A DHC8-400 pressurization system was MEL'ed so that the mode control switch was in the dump position...

Narrative:

Climbing in a DHC8-400 with 'manual' pressurization; we neglected to move the switch from 'dump' to 'man' before the takeoff roll. It wasn't until passing through 8;000' that we realized the incorrect position of the switch and corrected it. The 'cabin press' warning light illuminated for about 15 seconds before going out due to the cabin beginning to pressurize. This was our 2nd leg of the day in this aircraft that required the use of manual pressurization. The MEL procedure has you switch to 'dump' mode before touchdown and leave it there during engine start and the taxi out. There is nothing in the normal checklist that references the pressurization control between the taxi out and actually taking off to remind you to check the position of the 'dump' valve switch. Keeping the MEL manual out and open would be a good future procedure for me in a similar situation. During our first leg; it took about a minute for the pressurization to get under control during the climb out. Before it came under control; the cabin was climbing at 2;000 ft per minute. On our initial climb out on our second leg (elevation 5;600 ft); the cabin rate of climb was pegged at 2;500 ft per minute climb; but this wasn't unexpected based on what happened climbing out of our original departure point. It wasn't until climbing through 2;500 ft AGL that we realized the switch was in 'dump.' we corrected the switch position and the cabin slowly began to pressurize and fix itself. A considerable amount of concentration is required to monitor and control the pressurization during manual pressurization operations. We were mostly a VFR day during those three legs. If it had been a bad weather day; with any other significant challenges; it would have been very easy to land while being over pressurized because we were distracted from the constant monitoring that is required. With each passing leg; our performance became better; as far as being proficient with the manual pressurization procedures; but it is a handful even during the best of times.

Original NASA ASRS Text

Title: A DHC8-400 pressurization system was MEL'ed so that the mode control switch was in the DUMP position during start; but required to be switched to MANUAL before takeoff. The crew failed to select MANUAL and subsequently departed unpressurized until passing 8;000 FT.

Narrative: Climbing in a DHC8-400 with 'manual' pressurization; we neglected to move the switch from 'DUMP' to 'MAN' before the takeoff roll. It wasn't until passing through 8;000' that we realized the incorrect position of the switch and corrected it. The 'CABIN PRESS' warning light illuminated for about 15 seconds before going out due to the cabin beginning to pressurize. This was our 2nd leg of the day in this aircraft that required the use of manual pressurization. The MEL procedure has you switch to 'DUMP' mode before touchdown and leave it there during engine start and the taxi out. There is nothing in the normal checklist that references the pressurization control between the taxi out and actually taking off to remind you to check the position of the 'DUMP' valve switch. Keeping the MEL manual out and open would be a good future procedure for me in a similar situation. During our first leg; it took about a minute for the pressurization to get under control during the climb out. before it came under control; the cabin was climbing at 2;000 FT per minute. On our initial climb out on our second leg (elevation 5;600 FT); the cabin rate of climb was pegged at 2;500 FT per minute climb; but this wasn't unexpected based on what happened climbing out of our original departure point. It wasn't until climbing through 2;500 FT AGL that we realized the switch was in 'DUMP.' We corrected the switch position and the cabin slowly began to pressurize and fix itself. A considerable amount of concentration is required to monitor and control the pressurization during manual pressurization operations. We were mostly a VFR day during those three legs. If it had been a bad weather day; with any other significant challenges; it would have been very easy to land while being over pressurized because we were distracted from the constant monitoring that is required. With each passing leg; our performance became better; as far as being proficient with the manual pressurization procedures; but it is a handful even during the best of times.

Data retrieved from NASA's ASRS site as of April 2012 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	847463
Time
Date	200908
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Light	Daylight
Aircraft 1
Make Model Name	Dash 8-400
Operating Under FAR Part	Part 121
Flight Phase	Climb
Flight Plan	IFR
Component
Aircraft Component	Pressurization Control System
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Commercial
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural Published Material / Policy Deviation - Procedural MEL

A DHC8-400 pressurization system was MEL'ed so that the mode control switch was in the dump position during start; but required to be switched to manual before takeoff. The crew failed to select manual and subsequently departed unpressurized until passing 8;000 ft.