Why can't you open the cabin baggage door past 40,000'?

[tuna hp]

I was reading through some manuals for the Falcon 7X and G550, and for the 7X there was an outright prohibition on opening the door at higher than 40,000', while in the G550 there were instructions that at over 40,000' you must open the door for a maximum of 5 minutes at a time.

What is the reasoning for these regulations?

Also, official cabin length specifications for these aircraft are 39'1" for the Falcon and 50'1" for the Gulfstream. I suspect, but cannot confirm anywhere, that gulfstream includes the length of their baggage compartment but that Dassault only includes length to the internal baggage door. Is that true?

[Gulfstreamaviator]

If there is a fan seperation, then the disc might enter the baggage bay.

The baggage door acts as a supplemental pressure bulkhead.

So assuming the door is in place, (not always a certainty on a G550) then the emergency descent can be completed within the certification limits.

It also might have some relevence to ERPOS, but I can not find that reference, sorry.

[tuna hp]

So its not that pressure bulkhead at the rear of the baggage compartment cannot sustain the same pressure as the rest of the pressure vessel, its completely because of the risk of fan separation?

Is this a regulation that is taken very seriously in flight or would most private operators not think twice about going into the baggage compartment regardless of altitude?

I would think that fan separation would be more likely at lower altitudes when you have much more energy running through the engine, but what do I know.

[smallfry]

Yes, during our initial and re-currents it is explained as being due to fan (blade) separation damage control.
Our FA's and Pax regularly go into the hold at and above FL400. - Which is totally allowed.
We get a Blue CAS message, and if the door remains open for 5 minutes we get an Amber CAS message. Usually the Door is not open for that long. If we were restricted to not being able to use the hold door above FL400 we would seldom be able to use it, most of our trips over an hour are above FL400.
In answer to your other query, I am trying to find the document that has the diagram on, but I recall that the G cabin length is to the back of the aft lav, so not including the baggage compartment. BUT until I find it (or measure it myself!) I cant swear to it.

[tuna hp]

If this diagram is accurate then it shows that the 50'1" includes the baggage area

http://img6.imageshack.us/img6/261/intgulfstreamgv.jpg

I can't find a similar diagram for the Falcon.

Do you think that Falcon operators avoid opening the door, following regulations?

[tuna hp]

All right this pretty much confirms the cabin lengths for me. I still can't find a diagram of the 7X but I do know that Dassault advertises the Falcon 900 cabin length at 32'3" and I was able to find this diagram:

http://img4.imageshack.us/img4/7740/intfalcon900.gif

So Gulfstream and Bombardier figure cabin length including the baggage holds and it appears that Dassault does not. Out of all the websites that allow you to make comparisons between aircraft specifications, I've seen them all use the official numbers form the manufacturers without a single one that mentions that comparing those cabin length numbers is apples and oranges. I don't know if Dassault does this because its their tradition or because the regulations don't let you access the baggage at all above 40k... I don't know but it seems kind of stupid of them from a marketing perspective.

[Arkwright]

Interesting.....I fly a 900, and was told on both the initial and recurrent course that the reason for the limitation was the "time of useful consciousness" above FL400.

If depressurisation were to occur whilst someone was in there, they wouldn't have enough time to get back to an oxygen mask before passing out.....

Anyone else heard this reason???

[His dudeness]

don't know but it seems kind of stupid of them from a marketing perspective.

Stupid? I think its just honest. Cabin lenght should be cabin and not cabin plus baggage compartment.

[tuna hp]

I looked into what these factors are for the Falcon 2000:

The official cabin length for that plane is 31', and it turns out that this number INCLUDES the baggage hold while the 900 (and I'm guessing the 7X) does not. Also, from reading some of the documents on Smart Cockpit, I can't find anywhere it mentions a limitation on baggage hold access during flight for the Falcon 2000. It seems that you can enter and exit whenever you want. Maybe because the baggage compartment is completely in front of the engines, whereas it is about parallel with the engines in the 900 and 7X?

I don't understand the point of that regulation. If the engine explodes and slices through the fuselage, you are in trouble regardless. Even if the door happens to be open at that moment, I'm sure that the door could be engineered to be automatically slammed closed by the suction of the escaping air. Yes, mandate that you have that secondary pressure bulkhead and that the door is springloaded to automatically close in order to encourage it to be closed whenever possible. But I wouldn't think twice about going in to get a bag knowing that my only marginal risk is of an engine exploding, which probably is risky enough to my life even if I'm not in the baggage hold.

[galaxy flyer]

tuna hp

The certification standard is there not because someone in the hold would be injured or run out of useful consciousness; it is there to protect ALL the plane's occupants. In these planes the engines are far enough forward, that an uncontained failure would damage the pressure vessel, hence the reason the interior baggage door is a secondary pressure door. The engines on the Bombardier products are located so that the plane of a turbine blade failure is AFT of the aft pressure bulkhead, hence the lack of a restriction on those types.

GF

[tuna hp]

@ Galaxy Flyer

I understood that. I was just conjecturing that the risk of blade separation seems very low and that as long as your regulations force you to have that secondary pressure bulkhead and to enter it sparingly, it seems pretty safe. From what I've read online, blade separation has been called "extremely rare" and the most rare of the named types of engine failures. Further, it would most often happen during climb.

So I was trying to say, maybe if the regulations still required you to have the secondary pressure bulkhead, and to have the door be loaded to automatically close, and to have an indicator go on in the cockpit when the door is opened, and to prohibit cabin furnishing from being installed in the baggage area, and to not enter the baggage hold during climb and descent: basically regulations that would naturally encourage the door to be closed as much as practical, that it would still be pretty safe.

For example, I would like to hear the reasoning behind the Gulfstream's toothless requirements. "No more than 5 minutes at a time" means that you could technically be compliant with that regulation by repeatedly going into the hold for 5 minutes and stepping out for a second to close the door. Is it because fewer blades overlap with the hold? Is it because of the reliability record of their Rolls Royce engines? Is it because they have more clout with regulators, so they could make sure that whatever the regulation was, it would allow them to market their plane as having a fully accessible baggage hold?

[Fossy]

I don't know for the G550 nor the 7x, but if i'm not wrong, for the F900 it is also restricted due to that there is a pressure diff between the cabin and the cargo above FL35.

[tophe]

For the F900 EX, it's part of the limitations: access in the bag compartment is prohibited above FL410 and the door must be closed and latched for any ops above that level.