PPRuNe Forums - View Single Post - Ethiopian airliner down in Africa
View Single Post
Old 6th May 2019, 01:39
  #4966 (permalink)  
737mgm
 
Join Date: Apr 2015
Location: Europe
Posts: 16
FCTM on unreliable airspeed

Originally Posted by User7861 View Post
Excuse me if this was already mentioned before, but I have to ask:

Nobody seems to be disturbed about the fact that the Unreliable Airspeed memory items include two performance settings only, and none of those are suitable for an initial climb after take off.
80% 10 degress pitch is the one with flaps extended and gear up. Starting actions at 400 AGL would mean that somewhere around 1000' these values would be set if I happened to follow the memory items without thinking.
So then what? What about high terrain and MSA?
Why is there no initial thrust and pitch setting for take off?
My personal game plan would be to keep the take off thrust and an initial pitch somewhere 14-16 degrees up until MSA or in case of VMC to an altitude where I'm absolutely sure that there will be no terrain threat, then set the 80% 10 deg.
Can anybody here show me what am I missing? Is there any of you here, who would consider setting that pitch and power right after take off? Is there even any data about the actual climb rate at MTOW for that setting?
A legitimate question that I have been asking myself as well. Adding to what other posters have said, you can find answers in the 737 flight crew training manual:

“Memory items for target pitch and thrust must be accomplished as soon as it is suspected that airspeed indications are incorrect. The intent of having memorized pitch and thrust settings is to quickly put the airplane in a safe regime until the Airspeed Unreliable checklist can be referenced. The memorized settings are calculated to work for all model/engine combinations, at all weights and at all altitudes. The flaps extended settings will be sufficient such that the actual airspeed remains above stick shaker and below the flap placard limit. The flaps extended pitch and thrust settings will result in a climb."

Accordingly setting 10° pitch and 80% N1 will result in a climb at all weights. If you have a look at the departure chart that ET 302 flew you will see that terrain was not a factor for them for at least 40NM if they continue on runway heading. Also they had good visibility. Therefore setting these values would not have been a problem. However as you said, it is also an option to keep the TO thrust setting a bit longer and the pitch atitude at 15° in order to climb quicker to an altitude where you feel more comfortable. Nonetheless you have no guarantee from Boeing then that you will not reach flap placard speed at some point. If terrain is actually a factor that is a risk I would be willing to take and as 737driver said, the best option then would be to fly your company's engine out procedure.
737mgm is offline