Smallest type/V1?
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Smallest type/V1?
Hi all, could someone please tell me, what is the type used where V1 isn't an issue. Obviously on small airliners, such as 737s and A319s, V1 is an issue, but there's smaller types out there than these, so I wonder how much smaller must they be before V1 is irrelevant? Thanx.
Pt 2...
Is it necessary to calculate V1 (for a 737-300, say) on a r/w that has enough space to reject T/O and stop, and then some? ie, the stopping distance being something like twice the desired amount.
Pt 2...
Is it necessary to calculate V1 (for a 737-300, say) on a r/w that has enough space to reject T/O and stop, and then some? ie, the stopping distance being something like twice the desired amount.
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V1 is a decision speed at which an engine failure is assumed to be recognized and the rejected takeoff initiated with a reaction time of about 1 second.
A V1 should be established for all aircrafts with more than 1 engine, and be used in all takeoffs.
You can't have a V1 that is lover than minimum controlspeed on ground. You wouldn't be able to control the aircraft in a continued takeoff senario from a speed of V1 speed up to controlspeed ground.
A V1 should be established for all aircrafts with more than 1 engine, and be used in all takeoffs.
You can't have a V1 that is lover than minimum controlspeed on ground. You wouldn't be able to control the aircraft in a continued takeoff senario from a speed of V1 speed up to controlspeed ground.
V1 criteria doesn't apply to all multi-engine a/c.
V1 is a speed below which, after an engine failure & assuming a defined recognition period, the a/c can be brought to a stop on the remaining runway & stopway.
Above V1 the a/c must be able to continue the take off using the remaining runway + clearway.
Multi-engine aircraft below 5700kg/12,500lb MTOW usually aren't certified to operate using V1 criteria. They're really just single engine a/c with the engine split into two or three pieces.
V1 is a speed below which, after an engine failure & assuming a defined recognition period, the a/c can be brought to a stop on the remaining runway & stopway.
Above V1 the a/c must be able to continue the take off using the remaining runway + clearway.
Multi-engine aircraft below 5700kg/12,500lb MTOW usually aren't certified to operate using V1 criteria. They're really just single engine a/c with the engine split into two or three pieces.
Moderator
Dragon Knight,
While the precise V1 definition has changed a few times over the years, the current philosophy is along the lines that "if you haven't STARTED stopping by V1 .. then you are going to continue the takeoff".
This addresses the very real risk of overrun on ASD limited runways.
In the case of a very long runway .. obviously the ASD problem is not a major concern but we stick to the SOP approach to things for consistency.
While the precise V1 definition has changed a few times over the years, the current philosophy is along the lines that "if you haven't STARTED stopping by V1 .. then you are going to continue the takeoff".
This addresses the very real risk of overrun on ASD limited runways.
In the case of a very long runway .. obviously the ASD problem is not a major concern but we stick to the SOP approach to things for consistency.
JT,
You are right about current definitions, but I disagree re the philosophy of V1.
V1 is more the "Go" speed than the "Stop" speed. There must be AT LEAST enough runway to stop if a reject is initiated by V1, but, regardless of how much extra runway is available, the philosophy is that if the aircraft has sufficient speed to reach Vr and climb at V2, that is statistically a safer maneuver than stopping on ANY length of runway.
Over-run is not the only risk in a reject, particularly an asymmetric one. Loss of control and resultant excursion off the side of the runway is a much more dangerous scenario. Thus, if it will fly, get it up and sort it out in the air.
Re smaller aircraft, I think the relevant standard is whatever the current version of FAR 23 is. Aircraft not reaching this standard do not require a V1 calculation (and that includes ALL light piston twins). Engine failure/decition is left largely up to the operator. There is a point after take-off and before "Blue Line" (VySE) where the aircraft will neither accellerate nor climb, and a landing straight ahead is the only option. Aircraft complying with the standard (and I think virtualy all turbines do) MUST have a V1?@and be able to continue a takeoff after engine loss just before.
You are right about current definitions, but I disagree re the philosophy of V1.
