While descending on the waterloo RNAV STAR to cyyz an E145 flight crew; distracted by other duties a...

Narrative:

We were on the YWT4 RNAV arrival to runway 23 at cyyz. It was our first time with this arrival/runway combination. This was one of those opd arrivals; which is complicated by itself; and we were given a late runway change to 23; which is an unusual runway for us. We also were dealing with low bleed air temperature while in moderate ice; having to slow down for an ATC speed assignment requiring speed brakes; all while complying with turns as assigned by ATC and changes to the aircraft configuration. We had to quickly re-brief the approach while trying to get the speed under control. We were descending when the captain selected 'speed hold' too close to our cleared altitude of 4;000 ft MSL and the autopilot blew through it and continued descending. We caught it too late (3;600 ft or so) and started climbing back up to 4;000 ft. ATC asked about our altitude and we said 'climbing back to 4;000 ft.' no further deviations occurred and we landed normally.we need to be careful using speed mode or when changing modes close to assigned altitude. Also; we needed better monitoring and crosschecking. The captain said he was changing the mode; which was good CRM; but I did not confirm what he did; and that was poor monitor/crosscheck. I will be more vigilant from now on; even with a familiar crew.

Original NASA ASRS Text

Title: While descending on the WATERLOO RNAV STAR TO CYYZ AN E145 flight crew; distracted by other duties and; perhaps failing to insure altitude capture was active; failed to level at 4;000 FT as cleared.

Narrative: We were on the YWT4 RNAV arrival to Runway 23 at CYYZ. It was our first time with this arrival/runway combination. This was one of those OPD arrivals; which is complicated by itself; and we were given a late runway change to 23; which is an unusual runway for us. We also were dealing with low bleed air temperature while in moderate ice; having to slow down for an ATC speed assignment requiring speed brakes; all while complying with turns as assigned by ATC and changes to the aircraft configuration. We had to quickly re-brief the approach while trying to get the speed under control. We were descending when the Captain selected 'SPEED HOLD' too close to our cleared altitude of 4;000 FT MSL and the Autopilot blew through it and continued descending. We caught it too late (3;600 FT or so) and started climbing back up to 4;000 FT. ATC asked about our altitude and we said 'climbing back to 4;000 FT.' No further deviations occurred and we landed normally.We need to be careful using speed mode or when changing modes close to assigned altitude. Also; we needed better monitoring and crosschecking. The Captain said he was changing the mode; which was good CRM; but I did not confirm what he did; and that was poor monitor/crosscheck. I will be more vigilant from now on; even with a familiar crew.

Data retrieved from NASA's ASRS site as of July 2013 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.

Attributes
ACN	1067155
Time
Date	201302
Local Time Of Day	1801-2400
Place
Locale Reference	CYYZ.Airport
State Reference	ON
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Make Model Name	EMB ERJ 145 ER/LR
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Route In Use	STAR YWT4
Flight Plan	IFR
Component
Aircraft Component	Autoflight System
Person 1
Function	First Officer Pilot Not Flying
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Altitude Overshoot Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy

While descending on the waterloo RNAV STAR to cyyz an E145 flight crew; distracted by other duties and; perhaps failing to insure altitude capture was active; failed to level at 4;000 ft as cleared.