F/Lynx all systems go at AW
Dangermouse - I am afraid your comments regarding Nr control rather expose the difference between theoretical design parameters and the real world experience.
I am sure in one of your books somewhere it tell you that the engine governing system maintains the Nr inside strictly defined limits - that it does when power is applied but the droop law slope of any helicopter governor will have to shallow off at the bottom to prevent hunting in low power situations and, once the Nr is being driven up by other factors ie disc loading in manoeuvres, the throttle can only back off so far.
Low Nr isn't generally a problem in the Lynx since the engines are quite powerful and the governors work well - it is high Nr that can only be controlled by the pilot raising the lever that is the problem. A rapid, tactical descent followed by a flaring turn to wash off speed and make an expeditious arrival in an LS is the type of manoeuvre that regularly tries to wind the Nr off the clock in a heavy Lynx - adding to the AUM will just make it worse.
Your answer will probably be to train the pilots better! The condition is manageable at present AUM but will require even more pilot input and control (when he is trying to concentrate on not getting shot down) if you make the FLynx heavier. Helicopter designers are supposed to make each generation of military helicopters easier to fly so that the pilot can use the aircraft as a weapon of war to its best effect.
I would not for a moment exonerate the IPTs in the flawed procurement process but AW have been guilty in the past of presenting the IPT with a 'solution' to a problem in meeting the required capability which leaves the IPT with the choice to either accept the compromise or face further delays/costs in getting the product to the front-line.
I am sure in one of your books somewhere it tell you that the engine governing system maintains the Nr inside strictly defined limits - that it does when power is applied but the droop law slope of any helicopter governor will have to shallow off at the bottom to prevent hunting in low power situations and, once the Nr is being driven up by other factors ie disc loading in manoeuvres, the throttle can only back off so far.
Low Nr isn't generally a problem in the Lynx since the engines are quite powerful and the governors work well - it is high Nr that can only be controlled by the pilot raising the lever that is the problem. A rapid, tactical descent followed by a flaring turn to wash off speed and make an expeditious arrival in an LS is the type of manoeuvre that regularly tries to wind the Nr off the clock in a heavy Lynx - adding to the AUM will just make it worse.
Your answer will probably be to train the pilots better! The condition is manageable at present AUM but will require even more pilot input and control (when he is trying to concentrate on not getting shot down) if you make the FLynx heavier. Helicopter designers are supposed to make each generation of military helicopters easier to fly so that the pilot can use the aircraft as a weapon of war to its best effect.
I would not for a moment exonerate the IPTs in the flawed procurement process but AW have been guilty in the past of presenting the IPT with a 'solution' to a problem in meeting the required capability which leaves the IPT with the choice to either accept the compromise or face further delays/costs in getting the product to the front-line.
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thanks for the clarification
and the cogent argument.
however;
Modern engines (T700/RTM322/T800 etc) are isonchronously governed using NR as the prime control law which means they have no droop characteristics down to 0% Tq and sit at the governed Nr in autorotation (same as when power on). The case you specify is akin to an autorotation and I agree that in that case rotor speed is just down to rotor pitch control, (the engines by definition not doing anything) but that's true in any autorotation scenario. It may be that the specified target AUM for the Flynx using the existing rotor system is too high for that type of manouevre to be carried out, I guess only time and flight testing will tell (from a quick search the Flynx AUM is beyond any existing variant AUM)
It would appear that the only thing to do would be to;
a) train the pilots better (!!) or
b) to increase the inertia of the disc to prevent a rapid split off (this may happen if the blades change in the future but that's not going to happen soon).
c) limit the aircraft mass until b) happens if a) doesn't work because as Scotty says 'Yae cannae change the laws of physics' and converting descent energy into rotor speed MUST add kinetic energy to the disc.
The improvement in helicopter technology is there (BERP4 for instance) and some is being incorporated (crash worthiness, FADEC) but again the MoD arent prepared to pay for it all yet (the spectre of limited funding rears it's head again).
I dont follow the statement 'presenting the IPT with a 'solution' to a problem in meeting the required capability' as being a problem, surely that's what they are meant to do (my underlining) and as long as the requirement is met (which means it isn't a compromise, it's spec compliance)then it's good business practice.
DM
however;
Modern engines (T700/RTM322/T800 etc) are isonchronously governed using NR as the prime control law which means they have no droop characteristics down to 0% Tq and sit at the governed Nr in autorotation (same as when power on). The case you specify is akin to an autorotation and I agree that in that case rotor speed is just down to rotor pitch control, (the engines by definition not doing anything) but that's true in any autorotation scenario. It may be that the specified target AUM for the Flynx using the existing rotor system is too high for that type of manouevre to be carried out, I guess only time and flight testing will tell (from a quick search the Flynx AUM is beyond any existing variant AUM)
It would appear that the only thing to do would be to;
a) train the pilots better (!!) or
b) to increase the inertia of the disc to prevent a rapid split off (this may happen if the blades change in the future but that's not going to happen soon).
c) limit the aircraft mass until b) happens if a) doesn't work because as Scotty says 'Yae cannae change the laws of physics' and converting descent energy into rotor speed MUST add kinetic energy to the disc.