V1 is more the "Go" speed than the "Stop" speed. There must be AT LEAST enough runway to stop if a reject is initiated by V1, but, regardless of how much extra runway is available, the philosophy is that if the aircraft has sufficient speed to reach Vr and climb at V2, that is statistically a safer maneuver than stopping on ANY length of runway.
Over-run is not the only risk in a reject, particularly an asymmetric one. Loss of control and resultant excursion off the side of the runway is a much more dangerous scenario. Thus, if it will fly, get it up and sort it out in the air.
Re smaller aircraft, I think the relevant standard is whatever the current version of FAR 23 is. Aircraft not reaching this standard do not require a V1 calculation (and that includes ALL light piston twins). Engine failure/decition is left largely up to the operator. There is a point after take-off and before "Blue Line" (VySE) where the aircraft will neither accellerate nor climb, and a landing straight ahead is the only option. Aircraft complying with the standard (and I think virtualy all turbines do) MUST have a V1?@and be able to continue a takeoff after engine loss just before.
Moderator
Wiz,
We are in heated agreement .... perhaps my words were not well-chosen ... ?
The SOP line ops emphasis is on "go" once the aeroplane gets somewhere near V1 (considering a garden variety engine failure or fire type of situation) .. what I was trying to highlight is the Boeing/Airbus philosophy that V1 is not a "decision" speed .... rather a "my decision has already been made and if I haven't commenced the stop sequence by the time I get to V1 then I am going to keep going" speed .. in effect, this biases the decision several knots or so slower and provides a significant buffer for ASD.
So far as bugsmashers are concerned it is important to note that FAR23 has gone through some very significant changes over recent years and that the great majority of in-service lighties were certificated to standards (many to CAR3 which pre-dated FAR23) that are quite different in many aspects to what one might read in the current FAR23 words. Fortunately the FAA website does give one the choice of checking out superseded FARs if one is interested in a particular certification basis. Type Certificate Data Sheets for particular Types and models can be found here and the certification basis for most is specified toward the end of entry for the relevant models.
We are in heated agreement .... perhaps my words were not well-chosen ... ?
The SOP line ops emphasis is on "go" once the aeroplane gets somewhere near V1 (considering a garden variety engine failure or fire type of situation) .. what I was trying to highlight is the Boeing/Airbus philosophy that V1 is not a "decision" speed .... rather a "my decision has already been made and if I haven't commenced the stop sequence by the time I get to V1 then I am going to keep going" speed .. in effect, this biases the decision several knots or so slower and provides a significant buffer for ASD.
So far as bugsmashers are concerned it is important to note that FAR23 has gone through some very significant changes over recent years and that the great majority of in-service lighties were certificated to standards (many to CAR3 which pre-dated FAR23) that are quite different in many aspects to what one might read in the current FAR23 words. Fortunately the FAA website does give one the choice of checking out superseded FARs if one is interested in a particular certification basis. Type Certificate Data Sheets for particular Types and models can be found here and the certification basis for most is specified toward the end of entry for the relevant models.
Guest
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Sorry, but I was only trying to explain the basis of V1, and not the application of V1.
That is an entirely different matter, and I have to agree with john_t. Stopping close to V1 can be very hairy bussiness.
Reaching V1 minus 5 kts, my hands will no longer be at the throttles, unless I haven't reached Vmcg, I'm in go mode. I know I'm eating of my minimum 35 ft. at the runway end, in a balanced takeoff, but I can still expect to be airborne on the remaining runway. Actually with V1 minus 10 kts., I can still expect to be airborne at the runway end.
You are correct john, converting some of your GO margin to your STOP margin is sound practice.
That is an entirely different matter, and I have to agree with john_t. Stopping close to V1 can be very hairy bussiness.
Reaching V1 minus 5 kts, my hands will no longer be at the throttles, unless I haven't reached Vmcg, I'm in go mode. I know I'm eating of my minimum 35 ft. at the runway end, in a balanced takeoff, but I can still expect to be airborne on the remaining runway. Actually with V1 minus 10 kts., I can still expect to be airborne at the runway end.
You are correct john, converting some of your GO margin to your STOP margin is sound practice.
