Norways first AW101 on its side
Davigal, thank you for the additional info. But all the issues mentioned, the design challenges with larger helicopters have been successfully addressed with non powered, fully castering nose wheels. The only large US helicopter exception to that statement is the CH-47, and Boeing went to a powered left rear gear in 1964, and not because of size or gross weight, but because of a main rotor design issue: the droop stops were set so tight that taxi pedal inputs larger than 3/4 inch resulted in droop stop contact and in many cases, failure of the droop stop, with embarrassing consequences during the subsequent shutdown sequence.
I’m just being curious, as I’ve been to Yeovil and they are very good, therefore my thinking is that they wouldn’t have wanted to make their system that much more complicated unless there was another consideration in play.
I’m just being curious, as I’ve been to Yeovil and they are very good, therefore my thinking is that they wouldn’t have wanted to make their system that much more complicated unless there was another consideration in play.
Last edited by JohnDixson; 28th Nov 2017 at 21:31. Reason: Correction
I begin to appreciate Mr. Sikorsky and Mr. Boeing's Engineers more and more.
Sometimes simple is in fact better.
The Chinook's power steering system and castering Aft gear could cause enough heart ache but the 101 seems a tad too complex for some reason.
Sometimes simple is in fact better.
The Chinook's power steering system and castering Aft gear could cause enough heart ache but the 101 seems a tad too complex for some reason.
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Cheers
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Nosewheel steering design requirements for 101 (info for SASless)
The NWS system operates the way it does due to the RN requirement for the aircraft to be recovered into a ships hangar with no-one on deck (itself a pretty tough requirement to meet on a frigate in the north atlantic). Based on Lynx experience the RN aircraft is required to have a deck lock (harpoon) at the centre of rotation of the aircraft, that engages into a grid on the deck, the aircraft is then orientated towards the hangar by spinning around the deck lock with the nosegear at 90 degs (castored). The Lynx manages this by having the main gear orientated outboard with a free castoring nosegear, this works fine but the gear orientation has to be carried out by groundcrew and when locked outboard prevents any ground handing (the Lynx was not required move into the hangar independently, the Merlin was). This was deemed unworkable on the 101 given the size of the aircraft and the need to also have the capability to enter the hangar (mainwheels must remain fore/aft) with no one on the deck. Therefore a powered castoring nosegear system was selected. This moves the gear to 90 degs so the aircraft can be orientated correctly to allow the automatic deck handling shuttles to engage the u/c legs to pull the aircraft into the hangar.
Now as you have a powered castoring nosegear it makes sense to use some of the capability to allow ground steering to be carried out, the NWS has 50 degs of movement either side of fore/aft to allow steering during ground taxiing to take place. There are speed limits for using this system and for higher speeds either use of differential main gear braking or the tail rotor can be used to control heading. Obviously disengaging heading hold is a good idea when ground handling, FRCs include the appropriate limits and warnings which have been mentioned previously.
So as the RN aircraft uses that system specifically to meet a basic RN requirement, for commonality across 101 variants they all have it.
The strut change mentioned by davigal is specific to naval variants of the 101 and allows the main gear damping value to be selected from 'soft' to 'hard' to prevent excessive aircraft motion when embarked on ships, it is manually selectable from outside the aircraft and the status is included in the preflight walkaround checks. I suspect that the Norway aircraft not being a naval variant doesn't have this option in any case
In any case I don't think we can imply anything as a cause of the incident as the nosegear is obviously orientated fore/aft in the photos.
The NWS system operates the way it does due to the RN requirement for the aircraft to be recovered into a ships hangar with no-one on deck (itself a pretty tough requirement to meet on a frigate in the north atlantic). Based on Lynx experience the RN aircraft is required to have a deck lock (harpoon) at the centre of rotation of the aircraft, that engages into a grid on the deck, the aircraft is then orientated towards the hangar by spinning around the deck lock with the nosegear at 90 degs (castored). The Lynx manages this by having the main gear orientated outboard with a free castoring nosegear, this works fine but the gear orientation has to be carried out by groundcrew and when locked outboard prevents any ground handing (the Lynx was not required move into the hangar independently, the Merlin was). This was deemed unworkable on the 101 given the size of the aircraft and the need to also have the capability to enter the hangar (mainwheels must remain fore/aft) with no one on the deck. Therefore a powered castoring nosegear system was selected. This moves the gear to 90 degs so the aircraft can be orientated correctly to allow the automatic deck handling shuttles to engage the u/c legs to pull the aircraft into the hangar.
