VMCG
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VMCG
I always thought that the CAA took crosswinds into consideration when calculating VMCG, however I cant find any reference to it in JAR 25.149 Minimum Control Speeds.
So can someone tell me if it does apply for CAA certified aircraft.
Thanks.
Mutt
So can someone tell me if it does apply for CAA certified aircraft.
Thanks.
Mutt
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Mutt,
You need to look at JAR 1000.....
1000.A No pilot or pilots, or person or persons acting on the direction or suggestion or supervision of the pilot or pilots may try, or attempt to try or make or make attempt to try to comprehend or understand any or all, in whole or in part of the herein mentioned Joint Aviation Regulations, except as authorized by the Administrator or an agent appointed by, or inspected by the Administrator.
1000.B If the pilot, or group of associated pilots becomes aware of, or realizes, or detects, or discovers or finds that he, or she, or they, are or have been beginning to understand the Joint Aviation Regulations, they must immediately, within three (3) days notify, in writing, the Administrator.
1000.C Upon receipt of the above mentioned notice of impending comprehension, the Administrator will immediately rewrite the Joint Aviation Regulations in such a manner as to eliminate any further comprehension hazards.
1000.D The Administrator may, at his or her option, require the offending pilot, or pilots, to attend remedial instruction in Joint Aviation Regulations until such time that the pilot is too confused to be capable of understanding anything.
more seriously, from memory three runway design cases are looked at,
1) lateral forces on the nose gear,
2) the vertical ground reaction on either main gear should not become zero
3) the sum of all lateral ground friction forces should be greater than zero.
1) basically makes sure that the nose gear will steer the aircraft up to Vmcg
2) makes sure the aircraft does not do a wing over
3) makes sure the aircraft does not slide off the runway
where it lies in the JAR's I don't know ...
You need to look at JAR 1000.....
1000.A No pilot or pilots, or person or persons acting on the direction or suggestion or supervision of the pilot or pilots may try, or attempt to try or make or make attempt to try to comprehend or understand any or all, in whole or in part of the herein mentioned Joint Aviation Regulations, except as authorized by the Administrator or an agent appointed by, or inspected by the Administrator.
1000.B If the pilot, or group of associated pilots becomes aware of, or realizes, or detects, or discovers or finds that he, or she, or they, are or have been beginning to understand the Joint Aviation Regulations, they must immediately, within three (3) days notify, in writing, the Administrator.
1000.C Upon receipt of the above mentioned notice of impending comprehension, the Administrator will immediately rewrite the Joint Aviation Regulations in such a manner as to eliminate any further comprehension hazards.
1000.D The Administrator may, at his or her option, require the offending pilot, or pilots, to attend remedial instruction in Joint Aviation Regulations until such time that the pilot is too confused to be capable of understanding anything.
more seriously, from memory three runway design cases are looked at,
1) lateral forces on the nose gear,
2) the vertical ground reaction on either main gear should not become zero
3) the sum of all lateral ground friction forces should be greater than zero.
1) basically makes sure that the nose gear will steer the aircraft up to Vmcg
2) makes sure the aircraft does not do a wing over
3) makes sure the aircraft does not slide off the runway
where it lies in the JAR's I don't know ...
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The following is a quote from a textbook called "Fixed Wing Airworthiness", which nobody will recognise, because I won't finish writing it for at-least another 2 years....
>Requirements for VMCG and for control following an engine failure on the ground
VMCG is the minimum control speed on the ground, and is defined by the ability to maintain the runway centreline during take-off, within a given tolerance, in the event of failure of the most critical engine - which is again usually performed by shutting off fuel to an engine during a take-off run. The significance of VMCG is that above that speed, an aircraft may safely continue a take-off (assuming that sufficient thrust is available to do so) whilst below that speed, in order to remain on the runway, braking must be used and a take-off aborted. Obviously it is not the only consideration, but it is nonetheless one which must be determined, and taken into account when determining V1 - the take-off decision speed, which can never be less than VMCG (the other bound is obviously VR - the rotation speed, where in between V1 lies is a function of aircraft performance and runway length, surface and condition).
The method by which testing VMCG is carried out involves a series of take-offs, ideally into wind, with the critical engine deliberately being failed at a series of airspeeds, starting just below VR and reducing in small increments until the aircraft is unable to remain within the required distance of the runway centreline. The take-offs should be filmed from either behind or ahead of the aircraft, and in subsequent analysis of the take-off films, should determine at which engine failure speed speed adequate directional control on the runway can no-longer be maintained. Inevitably, the tests will be carried out at whatever is determined to be the most critical take-off configuration, with the worst case weight and CG conditions. Take-off trim is universally used.
Needless to say, this is a high risk exercise, which is normally carried out after all airborne minimum control speeds have been determined. The use of a very wide runway, with no significant obstructions to either side is essential, as is a very well briefed team on ever aspect of the trial. It is important in more complex aircraft to be particularly aware in VMCG tests of the flight control system - spoilers in particular can often lead to non-linear rolling moment with stick input characteristics, and may also lead to increased directional stability (weathercocking tendency) just when it is least wanted.