The improvement in helicopter technology is there (BERP4 for instance) and some is being incorporated (crash worthiness, FADEC) but again the MoD arent prepared to pay for it all yet (the spectre of limited funding rears it's head again).
I dont follow the statement 'presenting the IPT with a 'solution' to a problem in meeting the required capability' as being a problem, surely that's what they are meant to do (my underlining) and as long as the requirement is met (which means it isn't a compromise, it's spec compliance)then it's good business practice.
DM
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DM, Thanks, I do actually agree with your last. It is not a one pointed 'jab' at AW and there is a wider villain here. From the ground, I can assure you that it is very hard to get any honest empathy from the non mil side, I have tried.
It would seem that AW can just wait until, because we can't any more, there is no option to accept second best . It is defiantly a monopoly with a .gov.uk cheque at the end - it is SO VERY frustrating.
I am wrong to berate the H&S instructions and blame others for doing their mandated, ill advised will. I can assure you I am not the only person who WILL ignore them if it saves life or gets a very important job done (I could also say that I would use them to my advantage if it had the same effect - fickle or what!!) but do get annoyed when they are used as a weapon to NOT give us what we want - eg - tough, you got the seats as against OK, we will adapt it so you have enough seats, can you see the subtle difference?
On the Nr, I can verily easily over speed the head with power applied, if heavy. Heavy being a lot less than the predicted weight of the Mk 11 Lynx, sorry the all new FLynx - not able to comment on the 800s. The 800s being another point, if we didn't accept the Mk11, we were not going to get the 800s, how was that acting in our best interests??
It would seem that AW can just wait until, because we can't any more, there is no option to accept second best . It is defiantly a monopoly with a .gov.uk cheque at the end - it is SO VERY frustrating.
I am wrong to berate the H&S instructions and blame others for doing their mandated, ill advised will. I can assure you I am not the only person who WILL ignore them if it saves life or gets a very important job done (I could also say that I would use them to my advantage if it had the same effect - fickle or what!!) but do get annoyed when they are used as a weapon to NOT give us what we want - eg - tough, you got the seats as against OK, we will adapt it so you have enough seats, can you see the subtle difference?
On the Nr, I can verily easily over speed the head with power applied, if heavy. Heavy being a lot less than the predicted weight of the Mk 11 Lynx, sorry the all new FLynx - not able to comment on the 800s. The 800s being another point, if we didn't accept the Mk11, we were not going to get the 800s, how was that acting in our best interests??
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thanks for the further replies
It's nice to see that on this discussion at least we are all staying grown up and not getting personal, even if we disgree with some posters.
I think what we are seeing here is a reflection on the lack of understanding between users and producers (interestingly this same thing has been highlighted on the A400 thread as well). Unfortunately this always comes back to funding, no doubt the Lynx could have been adapted to meet ALL the different users requirements but in that case the cost would have been unacceptable (either in monetary terms or political terms if something else had been selected). What you want often isnt what they can afford!!
By now everyone must recognise that protecting UK jobs is part of the UK goverments responsibility whether any us of like it or not.
It is probable that the final weight of the Flynx will only be with a new rotor fitted which no doubt will go some way to alleviate the current problems. Again overspeeding the head whilst power on is down to engine governing not backing the throttle off quickly enough (maybe the actual condition was really in autorotative flight but the engine didnt react quickly enough)
DM
I think what we are seeing here is a reflection on the lack of understanding between users and producers (interestingly this same thing has been highlighted on the A400 thread as well). Unfortunately this always comes back to funding, no doubt the Lynx could have been adapted to meet ALL the different users requirements but in that case the cost would have been unacceptable (either in monetary terms or political terms if something else had been selected). What you want often isnt what they can afford!!
By now everyone must recognise that protecting UK jobs is part of the UK goverments responsibility whether any us of like it or not.
It is probable that the final weight of the Flynx will only be with a new rotor fitted which no doubt will go some way to alleviate the current problems. Again overspeeding the head whilst power on is down to engine governing not backing the throttle off quickly enough (maybe the actual condition was really in autorotative flight but the engine didnt react quickly enough)
DM
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DM,
No-one has ever had a big problem with overspeeding a head with power on. Unfortunately it is a much less effective and therefore much more dangerous tactical descent and approach if you have to keep the Tq high enough to govern NR. And limiting the AUM is not an answer - your 3 troops that FLynx could put into that LS is now 1, and the aircraft will need to go for fuel before it can pick up the next solitary troop for the LS.
No-one has ever had a big problem with overspeeding a head with power on. Unfortunately it is a much less effective and therefore much more dangerous tactical descent and approach if you have to keep the Tq high enough to govern NR. And limiting the AUM is not an answer - your 3 troops that FLynx could put into that LS is now 1, and the aircraft will need to go for fuel before it can pick up the next solitary troop for the LS.