Now as you have a powered castoring nosegear it makes sense to use some of the capability to allow ground steering to be carried out, the NWS has 50 degs of movement either side of fore/aft to allow steering during ground taxiing to take place. There are speed limits for using this system and for higher speeds either use of differential main gear braking or the tail rotor can be used to control heading. Obviously disengaging heading hold is a good idea when ground handling, FRCs include the appropriate limits and warnings which have been mentioned previously.
So as the RN aircraft uses that system specifically to meet a basic RN requirement, for commonality across 101 variants they all have it.
The strut change mentioned by davigal is specific to naval variants of the 101 and allows the main gear damping value to be selected from 'soft' to 'hard' to prevent excessive aircraft motion when embarked on ships, it is manually selectable from outside the aircraft and the status is included in the preflight walkaround checks. I suspect that the Norway aircraft not being a naval variant doesn't have this option in any case
In any case I don't think we can imply anything as a cause of the incident as the nosegear is obviously orientated fore/aft in the photos.
Last edited by dangermouse; 29th Nov 2017 at 07:44. Reason: additional info
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For ground taxying the AW101, we recommend that the non-handling pilot puts his or her feet firmly on the inner section of the yaw pedals to resist any unwanted input from the handling pilot. This also breaks the yaw channel microswitches so, even if the AP is still engaged, the heading-hold will not affect the pedal position.
Ground handling accidents are not the sole preserve of the AW101!
Ground handling accidents are not the sole preserve of the AW101!
Thanks for the design info DM. In some other forum it would be informative to read the RN’s views on the Lynx system vs the Canadian haul down for frigate recovery ops.
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I think the RN view is that until you are actually firmly on the deck it is better to not be attached to the ship at all!!
Surely an issue with the haul down is getting the aircraft to connect to the ship whilst hovering (how is that done?), I guess that needs a team on the deck, the RN view is probably that (certainly for Merlin) the deck is unmanned, which given the sea states required to operate in, is safer than having people on a wet moving deck.
Both Merlin and Lynx/Wildcat have significant subminimum pitch available to stick the aircraft on the deck until the harpoon engages (which takes a few seconds at most) only when secured by that are the engines shutdown and either the aircraft moved into the hangar or lashed down.
Surely an issue with the haul down is getting the aircraft to connect to the ship whilst hovering (how is that done?), I guess that needs a team on the deck, the RN view is probably that (certainly for Merlin) the deck is unmanned, which given the sea states required to operate in, is safer than having people on a wet moving deck.
Both Merlin and Lynx/Wildcat have significant subminimum pitch available to stick the aircraft on the deck until the harpoon engages (which takes a few seconds at most) only when secured by that are the engines shutdown and either the aircraft moved into the hangar or lashed down.
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Customer: 'Ello, I wish to register a complaint.
(The owner does not respond.)
C: 'Ello, Miss?
Owner: What do you mean "miss"?
C: I'm sorry, I have a cold. I wish to make a complaint!
O: We're closin' for lunch.
C: Never mind that, my lad. I wish to complain about this chopper what I purchased not half an hour ago from this very boutique.
O: Oh yes, the, uh, the Norwegian Blue...What's,uh...What's wrong with it?
C: I'll tell you what's wrong with it, my lad. 'E's dead, that's what's wrong with it!
O: No, no, 'e's uh,...he's resting.
C: Look, matey, I know a dead chopper when I see one, and I'm looking at one right now.
O: No no he's not dead, he's, he's restin'! Remarkable bird, the Norwegian Blue, idn'it, ay? Beautiful plumage!
C: The plumage don't enter into it. It's stone dead.
O: Nononono, no, no! 'E's resting!
C: All right then, if he's restin', I'll wake him up!
(shouting at the cage)
'Ello, Mister Polly Parrot! I've got a lovely fresh cuttle fish for you if you show...(owner hits the cage)
O: There, he moved!
C: No, he didn't, that was you hitting the cage!
O: I never!!
C: Yes, you did!
O: I never, never did anything...
C: (yelling and hitting the cage repeatedly) 'ELLO POLLY!!!!!
Testing! Testing! Testing! Testing! This is your nine o'clock alarm call!
(Takes parrot out of the cage and thumps its head on the counter. Throws it up in the air and watches it plummet to the floor.)
