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DC9 Tail Cone Evacuation

Mon Jul 26, 2004 3:21 am

Does anybody know if when the tail cone of a DC9 or equivalent is jettisoned for an evacuation, can it be attached or is the aircraft then effectively written off?


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Starlionblue
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RE: DC9 Tail Cone Evacuation

Mon Jul 26, 2004 3:59 am

It is reattached, or more likely the part is sent back to Boeing or written off and a new part fitted.

Many MD-81/82s with the original pointy tail have been retrofitted with the screwdriver tail. I think you'll find that if there is no damage/buckling/cracking of structural members, most airframe parts are not so expensive to replace as to require writing off the airframe.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
4jaded
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RE: DC9 Tail Cone Evacuation

Mon Jul 26, 2004 6:06 am

It is my understanding that this part is designed to jettison from the aircraft in an evacuation. Like other emergency devises like slides there has been countless inadvertant deployments over the years. I am certain that when Douglas developed this aircraft and this feature they were aware of the
ooops factor. In most cases I am confident that it should only require an inspection before it is attatched back onto the airplane.
 
Dalmd88
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RE: DC9 Tail Cone Evacuation

Mon Jul 26, 2004 3:55 pm

The tail cone is a composite part that usually needs repair after a deployment. They are interchangable between airplanes so spares are not a problem. We take them off during the overhaul visit.
 
SafetyDude
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RE: DC9 Tail Cone Evacuation

Mon Jul 26, 2004 9:48 pm

Does anybody know if when the tail cone of a DC9 or equivalent is jettisoned for an evacuation, can it be attached or is the aircraft then effectively written off?
Almost everything on an aircraft can be replaced. For the tail cone on the DC-9, the plane would not really be a good buy if millions of dollars are lost when a hundred dollar item falls off.  Big grin

-Will
"She Flew For What We Stand For"
 
broke
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RE: DC9 Tail Cone Evacuation

Mon Jul 26, 2004 10:46 pm

The tailcone on the DC-9 is mostly fabricated from fiberglass. When it comes off, either intentionally or inadvertently, it usually gets a ding (surfing term) at its pointy end which requires a minor repair before being reused.
I think the MD-80 boattail tailcone is also composite and would get dinged at the lower edge of the boattail when ejected.
The tail slide is mounted at the edge of the metal structure just forward of the where the tailcone comes off and it is deployed manually after the tailcone is out of the way.
There is a narrow catwalk, that gives a tricky access to the slide, with heavy canted curved beams that carry the empennage loads into the fuselage overhead. It is very easy to fram your head into one of these beams. Ouch, ouch, ouch!! The catwalk starts over the APU shroud and the compartment is usually very smelly from skydrol. Experience talking.
 
AA717driver
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RE: DC9 Tail Cone Evacuation

Tue Jul 27, 2004 1:11 am

Broke--I thought "ding" was an aviation term. Smile

I was always leery when doing walkarounds on the -9/-80/717 after the instructor told me the tailcone weighs a couple hundred pounds! Talk about a ding!

Anyway, you never know when a mech or FA will be trying to deploy the aft stairs on a -80 and accidently jettison the tailcone. Insane TC
FL450, M.85
 
broke
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RE: DC9 Tail Cone Evacuation

Tue Jul 27, 2004 1:39 am

My first experience with someone dumping the tailcone when attempting to lower the ventral airstairs occurred on a DC-9-50 that we were modifying for introduction into Eastern's fleet. Someone inside the plane yelled out to lower the airstairs and my compatriot pulled the wrong handle!! He reached out without really looking at what he was reaching for. His first name was Henry and from then on, the external tailcone jettison handle was known by us as the "Hank" handle.
 
SlamClick
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RE: DC9 Tail Cone Evacuation

Tue Jul 27, 2004 11:56 am

It's been said that the real reason for the screwdriver tailcone is so it won't roll so far when it is accidentally dumped.