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No, came thundering round the corner, the mighty Gem roaring, lots of troops and off she jolly well went, nothing on the clock but the makers name - as they say (pointer being far to right in this case).
I still believe that there should and could be more joint pressure on - whoever, Gov, Mod, IPT or AW to try a little harder to compromise, not just cold business profiteering. Who knows, I might be able to get my job done quicker and spend Crimbo at home instead of – umm - not there!!!!
I still believe that there should and could be more joint pressure on - whoever, Gov, Mod, IPT or AW to try a little harder to compromise, not just cold business profiteering. Who knows, I might be able to get my job done quicker and spend Crimbo at home instead of – umm - not there!!!!
Dangermouse - my point about providing 'solutions' is that if there is an IPT/customer requirement that AW can't meet then they often offer what they have available on the shelf which is usually far less capable than was actually required. Then, when the IPT/customer complains they are told that if they really want the required capability then it will cost more money and take longer. The inevitable result is that the IPT/customer ends up having to concede capability because the manufacturer can't actually deliver what they promised.
This is not the same as producing a product which fully meets the IPT/customer requirements.
You don't seem to understand, despite several pilots telling you, that the Nr on the Lynx is lively, ie any venture into the low power end of the spectrum when manoeuvring results in rapid increases in Nr - far more than most other helicopters. It is completely irrelevant to isynchronous governing. Overspeeding the head with power on is not a function of the throttle not backing off quickly enough, it is a function of the powerful accelerative forces in the rotor system (which is in fact quite high inertia already) during flaring and turning manoeuvres.
It would appear that the blades and rotor system on FLynx will be exactly the same as on the present one so any increase in AUM brings handling penalties. And as we have already stated, increasing the AUM doesn't achieve anything unless you can fit troops into the cabin or weapons on pylons - what system is FLynx going to be fitted with for the battlefield variant?
It is a persistant AW myth that simply increasing the AUM of the aircraft will bring new capability to the battlefield - window dressing and hyperbole to disguise the poor suitability of the platform to the task.
This is not the same as producing a product which fully meets the IPT/customer requirements.
You don't seem to understand, despite several pilots telling you, that the Nr on the Lynx is lively, ie any venture into the low power end of the spectrum when manoeuvring results in rapid increases in Nr - far more than most other helicopters. It is completely irrelevant to isynchronous governing. Overspeeding the head with power on is not a function of the throttle not backing off quickly enough, it is a function of the powerful accelerative forces in the rotor system (which is in fact quite high inertia already) during flaring and turning manoeuvres.
It would appear that the blades and rotor system on FLynx will be exactly the same as on the present one so any increase in AUM brings handling penalties. And as we have already stated, increasing the AUM doesn't achieve anything unless you can fit troops into the cabin or weapons on pylons - what system is FLynx going to be fitted with for the battlefield variant?
It is a persistant AW myth that simply increasing the AUM of the aircraft will bring new capability to the battlefield - window dressing and hyperbole to disguise the poor suitability of the platform to the task.
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sorry that's wrong
I don't get where you are coming from CRAB, you seem very confused with terminology
my point about providing 'solutions' is that if there is an IPT/customer requirement that AW can't meet then they often offer what they have available on the shelf which is usually far less capable than was actually required ( that's the way of the world, not everything is available off the shelf). Then, when the IPT/customer complains (it's hardly fair to register a complaint because what is wanted isn't available off the shelf) they are told that if they really want the required capability then it will cost more money and take longer (what's wrong with that? development to meet a specific requirement does take time and money, why should the manufacturer pay for that, it's the customer placing the requirement) The inevitable result is that the IPT/customer ends up having to concede capability because the manufacturer can't actually deliver what they promised. (there has been no promise made or broken!! the manufacturer said what he can deliver off the shelf, or what could be delivered if funded to change what is currently available, there is no promise anywhere until a contract is placed but I guess you are assuming that manufacturers always lie about deliveries in any case)
If you think that a response to a request stating 'we cant do it' is a Promise to say 'we CAN do it' you have a very poor understanding of the English language.
If AW (or anyone else) don't have anything available to fully meet any requirement of course it will take time and money to arrive at one that will, it's naive to think anything else. If what is available is acceptable within any given timescale and budget that's what is delivered, if it's not acceptable it's either not bought or incurs costs to make it acceptable, theres nothing new in that.
I also completely disagree with the assertion that a power on manoeuvre has nothing to do with engine control authority, by definition a power on state requires energy to be put into the system (by the engines) to maintain rotor speed and therefore it all comes down to engine control providing more energy than needed for any particular manoeuvre.
As I said a few posts ago a governing sytem without adequate authority will exacerbate the inherent trend of a highly loaded disc to accelerate during a disc off loading manoeuvre, that's basic physics:-
If energy demand at the time is lower than the sum of (the energy transfer by the manoeuvre plus energy supplied by the engines) = the rotor speeds up,
so
If the engine energy supply is lowered in time the energy sum balances = rotor speed won't change (or you are in auto), conversely if due to low authority control engine energy supply is not lowered in time the rotor upspeeds.
