B777 logic - balked landing/GA after touch down
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The air/ground logic for the 777 is ever so slightly different, but that difference may have a big effect.
While the logic works off the RAD ALT. the transition from Ground to AIR mode happens when the tilt is taken out of the main gear trucks.
So, as the aircraft rotates, the trucks tilt to the normal position you see on most pictures. after a delay, the "airborne" signal is given to various systems, notably the auto brake and you get the distinctive "click" as it turns off.
On selection of up, the gear is hydraulically driven flat as the doors open and then retracted. There is a delay for all this to happen and TOGA is not available until the "AIR" signal is delivered from the gear tilt.
So, TOGA is not available on the ground, hence when doing T+G's, the thrust is manually set. It is also not available for a definite period (2-3 seconds as a GUESS) after leaving the ground. This would also apply in the event of a bounce.
I have done many simulated bounce recovery's in the sim. Often you touch down again, It is possibly the most energy deficient maneuver I know: well below Vref, nose high, no power, engines near idle and no time!!!
If the TOGA switch's were pushed any time before this "AIR" signal--NOTHING
So
READ and UNDERSTAND the FMA
Back up (or beat) the automatics. I can not imagine a situation where I would not manually push the T/L up, But I was not there!
It is NOT a go-around, leave the config. alone until ground clearance is assured.
While the logic works off the RAD ALT. the transition from Ground to AIR mode happens when the tilt is taken out of the main gear trucks.
So, as the aircraft rotates, the trucks tilt to the normal position you see on most pictures. after a delay, the "airborne" signal is given to various systems, notably the auto brake and you get the distinctive "click" as it turns off.
On selection of up, the gear is hydraulically driven flat as the doors open and then retracted. There is a delay for all this to happen and TOGA is not available until the "AIR" signal is delivered from the gear tilt.
So, TOGA is not available on the ground, hence when doing T+G's, the thrust is manually set. It is also not available for a definite period (2-3 seconds as a GUESS) after leaving the ground. This would also apply in the event of a bounce.
I have done many simulated bounce recovery's in the sim. Often you touch down again, It is possibly the most energy deficient maneuver I know: well below Vref, nose high, no power, engines near idle and no time!!!
If the TOGA switch's were pushed any time before this "AIR" signal--NOTHING
So
READ and UNDERSTAND the FMA
Back up (or beat) the automatics. I can not imagine a situation where I would not manually push the T/L up, But I was not there!
It is NOT a go-around, leave the config. alone until ground clearance is assured.
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On selection of up, the gear is hydraulically driven flat as the doors open and then retracted.
While the logic works off the RAD ALT. the transition from Ground to AIR mode happens when the tilt is taken out of the main gear trucks.
Can you confirm that it is truck tilt and not the landing gear beam load sensors which give air/ground data to the AP and TMCS for the go-around function? Ref Boeing 777 AMM D&O 32-09-00. Or is it a combination of both?
I'm having trouble understanding the relationship between the PSEU cards and the WOW cards.
Thanks.
I would say the trucks or bogies are driven from forward wheel up to forward wheel slightly down (relative to the airplane longitudinal axis).
Here is what it looks like: a 'gear swing' of the main landing gear of a 777 (-300ER) in the hangar.
Only the two ACMP's (electric pumps) are used, this is why the gear retracts very slowly.
https://youtu.be/b93ekEpTZ-w
Another one: https://youtu.be/w4bTPq6qNTs?t=24s
On a 777-200: https://youtu.be/NYyWdbTWtSs
In the air: truck attitude during retraction: http://cdn.c.photoshelter.com/img-ge...akeoff-09R.jpg
Here is what it looks like: a 'gear swing' of the main landing gear of a 777 (-300ER) in the hangar.
Only the two ACMP's (electric pumps) are used, this is why the gear retracts very slowly.
https://youtu.be/b93ekEpTZ-w
Another one: https://youtu.be/w4bTPq6qNTs?t=24s
On a 777-200: https://youtu.be/NYyWdbTWtSs
In the air: truck attitude during retraction: http://cdn.c.photoshelter.com/img-ge...akeoff-09R.jpg
Join Date: Oct 2013
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singleseater great post with good details about the logic of the air/ground sensing system. Regarding the bounced landing recovery FCTM suggest to change the config to Flaps 20 and follow normal go-around procedures.
From 777 Flight Crew Training Manual
Bounced Landing Recovery
Bounced Landing Recovery If the airplane should bounce, hold or re-establish a normal landing attitude and add thrust as necessary to control the rate of descent. Thrust need not be added for a shallow bounce or skip. When a high, hard bounce occurs, initiate a go-around. Apply go-around thrust and use normal go-around procedures. Do not retract the landing gear until a positive rate of climb is established because a second touchdown may occur during the go-around.
If higher than idle thrust is maintained through initial touchdown, the automatic speedbrake deployment may be disabled even when the speedbrakes are armed. This can result in a bounced landing.
If the speedbrakes started to extend on the initial touchdown, they will retract once the airplane becomes airborne again on a bounce, even if thrust is not increased. The speedbrakes must then be manually extended after the airplane returns to the runway.
And also
After Touchdown - Touch and Go
• Maintain runway alignment (PF)
• Flaps 20 (IP)
• Reset stabilizer trim (IP)
• Check speedbrakes down (IP)
• Thrust levers vertical (PF)
• Go-around thrust (PF)
• Rotate at Vref
• Climb Vref + 15-25
It is NOT a go-around, leave the config. alone until ground clearance is assured.
Bounced Landing Recovery
Bounced Landing Recovery If the airplane should bounce, hold or re-establish a normal landing attitude and add thrust as necessary to control the rate of descent. Thrust need not be added for a shallow bounce or skip. When a high, hard bounce occurs, initiate a go-around. Apply go-around thrust and use normal go-around procedures. Do not retract the landing gear until a positive rate of climb is established because a second touchdown may occur during the go-around.
If higher than idle thrust is maintained through initial touchdown, the automatic speedbrake deployment may be disabled even when the speedbrakes are armed. This can result in a bounced landing.
If the speedbrakes started to extend on the initial touchdown, they will retract once the airplane becomes airborne again on a bounce, even if thrust is not increased. The speedbrakes must then be manually extended after the airplane returns to the runway.
And also
After Touchdown - Touch and Go
• Maintain runway alignment (PF)
• Flaps 20 (IP)
• Reset stabilizer trim (IP)
• Check speedbrakes down (IP)
• Thrust levers vertical (PF)
• Go-around thrust (PF)
• Rotate at Vref
• Climb Vref + 15-25
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From the video of gear retraction, I can see that the tilting down of main wheel truck is part of landing gear retraction sequence. If the GRD to AIR logic starts after the main wheel truck position changes (to forward wheels slightly down), what happen to the logic if the GEAR lever, for any reason, remain in DOWN position ?
