You see this in movies all of the time. Someone has hidden a bomb, or snakes or terrorists or something in the cargo hold and the hero opens a hatch and climbs down to take care of it. Sometimes there is even an elevator you can take to get there.
Yet you never see these hatches in real life, at least not in my experience. And it would seem like a great security risk to have easy access to all the stuff that they wouldn’t let you carry on as cabin luggage.
Not in a DC-9-30 which I worked on back in the day. I believe that’s true for the updated MD-80 series of the same aircraft.
The cargo hold in the DC-9 is pressurized, but doesn’t have direct airflow into them. There are little valves between the roof of the cargo compartments and just under the floor of the cabin to allow pressure to equalize, but the air could get stale in the cargo bays. It’s not directly heated either and can get cold in them.
There is a panel in the cockpit that allows someone to go down into the E&E (electronics and environmental) compartment. This compartment is on the save level and just forward of the cargo compartment, but there’s no way to get from the E&E into cargo compartment.
They are definitely pressurised. It would be difficult not to pressurise the cargo hold as it would place a lot of stress on the floor between the cabin and the hold. It is much better to use the entire structure of the fuselage as the pressure hull.
As for getting down there, you definitely can’t in the BAe146, and I would be very surprised if you could in other small-medium airliners. As for B747, A380, and similar, I doubt you’d be able to but I don’t know. You can get in to the cargo bay in the Dash 8 as it is behind a bulkhead at the rear of the passenger cabin and the bulkhead has a door.
Yes you can depressurise the cabin. You wouldn’t do it to chill the snakes though, you’d do it to starve them of oxygen.
Certainly; at the very least you could use something to punch a hole in the skin of the plane or break a window. The real question is can you do so in a controlled fashion that lets you re-pressurize the plane afterwards.
Yes you can. You can set the pressurisation to manual mode and open the outflow valves which are valves in the fuselage that control how much air is let out of the cabin. You can control the rate at which the cabin depressurises so that ears and sinuses aren’t traumatised. Once the snakes are unconscious and restrained you can put the pressurisation back to auto and the cabin will “descend” back to where it should be.
The avionics bay on the 146 is accessible from a hatch in the flight deck and a hatch on the right side of the nose. It also has the benefit of sitting low to the ground so you don’t need a ladder to get to the avionics bay.
The hydraulic bay and cargo bays on the other hand are only accessible from the outside.
I was in the very back row of a DC-10 & the pilot came back, went through a door / hatch that looked like a door and I could what appeared to be the outer skin. Wind noise also became much more intense. Was in there about 5 minutes, came out & talked to the stewards, gave my attentive look a “Do not say a word to anybody.” & went back up front.
( We had an inflight situation that the crew in the back & I in the last row knew was not normal. We heard it go [not normal] )
Went on to the next destination and we changed planes. Not sure if we were supposed to or if it was because of what they found. They did not let me be in the loop.
The 777 has an access hatches to both the forward and aft cargos. The forward hatch is just aft of the flight deck door, the aft access is between doors 3R and 3L. The 737, the plane I have worked on the most in my 30 years at Boeing only has an emergency access panel to the forward cargo. The gain access, the carpets would need to be pulled up and possibly a seat moved to gain access. It is something that would be difficult, if not impossible, to do while the plane is in the air.
This. A large flat surface (like the floor of a 747’s passenger deck) that’s resisting a pressure differential is subjected to bending loads and must be built rather thick and rigid (and therefore heavy). A curved surface (like the skin of a 747’s fuselage) that’s resisting a pressure differential is subjected to simple tension and can do the job with a lot less material/weight. ISTR the cabin is kept at a “pressure altitude” of about 5,000 feet, i.e. the internal pressure is about 11 psi. At 35,000 psi the ambient presssure is just 3.5 psi, so the inside/outside pressure differential at cruise is about 7.5 psi. Assuming a 747 fuselage is ~20 feet wide, a full-width strip of fuselage floor measuring 1 foot from front to rear would be subjected to 21,600 pounds of force (in addition to the weight of passengers and seats) if the cargo area were not pressurized. Think “seven Honda Civics.” The floor ain’t that robust.