Question regarding accel/stop certification
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Join Date: Dec 2007
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Question regarding accel/stop certification
I'm not a test pilot, just a regular line driver, so I was hoping one of you test fellas might help me out:
1)In the situation where a runway is NOT contaminated with slush/snow etc, but braking action is never the less 'poor' due to say rubber deposits, PIREPs etc, while the dry or wet runway takeoff data would cater for the accelerate/GO case, how would you cater for the Accelerate STOP case, given that you have no valid charts for it? As I see it, there will be little contaminant 'retardation' in the accelerate phase, but less than nominal braking in the stop portion from V1.
Indeed, is it something that is even considered in certification?
2)On a different note: given that jet transport aircraft, by and large have to carry out an emergency descent for depressurization within the confines of the available oxygen envelope (something like a staircase pattern in my manual) and that the certification assumes use of speedbrakes and Mmo/Vmo(correct me if I'm wrong there) what happens if you don't have them? The checklists for loss of speedbrake conditions never seem to mention the fact that a lower altitude might be a good idea to cater for the 'prolonged' emergency descent case. I always consider it in the Airbus, particularly in alternate law situations where you can't use speedbrakes and Mmo is severely reduced. Just wondering if it ever occurred to anyone else?
Your thoughts, anyone?
1)In the situation where a runway is NOT contaminated with slush/snow etc, but braking action is never the less 'poor' due to say rubber deposits, PIREPs etc, while the dry or wet runway takeoff data would cater for the accelerate/GO case, how would you cater for the Accelerate STOP case, given that you have no valid charts for it? As I see it, there will be little contaminant 'retardation' in the accelerate phase, but less than nominal braking in the stop portion from V1.
Indeed, is it something that is even considered in certification?
2)On a different note: given that jet transport aircraft, by and large have to carry out an emergency descent for depressurization within the confines of the available oxygen envelope (something like a staircase pattern in my manual) and that the certification assumes use of speedbrakes and Mmo/Vmo(correct me if I'm wrong there) what happens if you don't have them? The checklists for loss of speedbrake conditions never seem to mention the fact that a lower altitude might be a good idea to cater for the 'prolonged' emergency descent case. I always consider it in the Airbus, particularly in alternate law situations where you can't use speedbrakes and Mmo is severely reduced. Just wondering if it ever occurred to anyone else?
Your thoughts, anyone?
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1. Really not accounted for. If you had to use something to represent poor braking on the stop but little effect on the go, ice or packed snow from the "standard" contamination options would be your closest equivalent, but bitching at the airport authority would also be good.
2. Taken account of. Where we have a spoilers lost case that makes the emergency descent case not achievable with available pax oxygen, the procedure requires descent to a low enough level to assure the descent. In many cases it may not be required because the aircraft has margin to start with and you are just eating into the margin.
2. Taken account of. Where we have a spoilers lost case that makes the emergency descent case not achievable with available pax oxygen, the procedure requires descent to a low enough level to assure the descent. In many cases it may not be required because the aircraft has margin to start with and you are just eating into the margin.
