LO Principals Flashcards
Explain the objective of stealth design
Reduce the probability of detection
Describe active and passive aircraft signature reduction concepts
Active Signature
- Acoustic Signature: Reduce aircraft noise
- Infrared Signature: Engine exhaust/afterburners
- RF signature: Comms/navigation
Passive Signature
- Visual Signature Reduction: reduce glint/aircraft paint
- Radar Signature: EM
Explain why RCS is considered the most critical signature for most aircraft
Provides:
- Early warning
- Target Tracking
Define RCS and explain the factors that determine the size of RCS
-The measure of a targets ability to reflect RF signals in the direction of the radar reciever Factors: ) - Azimuth (aspect) of target - Elevation of target - Frequency of viewing radar - Polarization of viewing radar
Describe the 4 basic methods to make an aircraft stealthy to radar energy
- Shaping: reflect radar energy away from viewing radar
- Cancellation: Active or Passive, add waves together
- Absorption: turn radar energy to heat with RAM
- Transparencies: Allow radar to pass through
Describe the faceted shaping, compound curve and planform alignment techniques
- Faceted Shaping: Orient Flat surfaces to reflect radar away from viewing radar (F-117)
- Compound Curve: replace straight edges with curved to reflect less to viewing radar (B-2)
- Planform alignment: All angles exactly the same to reduce RCS spikes (F-22)
State the goals of radar absorption materials
- Reduce specular and multibounce reflections
- Reduce energy diffracted from trailing edges or discontinuities by absorbing energy as the wave travels along the surface
Describe how aircraft surface breaks and gaps affect total RCS
Radar reflections become significant at high frequencies and low graze angles
Describe engine inlet design, canopy design and other considerations/methods used to reduce RCS
Inlet design - screen grids: cover inlets (F-117) - Buried engines: inlet echo supression, RAM (B-1) - Intakes ontop of aircraft (B-2) - Shaping inlets with RAM Canopy Design - Made of radar abosrbing materials - Smoothly blended in aircraft - Shape deflects radar away Other - Antennas - Access Doors - External Stores - Air data sensors
Discuss basic systems that may be used to counter stealth aircraft
- Low frequency radar: long wavelength gens significant return
- High frequency radar: exploits scattering from shape defects
- Bi or Multistatic radar: Reciever(s) not co-located with transmitter
- Passive coherent radar: Ambient noise changes (i.e. radio stations)
Discuss the maintenance practices that assure aircraft LO properties
Extensive and expensive
- Maintenance tracking records
- visual inspections
- Mechanical verification
- Material reflective measurements
- True RCS measurements
- Diagnostic imaging
- Special facilities
Discuss the elements that contribute to the cost of stealth
- Acquisition cost: high initial cost
- Cost per flying hour
- Infrastructure cost (security, support facilities, etc.)
- Inspection cost
- Personnel cost
Discuss value and limitations of modern stealth aircraft
Value: - Stealth provides method of breaking kill chain Limits - Cost - limited number - complex mission planning - lack of flexibility - threats
Characteristics of E-RAM
Narrowband, thick (but light)
- causes cancellation with 180 degree phase shift
Characteristics of MagRAM
Broadband, thin (but heavy)
- Iron paint to turn radar into heat
