Air carrier first officer reported the captain began a descent too early in a high terrain area.

Attributes
ACN	1562217
Time
Date	201807
Local Time Of Day	1801-2400
Place
Locale Reference	SEFG.ARTCC
State Reference	FO
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	Large Transport
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Flight Plan	IFR
Person 1
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Instrument Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine
Experience	Flight Crew Total 8000
Events
Anomaly	Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Published Material / Policy Inflight Event / Encounter CFTT / CFIT

Narrative:

On approach into quito; seqm; we were cleared for the ILS Z 36. The approach requires we maintain FL180 until crossing qit VOR. The captain was pilot flying. Upon getting cleared for approach and in VNAV pth he set minimums in the altitude window. He was a little high to make the altitude crossing and the recommended speed of 220 KIAS at qit. I was looking up our missed; single engine missed; taxi and gate location on my ipad when I looked over to see the ca (captain) had selected vertical speed mode; 3000 FPM down and was descending through 17;100 ft prior to qit; instead of maintaining FL180 for terrain clearance as depicted and briefed on approach. I quickly advised him to level off as we were not yet permitted to descend on approach. Quito approach queried us and we explained we were maintaining 17;000 feet. The remainder of the approach and landing occurred without incident and no egpws event was triggered.

Original NASA ASRS Text

Title: Air carrier First Officer reported the Captain began a descent too early in a high terrain area.

Narrative: On approach into Quito; SEQM; we were cleared for the ILS Z 36. The approach requires we maintain FL180 until crossing QIT VOR. The Captain was pilot flying. Upon getting cleared for approach and in VNAV PTH he set minimums in the altitude window. He was a little high to make the altitude crossing and the recommended speed of 220 KIAS at QIT. I was looking up our missed; single engine missed; taxi and gate location on my iPad when I looked over to see the CA (Captain) had selected vertical speed mode; 3000 FPM down and was descending through 17;100 ft prior to QIT; instead of maintaining FL180 for terrain clearance as depicted and briefed on approach. I quickly advised him to level off as we were not yet permitted to descend on approach. Quito Approach queried us and we explained we were maintaining 17;000 feet. The remainder of the approach and landing occurred without incident and NO EGPWS EVENT WAS TRIGGERED.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.