The callout "Radio Altimeter alive" should be made by the first crew member observing the Radio Altimeter activation at 2500' AGL
Agree. After take off in the old 737-200 it was our company policy to set the radio altimeter alert height to its maximum which was 2500 ft. It would be left there for the rest of the flight until the light was actuated during descent for landing. The radio altimeter instrument itself was quite large. There was no aural RA MDA or DH warning but a bright amber light which was actuated as the aircraft passed 2500 ft RA height on descent. After that, further re-setting of the RA warning height was up to the pilot.
Descending at night over the mountains into Honiara in the Solomon Islands in the South Pacific where the MSA was 8000 ft within 25 miles of the airport (adjacent to the sea shore), it was common to see the RA 2500 ft alert light flash on and off momentarily as we passed over close terrain. It was sometimes quite unnerving in the dead of the night to realise there was big hills immediately below you. That is what we called situational awareness with a vengeance. Having flown the same route in fine conditions, made you realise it was no place to make mistakes in altitude awareness.
During practice GPWS pull up manoeuvres in the simulator the radio altimeter light in the 737-200 comes alive at 2500ft above terrain while the aural warning of PULL UP does not occur until a few seconds later, depending on rate of descent. In the 737-300 series and above, there is no bright RA warning light and one must rely on seeing the first appearance of the RA needle which is small. The needle colour might change though. If making a normal IMC descent into an area where there is substantial terrain en route and not under radar control, the GPWS warning is designed to give you sufficient time to react and climb out of trouble. Most times a GPWS terrain warning has a startle factor and any indecision by the crew to pull up can be fatal.
A wise pilot should know where he is at all times. However, CFIT accidents often prove otherwise. As soon as the radio altimeter comes alive at such a rate it is obvious something is seriously amiss, an immediate pull up at max power to at least 20 degrees has been shown to save you at least 500 ft versus waiting for the aural PULL UP to sound and causing the pilot to react That doesn't mean to say the pilot should be staring at his radio altimeter all the time during the descent. A modicum of common sense must prevail.
But going into some parts of the world where ATC radar or ground navaids may be unreliable, in an area of significant terrain, it is worth using good airmanship by keeping a wary eye for any sudden and unexpected appearance of the radio altimeter needle coming alive in a hurry. That is the time to get going and pull up real quick without waiting for the GPWS aural PULL UP warning first. Caution: Personal opinion only
