RE: Rx/Tx and air/ground Questions
1. yes a air Tx/Rx will operate on ground- such as landing/take off. A good example of longer times on the ground/and water is the hydro boats.
2. Do you mean as in a sub?- not sure maybe someone else could answer. If plane/hydro tips or crashes it may damage the electrionics.
3. yes the Laser4 and the HFS-04 will work together as long as they are the same channel. Also the Laser 4 is an air Tx and not meant to be used for ground.