737 Checklist question re use of Start switches
Start Switches.
Before Boeing embarked on a major change to checklist design several years ago and amplified areas of responsibility, the start switches were only set to Continuous during line up. Probably for bird strike precaution. Nowadays the start switches are turned to CONT before taxi and remain on until the after take off checks and then at pilot discretion. After all, the reason for start switches to CONT is for icing conditions and bird strike precaution yet they are left to CONT during taxi even in good weather.
The operating handbook for the JT8D engine cautioned against unnecessary use of the start switches because of a finite time life of the ignitors. Where engine anti-ice was used in flight, the start switches were first switched to CONT. Then engine anti-ice switched on. Then start switches turned off. Nowadays if engine anti-ice is required the start switches are left on for the period the engine anti-ice is on. Why is this so when it wasn't the policy before on the JT8D engine?
Currently the start switches are selected to CONT as part of the landing checks which are usually completed a minute or so before landing. It was like that on the 737-200 as well as the Classics and NG.
Question: If ignitor life was a factor in leaving the start switches until line up in the JT8D engines on the 737-200/ DC9, then is ignitor life not a factor anymore on the 737 Classics and NG series? And why are the start switches left until the last minute during the landing checks when it would be more simple to put the start switches to CONT at (say) 10,000 ft and thus reduce the landing checklist by one item? Assuming that on the CFM 56 series ignitor life is unlimited.