Common Results of a Dual Square Deployment: The most likely canopy configuration from simultaneous or near simultaneous deployment is a biplane with the main canopy in front and the reserve in the rear.

A biplane is both canopies flying in the same direction with one behind the other. Excluding extremes, the shorter rear canopy's leading edge rests against the steering lines below the trailing edge of the taller front canopy.

The next most common configuration is a side-by-side with the main risers behind the reserve risers.

A side-by-side is both canopies flying side by side in the same direction. They are usually touching end cell to end cell, or the end cell of the shorter canopy resting against the outside lines of the taller canopy.

Another fairly common configuration would be a fully inflated canopy (either main or reserve) with a trailing pilot chute, P.C. and bag or trailing uninflated second canopy behind the jumper. This scenario if left unattended would sometimes remain s it is, or result in one of the other configurations.

A less frequently occurring configuration is a downplane.

A downplane is both canopies flying away from each other and toward the ground.

Another infrequent configuration is an entanglement of the two canopies.

Note: Some people have always believed that you must choose a reserve that is smaller than the main. While this is probably a safe thing to do it is not an entirely accurate gauge. For example: a PD-143-R has shorter lines than a STILETTO-135. This combination flew well in a biplane with the main in front. 7 cell canopies typically have shorter lines than equally sized 9 cells.

Conclusion: Use great care to choose proper equipment. Choose a reserve that is similar in size to the main canopy.