Why nosewheel tiller?
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Ok then, 411A, do early 707s have artificial feel units on the rudder pedals, or simply rely on aerodynamic control surface feedback? I am aware that they have hydraulic rudder boost, but aren' the rudder pedals also mechanically connected to the rudder on 707s?
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411A
Thanks for the correction re series/parallel Y/D. Oops, its been a while....
BIK etc
The glib answer re Saab Y/D off for t/o and ldg is "because the AFM says so". As I understand it, the Y/D is off close to the ground because it inputs rudder in the event of an engine failure - you can see the potential failure modes!!!!
About the B707 rudder feel, on the -300 there was a "Q bellows" in the fin to adjust the feel for airspeed. The -100 was simply a dog's breakfast in the rudder - the JT3C powered series had no power rudder, but with the JT3D fan series, power rudder was a must (12,000lb vs 18,000lb thrust). How this was achieved depended on degrees of rudder displacement and varied from no power to full power. All I can remember was that it was a bloody nightmare to rig. I'm fairly sure that the B707-300 had artificial feel on the rudder. The rest of the system is for another thread I think!! It's been a hell of a long time since I was an airframe LAME on the B707.
Thanks for the correction re series/parallel Y/D. Oops, its been a while....
BIK etc
The glib answer re Saab Y/D off for t/o and ldg is "because the AFM says so". As I understand it, the Y/D is off close to the ground because it inputs rudder in the event of an engine failure - you can see the potential failure modes!!!!
About the B707 rudder feel, on the -300 there was a "Q bellows" in the fin to adjust the feel for airspeed. The -100 was simply a dog's breakfast in the rudder - the JT3C powered series had no power rudder, but with the JT3D fan series, power rudder was a must (12,000lb vs 18,000lb thrust). How this was achieved depended on degrees of rudder displacement and varied from no power to full power. All I can remember was that it was a bloody nightmare to rig. I'm fairly sure that the B707-300 had artificial feel on the rudder. The rest of the system is for another thread I think!! It's been a hell of a long time since I was an airframe LAME on the B707.
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BIK_116.80
Mustafagander has it right on the money. Q bellows provided artificial feel and yes, the rudder was connected by bellcranks and cables as well. Once rigged correctly, it gave little trouble. If however, the rudder boost was switched OFF during a three engine go-around, the aircraft required LOTS of airspeed. Vmca (boost ON)= 120 knots, boost OFF= 180 knots. The rudder boost was switched OFF on just such a maneuver during a TWA training flight years ago by an FAA inspector in the obs seat and the aircraft rolled over on its back and crashed, killing everyone. After the investigation, the FAA bought TWA a brand NEW 707. The 707 also had a system for aileron assist using aerodynamic balance panels. Wonderful old bird, it was a delight to fly, especially the later -320B advanced models.
Mustafagander has it right on the money. Q bellows provided artificial feel and yes, the rudder was connected by bellcranks and cables as well. Once rigged correctly, it gave little trouble. If however, the rudder boost was switched OFF during a three engine go-around, the aircraft required LOTS of airspeed. Vmca (boost ON)= 120 knots, boost OFF= 180 knots. The rudder boost was switched OFF on just such a maneuver during a TWA training flight years ago by an FAA inspector in the obs seat and the aircraft rolled over on its back and crashed, killing everyone. After the investigation, the FAA bought TWA a brand NEW 707. The 707 also had a system for aileron assist using aerodynamic balance panels. Wonderful old bird, it was a delight to fly, especially the later -320B advanced models.
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PM-
Most all jets flying today have limited nosewheel steering controlled by rudder pedal inputs.
The tiller has much more "turning" authority than the rudder pedals. It should be used only for taxiing, and shouldn't be used for takeoff or landing.
Most all jets flying today have limited nosewheel steering controlled by rudder pedal inputs.
