> The plane was going 140 mph at impact, which is close to regular landing speed. But the 727 was descending at 1,500 feet per minute, much faster than the 10 to 20 feet per minute of a typical airliner landing.
I have to imagine that they were thinking seconds instead of minutes. coming down from 35k feet would take quite a long time if that was not the case. (20'/min would take ~30 hours)
For a standard 3-degree ILS approach, the descent rate is 318 ft per nautical mile. With a ground speed of 150 knots, that would be about 750 ft/minute. At higher altitudes and before the ILS, descent rates are usually higher, sometimes up to 3'000 or 4'000 ft with a default rate of 1'500 ft per minute.
I don't necessarily disagree, but it's possible that they were talking about the rate of descent at the point of impact, rather than the the rate of descent over the whole course of descending from cruising altitude to landing.
I think they were talking about touchdown. An aircraft that is landing approaches the ground quickly, levels off, and touches down at a couple of feet per second. An aircraft descending at 1,500 ft/min which no longer has control impacts the ground at 25 ft/s.
If you don't flare before touchdown and are not flying a Navy plane built for carrier landings, you will break your aircraft pretty badly when you slam into the runway at your normal descent speed.
I have to imagine that they were thinking seconds instead of minutes. coming down from 35k feet would take quite a long time if that was not the case. (20'/min would take ~30 hours)