Under the Shelf, Through the Surface Area: A Solo Student and Class B Airspace
Student pilot Luis has 34 hours and a current solo endorsement. He wants to fly solo from a Class D satellite field to another Class D field 35 nm away in the club's Cessna 172, which has an operating Mode C transponder and ADS-B Out. The direct route clips Class B airspace: for about 8 nm the Class B floor extends to the surface, and the destination airport sits beneath a 3,000-ft MSL Class B shelf. Luis's logbook holds a solo endorsement dated 70 days ago and a Class B ground and flight training endorsement dated five months ago. His planned cruise altitude is 2,500 ft MSL. Forecast: 4,500 scattered, visibility 10 statute miles, wind calm. The chief instructor is away. The club dispatcher looks at the logbook and says, "The endorsement is in there - you're good."
1. Is the dispatcher correct? Identify exactly what Luis has and what he is missing for this specific route.
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The dispatcher checked one box and stopped.
What Luis has. A solo endorsement within the preceding 90 days (70 days old) satisfies 61.87(n). The airplane's Mode C transponder and ADS-B Out satisfy the equipment rules for Class B (91.215 and 91.225). Weather is comfortably VFR.
What he is missing. The Class B endorsement is five months old. Under 61.95, a student pilot may not operate in Class B airspace unless ground and flight training have been received and a logbook endorsement was given within the preceding 90 days. At five months, it is expired. Two things must happen: a flight instructor must re-accomplish and re-endorse the Class B training, and Luis must receive an explicit ATC clearance - "cleared into the Class B airspace" - before entering.
The subtlety. The endorsement only matters for the airspace he actually enters. Under the 3,000-ft shelf at 2,500 ft, he is below Class B and needs no endorsement and no clearance. The 8-nm segment where the floor is at the surface is different: there is no "underneath," so either he gets a fresh endorsement and a clearance, or he routes around it.
2. Luis says, "The shelf is 3,000 feet, I'll just stay at 2,500 and go direct." Explain the airspace geometry error and how you would brief the route.
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His mental model is that Class B has one floor. It does not - it is a stack of irregular shelves, and the floor changes along the route.
The error. For 8 of the 35 nm the Class B floor is the surface. At 2,500 ft in that segment he is not under Class B; he is inside it, and without a clearance he has violated the airspace regardless of altitude. The destination end is the opposite case: a 3,000-ft shelf genuinely permits flight at 2,500 ft without a clearance, which is probably where his assumption came from.
The brief.
- Print or draw the sectional excerpt and have Luis highlight the surface area boundary, not just the shelf line.
- Mark the two decision points: where he must already have a clearance, and where a route around begins.
- Brief the two legal options - obtain the endorsement and clearance, or fly a dogleg clear of the surface area - and have him fly the dogleg first.
- Brief the phraseology: he must hear "cleared into the Class B airspace," and he must not assume a frequency change or a traffic advisory is a clearance.
- Brief what to do if ATC says "remain outside Class B airspace": turn away immediately and fly the pre-planned alternate.
3. On the morning of the flight the ADS-B Out unit is squawking a fault and cannot be repaired until Tuesday. Can the flight still be made through the Class B airspace, and what are the options?
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Not by default. ADS-B Out is required to operate in Class B airspace under 91.225, and the requirement is independent of the transponder. An operating Mode C transponder does not cure a failed ADS-B transmitter.
Option 1 - request a deviation. ATC may authorize deviation from the ADS-B requirement, but the request must be made no later than one hour before the proposed operation. This is a request, not an entitlement; the controller may say no, and it is not something a student should be negotiating solo on his first trip.
Option 2 - route around. The surface-area segment is only 8 nm. A dogleg outside the lateral boundary keeps the flight legal with no equipment at all and no special permission. This is the cleanest answer for a student solo.
Option 3 - cancel or reposition. Fly a different destination or wait until the unit is fixed.
Teaching point. The equipment failure did not create a legal gray area; it created a routing decision. The instructor's job is to have Luis identify which of the three options he would choose and why, before he is airborne and improvising. Also note that the Class B endorsement, if not current, still blocks the airspace option regardless of the radio.