I am not confusing power off rotor control with power on and fully accept that the Lynx has a lively rotor when unloaded, however all the input so far appears to be from people experienced in Gem operations, not T800 so any comments made regarding Flynx Nr control are based on false assumptions.Theoretically as the T800 is isochronously governed it should be possible to keep the Tq at a very low value and still have the Nr governed (again when power off it's all down to the rotor) so that a nearly autorotative descent can be flown, that's one advantage of newer engines and their governing systems.
I agree with the views regarding compromises, but any 'compromise' in this case will be expensive as there is very little that can be done cheaply to change a rotor discs behaviour, a higher disc loading means a quicker rotor response when off loading the disc.....over to Scotty again I am afraid (at least the Flynx won't have the Gems governing to worry about)
DM
my point about providing 'solutions' is that if there is an IPT/customer requirement that AW can't meet then they often offer what they have available on the shelf which is usually far less capable than was actually required ( that's the way of the world, not everything is available off the shelf). Then, when the IPT/customer complains (it's hardly fair to register a complaint because what is wanted isn't available off the shelf) they are told that if they really want the required capability then it will cost more money and take longer (what's wrong with that? development to meet a specific requirement does take time and money, why should the manufacturer pay for that, it's the customer placing the requirement) The inevitable result is that the IPT/customer ends up having to concede capability because the manufacturer can't actually deliver what they promised. (there has been no promise made or broken!! the manufacturer said what he can deliver off the shelf, or what could be delivered if funded to change what is currently available, there is no promise anywhere until a contract is placed but I guess you are assuming that manufacturers always lie about deliveries in any case)
If you think that a response to a request stating 'we cant do it' is a Promise to say 'we CAN do it' you have a very poor understanding of the English language.
If AW (or anyone else) don't have anything available to fully meet any requirement of course it will take time and money to arrive at one that will, it's naive to think anything else. If what is available is acceptable within any given timescale and budget that's what is delivered, if it's not acceptable it's either not bought or incurs costs to make it acceptable, theres nothing new in that.
I also completely disagree with the assertion that a power on manoeuvre has nothing to do with engine control authority, by definition a power on state requires energy to be put into the system (by the engines) to maintain rotor speed and therefore it all comes down to engine control providing more energy than needed for any particular manoeuvre.
As I said a few posts ago a governing sytem without adequate authority will exacerbate the inherent trend of a highly loaded disc to accelerate during a disc off loading manoeuvre, that's basic physics:-
If energy demand at the time is lower than the sum of (the energy transfer by the manoeuvre plus energy supplied by the engines) = the rotor speeds up,
so
If the engine energy supply is lowered in time the energy sum balances = rotor speed won't change (or you are in auto), conversely if due to low authority control engine energy supply is not lowered in time the rotor upspeeds.
I am not confusing power off rotor control with power on and fully accept that the Lynx has a lively rotor when unloaded, however all the input so far appears to be from people experienced in Gem operations, not T800 so any comments made regarding Flynx Nr control are based on false assumptions.Theoretically as the T800 is isochronously governed it should be possible to keep the Tq at a very low value and still have the Nr governed (again when power off it's all down to the rotor) so that a nearly autorotative descent can be flown, that's one advantage of newer engines and their governing systems.
I agree with the views regarding compromises, but any 'compromise' in this case will be expensive as there is very little that can be done cheaply to change a rotor discs behaviour, a higher disc loading means a quicker rotor response when off loading the disc.....over to Scotty again I am afraid (at least the Flynx won't have the Gems governing to worry about)
DM
Last edited by dangermouse; 17th Dec 2008 at 17:34.
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My Two Cents....
Hi Peeps,
I have followed the thread with a bit of interest as i do have a background on the mighty Lynx, Since i trained on it from squirrel i found the Nr loading to to be a real horror show, exploring the AW system in the process just to make sure!
DM your point is well made about the power on /off issue with loading, and actually, through real experience of the conditions required to catch you out on a daily basis, there realy is no replacement for training and practice. It was the transition from power on to off, either intentionally or otherwise that would effect the need to have your left hand cupping the collective as the AC Comd.
I'm must admit that i find the comments about having low Tq values and still having the ability to control Nr a bit confusing, it requires pitch to create drag to slow the rotor down...i think! So fadec would not have an input, unless through an AFCS function?
With that in mind the beasty i am floating about in does have FADEC and still has the same issues as ANY other AC that is big and heavy. The Lynx, with a Fadec'd engine and greater AUM will IMHO have the same issues as now, but with good training it will be no more than another trait on a great flying airframe. Pity it is just that, a good flying machine, not necessarily a fighting machine.
If i am mistaken in any of this then please feel free to correct me, I am utter ****e at Gnd School!!
I have followed the thread with a bit of interest as i do have a background on the mighty Lynx, Since i trained on it from squirrel i found the Nr loading to to be a real horror show, exploring the AW system in the process just to make sure!
DM your point is well made about the power on /off issue with loading, and actually, through real experience of the conditions required to catch you out on a daily basis, there realy is no replacement for training and practice. It was the transition from power on to off, either intentionally or otherwise that would effect the need to have your left hand cupping the collective as the AC Comd.
