TCAS RA Against an ATC Descent Clearance in Kuwait FIR
You are commander of an A320 at FL330 on airway UL934 inbound to Kuwait International (OKBK), 55 minutes from touchdown. Kuwait Control clears you: "Descend to FL290, cross RAGAT at FL290 or below." The first officer is pilot flying with the autopilot in VNAV; the aircraft passes FL326 at 290 kt / M0.78 and starts down. Eight seconds later TCAS calls "TRAFFIC, TRAFFIC", then "CLIMB, CLIMB". The traffic display shows an intruder 3 nm ahead and 700 ft below, climbing. The controller has just cleared a preceding aircraft to FL300 in the same block and the frequency is congested. Fuel on board is 6,200 kg with 5,100 kg required to destination plus reserves. The cabin is secure, the seat-belt signs are on, there is no weather and the aircraft is not turning. RAGAT is 30 nm ahead.
1. State, in sequence, the actions required from the moment the RA is annunciated until ATC has been informed. Justify the order.
Read the worked answer
Aviate first; the clearance is secondary.
- Recognise and call. Both pilots must see the RA. The PM calls "CLIMB RA" and takes the radios; the PF disconnects or overrides the automation and applies a smooth pitch input to place the aircraft in the green band.
- Pitch only. No roll, no configuration change, no speedbrake. The aircraft must not be flown opposite to the command, and the manoeuvre must be limited to what the RA demands - an over-aggressive pull costs speed and creates a secondary stall risk.
- Do not attempt the descent. Do not average the two instructions, and do not cross-check the RA against the intruder's displayed altitude; the traffic display is advisory, the RA is the only valid vertical instruction.
- Transmit "TCAS RA". A three-word standard call as soon as workload permits - enough for the controller to stop issuing altitudes and protect the other aircraft.
- Hold the response until "Clear of conflict", then resume the last clearance (FL290), announce "Clear of conflict, returning to FL290", and request an amended clearance if the profile is now unachievable.
A "CLIMB" RA is obeyed even though you have just been cleared to descend: the RA exists because the controller's picture and the aircraft's picture have diverged.
2. Is the deviation from the ATC clearance lawful, and what must be filed afterwards?
Read the worked answer
Lawful, but it is a deviation that must be notified and reported.
- Right to deviate. ICAO Annex 2, Chapter 3, 3.2.2 permits the PIC to deviate from rules and clearances to the extent necessary in the interest of safety - and only to that extent. No prior ATC approval is required or possible in the seconds available.
- Responding to the RA is itself required. PANS-OPS (Doc 8168, Vol I, Part III) requires immediate response to a RA and makes clear that an ATC clearance does not take precedence over it. A controller cannot clear you to ignore an RA.
- Notification is the crew's obligation. The controller must know immediately, because separation of the other aircraft is affected and because your altitude is temporarily outside the clearance.
- Written follow-up. File an air traffic incident report to the ANSP (Doc 4444, §15.1) and an occurrence report through the operator's SMS to the Kuwait DGCA within the State's prescribed time. Record facts only: time, level, RA type, intruder bearing/range/altitude trend, the evasive action taken, and the outcome.
- Do not reconstruct the event afterwards - the Mode S / TCAS data and the CVR are the record; the report must match them.
3. After "Clear of conflict" you are high and slightly fast with RAGAT 30 nm ahead. Can the crossing restriction still be met, and what is the real threat?
Read the worked answer
Altitude is achievable; energy is the problem.
- Crude profile check. The RA climb has left you around FL318–FL320, so about 3,000 ft to lose in 30 nm. At roughly 420 kt groundspeed, 30 nm is 4.3 minutes, so the required rate is about 700 ft/min - well inside the aircraft's capability even at idle.
- Therefore comply, but manage energy. Select idle and speedbrake early, plan the deceleration to 250 kt below FL100, and expect to need the gear or flaps earlier than normal on a busy arrival.
- Set a trigger for "unable". If the required rate rises above roughly 1,500 ft/min, or the aircraft is still fast at 10 nm to RAGAT, tell ATC "unable to comply, request level change" rather than diving - a rushed, high-energy descent into a dust-hazy Kuwait evening is a worse outcome than a re-clearance.
- Fuel cross-check. 6,200 kg against 5,100 kg required leaves about 1,100 kg (roughly 15 minutes). A go-around, a hold or a long vector will consume it; monitor it against a bingo figure and declare minimum fuel before it becomes an emergency.