At room temperature

If the antenna is mounted on the inside of the tip

AoA – Angle of Attack

it cannot be easily displaced by pressure

Memory for up to 100 user-defined named frequencies

f391 Thread Size:7/16-20 At room temperatureValve mounts in the sump, the same as original plug, with no projection. Cant be knocked off or opened by particles thrown from propellers. Opens only when operated with sampler cup, rod or wire. Clear cup permits inspection for water or contaminants. FAA approved. PN Manufacturing No. Application 05 01874 F 391 14 Aeronca, Beech AT 11, D 18S, Piper PA 11, 12,18, 20,22, Apache Champion, Howard 05 01875 F 391 18 Stinson, Waco VK, UPF, Seabee, Bellanca,