The Dash 7 was the only FAR25 transport category aircraft (
AFAIK) certificated for steep approaches up to 7.5 degrees, such as the MLS approach at Vail, Colorado (which was actually 8 degrees).
The Transport Canada certification criteria for steep approach approval were much tougher than the later ICAO standards , which were watered down. For instance, to certify for a 7.5 degree approach slope DHC was required to demonstrate a capture of the G/S from 2 degrees above the 7.5 degree slope, i.e. 9.5 degrees, with One Engine Inoperative!
Oh, and, by the way, the Dash 7 was eventually approved for the 7.5 degree slope with a 10 knot tailwind, at airfield elevations up to at least 10,000' ASL!
Here is an interesting link which tells the airport side of the story:
Abandoned & Little-Known Airfields: Northwestern Colorado