British Civil Airworthiness Standards Section K The quantity VMCG is not defined or used in BCAR Section K. If VMCG is required, the author recommends use of JAR-25.
Joint Airworthiness Requirements
JAR-23 The quantity VMCG is not defined or used in JAR-23. If VMCG is required, the author recommends use of JAR-25.
JAR-25 Propeller to take it’s natural position, with no pilot input to pitch setting MTOP Max. deviation from runway centreline: 30ft (9.1m), Roll Control only to be used to keep wings level whilst on the ground Max. Rudder force: 150 lbf; Nosewheel steering not permitted to be used in demonstration
Readers will note that in those standards which define a VMCG test, use of the nosewheel steering is not permitted. Conjecturing as to the reasoning behind the committees that drafted these standards, almost certainly this is to allow use of the nosewheel to counter crosswinds (which are not taken account of in these tests), but also readers mainly familiar with light aircraft, it is worth remembering that airliners usually have a separate “tiller” for control of the nosewheel steering, which is not connected to the rudder mechanism
G
N.B. Zeke, Pilots aren't expected to understand things. That's what Engineers are for.
>Requirements for VMCG and for control following an engine failure on the ground
VMCG is the minimum control speed on the ground, and is defined by the ability to maintain the runway centreline during take-off, within a given tolerance, in the event of failure of the most critical engine - which is again usually performed by shutting off fuel to an engine during a take-off run. The significance of VMCG is that above that speed, an aircraft may safely continue a take-off (assuming that sufficient thrust is available to do so) whilst below that speed, in order to remain on the runway, braking must be used and a take-off aborted. Obviously it is not the only consideration, but it is nonetheless one which must be determined, and taken into account when determining V1 - the take-off decision speed, which can never be less than VMCG (the other bound is obviously VR - the rotation speed, where in between V1 lies is a function of aircraft performance and runway length, surface and condition).
The method by which testing VMCG is carried out involves a series of take-offs, ideally into wind, with the critical engine deliberately being failed at a series of airspeeds, starting just below VR and reducing in small increments until the aircraft is unable to remain within the required distance of the runway centreline. The take-offs should be filmed from either behind or ahead of the aircraft, and in subsequent analysis of the take-off films, should determine at which engine failure speed speed adequate directional control on the runway can no-longer be maintained. Inevitably, the tests will be carried out at whatever is determined to be the most critical take-off configuration, with the worst case weight and CG conditions. Take-off trim is universally used.
Needless to say, this is a high risk exercise, which is normally carried out after all airborne minimum control speeds have been determined. The use of a very wide runway, with no significant obstructions to either side is essential, as is a very well briefed team on ever aspect of the trial. It is important in more complex aircraft to be particularly aware in VMCG tests of the flight control system - spoilers in particular can often lead to non-linear rolling moment with stick input characteristics, and may also lead to increased directional stability (weathercocking tendency) just when it is least wanted.
British Civil Airworthiness Standards Section K The quantity VMCG is not defined or used in BCAR Section K. If VMCG is required, the author recommends use of JAR-25.
Joint Airworthiness Requirements
JAR-23 The quantity VMCG is not defined or used in JAR-23. If VMCG is required, the author recommends use of JAR-25.
JAR-25 Propeller to take it’s natural position, with no pilot input to pitch setting MTOP Max. deviation from runway centreline: 30ft (9.1m), Roll Control only to be used to keep wings level whilst on the ground Max. Rudder force: 150 lbf; Nosewheel steering not permitted to be used in demonstration
Readers will note that in those standards which define a VMCG test, use of the nosewheel steering is not permitted. Conjecturing as to the reasoning behind the committees that drafted these standards, almost certainly this is to allow use of the nosewheel to counter crosswinds (which are not taken account of in these tests), but also readers mainly familiar with light aircraft, it is worth remembering that airliners usually have a separate “tiller” for control of the nosewheel steering, which is not connected to the rudder mechanism
G
N.B. Zeke, Pilots aren't expected to understand things. That's what Engineers are for.
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Genghis,
Not enough people to translate....
Sounds like an interesting book, I will buy one from you when you are finished...
Are the BCARs on the internet ?
I have found that the hardest time to control a twin jet like an A320 on one engine is at low speed and high power setting, nowhere near Vmcg. The tiller comes in handy.
Not enough people to translate....Sounds like an interesting book, I will buy one from you when you are finished...
Are the BCARs on the internet ?
I have found that the hardest time to control a twin jet like an A320 on one engine is at low speed and high power setting, nowhere near Vmcg. The tiller comes in handy.
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Mutt,
I can't speak to the European requirements, but on the presumption that this aspect of the JARs will echo the FARs, the following observations probably are relevant to the original post's question. I suspect that the JAA system is somewhat similar (except that I vaguely recall several BCAR AFM definitions including a reference to 7 knots as suggested in the previous post).
