Tridents and the Autoland system
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<<I never heard of 75m RVR at LHR >>
Guess you never worked at Heathrow? Not only have I seen RVR of 75m, I have also seen 000 on a number of occasions.
T.. Thanks for the tip; I'm following PBs pics on the Farnborough group.
Guess you never worked at Heathrow? Not only have I seen RVR of 75m, I have also seen 000 on a number of occasions.
T.. Thanks for the tip; I'm following PBs pics on the Farnborough group.
Last edited by HEATHROW DIRECTOR; 11th Apr 2013 at 16:11.
Actually I worked at Heathrow or to put it more accurately out of Heathrow for more than thirty years. It would be fair comment of course that anyone on the spot in ATC every day would have a more comprehensive view than mine. Even so I would call 75m RVR (as opposed to met visibility) a rare event - middle of the night perhaps ? Below 75m RVR would have stopped operations for everyone and I don't recall that myself.
Last edited by Tagron; 11th Apr 2013 at 17:18. Reason: Minor deletion
Please forgive me if I have said this before but the Smiths Autoland system as fitted to the Trident (which I never flew) and the Belfast (which I certainly did) was a very fine system and it was very accurate. It was, however, very complicated and relied on a Triplex system which worked on the principle that if any one single item failed during an autoland, then the other two systems would vote the troublemaker out of the logic and continue to a good resolution.
The big problem was that to achieve this (at the time) amazing result, the amount of equipment required to be carried was vast. the aircraft had to carry, for example, three VRUs (Vertical Reference Units), three RGUs (Rate Gyro Units), three Auto Pilots, three ILS and GS receivers and three bits of wire to every control surface.
I seem to remember that the whole lot weighed about 1,700 lbs which had to be be carried around whether you needed it or not.
All of this came before the invention of PCs, Microprocessors and the mobile phone.
Nothing that happens nowadays achieves a better result when it comes to landing in fog but I doubt that the modern equivalent weighs more than 100 lbs to achieve the same result, but it was all quite exciting at the time.
The big problem was that to achieve this (at the time) amazing result, the amount of equipment required to be carried was vast. the aircraft had to carry, for example, three VRUs (Vertical Reference Units), three RGUs (Rate Gyro Units), three Auto Pilots, three ILS and GS receivers and three bits of wire to every control surface.
I seem to remember that the whole lot weighed about 1,700 lbs which had to be be carried around whether you needed it or not.
All of this came before the invention of PCs, Microprocessors and the mobile phone.
Nothing that happens nowadays achieves a better result when it comes to landing in fog but I doubt that the modern equivalent weighs more than 100 lbs to achieve the same result, but it was all quite exciting at the time.
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Tagron. Yes, stopped it for just about everyone except an RAF VC10 which had brought in a VIP earlier. When asked his minima for take-off he replied "I do not have a minima"... so take-off he did!!
We used to get nervous in poor vis that the oncoming watch might not make it so we used to wind the ASMI out and watch if there was traffic on the M4.
We must have spoken many times. I started at Heathrow in Jan 1972 and retired in Nov 2002.
We used to get nervous in poor vis that the oncoming watch might not make it so we used to wind the ASMI out and watch if there was traffic on the M4.
We must have spoken many times. I started at Heathrow in Jan 1972 and retired in Nov 2002.
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G & T, that's an old wives' tale!
Hadn't heard the myth of the reason for the offset nose gear before!
HS Trident a.k.a. the HS Ground-Gripper. forward thrust provided by 3 noise generators, soundwaves thrusting the aircraft forward - More speed? turn up the volume....
Talking about fog at LHR, once after finishing a late shift on the south side missed the last bus & had to walk home, in the fog. Damned nearly walked into the outer waterway at the crossing by Stanwell, where there were no street lights, pitch black and 000 visibilty.
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Chevvron, the "tales of fire service vehicles being led into oil drums" were true - I managed it one night! The sound in the background of drums being hit as the man in the cab was talking on the R/T was something else.
There were specific taxy routes for Tridents from the cul de sacs and as said they stopped at the stop bar at the exit to set the GRM so they knew where they were as they groped their way along the green taxiway lights (set at max brilliance) Also there were makings to indicate curves coming up.
It wasn't just that the aircraft that were CAT III, but the crew had to be current as well. With 3 crew it wasn't unusual for them to hold in order for P2 & P3 to swap seats so they were legal.
I remember the day early on in LVP's when we had very low vis and ran a sweepstake to see what time the first a/c would land. Some hours later it was won. Only weeks later, we heard the pilot was being investigated for landing below limits and asking for our help! Problem was "finger trouble" when he was recorded as landing on the other Runway in the log.
We could prove he was OK as we all remembered the amount of money the lucky sod won!
There were specific taxy routes for Tridents from the cul de sacs and as said they stopped at the stop bar at the exit to set the GRM so they knew where they were as they groped their way along the green taxiway lights (set at max brilliance) Also there were makings to indicate curves coming up.
It wasn't just that the aircraft that were CAT III, but the crew had to be current as well. With 3 crew it wasn't unusual for them to hold in order for P2 & P3 to swap seats so they were legal.
