Parking brake and CVR test relation?

[kochu kaili]

Why is it necessary to set the parking brakes ON before doing the CVR test?I`ve experience only on the 320 but I believe its the same for most other aircraft

[chimbu warrior]

A protection feature that ensures that the erase feature can only be accomplished when the aircraft is on the ground and brakes are parked.

[kochu kaili]

I understand that the cvr cannot be erased if the parking brakes are not set.But why do we need to switch the brakes on to conduct the cvr test?
1.As pilots we are not going to erase the CVR.
2.What could happen if we did not set the parking brakes before doing the test?What would go wrong?

[EDDT]

The testing takes the CVR out of its normal operation, as all the circuits are tested and your should hear a beep from the speaker. Thats why its tied to PB-Set as well as the erase button.

1. of course. I often erase the CVR on ground, especially if we were talking about "serious issues"

2. If the PB is not set you nust dont hear the beep, and the test is unsucsessful. or what exactly are you asking?

If you want to stop it from listening while airborne, just pull the corresponding Circuit Breaker.

[vilas]

EDDT
Your DGCA seems to be very benevolent. This could get some others in trouble.

[NSEU]

but I believe its the same for most other aircraft

I don't know about Airbus, but it's not required on Boeings (737NG, 747, 747-400, 767, 777). Not sure about the 787 (?)

[kochu kaili]

EDDT

simply put, what will happen if I dont set the PB before the CVR test?

[NSEU]

https://www.scribd.com/doc/24949816/...-Communication

According to the diagrams in this file (page 227, and on), with the park brake not set and the CVR test button pushed, the CVR gets the command to generate the test audio, but it doesn't get to the speakers because a park brake relay interrupts the signal. This suggests the test tone is recorded.

Pushing the test button also stops TCAS audio reaching the speakers.

Bizarre