You draw a route beneath a Bravo shelf and explain that it stays outside Class B. Your instructor then asks about the aircraft's transponder and ADS-B Out. Why does equipment matter if the route avoids the shelf? Because the shelf and the equipment boundary answer different questions.
For this study session, use an ordinary training airplane originally certificated with an engine-driven electrical system, with no applicable equipment exception or ATC deviation authorization. Write that assumption at the top of the page before working through the example.
Draw the veil separately from the shelves
Under 14 CFR § 91.215(b)(2), the transponder and altitude-reporting requirement generally applies within 30 nautical miles of an airport listed in Part 91, Appendix D, section 1, from the surface upward to 10,000 feet MSL. This is commonly called the Mode C veil.
The veil does not turn all the enclosed airspace into Class B. On your sketch, draw the airport as a point, the veil as a surrounding boundary, and the Bravo shelves as their own shapes. Label each feature with the question it helps answer: equipment or airspace classification.
Use the Class B guide if the shelf geometry is unfamiliar. You should be able to describe both boundaries without using one as a substitute for the other.
Work through a route below a shelf
Imagine a position 20 nautical miles from a listed airport, with a Bravo floor at 4,000 feet MSL. Place the aircraft at 2,500 feet MSL and assume the underlying airspace is Class E.
The aircraft is below that hypothetical shelf. It is also inside the 30-nautical-mile equipment area. Under our aircraft assumptions, avoiding the shelf does not remove the transponder and altitude-reporting requirement.
Now move the aircraft horizontally while keeping its altitude fixed. First predict which boundary the route crosses. A transition out of the shelf's footprint and a transition out of the veil are different events; mark both on paper even if they occur close together in your invented drawing.
Check ADS-B Out on its own line
14 CFR § 91.225(d)(2) separately establishes an ADS-B Out requirement in the same 30-nautical-mile area, subject to the rule's exceptions and authorization provisions. A portable traffic receiver providing ADS-B In does not establish that the airplane meets the ADS-B Out requirement.
Do not assume that leaving the veil removes all equipment requirements. Both regulations identify additional airspace where equipment is required. Their exceptions and deviation provisions also need separate review; they are not established by a successful radio call.
For your notebook, make three entries: transponder with altitude reporting, ADS-B Out, and permission to enter the intended airspace. Write what evidence you would need for each. Ask your instructor how to verify the actual training airplane's equipment status and operating limitations.
Try it in AirspaceLab
Open the airspace probe, select a Bravo shelf, and choose a hypothetical altitude beneath it. Record what that geometry tells you. Then consult a current sectional and the cited equipment rules to add the veil check to the same scenario.
Finish with an explanation in your own words: where is the aircraft, which equipment requirements apply under the stated assumptions, and what would change if the route entered Class B? Compare the last question with the ATC standby article.
Sources checked: November 14, 2026. Distances and shelf altitudes in the exercise are invented. A simulator display does not verify equipment compliance or provide an ATC authorization.