C: Now that's what I call a dead parrot.
O: No, no.....No, 'e's stunned!
C: STUNNED?!?
O: Yeah! You stunned him, just as he was wakin' up! Norwegian Blues stun easily, major.
C: Um...now look...now look, mate, I've definitely 'ad enough of this. That parrot is definitely deceased, and when I purchased it not 'alf an hour ago, you assured me that its total lack of movement was due to it bein' tired and shagged out following a prolonged squawk.
O: Well, he's...he's, ah...probably pining for the fjords.
C: PININ' for the FJORDS?!?!?!? What kind of talk is that?, look, why did he fall flat on his back the moment I got 'im home?
O: The Norwegian Blue prefers kippin' on it's back! Remarkable bird, id'nit, squire? Lovely plumage!
C: Look, I took the liberty of examining that parrot when I got it home, and I discovered the only reason that it had been sitting on its perch in the first place was that it had been NAILED there.
(pause)
O: Well, o'course it was nailed there! If I hadn't nailed that bird down, it would have nuzzled up to those bars, bent 'em apart with its beak, and VOOM! Feeweeweewee!
C: "VOOM"?!? Mate, this bird wouldn't "voom" if you put four million volts through it! 'E's bleedin' demised!
O: No no! 'E's pining!
C: 'E's not pinin'! 'E's passed on! This chopper is no more! He has ceased to be! 'E's expired and gone to meet 'is maker!
'E's a stiff! Bereft of life, 'e rests in peace! If you hadn't nailed 'im to the perch 'e'd be pushing up the daisies!
'Is metabolic processes are now 'istory! 'E's off the twig!
'E's kicked the bucket, 'e's shuffled off 'is mortal coil, run down the curtain and joined the bleedin' choir invisibile!!
THIS IS AN EX-CHOPPER!!
(The owner does not respond.)
C: 'Ello, Miss?
Owner: What do you mean "miss"?
C: I'm sorry, I have a cold. I wish to make a complaint!
O: We're closin' for lunch.
C: Never mind that, my lad. I wish to complain about this chopper what I purchased not half an hour ago from this very boutique.
O: Oh yes, the, uh, the Norwegian Blue...What's,uh...What's wrong with it?
C: I'll tell you what's wrong with it, my lad. 'E's dead, that's what's wrong with it!
O: No, no, 'e's uh,...he's resting.
C: Look, matey, I know a dead chopper when I see one, and I'm looking at one right now.
O: No no he's not dead, he's, he's restin'! Remarkable bird, the Norwegian Blue, idn'it, ay? Beautiful plumage!
C: The plumage don't enter into it. It's stone dead.
O: Nononono, no, no! 'E's resting!
C: All right then, if he's restin', I'll wake him up!
(shouting at the cage)
'Ello, Mister Polly Parrot! I've got a lovely fresh cuttle fish for you if you show...(owner hits the cage)
O: There, he moved!
C: No, he didn't, that was you hitting the cage!
O: I never!!
C: Yes, you did!
O: I never, never did anything...
C: (yelling and hitting the cage repeatedly) 'ELLO POLLY!!!!!
Testing! Testing! Testing! Testing! This is your nine o'clock alarm call!
(Takes parrot out of the cage and thumps its head on the counter. Throws it up in the air and watches it plummet to the floor.)
C: Now that's what I call a dead parrot.
O: No, no.....No, 'e's stunned!
C: STUNNED?!?
O: Yeah! You stunned him, just as he was wakin' up! Norwegian Blues stun easily, major.
C: Um...now look...now look, mate, I've definitely 'ad enough of this. That parrot is definitely deceased, and when I purchased it not 'alf an hour ago, you assured me that its total lack of movement was due to it bein' tired and shagged out following a prolonged squawk.
O: Well, he's...he's, ah...probably pining for the fjords.
C: PININ' for the FJORDS?!?!?!? What kind of talk is that?, look, why did he fall flat on his back the moment I got 'im home?
O: The Norwegian Blue prefers kippin' on it's back! Remarkable bird, id'nit, squire? Lovely plumage!
C: Look, I took the liberty of examining that parrot when I got it home, and I discovered the only reason that it had been sitting on its perch in the first place was that it had been NAILED there.
(pause)
O: Well, o'course it was nailed there! If I hadn't nailed that bird down, it would have nuzzled up to those bars, bent 'em apart with its beak, and VOOM! Feeweeweewee!
