The recording equipment type (and techniques) selected will be colored by the platform being recorded, the conditions of the recording, safety, and other practical matters. It will not be possible, for example, to set up a professional recording studio in an F16 Cockpit. However, every effort should be made to achieve the highest quality set-up possible.
Since recording is typically done in a mobile setting, look for equipment that is relatively compact. However, try to avoid sacrificing features and quality for the sake of compactness. In addition, be aware that hi quality, compact recording devices will be more expensive.
Also consider power availability. Most likely the recording equipment will need to be battery operated (for some if not all of the recording process). Be sure that battery operated units have visible indicators showing battery status and that you (and the person making the recording) know at what point a low battery situation effects the quality of the recording.
A key feature requirement is the ability to adjust the microphone record level 'on-the-fly' (some Sony machines, for example do not allow this) and an appropriate display for determining the input audio level. This feature is required to set the microphone to the appropriate recording levels and to avoid input clipping which would make the recording useless.
In addition, avoid units with AGC (automatic gain control) on the mic input or ensure there is a way to defeat the AGC feature. If AGC is on during the recording process the unit will modulate the input audio signal to achieve a constant signal level. This again results in a relatively useless recording, as all sound level relevance will be lost.
There are three primary options for recording format and hence equipment type: MiniDisc, DAT, and Cassette.
The first choice. MiniDisc is a robust media with excellent recording and playback features that make sound model generation and tuning significantly easier. Recorders are typically small and maintain battery power for reasonable periods. One of the best MiniDisc features is the ability to instantly jump around the recording when in playback mode (unlike a tape that must spool to the required point). This makes the MiniDisc easy to work with during sound modeling and tuning.
A good second choice, but not as flexible as MiniDisc for working with the final recordings. Because it is a tape, searching, reviewing, and general movement throughout the recordings are slower due to the spooling back and forth of the tape. Audio quality is high but the media is not as robust as MiniDisc. Tagging features similar to MiniDisc are available which are useful for locating specific sounds and sections of the tape. DAT units will be somewhat more expensive.
This is the equipment of last resort. Small units are abundant and inexpensive, However, in general the quality is poorer and there can be limited frequency response and signal to noise range. The media itself is also not as durable. The recording quality can also be effected by low battery states. In addition, cassette tapes are difficult to work with during sound modeling and tuning as they lack the ability to easily tag tape locations for quick search and review and suffer from the tape spooling problem as well.