Chinook & other tandem rotors discussions
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Slow day at the office SS?
I was attempting to keep it simple mate.
If you wish to have a limitations quiz, give me a shout and I'll send one over.
(I'll make sure you get above 60% this time (30% real time)) 
It is but we work out single eng perf based on PPI not gearbox.
Tell the rest of the bonk tuning criteria then?? C'mon, you'll not get away that easily!
I was attempting to keep it simple mate.
If you wish to have a limitations quiz, give me a shout and I'll send one over.
(I'll make sure you get above 60% this time (30% real time))
It's a powerful engine the Gem!
Tell the rest of the bonk tuning criteria then?? C'mon, you'll not get away that easily!
Purveyor of Egg Liqueur to Lucifer
Slow day at the office SS?
memo to self: must remember passwords for tax return, then I won't be drawn towards PPRuNe !
As for the quiz, if you can get one here for Friday in time for my OPC that would be great. It would be the correct type I trust!?
Thanks for the results, I didn't know back then that they were that low! With 'Above Average' gradings back then, I wonder what I would get if I scored higher in the MPQ!
By the way, I never got the last question on each MPQ paper corect.
What 'was' the telephone number for Aviation Standards at M.Wallop? I do hope the questions are more relevant these days!
we work out single eng perf based on PPI not gearbox.
SS
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Papers in the post
Forgotten how and why we do a PPI already, Sid??
You've still not furnished me with the rest of the bonk setting criteria
QHI's.....c*"ts the lot of 'em!
But surely that is still a transmission torque limitation!!!
You've still not furnished me with the rest of the bonk setting criteria
QHI's.....c*"ts the lot of 'em!
wg13,
Cu*ts are useful and pleasant to be around, aren't they?
Sid,
What's a tax return?!
Cu*ts are useful and pleasant to be around, aren't they?
Sid,
What's a tax return?!
Purveyor of Egg Liqueur to Lucifer
It seems then wg, that my memory is fading faster than a cat can lick it a$$!!
When working out the single engine performance figures, I always used to refer to the charts in the back of the ODM. The figures were based on Temp/Press/Wt. At no time did I go to the BATs office and get the latest PPI figures.
These days, we do a PAC (Power Assurance Check) daily, and still when working out the figures for Cat A Ops, do not go and check the daily PAC sheets. The Performance data charts still only needs a combination of Temp/Press/Weight to give me the required values.
Perhaps it is you that doesn't know why you do a PPI in the first place!
SS
Thud,
Time for you to come home, the Sun must be getting to you!!
SS
When working out the single engine performance figures, I always used to refer to the charts in the back of the ODM. The figures were based on Temp/Press/Wt. At no time did I go to the BATs office and get the latest PPI figures.
These days, we do a PAC (Power Assurance Check) daily, and still when working out the figures for Cat A Ops, do not go and check the daily PAC sheets. The Performance data charts still only needs a combination of Temp/Press/Weight to give me the required values.
Perhaps it is you that doesn't know why you do a PPI in the first place!
SS
Thud,
Time for you to come home, the Sun must be getting to you!!
SS
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Power Assurance Check
So you wouldnt use the PPI figures from the 700 to establish where to start on the graphs then? Remember all the different graphs relating to 96% PPI (clean etc), 98% PPI (Clean etc), 100% PPI (blah...).
At no time did I go to the BATs office and get the latest PPI figures.
Surely the performace of the engine (well, since its last PPI) is quite relevent to what we could expect the engine to produce should the other donk stop?
(........1013 set, S+L, CAC out, friction on, ECL brief, 1 back to check 2, pull to 100 %, allow to settle, read OAT, Alt, NR, TQ, T6, NH....blah..... See if its T6, NH or NR droop limited?? REMES calculate to give the errr Power Performance Index so that we can calculate the errr Sin Eng Perf!!) Jog any memories, Sid?
My, you have been away too long!
When working out the single engine performance figures, I always used to refer to the charts in the back of the ODM. The figures were based on Temp/Press/Wt. At no time did I go to the BATs office and get the latest PPI figures.
Purveyor of Egg Liqueur to Lucifer
Hmmm...shouldn't that have been done by the end of September?