C: "VOOM"?!? Mate, this bird wouldn't "voom" if you put four million volts through it! 'E's bleedin' demised!
O: No no! 'E's pining!
C: 'E's not pinin'! 'E's passed on! This chopper is no more! He has ceased to be! 'E's expired and gone to meet 'is maker!
'E's a stiff! Bereft of life, 'e rests in peace! If you hadn't nailed 'im to the perch 'e'd be pushing up the daisies!
'Is metabolic processes are now 'istory! 'E's off the twig!
'E's kicked the bucket, 'e's shuffled off 'is mortal coil, run down the curtain and joined the bleedin' choir invisibile!!
THIS IS AN EX-CHOPPER!!
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How would such a system work? If I were taking off from the deck of a small ship at night (or any time actually) I would want to be assured that the AP was fully engaged prior to lifting. A WOW switch would prevent that, unless it had some kind of override - which would compromise any protection. The AW101 does indeed have a WOW override - but as far as I know it's not routinely used.
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How would such a system work? If I were taking off from the deck of a small ship at night (or any time actually) I would want to be assured that the AP was fully engaged prior to lifting. A WOW switch would prevent that, unless it had some kind of override - which would compromise any protection. The AW101 does indeed have a WOW override - but as far as I know it's not routinely used.
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The AP on the AW101 is 100% authority attitude and heading hold system. It isn't SAS. It does have a manual trim mode which is similar to SAS, but it's not routinely used because it deprives the pilot of AFCS modes (IAS, BAR, RAD holds etc).
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Xmit, are you referring to the SEP20 or the AWAC200?
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. The Norway AW101 uses the later AFCS, which determines if it is on ground.To my knowledge the SEP20 provides stability augmentation through the fast acting but limited authority series actuators, responding to dynamic disturbances. Only the parallel actuators, for AP, have full authority.
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That's correct, but with ASE only engaged (ie no AFCS modes) the parallel actuators still operate and extend ASE authority to 100%. Although slow compared with the series actuators, they are certainly fast enough to give problems on the ground if the ASE is malfunctioning or misused.
Maybe this isn't the case with the new system. The SEP20 has a manual trim mode which takes out the parallel actuators but, as far as I know, it's never used except during initial flying control demo sorties.
Maybe this isn't the case with the new system. The SEP20 has a manual trim mode which takes out the parallel actuators but, as far as I know, it's never used except during initial flying control demo sorties.
But the parallel actuators need to move the controls in order to get into an open-loop condition and extend the authority of the series actuators, this should be noticed by the pilot.
To create a demand that would cause the parallel actuators to move, an input from a sensor would be required or a demand from a pilot input (using the beeper trim for example).
To create a demand that would cause the parallel actuators to move, an input from a sensor would be required or a demand from a pilot input (using the beeper trim for example).
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Originally Posted by [email protected]
But the parallel actuators need to move the controls in order to get into an open-loop condition and extend the authority of the series actuators, this should be noticed by the pilot.
To create a demand that would cause the parallel actuators to move, an input from a sensor would be required or a demand from a pilot input (using the beeper trim for example).
To create a demand that would cause the parallel actuators to move, an input from a sensor would be required or a demand from a pilot input (using the beeper trim for example).
Sometimes pilots don't physically monitor the controls, especially on the ground, and insidious movement, pehaps caused by a sticky trim switch or malfunctioning parallel actuator, might catch the unwary.
It's also worth saying that AFCS issues on the ground aren't confined to the AW101!
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Pants on Fire
The Norwegian Blue!
Thanks a lot!
I almost lost my medical.
Thanks to You and John Cleese!
I was sitting peacefully having breakfast at a hotel restaurant when checking the latest on this thread.
Hysteric laughter and heaving for air, when reading Your post!
The local CAA was just ca 100 meters away and I think another crew was considering contacting them ......
I recovered , and agreed with myself never to read pPrune in a public place anymore.
Thanks, You made my day.
Cpt B
Thanks a lot!
I almost lost my medical.
Thanks to You and John Cleese!
I was sitting peacefully having breakfast at a hotel restaurant when checking the latest on this thread.
Hysteric laughter and heaving for air, when reading Your post!
The local CAA was just ca 100 meters away and I think another crew was considering contacting them ......
I recovered , and agreed with myself never to read pPrune in a public place anymore.
Thanks, You made my day.
Cpt B