Unreliable Speed QRH procedure

Disclaimer: 

▪︎This content is Not an official document and does not represent the views of Airbus or any other aviation authority.

▪︎The information provided may be incorrect or misinterpreted and should not be relied upon for decision-making. 

▪︎Always refer to official documents and consult with a qualified aviation professional before making any decisions based on the information provided in this blog post.

▪︎The information provided in this blog post is based on personal study and review.

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UNRELIABLE SPEED MEMORY ITEM

 

there are memory items for the a320 pilots which we have to apply A MEMORY ITEM, when the flight crew has no time to refer to the ECAM/QRH/FCOM to ensure a safe flight path.

and one of those memory items, has an Unreliable speed. 

if the pilot were asked about the memory items, they might immediately say " autopilots off, autothrust off, both fds off. below thrust reduction altitude toga pitch 15.. above thrurst reduction altitude ..blabla.. 

 

but unreliable speed memory item has to be done only If the safe conduct of the flight is affected,

the flight crew should not applies the memory items just because the flight crew has an indication of unrelieble airpseed.

 

 

If we look into unreliable airspeed QRH, there are BLACK DOTs and BLACK SQUAREs. 

 

Reference only

 

BLACK DOT

If an action depends on a precondition, a black dot identifies the precondition. If the precondition appears on ECAM, it appears in LARGE LETTERS. If not, it appears in small letters.

 

BLACK SQUARE

 

When several procedures appear under the same title, a black square marks the starting point of each procedure.(The ECAM does not display black squares.)

 

 

So one of 3 precondition is "if the safe flight is impacted" condition, which is memory item.

 

 

BUSS below FL250 

 

Aside from aircraft equipped with DBUS (Digital Backup Speed/Altitude), if the affected ADRs (Air Data References) are not identified and the aircraft is below FL250, the QRH procedure will eventually lead to the use of BUSS (Backup Speed Scale).

 

There are two types of BUSS: reversible and non-reversible. The reversible BUSS has a “BUSS” button, which allows the reactivation of one ADR and enables the continued use of one ADR pushbutton.

For the non-reversible BUSS, all three ADR pushbuttons (ADR 1, 2, and 3) must be turned off to activate the BUSS.

and this action is not reversible.

 

This results in the ECAM procedure for an “ADR 1+2+3 FAULT,” which the flight crew must follow. This will also lead to the “ALL ADR OFF” QRH procedure, requiring the manual adjustment of cabin altitude.

 

 

reversible BUSS

 

With the reversible BUSS, only two ADR pushbuttons need to be turned off, leaving one ADR operational. This means the flight crew does not need to manually adjust the cabin altitude.

 

The QRH procedure for using BUSS is only applied when the aircraft descends below FL250, even though the FCOM does not specify an altitude limitation for BUSS. However, according to the FCTM, most unreliable speed indications above FL250 are temporary. This is likely why the QRH directs the crew to use BUSS at or below FL250.

 

there is ADR 1+2+3 fault ECAM with the aircrafts with reversible BUSS, when the other situation requires to turn off all ADR pushbottons. 

 

 

 

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Unreliable speed (Airbus)