The tiller has much more "turning" authority than the rudder pedals. It should be used only for taxiing, and shouldn't be used for takeoff or landing.
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I know you guys do Big planes, and I hope I will in a very short time from now.
Let me tell you something about the Lears
I´m sure most of you know that they have a little button called steer.
This button basically increases and decreases the amount of degrees the nosewheel moves each side. On takeoff you hold it pressed until you reach 60kt at that speed you release it for 2 reasons.
1) Because now the rudder has enough authority to control the plane directionally and
2) Because if you keep it depressed chances are you´ll lose directional control out of the rwy.
I´ve seen 747 captains use it after touchdown, but very cautiously. I´ve seen 757 pilots using assymetrical thurst to control the plane better. That guy was an ex-C130, that might be the reason, though.
Be safe !! Hands On from TOD PLEASE !!!!
SW.
Let me tell you something about the Lears
I´m sure most of you know that they have a little button called steer.
This button basically increases and decreases the amount of degrees the nosewheel moves each side. On takeoff you hold it pressed until you reach 60kt at that speed you release it for 2 reasons.
1) Because now the rudder has enough authority to control the plane directionally and
2) Because if you keep it depressed chances are you´ll lose directional control out of the rwy.
I´ve seen 747 captains use it after touchdown, but very cautiously. I´ve seen 757 pilots using assymetrical thurst to control the plane better. That guy was an ex-C130, that might be the reason, though.
Be safe !! Hands On from TOD PLEASE !!!!
SW.
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Gawd theres some knowledge out there in pprune land. Thanks for the info guys.
But it still sounds to me like my original proposition stands. That "Yaw damper rudder inputs are not an input to the rudder artificial feel units on any aircraft I know about."
So early 707s had yaw dampers in parallel with the rudder pedals - but there was no artificial feel unit since the rudder controls were entirely a manual affair. You say that more recent 707s had a Q-feel unit on the rudder pedals, but was the yaw damper in parallel on these models? Or was it in series?
So the Saab requires the yaw damper to be switched off for take-off and landing - still hasn't got me convinced that its anything to do with yaw damper inputs to an artificial feel unit. (Does the Saab have a powered rudder?? Does the Saab have an artificial feel unit for the rudder pedals??)
So I am still unable to agree with V2Climb's proposition that "Some aircraft take of with the yaw damper in all the way from the start of the roll. Some other means of steering is needed ie: a nosewheel tiller.(BAE 146 for example)"
And, 411A, thanks for the interesting story about the Feds screw up at TWA. I spose you are well aware of the RAAF (Royal Australian Air Force) B707 training crash off the south east coast of Australia about 10 or 12 years ago when the officer in charge (who was sitting on the jump seat) decided to switch off the rudder boost while two engines on the same side were shut down, and while the aircraft was at 5,000 feet over the ocean? The aircraft rolled over and went into the water with a hell of a thud in well under 30 seconds. May all five crew members on board RIP.
But it still sounds to me like my original proposition stands. That "Yaw damper rudder inputs are not an input to the rudder artificial feel units on any aircraft I know about."
So early 707s had yaw dampers in parallel with the rudder pedals - but there was no artificial feel unit since the rudder controls were entirely a manual affair. You say that more recent 707s had a Q-feel unit on the rudder pedals, but was the yaw damper in parallel on these models? Or was it in series?
So the Saab requires the yaw damper to be switched off for take-off and landing - still hasn't got me convinced that its anything to do with yaw damper inputs to an artificial feel unit. (Does the Saab have a powered rudder?? Does the Saab have an artificial feel unit for the rudder pedals??)
