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Staines, UK 1972, June 18th.

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Staines, UK 1972, June 18th.

Old 27th Jun 2022, 14:49
  #61 (permalink)  
 
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Originally Posted by DaveReidUK View Post
The tailplane (in the days before we called them horizontal stabilizers) was moved by 3 hydraulic jacks in response to pitch (or a/p) inputs. The "elevator" wasn't really an elevator at all, it was a massive geared tab moved by a simple mechanical linkage to the stab. I suspect what you encountered was a failure of that linkage, which would indeed allow the tab to float freely.
Yes the "all-flying" tailplane, like the other primary controls, was driven by three hydraulic jacke, one for each hydraulic system. Our logic for the triplex system arrangements was that they were part of the way we met the reliability target which led to certification of autoland. As DaveReidUK wrote, the thing that looks like an elevator is a geared tab so can we agree on these matters and debate something else?
PS I wrote "our" because I worked at de Havilland at the time, not because I designed the system.
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Old 27th Jun 2022, 16:37
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Post #59

Wow! Takes me back 45 years! Excellent link. Couple of points:

- at the bottom of each HSI is the 'drift shutter'; when switched right the caption was blank and in heading mode the autopilot/flight director would fly the heading demanded by the heading bug. When selected left the caption AUTO appeared and Doppler drift was applied. The APFD would then fly the track demanded by the heading bug.

- the moving map (Doppler driven) was never used because it was too unreliable; IIRC the original design featured a pen to physically draw a record of the track actually flown on the map.

- the T3 had an extra yaw damper to compensate for the reduced directional stability caused by the lengthened forward fuselage; flight with dampers off was demo'd during training - very unsettling!

- the boost engine reliability was poor - fortunately it was only needed occasionally - high aircraft weight on hot days or on short or contaminated runways (snow/slush).

Yes the "all-flying" tailplane, like the other primary controls, was driven by three hydraulic jacks, one for each hydraulic system.
The hydraulic systems were labelled green, blue & yellow. When needing to go back to the cabin to use the toilet the pilots would refer to 'just going back to offload the yellow hydraulics'.

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Old 28th Jun 2022, 05:37
  #63 (permalink)  
 
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Discorde

I baulked at reading the link at the detail and shear complexity of the Trident. It certainly was a great but complicated aircraft.
I'm surprised nowadays that I understood it all let alone knew how to tweak the systems like the cabin on a GIB or GLA descent with brakes and 10500 reverse.
Doesn't mention the sixpence/half a crown feeling at Nicosia with the approach lights fast approaching on take off though.
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Old 28th Jun 2022, 06:28
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I remember it’s nickname was the gripper due presumably to the takeoff performance you are referring to blind pew. I mainly flew Boeings with such a surplus of performance that a full power takeoff was unusual. I did experience a jumpseat takeoff in a trident from Luton of all places and remember getting a very good view of the end of the runway. I seem to remember someone had also written ‚fastest over the threshold‘ on the back of the cockpit door. So performance overall seems to have been interesting. I do however associate it with happy holiday memories as a child mainly going to Geneva on skiing trips.
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Old 28th Jun 2022, 11:14
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It certainly was a great but complicated aircraft.
Yes, far too complicated and over-engineered (apart from T3 wings, which began to develop cracks after a few years of service). For example, gauges which showed how much pressure was being applied to the left and right wheelbrakes. P3 had to call out these figures during roll-out - utterly pointless. Quite a contrast to the B737 - no unnecessary kit unless customer-specified. No tail anti-icing - flight tests had confirmed satisfactory performance with iced-up leading edges.

I remember it’s nickname was the gripper due presumably to the takeoff performance
Apocryphal comment (source unknown) on LHR Tower freq as a T-Bird roared along the runway during take-off:

'You're witnessing de Havilland's attempt at the world land speed record.'
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