Posts by user "EXDAC" [Posts: 27 Total up-votes: 55 Pages: 2]

tdracer posted - " Commanded engine cutoff - the aisle stand fuel switch sends electrical signals to the spar valve and the "High Pressure Shutoff Valve" (HPSOV) in the Fuel Metering Unit, commanding them to open/close using aircraft power. The HPSOV is solenoid controlled, and near instantaneous. The solenoid is of a 'locking' type that needs to be powered both ways (for obvious reasons, you wouldn't want a loss of electrical power to shut down the engine). The fire handle does the same thing, via different electrical paths (i.e. separate wiring)."

Search this thread for "HPSOV" if you need confirmation of the quote.

Note there are two shut off fuel valves per engine - the HPSOV and the Spar valve. Both stay where they are if power is lost.

Wouldn't "fail safe open" imply that the valves would open on loss of control signals or power. They don't. They stay just where they were before loss of power or control signal. If I understood tdracer's description of the HPSOV it can only be open or closed. That's not true of the spar valves which are motor driven and can stop in any intermediate position if power is lost.

The only way this is relevant to the accident is if the shut off valves had been commanded closed and then power had been lost. The valves would not open.

Thanks for those two quotes. I had only used the first one in my previous reference to HPSOV operation. I have only been involved with Boeing spar valves and not any HPSOV. However, I do not see that spring shutoff when less than 300 psi is in conflict with staying open if electrical power is lost.

Hopefully tdracer will provide more detail if/when he re-joins the discussion.

I am not aware of any requirement for a DFDAU (or equivalent) to store any data. I say "or equivalent" because in B717 the DFDAU is not an LRU. It is a functional partition of the VIA.

It's not clear to me that 787 EAFR even requires an external DFDAU. The GE EAFR does not -

"Provides Flight Data Acquisition function of ARINC 664 p7 data parameters – No need for a Digital Flight Data Acquisition Unit (DFDAU)."

ref https://www.geaerospace.com/sites/de...rder-3254F.pdf

The requirements I have seen indicate that RIPS is applicable only to CVR or the CVR function of an EAFD. If you are aware of any requirement for RIPS to support flight data recording would you please provide a reference.

FAA requirements and the discussion/changes that resulted from the initial NPRM here -

https://www.federalregister.gov/docu...er-regulations

I was looking for connector pin data but only found this:

"The front panel contains one connector, J1, and a grounding stud. • J1 provides the main EAFR power supply, Aircraft Data Network, Ethernet Channels A and B, analog audio input, input and output discretes, and other miscellaneous signals."

If RIPS is external and the GE EAFD only has a "main power supply" pin then I agree it seems likely that the flight data function is powered by RIPS.

For RIPS to power only the CVR function I would have expected to see separate main power and RIPS power input pins. I could not find any data except the two page marketing brochure which is not definitive.

Glide slope is expressed as an angle in degrees. L/D (lift/drag) is expressed as a ratio, such as 13:1, which is the ratio of distance flown to height lost. Glideslope = tan⁻\xb9 (D/L).

So, 13:1 is equivalent to 4.4 degrees.