Avionics, VOR system, DME system, INS avionic system advantages and disadvantages
Modern tactical aircraft incorporate digital avionics systems with federated, centralized or distributed avionics architectures that share data via interconnecting data buses, The design of the digital avionics architecture has an impact on the combat survivability of the aircraft, Survivability in combat is defined as ‘the capability of the aircraft to avoid and/or withstand a man-made hostile environment.
An Avionics Technician is suitable for people who like practical and hands-on work, it is suitable for people who want to work in a supportive work environment, It is perfect for people who love to work indoors, An Avionics Technician is not suitable for people who like to help and teach others.
Survivability is made up of two elements, susceptibility, the inability of the aircraft to avoid being damaged by various elements of the man-made hostile environment, and vulnerability, the ability of the aircraft to withstand the damage caused by the hostile environment, so, a tactical aircraft should be designed to avoid being hit and to survive if hit, This thesis explores the survivability advantages and disadvantages inherent in the design of digital avionics system architectures.
INS-Inertial Navigation System
INS avionic system is a long-range navigational aid, it stands for Inertial Navigation System, It offers aircraft velocity (3D) and position fix (3D), INS is based on DR, what makes this technology quite amazing is that it is a self-contained system, so, no ground stations are required for operation.
In the Aircraft, In addition to velocity and position, INS offers Track to fly, Off-track distance, Distance between 2 points, it stores alternate destination positions, it determines true North direction, Recalculates ETAs.
INS avionic system is a self-contained airborne system that does not need any outside NAV source, It displays in real-time the Aircraft velocity and position, It operates at all the altitudes, Sometimes GPS is used as an aid to INS in order to correct or attenuate errors, there are two types of INS in the Aircraft which are Stable-Platform INS or Gimballed INS and Strap Down INS.
Stable-Platform INS or Gimballed INS isolates the gyroscopes and accelerometers from the aircraft angular motion, and remains in-synch with the earth co-ordinate system, The system contains 3 Gyroscopes(G) viz, GROLL, GPITCH & GYAW, It contains 3 movable Accelerometers (A) viz. ALAT (AN-S), ALON (AW-E) and AALT.
Strap Down INS has no moving parts, so, the accelerometers are solidly connected to the airframe and gyroscopes are well aligned with the aircraft X-Y-Z coordinate system, It contains three laser gyroscopes viz. GROLL (Gx), GPITCH (Gy), GYAW (Gz), Strap Down INS is mechanically simple to realize, Laser gyros are more robust than traditional ones.
Stable-Platform INS gets aligned with the earth coordinate system despite aircraft angular motion, accelerometers and gyros are protected from malfunctioning due to severe maneuvers since they are not directly connected to the airframe.
INS avionic system disadvantages
Errors are generated by non-orthogonality of accelerometers, Vibration and thermal variation may cause flaws in information data, INS is an expensive technology, Drift Error is approx. about +/- 0.5 kts (+/-k 1 Km/hr), Stable-Platform INS is mechanically more complicated to realize, Errors generated by non-orthogonality of gyros, Gyros may suffer from EMI.
NAV accuracy is highly dependant on the A/C maneuver, given that the accelerometers and gyros are directly connected to the airframe, Strap-Down INS demands more computations as first need to convert acceleration from Aircraft coordinates to the earth coordinates then perform DR to get the velocity and position.
VOF-VHF Omnidirectional Range basics
VOR avionic system is a short-range navigational aid, it stands for VHF Omnidirectional Range, VOR provides Aircraft radial with respect to a ground station, the VOR system informs us of the aircraft location only as an entity seen by the ground VOR transmitter, If you want to know where the aircraft is located, tune VOR receiver to at least two VOR ground stations and obtain the 2D position fix.
Applications of VOR such as V-Airway: Used to assign highways in the sky, Track intercept: To be able to get back to the track due to crosswind, Simply fly toward the needle of the VOR display known as the course deviation indicator to ensure that the aircraft is going in the direction of the VOR ground station.
VOR system is more efficient than ADF, its indicator point to the ground VOR transmit system, ADF presents a relative bearing corresponding to the offset between the aircraft longitudinal axis, so, the NDB does not point to the ground base beacon.
Disadvantages of the VOR system
It is limited to LOS due to VHF band operation, Error is approx. about +/- 2 Degree, VOR signals are either reflected or blocked or distorted due to buildings, Mountains, Fences, power lines, etc, At higher altitude interference may occur between two ground stations operated at the same frequency, VOR does not provide the aircraft heading, it only points to the ground station, Though GPS is taking place of VOR, VOR is still in use as a back up navigational aid system in case of satellite link failure.
DME-Distance Measuring Equipment basics
DME avionic system stands for Distance Measuring Equipment, It is a navigational aid, It is rarely affected by precipitation static and thunderstorms, DME instrument provides distance between Aircraft and Ground station, we need separation between the Aircraft and the DME station measured overground.
On the Ground, DME operates in the UHF frequency band from 960 to 1215 MHz with 100 number of channels, Each ground station is able to handle 100 Aircrafts simultaneously, DME system is referred as Integrator, It operates in the UHF band, It operates in the range from 150 to 200 miles.