Crab,
The Captain was a very nice fellow, well liked, experienced, former military pilot. The Co-Pilot was also a Military aviator.....and was active in the National Guard (Territorials).
There was no hint or record of the Captain being anything but professional.
The Crew plainly goofed up.....and in my opinion....their being unfamiliar with the aircraft they were flying that day played a huge role in the chain of events (or chain of Non-Events if you will) that ultimately killed them and their two Medical Crew Members.
Recall the ILS Approach extant the day of the accident did not have a Locator....but just a Marker Beacon.
If my memory serves me right....the Accident Aircraft had a LORAN and the Duty Aircraft had a GPS.....but for sure the Area Nav unit was quite different from the one they were well used to from their regular flying.
There was a DME and VOR at the Airport.
Now ask yourself some questions about how you could fix the location of the AIRPORT if you had dual VOR/ILS Receivers, a DME receiver, an ADF receiver, and an Area NAV?
As there was no Locator....I would have been concerned about being turned in too soon by ATC, EXACTLY as the Crew was. They appeared to trust ATC would do as they asked.
It appears they never saw the Glideslope or never got onto the Glide Slope and seem to have abandoned the ILS and opted to complete a Localizer Only Approach.
It is surmised they confused the Outer Marker for the Middle Marker/Inner Marker due to the reported altitudes that were flown. They hit the mountain that was something like Seven Miles beyond the Airport (if my recollection of the distance is correct.....but it was quite some distance past the airport).
They could have used the "Hold" function to retain the DME readout.
They could have used the Area Nav to fix the Airport.
They could have used the Area Nav to "fix" the Outer Marker (even if not legal).
They did not or they would not have flown the profile they did.
So is that Crew Error, Training related, Management Error, Policy/SOP error?
Did the Federal Air Regulations and the Operator's OpSpec's cause a problem?
Could the company have purchased IFR Certified GPS for all of their Aircraft...should they have Standardized Cockpits in all their aircraft?
Excerpt from the NTSB Report
Aircraft Accidents and Incidents - Bluefield, Virginia 24605 Mercer County Airport Friday, April 22, 1994 14:45 EDT