Lowest take off V1
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Lowest take off V1
Dies anyone know if there is aformula for calculating a reduced V1, assuming airfield details (TODA, TORA & ASDA etc) and Vr and V2 are known
Given that V1min is a function of Vmcg, to get a lower minimum V1, you need to lower Vmcg.
Most of the factors affecting Vmcg are not able to be varied, but one that is, is engine thrust.
So it is possible for some performance software to come up with a reduced V1 when performing a reduced thrust takeoff, but the use of this is subject to a number of restrictions, and that is before you consider a plethora of other takeoff performance requirements that need to be met.
Most of the factors affecting Vmcg are not able to be varied, but one that is, is engine thrust.
So it is possible for some performance software to come up with a reduced V1 when performing a reduced thrust takeoff, but the use of this is subject to a number of restrictions, and that is before you consider a plethora of other takeoff performance requirements that need to be met.
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Reduced V1 takeoff
Firstly, thank you all for taking the time to reply. In answer to B2N2. I am looking at a situation where a BAe146 fire fighting aircraft is taking off heavily loaded with 3000 gallons of retardant on a runway where it would possibly be more prudent to get airborne following an engine failure than to try to stop. ITo enable this it would be nice to be able to reduce V1 to as close to vmcg whilst still having enough room to get airborne. It is possible there may be software that can give me the information and it would be nice to know if there is and the cost. For a small operator it may be better if there was a formula that could be used to work it out.
As you alluded to, the low V1 won’t be the issue. However, the distance available for 3 engine acceleration from V1 to VR could be limiting on shorter runways.
Firstly, thank you all for taking the time to reply. In answer to B2N2. I am looking at a situation where a BAe146 fire fighting aircraft is taking off heavily loaded with 3000 gallons of retardant on a runway where it would possibly be more prudent to get airborne following an engine failure than to try to stop. ITo enable this it would be nice to be able to reduce V1 to as close to vmcg whilst still having enough room to get airborne. It is possible there may be software that can give me the information and it would be nice to know if there is and the cost. For a small operator it may be better if there was a formula that could be used to work it out.
When I flew light business jets, Our V1 was almost always Vr. But there were plenty of longer runways where I could have "aborted" from a 100' AGL with the gear up, and easily come to a stop on that same runway.
If you are talking about a balanced T/O V1, it is simply the speed where, given the weight&weather the aircraft can come to a stop before the end of the runway, and the aircraft can continue the T/O, with 1 engine not running, and cross the end of the runway at the appropriate height, and continue climbing afterwards....
Lowering the V1 without changing anything else will achieve your desire to be able to come to a stop on the runway, but it will make it impossible to achieve the required height crossing the DER. The only way to achieve a lower V1, and still get airborne after an engine failure is to reduce TOW.
If you just want a bigger margin on the runway, you could calculate the max TOW, reduce it by a margin for safety, and run the numbers for the lowest V1, or maybe just run numbers for a wet runway...
But there will always be a TOW penalty when you change the numbers from the the optimal balanced T/O performance V1.
(and as someone who has never flown the BAE146, from what I little I know about the performance, I still would be surprised if Vmcg was a big factor in V1)
Firstly, thank you all for taking the time to reply. In answer to B2N2. I am looking at a situation where a BAe146 fire fighting aircraft is taking off heavily loaded with 3000 gallons of retardant on a runway where it would possibly be more prudent to get airborne following an engine failure than to try to stop. ITo enable this it would be nice to be able to reduce V1 to as close to vmcg whilst still having enough room to get airborne. It is possible there may be software that can give me the information and it would be nice to know if there is and the cost. For a small operator it may be better if there was a formula that could be used to work it out.
BAe provides operators with very comprehensive flight manuals and an FCOM that is full of performance info and other useful data. Unless you wish to become the first at the scene of an accident I suggest that you stick to the way the manufacturer intended the aircraft to be operated.
Last edited by common toad; 26th May 2024 at 07:03.
I am looking at a situation where a BAe146 fire fighting aircraft is taking off heavily loaded with 3000 gallons of retardant on a runway where it would possibly be more prudent to get airborne following an engine failure than to try to stop. ITo enable this it would be nice to be able to reduce V1 to as close to vmcg whilst still having enough room to get airborne.
