"Fail safe" ...MarcE wrote: ↑17 Jun 2024, 16:32Because every failsafe system can fail. I don‘t recall what exactly happened to Scott‘s Aerostar or if he even shared the details but I believe to remember that one if the main gears was stuck retracted and that they decided a belly landing was safer to do.
Almost as good a brochure term as "maintenance free". Anyways, having only studied Aerostar from books and pictures, basically, never having seen one properly up close and throughout, there are several areas where my 'distance learning' impressions of the design are not necessarily all that convinced. All that only serves to make it unique and interesting in the sim, of course! But if I had to encounter one in real, such things would make me suspicious at first instead (of course, these impressions often prove false in real, erring both ways sometimes).
One of those areas of my suspicion is the landing gear.
First of all, it does not appear there are any direct means for alternate extension. To get the landing gear fall free when hydraulic pressure is lost, well, one must lose the hydraulic pressure. You could make that happen, by either stopping the right-hand engine OR, if you want to keep that running, closing an electrically operated shutoff valve in the system, a move which would quickly destroy your now dry-running engine-driven hydraulic pump. One would also have to disarm the auxiliary pump, if installed. AND thereafter, one must cycle the flaps until the accumulator pressure is depleted. Which would mean you also lost control of your flaps. A separate isolate & dump valve for alternate gear extension would have been relatively easy to accomplish.
The gear itself appears unnecessarily complicated for such aircraft, while not particularly robust in mechanical design. In particular, how the main gear door sequencing is accomplished makes me raise my eyebrows and whisper the word 'why'. I am not going into details of this all now, but perhaps later on if I could make some illustrations. I don't know really if this is causing much or any issues in reality - it can be a sound system in practice, but it seems a dubious one in theory.
Speaking generally, aside anything getting broken or stuck mechanically, standard failure modes common to such hydraulic systems apply here as well. For instance, the fluid needs to get out from the side of the actuator piston it is extending towards (these are dual acting actuators). It is possible, just to give one example, that debris in the system (pieces of damaged packing or whatnot) would block the return path, hindering proper movement.
The list would be a long one, lots can go wrong with apparently fail safe systems.
-Esa
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