So I am still unable to agree with V2Climb's proposition that "Some aircraft take of with the yaw damper in all the way from the start of the roll. Some other means of steering is needed ie: a nosewheel tiller.(BAE 146 for example)"
And, 411A, thanks for the interesting story about the Feds screw up at TWA. I spose you are well aware of the RAAF (Royal Australian Air Force) B707 training crash off the south east coast of Australia about 10 or 12 years ago when the officer in charge (who was sitting on the jump seat) decided to switch off the rudder boost while two engines on the same side were shut down, and while the aircraft was at 5,000 feet over the ocean? The aircraft rolled over and went into the water with a hell of a thud in well under 30 seconds. May all five crew members on board RIP.
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BIK_116.80
All B707's had yaw dampers and especially the early models were quite unstable in the yaw axis. Earlier models had parallel units, later had series.
Had not heard about the RAAF accident. Nasty business, it has always ammazed me why someone would purposely switch OFF an esential system, especially rudder boost on the 707.
With two engines out on one side, the B707
Vmca (boost ON) 170 knots, (boost OFF) 235 knots. This is for the -320B advanced series.
All B707's had yaw dampers and especially the early models were quite unstable in the yaw axis. Earlier models had parallel units, later had series.
Had not heard about the RAAF accident. Nasty business, it has always ammazed me why someone would purposely switch OFF an esential system, especially rudder boost on the 707.
With two engines out on one side, the B707
Vmca (boost ON) 170 knots, (boost OFF) 235 knots. This is for the -320B advanced series.
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So the early 707s had no artificial feel unit (no powered rudder) but the rudder pedals moved with the parallel yaw damper.
And the more recent 707s had a Q-feel system, but the yaw damper was in series and so the rudder pedals did not move with the yaw damper.
So again, I think my proposition that, "Yaw damper rudder inputs are not an input to the rudder artificial feel units on any aircraft I know about." stands.
The RAAF OIC was trying to give the trainees a challenging scenario to deal with for training purposes. I guess he succeeded in that regard, but the trainees never got the chance to use their new found knowledge.
It is interesting that in both the RAAF and the TWA accidents it seems that the OIC and the FAA PIC were on the jump seat and therefore had no way of either :
(1) Knowing what control inputs and with what force were being applied to the rudder pedals; or,
(2) Making their own rudder pedal inputs to correct the rapidly deteriorating situation (and therefore quickly realising that it was not able to be sorted out), but rather were only able to shout words of encouragement from the jump seat.
It also seems that in both cases no crew member chose to switch the rudder boost back on when they realised that things were not going according to plan. Interesting CRM lesson about assertiveness and mindset perhaps?
But oh what a terrible waste all round.
And the more recent 707s had a Q-feel system, but the yaw damper was in series and so the rudder pedals did not move with the yaw damper.
So again, I think my proposition that, "Yaw damper rudder inputs are not an input to the rudder artificial feel units on any aircraft I know about." stands.
The RAAF OIC was trying to give the trainees a challenging scenario to deal with for training purposes. I guess he succeeded in that regard, but the trainees never got the chance to use their new found knowledge.
It is interesting that in both the RAAF and the TWA accidents it seems that the OIC and the FAA PIC were on the jump seat and therefore had no way of either :
(1) Knowing what control inputs and with what force were being applied to the rudder pedals; or,
(2) Making their own rudder pedal inputs to correct the rapidly deteriorating situation (and therefore quickly realising that it was not able to be sorted out), but rather were only able to shout words of encouragement from the jump seat.
It also seems that in both cases no crew member chose to switch the rudder boost back on when they realised that things were not going according to plan. Interesting CRM lesson about assertiveness and mindset perhaps?
But oh what a terrible waste all round.
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Yes, very sad indeed. It is interesting to note that an FAA inspector on a line or training surveillce flight have NO authority to touch any switch or control. Many years ago (on a DC3 would you believe) I left an inspector in StThomas due to his inability to keep his hands to himself. I complained to the ACDO supervising inspector and this misfit was later transferred.
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With this question on rudder/tiller control of the aircraft is as all the others as far as I am concerned, ie. the less automatics we have in the control of the the aircraft, the better I will like it, manual is much better, and also much, much more reliable!!
