Control Wheel Steering
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Some versions of the 747-200 had CWS instead of the "Manual" autopilot mode. I've tried it a few times, but don't like it at all. I can trim it manually better with the autopilot off, and not get the undesirable feedback from the yoke when I try to turn.
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Now, careful with CWS chaps...
In the Boeing, it takes away some workload, and thus reduces arousal. So, you're climbing or descending to cleared level, in CWS. As you approach the cleared level, you'll get all the usual indications (800ft to level chime/'c' chord) and light, but the aircraft will sail through the level unless you do something.
In the Boeing, it takes away some workload, and thus reduces arousal. So, you're climbing or descending to cleared level, in CWS. As you approach the cleared level, you'll get all the usual indications (800ft to level chime/'c' chord) and light, but the aircraft will sail through the level unless you do something.
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Lockheed L-1011 TriStar Horizontal Stabilizer
There is something about the L-1011 horizontal stabilizer that makes it unique: In the early design stages, the airlines told Lockheed they wanted the pilots to have more power and control over the pitch system, so that in case of a jet upset, the crew could pull the aircraft out of a dive.
Lockheed designed this extra power into the tail: The L-1011 is the only commercial jet that can take off with full nose down trim. This was actually demonstrated to the airlines during the flight testing phase - with full nose down trim (which is a mis-set trim setting but has happened in the past on other aircraft and caused accidents) the pilot is still able to rotate the aircraft and climb away - it takes a lot of control wheel force to do it but it can be done - in other aircraft, the control column can be pulled full aft but with full nose down trim the nose won't come up for rotation. For those who don't know: Jet upset was an early event that happened more in the 1950's and early 1960' with the commercial jets than we see today - via rough air, the aircraft would get knocked out of it's stablized cruise condition until it was diving towards the ground out of control - the pilots would attempt to pull back on the wheel to get the nose to come up but most of the jets of that era did not have the power to overcome the excessive speed and thus they could not pull the aircraft out of the dive - when the L-1011 was being designed, the airlines wanted to make sure the L-1011 had enough pitch force to do this should it happen - to this day, a TriStar has never been lost as a result of jet upset and not being able to pull out of the resulting dive.
Now on to the technical description of the L-1011 pitch control system. The L-1011 incorporates an all-flying horizontal stabilizer to control movement in the pitch axis. This "all flying tail" is unique in the commercial aircraft industry. First of all, pitch control on most airplanes are usually controlled by elevators - on the L-1011 however, the primary part of the tail that controls pitch is the front part called the horizontal stabilizer, the leading edge of which which move up and down - the elevators are attached to the rear spar of this movable stabilizer piece - the elevators do move, yes, but not under direct pilot control. The elevators move as a direct result of stabilizer movement only via a physical mechanical link: When the stabilizer moves it's nose downward, the elevators deflect upward to increase the camber of the entire tail - this causes a downward moment and thus pulls the entire rear portion of the aircraft in a downward direction - this causes the nose of the aircraft to pitch up. When the pilot pushes the control wheel forward, this causes the stabilizer nose to move up, causing the elevators to deflect downward, increasing the camber effect to cause a lifting moment and thus pull the tail of the aircraft upward and this in turn causes the nose to pitch down.
The L-1011 has four hydraulic systems - by contrast, the DC-10 and MD-11 only has three hydraulic systems. All four of the 1011 hydraulic systems power the horizontal stabilizer, any one of which can operate it. Not all of the flight controls are powered by all of the hydraulic systems - most are powered by three of the four and only the tail is powered by all four - this is because the pitch system is considered to be the most critical. Like all widebodied commercial jets, the flight controls are only powered by the hydraulics - there is no manual cable backup system - if you lose all the hydraulics to a given flight control, you lose that flight control.
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Much ore on this fantastic bird at FlyTriStar
Lockheed designed this extra power into the tail: The L-1011 is the only commercial jet that can take off with full nose down trim. This was actually demonstrated to the airlines during the flight testing phase - with full nose down trim (which is a mis-set trim setting but has happened in the past on other aircraft and caused accidents) the pilot is still able to rotate the aircraft and climb away - it takes a lot of control wheel force to do it but it can be done - in other aircraft, the control column can be pulled full aft but with full nose down trim the nose won't come up for rotation. For those who don't know: Jet upset was an early event that happened more in the 1950's and early 1960' with the commercial jets than we see today - via rough air, the aircraft would get knocked out of it's stablized cruise condition until it was diving towards the ground out of control - the pilots would attempt to pull back on the wheel to get the nose to come up but most of the jets of that era did not have the power to overcome the excessive speed and thus they could not pull the aircraft out of the dive - when the L-1011 was being designed, the airlines wanted to make sure the L-1011 had enough pitch force to do this should it happen - to this day, a TriStar has never been lost as a result of jet upset and not being able to pull out of the resulting dive.