(a) the rules as they are written present two problems
(i) one has to get the correct issue for a particular Type/model to have any chance of getting the story.
Even then it may not be encompassing.
(ii) the rules as written, as they may be interpreted by the lay reader, may have little to do
with the interpretation imposed by the certification process. In particular, much of the detail
is not included in the rules as published.
(b) in respect of (ii), interpretation of the rules will be dictated by one or more of the following
(i) what the judge says after the accident enquiry
(ii) what the manufacturer negotiates with the certificating regulatory authority
(iii) what the regulator prescribes in advisory data - which is where we usually go to find out
something about what the regulator intends us to think what the rules might mean
In the case of the FAA, the useful explanatory data appears in Advisory Circulars, Orders, and the like.
In respect of Vmcg, a useful document is AC 25-7A which is the Flight Test Guide for heavy aircraft.
Unfortunately, I have to hand only the superseded -7 issue so there may be some change in the detail - although I would not expect too much substantive alteration in respect of Vmcg.
Ignoring some of the niceties,
(i) the preamble suggests a maximum wind for testing of 5 knots (preferred) and 10 knots (maximum).
(ii) the bit dealing with Vmcg indicates that the data is determined or reduced to zero wind conditions. What actually happened for a given model would be buried in the certification data.
This now ought to prompt a very pertinent question. What happens in the OEI case in a crosswind ?
Australia, if I am correct - and I may well not be, is the only country which experimented much with looking at real world operationally rational handling problems on the runway as a part of its consideration of appropriate runway widths some years ago.
During some of these flight tested programs, it became apparent that the situation with a min V1 failure at aft cg and much of a crosswind could present some nasty surprises for the unwary pilot.
Of direct relevance is the rate at which centreline deviation increases in the min V1 region under OEI conditions - this is quite alarming to any pilot who prefers boring flights and interesting overnights. In particular, crosswind from the "wrong" side has the effect of increasing the "real" Vmcg above the published figure. For one program, the manufacturer provided proprietary data for the relevant aircraft model which indicated that the increase in Vmcg with crosswind was approximately one half knot/knot and I presume that this sort of figure is likely to be typical. Thus, for a min V1 scheduled takeoff in significant crosswind conditions and with an aft cg, the aircraft is at very real risk of lateral runway departure in OEI conditions.
If you doubt this statement, try it in your simulator. Unless the sim is not programmed appropriately for this situation, you might have cause to reassess your doubt. For the program with which I am presently involved, towards the end of the endorsement sequences I give the students just such a scenario. In almost all cases, the result is a very convincing lateral departure from the runway ... along with two very wide pairs of eyes and two stunned expressions.
In the situation of takeoff from a short runway at low weight, you don't have too much in the way of options - either you
(a) delay until the crosswind abates, or you
(b) accept the risk, smug in the knowledge that you will die in some sort of legally acceptable way, I guess.
In the situation of a ferry flight, or similarly low weight operation, from a longish runway, there are, at the very least, two options -
(a) blindly use the normally scheduled min V1 data, or
(b) if such a procedure be not proscribed in your company ops manual, consider using the speed data for a higher weight, being within the applicable RTOW range for the conditions. How much higher ? I like the idea of looking to a weight which gives an increase in V1 of around half the crosswind if the cg is near the aft limit and somewhat less if the cg is further forward.
Food for thought ?
I can't speak to the European requirements, but on the presumption that this aspect of the JARs will echo the FARs, the following observations probably are relevant to the original post's question. I suspect that the JAA system is somewhat similar (except that I vaguely recall several BCAR AFM definitions including a reference to 7 knots as suggested in the previous post).
(a) the rules as they are written present two problems
(i) one has to get the correct issue for a particular Type/model to have any chance of getting the story.
Even then it may not be encompassing.
(ii) the rules as written, as they may be interpreted by the lay reader, may have little to do
with the interpretation imposed by the certification process. In particular, much of the detail
is not included in the rules as published.
(b) in respect of (ii), interpretation of the rules will be dictated by one or more of the following
(i) what the judge says after the accident enquiry
(ii) what the manufacturer negotiates with the certificating regulatory authority
(iii) what the regulator prescribes in advisory data - which is where we usually go to find out
something about what the regulator intends us to think what the rules might mean
In the case of the FAA, the useful explanatory data appears in Advisory Circulars, Orders, and the like.
In respect of Vmcg, a useful document is AC 25-7A which is the Flight Test Guide for heavy aircraft.
Unfortunately, I have to hand only the superseded -7 issue so there may be some change in the detail - although I would not expect too much substantive alteration in respect of Vmcg.
Ignoring some of the niceties,
(i) the preamble suggests a maximum wind for testing of 5 knots (preferred) and 10 knots (maximum).
(ii) the bit dealing with Vmcg indicates that the data is determined or reduced to zero wind conditions. What actually happened for a given model would be buried in the certification data.
