to increase Vr, hence V2, and hence creating better climb gradients. Different story that has initially nothing to do with V1 changes (although V1 is likely to change because Vr and V2 change). The note about the field limit might be confusing, but it's only there to show V1 can be increased, field length is not limiting your stopping distance because of a higher V1.