Now on to the technical description of the L-1011 pitch control system. The L-1011 incorporates an all-flying horizontal stabilizer to control movement in the pitch axis. This "all flying tail" is unique in the commercial aircraft industry. First of all, pitch control on most airplanes are usually controlled by elevators - on the L-1011 however, the primary part of the tail that controls pitch is the front part called the horizontal stabilizer, the leading edge of which which move up and down - the elevators are attached to the rear spar of this movable stabilizer piece - the elevators do move, yes, but not under direct pilot control. The elevators move as a direct result of stabilizer movement only via a physical mechanical link: When the stabilizer moves it's nose downward, the elevators deflect upward to increase the camber of the entire tail - this causes a downward moment and thus pulls the entire rear portion of the aircraft in a downward direction - this causes the nose of the aircraft to pitch up. When the pilot pushes the control wheel forward, this causes the stabilizer nose to move up, causing the elevators to deflect downward, increasing the camber effect to cause a lifting moment and thus pull the tail of the aircraft upward and this in turn causes the nose to pitch down.
The L-1011 has four hydraulic systems - by contrast, the DC-10 and MD-11 only has three hydraulic systems. All four of the 1011 hydraulic systems power the horizontal stabilizer, any one of which can operate it. Not all of the flight controls are powered by all of the hydraulic systems - most are powered by three of the four and only the tail is powered by all four - this is because the pitch system is considered to be the most critical. Like all widebodied commercial jets, the flight controls are only powered by the hydraulics - there is no manual cable backup system - if you lose all the hydraulics to a given flight control, you lose that flight control.
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Much ore on this fantastic bird at FlyTriStar
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Denti.
Extract from B737 FCTM re manual flying and A/T:
"To simplify thrust setting procedures, autothrottle use is recommended during take off and climb in either automatic or manual flight. During all other phases of flight, autothrottle use is recommended only when the autopilot is engaged...The autothrottle arm mode is not normally recommended because its function can be confusing."
flying raw data in my company means you're flying completely manual except for AT which is supposed to be in ARM
"To simplify thrust setting procedures, autothrottle use is recommended during take off and climb in either automatic or manual flight. During all other phases of flight, autothrottle use is recommended only when the autopilot is engaged...The autothrottle arm mode is not normally recommended because its function can be confusing."
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CWS
CWS useful for me in 2 ways....
When deviating around minor patches of weather. Leave AP in CMD and de-select LNAV/HDG and move the aircraft where you want in roll. Remains in CMD in the pitch mode so you won't deviate from the assigned alt.
De-selecting LVL CHNG/VS in climb and descent (again A/P in CMD) then pitch up/down for whatever you want. Autopilot will still acquire the altitude selected in the MCP so again no level busts. Useful for bunting over/under weather/traffic.
Using the CWS mode completely...Why? We are pilots, fly it!
When deviating around minor patches of weather. Leave AP in CMD and de-select LNAV/HDG and move the aircraft where you want in roll. Remains in CMD in the pitch mode so you won't deviate from the assigned alt.
De-selecting LVL CHNG/VS in climb and descent (again A/P in CMD) then pitch up/down for whatever you want. Autopilot will still acquire the altitude selected in the MCP so again no level busts. Useful for bunting over/under weather/traffic.
Using the CWS mode completely...Why? We are pilots, fly it!
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If I'm not mistaken the plane will capture the selected altitude (on 737) when climbing or descending in CWS only if the selected mode for AP is CMD,even though you're climbing in CWS Pitch (for ex if you deselected the pitch mode). If the selected mode is CWS ,you'll pass through the selected altitude,as NorthernSky said.
I-2021,am I wrong?
I-2021,am I wrong?
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If I'm not mistaken the plane will capture the selected altitude (on 737) when climbing or descending in CWS only if the selected mode for AP is CMD,even though you're climbing in CWS Pitch (for ex if you deselected the pitch mode). If the selected mode is CWS ,you'll pass through the selected altitude,as NorthernSky said.
I-2021,am I wrong?
I-2021,am I wrong?
If the AP paddle is only halfway up, therefore in CWS, it'll not capture. I might be wrong, but I think that's the case.
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Extract from B737 FCTM re manual flying and A/T:
"To simplify thrust setting procedures, autothrottle use is recommended during take off and climb in either automatic or manual flight. During all other phases of flight, autothrottle use is recommended only when the autopilot is engaged...The autothrottle arm mode is not normally recommended because its function can be confusing."
"To simplify thrust setting procedures, autothrottle use is recommended during take off and climb in either automatic or manual flight. During all other phases of flight, autothrottle use is recommended only when the autopilot is engaged...The autothrottle arm mode is not normally recommended because its function can be confusing."
Anyway, it is SOP to leave the AT in arm mode, the rest as you quote it above.
