BFCM System Details / Dual Hydraulic Failure Controllability

[Ludl0w]

I've been flying the F-14 (mainly the B) extensively in scenarios involving large amounts of AAA and AA. In these scenarios, there have been many times where I've been hit and suffered dual hydraulic failure (in both the FLT and COMB systems) but still had one or both engines operational. As expected, the BFCM always turns on when both systems drop below 2100 psi. Most of the time, I will have control over the tailplanes and rudders as expected, and will be able to limp home. However, I will occasionally have a situation where I do not have control over the tailplanes and rudders, the EMER FLT flags (both HI and LOW) for the BFCM on the HYD PRESS indicator will both be off, but the BFCM electrohydraulic pump will be audible.

My first question is whether or not my understanding of the BFCM and backup flight control system in general is correct? My understanding being that the BFCM and backup flight control system is a separate hydraulic loop. Operating under this understanding, I'm assuming in the situations where I did not have control were due to the loop suffering a leak and loss of pressure (the BFCM presumably getting power since its audible but running dry). But again, I'm not sure if my understanding of the system is correct.

My second question would be regarding the outboard spoilers. In most of the dual hydraulic failure situations where I also don't have tailplane or rudder control (presumably being a failure of the backup flight control system), I will still retain outboard spoiler control. My outboard spoilers actually seem to be the lowest failure-rate flight control system. This kind of makes sense if my understanding of the outboard spoiler system is correct. That understanding being that they are also on their own hydraulic loop that is independent of the main hydraulic systems (FLT and COMB) and of the backup flight control system. Is this understanding correct? And if so, is this system fully modeled yet as far as the damage-model is considered? Because I can only remember ever losing the outboard spoilers in dual-engine failure scenarios, but never when extensively damaged with one or two operational engines.

My third question is whether or not the F-14A and F-14B NATOPS that contain information on the aforementioned systems are declassified or available and if they are, if anyone might know where I can find one where the foldouts / diagrams are legible so I can answer these questions for myself. Because I may or may not have seen one that may or may not have had foldouts / diagrams for the following systems, and they may or may not have been pixelated beyond legibility .

Edited February 16, 2023 by Ludl0w

[The_Tau]

Focusing on Hydraulic System 

[RustBelt]

The problem is most of the important Hydraulic bits live along the inside of both nacelles. So a hit in the rear center tends to do a lot of system damage. 
 

They’re backup systems for common maintenance style failures. They aren’t really meant to backup getting a MANPAD or hand full of HEI round up the tunnel. The pumps may still be intact, but the reservoirs don’t work so good full of holes. 

[Ludl0w]

@The_Tau Excellent video. Your explanations are so clear, and the diagrams / graphics are incredibly helpful and intuitive. You answered all my questions! I actually have more questions now, but only because I understand the system so much better now thanks to your video.

[Ludl0w]

@RustBelt Still, the F-14 has a lot of redundancy for a jet aircraft of its time. Even if the systems were implemented primarily for maintenance-style failures. In the scenarios I described where I take battle-damage, I am often able to limp the bird back and land her, due solely to the redundant systems engineered into the F-14.

[RustBelt]

Oh yea. It’s robust.