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Grisee08
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Why No "Screwdriver" Tail On DC9-10 Thru 50

Wed Mar 02, 2016 12:43 am

Original DC9-81s were delivered with the old-style cone (I forget what they are called), as were DC9-82s and DC9-83s. As we all know, AA has retrofitted all of their Super 80s with "Screwdriver" Tailcones, and all DC9-87s, MD-88s, MD-90s, and MD-95s (717) were delivered with Screwdriver cones. So how come airlines, such as NW didn't retrofit their DC9-10 thru -50s with screwdriver tailcones? Or at least the -30/-40/-50s? I know AA made all of theirs in-house, so I figured NW could have done the same, or contracted with AA. Does anybody know?
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L-188
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RE: Why No "Screwdriver" Tail On DC9-10 Thru 50

Wed Mar 02, 2016 12:45 am

AFAIK the DC-9's never had a stc created for the mod.

And with the low gas prices of the era and the short trips that NW made I don't think it would have made a lot of difference.
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OzarkD9S
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RE: Why No "Screwdriver" Tail On DC9-10 Thru 50

Wed Mar 02, 2016 12:48 am

I always called it a "paddlebutt". Guess the aerodynamics of the 9's vs. the 80's/90's were such that it was cost prohibitive.
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Okie
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RE: Why No "Screwdriver" Tail On DC9-10 Thru 50

Wed Mar 02, 2016 1:06 am

Quoting Grisee08 (Thread starter):
As we all know, AA has retrofitted all of their Super 80s with "Screwdriver" Tailcones

Out of context but AA developed their own STC for the Screwdriver tail and manufactured them in house for a fraction of the cost.
There was a good NBC program on the Tulsa Mx facility years ago that mentioned said modification.
If you can manufacture in house for a fraction of the cost and install during routine inspection program then it makes the small efficiency gains worthwhile when you have a 300 MD80 fleet.

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strfyr51
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RE: Why No "Screwdriver" Tail On DC9-10 Thru 50

Wed Mar 02, 2016 1:33 am

The Screwdriver tip tail cone on the MD80 wasn't available on the DC9 series and would have been a retrofit,
And?? A retrofit the airline would have had to justify in terms of Return on investment vs cost and downtime.
If the numbers don't add up? the investment would be a stupid one. By 1985 the DC9-80 series was the only viable airplane that mod might have been a positive on the B767-300 had anyone decided to do it and on the DC10-30'
I personally believe the DC10-30's would benefit by being re-engined and in turn re-engnie the
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NWAROOSTER
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RE: Why No "Screwdriver" Tail On DC9-10 Thru 50

Wed Mar 02, 2016 2:45 am

The screwdriver as you call it when I was working at Northwest was called the Beaver Tail.   
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Aircellist
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RE: Why No "Screwdriver" Tail On DC9-10 Thru 50

Wed Mar 02, 2016 6:07 am

What were the benefits of the, er, beaver tail?
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nema
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RE: Why No "Screwdriver" Tail On DC9-10 Thru 50

Wed Mar 02, 2016 6:20 am

It would be interesting to know the cost of the screwdriver cone. I would guess that the refitting costs would be minimal as it appears a far simpler exercise that fitting winglets for example.
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32andBelow
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RE: Why No "Screwdriver" Tail On DC9-10 Thru 50

Wed Mar 02, 2016 6:38 am

Quoting Aircellist (Reply 6):

What were the benefits of the, er, beaver tail?

I'm sure it is more aero. Isn't it also on the MD-11 vs. DC-10?
 
UA735WL
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RE: Why No "Screwdriver" Tail On DC9-10 Thru 50

Wed Mar 02, 2016 6:40 am

IIRC there actually is a mod that adds the screwdriver tail on the DC-9- it's made by the same company that offers the Super 98 upgrade for the M88 that DL just installed. I don't remember the name of the company, but I remember finding it while browsing their website after reading a thread about the Super 98 mod. Does anyone remember which company it is?


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rikkus67
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RE: Why No "Screwdriver" Tail On DC9-10 Thru 50

Wed Mar 02, 2016 6:53 am

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Rage
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RE: Why No "Screwdriver" Tail On DC9-10 Thru 50

Wed Mar 02, 2016 7:15 am

I thought that I had read somewhere decades ago that the tail was an improvement on two separate factors:
1. Aerodynamics - The shape of the new tail cut down on drag.
2. Safety - I remember reading that if the cone were to detach on the ground, the shape proved much more efficient at falling away from the aft air stairs than the original cone and so the chances of blocking an exit path were drastically reduced.
 
Grisee08
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RE: Why No "Screwdriver" Tail On DC9-10 Thru 50

Wed Mar 02, 2016 4:27 pm

Is AA the only company that now builds these (for replacement for all airlines) or does Boeing still manufacture these to replace them?
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N1120A
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RE: Why No "Screwdriver" Tail On DC9-10 Thru 50

Wed Mar 02, 2016 5:46 pm

Quoting Grisee08 (Thread starter):
I know AA made all of theirs in-house, so I figured NW could have done the same, or contracted with AA. Does anybody know?

It would have likely been the latter, if they had done it.

Quoting L-188 (Reply 1):
And with the low gas prices of the era and the short trips that NW made I don't think it would have made a lot of difference.

NW/DL was flying DC9s in some rather high fuel environments.

Quoting Okie (Reply 3):
If you can manufacture in house for a fraction of the cost and install during routine inspection program then it makes the small efficiency gains worthwhile when you have a 300 MD80 fleet.

AA also made money insourcing installs for other airlines, G4 being a big one.

Quoting Grisee08 (Reply 12):

Is AA the only company that now builds these (for replacement for all airlines) or does Boeing still manufacture these to replace them?

Is AA even still making them? I
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Grisee08
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RE: Why No "Screwdriver" Tail On DC9-10 Thru 50

Wed Mar 02, 2016 6:54 pm

Quoting N1120A (Reply 13):
Is AA even still making them? I

Good Point! Didn't think of that. I figure if they need one now, they can just go pick one out of the desert. 
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Adipasquale
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RE: Why No "Screwdriver" Tail On DC9-10 Thru 50

Wed Mar 02, 2016 7:21 pm

Quoting N1120A (Reply 13):
NW/DL was flying DC9s in some rather high fuel environments.

But I would guess that by the time fuel prices went up to the point that it would make sense to install the mods based on fuel prices alone, the DC-9s themselves were so old that there wasn't really a sound economic reason to install them.
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KCMCIfan
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RE: Why No "Screwdriver" Tail On DC9-10 Thru 50

Wed Mar 02, 2016 9:01 pm

If I remember right the CNBC special from around 2006 on AA covered quite a few details about the "screwdriver". I don't remember the exact figures but they mention how much Boeing wanted for them and then remarked how much they were in house. It was quite a cost savings.

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