Boeing Airspeed unreliable
Thread Starter
Joined: Nov 2019
Posts: 25
Likes: 0
From: Sydney
Boeing Airspeed unreliable
A quick query if I may
AIRSPEED UNRELIABLE CL calls for setting pitch attitude and thrust from tables for phase of flight. In terms of the order of things, does this imply e.g. if using the 5000 terminal area table?
Set 5000 and fly level
Set the published thrust
Await till the published PA is reached and nil further trim so therefore we have reached table speed
(Doesn’t read this way)
or
Simply set the published attitude (corresponding to the altitude table for your current altitude but ignoring level flight for now)
Set the published thrust
And allow the aircraft to climb or descend about the published table altitude whilst awaiting until no further trim needed.
In summary, when referring to the tables, is altitude disregarded whilst setting the pitch attitude and thrust for phase of flight?
Many thanks in advance
AIRSPEED UNRELIABLE CL calls for setting pitch attitude and thrust from tables for phase of flight. In terms of the order of things, does this imply e.g. if using the 5000 terminal area table?
Set 5000 and fly level
Set the published thrust
Await till the published PA is reached and nil further trim so therefore we have reached table speed
(Doesn’t read this way)
or
Simply set the published attitude (corresponding to the altitude table for your current altitude but ignoring level flight for now)
Set the published thrust
And allow the aircraft to climb or descend about the published table altitude whilst awaiting until no further trim needed.
In summary, when referring to the tables, is altitude disregarded whilst setting the pitch attitude and thrust for phase of flight?
Many thanks in advance
Joined: Dec 2005
Aviation Qualifications: ATPL
Posts: 4,998
Likes: 341
From: Hong Kong
If you're using the tables 'all the way' then you're having a really bad day. Step 1 is memory items for pitch and thrust, which keeps you safe. Step 2 is to use the QRH to set accurate values from the table for speed which will allow you to hopefully establish if one of your 3 sources is reliable. If none are reliable then step 3 calls for table values for pitch and power. In the scenario you describe when reaching 5000ft you would maintain it with elevator and trim. The resultant power setting should correspond to the desired speed, just as you would expect: In level flight if you add a bit of power, trim to maintain level flight and you'll get faster.
