Drifting into Class B
A private pilot plans a 45-minute balloon flight from a field 8.5 NM south of a Class B primary airport. The airport's Class B airspace has an inner ring from the surface to 10,000 MSL within 5 NM, and an outer shelf from 3,000 to 10,000 MSL between 5 and 10 NM. The launch site lies under the outer shelf. The balloon is equipped with a two-way radio and a Mode C transponder. Surface winds are forecast from 180° at 8 knots, turning to 210° at 8 knots at 2,000 MSL. The pilot plans to climb to 2,700 MSL and remain below the 3,000 MSL shelf. Thirty minutes after launch, the GPS shows the balloon 4.6 NM from the airport at 2,800 MSL. The pilot has not requested Class B clearance. The approach controller is reachable on the radio. The pilot sees a suitable landing field about 0.8 NM ahead.
1. At the reported position, what airspace is the balloon in, and what requirements apply? Show the boundary reasoning.
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At 4.6 NM the balloon is inside the 5-NM inner ring; at 2,800 MSL it is between the surface and 10,000 MSL. That is Class B airspace. Class B requires an explicit ATC clearance before entry; merely being in radio contact or having a transponder is not enough. The pilot has the required radio and Mode C transponder but no clearance, so the balloon is in Class B contrary to §91.131(a)(1). VFR weather minimums in Class B are 3 statute miles visibility and clear of clouds. The fact that the pilot planned to stay below the 3,000-ft shelf is irrelevant once the balloon crossed inside 5 NM, because the inner ring's floor is the surface. The airspace boundary is both horizontal and vertical; the pilot crossed the horizontal boundary.
2. What should the pilot do immediately? Compare continuing the flight with landing at the field ahead, and explain whether descending would solve the problem.
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Contact ATC immediately and prepare to land. The pilot should call approach, state the balloon's position, altitude, and that it entered Class B inadvertently, and request a clearance. If ATC grants an explicit clearance, the pilot may continue, but must comply with instructions and avoid the airport core. If clearance is not granted, the pilot must exit the airspace. Descending will not exit Class B because the inner ring extends to the surface. The only reliable exit is to land. The field 0.8 NM ahead is reachable in roughly 6 minutes at about 8 knots; the pilot should use it if clearance is denied or uncertain. The pilot should not assume that a radio call equals a clearance. The safe decision is to land and sort out the airspace violation on the ground rather than continue deeper into the inner ring.
3. What error in flight planning created the situation, and how could a pilot plan a similar flight to avoid it?
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The planning error was treating the 3,000-ft shelf as a safe ceiling without accounting for horizontal drift into the 5-NM inner ring. The pilot launched 8.5 NM out, but the wind carried the balloon about 4 NM in 30 minutes, putting it at 4.6 NM. A safer plan would set a hard trigger: if the GPS shows the balloon approaching 6 NM from the airport, begin descent and land before 5 NM, or obtain Class B clearance before launch and maintain it. The pilot should also use the outer shelf only while remaining outside 5 NM; the floor changes abruptly at the boundary, so altitude alone does not keep the balloon clear. Finally, a clearance must be received before entry, not requested after the boundary is crossed.