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VFR transit request that ends with 'remain outside controlled airspace'

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VFR transit request that ends with 'remain outside controlled airspace'

You are flying a Cessna 152, B-HKB, from Shek Kong (VHSK) at 09:10 with one passenger on a planned local VFR flight to the southeast at 1,500 ft. Wind 100° at 8 kt, visibility 8 km, few cloud at 2,000 ft, QNH 1010 hPa. After departure Shek Kong Tower says: B-HKB, squawk 4701, contact Hong Kong Approach, report leaving the Shek Kong zone. You call: Hong Kong Approach, B-HKB, Cessna 152, request VFR transit of the TMA to the southeast at 1,500 ft. Approach replies: B-HKB, Hong Kong Approach, remain outside controlled airspace, VFR transit not available at this time, advise intentions. You are 2 nm from the TMA boundary, with rising ground to the north and a Cathay 777 being sequenced for Runway 07L on the same frequency. At your groundspeed of 95 kt you will reach the boundary in about one minute.

1. Critique your initial call and explain precisely what `remain outside controlled airspace` requires of you. What should you transmit back?

Read the worked answer
  • The call: it gave callsign, type, level and intentions, but no position. A transit request should say where you are relative to a known point or to the boundary - e.g. 2 nm northwest of the TMA boundary, 1,500 ft - because that is what the controller needs to sequence you and to check you are clear of the boundary.
  • What the instruction means: remain outside controlled airspace is not a clearance, not a route, and not a refusal of VFR flight. It is an instruction to keep the aircraft clear of the TMA in all three dimensions. It is your responsibility to know the lateral boundary and the base of controlled airspace at your position from the chart - near the islands the base can be low, so 1,500 ft may not be clear of it.
  • Reply: B-HKB, remaining outside controlled airspace, will advise - and then state what you will actually do: B-HKB, orbiting south of the boundary at 1,500 ft or B-HKB, returning to Shek Kong.
  • Do not enter while waiting for a clearance. ATC separation of IFR traffic does not protect you, and a 777 on approach will not be looking for a 152.

2. Approach says `B-HKB, standby`, then later: `B-HKB, cleared to enter controlled airspace via the harbour route, maintain 1,500 ft or below, squawk 4701.` What does `standby` mean, and what exactly must you read back?

Read the worked answer
  • Standby: the controller has heard you and will call you back. It is not an approval, is not a clearance, and you should not immediately transmit again. Stay outside controlled airspace and keep listening; at 95 kt you have under a minute of margin, so be ready to orbit.
  • Read back every element that limits your flight: the clearance limit and route (cleared to enter controlled airspace via the harbour route), the level restriction (maintaining 1,500 ft or below), and the squawk. Example: B-HKB, cleared to enter controlled airspace via the harbour route, maintaining 1,500 ft or below, squawk four seven zero one, B-HKB.
  • Squawk readback: speak the digits individually (four seven zero one). A wrong squawk readback is a common and consequential error.
  • Effect: the clearance only exists from the moment it is issued. Before it you were legally outside controlled airspace; after it you are in it, and must comply with ATC instructions and maintain VMC unless a special VFR clearance has been issued.

3. The cloud base to the southeast falls to 1,200 ft and visibility to 5 km, and terrain limits you to 1,500 ft. You want to continue. What can you request, what are the conditions attached, and what will you do if it is refused?

Read the worked answer
  • Request: B-HKB, request Special VFR clearance to the southeast, to remain clear of cloud and in sight of the surface.
  • What special VFR is: a clearance issued by ATC, subject to their approval and traffic, allowing flight in controlled airspace when the weather is below VMC. The pilot must remain clear of cloud and in sight of the surface; in most states it is limited to day. It is not an instrument clearance and gives no authority to fly in cloud or without visual reference to the ground.
  • Before asking: assess honestly whether you can keep clear of cloud and in sight of the surface, and whether terrain and the airspace base allow it. Here the usable band between terrain at 1,500 ft and cloud at 1,200 ft is very tight - near zero - so refusal is likely and diversion is probably the safer answer.
  • If refused: stay VMC outside controlled airspace and either return to Shek Kong or take a route and level that keep you clear. Never press on into IMC. If you are caught out and safety is compromised, tell ATC immediately and declare an urgency (PAN PAN).