I'm must admit that i find the comments about having low Tq values and still having the ability to control Nr a bit confusing, it requires pitch to create drag to slow the rotor down...i think! So fadec would not have an input, unless through an AFCS function?
With that in mind the beasty i am floating about in does have FADEC and still has the same issues as ANY other AC that is big and heavy. The Lynx, with a Fadec'd engine and greater AUM will IMHO have the same issues as now, but with good training it will be no more than another trait on a great flying airframe. Pity it is just that, a good flying machine, not necessarily a fighting machine.
If i am mistaken in any of this then please feel free to correct me, I am utter ****e at Gnd School!!
DM, I will try to make myself clear. If I want a house built, I will choose an architect who will listen to what I want, possibly amend or adjust a few things for the sake of cost, style or expedience and then produce the drawings. Then I will choose a builder who will build said residence for x pounds.
Having agreed the price the building is built to my satisfaction within the required timescale or penalties are invoked.
With AW, they are the only architect and the only builder in town so I have a choice of 1 with no competition. Then AW will look at my ideas for a house and then try to shoehorn a design they already have drawn up for a different project and try to convince me that this house of theirs is exactly what I want.
Since they are the only architects/builders in town I have little choice because I want my new house next year so I emphasise what I want and they promise that what they will deliver will be to my liking and a contract is made.
Somewhere along the line, AW realise that the bathroom design I have specified (and they have agreed to) is not going to work because their plumbing doesn't fit it. Then they tell me it will be OK because they have a very similar bathroom suite which does fit their plumbing but hasn't got the bidet, power shower and walk-in bath I asked for.
I create merry hell and ask why they said they could do the job when it was obvious from the start there was a plumbing issue. They reply by telling me I can have what I originally wanted but it will mean redesigning their plumbing rig which will take time and cost more money because it wasn't included in the original quote.
Because I am under pressure from the wife to move into the new house I have to agree and the end result is a house with a bathroom I don't like and didn't want and AW go away happy, with their profit intact and promising that an upgrade to the bathroom may well be available in a couple of years as long as I am willing to pay for it.
I think that sums up the AW experience
Back to governors - unless your 2 engines are mechanically or electrically joined, you need a droop law to allow the engines to load share. In a constant Nr (I think this is what you mean by isynchronous) system with no link between engines, one engine could idle and the other be flat out and both governors would be happy because the Nr was correct.
Back to manoeuvring the Lynx - because of the CAC (computer acceleration control) when 'G' is sensed, it offloads the rotor head by reducing collective pitch (and thus torque) - it is a clumsy system designed to minimse the effect of a cyclic AFCS runaway in pitch.
If you are in a high-speed tactical descent with say 20% Tq (ie power on) and you then flare hard, the 'G' will cause the CAC to reduce pitch and Tq and coupled with the normal flare effects due to the change in the relative airflow presented to the disc (pitch-up, increase in rotor thrust and NR) will suddenly put you in effectively a power off regime which even the cleverest governor in the world can do nothing about. Unless the collective is raised pdq, the Nr will accelerate fast and probably overspeed. We do teach pilots to lead with lever btw but it can still catch people out.
The higher the AuM, the more flare required to arrest the rate of descent and the more 'G' experienced.
The point to note is that, to use your terminology, the boundary between loaded and unloaded head can be crossed very quickly when manoeuvring hard and your clever governors won't cope.
Having agreed the price the building is built to my satisfaction within the required timescale or penalties are invoked.
With AW, they are the only architect and the only builder in town so I have a choice of 1 with no competition. Then AW will look at my ideas for a house and then try to shoehorn a design they already have drawn up for a different project and try to convince me that this house of theirs is exactly what I want.
Since they are the only architects/builders in town I have little choice because I want my new house next year so I emphasise what I want and they promise that what they will deliver will be to my liking and a contract is made.
Somewhere along the line, AW realise that the bathroom design I have specified (and they have agreed to) is not going to work because their plumbing doesn't fit it. Then they tell me it will be OK because they have a very similar bathroom suite which does fit their plumbing but hasn't got the bidet, power shower and walk-in bath I asked for.
I create merry hell and ask why they said they could do the job when it was obvious from the start there was a plumbing issue. They reply by telling me I can have what I originally wanted but it will mean redesigning their plumbing rig which will take time and cost more money because it wasn't included in the original quote.
Because I am under pressure from the wife to move into the new house I have to agree and the end result is a house with a bathroom I don't like and didn't want and AW go away happy, with their profit intact and promising that an upgrade to the bathroom may well be available in a couple of years as long as I am willing to pay for it.
I think that sums up the AW experience
Back to governors - unless your 2 engines are mechanically or electrically joined, you need a droop law to allow the engines to load share. In a constant Nr (I think this is what you mean by isynchronous) system with no link between engines, one engine could idle and the other be flat out and both governors would be happy because the Nr was correct.
