Auto Take-off?
Guest
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Auto Take-off?
Hi,
This question was posed to me by a visitor to the flight deck recently. While I'm aware that most modern airliners have some sort of autoland capability, do any of them have a capability to take-off on automatics?
Not sure if such a system would have many uses, apart from from LVPs, but it doesn't seem to me that it would be too difficult to design.
Any ideas?
This question was posed to me by a visitor to the flight deck recently. While I'm aware that most modern airliners have some sort of autoland capability, do any of them have a capability to take-off on automatics?
Not sure if such a system would have many uses, apart from from LVPs, but it doesn't seem to me that it would be too difficult to design.
Any ideas?
Guest
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FF,
I'm not sure if that would work. Looking at the flight director when it is in T/O mode it seems to command a nose-up pitch for the entire takeoff run. I suspect that the autopilot would command a pitch up and you would get an underspeed rotation, probably resulting in a tailstrike.
This is on the 757 btw, I'm not sure how other types work.
If you fancy giving it a try, then please do post and let me know how it went, although I suspect we would be reading about the incident in the R&N section first.
I'm not sure if that would work. Looking at the flight director when it is in T/O mode it seems to command a nose-up pitch for the entire takeoff run. I suspect that the autopilot would command a pitch up and you would get an underspeed rotation, probably resulting in a tailstrike.
This is on the 757 btw, I'm not sure how other types work.
If you fancy giving it a try, then please do post and let me know how it went, although I suspect we would be reading about the incident in the R&N section first.
Guest
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A part from the CWS T/O . The A/P should not be engaged until above 100', and the aircraft has been airborne for at least five seconds. The ground mode on modern aircrafts is a direct law with full authority . immediately after the aircraft becomes airborne the flight mode is progressively blended in .
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ROYAN
This may be true for other aircraft types, but the Lockheed L1011 A/P in CWS can be used unrestricted for all takeoffs. However, those L1011's that were "reengineered" to be placed on the UK register have a CWS restriction. Also Mmo is .88 for UK registered TriStars, .90 for those on the US (and most other) registers. Same for scarfed pitot tubes and MDLC. The Brits were/are very sensitive to "not invented here".
This may be true for other aircraft types, but the Lockheed L1011 A/P in CWS can be used unrestricted for all takeoffs. However, those L1011's that were "reengineered" to be placed on the UK register have a CWS restriction. Also Mmo is .88 for UK registered TriStars, .90 for those on the US (and most other) registers. Same for scarfed pitot tubes and MDLC. The Brits were/are very sensitive to "not invented here".
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Airbuses do not does not takeoff with autopilot on, just flight director.
On the airbus the common modes for takeoff are Lateral : RWY (Runway) and Vertical/Speed : SRS (Speed Reference System).
The SRS give you V2+10 in normal config, or the greater of current speed/V2 OEI configuration to the acceleration altitude, with a maximum pitch of 18 degrees, and minimum V/S of 120 ft/sec.
The flight director is available on the takeoff run and initial climb, the autopilot engages 5 seconds after takeoff. This relies on a localizer being available, being 1/2 dot on the localizer, and heading with 20 degrees of the ILS course.
The primary flight display in this mode will show a yaw bar so you can tell the effect of wind.
If you not set this up, the aircraft will maintain runway track (RWY TRK) at 30 ft rad alt if you forgot to arm the nav mode before takeoff.
Royans comments above are airbus specific.
On the airbus the common modes for takeoff are Lateral : RWY (Runway) and Vertical/Speed : SRS (Speed Reference System).
The SRS give you V2+10 in normal config, or the greater of current speed/V2 OEI configuration to the acceleration altitude, with a maximum pitch of 18 degrees, and minimum V/S of 120 ft/sec.
The flight director is available on the takeoff run and initial climb, the autopilot engages 5 seconds after takeoff. This relies on a localizer being available, being 1/2 dot on the localizer, and heading with 20 degrees of the ILS course.
The primary flight display in this mode will show a yaw bar so you can tell the effect of wind.
If you not set this up, the aircraft will maintain runway track (RWY TRK) at 30 ft rad alt if you forgot to arm the nav mode before takeoff.
Royans comments above are airbus specific.
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"I'm not sure if that would work. Looking at the flight director when it is in T/O mode it seems to command a nose-up pitch for the entire takeoff run."
The FD is pitch up simply because it is in TOGA mode. If you selected another mode, the bars won't necessarily point up. FLCH mode on the 747-400, for example, (from memory) makes the FD point down when parked at the gate, even tho' the selected altitude is higher (probably trying to attain MCP speed by pitching down). V/S gives you sort of what you select (it seems to give a particular _initial_ pitch angle command for a particular V/S setting. Probably no good for autotakeoffs.
[Freezing Fog] Re LOC mode... will it capture on the ground on your particular aircraft? Never tried it.
Rgds.
Q.
The FD is pitch up simply because it is in TOGA mode. If you selected another mode, the bars won't necessarily point up. FLCH mode on the 747-400, for example, (from memory) makes the FD point down when parked at the gate, even tho' the selected altitude is higher (probably trying to attain MCP speed by pitching down). V/S gives you sort of what you select (it seems to give a particular _initial_ pitch angle command for a particular V/S setting. Probably no good for autotakeoffs.
[Freezing Fog] Re LOC mode... will it capture on the ground on your particular aircraft? Never tried it.
Rgds.
Q.