This now ought to prompt a very pertinent question. What happens in the OEI case in a crosswind ?
Australia, if I am correct - and I may well not be, is the only country which experimented much with looking at real world operationally rational handling problems on the runway as a part of its consideration of appropriate runway widths some years ago.
During some of these flight tested programs, it became apparent that the situation with a min V1 failure at aft cg and much of a crosswind could present some nasty surprises for the unwary pilot.
Of direct relevance is the rate at which centreline deviation increases in the min V1 region under OEI conditions - this is quite alarming to any pilot who prefers boring flights and interesting overnights. In particular, crosswind from the "wrong" side has the effect of increasing the "real" Vmcg above the published figure. For one program, the manufacturer provided proprietary data for the relevant aircraft model which indicated that the increase in Vmcg with crosswind was approximately one half knot/knot and I presume that this sort of figure is likely to be typical. Thus, for a min V1 scheduled takeoff in significant crosswind conditions and with an aft cg, the aircraft is at very real risk of lateral runway departure in OEI conditions.
If you doubt this statement, try it in your simulator. Unless the sim is not programmed appropriately for this situation, you might have cause to reassess your doubt. For the program with which I am presently involved, towards the end of the endorsement sequences I give the students just such a scenario. In almost all cases, the result is a very convincing lateral departure from the runway ... along with two very wide pairs of eyes and two stunned expressions.
In the situation of takeoff from a short runway at low weight, you don't have too much in the way of options - either you
(a) delay until the crosswind abates, or you
(b) accept the risk, smug in the knowledge that you will die in some sort of legally acceptable way, I guess.
In the situation of a ferry flight, or similarly low weight operation, from a longish runway, there are, at the very least, two options -
(a) blindly use the normally scheduled min V1 data, or
(b) if such a procedure be not proscribed in your company ops manual, consider using the speed data for a higher weight, being within the applicable RTOW range for the conditions. How much higher ? I like the idea of looking to a weight which gives an increase in V1 of around half the crosswind if the cg is near the aft limit and somewhat less if the cg is further forward.
Food for thought ?
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Alex and John's memories regarding the 7 knot component are correct. This also had a significant effect on the performance schedules of the MD8X series of aircraft when certified by the CAA. Some of our senior readers may be able to remember if similar penalties were applied to the DC9 family prior to this.
The post above this clearly demonstrates the importance of a crosswind component while involuntarily exploring the concept of Vmcg. I will refrain from leaping onto my hobby horse of what is essential safety legislation and the role of commercial interests in its creation.
------------------
Regards from the Towers
[email protected]
The post above this clearly demonstrates the importance of a crosswind component while involuntarily exploring the concept of Vmcg. I will refrain from leaping onto my hobby horse of what is essential safety legislation and the role of commercial interests in its creation.
------------------
Regards from the Towers
[email protected]
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Ladies and Gentlemen
While appreciating the considerable risks of establishing VMCG during certification, (given the requirement to maintain the good engine at full throttle for at least five seconds after the yaw) I have never felt this would be a hairy event in normal ops. because most crews would get all throttles off well before five seconds. They are in a stop situation after all.
So while a stong cross wind from the side you lost the donk could have a very nasty effect so far as the initial yaw rate was concerned, would that not also cue you chop all power even faster?
Please put me straight if I am all wrong on this.
JF
While appreciating the considerable risks of establishing VMCG during certification, (given the requirement to maintain the good engine at full throttle for at least five seconds after the yaw) I have never felt this would be a hairy event in normal ops. because most crews would get all throttles off well before five seconds. They are in a stop situation after all.
So while a stong cross wind from the side you lost the donk could have a very nasty effect so far as the initial yaw rate was concerned, would that not also cue you chop all power even faster?
Please put me straight if I am all wrong on this.
JF
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John F,
Ah hah ! ... someone took the bait ....
I concur with your comments - almost ...
BUT .. there is one problem which seems to be ignored to a great extent and is one which I try to get across to my students - just to have it in the back of their minds.
In the case of lightweight takeoffs, V-schedule chart data (however presented) exhorts us to watch out for Vmcg in the event of a min V1 sort of takeoff. Now, depending on the amendment list state of play for the certification design standards, we can find ourselves in the situation where we are scheduling a min V1 at or near the published (nil or low wind) Vmcg.
Whereupon the blissfully ignorant (of the problem) pilot may well happily continue the takeoff if the failure is at or about V1 - and, in the current philosophical climate of being "go-oriented" this might just mean that the pilot ... on this unfortunate occasion where the cg is well aft .. and the crosswind rather bracing .. not to mention being from the wrong side .... might just have shaded "his" V1 a few knots.
Now I, probably like many pilots, thought that the Australian regulator's concern with runway width was so much waffle. That is, until I watched a video taken from the end of a longish runway somewhere in the Antipodes, of a well loved narrow body twin being subjected to engine cuts over a range of speeds in the vicinity of Vmcg.
