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In this incident the cabin crew entered baggage compartment to find and secure a smoking suitcase. But that was in ATR-72 which has the baggage compartments on the main deck behind cockpit and aft of cabin and passage between cockpit and cabin goes through the (larger) forward compartment.

In this incident it was clearly an advantage to be able to get to the cargo. Would it also be possible in some larger planes? Is there any regulation or guideline explaining why it should or shouldn't be possible?

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    $\begingroup$ The article says the smoke was from acetone and a hairdryer but "The female owner of the suitcase reported it was a fluid to make the hair lighter." That sounds much more like hydrogen peroxide (hair bleach) than acetone (nail varnish remover). $\endgroup$ – David Richerby Nov 12 '14 at 18:53
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There are 4 classes of cargo compartments listed in 14 CFR 25.857 for transport category airplanes. The main concern with in-flight access is in regards to fire safety.

  • Class A: Crew will easily discover fire from their station (and therefore be able to suppress it as well)
  • Class B: There is a fire/smoke detection system, and access for crewmember to use a hand fire extinguisher
  • Class C: There is a fire/smoke detection system to alert the crew, and a fire extinguishing/suppressing system installed
  • Class E: For cargo-only aircraft (no passengers): There is a fire/smoke detector, and a way to shut off air flow to the compartment

So basically, there has to be some way to both detect and address a cargo fire. Class A compartments are those such as in the cockpit where a detection system is not necessary. It sounds like the ATR example would be Class B, since they had a fire indication, and the crew had access to extinguish the fire themselves.

In larger planes with cargo in the lower hold, the compartments are usually Class C, so they have a detection system and a suppression system, and in-flight access is not required. As David Richerby's answer notes, the compartment may be accessible, but that doesn't mean that crew could effectively locate or fight a fire in those areas. Especially for large cargo holds, a fire suppression system installed througout the hold is much more effective than crew members gaining access at certain locations. This also provides the benefit of isolating the main cabin from the fire extinguishing agents.

Besides fires, there are even rarer instances where cargo compartment access could be helpful. But even in that case, it was better for the plane to just come back and land to access the cargo compartment.

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    $\begingroup$ No elevator to the cargo deck like in thriller movies? I'm disappointed :( /sarcasm $\endgroup$ – yo' Nov 12 '14 at 20:53
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    $\begingroup$ In general: Class C's are underbelly holds on jets, which may or may not be accessible through say an E&E bay or a hatch from above. Class A's and B's MUST be accessible for fire extinguishing -- Class A is used for cockpit storage compartments, and Class B for the small main deck cargo compartments on regional and commuter turboprops (like the ATR-72 mentioned in the question). Class E cargo compartments are the main decks of cargo aircraft -- although the requirements for them are a-changing in the wake of UPS 6. $\endgroup$ – UnrecognizedFallingObject Nov 17 '14 at 1:33
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    $\begingroup$ @tohecz the L1011 had an elevator! $\endgroup$ – vectorVictor Nov 17 '14 at 22:55
  • $\begingroup$ I remember in the Arnold Schwarznegger movie 'Commando', he does into the cargo hold, from the back of the aircraft and escaped through the landing gear $\endgroup$ – Firee Sep 9 '15 at 13:36
  • $\begingroup$ Is Class D skipped? Or was there a legacy Class D? $\endgroup$ – curious_cat Jan 2 '16 at 16:56
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I've no idea how accurate it is but this Straight Dope thread contains confident assertions (some from people who claimed to have worked on these planes) of the following:

Cargo hold inaccessible. BAe146, DC-9-30.

Forward cargo holds accessible. 737, 747.

All cargo holds accessible. 777.

Note that, on larger planes, a lot of the luggage will presumably be in containers so getting into the cargo hold isn't necessarily useful.

This was originally posted as a comment in the hope that somebody would post something more authoritative as an answer.

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    $\begingroup$ I can confirm that the forward cargo hold on 747-100/200 aircraft is accessible in flight. To get there you pull up a small section of carpet on the forward part of the maindeck, open the hatch underneath it, and descend into the electronics bay. If you then go forward, you'll be in the compartment in which you can manually lower the nose gear. If you go aft you'll go into the forward cargo hold. There's a heavy fabric wall between the electronics bay and the forward hold that has provision for getting through it. $\endgroup$ – Terry Mar 15 '17 at 17:37

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