Think how much time and effort they could have saved just putting their shitty food directly in the waste disposal tank. Way better than running it through people first.
[QUOTE=Richard Pearse]
We can even depart with an unserviceable engine! Not with passengers, but consider the case where we have a broken starter motor. We can legally take-off on three engines, perform an air-start of the forth one, land, load the passengers with the dodgy engine idling, then depart. It’s not something I’ve heard of being done but there is a procedure for it. How would that feel as a passenger, being told that the aircraft basically has to push start one of its engines ;)?
[/QUOTE]
I’m assuming this is only meant to be done if the APU is kaput and a start cart isn’t available, so the procedure exists for the sake of “and what if…?” completeness.
As a security analyst who occasionally needs to think of the unthinkables, I’m happy that you have this procedure in writing. 
Nope. It’s there for when the engine’s starter motor is kaput. Neither APU, nor start cart will help you then. And it’s only available on 4-engine aircraft.
There’re also procedures for the automatic starting system being inop and another for the backup pilot-controlled manual starting system to be inop. In that latter case a mechanic controls the start using a wrench on some valves & switches inside the open cowling while the engine cranks up and runs. Talk about scary and bone-vibratingly noisy, especially up on a rickety workstand next to a tail mounted engine! :eek: Better them than me.
As RP said …
HQ and the FAA already decided on the gross parameters of what we pilots or local maintenance techs are allowed to bypass and the mitigations if any required.
If maintenance isn’t available I’m experienced and trained enough to assess how the actual situation fits into the various buckets of allowed discrepancies. And if I see something that seems to have excess loose ends or unknowns compared to the cut-and-dried textbook case, I’m fully empowered and encouraged to stop the show until we can get it fixed even if that means a cancellation and 250 hotel rooms in Bangor or wherever.
And regardless of any other eyes on the situation before we go or cancel or wait for repair I get to have a conference call with Maintenance HQ & Pilot HQ so we have a cross-check on our collective understanding of the guidance and the actual situation on the aircraft.
Specifically to toilets, as long as there’s at least some units operative appropriate to the duration and passenger headcount we’re not too concerned that a problem could snowball enroute. It rapidly becomes a public health issue if there are zero toilets. OK for small aircraft on short flights. OTOH …
About a month ago I read in our weekly recap of “stuff happens out there” about a 777 that was just entering the Atlantic when all toilets failed so they reversed course and diverted to someplace with appropriate maintenance support. And we bought 300 hotel rooms for 300 pissed off people who got to their destination a day late after it was fixed. But at least nobody was spreading dysentery far and wide while shitting uncontrollably in the aisles.
The scenario above is not so unthinkable. It’s happened to me a few times. The first time the APU wouldn’t start as we taxied in at a remote mine airfield with no ground power cart so we shut down engines 3, 2, and 1 and unloaded the passengers. Then we used engine 4 to power the start of engine 1 and shut number 4 down so we could unload bags, refuel, and load the bags for the next leg. Then we start 4 and shutdown 1 so we can load the passengers. Then we start the rest of the engines and go. It is known as the “flip flop” and requires careful risk management.
The second and third time the APU failed after we had shut down engines, but the mine had a battery cart. This is simpler. We unload and load the ship while it’s dead, then do as much cockpit prep as possible on the internal battery. Once bags and fuel is loaded we start #4, complete the cockpit prep on engine generator power and load the passengers. Then start the remaining engines using #4 as a power source and get going.
The forth time, the APU failed after engine shut down but when we attempted a battery start the battery didn’t have enough juice and we were stranded until a spare aircraft could come and rescue us.