The video camera was fitted with a 1000mm lens (or was it 800mm ? - I can't quite recall now) which gave somewhat less than a half degree field of view. That converts to the wingtips being well outside the sides of the video image at 2nm).
I suggested in a previous post that the runway centreline deviation (which is basically what Vmcg is looking at in the continued takeoff case) becomes interesting around Vmcg and that the effect of crosswind is to move this asymptote to the perpendicular up the graph to a higher speed - this is the problem.
I still have the relevant videos on file (somewhere) - a beer is the cost of a look. It is quite sobering to see a moderate size aeroplane disappear out of the field of view - and this a Type which pilots reverently assured me ... "tracks on rails with an engine failure". Regrettably I never flew the Type.
John suggests that the scenario is a non event in the RTO case and our observations of several Types quite support that thought.
The problem is when the takeoff is continued.
Now, I am not suggesting that we ought not get out of bed in the morning because of this particular risk. However, it is a useful thing for the pilot to understand - in these restricted conditions, a continued takeoff may not be possible, especially on a narrowish sort of runway. This is one of those times when being go-oriented might not be the best risk averse option.
If a company's operational requirements do not proscribe such a procedure, and circumstances permit, the whole problem goes away if V1 is increased by a suitable margin to account for the crosswind.
Ah hah ! ... someone took the bait ....
I concur with your comments - almost ...
BUT .. there is one problem which seems to be ignored to a great extent and is one which I try to get across to my students - just to have it in the back of their minds.
In the case of lightweight takeoffs, V-schedule chart data (however presented) exhorts us to watch out for Vmcg in the event of a min V1 sort of takeoff. Now, depending on the amendment list state of play for the certification design standards, we can find ourselves in the situation where we are scheduling a min V1 at or near the published (nil or low wind) Vmcg.
Whereupon the blissfully ignorant (of the problem) pilot may well happily continue the takeoff if the failure is at or about V1 - and, in the current philosophical climate of being "go-oriented" this might just mean that the pilot ... on this unfortunate occasion where the cg is well aft .. and the crosswind rather bracing .. not to mention being from the wrong side .... might just have shaded "his" V1 a few knots.
Now I, probably like many pilots, thought that the Australian regulator's concern with runway width was so much waffle. That is, until I watched a video taken from the end of a longish runway somewhere in the Antipodes, of a well loved narrow body twin being subjected to engine cuts over a range of speeds in the vicinity of Vmcg.
The video camera was fitted with a 1000mm lens (or was it 800mm ? - I can't quite recall now) which gave somewhat less than a half degree field of view. That converts to the wingtips being well outside the sides of the video image at 2nm).
I suggested in a previous post that the runway centreline deviation (which is basically what Vmcg is looking at in the continued takeoff case) becomes interesting around Vmcg and that the effect of crosswind is to move this asymptote to the perpendicular up the graph to a higher speed - this is the problem.
I still have the relevant videos on file (somewhere) - a beer is the cost of a look. It is quite sobering to see a moderate size aeroplane disappear out of the field of view - and this a Type which pilots reverently assured me ... "tracks on rails with an engine failure". Regrettably I never flew the Type.
John suggests that the scenario is a non event in the RTO case and our observations of several Types quite support that thought.
The problem is when the takeoff is continued.
Now, I am not suggesting that we ought not get out of bed in the morning because of this particular risk. However, it is a useful thing for the pilot to understand - in these restricted conditions, a continued takeoff may not be possible, especially on a narrowish sort of runway. This is one of those times when being go-oriented might not be the best risk averse option.
If a company's operational requirements do not proscribe such a procedure, and circumstances permit, the whole problem goes away if V1 is increased by a suitable margin to account for the crosswind.
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<font face="Verdana, Arial, Helvetica" size="2">Whereupon the blissfully ignorant (of the problem) pilot may well happily continue the takeoff if the failure is at or about V1</font>
JF
[This message has been edited by John Farley (edited 30 May 2001).]
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John,
I concur with your assessment in the case of a "thinking" pilot. I am aware of your extensive FT background and a refusal above scheduled V1 in such circumstances is exactly what I would expect anyone with a test background to do - accepting the inevitable overrun in a limiting accel stop situation.
However, and this is the ONLY reason I raised the issue, the great majority of line pilots do not have the benefit of the sort of background which you, and others of similar ilk, have. In particular, they don't have the exposure to unusual handling situations requiring rapid and novel solutions.
Many, it seems, have precious little knowledge of matters outside their specific directed training.
In addition, the line pilot is subjected to a barrage of rote training in respect of when he should stop and when he should go, leading to a potential problem in respect of expectation.
Simulator observations over a period of time with a range of line pilots (including some with very significant experience in terms of hours) indicate to me that the line reality may be very different to what the TP would sensibly do.
Many, and possibly most(?), line pilots, because of a startle factor and expectation, may (and I suspect, will) keep going, initially, in spite of the clearly obvious outcome. The short window of opportunity to refuse is, in such a circumstance, quite critical.
