Overspeed aural reset switch? (747-8)

[Hardy Heinlin]

Just curious ...

On the 748, near the lower right corner of the captain's CDU, there's a pushbutton for "overspeed aural reset". Does that mean the 748 may get into overspeed more easily than other aircraft?

And because returning to normal speed may take very long the crew needs a switch to silence the overspeed siren? :-)


Regards,

|-|ardy

[Owl]

No idea about the -8 but there's an interesting case of regulatory divergence which results in it being an option on the -400.

EASA mandates that the overspeed must not be able to be silenced.

However the FAA requires a silenceable overspeed in order to "make the flight compartment environment more conducive to communication and coherent thought during a prolonged overspeed warning".

The FAA preference eventually became the default for all non EASA -400s from l/n 1276 and onwards.

[dhob]

It's an option for a dedicated switch.
Silencing the Overspeed warning with the Master Caution/Warning switch satisfies the FAA requirement.
EASA requires a dedicated switch; thus, EASA operators had to pay extra for the option.
Our 747-8's do not have the switch.

[Hardy Heinlin]

In PSX these two warnings cannot be silenced:

• Takeoff configuration
• Mach/IAS overspeed

In PSX there's currently no option to make these two silenceable by pushing the master warning reset switch.
Is this option really required on the 744 as well (not just 748)?

If so, I will implement it in the next update.

Is it also required for the takeoff configuration warning?


|-|ardy

[dhob]

Our 747-400F factory freighters are configured such that the siren cannot be silenced by the Master Warning Reset switch for the following: AUTOPILOT DISC, CONFIG FLAPS, CONFIG GEAR, CONFIG PARK BRK, CONFIG SPOILERS, CONFIG STAB. (The AUTOPILOT siren can be canceled by pushing the A/P disconnect switch a second time).

The siren can be canceled for CABIN ALTITUDE, OVERSPEED, and PILOT RESPONSE warnings with the Master Warning Reset switch.

Interestingly, the four used 747-400 freighters we purchased from a European operator were configured such that the OVERSPEED warning could not be canceled.  They were subsequently modified to our configuration prior to EIS.

[Hardy Heinlin]

Thanks.

Another question: I see, for the autopilot, your airline uses the siren instead of the wailer. I noticed that in some videos. In PSX the autopilot always gets the wailer, never the siren. I guess this should become another option. Is that another FAA/EASA thing?

[Owl]

The options for the AP disc are either:

Siren - inhibited (i.e. wont sound at all if pushed quick enough) with double push.

Wailer - minimum fixed length aural, can be silenced with second push after approx. 1 sec, to meet EASA requirements.

If you're interested I can list all the retrofittable options I'm aware of that aren't available in PSX, at least those with sufficient documentation anyway.

Owl

[Hardy Heinlin]

Yes, please. Can you list them?


Thanks,

|-|ardy

[Hardy Heinlin]

If you're interested I can list all the retrofittable options I'm aware of that aren't available in PSX, at least those with sufficient documentation anyway.

I hope there aren't too many :-) Is it possible to estimate the number approximately? 10 ... 50 ... 100?


|-|ardy

[Owl]

Sorry been a bit busy I'll get round to it soon, if I had to guess I'd say maybe 25-30 or so. Some probably wont pass the triviality check but I'll just list them all and leave that up to you. 

[Hardy Heinlin]

The FAA options for the silenceable overspeed alert and
the silent A/P disconnect logic using the siren instead of the wailer
are now available in PSX update 10.168:

https://aerowinx.com/board/index.php/topic,4191.0.html


|-|ardy