I used to be able to claim that the only time in my whole career I ever had lost comm was in a DC-9 when the last bonding cable to the tailcone finally broke. We got in a high altitude stratus layer and the ice crystals brushing down the ungrounded tailcone caused a squeal in all the radios that did not go away until we left the clouds. Needless to say it took them a while to find the broken bonds in response to our writeup, but it fixed the problem.

I can't say it was the only time anymore because that happens to the Airbus every time it gets in heavy clouds at altitude.
Happiness is not seeing another trite Ste. Maarten photo all week long.
 
DL_Mech
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RE: DC9 Tail Cone Evacuation

Tue Jul 27, 2004 9:12 pm

The MD-90 has a different tailcone from the MD-80. There is a small nitrogen bottle installed inside the tailcone with an exhaust port that "blows" the tailcone to one side during deployment.
This plane is built to withstand anything... except a bad pilot.
 
miamiair
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RE: DC9 Tail Cone Evacuation

Tue Jul 27, 2004 10:03 pm

First of all, the tailcone does not weigh a couple hundred pounds.

The DC-9 tailcones have an aluminized flame spray coating for the RF problem.

They are damaged more from hangar rash than operational use.
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FBU 4EVER!
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RE: DC9 Tail Cone Evacuation

Wed Jul 28, 2004 4:25 am

The original DC-9/MD-80 pointed tailcone weighs 48 kgs. It is designed so as to hit the ground and roll off to one side so as not to obstruct the tailcone slide when it inflates.
The "screwdriver" tailcone did not roll away as easily,and that may be the reason for the MD-90 having the mentioned gas bottle to deflect the cone away from the A/C:
"Luck and superstition wins all the time"!
 
meister808
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RE: DC9 Tail Cone Evacuation

Wed Jul 28, 2004 2:07 pm

48 kg!!!

Damn that is light. I would have expected at least 500 lb.

-Meister
Twin Cessna 812 Victor, Minneapolis Center, we observe your operation in the immediate vicinity of extreme precipitation
 
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RE: DC9 Tail Cone Evacuation

Wed Jul 28, 2004 4:10 pm

That's right!
It should be able for just one person to handle it in case it doesn't clear the area by it's own after jettisoning.

Another interesting fact is that it remains in position due to air pressure/suction if the jettison handle is pulled during flight.It will fall off during landing,though.
"Luck and superstition wins all the time"!
 
DL_Mech
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RE: DC9 Tail Cone Evacuation

Wed Jul 28, 2004 9:18 pm

Another interesting fact is that it remains in position due to air pressure/suction if the jettison handle is pulled during flight.

I'll let you pull the handle............ Smile/happy/getting dizzy
This plane is built to withstand anything... except a bad pilot.
 
MD-90
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RE: DC9 Tail Cone Evacuation

Thu Jul 29, 2004 3:42 pm

Due to the internal air pressure (at altitude, at least), I'll bet it would pop off like a cork from a champagne bottle.

It'd be interesting if someone tried a D.B. Cooper style escape from one and chose that method instead of trying to get out without having the rear airstairs beat them to death against the lower fuselage.


I would've guessed that the tailcone weighs about 100 pounds, so 48 kilos sounds about right.
 
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RE: DC9 Tail Cone Evacuation

Thu Jul 29, 2004 6:59 pm

Like a champagne bottle? Nope,the tailcone was not part of the pressurized area,the aft cabin door forms part of the aft pressure bulkhead.The cooling louvres on either side of the aft fuselage,just below the fin,creates a slight underpressure within the tailcone compartment and this keeps the cone in place even if the locking pins are pulled.It will fall off as the plane slows down after landing.
"Luck and superstition wins all the time"!
 
MD-90
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RE: DC9 Tail Cone Evacuation

Fri Jul 30, 2004 11:46 am

Interesting...

I guess you shouldn't open the door to get back there during flight anyway, since that would compromise the pressure vessel.
 
CanadianNorth
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RE: DC9 Tail Cone Evacuation

Mon Aug 02, 2004 2:13 pm

If they were designed to come off when you pull the handles and someone pulled the handle on the ground, and someone happened to be standing under it, wouldn't that hurt come morning?



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