My interest in this topic is to provoke some thought amongst the airline training people about a little area which can present a big surprise to the unsuspecting pilot.
I readily admit that I don't know whether I am seeing a bigger problem than might exist in reality. It just seems appropriate to me that the flight standards training implications ought to be canvassed.
Hence my comment in the earlier post that ...
"..this is one of those times when being go-oriented might not be the best risk averse option..."
[This message has been edited by john_tullamarine (edited 31 May 2001).]
[This message has been edited by john_tullamarine (edited 31 May 2001).]
I concur with your assessment in the case of a "thinking" pilot. I am aware of your extensive FT background and a refusal above scheduled V1 in such circumstances is exactly what I would expect anyone with a test background to do - accepting the inevitable overrun in a limiting accel stop situation.
However, and this is the ONLY reason I raised the issue, the great majority of line pilots do not have the benefit of the sort of background which you, and others of similar ilk, have. In particular, they don't have the exposure to unusual handling situations requiring rapid and novel solutions.
Many, it seems, have precious little knowledge of matters outside their specific directed training.
In addition, the line pilot is subjected to a barrage of rote training in respect of when he should stop and when he should go, leading to a potential problem in respect of expectation.
Simulator observations over a period of time with a range of line pilots (including some with very significant experience in terms of hours) indicate to me that the line reality may be very different to what the TP would sensibly do.
Many, and possibly most(?), line pilots, because of a startle factor and expectation, may (and I suspect, will) keep going, initially, in spite of the clearly obvious outcome. The short window of opportunity to refuse is, in such a circumstance, quite critical.
My interest in this topic is to provoke some thought amongst the airline training people about a little area which can present a big surprise to the unsuspecting pilot.
I readily admit that I don't know whether I am seeing a bigger problem than might exist in reality. It just seems appropriate to me that the flight standards training implications ought to be canvassed.
Hence my comment in the earlier post that ...
"..this is one of those times when being go-oriented might not be the best risk averse option..."
[This message has been edited by john_tullamarine (edited 31 May 2001).]
[This message has been edited by john_tullamarine (edited 31 May 2001).]
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John T
What type is the aircraft in the video, if you don't want to say could you describe the general layout of the type?
If this is indeed an area where a transport category aircraft is barely or even not controllable in normal operation,how was it certified?
Most ferry or very lightweight takeoffs will be accomplished at very reduced thrusts under normal circumstances.This would improve matters I take it?
Sounds like a good plan to up the speeds a bit as you suggested earlier.Jeez this flying's getting dodgier by the day.
What type is the aircraft in the video, if you don't want to say could you describe the general layout of the type?
If this is indeed an area where a transport category aircraft is barely or even not controllable in normal operation,how was it certified?
Most ferry or very lightweight takeoffs will be accomplished at very reduced thrusts under normal circumstances.This would improve matters I take it?
Sounds like a good plan to up the speeds a bit as you suggested earlier.Jeez this flying's getting dodgier by the day.
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Flanker,
(a) I would need the concurrence of other people to identify the exercise.
A most venerated rear mounted narrow bodied twin Type. I still kick myself for not bidding onto it for the experience.
And the Type doesn't matter, anyway - the problem exists whenever the AFM permits the scheduling of V1 down around Vmcg. Of course some aircraft have Vmcg so low that this never happens - in which case the problem goes away.
Mind you, I still can recall my eyes opening wide whilst watching through the viewfinder at the time .... I became an instant convert to that School which advocates rational matching of aircraft to minimum runway width which was what the exercise at the time was all about.
(b) ... how was it certified? This really is not the point - the certification performance standards are not about guarantees - rather they provide some reference data and guidance for the information of operators and crews. It is up to the operator/pilot to pitch his tent somewhere between the regulated minimum requirements and whatever is determined to be an appropriate risk management position, level playing field profit considerations notwithstanding.
The Vmcg certification requirement provides a very reasonable control boundary adequate for most operational circumstances. However, within restricted areas in the normal operating envelope, perhaps there is a flight standards and training problem/consideration to be mulled over.
(c) Most ferry or very lightweight ... The problem only must be worn (if you can't defer the operation) in the case of short runways where you are pretty well stuck with a low V1. In the event that there is lots of runway, then the problem can be avoided just by using some of the spare V1 range available up to the RTOW limits for the particular runway.
Perhaps I have needlessly caused anxiety.
This is a very minor problem in the overall scheme of things. I just think that it needs an occasional airing so that pilots have it tucked away in the back of the mind.
(a) I would need the concurrence of other people to identify the exercise.
A most venerated rear mounted narrow bodied twin Type. I still kick myself for not bidding onto it for the experience.
And the Type doesn't matter, anyway - the problem exists whenever the AFM permits the scheduling of V1 down around Vmcg. Of course some aircraft have Vmcg so low that this never happens - in which case the problem goes away.
