BLOW OUT PANELS

[piratepete]

Can someone educate me as to the purpose of these items and what might cause them to depart the (in this case) the leading edge, all 3 of them and where is the reference? Thanks Peter.

[NSEU]

Which aircraft?

[JammedStab]

Bleed air leak. Happened to one of the engines on one of our 727's a few years back. Not sure about leading edges though. However, many do use bleed air for anti-ice.

[lomapaseo]

Can someone educate me as to the purpose of these items and what might cause them to depart

Lots of duct work in planes carrying pressures above ambient (engine bleed air and ant-ice are examples). If one of them ruptures and discharges into some compartment you don't want that compartment to rip open or tear at rivet lines.

The idea is to assume possible levels of over-pressures from malfunctions and ensure that an easily replaceable or fixable item gives way first.

as for the op specifics, I have no idea

[mustafagander]

Another thing blow out panels do for the maintainers is to show clearly what area has the leak.

[FE Hoppy]

WHAT TYPE?

tech q's should always include aircraft type if you want an accurate answer.

LE ducting could be bleed air or wing anti-ice. The regulation of pressure is done by different valves depending on TYPE!

[piratepete]

Its a 767-200 SORRY TO YELL, old habits etc

[NSEU]

Bleed duct rupture would be a good bet, but severe and unusual turbulence and buffet inspections in Chapter 05-51-04 of the Maintenance Manual also mention blowout doors (perhaps because of structural flexing).

[TURIN]

Now the question has been answered I feel I can make comment.

Pete,

Please can you desist on posting thread titles in all capitals. You have demonstrated that you can write correctly in the body of the thread so please do it in the title!

That's all.
Cheers

Why is it bad practice to post a title in capital letters?
Genuine question. I do not understand the reason for this.
Thanks.

[Basil]

Do we now have blow-out panels in the cabin floor, empennage aft of the aft pressure bulkhead and on the fin and tailplane? They're all components which could sustain catastrophic damage due rapid decompression.
My hearing isn't all that good and I find the capitals help a bit ;)

[lomapaseo]

Some of us only speed read for titles of interest and caps and bolding makes it easier :ok:

but don't do this in the text except to a very few places

[Old Fella]

A classic example of where blow out panel may have been advantageous is the loss of the JAL B747 which suffered a rupture of the rear pressure bulkhead (due to a previous faulty repair). When the bulkhead ruptured the vertical stabilizer was pressurized and failed, taking the hydraulics to the rudder actuators with it. Total loss of hydraulics resulted which in turn led to loss of control of the aircraft.

[_Phoenix]

Doesn't matter the type, the only purpose of a blow-out panel is to blow... at a predetermined threshold of pressure differential, by opening of a venting area for relief of dangerous stress in the structure.

[piratepete]

Thanks OLD FELLA, my other concern is what about the actual panels coming off over a highly populated area and hurting someone on the ground? I guess its a compromise but it does bother me that these things travelling quite fast hit someone.A few years back I do recall a Cathay A330 or 777 engine panel of some kind falling off on departure from DMK and the quite large thing fell into a car engine section while someone was driving on Chang Wattana Road west of the airport.No one was hurt, but pure luck.Peter.

[triploss]

A classic example of where blow out panel may have been advantageous is the loss of the JAL B747 which suffered a rupture of the rear pressure bulkhead (due to a previous faulty repair). When the bulkhead ruptured the vertical stabilizer was pressurized and failed, taking the hydraulics to the rudder actuators with it. Total loss of hydraulics resulted which in turn led to loss of control of the aircraft.
I don't see how that would help in this case: a blowout panel for the bulkhead (or anywhere in the cabin) would mean that the cabin can't stay pressurised.

I.e. if the bulkhead blew at pressure difference X: during flight / once you're cruising you're expecting a pressure difference Y that will likely be larger (Y >= X). But to prevent bulkhead blowout you'd need a blowout panel that releases at a pressure difference Z, which has to be smaller than X for the panel to blow before the bulkhead does (i.e. Z < X, and Y >= X). Thus Z <= Y (blowout panel pressure difference less than crusing altitude pressure difference), so the blowout panels go on every single flight.

Note: I'm not qualified as a pilot or an aerospace engineer, I could well be missing something obvious here.

[Old Fella]

PP, I think given the thousands of flights daily worldwide such occurrences are rare. Like anything else where there is the "human element" involved oversights will happen and incidents will follow.

[Old Fella]

Triploss, I was not suggesting a "Blow-out Panel" in the pressurised hull. If blow out panels had been incorporated in the leading edge of the vertical stabilizer, or the structure itself, they may have prevented the failure which occurred when they became pressurised with air escaping from the cabin via the failed pressure bulkhead. At the altitude the aircraft was flying the pressure differential (cabin pressure v's ambient pressure) would have been around 9 p.s.i. which does not sound a lot, but the vertical stabilizer is not designed to withstand internal pressure. Hope this explains my previous comment a little better.

[lomapaseo]

Triploss, I was not suggesting a "Blow-out Panel" in the pressurised hull. If blow out panels had been incorporated in the leading edge of the vertical stabilizer, or the structure itself, they may have prevented the failure which occurred when they became pressurised with air escaping from the cabin via the failed pressure bulkhead. At the altitude the aircraft was flying the pressure differential (cabin pressure v's ambient pressure) would have been around 9 p.s.i. which does not sound a lot, but the vertical stabilizer is not designed to withstand internal pressure. Hope this explains my previous comment a little better.

This is probably a lot more complicated given that the blow-down rate through a breech, yet to be defined, would need to be taken into account along with any avenues of escape of the air behind the bulkhead.

I do suspect than the loss of structural support of the fuselage at the aft bulkhead might have had a greater contribution and left the vertical to torque off in the airflow.

Blow-off panels only work where the rate of rise of the pressure is defined.

[KenV]

A classic example of where blow out panel may have been advantageous is the loss of the JAL B747 which suffered a rupture of the rear pressure bulkhead (due to a previous faulty repair). When the bulkhead ruptured the vertical stabilizer was pressurized and failed, taking the hydraulics to the rudder actuators with it. Total loss of hydraulics resulted which in turn led to loss of control of the aircraft. Maybe. Maybe not. It's not known exactly what caused the loss of the vertical fin. However, the vertical fin structure is much stronger than the tail cone structure. In all probability, the tail cone would depart and vent the aft fuselage area before the vertical fin could rupture from over pressurization. However, the decompression was powerful enough to blast large chunks of the pressure dome aft into the aft fuselage area. It is likely that the large chunks of flying metal caused structural damage to the vertical fin attach/support structure which then failed under the aerodynamic loads on the fin. Certainly they severed all four hydraulic systems that passed through the aft fuselage area. The combination of loss of the fin and all flight control systems made the aircraft uncontrollable. It was a miracle the flight crew kept the aircraft in the air for 32 minutes. Numerous simulator runs were done simulating the damage and with multiple very experienced flight crews at the controls. None came close to the 32 minutes achieved by the actual flight crew.

[tdracer]

Thanks OLD FELLA, my other concern is what about the actual panels coming off over a highly populated area and hurting someone on the ground? All the blowout panels I'm familiar with are designed to NOT depart the aircraft - typically hinged. Parts departing the aircraft is considered a bad thing (even in a failure condition), and in the case of the engine and wing, there is the risk of the parts hitting and damaging the tail.

With regard to the JAL 747, a 20 ft. diameter pressure bulkhead ruptured - I seriously doubt pressure relieve doors would have made any difference what so ever.