The whole point of V1 is that it literally tells you whether you can or can't stop in the remaining distance available. The general assumption is that you don't go flying with a problem unless you absolutely have to, so your scenario makes no sense. You could lower V1 to Vmcg if you wanted to, but then you'd be going flying in circumstances where it would be more prudent to stop.
V1min would favour continuing, and the limitation would be the TODR, which would increase over V1BFL TODR. ASDR would decrease significantly and not be limiting. What I think the OP may find limiting is the heavily laden nature of the flight. If the aim is to maximise TOM, in most airfield V1BFL will result in the highest RTOM. Reducing V1 from V1BFL will significantly increase TODR, so if the runway was limiting it is unlikely to be an available strategy.
Last edited by Journey Man; 26th May 2024 at 14:35.
There appears to be undue bias in the choice of performance; "… possibly be more prudent to get airborne following an engine failure". This thinking should not influence performance calculations.
for info;
"Minimum V1 - the minimum permissible V1 speed for the referenced conditions (temperature, wind, pressure altitude, weight, thrust, runway etc) from which the takeoff can be safely completed after the critical engine has failed at the designated speed (VEF)"
"Note that Engine Failure Speed (VEF) is a manufacturer nominated design speed that must be greater than Minimum Control Speed - Ground (Vmcg) and occur at least one second prior to V1."
https://skybrary.aero/articles/v1
See CS 25 for the full certification requirement.
and don't even think of shaving margins near Vmcg. Performance requirement / testing in this area is a very grey art; no crosswind, dry runway, good surface, specific forward stick position, …
The 146/RJ is a delightful aircraft to fly with great capability, but Vmcg is one corner of envelope with fuzzy margins because of the attributes - 4 engines, big fin / rudder, high lift wing, …
for info;
"Minimum V1 - the minimum permissible V1 speed for the referenced conditions (temperature, wind, pressure altitude, weight, thrust, runway etc) from which the takeoff can be safely completed after the critical engine has failed at the designated speed (VEF)"
"Note that Engine Failure Speed (VEF) is a manufacturer nominated design speed that must be greater than Minimum Control Speed - Ground (Vmcg) and occur at least one second prior to V1."
https://skybrary.aero/articles/v1
See CS 25 for the full certification requirement.
and don't even think of shaving margins near Vmcg. Performance requirement / testing in this area is a very grey art; no crosswind, dry runway, good surface, specific forward stick position, …
The 146/RJ is a delightful aircraft to fly with great capability, but Vmcg is one corner of envelope with fuzzy margins because of the attributes - 4 engines, big fin / rudder, high lift wing, …
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“Roger Munyard” take note of what “safetypee” wrote. He known probably knows more about the 146/RJ flying, testing and training than anyone else above ground today. Anyone that know him respect his wise words re the aircraft.
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The aircraft is a joy to fly and the 3-engine ferry is not difficult IF you follow the correct procedures. Are you by any chance new to the BAe 146? Have you completed the 3-engine ferry training? Trust me, you do not want to be pushing your luck with loosing a second engine at high weight - it will not end well.
BAe provides operators with very comprehensive flight manuals and an FCOM that is full of performance info and other useful data. Unless you wish to become the first at the scene of an accident I suggest that you stick to the way the manufacturer intended the aircraft to be operated.
BAe provides operators with very comprehensive flight manuals and an FCOM that is full of performance info and other useful data. Unless you wish to become the first at the scene of an accident I suggest that you stick to the way the manufacturer intended the aircraft to be operated.
Thanks for your message and yes, I have flown the BAe146 including a 3 engine ferry flight. I have been teaching in the flight simulator (which is now in Missoula) for about 12 years, most of it full time during which I must have trained at least 100 pilots for 3 engine ferry operations.
The situation with the operators that I work with now is that they operate the aircraft as Fire fighting aircraft carrying 3000 gallons of retardant. When taking of at a weight of just over 40,000 kg it could be considered preferable to get airborne rather than risk a high speed take-off rejection. Particularly because, at a press of a button, the load could be jettisoned in 3 seconds reducing the weight to 28,000 kg. By having a lower V1 a high speed abort can be avoided provided there is enough runway left to get airborne and safely achieve V2. The question is how to get the required lowest V1 figure for the existing conditions.
