« Previous Next »

HSI Mode Switch

Technical Information

Catalogue No: C1180
Category: Navigation/Inertial
Object Type: Control/Data Entry
Object Name: HSI Mode Switch
Part No: 25-001-01
Serial No: 408
Manufacturer: Marconi Avionics
Division: Inertial Navigation [IND]
Platform(s): Jaguar
Year of Manufacture: circa 1970
Dimensions: Width (mm): 60
Height (mm): 60
Depth (mm): 123
Weight (g): 360
Location: Triple Shelf Unit, LH (control panels) [Main Store]

H.S.I. Mode Switch
Type No. 25-001-01
Ref No. 6JA/111-8588
Ser No. 408
Code No. K0656


This is a Mode Switch to select the TACAN modes for display on the HSI. The NSN given in our database is NSN 6610-99-111-8588 and a Part No.75DSK6210.This item bears IND inspection seals.

The horizontal situation indicator (commonly called the HSI) is an aircraft flight instrument normally mounted below the artificial horizon in place of a conventional heading indicator. It combines a heading indicator with a VHF omnidirectional range-instrument landing system (VOR-ILS) display. This reduces pilot workload by lessening the number of elements in the pilot's instrument scan to the six basic flight instruments.  


A tactical air navigation system, commonly referred to by the acronym TACAN, is a navigation system used by military aircraft. It provides the user with bearing and distance (slant-range or hypotenuse) to a ground or ship-borne station. Aircraft equipped with TACAN avionics can use this system for en route navigation as well as non-precision approaches to landing fields.

The typical TACAN onboard user panel has control switches for setting the channel (corresponding to the desired surface station's assigned frequency), the operation mode for either transmit/receive (T/R, to get both bearing and range) or receive only (REC, to get bearing but not range). Capability was later upgraded to include an air-to-air mode (A/A) where two airborne users can get relative slant-range information. Depending on the installation, Air-to-Air mode may provide range, closure (relative velocity of the other unit), and bearing, though an air-to-air bearing is noticeably less precise than a ground-to-air bearing.

Click to enlarge Click to enlarge