Mind you, I still can recall my eyes opening wide whilst watching through the viewfinder at the time .... I became an instant convert to that School which advocates rational matching of aircraft to minimum runway width which was what the exercise at the time was all about.
(b) ... how was it certified? This really is not the point - the certification performance standards are not about guarantees - rather they provide some reference data and guidance for the information of operators and crews. It is up to the operator/pilot to pitch his tent somewhere between the regulated minimum requirements and whatever is determined to be an appropriate risk management position, level playing field profit considerations notwithstanding.
The Vmcg certification requirement provides a very reasonable control boundary adequate for most operational circumstances. However, within restricted areas in the normal operating envelope, perhaps there is a flight standards and training problem/consideration to be mulled over.
(c) Most ferry or very lightweight ... The problem only must be worn (if you can't defer the operation) in the case of short runways where you are pretty well stuck with a low V1. In the event that there is lots of runway, then the problem can be avoided just by using some of the spare V1 range available up to the RTOW limits for the particular runway.
Perhaps I have needlessly caused anxiety.
This is a very minor problem in the overall scheme of things. I just think that it needs an occasional airing so that pilots have it tucked away in the back of the mind.
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JT,
My question,
We currently operate a large trijet on ad hoc charter , this means often positioning empty . Short legs with very low weight take offs. The aeroplane goes like a screeming banshee when empty and the only way to keep thing sensible is to use a big de-rate.
However the MTOW tables we use for calcs although very good for NORMAL weights leave us with some odd speeds when very light.
e.g. xxx r/w 03 10000`+ ATOW 120tonnes
max derate uses an assumed temp of +54 and gives a max to of 209tonnes and the v speeds for this weight. We use these speeds but although they are safe, leave the aircraft on the runway for much longer than it should be.
The alternative is to use the speeds from our weight/flap tables for vr and v2 and as the vr speed is always less than v1 from the MTOW table, use v1/vr unity.
We do not use this method currently but are disscusing its merits as the aircraft is realy keen to fly 20 kts below the v1s we currently use.
This threatd has highlighted another consideration as the low weight vr speeds are always vmcg limited and the v2 speeds are often min v2 .
Any thoughts?
My question,
We currently operate a large trijet on ad hoc charter , this means often positioning empty . Short legs with very low weight take offs. The aeroplane goes like a screeming banshee when empty and the only way to keep thing sensible is to use a big de-rate.
However the MTOW tables we use for calcs although very good for NORMAL weights leave us with some odd speeds when very light.
e.g. xxx r/w 03 10000`+ ATOW 120tonnes
max derate uses an assumed temp of +54 and gives a max to of 209tonnes and the v speeds for this weight. We use these speeds but although they are safe, leave the aircraft on the runway for much longer than it should be.
The alternative is to use the speeds from our weight/flap tables for vr and v2 and as the vr speed is always less than v1 from the MTOW table, use v1/vr unity.
We do not use this method currently but are disscusing its merits as the aircraft is realy keen to fly 20 kts below the v1s we currently use.
This threatd has highlighted another consideration as the low weight vr speeds are always vmcg limited and the v2 speeds are often min v2 .
Any thoughts?
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I'm very relieved to report that the types I have flown for the last ten years (Boeing twins on UK CAA register) have covered the very light and ferry sector cases with an imposed minimum V1 and never any lower. QRH, FMC and AFM V1's go 6 or 7 knots lower than the imposed figure. Amplifying on the reasons for this is pointless as John T has explained it far better than I could.
Having said that: Mutt must be glad he's on holiday and well out of this. On one thread I'm arguing he's keeping his guys on the runway too long and here I'm glad to be staying firmly on the ground a little longer - funny old world huh
------------------
Regards from the Towers
[email protected]
[This message has been edited by PPRuNe Towers (edited 31 May 2001).]
[This message has been edited by PPRuNe Towers (edited 31 May 2001).]
Having said that: Mutt must be glad he's on holiday and well out of this. On one thread I'm arguing he's keeping his guys on the runway too long and here I'm glad to be staying firmly on the ground a little longer - funny old world huh
------------------
Regards from the Towers
[email protected]
[This message has been edited by PPRuNe Towers (edited 31 May 2001).]
[This message has been edited by PPRuNe Towers (edited 31 May 2001).]
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FE Hoppy
Is "Hoppy" the same as "Skippy" ? .. if so, g'day ..
First, I am envious - really and truly, I am - obviously you have a most wonderful answer to an older young chap's desires for get up and go - even if a lot more expensive than Sildenafil - and, no, I have yet to contemplate seeing things in shades of whatever colour is reported to be the side effect. Closest in my background was an empty Electra on a cold night and with nothing better to do ...
(a) Without having a look at your AFM with chin in one hand and a pencil in the other, the following suggestion might not be appropriate. However, my initial line of enquiry would go along this pathway for a simple solution -
(i) prepare separate general takeoff charts for accel stop, separates/composite for takeoff distance (although I would expect the AEO case to be convincingly limiting), and gradient charts for BRW/V2. You probably have such animals in your company Ops Manual performance volume at present.