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Some thoughts ...
Does anyone know if there is a formula for calculating a reduced V1, assuming airfield details (TODA, TORA & ASDA etc) and Vr and V2 are known
Not the way we go about it, so, no. You could figure one out but for no real value and a lot of effort.
Given that V1min is a function of Vmcg, to get a lower minimum V1, you need to lower Vmcg.
No, you can't do that. Vmcg is fixed for the certification conditions.
So it is possible for some performance software to come up with a reduced V1 when performing a reduced thrust takeoff
No, for reduced thrust Vmcg is fixed and based on whatever the rated thrust is. You are confusing reduced thrust with derated takeoff. In the later, the certification basis is varied to reflect a different engine rating. Conceptually, you unbolt a bigger engine and bolt in a replacement smaller engine. To make things worse, you can play with both derated and reduced takeoff together but you start with the derate and then play with the reduced thrust.
BAe146 fire fighting aircraft is taking off heavily loaded with 3000 gallons of retardant on a runway where it would possibly be more prudent to get airborne following an engine failure than to try to stop. To enable this it would be nice to be able to reduce V1 to as close to vmcg whilst still having enough room to get airborne. It is possible there may be software that can give me the information and it would be nice to know if there is and the cost. For a small operator it may be better if there was a formula that could be used to work it out.
Be very aware that a takeoff failure very close to Vmcg is not for the faint-hearted and is guaranteed to get the pulse rate up and away. The story for a given aeroplane is told quite nicely in the AFM. If the present story doesn't suit your needs, you need a smaller engine. Then, again a smaller engine on the quadrapuff probably is a bit of a non-sequiter.
the low V1 won’t be the issue. However, the distance available for 3 engine acceleration from V1 to VR could be limiting on shorter runways.
All depends on the numbers. On some shorter runways, being able to reduce V1 can make the difference if ASDR were previously limiting .....
If you are talking about a balanced T/O V1, it is simply the speed
Although I very nearly did my initial command on the machine, I have never played with the AFM. I presume that the AFM permits unbalancing which would be a necessary consideration to exploit the OP's concerns.
You could lower V1 to Vmcg if you wanted to, but then you'd be going flying in circumstances where it would be more prudent to stop.
While your opinion is respected, I think it, somewhat parochially, throws out the baby with the bathwater.
V1min would favour continuing
Would you put a wager on that ? While acknowledging the OP's jettison observations, there comes into play a consideration of the jettison reliability in extremis.
safety pee
.. as always, wise counsel.
Does anyone know if there is a formula for calculating a reduced V1, assuming airfield details (TODA, TORA & ASDA etc) and Vr and V2 are known
Not the way we go about it, so, no. You could figure one out but for no real value and a lot of effort.
Given that V1min is a function of Vmcg, to get a lower minimum V1, you need to lower Vmcg.
No, you can't do that. Vmcg is fixed for the certification conditions.
So it is possible for some performance software to come up with a reduced V1 when performing a reduced thrust takeoff
No, for reduced thrust Vmcg is fixed and based on whatever the rated thrust is. You are confusing reduced thrust with derated takeoff. In the later, the certification basis is varied to reflect a different engine rating. Conceptually, you unbolt a bigger engine and bolt in a replacement smaller engine. To make things worse, you can play with both derated and reduced takeoff together but you start with the derate and then play with the reduced thrust.
BAe146 fire fighting aircraft is taking off heavily loaded with 3000 gallons of retardant on a runway where it would possibly be more prudent to get airborne following an engine failure than to try to stop. To enable this it would be nice to be able to reduce V1 to as close to vmcg whilst still having enough room to get airborne. It is possible there may be software that can give me the information and it would be nice to know if there is and the cost. For a small operator it may be better if there was a formula that could be used to work it out.
Be very aware that a takeoff failure very close to Vmcg is not for the faint-hearted and is guaranteed to get the pulse rate up and away. The story for a given aeroplane is told quite nicely in the AFM. If the present story doesn't suit your needs, you need a smaller engine. Then, again a smaller engine on the quadrapuff probably is a bit of a non-sequiter.
the low V1 won’t be the issue. However, the distance available for 3 engine acceleration from V1 to VR could be limiting on shorter runways.