Back to manoeuvring the Lynx - because of the CAC (computer acceleration control) when 'G' is sensed, it offloads the rotor head by reducing collective pitch (and thus torque) - it is a clumsy system designed to minimse the effect of a cyclic AFCS runaway in pitch.
If you are in a high-speed tactical descent with say 20% Tq (ie power on) and you then flare hard, the 'G' will cause the CAC to reduce pitch and Tq and coupled with the normal flare effects due to the change in the relative airflow presented to the disc (pitch-up, increase in rotor thrust and NR) will suddenly put you in effectively a power off regime which even the cleverest governor in the world can do nothing about. Unless the collective is raised pdq, the Nr will accelerate fast and probably overspeed. We do teach pilots to lead with lever btw but it can still catch people out.
The higher the AuM, the more flare required to arrest the rate of descent and the more 'G' experienced.
The point to note is that, to use your terminology, the boundary between loaded and unloaded head can be crossed very quickly when manoeuvring hard and your clever governors won't cope.
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DM, I am starting to get the same felling about this thread as I do when AW start talking - it is going nowhere unless we agree with you.
Crab is in no way shabby when it comes to the tech and PoF required to prove that the Lynx at 4875 is a handful, T800s are great and are meant to let us actually get airborne in moderate temps (something that is embarrassingly missing at the moment) but will not stop the problem of an old, slow AFCS being re-installed on a modified bathroom thus adding the same bidet characteristics, regardless how you redecorate it. If I add gold wallpaper to the bathroom, increase the overall weight, the Pooh will still go down the pan in the same way!!!! You could narrow the pipe to slow it a bit but it will still go down.
I Think the bathroom analogy is the correct one for the Mk11, and no redecoration is going to make it actually do the job we, the poor, stupid users want or asked for.
Again,
have we been allowed to have castering nose wheels?
Can we have enough room in the front to actually use it (or remove the PSPs if they are the problem)?
How are we going to get the troops out of the places they NEED to be got out from?
All questions that were asked well before the 1st mock up was built and seem to have been re-interpreted.
Crab is in no way shabby when it comes to the tech and PoF required to prove that the Lynx at 4875 is a handful, T800s are great and are meant to let us actually get airborne in moderate temps (something that is embarrassingly missing at the moment) but will not stop the problem of an old, slow AFCS being re-installed on a modified bathroom thus adding the same bidet characteristics, regardless how you redecorate it. If I add gold wallpaper to the bathroom, increase the overall weight, the Pooh will still go down the pan in the same way!!!! You could narrow the pipe to slow it a bit but it will still go down.
I Think the bathroom analogy is the correct one for the Mk11, and no redecoration is going to make it actually do the job we, the poor, stupid users want or asked for.
Again,
have we been allowed to have castering nose wheels?
Can we have enough room in the front to actually use it (or remove the PSPs if they are the problem)?
How are we going to get the troops out of the places they NEED to be got out from?
All questions that were asked well before the 1st mock up was built and seem to have been re-interpreted.
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clarification, thanks
CRAB, thankyou for clarifying with your analogy what you were trying to say in your earlier post. Obviously in the scenario you postulate the supplier has broken the contract agreed on (ie not supplied what was agreed) and you should quite rightly be agrieved (no argument there).
I find it difficult to believe that with MoD contracts this happens without the supplier incurring penalties as legally they will be in breach of the contract (hardly good business sense). It may appear from your position that doesn't happen but I remain to be convinced.
Back to engine control....
Engine governing systems have different 'priorities' when it comes to control. The prime (but not the only) one should be to maintain rotor speed at all times within an agreed tolerance, and if the propulsion system uses more than 1 engine a secondary consideration (for obvious reasons) should be to share the power evenly whilst maintaining adequate rotor control, I believe that is what current mechanical or digital control systems do as well as other clever things like temp and speed limiting.
I have never stated that when 'power off' rotor speed control on the Lynx is anything but challenging and I agree that an increase in AUM can only make things worse in that case, however until that point is reached (ie autorotation is entered) a more modern engine governing system WILL control Nr more tightly and reduce the tendency for the rotor speed to increase as power demand is reduced and may well prevent a split off being achieved.
Thanks for the input from Penny Pincher regarding FADEC control and piloting techniques, his points are well made.
PP: to clarify if the engines are required to supply power at any level they also have the capabilty to throttle that power and control the Nr, newer (Digital) system have a higher reaction time and higher fidelity than legacy systems and that is why the governing laws are tighter. A rotor will slow down any pitch angle otherwise it would require no power at all to get the thing to rotate in the first place (profile and induced drag plus inherent friction within the drive train have to be overcome if nothing else)
I am not saying that rotor control at high AUM will be perfect but it will be better than now and I can only assume that the MAUM number arrived at for the Lynx rotor system with T800s driving it has been modelled and assessed as suitable for service otherwise that AUM would never have been agreed, surely.
GND: The bathroom analogy is a bit harsh in this case, AW (to the best of my knowledge) havent changed the contracted design and then demanded more cash, they are contractually obliged to deliver what was agreed, yes you are right you might not get what YOU want but you will get what was ordered and that won't be AWs fault.