I remember the day early on in LVP's when we had very low vis and ran a sweepstake to see what time the first a/c would land. Some hours later it was won. Only weeks later, we heard the pilot was being investigated for landing below limits and asking for our help! Problem was "finger trouble" when he was recorded as landing on the other Runway in the log.
We could prove he was OK as we all remembered the amount of money the lucky sod won!
Last edited by windowjob; 12th Apr 2013 at 22:10.
Last aircraft out of heathrow one night before it closed as RVR was falling below take off minima. We had twenty odd miles viz over a sea of fog which just covered the transmissometers.
Surreal.
Next company had a "look and see" policy (if we suspected any anomalies in the reporting system) which got us into egkk after it had officially closed - egll had an approach ban due viz.
Surreal.
Next company had a "look and see" policy (if we suspected any anomalies in the reporting system) which got us into egkk after it had officially closed - egll had an approach ban due viz.
P2 was, as it were, determined to go-around. The slightest hesitation on the part of P1 to say "Land" would result in a GA.
Tridents (BEA ones anyway) always carried 3 crew ie Captain and two FOs, although the non-flying FO was I believe, referred to as second officer. They swopped places on consecutive sectors.
I think most operators in this part of the world operate the monitored approach system in bad weather.
The first officer is programmed to fly the approach (using the automatics) to decision height with the intention of making a go-around.
The captain monitors the approach and is programmed to land the aircraft provided that sufficient visual reference is available at minima.
It works very well. The first officer calls "Decide" at minimums.
The captain will either call "Land" in which case he takes control and lands. The first officer simply takes his hands and feet off everything. Nothing needs to be said by him.
Otherwise, the captain calls "Go Around" whereupon the first officer immediately carries out a go around and the captain monitors his actions.
It gets rid of the bad old days where captains were flying the approach AND trying to look up at minimums and land while the first officer was sat on his backside doing very little.
The first officer is programmed to fly the approach (using the automatics) to decision height with the intention of making a go-around.
The captain monitors the approach and is programmed to land the aircraft provided that sufficient visual reference is available at minima.
It works very well. The first officer calls "Decide" at minimums.
The captain will either call "Land" in which case he takes control and lands. The first officer simply takes his hands and feet off everything. Nothing needs to be said by him.
Otherwise, the captain calls "Go Around" whereupon the first officer immediately carries out a go around and the captain monitors his actions.
It gets rid of the bad old days where captains were flying the approach AND trying to look up at minimums and land while the first officer was sat on his backside doing very little.
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I think Centaurus has misunderstood the SOPs. As JW411 has indicated, P2 flew the entire approach, with the firm intention of going around at DH, unless P1 said "Land" in response to P3's call "Decide".
There was no transfer of control during a missed approach.
If P1 called "Land" at DH, P2 would simply let go of the controls and be prepared to select reverse and lift-dumpers. If P1 said "Go-around", or said nothing - P2 would go-around.
There was no transfer of control during a missed approach.
If P1 called "Land" at DH, P2 would simply let go of the controls and be prepared to select reverse and lift-dumpers. If P1 said "Go-around", or said nothing - P2 would go-around.
As above from JW and AD, the procedure was simple and safe. The variant which I recall had ‘Decide’ at 15 ft above DH with either a ‘Land’ or a ‘GA’ response before DH (~2 sec later). With the latter the PF pressed GA for an automatic GA. In both instances the Captain continued monitoring.
The ‘wags’ view of having no response – default to GA, was (no response) “the Captain is dead – long live the new Captain” – ‘Land’. In reality this was an accepted procedure to cover the rare circumstance of an incapacitated Captain, thus the autoland option was the safest course of action.
During research flying which investigated the limitations of human capability in fog - auto disengagement or manual take over, the procedure was modified to include the Captain tapping the hand of the PF. This confirmed the decision to land and overcame intercom blocking if the visual scene / workload was being described.
The ‘wags’ view of having no response – default to GA, was (no response) “the Captain is dead – long live the new Captain” – ‘Land’. In reality this was an accepted procedure to cover the rare circumstance of an incapacitated Captain, thus the autoland option was the safest course of action.
During research flying which investigated the limitations of human capability in fog - auto disengagement or manual take over, the procedure was modified to include the Captain tapping the hand of the PF. This confirmed the decision to land and overcame intercom blocking if the visual scene / workload was being described.
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The big problem was that to achieve this (at the time) amazing result, the amount of equipment required to be carried was vast. the aircraft had to carry, for example, three VRUs (Vertical Reference Units), three RGUs (Rate Gyro Units), three Auto Pilots, three ILS and GS receivers and three bits of wire to every control surface.
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FWIW...many years ago, when black and white TV was in fashion there was a TV show in the USA called: THE TWENTIETH CENTURY...it was on CBS. Either Mike Wallace or Walter Cronkite was in the cockpit of the trident as it made an autoland, the captain looking backwards at the Camera explaining what was going on.
It might be of interest to you all to see it...of course I don't know if it is available today. It made quite an impression on me back then.
It might be of interest to you all to see it...of course I don't know if it is available today. It made quite an impression on me back then.