AVRO LANCASTER TYPE O.6/A 1248 HAND HELD BEARING COMPASS

For the Lancaster bomber Observer/Navigator, obtaining a fix on the aircraft’s position in relation to its target was critical to the success of the mission and the safety of its crew.

In flight, the Observer/Navigator had to plot fixes every 6 minutes, calculate wind velocity and direction every 20 minutes and give the pilot any course and speed changes needed to arrive at their turning points and target on time.

Fortunately, typical RAF heavy bombers such as the Avro Lancaster and Short Stirling were equiped with a range of navigation aids including ‘fixed' compasses - one at the bottom left of the pilot’s main flying panel and another mounted against the rear wall of the navigators position.

These were also supplemented with an astro or the later, bubble compass which could be mounted below the aircraft's perspex astro dome for taking star and sun sights, together with a Drift Indicator (which provided information on the rate of aircraft drift in relation to its heading) as well as the GEE Radio Positioning System.

The Gee system relied upon a timed series of unique radio pulses transmitted from three radio transmitting towers stations 100 miles apart across the south coast of Britain.

With a range of 400 miles, the towers transmitted radio bursts across the European continent which intersected in a curved grid pattern. Using a Gee Map, the navigator could obtain a position fix to within six miles of his position via the GEE display projector with interpreted the timed and intersecting signals and projected a moving arrow onto the Gee map below. 

On their return flight from the target, both pilot and navigator also relied upon another radio transmission from their home airfield called the Beam Approach which moved a floating needle on the pilot's and linked, navigator's Beam Indicator display. either left or right depending on the aircraft's track. Pointing too far to either the left or right of the signal's direction informed the pilot of the need to correct course to bring the needle back to a central position on the Indicator display to stay on track.

Another navigational aid carried aboard in its own padded, wooden carrying box was the aircraft’s Hand Bearing Compass.

Stowed under the navigator’s desk, the portable, Head Bearing compass enabled compass heading readings to be taken out of the cockpit canopy, astro dome or any fuselage window to obtain a navigational bearing on a target or, just as importantly, obtain a compass bearing on three predominate land marks along the aircrafts’ flight path to obtain what is called a ‘running fix’

The observer  would take note off the direction of the bearing through the adjustable prism mirror as it was reflected up from the floating compass card. The markings on the compass card are reversed so that they appear correctly in the prism mirror. Once three directional ‘fixes were obtained, the navigator would mark these along a ruled line representing the aircraft’s flight path.

Using the map’s compass rose, a line was then drawn from each of the land marks and their compass bearings and where the lines crossed in the commonly called ‘peaked hat’ triangle - indicated the aircraft’s approximate position on the chart.

The Air Ministry issued Type O.6A Head Bearing Compass was carried by all heavy bombers as well as coastal command marine patrol and attack aircraft such as the carrier-launched Fairey Swordfish torpedo bomber.

The ‘O’ represented the Observer/Navigator and each compass featured either the early, wooden handle which was later modified to carrying an internal battery and bulb providing nighttime illumination for the prism compass reading or the later, all-metal handle with internal bulb and battery.

This Air Ministry Type O.6A Hand Bearing Compass comes complete with its original Air Ministry stamped, padded wooden carrying box and whilst its compass fluid has evaporated, the compass card still revolves as it should. The prism lens still moves on its gimballed hinge and the wooden handle unscrews from the base of the compass unit.

Unfortunately this unit’s original battery holding, wooden handle appears to have been replaced with a professionally turned solid wooden handle which would indicate some damage to the original handle either during the war or later.

* Please note that this original Recovery Curios Aircraft Display is also available in a Super Detailed, Large Scale 1/48 version with some astounding and simply awesome detail. Click on the 1/48 Scale Model Option' at the top of this page to order.

This Avro Lancaster Instrument comes complete with detailed Scale Model, Mango Wood Stand & Plaque plus Printed Fact Sheet featuring photo of instrument in the aircraft cockpit.

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