I dont have access to the design deatils but from the CGI pictures it looks like the undercarriage is common between RN and AAc aircraft and I am sure the RN will mandate a castoring nosewheel so you will get one as well.
It is likely we won't see eye to eye on all points in this discussion but where I know things are wrong I will continue to correct them. I wish you well and keep your head down and yourself safe wherever you are.
DM
I find it difficult to believe that with MoD contracts this happens without the supplier incurring penalties as legally they will be in breach of the contract (hardly good business sense). It may appear from your position that doesn't happen but I remain to be convinced.
Back to engine control....
Engine governing systems have different 'priorities' when it comes to control. The prime (but not the only) one should be to maintain rotor speed at all times within an agreed tolerance, and if the propulsion system uses more than 1 engine a secondary consideration (for obvious reasons) should be to share the power evenly whilst maintaining adequate rotor control, I believe that is what current mechanical or digital control systems do as well as other clever things like temp and speed limiting.
I have never stated that when 'power off' rotor speed control on the Lynx is anything but challenging and I agree that an increase in AUM can only make things worse in that case, however until that point is reached (ie autorotation is entered) a more modern engine governing system WILL control Nr more tightly and reduce the tendency for the rotor speed to increase as power demand is reduced and may well prevent a split off being achieved.
Thanks for the input from Penny Pincher regarding FADEC control and piloting techniques, his points are well made.
PP: to clarify if the engines are required to supply power at any level they also have the capabilty to throttle that power and control the Nr, newer (Digital) system have a higher reaction time and higher fidelity than legacy systems and that is why the governing laws are tighter. A rotor will slow down any pitch angle otherwise it would require no power at all to get the thing to rotate in the first place (profile and induced drag plus inherent friction within the drive train have to be overcome if nothing else)
I am not saying that rotor control at high AUM will be perfect but it will be better than now and I can only assume that the MAUM number arrived at for the Lynx rotor system with T800s driving it has been modelled and assessed as suitable for service otherwise that AUM would never have been agreed, surely.
GND: The bathroom analogy is a bit harsh in this case, AW (to the best of my knowledge) havent changed the contracted design and then demanded more cash, they are contractually obliged to deliver what was agreed, yes you are right you might not get what YOU want but you will get what was ordered and that won't be AWs fault.
I dont have access to the design deatils but from the CGI pictures it looks like the undercarriage is common between RN and AAc aircraft and I am sure the RN will mandate a castoring nosewheel so you will get one as well.
It is likely we won't see eye to eye on all points in this discussion but where I know things are wrong I will continue to correct them. I wish you well and keep your head down and yourself safe wherever you are.
DM
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dangermouse, how many hours do you have flying Lynx?
At present, the u/c is common for both. ie- the same as current naval Lynx. The Navy have (or had) no requirement for a castoring nose wheel as they feel there is no need to ground taxi the aircraft. The army failed to clearly specify that they required ground taxiable aircraft although the requirement intimated it. To 'cure' this error, it may be deemed that it is out of contract thus meaning extra cost to stick a castoring nose wheel on (both versions). With this extra cost, it means further capability will be lost as we have to remove something to pay for the change. Even if we do get a ground taxiable aircraft, it is doubtful whether AW will 'clear' the aircraft to anyway as they don't have confidence in being able to record head stress through life. How come we can ground taxi Mk9 Lynx with the same head without this problem?
I dont have access to the design deatils but from the CGI pictures it looks like the undercarriage is common between RN and AAc aircraft and I am sure the RN will mandate a castoring nosewheel so you will get one as well.
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not many....
but I don't need to have to understand control theory.
just for clarity in this part of the discussion, by 'castoring' do we mean powered (like the Merlin) or free castoring? (like the Puma) as the Puma can ground taxi without a powered nosewheel so the Flynx should be able to.
Currently doesnt the RN Lynx have a free castoring nose wheel to allow turns on the deck, same reason as the main wheels can be toed ? nd isnt that analagous to the puma situation, or am I getting my knickers in a twist?
WG13: the 'problem' comes back to (from the users point of view) a poor defintion of the requirement, once more not the suppliers fault, you should get EXACTLY what you asked for, nothing more or less.
Without a detailed involvement in the design and qualification process (which I also dont have) why makes you think a release for a new aircraft with dedicated trails assets isn't achievable, it's pure conjecture (but I suppose this is a 'rumour' network after all)
DM
just for clarity in this part of the discussion, by 'castoring' do we mean powered (like the Merlin) or free castoring? (like the Puma) as the Puma can ground taxi without a powered nosewheel so the Flynx should be able to.
Currently doesnt the RN Lynx have a free castoring nose wheel to allow turns on the deck, same reason as the main wheels can be toed ? nd isnt that analagous to the puma situation, or am I getting my knickers in a twist?
WG13: the 'problem' comes back to (from the users point of view) a poor defintion of the requirement, once more not the suppliers fault, you should get EXACTLY what you asked for, nothing more or less.