And that gives you the limitation for the gearbox??
Running parrallel on this thread, Torque limitations are based on the transmission are they not? An engine can easily overtorque a transmission.
I guess when I said, "At no time did I go to the BATs office and get the latest PPI figures" I must have been thinking about that cat licking its a$$. OK, wrong again, sorry!
Now was that anti-icing and cabin heating off or not? What if I have anti-icing off and cabin heating on? AFCS Height hold disengaged or not?
Anyway, I still stand by "When working out the single engine performance figures, I always used to refer to the charts in the back of the ODM. The figures were based on Temp/Press/Wt." But must add, the chart used was decided by the PPI results found in the 700. But isn't that just for finding MinSELF?
Do/Did you feel safe in an aircraft giving you 94% PPI?
'Above average' eh?
You never did make PSI did you? Only now by default!
SS
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Apology accepted.
I guess its a similar thing for most twin engined helis. But with the Lynx it goes for the most current figure as opposed to what the manufacturer spec says it should be? Is the PAC figure a fixed book figure?
Yes quite true. Thats why we have a TQ guage. TQ limitations are set in stone. But with a low PPI engine or a 'bad performance day' there is no guarentee that the TQ limit will be reached before the MSELF. Hot & High it will more than likely be the T6 or even the NH.
Think youve answered your own question.
More than.
As to your last question......YES! Cheeky git!
No, the PAC is a means for the pilot to determine, prior to take off, that each engine is capable of developing specification power!!
Running parrallel on this thread, Torque limitations are based on the transmission are they not? An engine can easily overtorque a transmission.
When working out the single engine performance figures
But isn't that just for finding MinSELF?
Do/Did you feel safe in an aircraft giving you 94% PPI?
As to your last question......YES! Cheeky git!
Purveyor of Egg Liqueur to Lucifer
One of those weeks, just trying to get the 3rd thing to go wrong, in order to reset everything.
(This thread seems to have done the trick!)
Thanks for the help________wg
SS________
Opening up to contradiction on different types here, but I think that the PAC way keeps everything 'tidy'. As mentioned before, the PAC ensures that the engines are capable of developing specification power, if they are producing within spec then all is well. It is a check afterall, as opposed to an index figure.
The check is a monitor for power trends and should a trend develop, indicating power loss, then it is investigated further from that point. Rather than having lots of starting pages (moving posts!!), ie 104%, 100%, 94% anti ice & cabin heating on or off, sand filters fitted, etc.
Wouldn't it be easier in the Lynx to work off one set of charts, lets say the 94% figure, and if you have 104% or 100% PPI, bonus! ?
How about also a system where should an engine fail, the cabin heating (and air conditioning!) automatically switches off in order to utilise maximum power from the remaining engine, with an override for use when back in a safe OEI condition?
Maybe on FLynx!!!
SS exits stage left ________________________
(This thread seems to have done the trick!)
Thanks for the help________wg
SS________
Is the PAC figure a fixed book figure?
The check is a monitor for power trends and should a trend develop, indicating power loss, then it is investigated further from that point. Rather than having lots of starting pages (moving posts!!), ie 104%, 100%, 94% anti ice & cabin heating on or off, sand filters fitted, etc.
Wouldn't it be easier in the Lynx to work off one set of charts, lets say the 94% figure, and if you have 104% or 100% PPI, bonus! ?
How about also a system where should an engine fail, the cabin heating (and air conditioning!) automatically switches off in order to utilise maximum power from the remaining engine, with an override for use when back in a safe OEI condition?
Maybe on FLynx!!!
SS exits stage left ________________________
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How about also a system where should an engine fail, the cabin heating (and air conditioning!) automatically switches off in order to utilise maximum power from the remaining engine, with an override for use when back in a safe OEI condition?
There are even more graphs in the back now, Sid. I think the reason why there is so many is firstly, we operate in slightly more varied environments than was the case 15 or so years ago. I'm talking hot.