(ii) using whatever level of equivalent temp derate you desire (and it must be a wonderfully terrifying experience if you go full grunt in these circumstances) note the limit RTOW from your individual runway chart.
(iii) use the general charts to figure the nominal accel stop and takeoff distances for this weight, and the gradient capability at the scheduled V speeds.
(iv) use the general charts to figure the lowest V1 which will not cause you to exceed the above distance figures for your BRW, with a suitable V2 to achieve not less than the scheduled V2's gradient capability.
(v) schedule a V1 somewhere between the two limiting values according to your horoscope's recommendations for the day.
What this approach achieves is to make sure that
(i) the modified takeoff gets to a similar point down the runway at 35 ft when compared to normal chart data.
(ii) the subsequent climb is not inferior to that scheduled normally, so that you don't have to worry about obstacles. This probably isn't going to be limiting at all.
(iii) you know how many miles of pad you have for the accel stop.
Given the impressive T/W for such a takeoff, I probably wouldn't be too worried about Vmcg - you would be well and truly through the region by the time the aircraft realised it had suffered a failure. Then again, you have a wide range of available V1 figures - so you can pays your money and takes your chances according to your philosophical preferences.
I wouldn't fancy using needlessly high V1 and Vr figures if the bird has a desire to skate.
(PS .. I quote very reasonably for this sort of work ......and a discount would accrue, depending on how many rides I can come along on for the experience)
Is "Hoppy" the same as "Skippy" ? .. if so, g'day ..
First, I am envious - really and truly, I am - obviously you have a most wonderful answer to an older young chap's desires for get up and go - even if a lot more expensive than Sildenafil - and, no, I have yet to contemplate seeing things in shades of whatever colour is reported to be the side effect. Closest in my background was an empty Electra on a cold night and with nothing better to do ...
(a) Without having a look at your AFM with chin in one hand and a pencil in the other, the following suggestion might not be appropriate. However, my initial line of enquiry would go along this pathway for a simple solution -
(i) prepare separate general takeoff charts for accel stop, separates/composite for takeoff distance (although I would expect the AEO case to be convincingly limiting), and gradient charts for BRW/V2. You probably have such animals in your company Ops Manual performance volume at present.
(ii) using whatever level of equivalent temp derate you desire (and it must be a wonderfully terrifying experience if you go full grunt in these circumstances) note the limit RTOW from your individual runway chart.
(iii) use the general charts to figure the nominal accel stop and takeoff distances for this weight, and the gradient capability at the scheduled V speeds.
(iv) use the general charts to figure the lowest V1 which will not cause you to exceed the above distance figures for your BRW, with a suitable V2 to achieve not less than the scheduled V2's gradient capability.
(v) schedule a V1 somewhere between the two limiting values according to your horoscope's recommendations for the day.
What this approach achieves is to make sure that
(i) the modified takeoff gets to a similar point down the runway at 35 ft when compared to normal chart data.
(ii) the subsequent climb is not inferior to that scheduled normally, so that you don't have to worry about obstacles. This probably isn't going to be limiting at all.
(iii) you know how many miles of pad you have for the accel stop.
Given the impressive T/W for such a takeoff, I probably wouldn't be too worried about Vmcg - you would be well and truly through the region by the time the aircraft realised it had suffered a failure. Then again, you have a wide range of available V1 figures - so you can pays your money and takes your chances according to your philosophical preferences.
I wouldn't fancy using needlessly high V1 and Vr figures if the bird has a desire to skate.
(PS .. I quote very reasonably for this sort of work ......and a discount would accrue, depending on how many rides I can come along on for the experience)
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On a closely allied subject, does anybody know of any work / formulae / modified WAT charts / whatever available to predict variations in take-off run due to a crosswind? We all know that a crosswind increases your take-off run, but I've never seen anything to predict by how much?
G
G
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Genghis,
I have some notes on calculating the stability and control derivatives to maintain lateral directional control during the takeoff ground run.
Only have 3 equations, but 5 unknows...normal story some assumptions have to be made.
Using these plus the longitudinal control requirements you could build up a lift & drag model for the aircraft which could be used to generate the takeoff charts.
I have not seen results of this type of analysis published before in aircraft POH, just a factored normal takeoff distance.
------------------
It is possible to fly without motors, but not without knowledge and skill.
— Wilbur Wright
I have some notes on calculating the stability and control derivatives to maintain lateral directional control during the takeoff ground run.
Only have 3 equations, but 5 unknows...normal story some assumptions have to be made.
Using these plus the longitudinal control requirements you could build up a lift & drag model for the aircraft which could be used to generate the takeoff charts.
I have not seen results of this type of analysis published before in aircraft POH, just a factored normal takeoff distance.
------------------
It is possible to fly without motors, but not without knowledge and skill.
— Wilbur Wright