Without a detailed involvement in the design and qualification process (which I also dont have) why makes you think a release for a new aircraft with dedicated trails assets isn't achievable, it's pure conjecture (but I suppose this is a 'rumour' network after all)
DM
Last edited by dangermouse; 18th Dec 2008 at 14:46.
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Been flying RN Lynx for a while with over 3000hrs in them. It can get off the deck in 5 minutes with a big gun and a missile and wreak havoc (the Merlin can't). The present airframes need replacing soon and there's nothing better at the job. If the the AAC don't want FLynx then perhaps they can give them to the RN.
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but I don't need to have to understand control theory.
Seeings how you have never flown Lynx, I shall pretty much ignore your 'theories' regarding NR control on that airframe if you don't mind?
just for clarity in this part of the discussion, by 'castoring' do we mean powered (like the Merlin) or free castoring? (like the Puma) as the Puma can ground taxi without a powered nosewheel so the Flynx should be able to.
Currently doesnt the RN Lynx have a free castoring nose wheel to allow turns on the deck, same reason as the main wheels can be toed ? nd isnt that analagous to the puma situation, or am I getting my knickers in a twist?
Look at the position of where the wheels are in relation to the oleo;
WG13: the 'problem' comes back to (from the users point of view) a poor defintion of the requirement, once more not the suppliers fault, you should get EXACTLY what you asked for, nothing more or less.
Without a detailed involvement in the design and qualification process (which I also dont have) why makes you think a release for a new aircraft with dedicated trails assets isn't achievable, it's pure conjecture (but I suppose this is a 'rumour' network after all)
DM
DM
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yes you are right you might not get what YOU want but you will get what was ordered and that won't be AWs fault.
And, if I recall, it was the Westland boys who created the fantastic rear undercarriage for the Mk 9 Lynx - you know, the one with the radius arm design that means you can't land vertically without peeling the tyres from the wheels. Oh no! that must have been the customer's fault as well.
Probably a bit like the Main Rotor Head Vibration Absorber (MRHVA) or 'bonk' as it was christened. This was Westlands genius solution to high vibration levels generated by the rotor - they just happend to have a box load of 'bonks' on the shelf because they had been intended for the WG30 - so they sold them to the AAC and invented a 'tuning procedure' which was only valid for one specific Nr (it varies in flight due to the droop law). The MRHVA reduced next to bugger all vibration and took many kilos of useable AUM - another fantastic Westlands bathroom solution.
DM you clearly don't want to listen to pilots' opinions on the Lynx handling - and you wonder why I thought you worked for AW
Probably a bit like the Main Rotor Head Vibration Absorber (MRHVA) or 'bonk' as it was christened. This was Westlands genius solution to high vibration levels generated by the rotor - they just happend to have a box load of 'bonks' on the shelf because they had been intended for the WG30 - so they sold them to the AAC and invented a 'tuning procedure' which was only valid for one specific Nr (it varies in flight due to the droop law). The MRHVA reduced next to bugger all vibration and took many kilos of useable AUM - another fantastic Westlands bathroom solution.
DM you clearly don't want to listen to pilots' opinions on the Lynx handling - and you wonder why I thought you worked for AW
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DM, you are missing the point somewhat. Again - no-one has a problem with NR control due to the governors not coping. No-one thinks that there is a problem with maintaining a constant NR power on. The point is that due to the rotor design, both head and blades, the NR is extremely challenging when in a low power situation. Not necessarily power off, but low power. This is because the aerodynamic effects of disc loading has more power to increase NR than the governors have to decrease it by backing off the power. It is very easy to get into a low Tq situation where the NR is rising rapidly, and the fanciest governors in the world will not change that. The fact is that to get the aircraft down through a threat band requires a high ROD with manouevering. This means extremely lively NR at a time/altitude when the pilot has lots of other things to focus on. An increase in AUM not only results in exacerbated NR rise, but an earlier onset of disc loading and therefore NR rise. I'm not complaining about it - it is managable if the pilot is competent, current, well trained and aware. But it is hardly progress, and the governors will not help this.
And by the way, just how many advanced autos or tactical descents have you done in a Lynx at 5330Kg?
And by the way, just how many advanced autos or tactical descents have you done in a Lynx at 5330Kg?
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DM - On the point of nosewheel castoring if it is the same as the current Mk3/8 arrangement, it won't be much use to the AAC. It is hydrualically actuated and will only rotate 90 deg to the right to allow the aircraft to pivot around the deck lock harpoon with the mainwheels towed out at 27.5 deg. The wheels don't have brakes either they have locks which are either on or off! Great when you are onboard and want take off into wind and the fish heads can't give you a decent flying course. Not so great for taxying around an airfield! As for NR control, I concur with all the other Lynx pilots on this thread, it can be extremely lively at high AUM in low Tq manoeuvres and no governer will change that. FLynx (Wildcat) will be great for the RN not so sure about the AAC! I only hope that it will be as capable as the current MK8 CMP.
Last edited by Jucky; 18th Dec 2008 at 19:06.