All depends on the numbers. On some shorter runways, being able to reduce V1 can make the difference if ASDR were previously limiting .....
If you are talking about a balanced T/O V1, it is simply the speed
Although I very nearly did my initial command on the machine, I have never played with the AFM. I presume that the AFM permits unbalancing which would be a necessary consideration to exploit the OP's concerns.
You could lower V1 to Vmcg if you wanted to, but then you'd be going flying in circumstances where it would be more prudent to stop.
While your opinion is respected, I think it, somewhat parochially, throws out the baby with the bathwater.
V1min would favour continuing
Would you put a wager on that ? While acknowledging the OP's jettison observations, there comes into play a consideration of the jettison reliability in extremis.
safety pee
.. as always, wise counsel.
it could be considered preferable to get airborne rather than risk a high speed take-off rejection
Seriously? You are suggesting that fully trained and type rated pilot might find doing an RTO from V1 a problem? In all the years that I operated to and from LCY I never considered that my external anal sphincter ever ‘puckered’ by the prospect.
Jettisoning these 3,000 gallons of fluid in 3-seconds whilst flying the aircraft - how does that affect controlling the aircraft while dealing with an engine failure? Remember, you are talking about those whose same pilots who you think cannot handle an RTO.
I find this discussion more baffling now that we learn that you are a trainer.
Whether that's an option available on the 146 is something I doubt!!!
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Not so sure - Our Boeing FCTM suggests that using a block derate (not assumed temp...) to reduce Vmcg in contaminated runway conditions may raise the perf limited take off weight. This is probably within the 'certification conditions' that you note which gives the crews an option.
Perhaps you might re-read my post. I thought I had distinguished between flex and derate ? Your manual note looks to be pretty well what I was talking about ?
All's well, though, the value of these sorts of threads is to get people thinking and challenging their ideas so that, at the end of the day we all might move forward a little with our various knowledge bases.
Perhaps you might re-read my post. I thought I had distinguished between flex and derate ? Your manual note looks to be pretty well what I was talking about ?
All's well, though, the value of these sorts of threads is to get people thinking and challenging their ideas so that, at the end of the day we all might move forward a little with our various knowledge bases.
Not so sure - Our Boeing FCTM suggests that using a block derate (not assumed temp...) to reduce Vmcg in contaminated runway conditions may raise the perf limited take off weight. This is probably within the 'certification conditions' that you note which gives the crews an option.
Perhaps you might re-read my post. I thought I had distinguished between flex and derate ? Your manual note looks to be pretty well what I was talking about ?
All's well, though, the value of these sorts of threads is to get people thinking and challenging their ideas so that, at the end of the day we all might move forward a little with our various knowledge bases.
Perhaps you might re-read my post. I thought I had distinguished between flex and derate ? Your manual note looks to be pretty well what I was talking about ?
All's well, though, the value of these sorts of threads is to get people thinking and challenging their ideas so that, at the end of the day we all might move forward a little with our various knowledge bases.
I think my issue is I've heard the assumed temp method referred to as both derate and reduced thrust (each on a different fleets that I've been on), hence for me both aren't suitable for reducing Vmcg.... Thus your post with the 'No, you can't do that'' at the start prompted my thoughts...
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I don’t know how you were taught to deal with an engine failure after V1, but most pilots take no action, apart from flying the aircraft, until above a safe height, for the 146, 400 ft. The retardant can be jettisoned in 3 seconds with no change of trim to the aircraft well before reaching that height. This exercise is practised regularlyin the Simulator without difficulty. Also, you are right that a qualified pilot should not have any difficulty abandoning the take of prior to V1 (however, you do not reject from V1 as you stated, once V1 has been reached you have to continue take-off). However, with the Fire Fighting 146 (referred to as a Tanker) fully loaded on a limiting runway the potential for damage may be greater stopping than getting Airborne and then significantly reducing the load. The BAe146 at a weight of 28,000 kg will climb away quite comfortably on 2 engines and this would be the weight after jettisoning the retardant.