Instruments Question AVC

[Pontius Navigator]

The V-bombers, and possibly others, had an autonomic variation setting control. There was a circular cam about 3 inches in diameter and contours made of dental material that modelled the magnetic variation throughout the world.

I think the cam was rotated with a drive from longitude drive from the GPI and a cam pick off for latitude. The navigator would set the variation at the airfield before takeoff.

Is that correct?

Now I think the variation map was the 1948 model and later 1973. Any ideas?

[Undried Plum]

Very clever!

[boing]

I remember our navigators referred to that device as the "wobbly cam".

The device did cause a major incident on a military VC10 supposedly going UK to Washington DC. Apparently the cam got lost and so did the aircraft, eventually heading to Florida. The story I got is that the pilots were blamed for not noticing the Sun was in the wrong position relative to the aircraft heading.


.

[Pontius Navigator]

Boing, not the one that went the other way over Greenland

Yes, an AVSC runaway could do that.

[boing]

PN

Can't have been too many of those events. I simply remember seeing a track plot that showed the aircraft somehow turning left and proceeding down the East Coast of the US practically parallel to it.

Perhaps Ex-Ascot knows the story.


.

[ian16th]

I have memories of a story of a Victor arriving at the coast of the USA hundreds of miles south of the intended landfall.

[Fox3WheresMyBanana]

By the 1990s, we had twin inertial nav systems that, according to the nav systems instructor, could do no wrong. I managed to get him airborne in the pointy jet, wearing his old blue flying suit from V-bomber days.
Ten minutes later, low level across the Fens;
"Where's that big pylon line, Gordon?"
(Head in kit)"Right, 1 mile"
"Look out left 9 o'clock"
".......................Oh."

[ExSp33db1rd]

I have memories of a story of a Victor arriving at the coast of the USA hundreds of miles south of the intended landfall.
Wine improves with age

Inertial / GPS ? Not too long ago a corporate jet got lost flying into Auckalnd from an overseas departure point. Eventually they sorted it out, they had programmed Longitude 174 West instead of 174 East for an enroute waypoint. Nothing wrong with the equipment, it performed precisely as designed.

[Pontius Navigator]

By the 1990s, we had twin inertial nav systems that, according to the nav systems instructor, could do no wrong. I managed to get him airborne in the pointy jet, wearing his old blue flying suit from V-bomber days.
Ten minutes later, low level across the Fens;
"Where's that big pylon line, Gordon?"
(Head in kit)"Right, 1 mile"
"Look out left 9 o'clock"
".......................Oh."

Not inertial but an old war story.
Our nav instructor was doing a night VID in a Meteor. They crept up on the target until they were a couple of hundred feet behind and he said Look up.

The pilot then said Look right. He did and there well off to one side was a starboard nav light. Oh s#£4&.

Now look left. There, off to port was a red nav light. ????

Now look up.

They were under a B36.

[Undried Plum]

And then there was KAL007.

The crew thought that selecting INS mode from Hdg mode would give them INS mode. It didn't because they were more than 7.5nm off-track at the time or were flying away from instead of towards the next waypoint that the INS was expecting.

[Pontius Navigator]

We once had an embarrassing mag/true error in the US.

The variation, IIRC, was 30 deg West and the pilots selected MAG as we headed South to the Syracuse VORTAC. Once overhead we then had a 30 Dec right turn into the airway West towards Des Moins. The aircraft was already on the numbers called out by the Nav and were the same numbers the pilots were already flying on. However they didn't realise the new heading was TRUE and the Nav didn't realise they were flying MAG.

I n short order we left the airway and had ATC shouting at us. Quick as a flash the AEO said we had had a compass problem that was now sorted and were regaining the centre line.

Quick as a flash ARC came back "NEGATIVE, I HAVE YOUR NAVIGATION, MAINTAIN HEADING". He made sure we remained off airway (J57?). Eventually we left his control and were able to conduct our planned bomb run on the Naval munitions storage at Hastings.

[barkingmad]

“And then there was KAL007.”

IIRC the best theory at the time, in the absence of DFDR data, was that the crew may have forgotten to select NAV mode from the in-use HDG mode and that no subsequent waypoint checks were performed on the assumption that the kit would take them to destination. Someone crunched the numbers for a rhumb line track and it came suspiciously close to the reported path.

Another reason to have the weather radar on painting terrain in those pre-GPS days..........

And then there was theory the US spy plane closely following the 747, whose captain allegedly had a standard of living above that expected of the normal KAL salary, was hoping the passenger aircraft would “tickle” the (new and unknown) Kamchatka Peninsula air defence radar into operation so’s the radar PRF and RPM and other parameters could be recorded and analysed.

Nowt like a good conspiracy theory to digest over the toast & marmalade...........