Activity Update to WE 20th August 2021

This is a compendium update of activities up to August 20th

T86

The Tx and Rx reflectors have had a coat of black paint (for now), see accompanying photo.

We are nearing the conclusion of the refurbishing and painting of the aerial assembly and pedestal platform but it does seem like a never-ending task due to all the waveguide runs and inaccessible places. Still to do are reassembly of all the items removed, JA aerial, In-Flight aerial etc. which is a two-man job.

Some parts of the aerial system also require the aerials to be tilted back to finish the painting; this to is a two man job; one on the brake switch and one on the hand crank to wind the aerials in elevation. Moving the aerials in bearing is not a problem, as long as the brake is off!

Aerial positioning and control (bearing) Part 1

In the odd moments I get I’m still trying to unravel the mysteries of the bearing brake system and the associated sector, end stop and limit switch operation. A total of 14 microswitches (I think). I know what switches should operate and when but that’s the start of the problems in that the synchro dials that indicate the mils of the aerial position do not tie up with the physical position. SJ operates at the vehicle centre line (straight out over the rear of the cabin) and the corresponding mils should indicate ‘0’ but they don’t, they indicate 24xx or something around there. Is it a set up problem? Of course when operating the T86 operationally you never actually checked the mils reading for aerial positions, or I can’t remember doing it. This photo shows where the various microswitches are located, they reside on the rotating pedestal shaft, the Bearing Stop Unit and the Switch Unit Bearing (the Geneva Mechanism and it microswitches sit below this unit).

Also see the Pedestal Assemblies drawing here.

Aerial positioning and control (bearing) Part 2

To add to the headache….. With the aerials at ‘0’ and SJ is operated (closed) by a small spigot on the main pedestal shaft the Sector the Limit and Sector lamps are out on the Pedestal End Stop Indicator out, sounds correct. So why is the SA /SB Lamp on, this lamp should only be on in an end stop? Why is the Limit Override lamp always on? Operating the Limit override switch on the console makes no difference but the Limit Override lamp goes out if the Bearing Brake is applied on the Console. I haven’t found a description of when the lamps come on and in which sequence (yet). Only answer is to finish my redrawing of the circuits controlling the lamps on the Pedestal End Stop Indicator.

I read up on a couple of APs; the story you get depends on which AP you read.

AP 1: Move the aerials to the Datum Zero Line on the trailer and if required release the clutch under the coarse mils dial and adjust to zero.

AP 2: Move the aerials to the Centre Line. Check the micro switch(s) operation at the mils they operate at and allow for any difference from the mils reading at the Centre Live from zero (implying the mils are not zero at the centre line).

Here is the engraved notch on the pedestal shaft that indicates the Centre Line.

The first thing I don’t understand is: When moving the aerials to around 200 degrees (CW or CCW) the Limit lamps light and with a bit more movement the Sector lamps light. That doesn’t look right to me hence the checking of the mils dials to see if I was actually at the centre line when starting or if I was 360 degrees out. The mils reading is not desperate if not zeroed but I currently can’t relate it to the mils at which the microswitches operate. The Sector lamps are illuminated by SC/SD in the Switch Unit Bearing while the Limit lamps are illuminated by SM/SN on the pedestal shaft.

All I want to achieve are some straight forward notes for us and anyone in the future who will be moving the aerials and what the indications mean but mainly to prevent someone ripping out the cable winder.

The clockwise and counter clockwise sectors of the aerial movement in bearing checked. Outer sector indicators on the console checked, see below.

A suspected fault with two indicators on the pedestal indicator unit remains to be investigated.

Protective wooden covers were constructed for the pedestal roof as painting of the roof commences. New duck boards have been constructed for the roof but these will only be fitted once restoration is complete, see accompanying photo.

LCP

Simulator run up for a check and all booted correctly. The simulator was left to run while other work was carried out.

Returning to check the simulator I found a fault had occurred on one of the display monitors (Technical Supervisor position).

The monitor is not suspect but a CHARGE (video display processor) Pixel Store is the more likely fault and I will swap the CHARGE Pixel Store with a spare, or extend the fault finding, spares are available.

Pete H

2 thoughts on “Activity Update to WE 20th August 2021”

    1. I don’t remember all that gubbins in the pedestal when I was working on the T86. Mind you I think we the only time we ever bothered about the actual position of the aerial system with respect to the vehicle datum was when we trialled taking the aerial on and off into its transit cage. I think we did this twice in the 7 years I was on the equipment. Still it was pretty difficult to do this once the trailer was on 4ft pillars.

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