Originally Posted by post #1 article
The pilots were using electronic aids to guide the aircraft through the low clouds, rain and late-day darkness to a landing on Runway 4 and had been told by air traffic control not to descend below 520 metres until passing an approach fix.
ATC instructs the flight to descend and maintain 1700 feet until DNNIS and clears them for the approach. Those who've flown into NYC area airports know that things often happen quickly and the likelihood of distraction and task saturation is increased. This is when "finger trouble" with making the proper inputs to the MCP and FMS usually happens. It's no coincidence that several levels of error catching measures are in force within the total system to stop such an occurrence from resulting in a CFIT:
1) Approach phase SOPs are designed (among other things) to catch input errors by cross checking altitude against distance to next fix. If you know the crossing altitude for each fix (approach plate) then you can easily see whether you're on profile. Since this can be misinterpreted or unintentionally neglected then;
2) ATC approach radar systems are designed to warn the controller if a flight is either below or predicted by the computer to be below the approach profile. A low altitude alert is generated and passed to the flight by the controller. This is what reportedly occurred in this instance. If the alert had not been issued then;
3) GPWS/TAWS/EGPWS (in order of sophistication and discrimination) provide the "last chance" warning of impending ground contact.
No EGPWS (what this airplane is equipped with) warning was reported in this instance. Had the airplane gotten much lower that far from the runway a terrain warning would presumably have been generated.
As to exactly what specific input error(s) could match with the scenario, I'll leave that to an E-Jet driver to explain. In each jet type I'm experienced in, the possibilities are different according to the avionics and vertical mode control design. It should go without saying that the airline in question will investigate and do what they must to reduce the likelihood of future similar occurrences.
Apologies to the vast majority of pilots who are already aware of the preceding.