And secondly, if we just went for the lowest, it may take away a potential landing site when in fact it could be made. Ie. Taking the lowest PPI, 94%, we may come up with a MSELF of 50 knots (not impossible in some theatres). Having a MSELF as high as that would also give us quite a high run on speed (prob over 30kts). This may push us into a decision to go elsewhere if we didnt have a suitable length or surface of area to run on to. You may think 'well, thats working well on the safe side'. True it is but the greater array of figures and calcs means that we can more accuratly get a realistic figure. Ie, more flexibility.I'm guessing in the civy side, the PAC gives you a greater safety margin hence it being a set figure?
Maybe on FLynx, I'll let you know.
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First stage control mixing
Hi,
I was wondering if anyone here could answer this, or at least refer me to someone who can...
The thing is, for my M.Sc. graduation project I'm trying to implement the Chinook CH-47D AFCS in a Matlab/Simulink computational environment, and currently I'm stuck on the inner workings of the first stage mixing unit.
Apparently, the AFCS pitch control laws have 2 output commands, one to the pitch SAS servo and one to the DASH (differential airspeed hold) servo. These two are accumulated with the pilot control inputs and the other control law outputs (both through the ILCAs) in the first stage mixing unit. This results in two outputs: lateral cyclic and collective pitch (something related to this has been discussed earlier in this thread I believe
). My question: what are the mixing equations? I have been able to find some data on the mixing equations of the pilot controls only (from stick input to rotor angle output), but these are unaffected by the DASH and SAS controllers, so there must be a separate set of equations for the first stage mixing.
I don't have a training manual, and I don't know who else I should contact to ask this crazy stuff
I was wondering if anyone here could answer this, or at least refer me to someone who can...
The thing is, for my M.Sc. graduation project I'm trying to implement the Chinook CH-47D AFCS in a Matlab/Simulink computational environment, and currently I'm stuck on the inner workings of the first stage mixing unit.
Apparently, the AFCS pitch control laws have 2 output commands, one to the pitch SAS servo and one to the DASH (differential airspeed hold) servo. These two are accumulated with the pilot control inputs and the other control law outputs (both through the ILCAs) in the first stage mixing unit. This results in two outputs: lateral cyclic and collective pitch (something related to this has been discussed earlier in this thread I believe
). My question: what are the mixing equations? I have been able to find some data on the mixing equations of the pilot controls only (from stick input to rotor angle output), but these are unaffected by the DASH and SAS controllers, so there must be a separate set of equations for the first stage mixing. I don't have a training manual, and I don't know who else I should contact to ask this crazy stuff
All this talk of Chinooks..now who can recall the Belvedere...the original aircraft could be flown manual...didn't even had assisted controls 'though they came before ie entered service.Four bladed rotors too and this was the late 1950s !
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Re: Did you know of this Chinook?
I'd say that was one of the Tilt Rotor Platform Test Heli's doing the 'Wing Thing'
Wild looking. Check the static droop of the forward hub rear blade.....wouldn't want any gusting!!!!!
Wild looking. Check the static droop of the forward hub rear blade.....wouldn't want any gusting!!!!!
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Re: Did you know of this Chinook?
HPB,
The use of a tiltable wing allows the high-speed rotor off-loading benefits of a wing to be enjoyed without the traditional loss-of-lift drawback of such configurations (as encountered by the Mi-6). As always, though, the rotorcraft gods demand that a price be paid, in this case chiefly the added weight & complexity (plus in the case of the 347 the reduced rotor-fuselage interface which you've highlighted).
The 347 has dubious distinction of out-living the HLH at Ft. Rucker's museum, and the type's four-blade rotor has long been touted as a feature of the next-generation CH-47X.
I/C
The use of a tiltable wing allows the high-speed rotor off-loading benefits of a wing to be enjoyed without the traditional loss-of-lift drawback of such configurations (as encountered by the Mi-6). As always, though, the rotorcraft gods demand that a price be paid, in this case chiefly the added weight & complexity (plus in the case of the 347 the reduced rotor-fuselage interface which you've highlighted).
The 347 has dubious distinction of out-living the HLH at Ft. Rucker's museum, and the type's four-blade rotor has long been touted as a feature of the next-generation CH-47X.
I/C
Re: Did you know of this Chinook?
I bet it stops really quickly with airbrakes like that!
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