TCAS Flashcards
(16 cards)
TCAS full form ?
Traffic alert and Collision Avoidance System
TCAS range ( vertical & longitudnal )
Vertical - 9700 ft
Longtiudnal - 30 nm
TCAS working principle
SSR
interrogate - 1030 mhz
reply - 1090 mhz
TCAS determines :
- The bearing of intruders, in relation to the bearing of the aircraft.
- The distance between the aircraft and intruders, and the rate of separation or closure.
- The relative altitude of intruders, if intruders report their altitude via a Mode-C or Mode-S transponder.
The TCAS then calculates the intruder trajectory, the Closest Point of Approach (CPA), and the
estimated time (TAU) before reaching the CPA.
TAU is also called time to impact
What is formula for TAU
Time = DIST / Speed
The TAU is the ratio between the distance that separates both aircraft, and the sum of their speed.
How is proximate traffic shown and what does it signify ?
No collision threat
- Intruder in the vicinity of the A/C (closer than 6 NM laterally and ±1 200 ft vertically)
SHown on ND as solid diamond
What are other intruders in TCAS , how is it shown on ND ?
no collision threat
within the surveillance envelope (lateral range: Closer than 30 NM)
Shown as hollow white diamond
.
WHat does TA traffic mean and how is it shown on ND?
Potential collision threat
- TAU is about 40 s
Shown as solid circle
How is Resolution Advisory
(RA) shown on ND and what does RA traffic mean ?
Real collision threat
- TAU is about 25 s
PFD: Vertical orders
* Maintain actual V/S (Preventive Advisory) or
* Modify V/S (Corrective Advisory)
SHown on ND as solid square
What are the three modes of operation for TCAS?
The three modes of operation for TCAS are:
1. Traffic Advisory/Resolution Advisory (TA/RA) mode
2. Traffic Advisory Only (TA ONLY) mode
3. Standby (STBY) mode
How can the system be switched to TA Only mode ?
It can be switched to TA only mode , either manually or automatically
- Manually in case of aircraft degraded performance (engine failure, landing gear extended), or in
specific airports, and for specific procedures (identified by operators) (e.g. closely-spaced parallel or converging runways) - Automatically, if TA/RA mode is previously selected and:
- The windshear alert is triggered
- The stall warning is triggered
- GPWS alerts are triggered
- Aircraft is below 1 000 ft AGL.
When the TCAS is operating in TA ONLY mode:
- All RAs are inhibited and converted into TAs
- TA threshold is set to TAU ≤20 s, irrespective of the aircraft altitude
- No vertical speed advisories are indicated on the PFDs
- “TA ONLY” is displayed on the NDs
WHat does STBY mode do in TCAS control panel ?
advisory generation and surveillance functions are not active.
The TCAS does not trigger any alert. No TCAS information can be displayed on the PFDs and NDs.
What happens to the relative altitude on ND for intruders that do not report their altitude?
The relative altitude does not appear on ND.
What is the TCAS response for intruders that do not report their altitude?
The TCAS never triggers any RA.
TA may trigger
Under what condition does TCAS inhibit the TA?
The TCAS inhibits the TA when own aircraft altitude is above 15500 ft.
When Mode Sel switch is put to to TA/RA , will the TCAs display traffic and intruders if ALT reporting is OFF on ATC transponder panel or ATC transponder is on STBY?
TA/RA position : Normal position.
The RAs, TAs and proximate intruders are displayed if the ALT RPTG switch is ON and the transponder is not on STBY
